Chapter 28: The Reproductive System

Chapter 28: The Reproductive System
Primary sources for figures and content: Marieb, E. N. Human Anatomy & Physiology. 6th ed. San Francisco: Pearson Benjamin Cummings, 2004. Martini, F. H. Fundamentals of Anatomy & Physiology. 6th ed. San Francisco: Pearson Benjamin Cummings, 2004.

The Reproductive System
Primary sex organs = gonads Gonads: organs that produce gametes and hormones Gametes = sex cells; ovum and sperm Sex cells are Haploid (n): have half normal chromosome number (23 vs. 46) All human tissue = somatic cells are Diploid (2n) 46 chromosomes, 23 homologous pairs (1) 1n/23 chrom. ovum + (1) 1n/23 chrom. sperm  (1) 2n/46 chromosome zygote, fertilized ovum Zygote will divide by mitosis to produce all diploid somatic cells of the body

Male and Female Reproductive Systems
Are functionally different Female produces 1 gamete per month: retains and nurtures zygote Male disseminates large quantities of gametes: produces 1/2 billion sperm per day

The Reproductive System
Gametogenesis Process of gamete formation 2n somatic cells produce 1n sex cells Reducing chromosome number by half requires special cell division  meiosis

Chromosomes in Mitosis and Meiosis
Figure 28–6

Mitosis 2n (duplicated) cell  two 2n daughter cells
All daughter cells are identical One 2n cell duplicates its DNA: each duplicated chromosome consists of two sister chromatids Sister chromatids are separated equally during anaphase Now single chromosomes are in each new daughter cell Two identical diploid daughter cells result Process of cell division used by all somatic cells

Meiosis 2n (duplicated)  four 1n daughter cells
All daughter cells are different One 2n cell duplicates its DNA Each duplicated chromosome consists of two sister chromatids Homologous chromosome undergo synapsis Pair up forming tetrads Tetrads = four sister chromatids or 2 duplicated chromosomes Homologous chromosomes exchange by cross-over

Meiosis In Meiosis I homologous chromosomes separate
Cells now haploid with duplicated chromosomes In Meiosis II sister chromatids separate (now single chromosomes) Producing four haploid cells, all genetically different Process of cell division only used for sex cell production

Male Reproductive System

The Male Reproductive System
Consists of male gonads = testes secrete male sex hormones (androgens) produce male gametes (spermatozoa or sperm) Accessory reproductive organs Ducts Glands External genitalia that aid sperm production/delivery

Summary: Male Reproductive System
Emission: mature spermatozoa move along duct system Semen: sperm mixed with accessory gland secretions Ejaculation: semen expelled from body

The Male Reproductive System
PLAY Male Reproductive System Flythrough Figure 28–1

Pathway of Spermatozoa
Testis Epididymis Ductus deferens (vas deferens) Ejaculatory duct Urethra

Accessory Organs Secrete fluids into ejaculatory ducts and urethra:
seminal vesicles prostate gland bulbourethral glands

Male Reproductive System
Figure 28–3

Scrotum Sac of cutaneous membrane, fascia, and muscle
External to abdominopelvic cavity 2 chambers, divided by raphae Each supports one testis Maintains testes at optimal temp for sperm development (36.2°C/96.5°F) Normal sperm development in testes requires temperatures 1.1°C (2°F) lower than body temperature Two muscles regulate temp. 1. Dartos muscle 2. Cremaster muscle

Scrotum Two muscles regulate temp. 1. Dartos muscle
Smooth muscle in the dermis Causes surface wrinkling to reduce heat loss 2. Cremaster muscle Skeletal muscle from internal obliques Adjusts proximity of the testes to the body Tenses scrotum and pulls testes closer to body (temperature regulation)

Testes = male gonads Produce gamates (sperm) and hormones: androgens (testosterone) and inhibin Development Form in abdominal cavity Same tissue and position as ovaries Descend prior to birth through inguinal canal Are passageways through abdominal musculature

The Fetus 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 are accompanied by pockets of peritoneal cavity

Descent of the Testes Figure 28–2a

Descent of the Testes Figure 28–2b

Accessory Structures Accompany testis during descent
Form body of spermatic cord: ductus deferens testicular blood vessels, nerves, and lymphatic vessels

Problems with Descent 1. Cryptorchidism Failure of restes to descen
3% full term, 30% premature births Internal testis will be sterile 2. Male Inguinal Hernias Are protrusions of visceral tissues, intestines, into inguinal canal Spermatic cord (in closed inguinal canal): causes weak point in abdominal wall

Testes Structure Surrounded by two tunics 1. Tunica vaginalis
Derived from peritoneum Parietal and visceral layers 2. Tunica albuginea Fibrous capsule of testis Partitions of tunica albuginea divides testis into lobules Each lobule contains 1-4 coiled seminiferous tubules

Structure of the Testes
Figure 28–4

Testes Seminiferous tubules converge into rete testis (inside the testis)  efferent ductules (superior and exterior to testis)  single epididymis (coiled around outside of testis) Epididymis transmits sperm to ductus/vas deferens Connects testis to urethra Testes connected to abdominopelvic cavity by spermatic cord. Composed of: CT surrounding ductus deferens Blood and lymphatic vessels Autonomic nerves supplying testes Vasectomy = Surgical sterilization Sever ductus deferens in spermatic cord

Testes Figure 28–9

Testes Functional regions of testes 1. Interstitial cells
In CT around seminiferous tubules Produce androgens (testosterone) 2. Seminiferous tubules Surrounded by capsule and areolar CT outer edge lined with spermatogonia Spermatogonia = sperm stem cell Spermatogonia divide and differentiate to produce spermatozoa for release into lumen Also contain sustentacular cells Aid sperm differentiation Extend from basement membrane to lumen

The Seminiferous Tubules
Figure 28–5b Testis contains about 1/2 mile of tightly-coiled seminiferous tubules Figure 28–5a

The Seminiferous Tubules
Figure 28–5c

Spermatogenesis = Sperm formation
Occurs in seminiferous tubules, aided by sustentacular cells Begins with stem cells = spermatogonium outer most tubule cell, contacts basement membrane As cells divide and differentiate they migrate toward the lumen of tubule

5 Steps in Spermatogenesis
Stem cells (spermatogonia) divide by mitosis: to produce 2 daughter cells: 1 remains as spermatogonium second differentiates into primary spermatocyte Primary spermatocytes: begin meiosis form secondary spermatocytes Secondary spermatocytes: differentiate into spermatids (immature gametes) Spermatids: differentiate into spermatozoa Spermatozoa: lose contact with wall of seminiferous tubule enter fluid in lumen

Chromosomes in Mitosis and Meiosis
Figure 28–6

Spermatogenesis Involves 3 integrated processes: 1. mitosis 2. meiosis
3. spermiogenesis

1. Mitosis Spermatogonium  primary spermatocyte
Spermatogonia divide producing daughter cells Daughter cell A Remains at basement membrane as spermatogonium Daughter cell B Differentiates into a primary spermatocyte and moves toward the lumen

2. Meiosis Primary spermatocyte  spermatid
The diploid primary spermatocyte undergoes meiosis I to generate two diploid secondary spermatocytes The secondary spermatocytes complete meiosis II producing four spermatids gametes contain 23 chromosomes Fusion of male and female gametes produces: zygote with 46 chromosomes

3. Spermiogenesis Spermatid  sperm/spermatozoa
Involves major structural changes The round spermatids differentiate into small, streamlined motile cells at the lumen A long flagellum is formed The chromosomes are compacted Excess cytoplasm (cytosol and organelles) is shed Complete cellular transformation takes ~5 weeks

Spermatogenesis 2n 2n 1n (haploid with duplicated chromosomes, sister chromatid) 1n (haploid with single chromosomes) Figure 28–7

Chromosomes in Spermatogenesis
Meiosis I and meiosis II: produce 4 haploid cells, each with 23 chromosomes Prophase I: chromosomes condense each chromosome has 2 chromatids Synapsis: maternal and paternal chromosomes come together 4 matched chromatids form tetrad Crossing over: some genetic material is exchanged increases genetic variation among offspring

Metaphase I: tetrads line up along metaphase plate Anaphase I: maternal and paternal chromosomes separate each daughter cell receives whole chromosome: maternal or paternal Independent assortment: as each tetrad splits maternal and paternal components are randomly distributed Telophase I ends: with formation of two daughter cells with unique combinations of chromosomes Both cells contain 23 chromosomes with 2 chromatids each

Interphase: separates meiosis I and meiosis II is very brief DNA is not replicated Meiosis II: proceeds through prophase II and metaphase II Anaphase II: duplicate chromatids separate Telophase II: yields 4 cells, each containing 23 chromosomes

KEY CONCEPT Meiosis produces gametes:
that contain 1/2 of chromosomes in somatic cells For each cell entering meiosis: testes produce 4 spermatozoa ovaries produce 1 ovum and 3 polar bodies

Spermiogenesis and Spermatozoon Structure
Figure 28–8a

Structure of sperm/spermatozoon
1. Head (genetic part) Flattened nucleus, compact DNA Covered by acrosome Lysosome-like cap containing hydrolytic enzymes for ovum penetration 2. Midpiece (metabolic part) Contains mitochondria  ATP To power contractile filaments of flagella 3. Tail (locomotor region) Flagellum: whip-like motion to propel cell

Figure 28–8b

Spermiogenesis Is the last step of spermatogenesis
Each spermatid matures into 1 spermatozoon (sperm): attached to cytoplasm of sustentacular cells (sertoli cells)

Sustentacular (sertoli) cells
Figure 28–5b

Role of Sertoli (sustentacular) Cells in Spermatogenesis
1. Maintenance of blood-testis barrier Cells linked by tight junctions Regulate environment inside tubule  High levels of androgens, estrogens, K+, amino acids (testicular fluid) Excludes leukocytes 2. Support mitosis and meiosis Stimulated by FSH and testosterone Promote cell division 3. Support during spermeogenesis Hold spermatids and stimulate development

Role of Sertoli (sustentacular) Cells in Spermatogenesis
4. Secrete inhibin Peptide hormone, inhibits FSH and GnRH Negative feedback for spermatogenesis 5. Secrete Androgen Binding Protein Binds androgens to retain them in tubule to stimulate spermiogenesis 6. Secrete Mullerian Inhibiting Factor Causes regression of fetal Müllerian ducts (uterus, uterine tubes)

Fetal Müllerian 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

Figure 28–8a

KEY CONCEPT Spermatogenesis:
begins at puberty and continues past age 70 is a continuous process All stages of meiosis are observed within seminiferous tubules

Reproductive Tract Spermatogenesis is seminiferous tubule takes days Immature sperm released into testicular fluid in lumen of tubule Moved by fluid pressure and cilia to epididymis Includes 1. Epididymis 2. Ductus deferens 3. Urethra

1. The Epididymis Figure 28–9

Functionally Immature Spermatozoa
Are incapable of locomotion or fertilization Are moved by cilia lining efferent ductules: into the epididymis

1. Epididymis 6 meter coiled tubule around top and side of testis
Functions 1. Monitor and adjust composition of testicular fluid Stereocilia absorb or secrete 2. Recycle damaged spermatozoa 3. Protect, store, facilitate maturation of sperm Transit takes ~20 days, sperm mature and gain ability to be motile Mature sperm stored few months During ejaculation, smooth muscle in wall propels sperm to ductus deferens

2. Ductus deferens Passes through inguinal canal (anterior to pubis) as part of the spermatic cord loops over ureter  descends posterior to bladder Ends in ampulla Connects to seminal vesicles and prostate During ejaculation peristaltic contractions transmit sperm from storage in epididymis  ejaculatory duct to mix with glandular secretions which activate sperm (now motile) Ejaculatory duct connects ampulla to urethra

Spermatozoa Leaving Epididymis
Are mature, but remain immobile To become motile (actively swimming) and functional: spermatozoa undergo capacitation Spermatozoa become motile: when mixed with secretions of seminal vesicles Spermatozoa become capable of fertilization: when exposed to female reproductive tract

The Ductus Deferens Figure 28–10a, b

3. Urethra Shared by urinary and reproductive systems 3 regions
1. Prostatic urethra Connects to urinary bladder and ejaculatory duct, passes through prostate 2. Membranous urethra Passes through body wall (urogenital diaphragm) 3. Spongy/penile urethra Length of penis, opens at external urethral orifica

Accessory Glands Produce fluid, nutrients, enzymes, buffers, that comprise bulk of semen Semen = sperm + gland secretions Accessory gland Seminal Vesicles Prostate Gland Bulbourethral Gland

4 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

1. Seminal Vesicle Figure 28–10a, c

1. Seminal vesicle On posterior bladder wall
Are extremely active secretory glands Produce about 60% of semen volume Produce seminal fluid 1. Fructose: nutrients to drive sperm motility 2. Prostaglandins: promote smooth muscle contraction to aid sperm mobility 3. Fibrinogen: converted to fibrin to form clot in vagina 4. Vasiculase: enzyme for fibrinogen conversion 5. Alkaline buffer: buffer acid pH of vagina During ejaculation sperm mixed with seminal fluid in ejaculatory duct become highly motile

2. Prostate Gland Figure 28–10a, d

2. Prostate Gland Encircles prostatic urethra
Forms 20–30% of semen volume Secretes prostatic fluid into urethra 1. Enzymes to digest cervical mucus 2. Fibrinolysin  breaks down semen clot to release sperm in vagina 3. Seminalplasmin  antibiotic

3. Bulbourethral Gland Figure 28–10a, e

3. Bulbourethral Gland In urogenital diaphragm Secrete alkaline mucus
Neutralize urinary acids and lubricate glans Duct of each gland: travels alongside penile urethra empties into urethral lumen

Semen 2-5 ml/ejaculation 60% seminal fluid 30% prostatic fluid
10% testicular fluid + active spermatozoa million sperm/ml Less than 60 million total = sterile

External Genitalia 1. Scrotum 2. Penis
Function: deliver sperm to female tract 3 parts 1. Root: attaches to body wall 2. Shaft: tubular, houses erectile tissue 3. Glans: distal end, covered by perpuce preputial glands secrete smegma Circumcision: remove prepuce Prevents UTI’s

The Penis Figure 28–11b, c

2. The Penis Shaft contains 3 columns of erectile tissue
1. (2) corpora cavernosa Anterior, stiffen shaft 2. (1) corpus spongiosum Surrounds urethra Distal end forms glans Holds urethra open Erectile tissue Vascular channels surrounded by elastic CT and smooth muscle Fills with blood via parasympathetic stimulation

2. The Penis Figure 28–11a, b

Male Sexual Function 1. Erection
Triggered by tactile or mental stimuli Parasympathetic triggers release of NO No dilates arterioles  blood fills channels Expansion compresses drainage veins  blood pressure = stiff Parasympathetic also triggers secretion from bulbourethral glands Eventually spinal reflex triggered ejaculation

Male Sexual Function 2. Ejaculation
Spinal reflex  sympathetic stimulation Ducts and glands contract emptying contents to urethra Skeletal muscles of penis contract, semen propelled out uretheral oridice 3. Detumescence Erection subsides Sympathetic constricts arterioles Latent period New ejaculation not possible (min-hrs)

Male Sexual Function Impotence
Inability to achieve or maintain erection Due to Alcohol, drugs, or hormonal, vascular, or nervous system problems

Hormonal mechanisms regulate male reproductive functions.

Hormonal and Male Reproductive Function
Figure 28–12

Male Hormones and Repro. Function
1. GnRH is released consistently in minutes intervals from the hypothalamus This triggers release of FSH and LH from the anterior pituitary 2. FSH targets sertoli (sustentacular) cells to Promote spermatogenesis Promote secretion of androgen binding protein As spermatogenesis increases it triggers release of inhibin Inhibin decr. GnRH and FSH by negative feedback 3. LH targets interstitial cells LH promotes the secretion of androgens (testosterone)

Male Hormones and Repro. Function
4. Testosterone Stimulates spermatogenesis binds to antigen binding protein Promotes sex drive in CNS Stimulates metabolism Especially skeletal muscle growth Establishes/maintain male secondary sex characteristics Maintains accessory organs of the reproductive tract As levels increase, testosterone inhibits GnRH release by negative feedback The consistent release of GnRH insures that the circulating levels of all the hormones (FSH, LH, and testosterone) remain relatively constant

Inhibin, FSH, LH Elevated FSH levels: If FSH declines: LH
increase inhibin production until FSH returns to normal If FSH declines: inhibin production falls FSH production increases LH Targets interstitial cells of testes Induces secretion of testosterone

Testosterone and Development
Testosterone production: begins around seventh week of fetal development reaches prenatal peak after 6 months Secretion of Müllerian inhibiting factor: by sertoli (sustentacular) cells leads to regression of Müllerian ducts Early surge in testosterone levels: stimulates differentiation of male duct system and accessory organs affects CNS 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% is converted from circulating testosterone: by enzyme aromatase 30% is secreted by interstitial and sustentacular cells of testes

Age Related Changes 1. Male climacteric:
Decrease testosterone = decr. Libido 2. Benign prostatic hypertrophy Prostate increases, can block urethra 3. Increased impotence 4. Sperm motility rate declines

On a warm day, would the cremaster muscle be contracted or relaxed?

What will happen if the arteries within the penis dilate?
impotence becomes flaccid erection erectile disfunction

What effect would low levels of FSH have on sperm production?
higher rate of production lower rate of production malformed sperm no effect on sperm production

Female Reproductive System.

The Female Reproductive System
Figure 28–13

Consists of Female gonads = ovaries Accessory reproductive organs = uterine tubes, uterus, vagina Aid fertilization and embryo growth and delivery

Ovary = female gonads Produce:
Gametes (ova) and hormones estrogen, progesterone, inhibin Lateral to uterus Surrounded by two layers Germinal epithelium Simple cuboidal epithelium, from peritoneum Tunica albuginea Dense CT capsule Cortex Houses forming gametes in ovarian follicles

Ovary = female gonads Stroma  interior tissues of ovary include:
1. Cortex Houses forming gametes in ovarian follicles: Oocyte Surrounding cells Single layer = follicle cells Stratified = granulosa cells Endocrine cells that produce female sex hormones 2. Medulla Contains blood vessels and nerves

Ovary Support Mesovarium Ovarian ligament:
extends from uterus to ovary Suspensory ligament: extends from ovary to pelvic wall Contains major blood vessels of ovary: Ovarian artery and ovarian vein Vessels connect to ovary at ovarian hilum: where ovary attaches to mesovarium

Oogenesis Oogonia = stem cells of females:
complete mitotic divisions before birth Figure 28–15

Oogenesis = oocyte formation
Begins prior to birth and ends at metaphase During fetal development primary oocytes suspended in Meiosis I are formed in primordial follicles From puberty to menopause primary oocytes are activated on a 28 day cycle (the ovarian cycle) to complete Meiosis I to produce one large secondary oocyte and one small polar body At ovulation the secondary oocyte is released from the ovary  suspended in Meiosis II Secondary oocyte will not complete Meiosis to produce a mature ovum until fertilized by a sperm

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

Oogenesis: 2 Characteristics of Meiosis
Cytoplasm of primary oocyte divides unevenly: producing 1 ovum (with original cytoplasm) and 2 or 3 polar bodies (that disintegrate) Ovary releases secondary oocyte (not mature ovum): suspended in metaphase of meiosis II meiosis is completed upon fertilization

Ovarian Cycle

The Ovarian Cycle Figure 28–16 (1 of 2)

The Ovarian Cycle Figure 28–16 (2 of 2)

Ovarian Cycle Follicular Phase (preovulatory phase) Ovulation
Luteal Phase (postovulatory phase)

Ovarian Cycle 1. Follicular Phase Period of follicle growth (day 1-14)
A. Formation of Primary Follicles (day 1-8) Squamous follicle cells of many primordial follicles enlarge into cuboidal cells and begin dividing forming primary follicles The follicular cells produce stratified layers Now called granulosa cells Microvilli form the innermost granulosa cells are connected to the primary oocyte via gap junctions to support and stimulate the growth of the oocyte

A. Formation of Primary Follicles (day 1-8) con’t The granulosa cells secrete glycoproteins  form a thick membrane around the primary oocyte called the zona pellucida Cells form the ovarian cortex form a layer of thecal cells around the outside of the primary follicle Thecal cells and granulosa cells together begin producing estrogens

B. Formation of Secondary Follicles (8-10) Only a few primary follicles continue development to become secondary follicles Granulosa cells begin to secrete follicular fluid The fluid accumulates between the stratified layers of the granulosa cells creating a space called the antrum This is now called a secondary follicle

C. Formation of one Tertiary Follicle (10-14) The primary oocyte becomes restricted to one side of the follicle attached by a stalk and surrounded by a layer of granulosa cells called the corona radiata The antrum continues to expand until the follicle spans the width of the cortex This is now called a tertiary follicle One tertiary or vasicular follicle usually forms 99% of the time The primary oocyte completes meiosis I forming a secondary oocyte and a small polar body

Ovarian Cycle 2. Ovulation Day 14
The tertiary follicle ruptures through the ovarian wall releasing the secondary oocyte Secondary oocytes is surrounded by the zona pellucida and corona radiata (granulosa cells associated with secondary oocyte)

Ovarian Cycle 3. Luteal Phase Day 14-28
The ruptured tertiary follicle collapses and fills with blood The granulosa cells and thecal cells proliferate and reorganize into the corpus luteum The corpus luteum secretes progesterone and some estrogens If pregnancy does not occur: the corpus luteum degenerates and is invaded by fibroblasts The fibroblasts create scar tissue called the corpus albicans If pregnancy occurs: The corpus luteum remains active for 3+ months until the placenta takes over progesterone secretion

KEY CONCEPT Oogenesis begins during embryonic development
Primary oocyte production is completed before birth Each month after puberty: ovarian cycle produces at least 1 secondary oocytes from existing population of primary oocytes Number of viable primary oocytes: declines over time until ovarian cycles end (age 45–55)

Ovaries or female gonads: release 1 immature gamete (oocyte) per month produce hormones Uterine tubes: carry oocytes to uterus If sperm reaches oocyte: fertilization is initiated oocyte matures into ovum

Uterine Tubes Function
Transmit oocyte to uterus Site for fertilization Muscular tube, lined with ciliated columnar epithelium and mucin secreting cells Oocyte moved via peristalsis and cilia Secretions to nourish oocyte (and sperm) Pelvic Inflammatory Disease Infection of uterine tubes N. gonorrhoeae, Chlamydia Scaring can cause infertility

Uterine Tubes 3 regions Transit ovary to uterus takes 3-4 days
1. Infundibulum Expanded end, has fimbriae with cilia that sweep ovarian surface to brush oocyte into uterine tube 2. Ampulla Muscular length Fertilization occurs here 3. Isthmus  connects to uterus Transit ovary to uterus takes 3-4 days Ectopic pregnancy Implantation of zygote in location other than uterus (0.6%), most spontaneously abort

Uterine Tube Also known as Fallopian tubes or oviducts Figure 28–14

The Uterine Tubes Figure 28–17a, b

Uterine Tube and Oocyte Transport
From infundibulum to uterine cavity: normally takes 3–4 days

The Uterus Figure 28–18a

Uterus Anterior to rectum, posterior and superior to bladder Function
House and nourish fertilized ovum Two regions 1. Body 2. Cervix

Uterus 1. Body Main portion, was has 3 layers
1. Perimetrium = visceral peritoneum 2. Myometrium = Middle, thick muscular Smooth muscle arranged into longitudinal, circular, and oblique layers Provides force to move fetus out of uterus into vagina 3. Endometrium = Inner, glandular mucosa Simple columnar epithelium over thick lamina propria Glandular and vascular tissues support physiological demands of growing fetus 2 zones 1. Functional zone Basilar zone

Uterus 1. Body 2 zones 1. Functional zone
Thick, borders uterine cavity, glands, vessels and epithelium change with hormones through uterine cycle Shed in mensus 2. Basilar zone Thin, borders myometrium, remains constant Gives rise to new function zone after mensus

The Uterine Wall Figure 28–19

Uterus 2. Cervix Inferior, tubular
Connects to vagina through cervical canal at external os (orifice) Mucosa has cervical glands Secrete thick mucus to block canal to prevent infections Mucus thins at mid ovarian cycle for sperm entry Prolapse of the uterus Damage to supporting ligaments results in uterus protruding through vaginal opening

The Uterus Provides for developing embryo (weeks 1–8) and fetus (week 9 through delivery): mechanical protection nutritional support waste removal

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 Unfertilized oocyte Degenerate in terminal portions of uterine tubes or within uterus

The Uterus Figure 28–18b

difficulty in conceiving no effect on conception
As the result of infections such as gonorrhea, scar tissue can block the lumen of each uterine tube. How would this blockage affect a woman’s ability to conceive? easier to conceive sterility difficulty in conceiving no effect on conception

Which layer of the uterus is sloughed off during menstruation?
myometrium basilar zone of the endometrium functional layer of the endometrium perimetrium

Uterine Cycle Figure 28–20

3 Phases of the Uterine Cycle
Menses Proliferative phase Secretory phase

Uterine Cycle (Menstrual Cycle)
Corresponds with ovarian cycle Same hormones regulate both 1. Mensus (day 1-5) Correlates with beginning of follicular phase at ovary Arteries constrict, tissues and glands of functional zone deteriorate Necrotic vessels rupture, blood flushes necrotic endometrial tissue out of uterus to vagina = menstruation Menstruation = loss of functional zone of endometrium

Uterine Cycle (Menstrual Cycle)
2. Proliferative phase (day 6-14) Correlates with follicular enlargement and oocyte maturation Cells of basilar zone of endometrium multiply to restore the mucosa, glands, and vessels of the function zone 3. Secretory phase (day 15-28 Correlates with ovulation and duration of luteal phase Endometrial glands enlarge and secrete mucus rich in glycogen to nourish potential embryo Secretion peaks 12 days post ovulation then declines as corpus luteum ceases hormone production In pregnancy occurs, secretion will continue and mensus will be inhibited

Uterine Cycle Endometriosis Endometrial tissue growing outside uterus
Painful mass that cycles Requires drugs or surgery Menarche = first menstrual cycle Menophase = last menstrual cycle Amenorrhea Failure to initiate mensus Due to physical exertion and low body mass Leptin permissive on gonadotropins

What changes would you expect to observe in the ovarian cycle if the LH surge did not occur?
premature ovulation no follicular development oogenesis would not occur ovulation and corpus luteum formation would not occur

What effect would a blockage of progesterone receptors in the uterus have on the endometrium?
inhibit menstruation inhibit glandular secretion inhibit initial thickening of endometrium promote development of endometrial lining

What event occurs in the uterine cycle when the levels of estrogens and progesterone decline?
pregnancy menarche menses menopause

Vagina Figure 28–21

Vagina Functions to receive penis and deliver infants and menstrual flow Elastic muscular tube, connect cervix to vestibule (external genitalia) 3 wall layers 1. Adventitia 2. Muscularis 3. Mucosa: stratified squamous epithelium Folded into rugae when relaxed Epithelium secretes glycogen Resident bacteria metabolize into lactic acid, low pH prevents pathogen colonization

Vaginitis Is an inflammation of the vaginal canal
Is caused by fungi, bacteria, or parasites

A Vaginal Smear Is a sample of epithelial cells shed at surface of vagina Used to estimate stage in ovarian and uterine cycles

What is the advantage of the acidic pH of the vagina?
enhances sperm motility prevents mucus secretions maintains epithelial lining prevents bacterial, fungal, and parasitic infections

The Female External Genitalia
Figure 28–22

External genitalia = Vulva
1. Mons pubis Anterior vulva, adipose over pubic symphasis 2. Labia majora Lateral vulva (=male scrotum), surrounds labia minora 3. Labia minora Encloses vestibule (=ventral penis)

External genitalia = Vulva
4. Vestibule Urethral orifice anterior, vaginal orifice posterior, flanked by greater vestibular glands (=bulbourethral glands) that produce secretions to lubericate vestibule 5. Clitoris Anterior to vestibule Erectile tissue (=corpus cavernosa) Covered by prepuce – formed by anterior labia

The Mammary Glands Figure 28–23a

Mammary Glands Lactation - Milk to nourish newborn
Modified sweat glands over pectoralis muscles Center = areola Pigmented skin around nipple Divided into ~25 lobes around nipple, CT and adipose between lobes Lobe contains lobules of alveoli – glandular structures that produce milk Lobule empties to lactiferous duct, exits lobe to lactiferous sinus Sinus stores milk during nursing Pregnancy causes proliferation of alveolar tissue for milk production

Circulating Hormones Control female reproductive cycle
Coordinate ovulation and uterus preparation

GnRH GnRH from hypothalamus: GnRH pulse frequency and amplitude:
regulates reproductive function GnRH pulse frequency and amplitude: change over course of ovarian cycle Changes in GnRH pulse frequency: are controlled by estrogens and progestins Estrogens increase pulse frequency Progestins decrease pulse frequency

Pathways of Steroid Hormone Synthesis in Males and Females
Figure 28–24

Follicular Development
Begins with FSH stimulation Monthly: some primordial follicles develop into primary follicles As follicles enlarge: thecal cells produce androstenedione

The Hormonal Regulation of Ovarian Activity
Figure 28–25

Hormones and the Female Reproductive Cycle
Ovarian and uterine cycles must be coordinated to allow fertilization and implantation of an embryo GnRH levels changes over the duration of the cycles to alter the levels of FSH and LH FSH and LH Control the secretion of the female sex hormones estrogen and progesterone Sex hormone levels drive oocyte maturation and uterus development

1. Follicular Phase GnRH levels begin to rise triggering release of FSH and LH FSH and LH stimulate follicle growth and maturation and production of estrogen LH targets thecal cells to produce androstenedione FSH targets granulosa cells to convert androstenedione to estrogens Increasing estrogen levels trigger Continued oocyte and follicle development Growth of new functional layer in the uterus Expression of progesterone receptors on endometrial tissue Negative feedback inhibition of the release of FSH and LH Both are still produced but are stored in the anterior pituitary

1. Follicular Phase Granulosa cells of secondary follicles secrete inhibin Inhibin provides further negative feedback on FSH 2. Ovulation Tertiary follicles are producing peak levels of estrogen which triggers A burst of LH to be release (along with some FSH) Thinning of the cervical mucus LH surge triggers Primary oocyte to complete meiosis I forming the secondary oocyte Ovulation: rupture of secondary oocyte through ovary wall Formation of the corpus luteum form damaged tertiary follicle

3. Luteal Phase The corpus luteum secretes progesterone, estrogen, and inhibin Increasing levels of progesterone trigger glandular secretion in the uterus and thickening of the cervical mucus All three luteum hormones (progesterone, estrogen, inhibin) act to provide negative feedback inhibition on LH, FSH, and GnRH production and release As LH levels decline The corpus luteum beings to degrade forming the corpus albicans Luteum hormone secretion ceases

3. Luteal Phase Declining levels of progesterone and estrogen trigger the initiation of mensus Decreased levels of all three luteum hormones no longer provide negative feedback GnRH levels increase and a new cycle begins

Hormonal Regulation of the Female Reproductive Cycle
Figure 28–26a, b

Figure 28–26c, d

Figure 28–26e, f

Functions of Estrogen Stimulates bone and muscle growth
Maintains female secondary sex characteristics: body hair distribution adipose tissue deposits Stimulate sex drive in CNS - 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

Hormones and Body Temperature
Monthly hormonal fluctuations affect core body temperature: during luteal phase: progesterone dominates during follicular phase: estrogen dominates basal body temperature decreases about 0.3°C

Basal Body Temperature
The resting body temperature Measured upon awakening in morning

Body Temperature and Ovulation
Upon ovulation: basal body temperature declines noticeably Day after ovulation: temperature rises

KEY CONCEPT Cyclic changes in FSH and LH levels maintain ovarian cycle
Hormones produced by ovaries regulate uterine cycle Chance of pregnancy is reduced or eliminated by: inadequate hormone levels inappropriate or inadequate responses to circulating hormones poor coordination and timing of hormone production or secondary oocyte release

Aging and the Reproductive System
1. Menophase Menstruation and ovulation cease due to lack of perimordial follicles 2. Estrogen and progesterone levels decline 3. GnRH, FSH, LH increase 4. Resulting hormone levels result in Reduction of uterus and breast (glands) Osteopenia or osteoporosis Cardiovascular disorders

Why does the level of FSH rise and remain high during menopause?
Because estrogen declines. Because the ovaries no longer respond to FSH. Because LH levels increase. Because GnRH levels increase.

Menopause Is the time that ovulation and menstruation cease
Typically occurs around age 45–55

Premature Menopause Is depletion of follicles before age 40

Andropause Also called male climacteric
Is the period of declining reproductive function Circulating testosterone begins to decline: between ages 50 and 60 Circulating FSH and LH increase

KEY CONCEPT Sex hormones have widespread effects on:
brain development and behavioral drives muscle mass bone mass and density body proportions patterns of hair and fat distribution As aging occurs, reductions in sex hormone levels affect: appearance strength many physiological functions

Hormones of the Reproductive Tract
Table 28–1 (1 of 2)

Hormones of the Reproductive Tract
Table 28–1 (2 of 2)

SUMMARY Gametes Fertilization Gonads: Testes and ovaries
External genitalia Spermatozoa Semen Oocytes Ova Spermatogenesis Spermatozoon Oogenesis

SUMMARY Uterine tubes Uterus Uterine cycle Vagina Mammary glands
Hormones Male sexual function Female sexual function Menopause Male climacteric

Chapter 28: The Reproductive System

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Chapter 28: The Reproductive System

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