An Introduction to the Reproductive System

An Introduction to the Reproductive System
Learning Outcomes 28-1 List the basic structures of the human reproductive system, and summarize the functions of each. 28-2 Describe the structures of the male reproductive system and the roles played by the reproductive tract and accessory glands in producing spermatozoa; specify the composition of semen; and summarize the hormonal mechanisms that regulate male reproductive functions.

Learning Outcomes 28-3 Describe the structures of the female reproductive system and the ovarian roles in oogenesis; explain the complete ovarian and uterine cycles; outline the histology, anatomy, and functions of the vagina; and summarize all aspects of the female reproductive cycle. 28-4 Discuss the physiology of sexual intercourse in males and females.

Learning Outcomes 28-5 Describe the reproductive system changes that occur with aging. 28-6 Give examples of interactions between the reproductive system and each of the other organ systems.

Is the only system that is not essential to the life of the individual Does affect other systems The male and female reproductive organs Produce and store specialized reproductive cells that combine to form new individuals Reproductive organs Also secrete hormones that play major roles in the maintenance of normal sexual function

28-1 Structures of the Reproductive System
Reproductive Structures Gonads are organs that produce gametes and hormones Ducts receive and transport gametes Accessory glands secrete fluids into ducts Perineal structures collectively known as external genitalia

The Reproductive Tract Includes all chambers and passageways that connect ducts to the exterior of the body Male and Female Reproductive Systems Are functionally different Female produces one gamete per month Retains and nurtures zygote Male produces large quantities of gametes Produces 1/2 billion sperm per day

The Male Reproductive System Testes or male gonads Secrete male sex hormones (androgens) Produce male gametes (spermatozoa or sperm)

The Female Reproductive System Ovaries or female gonads Release one immature gamete (oocyte) per month Produce hormones Uterine tubes Carry oocytes to uterus – if sperm reaches oocyte, fertilization is initiated and oocyte matures into ovum Uterus Encloses and supports developing embryo Vagina Connects uterus with exterior

28-2 Male Reproductive Functions
Pathway of Spermatozoa Testis Epididymis Ductus deferens (vas deferens) Ejaculatory duct Urethra

Accessory Organs Secrete fluids into ejaculatory ducts and urethra Seminal glands (vesicles) Prostate gland Bulbourethral glands

External Genitalia Scrotum Encloses testes Penis Erectile organ Contains distal portion of urethra

Figure 28-1 The Male Reproductive System (Part 1 of 2).
Prostatic urethra Pubic symphysis Major Structures of the Male Reproductive System Urinary bladder Ejaculatory duct Ducts Membranous urethra Spongy urethra Ductus deferens Epididymis Gonad Testis Corpus cavernosum External Genitalia Penis Corpus spongiosum Scrotum External urethral orifice

Figure 28-1 The Male Reproductive System (Part 2 of 2).
Ureter Rectum Accessory Glands Seminal gland Prostate gland Bulbourethral gland Anus

The Testes Egg shaped 5 cm long, 3 cm wide, 2.5 cm thick (2 in. × 1.2 in. × 1 in.) Each weighs 10–15 g (0.35–0.53 oz) Hang in scrotum

The Scrotum Is a fleshy pouch Suspended inferior to perineum Anterior to anus Posterior to base of penis

Descent of the Testes Testes form inside body cavity adjacent to kidneys Gubernaculum testis Is a bundle of connective tissue fibers Extends from testis to pockets of peritoneum Locks testes in position (near anterior abdominal wall) as fetus grows

Descent of the Testes During seventh month Fetus grows rapidly Circulating hormones Stimulate contraction of gubernaculum testis Each testis: Moves through abdominal musculature Is accompanied by pockets of peritoneal cavity

Figure 28-2a The Descent of the Testes.
Peritoneum Testis Gubernaculum testis 5 mm Colon 2 months Umbilical cord Penis 5 mm 3 months Pubis Testis 5 mm Scrotum Birth a Sagittal sectional views of the positional changes involved in the descent of the right testis. Because the size of the gubernaculum testis remains constant (see the scale bar at the right) while the rest of the fetus grows, the relative position of the testis shifts.

Figure 28-2b The Descent of the Testes (Part 1 of 2).
Diaphragmatic ligament Developing kidneys Mesonephric duct Gonads Gubernaculum testis 2 months Kidney Diaphragmatic ligament Epididymis Testis 3 months Epididymis Testis Urinary bladder b 4 months b Frontal views showing the descent of the testes and the formation of the spermatic cords. b

Figure 28-2b The Descent of the Testes (Part 2 of 2).
Ureter Testicular artery and vein Vas deferens Superficial inguinal ring Epididymis Scrotal cavity (opened) lined by tunica vaginalis Testis Gubernaculum testis 7 months Ureter Testicular artery and vein Urinary bladder Spermatic cord Scrotum (opened) Birth b Frontal views showing the descent of the testes and the formation of the spermatic cords.

Accessory Structures Accompany testis during descent Form body of spermatic cord Ductus deferens Testicular blood vessels, nerves, and lymphatic vessels

The Spermatic Cords Extend between abdominopelvic cavity and testes Consist of layers of fascia and muscle Enclose ductus deferens, blood vessels, nerves, and lymphatic vessels of testes Pass through inguinal canal Are passageways through abdominal musculature Form during development as testes descend into scrotum Descend into scrotum

Blood Vessels of Testes Deferential artery Testicular artery Pampiniform plexus of testicular vein Nerves of Testes Branches of genitofemoral nerve From lumbar plexus

Male Inguinal Hernias Are protrusions of visceral tissues into inguinal canal Spermatic cord (in closed inguinal canal) Causes weak point in abdominal wall Female Inguinal Canals Are very small Contain ilioinguinal nerves and round ligaments of uterus

Testis (covered by visceral layer of tunica vaginalis)
Figure 28-3 The Male Reproductive System in Anterior View (Part 1 of 2). Urinary bladder Inguinal canal Spermatic Cord Genitofemoral nerve Deferential artery Ductus deferens Pampiniform plexus Testicular artery Epididymis Scrotal cavity Testis (covered by visceral layer of tunica vaginalis) Parietal layer of tunica vaginalis (inner lining of cremaster, facing scrotal cavity) Raphe

Testicular artery Testicular vein Penis Inguinal ligament Superficial
Figure 28-3 The Male Reproductive System in Anterior View (Part 2 of 2). Testicular artery Testicular vein Penis Inguinal ligament Superficial inguinal ring Spermatic cord Scrotal septum Cremaster muscle with cremasteric fascia Layers of the Scrotum Superficial scrotal fascia Dartos muscle Scrotal skin (cut)

The Scrotum and the Position of the Testes Is divided into two chambers, or scrotal cavities Each testis lies in a separate scrotal chamber Raphe Is a raised thickening in scrotal surface Marks partition of two scrotal chambers

Tunica Vaginalis Is a serous membrane Lines scrotal cavity Reduces friction between opposing surfaces Parietal (scrotal) Visceral (testicular)

The Dartos Muscle Is a layer of smooth muscle in dermis of scrotum Causes characteristic wrinkling of scrotal surface The Cremaster Muscle Is a layer of skeletal muscle deep to dermis Tenses scrotum and pulls testes closer to body (temperature regulation)

Temperature Regulation Normal sperm development in testes Requires temperatures 1.1C (2F) lower than body temperature Muscles relax or contract To move testes away or toward body To maintain acceptable testicular temperatures

Structure of the Testes Tunica Albuginea Is deep to tunica vaginalis A dense layer of connective tissue rich in collagen fibers Continuous with fibers surrounding epididymis Fibers extend into substance of testis and form fibrous partitions, or septa, that converge near entrance to epididymis Supports blood and lymphatic vessels of testis and efferent ductules

Histology of the Testes Septa subdivide testis into lobules Lobules contain about 800 slender and tightly coiled seminiferous tubules Produce sperm Each is about 80 cm (32 in.) long Testis contains about 1/2 mile of tightly coiled seminiferous tubules Form a loop connected to rete testis, a network of passageways

Efferent Ductules 15–20 large efferent ductules Connect rete testis to epididymis

Figure 28-4a The Structure of the Testes.
Ductus deferens Epididymis Mediastinum of testis Efferent ductule Rete testis Scrotum Skin Dartos muscle Straight tubule Superficial scrotal fascia Seminiferous tubules Cremaster muscle Tunica vaginalis Tunica albuginea Septa Scrotal cavity Septa Lobule Raphe A transverse section of the scrotum and testes a

Figure 28-4b The Structure of the Testes.
Ductus deferens Epididymis Mediastinum of testis Efferent ductule Rete testis Scrotum Skin Dartos muscle Straight tubule Superficial scrotal fascia Cremaster muscle Seminiferous tubules Tunica vaginalis Tunica albuginea Septa Scrotal cavity Septa Lobule Raphe Testis LM × 26 b A section through a testis

Connective Tissue Capsules Surround tubules Areolar tissue fills spaces between tubules Within those spaces, there are: Blood vessels Large interstitial cells (Leydig cells) Produce androgens, dominant male sex hormones Testosterone is the most important androgen

Spermatogenesis Is the process of sperm production Begins at outermost cell layer in seminiferous tubules Proceeds toward lumen

Cells of Spermatogenesis Spermatogonia (stem cells) divide by mitosis to produce two daughter cells One remains as spermatogonium Second differentiates into primary spermatocyte Primary spermatocytes begin meiosis and form secondary spermatocytes

Cells of Spermatogenesis Secondary spermatocytes differentiate into spermatids (immature gametes) Spermatids Differentiate into spermatozoa Spermatozoa Lose contact with wall of seminiferous tubule Enter fluid in lumen

Figure 28-5a The Seminiferous Tubules.
containing late spermatids Seminiferous tubule containing spermatozoa Seminiferous tubule containing early spermatids Seminiferous tubules LM × 75 a A section through one or more seminiferous tubules.

Figure 28-5b The Seminiferous Tubules.
Dividing spermatocytes Nurse cell Interstitial cells Spermatogonium Spermatids Lumen Heads of maturing spermatozoa Seminiferous tubule LM × 350 b A cross section through a single tubule.

Figure 28-5c The Seminiferous Tubules.
Spermatid Nurse cell Dividing spermatocytes Capillary Lumen Interstitial cells Spermatogonium Spermatozoa c c Nurse cells surround the stem cells of the tubule and support the developing spermatocytes and spermatids.

Figure 28-5d The Seminiferous Tubules.
Spermatids completing spermiogenesis LUMEN Spermatids beginning spermiogenesis Initial spermiogenesis Secondary spermatocyte Secondary spermatocyte in meiosis II Primary spermatocyte preparing for meiosis I Luminal compartment Blood–testis barrier Nuclei of nurse cells Fibroblast Connective tissue capsule Capillary Interstitial cells Spermatogonium Basal compartment d Stages in spermatogenesis in the wall of a seminiferous tubule. d

Contents of Seminiferous Tubules Spermatogonia Spermatocytes at various stages of meiosis Spermatids Spermatozoa Large nurse cells (also called sustentacular cells or Sertoli cells) Are attached to tubular capsule Extend to lumen between other types of cells

Spermatogenesis Involves three integrated processes Mitosis Meiosis Spermiogenesis

Mitosis Is part of somatic cell division Produces two diploid (2n) daughter cells Both have identical pairs of chromosomes

Figure 28-6a Chromosomes in Mitosis and Meiosis.
Mitosis. The fates of three representative chromosome pairs during mitosis Cell (2n) Chromosomes Chromosome duplication 1 2 Chromosomes of daughter cell 1 Chromosomes of daughter cell 2 Daughter cells (2n)

Meiosis Is a special form of cell division involved only in production of gametes Spermatozoa in males Oocytes in females Gametes contain 23 chromosomes, half the normal amount Fusion of male and female gametes produces zygote with 46 chromosomes In seminiferous tubules: Begins with primary spermatocytes Produces spermatids (undifferentiated male gametes)

Spermiogenesis Begins with spermatids Small, relatively unspecialized cells Involves major structural changes Spermatids differentiate into mature spermatozoa Highly specialized cells

Mitosis and Meiosis Meiosis I and meiosis II Produce four haploid cells, each with 23 chromosomes (n)

Mitosis and Meiosis Prophase I Chromosomes condense Each chromosome has two chromatids Synapsis Maternal and paternal chromosomes come together Four matched chromatids form tetrad Crossing over: exchange of genetic material that increases genetic variation among offspring

Mitosis and Meiosis Metaphase I Tetrads line up along metaphase plate Independent assortment As each tetrad splits: Maternal and paternal components are randomly distributed

Mitosis and Meiosis Anaphase I Maternal and paternal chromosomes separate Each daughter cell receives whole chromosome Maternal or paternal

Mitosis and Meiosis Telophase I ends With formation of two daughter cells With unique combinations of chromosomes Both cells contain 23 chromosomes with two chromatids each (reductional division)

Mitosis and Meiosis Interphase Separates meiosis I and meiosis II Is very brief DNA is not replicated

Mitosis and Meiosis Meiosis II Proceeds through prophase II and metaphase II Anaphase II Duplicate chromatids separate Telophase II Yields four cells, each containing 23 chromosomes (equational division)

Figure 28-6a Chromosomes in Mitosis and Meiosis.
Mitosis. The fates of three representative chromosome pairs during mitosis Cell (2n) Chromosomes Chromosome duplication 1 2 Chromosomes of daughter cell 1 Chromosomes of daughter cell 2 Daughter cells (2n)

Figure 28-6b Chromosomes in Mitosis and Meiosis.
Meiosis. The fates of three representative chromosome pairs during the two stages of meiosis Cell (2n) Chromosomes Tetrad Chromosome duplication, synapsis, and tetrad formation Meiosis I Meiosis II 1 2 3 4 1 2 3 4 Chromosomes of gametes Gametes (n)

Figure 28-7 Spermatogenesis (Part 1 of 4).
Mitosis of spermatogonium Each division of a diploid spermatogonium produces two daughter cells. One is a spermatogonium that remains in contact with the basement membrane of the tubule, and the other is a primary spermatocyte that is displaced toward the lumen. These events from spermatogonium to primary spermatocyte take 16 days. Primary spermatocyte (diploid, 2n)

Meiosis I DNA replication As meiosis I begins, each primary spermatocyte contains 46 individual chromosomes. At the end of meiosis I, the daughter cells are called secondary spermatocytes. Every secondary spermatocyte contains 23 chromosomes, each with a pair of duplicate chromatids. This phase of spermatogenesis takes about 24 days. Primary spermatocyte Synapsis and tetrad formation Secondary spermatocytes

Meiosis II Spermatids (haploid, n) The secondary spermatocytes soon enter meiosis II, which yields four haploid spermatids, each containing 23 chromosomes. For each primary spermatocyte that enters meiosis, four spermatids are produced. This phase lasts only a few hours.

Spermiogenesis (physical maturation) In spermiogenesis, the last step of spermatogenesis, each spermatid matures into a single spermatozoon, or sperm. The process of spermiogenesis—from spermatids to spermatozoa—takes 24 days. Spermatozoa (haploid, n)

Spermiogenesis Is the last step of spermatogenesis Each spermatid matures into one spermatozoon (sperm) Attached to cytoplasm of nurse cells

Spermiation At spermiation, a spermatozoon: Loses attachment to nurse cell Enters lumen of seminiferous tubule Spermatogonial division to spermiation Takes about nine weeks

Nurse Cells Affect: Mitosis Meiosis Spermiogenesis in seminiferous tubules

Six Major Functions of Nurse Cells Maintain blood–testis barrier Support mitosis and meiosis Support spermiogenesis Secrete inhibin Secrete androgen-binding protein (ABP) Secrete Müllerian-inhibiting factor (MIF)

Maintenance of Blood–Testis Barrier Blood–testis barrier isolates seminiferous tubules Nurse cells are joined by tight junctions that divide seminiferous tubule into compartments Outer basal compartment contains spermatogonia Inner luminal compartment is where meiosis and spermiogenesis occur

Support of Mitosis and Meiosis Nurse cells are stimulated by: Follicle-stimulating hormone (FSH) Testosterone Stimulated nurse cells promote: Division of spermatogonia Meiotic divisions of spermatocytes

Support of Spermiogenesis Nurse cells Surround and enfold spermatids Provide nutrients and chemical stimuli for development Phagocytize cytoplasm shed by developing spermatids

Secretion of Inhibin Inhibin Is a peptide hormone secreted by nurse cells in response to factors released by spermatozoa Depresses: Pituitary production of FSH Hypothalamic secretion of GnRH Regulation of FSH and GnRH by inhibin: Gives nurse cells feedback control of spermatogenesis After division, increases inhibin production

Secretion of Androgen-Binding Protein (ABP) Androgen-Binding Protein (ABP) Binds androgens (primarily testosterone) In seminiferous tubule fluid Is important in: Elevating androgen in seminiferous tubules Stimulating spermiogenesis Production of ABP is stimulated by FSH

Secretion of Müllerian-Inhibiting Factor (MIF) Müllerian-Inhibiting Factor (MIF) Is secreted by nurse cells in developing testes Causes regression of fetal Müllerian (paramesonephric) ducts Help form uterine tubes and uterus in females In males, inadequate MIF production leads to: Retention of ducts Failure of testes to descend into scrotum

The Anatomy of a Spermatozoon Head Neck (attaches head to middle piece) Middle piece Tail

The Anatomy of a Spermatozoon Head A flattened ellipse that contains nucleus and chromosomes Acrosome A cap-like compartment at tip of head A membranous compartment that contains enzymes essential to fertilization Made of fused saccules of spermatid’s Golgi apparatus

The Anatomy of a Spermatozoon Middle piece Attached to head by short neck Contains mitochondria In spiral around microtubules Activity provides ATP to move tail

The Anatomy of a Spermatozoon Tail Is the only flagellum in the human body Is a whiplike organelle Moves cell from one place to another Has complex, corkscrew motion

Figure 28-8 Spermiogenesis and Spermatozoon Structure (Part 1 of 2).
Spermatid Mitochondria Nucleus Shed cytoplasm Golgi apparatus Acrosomal vesicle Acrosome Nucleus Acrosome Spermiogenesis. The differentiation of a spermatid into a spermatozoon. This process is completed in approximately 24 days.

Figure 28-8 Spermiogenesis and Spermatozoon Structure (Part 2 of 2).
Tail (55 m) Fibrous sheath of flagellum Middle piece (5 m) Spermatozoa SEM × 780 Mitochondrial spiral Neck (1 m) Centrioles Nucleus Head (5 m) Acrosome Spermatozoon

Mature Spermatozoon Lacks: Endoplasmic reticulum Golgi apparatus Lysosomes and peroxisomes Inclusions and other intracellular structures Loss of these organelles reduces sperm size and mass Sperm must absorb nutrients (fructose) from surrounding fluid

The Male Reproductive Tract Sperm maturation Testes produce physically mature spermatozoa that CANNOT fertilize an oocyte Other parts of reproductive system are responsible for: Functional maturation, nourishment, storage, and transport

The Male Reproductive Tract Sperm maturation Spermatozoa Detach from nurse cells Are free in lumen of seminiferous tubule Are functionally immature Are incapable of locomotion or fertilization Are moved by cilia lining efferent ductules into the epididymis

The Epididymis Is the start of male reproductive tract Is a coiled tube almost 7 m (23 ft) long Bound to posterior border of testis Has a head, a body, and a tail

Epididymis Head Is proximal to the testis Receives spermatozoa from efferent ductules Epididymis Body From last efferent ductule to posterior margin of testis Epididymis Tail Begins near inferior border of testis where number of coils decreases Re-curves and ascends to connection with ductus deferens Primary storage location of spermatozoa

Figure 28-9a The Epididymis.
Spermatic cord Ductus deferens Efferent ductules Straight tubule Rete testis Seminiferous tubule Epididymis Head of epididymis Tunica albuginea Body of epididymis Testis Tail of epididymis Scrotal cavity a A diagrammatic view of the head, body, and tail of an epididymis

Figure 28-9b The Epididymis.
Flagella of spermatozoa in lumen of epididymis Pseudostratified columnar epithelium of epididymis Stereocilia Epididymis LM × 304 b Sectional view of the epididymis

Figure 28-9c The Epididymis.
Tunica vaginalis (reflected) Spermatic cord Ductus deferens Epididymis Head of epididymis Body of epididymis Testis Tail of epididymis c Appearance of the testis and epididymis on gross dissection

Three Functions of the Epididymis Monitors and adjusts fluid produced by seminiferous tubules Recycles damaged spermatozoa Stores and protects spermatozoa Facilitates functional maturation

Spermatozoa Leaving Epididymis Are mature, but remain immobile To become motile (actively swimming) and functional: Spermatozoa undergo capacitation

Two Steps in Capacitation Spermatozoa become motile When mixed with secretions of seminal glands Spermatozoa become capable of fertilization When exposed to female reproductive tract

The Ductus Deferens (Vas Deferens) Is 40–45 cm (16–18 in.) long Begins at tail of the epididymis and, as part of spermatic cord, ascends through inguinal canal Curves inferiorly along urinary bladder Toward prostate gland and seminal glands Lumen enlarges into ampulla Wall contains thick layer of smooth muscle

The Ductus Deferens Is lined by ciliated epithelium Peristaltic contractions propel spermatozoa and fluid Can store spermatozoa for several months In state of suspended animation (low metabolic rates)

Figure 28-10a The Ductus Deferens and Accessory Glands.
Ureter Urinary bladder Ductus deferens Seminal gland Ampulla of ductus deferens Duct of seminal gland Ejaculatory duct Prostate gland Prostatic urethra a A posterior view of the urinary bladder and prostate gland, showing subdivisions of the ductus deferens in relation to surrounding structures. Bulbourethral glands Urogenital diaphragm

Figure 28-10b The Ductus Deferens and Accessory Glands.
Lumen of ductus deferens Smooth muscle Ductus deferens LM×120 b Light micrograph showing the thick layers of smooth muscle in the wall of the ductus deferens.

The Ejaculatory Duct Is a short passageway (2 cm; less than 1 in.) At junction of ampulla and seminal gland duct Penetrates wall of prostate gland Empties into urethra

The Urethra Is used by urinary and reproductive systems Extends 18–20 cm (7–8 in.) from urinary bladder to tip of penis Is divided into three regions Prostatic Membranous Spongy

The Accessory Glands Produce semen, which is a mixture of secretions from many glands Each with distinctive biochemical characteristics Important glands include: Seminal glands Prostate gland Bulbourethral glands

Four Major Functions of Male Glands Activating spermatozoa Providing nutrients spermatozoa need for motility Propelling spermatozoa and fluids along reproductive tract Mainly by peristaltic contractions Producing buffers To counteract acidity of urethral and vaginal environments

The Seminal Glands (Seminal Vesicles) Each gland is about 15 cm (6 in.) long with short side branches from body Are tubular glands coiled and folded into 5 cm by 2.5 cm (2 in. × 1 in.) mass Are extremely active secretory glands Produce about 60 percent of semen volume

Seminal Fluid Has same osmotic concentration as blood plasma but different composition High concentrations of fructose easily metabolized by spermatozoa Prostaglandins stimulate smooth muscle contractions (male and female) Fibrinogen forms temporary clot in vagina Is slightly alkaline To neutralize acids in prostate gland and vagina

Seminal Fluid Initiates first step in capacitation Spermatozoa begin beating flagella, become highly motile Is discharged into ejaculatory duct at emission When peristaltic contractions are under way Contractions are controlled by sympathetic nervous system

Figure 28-10c The Ductus Deferens and Accessory Glands.
Lumen Secretory pockets Smooth muscle Seminal gland LM×45 c Histology of the seminal glands. These organs produce most of the volume of seminal fluid.

The Prostate Gland Is a small, muscular organ, about 4 cm (1.6 in.) in diameter Encircles proximal portion of urethra Below urinary bladder Consists of 30–50 compound tubuloalveolar glands Surrounded by smooth muscle fibers

Prostatic Fluid Is slightly acidic Forms 20–30 percent of semen volume Contains antibiotic seminalplasmin Is ejected into prostatic urethra By peristalsis of prostate wall

Figure 28-10d The Ductus Deferens and Accessory Glands.
Connective tissue and smooth muscle Prostatic (tubuloalveolar) glands Prostate gland LM×50 d Histological detail of the glands of the prostate. The tissue between the individual glandular units consists largely of smooth muscle. Contractions of this muscle tissue help move the secretions into the ejaculatory duct and urethra.

The Bulbourethral Glands (Cowper’s Glands) Are compound, tubular mucous glands Round shaped, up to 10 mm (less than 0.5 in.) diameter Located at base of penis Covered by fascia of urogenital diaphragm

The Bulbourethral Glands (Cowper’s Glands) Secrete thick, alkaline mucus Helps neutralize urinary acids in urethra Lubricates the glans (penis tip) Duct of each gland travels alongside penile urethra and empties into urethral lumen

Figure 28-10e The Ductus Deferens and Accessory Glands.
Smooth muscle Capsule Mucous glands Lumen Bulbourethral gland LM×175 e Histology of the bulbourethral glands, which secrete a thick mucus into the spongy urethra.

Semen Typical ejaculation releases 2–5 mL Abnormally low volume may indicate problems With prostate gland or seminal glands Sperm count Is taken of semen collected after 36 hours of sexual abstinence Normal range 20–100 million spermatozoa/mL of ejaculate

Ejaculate Is the volume of fluid produced by ejaculation Contains: Spermatozoa Seminal fluid Enzymes Including protease, seminalplasmin, prostatic enzyme, and fibrinolysin

Male External Genitalia The penis Is a tubular organ through which distal portion of urethra passes Conducts urine to exterior Introduces semen into female’s vagina

The Penis The root Is the fixed portion that attaches penis to body wall Attachment occurs within urogenital triangle, inferior to pubic symphysis The body (shaft) Is the tubular, movable portion of the penis Consists of three cylindrical columns of erectile tissue The glans Is the expanded distal end of penis that surrounds external urethral orifice

A frontal section through the penis and associated organs
Figure 28-11a The Penis. Ureter Trigone of urinary bladder Seminal gland Ductus deferens Prostate gland Opening of ejaculatory duct Prostatic urethra Membranous urethra Bulbourethral gland Urogenital diaphragm Crus at root of penis Bulb of penis Opening from bulbourethral gland Erectile Tissue Corpus spongiosum Corpora cavernosa Spongy urethra Glans penis Prepuce External urethral orifice a a A frontal section through the penis and associated organs

A sectional view through the penis
Figure 28-11b The Penis. Dorsal artery (red), veins (blue), and nerve (yellow) Corpora cavernosa Dartos muscle Deep artery of penis Collagenous sheath Spongy urethra Corpus spongiosum b A sectional view through the penis

Figure 28-11c The Penis. Pubic symphysis Membranous urethra Bulb of penis Right crus of penis Body (shaft) of penis Ischial ramus Corpus spongiosum Neck of penis Corpora cavernosa Glans penis External urethral orifice Scrotum c An anterior and lateral view of the penis, showing positions of the erectile tissues

Dermis of the Penis Contains a layer of smooth muscle A continuation of dartos muscle Underlying areolar tissue Allows skin to move freely Subcutaneous layer Contains superficial arteries, veins, and lymphatic vessels

The Prepuce (Foreskin) Is a fold of skin surrounding tip of penis Attaches to neck and continues over glans Preputial glands In skin of neck and inner surface of prepuce Secrete waxy material (smegma) that can support bacteria Circumcision can help prevent infection

Erectile Tissue In body of penis Located deep to areolar tissue In dense network of elastic fibers That encircles internal structures of penis Consists of network of vascular channels Incompletely separated by partitions of elastic connective tissue and smooth muscle fibers In resting state: Arterial branches are constricted Muscular partitions are tense Blood flow into erectile tissue is restricted

The Corpora Cavernosa Two cylindrical masses of erectile tissue Under anterior surface of flaccid penis Separated by thin septum Encircled by dense collagenous sheath Diverge at their bases, forming the crura of penis Each crus is bound to ramus of ischium and pubis By tough connective tissue ligaments Extend to neck of penis Erectile tissue surrounds a central artery

The Corpus Spongiosum Relatively slender erectile body that surrounds penile urethra Extends from urogenital diaphragm to tip of penis and expands to form the glans Is surrounded by a sheath With more elastic fibers than corpora cavernosa Erectile tissue contains a pair of small arteries

Hormones and Male Reproductive Function Anterior lobe of the pituitary gland releases: Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) In response to: Gonadotropin-releasing hormone (GnRH)

Gonadotropin-Releasing Hormone Is synthesized in hypothalamus Carried to pituitary by hypophyseal portal system Is secreted in pulses At 60–90 minute intervals Controls rates of secretion of: FSH and LH Testosterone (released in response to LH)

FSH and Testosterone Target nurse cells of seminiferous tubules Nurse cells Promote spermatogenesis and spermiogenesis Secrete androgen-binding protein (ABP)

Negative Feedback Spermatogenesis is regulated by: GnRH, FSH, and inhibin As spermatogenesis accelerates: Inhibin secretion increases

Inhibin Inhibits FSH production In anterior lobe of the pituitary gland Suppresses secretion of GnRH At hypothalamus

Inhibin and FSH Elevated FSH levels Increase inhibin production Until FSH returns to normal If FSH declines: Inhibin production falls FSH production increases

Luteinizing Hormone Targets interstitial cells of testes Induces secretion of: Testosterone Other androgens

Testosterone Is the most important androgen Stimulates spermatogenesis Promoting functional maturation of spermatozoa Affects CNS function Libido (sexual drive) and related behaviors Stimulates metabolism Especially protein synthesis Blood cell formation Muscle growth

Testosterone Establishes male secondary sex characteristics Distribution of facial hair Increased muscle mass and body size Characteristic adipose tissue deposits Maintains accessory glands and organs of male reproductive tract

Figure 28-12 Regulation of Male Reproduction (Part 1 of 2).
Male reproductive function is regulated by the complex interaction of hormones from the hypothalamus, anterior lobe of the pituitary gland, and the testes. Negative feedback systems keep testosterone levels within a relatively narrow range until late in life. HYPOTHALAMUS Release of Gonadotropin- Releasing Hormone (GnRH) Negative feedback ? High testosterone levels inhibit the release of GnRH by the hypothalamus, causing a decrease in LH secretion, which lowers testosterone to normal levels. The hypothalamus secretes the hormone GnRH at a rate that remains relatively steady. As a result, blood levels of FSH, LH, and testosterone remain within a relatively narrow range throughout a man’s reproductive life. When stimulated by GnRH, the anterior lobe of the pituitary gland releases luteinizing hormone (LH) and follicle-stimulating hormone (FSH). ANTERIOR LOBE OF THE PITUITARY GLAND Secretion of Follicle- Stimulating Hormone (FSH) Secretion of Luteinizing Hormone (LH) Inhibin depresses the pituitary production of FSH, and perhaps the hypothalamic secretion of gonadotropin-releasing hormone (GnRH).The faster the rate of sperm production, the more inhibin is secreted. By regulating FSH and GnRH secretion, nurse cells provide feedback control of spermatogenesis. FSH targets primarily the nurse cells of the seminiferous tubules. LH targets the interstitial cells of the testes. KEY Stimulation Inhibition

Figure 28-12 Regulation of Male Reproduction (Part 2 of 2).
Interstitial Cell Stimulation Negative feedback LH induces the secretion of testosterone and other androgens by the interstitial cells of the testes. TESTES Nurse Cell Stimulation Testosterone Under FSH stimulation, and with testosterone from the interstitial cells, nurse cells (1) secrete inhibin in response to factors released by developing spermatozoa, (2) secrete androgen-binding protein (ABP), and (3) promote spermatogenesis and spermiogenesis. Inhibin KEY Stimulation Inhibition Androgen-binding protein (ABP) binds androgens within the seminiferous tubules, which increases the local concentration of androgens and stimulates the physical maturation of spermatids. Nurse cell environment facilitates both spermatogenesis and spermiogenesis. Peripheral Effects of Testosterone Maintains libido (sexual drive) and related behaviors Stimulates bone and muscle growth Establishes and maintains male secondary sex characteristics Maintains accessory glands and organs of the male reproductive system

Testosterone Functions like other steroid hormones Diffuses across target cell membrane Binds to intracellular receptor Hormone–receptor complex Binds to DNA in nucleus Circulating in bloodstream Bound to one of two types of transport proteins Gonadal steroid-binding globulin (GBG) carries 2/3 of circulating testosterone Albumins carry 1/3 of testosterone

Testosterone and Development Production begins around seventh week of fetal development and reaches prenatal peak after six months Secretion of Müllerian-inhibiting factor by nurse cells leads to regression of Müllerian ducts Early surge in testosterone levels stimulates differentiation of male duct system and accessory organs and affects CNS development

Testosterone and Development Testosterone programs hypothalamic centers that control: GnRH, FSH, and LH secretion Sexual behaviors Sexual drive

Estradiol Is produced in relatively small amounts (2 ng/dL) 70 percent is converted from circulating testosterone By enzyme aromatase 30 percent is secreted by interstitial and nurse cells of testes

28-3 The Female Reproductive System
Produces sex hormones and functional gametes Protects and supports developing embryo Nourishes newborn infant

Organs of the Female Reproductive System Ovaries Uterine tubes Uterus Vagina External genitalia

Figure 28-13 The Female Reproductive System (Part 1 of 2).
Ovarian follicle Rectouterine pouch Vesicouterine pouch Urinary bladder Urethra Pubic symphysis Accessory Glands Paraurethral glands Greater vestibular gland Clitoris

Figure 28-13 The Female Reproductive System (Part 2 of 2).
Sigmoid colon Rectum Anus Major Structures of the Female Reproductive System Ovary Uterine tube Uterus Vagina External Genitalia Perimetrium Myometrium Endometrium Cervix Labium minus Labium majus

Structural Support Ovaries, uterine tubes, and uterus are enclosed in broad ligament Uterine tubes Run along broad ligament Open into pelvic cavity lateral to ovaries The mesovarium Stabilizes position of each ovary

A posterior view of the uterus, uterine tubes, and ovaries
Figure 28-14a The Ovaries and Their Relationships to the Uterine Tube and Uterus (Part 1 of 2). Ovarian artery and vein Fimbriae Uterine tube Suspensory ligament Uterus Infundibulum Ovary Ureter Uterosacral ligament External os Cervix Vaginal rugae Vaginal wall a A posterior view of the uterus, uterine tubes, and ovaries

A posterior view of the uterus, uterine tubes, and ovaries
Figure 28-14a The Ovaries and Their Relationships to the Uterine Tube and Uterus (Part 2 of 2). Structures Stabilizing the Ovary Ovarian ligament Mesovarium Suspensory ligament Retractor Uterus Broad ligament a A posterior view of the uterus, uterine tubes, and ovaries

Figure 28-14b The Ovaries and Their Relationships to the Uterine Tube and Uterus.
Corpus luteum Cortex Tunica albuginea Mesenteries of the Ovary and Uterine Tube Mesosalpinx Mesovarium Broad ligament Ovarian hilum Egg nest Germinal epithelium Mature follicle b A sectional view of the ovary, uterine tube, and associated mesenteries

Ovaries Are small, almond-shaped organs near lateral walls of pelvic cavity Three main functions Production of immature female gametes (oocytes) Secretion of female sex hormones (estrogens, progestins) Secretion of inhibin, involved in feedback control of pituitary FSH

Ovary Support Mesovarium Ovarian ligament extends from uterus to ovary Suspensory ligament extends from ovary to pelvic wall Contains the ovarian artery and ovarian vein These vessels connect to ovary at ovarian hilum, where ovary attaches to mesovarium

The Visceral Peritoneum of the Ovary Also called germinal epithelium Covers surface of ovary Consists of columnar epithelial cells Overlies tunica albuginea

The Stroma Are interior tissues of ovary Superficial cortex Deeper medulla Gametes are produced in cortex

Oogenesis Also called ovum production Begins before birth Accelerates at puberty Ends at menopause

Figure 28-15 Oogenesis (Part 1 of 3).
Mitosis of oogonium Oogonium (stem cell) Unlike spermatogonia, the oogonia (ō-ō-GŌ-nē-uh), or female reproductive stem cells, complete their mitotic divisions before birth. Oogonium Primary oocyte (diploid, 2n)

Meiosis I DNA replication Between the third and seventh months of fetal development, the daughter cells, or primary oocytes (Ō-ō-sīts), prepare to undergo meiosis. They proceed as far as the prophase of meiosis I, but then the process comes to a halt. Primary oocyte Tetrad First polar body The primary oocytes remain in a state of suspended development until puberty, when rising levels of FSH trigger the start of the ovarian cycle. Each month after the ovarian cycle begins, some of the primary oocytes are stimulated to undergo further development. Meiosis I is then completed, yielding a secondary oocyte and a polar body. Secondary oocyte First polar body may not complete meiosis II

Meiosis II Secondary oocyte released (ovulation) in metaphase of meiosis II Each month after the ovarian cycle begins, one or more secondary oocytes leave the ovary suspended in metaphase of meiosis II. At the time of fertilization, a second polar body forms and the fertilized oocyte is then called a mature ovum. (A cell in any of the preceding steps in oogenesis is sometimes called an immature ovum.) Second polar body Sperm (n) Nucleus of oocyte (n) Fertilization (see Figure 29–1)

Fetal Development Between third and seventh months: Primary oocytes prepare for meiosis Stop at prophase of meiosis I Atresia Is the degeneration of primordial follicles Ovaries have about 2 million primordial follicles at birth Each containing a primary oocyte By puberty: Number drops to about 400,000

Process of Oogenesis Primary oocytes remain in suspended development until puberty At puberty: Rising FSH triggers start of ovarian cycle Each month thereafter: Some primary oocytes are stimulated to develop further

Oogenesis: Two Characteristics of Meiosis Cytoplasm of primary oocyte divides unevenly Producing one ovum (with original cytoplasm) And two or three polar bodies (that disintegrate) Ovary releases secondary oocyte (not mature ovum) Suspended in metaphase of meiosis II Meiosis is completed upon fertilization

The Ovarian Cycle After sexual maturation A different group of primordial follicles is activated each month Is divided into: Follicular phase (preovulatory phase) Luteal phase (postovulatory phase)

The Ovarian Cycle Ovarian follicles Are specialized structures in cortex of ovaries Where oocyte growth and meiosis I occur Primary oocytes Are located in outer part of ovarian cortex Near tunica albuginea In clusters called egg nests

Primordial Follicle Each primary oocyte in an egg nest Is surrounded by follicle cells Primary oocyte and follicle cells form a primordial follicle

Figure 28-16 The Ovarian Cycle (Part 1 of 7).
Primordial follicles in egg nest Primary oocyte Follicle cells LM ×1440

Formation of primary follicle Granulosa cells Primary oocytes Zona pellucida Thecal cells LM ×1092

Formation of secondary follicle Thecal cells Zona pellucida Nucleus of primary oocyte Granulosa cells LM ×1052

Formation of tertiary follicle Antrum containing follicular fluid Granulosa cells Corona radiata Secondary oocyte LM ×136

Primordial follicles Primary follicle Secondary follicle Tertiary follicle Released secondary oocyte Corona radiata Corpus albicans Corpus luteum 5 Ovulation Follicular fluid Secondary oocyte within corona radiata Ruptured follicle wall Outer surface of ovary LM ×70

Formation of corpus luteum LM ×208

Formation of corpus albicans LM ×208

The Uterine Tubes Also called Fallopian tubes or oviducts Are hollow, muscular tubes about 13 cm (5.2 in.) long Transport oocyte from ovary to uterus

Three Segments of the Uterine Tubes Infundibulum An expanded funnel near ovary With fimbriae that extend into pelvic cavity Inner surfaces lined with cilia that beat toward middle segment Ampulla Middle segment Smooth muscle layers in wall become thicker approaching uterus Isthmus A short segment between ampulla and uterine wall

Figure 28-17a The Uterine Tubes.
Ampulla Isthmus Uterus Fimbriae Infundibulum a Regions of the uterine tubes, posterior view

Histology of the Uterine Tube Epithelium lining uterine tube Contains scattered mucin-secreting cells Mucosa is surrounded by concentric layers of smooth muscle

Figure 28-17b The Uterine Tubes.
Columnar epithelium Lamina propria Smooth muscle Isthmus LM ×122 b A sectional view of the isthmus

Figure 28-17c The Uterine Tubes.
Microvilli of mucin- secreting cells Cilia Epithelial surface SEM×4000 c A colorized SEM of the ciliated lining of the uterine tube

Uterine Tube and Oocyte Transport Involves ciliary movement and peristaltic contractions in walls of uterine tube A few hours before ovulation, nerves from hypogastric plexus: “Turn on” beating pattern Initiate peristalsis From infundibulum to uterine cavity Normally takes three to four days

Uterine Tube and Fertilization For fertilization to occur: Secondary oocyte must meet spermatozoa during first 12–24 hours Fertilization typically occurs: Near boundary between ampulla and isthmus Uterine tube provides nutrient-rich environment by secretions from peg cells Containing lipids and glycogen Nutrients supply spermatozoa and developing pre- embryo

The Uterus Provides for developing embryo (weeks 1–8) and fetus (week 9 through delivery) Mechanical protection Nutritional support Waste removal

The Uterus Is pear-shaped 7.5 cm long, 5 cm diameter (3 in. × 2 in.) Weighs 50–100 g (1.75–3.5 oz) Normally bends anteriorly near base (anteflexion) In retroflexion, uterus bends backward

Suspensory Ligaments of Uterus Uterosacral ligaments Prevent inferior–anterior movement Round ligaments Restrict posterior movement Cardinal (lateral) ligaments Prevent inferior movement

Uterine Body Is largest portion of uterus Ends at isthmus Fundus Is rounded portion of uterine body Superior to attachment of uterine tubes

Cervix Is inferior portion of uterus Extends from isthmus to vagina Distal end projects about 1.25 cm (0.5 in.) into vagina External os Also called external orifice of uterus Is surrounded by distal end of cervix Leads into cervical canal

Cervical Canal Is a constricted passageway opening to uterine cavity of body At internal os (internal orifice)

Blood Supply of the Uterus Branches of uterine arteries Arising from branches of internal iliac arteries Ovarian arteries Arising from abdominal aorta Veins and lymphatic vessels

Nerves of the Uterus Autonomic fibers from hypogastric plexus (sympathetic) Sacral segments S3 and S4 (parasympathetic) Segmental blocks Anesthetic procedure used during labor Target spinal nerves T10–L1

Figure 28-18a The Uterus (Part 1 of 2).
Uterine Tube Fimbriae Infundibulum Ampulla Isthmus Fundus of uterus Uterine cavity Perimetrium Myometrium Endometrium See Figure 28–19 Uterine artery and vein Internal os of uterus Isthmus of uterus Cervical canal Cervix Vaginal artery External os of uterus Vaginal rugae See Figure 28–21 Vagina a A posterior view with the left portion of the uterus, left uterine tube, and left ovary shown in section.

Figure 28-18a The Uterus (Part 2 of 2).
Suspensory ligament of ovary Fundus of uterus Uterine tube Ovarian artery and vein Mesovarium Body of uterus Ovary Ovarian ligament Uterine cavity Round ligament of uterus Broad ligament Cervix Vagina a A posterior view with the left portion of the uterus, left uterine tube, and left ovary shown in section.

A superior view of the ligaments that stabilize
Figure 28-18b The Uterus. Uterosacral ligament POSTERIOR Cardinal ligaments (under broad ligament) Sigmoid colon Suspensory ligament of ovary Ovary Broad ligament Ovarian ligament Uterus Uterine tube Round ligament of uterus Vesicouterine pouch Urinary bladder ANTERIOR b A superior view of the ligaments that stabilize the position of the uterus in the pelvic cavity.

it is covered by peritoneum.
Figure 28-18c The Uterus. POSTERIOR Rectouterine pouch Ovary Ovarian ligament Uterine tube Uterus Vesicouterine pouch ANTERIOR c Superior view of the female pelvic cavity showing supporting ligaments of uterus and ovaries. In the photo, the urinary bladder cannot be seen because it is covered by peritoneum.

The Uterine Wall Has a thick, outer, muscular myometrium Has a thin, inner, glandular endometrium (mucosa) The perimetrium Is an incomplete serous membrane Continuous with peritoneal lining Covers fundus and posterior surface of uterine body and isthmus

The Myometrium The thickest portion of the uterine wall Constitutes almost 90 percent of the mass of the uterus Arranged into longitudinal, circular, and oblique layers Provides force to move fetus out of uterus into vagina

The Endometrium Contributes about 10 percent of uterine mass Glandular and vascular tissues support physiological demands of growing fetus Uterine glands Open onto endometrial surface Extend deep into lamina propria Estrogen Causes uterine glands, blood vessels, and epithelium to change with phases of monthly uterine cycle

Figure 28-19a The Uterine Wall.
Perimetrium Straight artery Myometrium Endometrium Uterine glands Uterine cavity Spiral artery Arcuate arteries Radial artery Uterine artery a A diagrammatic sectional view of the uterine wall, showing the endometrial regions and the blood supply to the endometrium

Figure 28-19b The Uterine Wall.
Endometrium Simple columnar epithelium Uterine glands Functional zone Basilar zone Myometrium Uterine cavity Uterine wall LM×32 b The basic histological structure of the uterine wall

Two Divisions of Endometrium The functional zone Contains most of the uterine glands Contributes most of endometrial thickness Undergoes dramatic changes in thickness and structure during menstrual cycle The basilar zone Attaches endometrium to myometrium Contains terminal branches of tubular endometrial glands

Blood Supply of Endometrium Arcuate arteries Encircle endometrium Radial arteries Supply straight arteries (to basilar zone) Supply spiral arteries (to functional zone)

Cyclical Changes in Endometrium Basilar zone remains relatively constant Functional zone undergoes cyclical changes In response to sex hormone levels Produce characteristic features of uterine cycle

The Uterine Cycle (Menstrual Cycle) Is a repeating series of changes in endometrium Lasts from 21 to 35 days Average 28 days Responds to hormones of ovarian cycle Menses and proliferative phase Occur during ovarian follicular phase Secretory phase Occurs during ovarian luteal phase

Menses Is the degeneration of functional zone Occurs in patches Is caused by constriction of spiral arteries Reducing blood flow, oxygen, and nutrients Weakened arterial walls rupture Releasing blood into connective tissues of functional zone

Menses Degenerating tissues break away, enter uterine lumen Entire functional zone is lost Through external os and vagina Only functional zone is affected Deeper, basilar zone is supplied by straight arteries

The endometrium at menses
Figure 28-20a The Appearance of the Endometrium during the Uterine Cycle. Perimetrium Uterine glands Uterine cavity Endometrium Myometrium Basilar zone of endometrium Cervix MYOMETRIUM Menses LM ×63 a The endometrium at menses

Menstruation Is the process of endometrial sloughing Lasts one to seven days Sheds 35–50 mL (1.2–1.7 oz) blood

The Proliferative Phase Epithelial cells of uterine glands Multiply and spread across endometrial surface Restore integrity of uterine epithelium Further growth and vascularization Completely restores functional zone Occurs at same time as: Enlargement of primary and secondary follicles in ovary

The Proliferative Phase Is stimulated and sustained by: Estrogens secreted by developing ovarian follicles Entire functional zone is highly vascularized Small arteries Spiral toward inner surface From larger arteries in myometrium

The endometrium during the proliferative phase
Figure 28-20b The Appearance of the Endometrium during the Uterine Cycle. Uterine glands Uterine cavity Uterine cavity Functional zone Myometrium ENDOMETRIUM Basilar zone MYOMETRIUM Proliferative phase LM ×66 b The endometrium during the proliferative phase

The Secretory Phase Endometrial glands enlarge, increasing rate of secretion Arteries of uterine wall Elongate and spiral through functional zone Begins at ovulation and persists as long as corpus luteum remains intact Peaks about 12 days after ovulation Glandular activity declines Generally lasts 14 days Ends as corpus luteum stops producing stimulatory hormones

The endometrium during the secretory phase of the uterine cycle
Figure 28-20c The Appearance of the Endometrium during the Uterine Cycle. Uterine glands Uterine cavity Detail of uterine glands LM ×150 Functional zone Secretory phase LM ×52 c The endometrium during the secretory phase of the uterine cycle

Menarche The first uterine cycle Begins at puberty (age 11–12) Menopause The termination of uterine cycles Age 45–55

Amenorrhea Primary amenorrhea Failure to initiate menses Transient secondary amenorrhea Interruption of six months or more Caused by physical or emotional stresses

The Vagina Is an elastic, muscular tube Extends between cervix and vestibule 7.5–9 cm (3–3.6 in.) long Highly distensible

The Vagina Cervix projects into vaginal canal Fornix is shallow recess surrounding cervical protrusion Lies parallel to: Rectum, posteriorly Urethra, anteriorly

Blood Supply of the Vagina Is through vaginal branches of internal iliac (uterine) arteries and veins Innervation of the Vagina Hypogastric plexus Sacral nerves Branches of pudendal nerve

Three Functions of the Vagina Passageway for elimination of menstrual fluids Receives spermatozoa during sexual intercourse Forms inferior portion of birth canal

Anatomy and Histology of the Vagina The Vaginal Wall Contains a network of blood vessels and layers of smooth muscle Is moistened by: Secretions of cervical glands Water movement across permeable epithelium

The Hymen Is an elastic epithelial fold That partially blocks entrance to vagina Usually ruptured by sexual intercourse or tampon usage

Vaginal Muscles Two bulbospongiosus muscles extend along either side of vaginal entrance Vestibular bulbs Masses of erectile tissue that lie beneath the muscles Have same embryological origins as corpus spongiosum of penis

The Vaginal Epithelium Is nonkeratinized, stratified, and squamous Forms folds (rugae) Changes with ovarian cycle Vaginal Lamina Propria Is thick and elastic Contains small blood vessels, nerves, and lymph nodes

The Vaginal Mucosa Is surrounded by elastic muscularis layer Layers of smooth muscle fibers Arranged in circular and longitudinal bundles Continuous with uterine myometrium

Figure 28-21 The Histology of the Vagina (Part 1 of 2).
Fornix Vaginal artery Vaginal vein Rugae Vaginal canal Hymen Greater vestibular gland Labia minora Vestibule

Figure 28-21 The Histology of the Vagina (Part 2 of 2).
Stratified squamous epithelium (nonkeratinized) Lumen of vaginal canal Bundles of smooth muscle fibers Lamina propria Blood vessels The vaginal wall LM ×25

Vaginal Bacteria A population of harmless resident bacteria Supported by nutrients in cervical mucus Creates acidic environment Restricts growth of many pathogens A Vaginal Smear Is a sample of epithelial cells shed at surface of vagina Used to estimate stage in ovarian and uterine cycles

The External Genitalia Vulva (or pudendum) Area containing female external genitalia Vestibule A central space bounded by small folds (labia minora) Covered with smooth, hairless skin Urethra opens into vestibule Anterior to vaginal entrance

Paraurethral Glands Also called Skene’s glands Discharge into urethra near external opening The Clitoris A small protuberance in vestibule Has same embryonic structures as penis Extensions of labia minora form prepuce or hood

Vestibular Glands Lesser vestibular glands Secrete onto exposed surface of vestibule Greater vestibular glands (or Bartholin’s glands) Secrete into vestibule near vaginal entrance

Mons Pubis and Labia Majora Form outer limits of vulva Protect and cover inner structures Contain adipose tissue Sebaceous glands and apocrine sweat glands Secrete onto inner surface of labia majora

Figure 28-22 The Female External Genitalia.
Mons pubis Clitoris Prepuce Glans Vestibule Urethral opening Labia minora Vestibular bulb Vaginal entrance Hymen (torn) Labia majora Greater vestibular gland Anus

The Mammary Glands Secrete milk to nourish an infant (lactation) Are specialized organs of integumentary system Are controlled by hormones of reproductive system and the placenta Lie in pectoral fat pads deep to skin of chest Nipple on each breast Contains ducts from mammary glands to surface Areola Reddish-brown skin around each nipple

Mammary Glands Consist of lobes Each containing several secretory lobules Separated by dense connective tissue

Suspensory Ligaments of the Breast Bands of connective tissue Originate in dermis of overlying skin Areolar tissue separates mammary gland complex from underlying pectoralis muscles Blood Supply of Mammary Glands Branches of internal thoracic artery

Mammary Gland Ducts Leave lobules Converge Form single lactiferous duct in each lobe Lactiferous Duct Enlarges Forms expanded chamber (lactiferous sinus) 15–20 lactiferous sinuses open to each nipple

An Active Mammary Gland Is a tubuloalveolar gland Consisting of multiple glandular tubes Ending in secretory alveoli Does not complete development unless pregnancy occurs

Figure 28-23a The Mammary Gland.
Pectoralis major muscle Pectoral fat pad Suspensory ligaments Lobules of two lobes of the mammary gland Lactiferous duct Areola Nipple Lactiferous sinus a The mammary gland of the left breast

Figure 28-23b The Mammary Gland.
Secretory alveoli Lactiferous duct Connective tissue Resting mammary gland LM×100 b An inactive mammary gland of a nonpregnant woman

Figure 28-23c The Mammary Gland.
Secretory alveoli Lactiferous duct Milk Active mammary gland LM×131 c An active mammary gland of a nursing woman

Hormones and the Female Reproductive Cycle Involve secretions of pituitary gland and gonads Form a complex pattern that coordinates ovarian and uterine cycles Circulating hormones Control female reproductive cycle Coordinate ovulation and uterus preparation

Hormones and the Female Reproductive Cycle GnRH from the hypothalamus regulates reproductive function GnRH pulse frequency and amplitude change over course of ovarian cycle Changes in GnRH pulse frequency are controlled by: Estrogens that increase pulse frequency Progestins that decrease pulse frequency

The Endocrine Cells Of anterior lobe of the pituitary Each group of endocrine cells: Responds to different GnRH pulse frequencies Is sensitive to some frequencies, insensitive to others

Hormones and the Follicular Phase Begins with FSH stimulation Monthly Some primordial follicles develop into primary follicles As follicles enlarge: Thecal cells produce androstenedione

Androstenedione Is a steroid hormone Is an intermediate in synthesis of estrogens and androgens Is absorbed by granulosa cells and converted to estrogens

Interstitial Cells Scattered throughout ovarian stroma Also secrete small amounts of estrogens Circulating estrogens Are bound primarily to albumins Lesser amounts carried by gonadal steroid-binding globulin (GBG) Three types: estradiol, estrone, and estriol

Estradiol Is most abundant Has most pronounced effects on target tissues Is dominant hormone prior to ovulation

Estrogen Synthesis Androstenedione is converted to testosterone Enzyme aromatase converts testosterone to estradiol Estrone and estriol are synthesized from androstenedione

Cholesterol Androstenedione Other Estrogens Progesterone Androgens
Figure Pathways of Steroid Hormone Synthesis in Males and Females. Aromatase Cholesterol Androstenedione Other Estrogens Estrone Progesterone Androgens Estriol In some tissues Progesterone Testosterone Dihydrotestosterone Aromatase Estradiol KEY = Common pathways = Primary pathways in females = Primary pathways in males

Five Functions of Estrogen Stimulates bone and muscle growth Maintains female secondary sex characteristics Such as body hair distribution and adipose tissue deposits Affects central nervous system (CNS) activity Especially in the hypothalamus, where estrogens increase the sexual drive Maintains functional accessory reproductive glands and organs Initiates repair and growth of endometrium

Figure 28-24 Regulation of Female Reproduction (Part 3 of 6).
The ovarian and uterine cycles must operate in synchrony to ensure proper reproductive function. If the two cycles are not properly coordinated, infertility results. A female who doesn’t ovulate cannot conceive, even if her uterus is perfectly normal. A female who ovulates normally, but whose uterus is not ready to support an embryo, will also be infertile. HYPOTHALAMUS As in males, GnRH from the hypothalamus regulates reproductive function in females. However, in females, GnRH levels change throughout the course of the ovarian cycle. 1 Release of Gonadotropin-Releasing Hormone (GnRH) The cycle begins with the release of GnRH, which stimulates the production and secretion of FSH and the production—but not the secretion— of LH. KEY Stimulation Release of GnRH Inhibition ANTERIOR LOBE OF PITUITARY GLAND 2 3 Follicular Phase of the Ovarian Cycle Luteal Phase of the Ovarian Cycle Production and secretion of FSH Production of LH The follicular phase begins when FSH stimulates some secondary follicles to develop into a tertiary follicle. The combination of increased GnRH pulse frequency and elevated estrogen levels stimulates LH secretion. Secretion of LH On or around day 14, a massive surge in LH level triggers (1) the completion of meiosis I by the primary oocyte, (2) the forceful rupture of the follicular wall, (3) ovulation, roughly 9 hours after the LH peak, and (4) formation of the corpus luteum. As secondary follicles develop, FSH levels decline due to the negative feedback effects of inhibin. Negative feedback

Follicular Phase of the Ovarian Cycle Developing follicles also secrete estrogens, especially estradiol, the dominant hormone prior to ovulation. 3 Luteal Phase of the Ovarian Cycle OVARY After day 10 The corpus luteum secretes progesterone, which stimulates and sustains endometrial development. Before day 10 • Meisois I completion • Ovulation • Corpus luteum formation In low concentrations, estrogens inhibit LH secretion. This inhibition gradually decreases as estrogen levels increase. • Follicle development • Secretion of inhibin estrogens After ovulation, progesterone levels rise and estrogen levels fall. This suppresses GnRH secretion. If pregnancy does not occur, the corpus luteum will degenerate after 12 days, and as progesterone levels decrease, GnRH secretion increases, and a new cycle begins. Secretion of progesterone Effects on CNS Stimulation of bone and muscle growth Establishment and maintenance of female secondary sex characteristics Maintenance of accessory glands and organs Stimulation of endometrial growth and secretion KEY Stimulation Inhibition

FOLLICULAR PHASE OF OVARIAN CYCLE LUTEAL PHASE OF OVARIAN CYCLE 50 40 LH Gonadotropic hormone levels (IU/L) 30 GnRH pulse frequency (pulses/day) 20 FSH 10 Follicle stages during the ovarian cycle Corpus luteum formation Mature corpus luteum Corpus albicans Follicle development Ovulation Progesterone Ovarian hormone levels Estrogens Inhibin 28/0 7 14 21 28/0 Days

FOLLICULAR PHASE OF OVARIAN CYCLE LUTEAL PHASE OF OVARIAN CYCLE Destruction of functional zone Repair and regeneration of functional zone Secretion by uterine glands Endometrial change during thes uterine cycle Phases of the uterine cycle MENSES PROLIFERATIVE PHASE SECRETORY PHASE 36.7 Basal body temperature (C) 36.4 28/0 7 14 21 28/0 Days

Summary: Hormonal Regulation of the Female Reproductive Cycle Early in follicular phase of ovarian cycle: Estrogen levels are low GnRH pulse frequency is 16–24/day (1 per 60–90 minutes) As tertiary follicles form, concentration of circulating estrogens rises steeply And GnRH pulse frequency increases to 36/day (1 per 30–60 minutes)

Summary: Hormonal Regulation of the Female Reproductive Cycle In follicular phase: Switchover occurs When estrogen levels exceed threshold value for about 36 hours Resulting in massive release of LH from the anterior lobe of the pituitary gland

Summary: Hormonal Regulation of the Female Reproductive Cycle In follicular phase: Sudden surge in LH concentration triggers: Completion of meiosis I by primary oocyte Rupture of follicular wall Ovulation Ovulation occurs 34–38 hours after LH surge begins (nine hours after LH peak)

Summary: Hormonal Regulation of the Female Reproductive Cycle In luteal phase of ovarian cycle: High LH levels trigger ovulation Promote progesterone secretion Trigger formation of corpus luteum Frequency of GnRH pulses stimulates LH more than FSH LH maintains structure and secretory function of corpus luteum

Summary: Hormonal Regulation of the Female Reproductive Cycle Luteal phase Progesterone levels remain high for one week Unless pregnancy occurs, corpus luteum begins to degenerate Progesterone and estrogen levels drop GnRH pulse frequency increases Stimulating FSH secretion Ovarian cycle begins again

Hormones and the Uterine Cycle Corpus luteum degenerates Progesterone and estrogen levels decline Resulting in menses Endometrial tissue sheds several days Until rising estrogen stimulates regeneration of functional zone

Hormones and the Uterine Cycle Proliferative phase continues Until rising progesterone starts secretory phase Increase in estrogen and progesterone Causes enlargement of endometrial glands And increase in secretory activities

Hormones and Body Temperature Monthly hormonal fluctuations affect core body temperature During luteal phase, progesterone dominates During follicular phase, estrogen dominates and basal body temperature decreases about 0.3C Upon ovulation, basal body temperature (BBT) declines noticeably Day after ovulation, temperature rises

28-4 Sexual Function Autonomic Function Controls the Reproductive System Coitus (Copulation) Sexual intercourse Introduces semen into female reproductive tract

28-4 Sexual Function Male Sexual Function
Is coordinated by complex neural reflexes Using sympathetic and parasympathetic divisions of ANS Male sexual arousal Leads to increase in parasympathetic outflow over pelvic nerves, which leads to erection

28-4 Sexual Function Male Sexual Stimulation
Initiates secretion of bulbourethral glands Lubricates penile urethra and surface of glans Leads to coordinated processes of emission and ejaculation

28-4 Sexual Function Emission Occurs under sympathetic stimulation
Peristaltic contractions of ampulla Push fluid and spermatozoa into prostatic urethra Seminal glands contract Increasing in force and duration Peristaltic contractions in prostate gland Move seminal mixture into urethra Sympathetic contraction of urinary bladder and internal urethral sphincter Prevents passage of semen into bladder

28-4 Sexual Function Ejaculation
Occurs as powerful, rhythmic contractions In ischiocavernosus and bulbospongiosus muscles That stiffen penis Push semen toward external urethral opening Causes pleasurable sensations (orgasm) Followed by subsidence of erectile tissue (detumescence)

28-4 Sexual Function Impotence Also called male sexual dysfunction
Is an inability to achieve or maintain an erection Caused by physical or psychological factors

28-4 Sexual Function Female Sexual Function
Parasympathetic activation leads to: Engorgement of erectile tissues Increased secretion of cervical mucous glands and greater vestibular glands Blood vessels in vaginal walls fill with blood Fluid moves from underlying connective tissues To vaginal surfaces

28-4 Sexual Function Female Orgasm Is accompanied by:
Peristaltic contractions of uterine and vaginal walls Rhythmic contractions of bulbospongiosus and ischiocavernosus muscles

28-4 Sexual Function Sexually Transmitted Diseases (STDs)
Are transferred by sexual intercourse Include bacterial, viral, and fungal infections Pelvic inflammatory disease (PID) AIDS Gonorrhea Syphilis Herpes Genital warts Chancroid

28-5 Effects of Aging on the Reproductive System
Female reproductive system Changes associated with menopause Male reproductive system Changes associated with male climacteric (andropause) Occur gradually, over longer time period

Menopause Is the time that ovulation and menstruation cease Typically occurs around age 45–55 Circulating concentrations of estrogens and progesterone decline Production of GnRH, FSH, and LH rises sharply

Perimenopause The interval immediately preceding menopause Ovarian and uterine cycles become irregular Due to shortage of primordial follicles Estrogen levels decline Ovulation is not triggered

Decline in Estrogen Levels Leads to: Reduction in uterus and breast size Thinning of urethral and vaginal epithelia Reduction in bone deposition (osteoporosis)

The Male Climacteric (Andropause) Is the period of declining reproductive function Circulating testosterone begins to decline Between ages 50 and 60 Circulating FSH and LH increase Sperm production continues Sexual activity gradually decreases With declining testosterone levels

28-6 Sex Hormones and Homeostasis
Males Sperm count must be adequate Semen must have correct pH and nutrients Erection and ejaculation must function properly

28-6 Sex Hormones and Homeostasis
Females Ovarian and uterine cycles must coordinate properly Ovulation and oocyte transport must occur normally Environment of reproductive tract must support: Survival and movement of sperm Fertilization of oocyte

Table 28-1 Hormones of the Reproductive System.

28-6 Reproductive System Integration
Human Reproduction Requires normal function of multiple systems Reproductive system Digestive system Endocrine system Nervous system Cardiovascular system Urinary system

The REPRODUCTIVE System
Figure diagrams the functional relationships between the reproductive system and the other body systems. SYSTEM INTEGRATOR Body System Reproductive System Reproductive System Body System Covers external genitalia; provides sensations that stimulate sexual behaviors; mammary gland secretions nourish the newborn Reproductive hormones affect distribution of body hair and subcutaneous fat deposits Integumentary Integumentary Page 174 Pelvis protects reproductive organs of females, portion of ductus deferens and accessory glands in males Sex hormones stimulate growth and maintenance of bones; sex hormones at puberty accelerate growth and closure of epiphyseal cartilages Skeletal Skeletal Page 285 Contractions of skeletal muscles eject semen from male reproductive tract; muscle contractions during sexual act produce pleasurable sensations in both sexes Reproductive hormones, especially testosterone, accelerate skeletal muscle growth Muscular Muscular Page 380 Controls sexual behaviors and sexual function Sex hormones affect CNS development and sexual behaviors Nervous Nervous Page 558 Endocrine Hypothalamic regulatory hormones and pituitary hormones regulate sexual development and function; oxytocin stimulates smooth muscle contractions in uterus and mammary glands Steroid sex hormones and inhibin inhibit secretions from the hypothalamus and pituitary gland Endocrine Page 647 Distributes reproductive hormones; provides nutrients, oxygen, and waste removal for fetus; local blood pressure changes responsible for physical changes during sexual arousal Estrogens may help maintain healthy vessels and slow development of atherosclerosis Cardiovascular Cardiovascular Page 776 Lymphatic Provides IgA for secretions by epithelial glands; assists in repairs and defense against infection Lysozymes and bactericidal chemicals in secretions provide innate immunity against reproductive tract infections Lymphatic Page 824 Provides oxygen and removes carbon dioxide generated by tissues of reproductive system and (in pregnant women) by a growing embryo and fetus Changes in respiratory rate and depth occur during sexual arousal, under control of the nervous system Respiratory Respiratory The Male Reproductive System Page 874 Provides additional nutrients required to support gamete production and (in pregnant women) embryonic and fetal development In pregnant women, digestive organs are crowded by developing fetus, constipation is common, and appetite increases Digestive Digestive Page 929 Urinary Urethra in males carries semen to exterior; kidneys remove wastes generated by reproductive tissues and (in pregnant women) by a growing embryo and fetus Accessory organ secretions may have antibacterial action that helps prevent urethral infections in males Urinary Page 1010 The REPRODUCTIVE System For all systems, the reproductive system secretes hormones with effects on growth and metabolism. Figure 28–26 diagrams the functional relationships between the reproductive system and the other body systems.

An Introduction to the Reproductive System

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An Introduction to the Reproductive System

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