The Reproductive System: Part A

The Reproductive System: Part A
27 The Reproductive System: Part A

Primary sex organs (gonads): testes and ovaries
Reproductive System Primary sex organs (gonads): testes and ovaries Produce sex cells (gametes) Secrete steroid sex hormones Androgens (males) Estrogens and progesterone (females) Accessory reproductive organs: ducts, glands, and external genitalia

Sex hormones play roles in
Reproductive System Sex hormones play roles in Development and function of the reproductive organs Sexual behavior and drives Growth and development of many other organs and tissues

Male Reproductive System
Testes (within the scrotum) produce sperm Sperm are delivered to the exterior through a system of ducts Epididymis, ductus deferens, ejaculatory duct, and the urethra

Male Reproductive System
Accessory sex glands: seminal vesicles, prostate, and bulbourethral glands Empty secretions into the ducts during ejaculation

Ureter Urinary bladder Prostatic urethra Peritoneum Seminal vesicle
Membranous urethra Ampulla of ductus deferens Urogenital diaphragm Pubis Ejaculatory duct Corpus cavernosum Rectum Corpus spongiosum Prostate Bulbourethral gland Spongy urethra Epididymis Anus Glans penis Bulb of penis Prepuce Ductus (vas) deferens Testis External urethral orifice Scrotum Figure 27.1

Sac of skin and superficial fascia
The Scrotum Sac of skin and superficial fascia Hangs outside the abdominopelvic cavity Contains paired testes 3C lower than core body temperature (temperature necessary for sperm production)

Temperature is kept constant by two sets of muscles
The Scrotum Temperature is kept constant by two sets of muscles Smooth muscle that wrinkles scrotal skin (dartos muscle) Bands of skeletal muscle that elevate the testes (cremaster muscles)

Urinary bladder Superficial inguinal ring (end of inguinal canal)
Testicular artery Spermatic cord Ductus (vas) deferens Penis Autonomic nerve fibers Middle septum of scrotum Pampiniform venous plexus Cremaster muscle External spermatic fascia Epididymis Tunica vaginalis (from peritoneum) Superficial fascia containing dartos muscle Tunica albuginea of testis Scrotum Internal spermatic fascia Skin Figure 27.2

Each is surrounded by two tunics
The Testes Each is surrounded by two tunics Tunica vaginalis, derived from peritoneum Tunica albuginea, the fibrous capsule Septa divide the testis into 250–300 lobules, each containing 1–4 seminiferous tubules (site of sperm production)

Sperm are conveyed through
The Testes Sperm are conveyed through Seminiferous tubules Tubulus rectus Rete testis Efferent ductules Epididymis

The Testes Blood supply comes from the testicular arteries and testicular veins Spermatic cord encloses nerve fibers, blood vessels, and lymphatics that supply the testes Interstitial (Leydig) cells outside the seminiferous tubules produce androgens

Spermatic cord Blood vessels and nerves Ductus (vas) deferens
Head of epididymis Testis Efferent ductule Seminiferous tubule Rete testis Lobule Straight tubule Septum Tunica albuginea Body of epididymis Tunica vaginalis Duct of epididymis Cavity of tunica vaginalis Tail of epididymis (a) Figure 27.3a

Seminiferous tubule (c) Interstitial cells Spermatogenic
cells in tubule epithelium Areolar connective tissue Myoid cells Sperm Figure 27.3c

The Penis External genitalia are the scrotum and the penis Penis is the male copulatory organ

The Penis Penis consists of
Root and shaft that ends in the glans penis Prepuce, or foreskin—the cuff of loose skin covering the glans Circumcision is the surgical removal of the foreskin Crura The proximal end surrounded by ischiocavernosus muscle; anchors penis to the pubic arch

The Penis Spongy urethra and three cylindrical bodies of erectile tissue (spongy network of connective tissue and smooth muscle with vascular spaces) Corpus spongiosum surrounds the urethra and expands to form the glans and bulb Corpora cavernosa are paired dorsal erectile bodies Erection: erectile tissue fills with blood, causing the penis to enlarge and become rigid

Figure 27.4 Ureter Ampulla of ductus deferens Seminal vesicle
Urinary bladder Ejaculatory duct Prostate Prostatic urethra Orifices of prostatic ducts Bulbourethral gland and duct Membranous urethra Urogenital diaphragm Bulb of penis Root of penis Crus of penis Bulbourethral duct opening Ductus deferens Corpora cavernosa Epididymis Corpus spongiosum Shaft (body) of penis Testis Section of (b) Spongy urethra Glans penis Prepuce (foreskin) (a) External urethral orifice Dorsal vessels and nerves Corpora cavernosa Urethra Skin Tunica albuginea of erectile bodies Deep arteries (b) Corpus spongiosum Figure 27.4

The Male Duct System Epididymis Ductus deferens Ejaculatory duct Urethra

Head: contains the efferent ductules Duct of the epididymis
Microvilli (stereocilia) absorb testicular fluid and pass nutrients to stored sperm Nonmotile sperm enter, pass slowly through, and become motile During ejaculation the epididymis contracts, expelling sperm into the ductus deferens

Ductus Deferens and Ejaculatory Duct
Passes through the inguinal canal Expands to form the ampulla and then joins the duct of the seminal vesicle to form the ejaculatory duct Propels sperm from the epididymis to the urethra Vasectomy: cutting and ligating the ductus deferens, which is a nearly 100% effective form of birth control

Conveys both urine and semen (at different times)
Urethra Conveys both urine and semen (at different times) Has three regions Prostatic urethra Membranous urethra Spongy (penile) urethra

Accessory Glands: Seminal Vesicles
Produces viscous alkaline seminal fluid Fructose, ascorbic acid, coagulating enzyme (vesiculase), and prostaglandins 70% of the volume of semen Duct of seminal vesicle joins the ductus deferens to form the ejaculatory duct

Accessory Glands: Prostate
Encircles part of the urethra inferior to the bladder Secretes milky, slightly acid fluid: Contains citrate, enzymes, and prostate-specific antigen (PSA) Plays a role in the activation of sperm Enters the prostatic urethra during ejaculation

Accessory Glands: Bulbourethral Glands (Cowper’s Glands)
Pea-sized glands inferior to the prostate Prior to ejaculation, produce thick, clear mucus Lubricates the glans penis Neutralizes traces of acidic urine in the urethra

Mixture of sperm and accessory gland secretions
Semen Mixture of sperm and accessory gland secretions Contains nutrients (fructose), protects and activates sperm, and facilitates their movement (e.g., relaxin) Prostaglandins in semen Decrease the viscosity of mucus in the cervix Stimulate reverse peristalsis in the uterus

Semen Alkalinity neutralizes the acid in the male urethra and female vagina Antibiotic chemicals destroy certain bacteria Clotting factors coagulate semen just after ejaculation, then fibrinolysin liquefies it Only 2–5 ml of semen are ejaculated, containing 20–150 million sperm/ml

Male Sexual Response Erection
Enlargement and stiffening of the penis from engorgement of erectile tissue with blood Initiated by sexual stimuli, including: Touch and mechanical stimulation of the penis Erotic sights, sounds, and smells Can be induced or inhibited by emotions or higher mental activity

Male Sexual Response Erection:
Parasympathetic reflex promotes release of nitric oxide (NO) NO causes erectile tissue to fill with blood Expansion of the corpora cavernosa Compresses drainage veins and maintains engorgement Corpus spongiosum keeps the urethra open Impotence: the inability to attain erection

Male Sexual Response Ejaculation
Propulsion of semen from the male duct system Sympathetic spinal reflex causes Ducts and accessory glands to contract and empty their contents Bladder sphincter muscle to constrict, preventing the expulsion of urine Bulbospongiosus muscles to undergo a rapid series of contractions

Most body cells are diploid (2n) and contain
Spermatogenesis Sequence of events that produces sperm in the seminiferous tubules of the testes Most body cells are diploid (2n) and contain Two sets of chromosomes (one maternal, one paternal) 23 pairs of homologous chromosomes Gametes are haploid (n) and contain 23 chromosomes

Gamete formation involves meiosis
Nuclear division in the gonads in which the number of chromosomes is halved (from 2n to n) Two consecutive cell divisions (meiosis I and II) following one round of DNA replication Produces four daughter cells Introduces genetic variation

Figure 27.6 (1 of 2) Interphase cell MEIOSIS I Prophase I
Prophase events occur, as in mitosis. Additionally, synapsis occurs: Homologous chromosomes come together along their length to form tetrads. During synapsis, the “arms” of homologous chromatids wrap around each other, forming several crossovers. The nonsister chromatids trade segments at points of crossover. Crossover is followed through the diagrams below. Nuclear envelope Centromere Crossover Centriole pairs Spindle Sister chromatids Nuclear envelope fragments late in prophase I Chromatin 2n = 4 Interphase events As in mitosis, meiosis is preceded by DNA replication and other preparations for cell division. Metaphase I The tetrads align randomly on the spindle equator in preparation for anaphase. Tetrad Dyad Anaphase I Unlike anaphase of mitosis, the centromeres do not separate during anaphase I of meiosis, so the sister chromatids (dyads) remain firmly attached. However, the homologous chromosomes do separate from each other and the dyads move toward opposite poles of the cell. Chromosomes uncoil Telophase I The nuclear membranes re-form around the chromosomal masses, the spindle breaks down, and the chromatin reappears as telophase and cytokinesis are completed. The 2 daughter cells (now haploid) enter a second interphase-like period, called interkinesis, before meiosis II occurs. There is no second replication of DNA before meiosis II. Nuclear envelopes re-form Cleavage furrow Figure 27.6 (1 of 2)

MEIOSIS II Prophase II Meiosis II begins with the products of meiosis I (2 haploid daughter cells) and undergoes a mitosis-like nuclear division process referred to as the equational division of meiosis. Metaphase II Anaphase II After progressing through the phases of meiosis and cytokinesis, the product is 4 haploid cells, each genetically different from the original mother cell. (During human spermatogenesis, the daughter cells remain interconnected by cytoplasmic extensions during the meiotic phases.) Telophase II and cytokinesis Products of meiosis: haploid daughter cells Figure 27.6 (2 of 2)

Figure 27.5 (1 of 2) Mother cell (before chromosome replication)
MITOSIS MEIOSIS Replicated chromosome Tetrad formed by synapsis of replicated homologous chromosomes Prophase Prophase I Chromosomes align at the metaphase plate Tetrads align at the metaphase plate Metaphase Metaphase I Sister chromatids separate during anaphase Homologous chromosomes separate but sister chromatids remain together during anaphase I Daughter cells of mitosis Daughter cells of meiosis I 2n 2n No further chromosomal replication; sister chromatids separate during anaphase II Meiosis II n n n n Daughter cells of meiosis II (usually gametes) Figure 27.5 (1 of 2)

Figure 27.5 (2 of 2) MITOSIS MEIOSIS Number of divisions
One, consisting of prophase, metaphase, anaphase, and telophase. Two, each consisting of prophase, metaphase, anaphase, and telophase. DNA replication does not occur between the two nuclear divisions. Synapsis of homologous chromosomes Does not occur. Occurs during mitosis I; tetrads formed, allowing crossovers. Daughter cell number and genetic composition Two. Each diploid (2n) cell is identical to the mother cell. Four. Each haploid (n) cell contains half as many chromosomes as the mother cell and is genetically different from the mother cell. Roles in the body For development of multicellular adult from zygote. Produces cells for growth and tissue repair. Ensures constancy of genetic makeup of all body cells. Produces cells for reproduction (gametes). Introduces genetic variability in the gametes and reduces chromosomal number by half so that when fertilization occurs, the normal diploid chromosomal number is restored (in humans, 2n = 46). Figure 27.5 (2 of 2)

Spermatic cells give rise to sperm
Spermatogenesis Spermatic cells give rise to sperm Mitosis Spermatogonia form spermatocytes Meiosis Spermatocytes form spermatids Spermiogenesis Spermatids become sperm

Figure 27.7a

Spermatogonium (stem cell) Cytoplasm of adjacent sustentacular cells Sustentacular cell nucleus Basal lamina Type A daughter cell remains at basal lamina as a stem cell Type B daughter cell Tight junction between sustentacular cells Primary spermatocyte Secondary spermatocytes Early spermatids Late spermatids Cytoplasmic bridge Spermatozoa Lumen of seminiferous tubule (c) A portion of the seminiferous tublule wall, showing the spermatogenic cells surrounded by sustentacular cells (colored gold) Figure 27.7c

Mitosis of Spermatogonia
Begins at puberty Spermatogonia Stem cells in contact with the epithelial basal lamina Each mitotic division  a type A daughter cell and a type B daughter cell

Mitosis of Spermatogonia
Type A cells maintain the germ cell line at the basal lamina Type B cells move toward the lumen and develop into primary spermatocytes

Meiosis: Spermatocytes to Spermatids
Meiosis I Primary spermatocyte (2n)  two secondary spermatocytes (n) Meiosis II Each secondary spermatocyte (n)  two spermatids (n) Spermatid: small nonmotile cells close to the lumen of the tubule

Basal lamina Spermatogonium (stem cell) Type A daughter cell remains at basal lamina as a stem cell Mitosis Type B daughter cell Growth Enters meiosis I and moves to adluminal compartment Primary spermatocyte Meiosis I completed Secondary spermatocytes Meiosis II Early spermatids Late spermatids Spermatozoa (b) Events of spermatogenesis, showing the relative position of various spermatogenic cells Figure 27.7b

Spermiogenesis: Spermatids to Sperm
Spermatids lose excess cytoplasm and form a tail, becoming spermatozoa (sperm)

Sperm Major regions Head: genetic region; nucleus and helmetlike acrosome containing hydrolytic enzymes that enable the sperm to penetrate an egg Midpiece: metabolic region; mitochondria Tail: locomotor region; flagellum

Golgi apparatus Acrosomal vesicle
Approximately 24 days Golgi apparatus Acrosomal vesicle Mitochondria Acrosome Nucleus 1 2 Centrioles Spermatid nucleus Microtubules Midpiece Head (a) 3 Flagellum Excess cytoplasm 4 Tail 5 6 7 (b) Figure 27.8a, b

Role of Sustentacular Cells
Large supporting cells (Sertoli cells) Extend through the wall of the tubule and surround developing cells Provide nutrients and signals to dividing cells Dispose of excess cytoplasm sloughed off during spermiogenesis Secrete testicular fluid into lumen for transport of sperm

Tight junctions divide the wall into two compartments Basal compartment—spermatogonia and primary spermatocytes Adluminal compartment—meiotically active cells and the tubule lumen

Spermatogonium (stem cell) Cytoplasm of adjacent sustentacular cells Sustentacular cell nucleus Basal lamina Type A daughter cell remains at basal lamina as a stem cell Type B daughter cell Tight junction between sustentacular cells Primary spermatocyte Secondary spermatocytes Early spermatids Late spermatids Cytoplasmic bridge Spermatozoa Lumen of seminiferous tubule (c) A portion of the seminiferous tublule wall, showing the spermatogenic cells surrounded by sustentacular cells (colored gold) Figure 27.7c

Tight junctions form a blood-testis barrier Prevents sperm antigens from escaping into the blood where they would activate the immune system Because sperm are not formed until puberty, they are absent during immune system development, and would not be recognized as “self”

Hormonal Regulation of Male Reproductive Function
A sequence of hormonal regulatory events involving the hypothalamus, anterior pituitary gland, and the testes The hypothalamic-pituitary-gonadal (HPG) axis

HPG Axis Hypothalamus releases gonadotropin-releasing hormone (GnRH) GnRH stimulates the anterior pituitary to secrete FSH and LH FSH causes sustentacular cells to release androgen-binding protein (ABP), which makes spermatogenic cell receptive to testosterone LH stimulates interstitial cells to release testosterone

Testosterone is the final trigger for spermatogenesis
HPG Axis Testosterone is the final trigger for spermatogenesis Feedback inhibition on the hypothalamus and pituitary results from Rising levels of testosterone Inhibin (released when sperm count is high)

GnRH Anterior Via portal pituitary blood Inhibin FSH LH Interstitial
1 GnRH Anterior pituitary Via portal blood 8 7 2 Inhibin 2 FSH LH Interstitial cells 3 4 6 Testosterone Somatic and psychological effects at other body sites Sustentacular cell Spermatogenic cells 5 Seminiferous tubule Stimulates Inhibits Figure 27.9

Mechanism and Effects of Testosterone Activity
Synthesized from cholesterol Transformed to exert its effects on some target cells Dihydrotestosterone (DHT) in the prostate Estrogen in some neurons in the brain

Mechanism and Effects of Testosterone Activity
Prompts spermatogenesis Targets all accessory organs; deficiency leads to atrophy Has multiple anabolic effects throughout the body Is the basis of the sex drive (libido) in males

Male Secondary Sex Characteristics
Features induced in the nonreproductive organs by male sex hormones (mainly testosterone) Appearance of pubic, axillary, and facial hair Enhanced growth of the chest and deepening of the voice Skin thickens and becomes oily Bones grow and increase in density Skeletal muscles increase in size and mass

Female Reproductive Anatomy
Ovaries: female gonads Produce female gametes (ova) Secrete female sex hormones (estrogen and progesterone) Accessory ducts include Uterine tubes Uterus Vagina

Female Reproductive Anatomy
Internal genitalia Ovaries Uterine tubes Uterus Vagina External genitalia The external sex organs

Suspensory ligament of ovary Infundibulum Uterine tube Ovary Fimbriae
Peritoneum Uterus Uterosacral ligament Round ligament Vesicouterine pouch Perimetrium Rectouterine pouch Urinary bladder Pubic symphysis Rectum Mons pubis Posterior fornix Cervix Urethra Anterior fornix Clitoris Vagina External urethral orifice Anus Hymen Urogenital diaphragm Labium minus Greater vestibular (Bartholin’s) gland Labium majus Figure 27.10

Held in place by several ligaments
Ovaries Held in place by several ligaments Ovarian ligament: anchors ovary medially to the uterus Suspensory ligament: anchors ovary laterally to the pelvic wall Mesovarium: suspends the ovary Broad ligament: supports the uterine tubes, uterus, and vagina; also contains the suspensory ligament and the mesovarium

Uterine (fallopian) tube Uterine tube Ovarian blood vessels Fundus
Suspensory ligament of ovary Uterine (fallopian) tube Uterine tube Ovarian blood vessels Fundus of uterus Lumen (cavity) of uterus Ampulla Mesosalpinx Ovary Isthmus Mesovarium Infundibulum Broad ligament Fimbriae Mesometrium Round ligament of uterus Ovarian ligament Endometrium Body of uterus Myometrium Wall of uterus Ureter Uterine blood vessels Perimetrium Isthmus Internal os Uterosacral ligament Cervical canal Lateral cervical (cardinal) ligament External os Vagina Lateral fornix Cervix (a) Figure 27.12a

Surrounded by a fibrous tunica albuginea Two poorly defined regions
Ovaries Blood supply: ovarian arteries and the ovarian branch of the uterine artery Surrounded by a fibrous tunica albuginea Two poorly defined regions Cortex: ovarian follicles Medulla: large blood vessels and nerves

Ovaries Follicle Immature egg (oocyte) surrounded by
Follicle cells (one cell layer thick) Granulosa cells (when more than one layer is present)

Several stages of development
Follicles Several stages of development Primordial follicle: squamouslike follicle cells + oocyte Primary follicle: cuboidal or columnar follicle cells + oocyte Secondary follicle: two or more layers of granulosa cells + oocyte Late secondary follicle: contains fluid-filled space between granulosa cells; coalesces to form a central antrum

Vesicular (Graafian) follicle
Ovaries Vesicular (Graafian) follicle Fluid-filled antrum forms; follicle bulges from ovary surface Ovulation Ejection of the oocyte from the ripening follicle Corpus luteum develops from ruptured follicle after ovulation

Late secondary follicle Degenerating corpus luteum (corpus albicans)
Tunica albuginea Oocyte Granulosa cells Late secondary follicle Degenerating corpus luteum (corpus albicans) Cortex Mesovarium and blood vessels Germinal epithelium Vesicular (Graafian) follicle Primary follicles Antrum Oocyte Ovarian ligament Zona pellucida Theca folliculi Medulla Ovulated oocyte Corpus luteum Developing corpus luteum Corona radiata (a) Diagrammatic view of an ovary sectioned to reveal the follicles in its interior Figure 27.11a

Female Duct System Uterine (fallopian) tubes or oviducts Uterus Vagina

Isthmus: constricted region where tube joins uterus
Uterine Tubes Ampulla Distal expansion with infundibulum near ovary Usual site of fertilization Ciliated fibriae of infundibulum create currents to move oocyte into uterine tube Isthmus: constricted region where tube joins uterus

Uterine Tubes Oocyte is carried along by peristalsis and ciliary action Nonciliated cells nourish the oocyte and the sperm Mesosalpinx: mesentery that supports the uterine tubes

Uterus Body: major portion Fundus: rounded superior region Isthmus: narrowed inferior region

Cervix: narrow neck, or outlet; projects into the vagina
Uterus Cervix: narrow neck, or outlet; projects into the vagina Cervical canal communicates with the Vagina via the external os Uterine body via the internal os Cervical glands secrete mucus that blocks sperm entry except during midcycle

Supports of the Uterus Mesometrium—lateral support: portion of the broad ligament Lateral cervical (cardinal) ligaments: from the cervix and superior part of the vagina to the walls of the pelvis Uterosacral ligaments secure uterus to the sacrum Round ligaments bind to the anterior wall

Sacs of peritoneum exist around the uterus
Peritoneal Pouches Sacs of peritoneum exist around the uterus Vesicouterine pouch is between bladder and uterus Rectouterine pouch is between rectum and uterus

Uterine Wall Three layers
Perimetrium: serous layer (visceral peritoneum) Myometrium: interlacing layers of smooth muscle Endometrium: mucosal lining

Stratum functionalis (functional layer)
Endometrium Stratum functionalis (functional layer) Changes in response to ovarian hormone cycles Is shed during menstruation Stratum basalis (basal layer) Forms new functionalis after menstruation Unresponsive to ovarian hormones

Uterine Vascular Supply
Uterine arteries: arise from internal iliacs Arcuate arteries: in the myometrium Radial branches in the endometrium branch into Spiral arteries  stratum functionalis Straight arteries  stratum basalis Spasms of spiral arteries leads to shedding of stratum functionalis

Spiral (coiled) artery
Lumen of uterus Epithelium Capillaries Uterine glands Venous sinusoids Lamina propria of connective tissue Spiral (coiled) artery Straight artery Endometrial vein Smooth muscle fibers Radial artery Arcuate artery Uterine artery (b) Figure 27.13b

Vagina Birth canal and organ of copulation Extends between the bladder and the rectum from the cervix to the exterior Urethra embedded in the anterior wall

Vaginal fornix: upper end of the vagina surrounding the cervix
Layers of wall Fibroelastic adventitia Smooth muscle muscularis Stratified squamous mucosa with rugae Mucosa near the vaginal orifice forms an incomplete partition called the hymen Vaginal fornix: upper end of the vagina surrounding the cervix

Mons pubis Labia Prepuce majora of clitoris Labia minora Clitoris
(glans) Urethral orifice Vestibule Hymen (ruptured) Vaginal orifice Anus Opening of the duct of the greater vestibular gland (a) Figure 27.14a

External Genitalia (Vulva or Pudendum)
Mons pubis: fatty area overlying pubic symphysis Labia majora: hair-covered, fatty skin folds Labia minora: skin folds lying within labia majora Vestibule: recess between labia minora

Greater vestibular glands
External Genitalia Greater vestibular glands Homologous to the bulbourethral glands Release mucus into the vestibule for lubrication

External Genitalia Clitoris Perineum
Erectile tissue hooded by a prepuce Glans clitoris: exposed portion Perineum Diamond-shaped region between the pubic arch and coccyx Bordered by the ischial tuberosities laterally

Inferior ramus of pubis
Clitoris Labia minora Labia majora Inferior ramus of pubis Pubic symphysis Anus Body of clitoris, containing corpora cavernosa Clitoris (glans) Crus of clitoris Urethral orifice Vaginal orifice Greater vestibular gland Bulb of vestibule (b) Fourchette Figure 27.14b

Mammary Glands Modified sweat glands consisting of 15–25 lobes Areola: pigmented skin surrounding the nipple Suspensory ligaments: attach the breast to underlying muscle Lobules within lobes contain glandular alveoli that produce milk

Mammary Glands Milk  lactiferous ducts  lactiferous sinuses  open to the outside at the nipple

Pectoralis major muscle Suspensory ligament
First rib Skin (cut) Pectoralis major muscle Suspensory ligament Adipose tissue Lobe Areola Nipple Opening of lactiferous duct Lactiferous sinus Lactiferous duct Lobule containing alveoli Hypodermis (superficial fascia) Intercostal muscles (a) (b) Figure 27.15

Usually arises from the epithelial cells of small ducts
Breast Cancer Usually arises from the epithelial cells of small ducts Risk factors include: Early onset of menstruation and late menopause No pregnancies or first pregnancy late in life Family history of breast cancer 10-20% are due to hereditary defects, including mutations to the genes BRCA1 and BRCA2

Breast Cancer: Detection and Treatment
70% of women with breast cancer have no known risk factors Early detection via self-examination and mammography Treatment depends upon the characteristics of the lesion: Radiation, chemotherapy, and surgery followed by irradiation and chemotherapy

(a) Mammogram procedure
Malignancy (b) Film of normal breast (c) Film of breast with tumor Figure 27.16

Production of female gametes Begins in the fetal period
Oogenesis Production of female gametes Begins in the fetal period Oogonia (2n ovarian stem cells) multiply by mitosis and store nutrients Primary oocytes develop in primordial follicles Primary oocytes begin meiosis but stall in prophase I

Each month after puberty, a few primary oocytes are activated
Oogenesis Each month after puberty, a few primary oocytes are activated One is selected each month to resume meiosis I Result is two haploid cells Secondary oocyte First polar body

The secondary oocyte arrests in metaphase II and is ovulated
Oogenesis The secondary oocyte arrests in metaphase II and is ovulated If penetrated by sperm the second oocyte completes meiosis II, yielding Ovum (the functional gamete) Second polar body

Figure 27.17 Meiotic events Follicle development in ovary Before birth
Oogonium (stem cell) Follicle cells Mitosis Oocyte Primary oocyte Primordial follicle Growth Infancy and childhood (ovary inactive) Primary oocyte (arrested in prophase I; present at birth) Primordial follicle Each month from puberty to menopause Primary follicle Primary oocyte (still arrested in prophase I) Secondary follicle Spindle Vesicular (Graafian) follicle Meiosis I (completed by one primary oocyte each month in response to LH surge) Secondary oocyte (arrested in metaphase II) First polar body Ovulation Meiosis II of polar body (may or may not occur) Sperm Ovulated secondary oocyte Meiosis II completed (only if sperm penetration occurs) In absence of fertilization, ruptured follicle becomes a corpus luteum and ultimately degenerates. Polar bodies (all polar bodies degenerate) Second polar body Ovum Degenating corpus luteum Figure 27.17

Monthly series of events associated with the maturation of an egg
Ovarian Cycle Monthly series of events associated with the maturation of an egg Two consecutive phases (in a 28-day cycle) Follicular phase: period of follicle growth (days 1–14) Ovulation occurs midcycle Luteal phase: period of corpus luteum activity (days 14–28)

Primordial follicle becomes primary follicle
Follicular Phase Primordial follicle becomes primary follicle The primordial follicle is activated Squamouslike cells become cuboidal Follicle enlarges to become a primary (1) follicle

Primordial follicles 1 Theca folliculi Primary oocyte Zona pellucida
3 4 2 Primary oocyte 1 Zona pellucida Antrum Secondary oocyte 5 1 Primordial follicles 8 6 Secondary oocyte 7 Corona radiata Figure (1 of 7)

Primary follicle 2 Theca folliculi Primary oocyte Zona pellucida
3 4 2 Primary oocyte 1 Zona pellucida Antrum Secondary oocyte 5 Primary follicle 2 8 6 Secondary oocyte Corona radiata 7 Figure (2 of 7)

Follicular Phase Primary follicle becomes a secondary follicle
Stratified epithelium (granulosa cells) forms around oocyte Granulosa cells and oocyte guide one another’s development

Follicular Phase Secondary follicle becomes a late secondary follicle
Connective tissue (theca folliculi) and granulosa cells cooperate to produce estrogens Zona pellucida forms around the oocyte Fluid begins to accumulate

Secondary follicle 3 Theca folliculi Primary oocyte Zona pellucida
4 2 Primary oocyte 1 Zona pellucida Antrum Secondary oocyte 5 3 Secondary follicle 8 6 Secondary oocyte 7 Corona radiata Figure (3 of 7)

Theca folliculi Primary oocyte Zona pellucida Antrum Secondary oocyte
3 4 2 Primary oocyte 1 Zona pellucida Antrum Secondary oocyte 5 8 6 Secondary oocyte 4 Late secondary follicle 7 Corona radiata Figure (4 of 7)

Follicular Phase Late secondary follicle becomes a vesicular follicle
Antrum forms and expands to isolate the oocyte with its corona radiata on a stalk Vesicular follicle bulges from the external surface of the ovary The primary oocyte completes meiosis I

Ovulation Ovary wall ruptures and expels the secondary oocyte with its corona radiata Mittelschmerz: twinge of pain sometimes felt at ovulation 1–2% of ovulations release more than one secondary oocyte, which, if fertilized, results in fraternal twins

Theca folliculi Primary oocyte Zona pellucida Antrum Secondary oocyte
3 4 2 Primary oocyte 1 Zona pellucida Antrum Secondary oocyte Mature vesicular follicle carries out meiosis I; ready to be ovulated 5 5 8 6 Secondary oocyte Corona radiata 7 Figure (5 of 7)

Follicle ruptures; secondary oocyte ovulated Theca folliculi
3 4 2 Primary oocyte 1 Zona pellucida Antrum Secondary oocyte 5 6 Follicle ruptures; secondary oocyte ovulated 8 6 Secondary oocyte 7 Corona radiata Figure (6 of 7)

Luteal Phase Ruptured follicle collapses Granulosa cells and internal thecal cells form corpus luteum Corpus luteum secretes progesterone and estrogen

Luteal Phase If no pregnancy, the corpus luteum degenerates into a corpus albicans in 10 days If pregnancy occurs, corpus luteum produces hormones until the placenta takes over at about 3 months

Corpus luteum (forms from ruptured follicle) Theca folliculi
3 4 2 Primary oocyte 1 Zona pellucida Antrum Secondary oocyte 5 7 Corpus luteum (forms from ruptured follicle) 8 6 Secondary oocyte 7 Corona radiata Figure (7 of 7)

Establishing the Ovarian Cycle
During childhood, ovaries grow and secrete small amounts of estrogens that inhibit the hypothalamic release of GnRH As puberty nears, GnRH is released; FSH and LH are released by the pituitary, and act on the ovaries These events continue until an adult cyclic pattern is achieved and menarche occurs

During childhood, until puberty Ovaries secrete small amounts of estrogens Estrogen inhibits release of GnRH

At puberty Leptin from adipose tissue decreases the estrogen inhibition GnRH, FSH, and LH are released In about four years, an adult cyclic pattern is achieved and menarche occurs

Hormonal Interactions During a 28-Day Ovarian Cycle
Day 1: GnRH  release of FSH and LH FSH and LH  growth of several follicles, and estrogen release  estrogen levels Inhibit the release of FSH and LH Stimulate synthesis and storage of FSH and LH Enhance further estrogen output

Estrogen output by the vesicular follicle increases High estrogen levels have a positive feedback effect on the pituitary at midcycle Sudden LH surge at day 14

Effects of LH surge Completion of meiosis I (secondary oocyte continues on to metaphase II) Triggers ovulation Transforms ruptured follicle into corpus luteum

Functions of corpus luteum Produces inhibin, progesterone, and estrogen These hormones inhibit FSH and LH release Declining LH and FSH ends luteal activity and inhibits follicle development

Days 26–28: corpus luteum degenerates and ovarian hormone levels drop sharply Ends the blockade of FSH and LH The cycle starts anew

Early and midfollicular phases
Hypothalamus Hypothalamus 5 GnRH Positive feedback exerted by large in estrogen output. 4 8 Travels via portal blood 1 Anterior pituitary 1 5 Progesterone Estrogen Inhibin LH surge FSH LH Ruptured follicle 6 2 2 8 Slightly elevated estrogen and rising inhibin levels. 3 7 Thecal cells Granulosa cells Androgens Corpus luteum Mature follicle Ovulated secondary oocyte Convert androgens to estrogens Inhibin 2 Late follicular and luteal phases Early and midfollicular phases Figure 27.19

(a) Fluctuation of gonadotropin levels: Fluctuating
LH FSH (a) Fluctuation of gonadotropin levels: Fluctuating levels of pituitary gonadotropins (follicle-stimulating hormone and luteinizing hormone) in the blood regulate the events of the ovarian cycle. Figure 27.20a

(b) Ovarian cycle: Structural changes in the ovarian
Primary follicle Vesicular follicle Corpus luteum Degenerating corpus luteum Secondary follicle Ovulation Follicular phase Ovulation (Day 14) Luteal phase (b) Ovarian cycle: Structural changes in the ovarian follicles during the ovarian cycle are correlated with (d) changes in the endometrium of the uterus during the uterine cycle. Figure 27.20b

Uterine (Menstrual) Cycle
Cyclic changes in endometrium in response to ovarian hormones Three phases Days 1–5: menstrual phase Days 6–14: proliferative (preovulatory) phase Days 15–28: secretory (postovulatory) phase (constant 14-day length)

Uterine Cycle Menstrual phase
Ovarian hormones are at their lowest levels Gonadotropins are beginning to rise Stratum functionalis is shed and the menstrual flow occurs

Uterine Cycle Proliferative phase
Estrogen levels prompt generation of new functional layer and increased synthesis of progesterone receptors in endometrium Glands enlarge and spiral arteries increase in number

Uterine Cycle Secretory phase Progesterone levels prompt
Further development of endometrium Glandular secretion of glycogen Formation of the cervical mucus plug

(c) Fluctuation of ovarian hormone levels:
Estrogens Progesterone (c) Fluctuation of ovarian hormone levels: Fluctuating levels of ovarian hormones (estrogens and progesterone) cause the endometrial changes of the uterine cycle. The high estrogen levels are also responsible for the LH/FSH surge in (a). Figure 27.20c

(d) The three phases of the uterine cycle:
Endometrial glands Blood vessels Menstrual flow Functional layer Basal layer Days Menstrual phase Proliferative phase Secretory phase (d) The three phases of the uterine cycle: • Menstrual: Shedding of the functional layer of the endometrium. • Proliferative: Rebuilding of the functional layer of the endometrium. • Secretory: Begins immediately after ovulation. Enrichment of the blood supply and glandular secretion of nutrients prepare the endometrium to receive an embryo. Both the menstrual and proliferative phases occur before ovulation, and together they correspond to the follicular phase of the ovarian cycle. The secretory phase corresponds in time to the luteal phase of the ovarian cycle. Figure 27.20d

If fertilization does not occur
Uterine Cycle If fertilization does not occur Corpus luteum degenerates Progesterone levels fall Spiral arteries kink and spasm Endometrial cells begin to die Spiral arteries constrict again, then relax and open wide Rush of blood fragments weakened capillary beds and the functional layer sloughs

Effects of Estrogens Promote oogenesis and follicle growth in the ovary Exert anabolic effects on the female reproductive tract Support the rapid but short-lived growth spurt at puberty

Induce secondary sex characteristics
Effects of Estrogens Induce secondary sex characteristics Growth of the breasts Increased deposit of subcutaneous fat (hips and breasts) Widening and lightening of the pelvis Metabolic effects Maintain low total blood cholesterol and high HDL levels Facilitates calcium uptake

Effects of Progesterone
Progesterone works with estrogen to establish and regulate the uterine cycle Effects of placental progesterone during pregnancy Inhibits uterine motility Helps prepare the breasts for lactation

Female Sexual Response
Initiated by touch and psychological stimuli The clitoris, vaginal mucosa, and breasts engorge with blood Vestibular gland secretions lubricate the vestibule Orgasm is accompanied by muscle tension, increase in pulse rate and blood pressure, and rhythmic contractions of the uterus

Female Sexual Response
Females do not have a refractory period after orgasm and can experience multiple orgasms in a single sexual experience Orgasm is not essential for conception

Sexually Transmitted Infections (STIs)
Also called sexually transmitted diseases (STDs) or venereal diseases (VDs) The single most important cause of reproductive disorders

Gonorrhea Bacterial infection of mucosae of reproductive and urinary tracts Spread by contact with genital, anal, and pharyngeal mucosae

Gonorrhea Signs and symptoms
Males Urethritis, painful urination, discharge of pus Females 20% display no signs or symptoms Abdominal discomfort, vaginal discharge, or abnormal uterine bleeding Can result in pelvic inflammatory disease and sterility Treatment: antibiotics, but resistant strains are becoming prevalent

Bacterial infection transmitted sexually or contracted congenitally
Syphilis Bacterial infection transmitted sexually or contracted congenitally Infected fetuses are stillborn or die shortly after birth Infection is asymptomatic for 2–3 weeks A painless chancre appears at the site of infection and disappears in a few weeks

Syphilis If untreated, secondary signs appear several weeks later for 3–12 weeks, and then disappear: pink skin rash, fever, and joint pain The latent period may or may not progress to tertiary syphilis, characterized by gummas (lesions of the CNS, blood vessels, bones, and skin) Treatment: penicillin

Chlamydia Most common bacterial STI in the United States
Responsible for 25–50% of all diagnosed cases of pelvic inflammatory disease Symptoms: urethritis; penile and vaginal discharges; abdominal, rectal, or testicular pain; painful intercourse; irregular menses Can cause arthritis and urinary tract infections in men, and sterility in women Treatment: tetracycline

Viral Infections Genital warts Caused by human papillomavirus (HPV)
Second most common STI in the United States Increase the risk of cancers in infected body regions

Caused by human herpes virus type 2
Viral Infections Genital herpes Caused by human herpes virus type 2 Characterized by latent periods and flare-ups Congenital herpes can cause malformations of a fetus Treatment: acyclovir and other antiviral drugs

Developmental Aspects: Determination of Genetic Sex
One of the 23 pairs of chromosomes in body cells are sex chromosomes: X and Y Females are XX and each egg has an X chromosome Males are XY, so ~50% of sperm contain X, ~50% contain Y

Developmental Aspects: Determination of Genetic Sex
X egg + X sperm  XX (female offspring) X egg + Y sperm  XY (male offspring) The SRY gene on the Y chromosome initiates testes development and maleness

Developmental Aspects: Sexual Differentiation
Sexually indifferent stage Gonads begin development in fifth week as gonadal ridges Paramesonephric (Müllerian) ducts (future female ducts) form lateral to the mesonephric (Wolffian) ducts (future male ducts) Primordial germ cells migrate to the gonadal ridges to provide germ cells destined to become spermatogonia or oogonia Gonads begin development in seventh week in males, eighth week in females

sexually indifferent stage
Mesonephros Mesonephric (Wolffian) duct Gonadal ridge Paramesonephric (Müllerian) duct Metanephros (kidney) Cloaca 5- to 6-week embryo: sexually indifferent stage Figure (1 of 5)

Testes Efferent ductules Epididymis Paramesonephric
duct (degenerating) Mesonephric duct forming the ductus deferens Urinary bladder Seminal vesicle Urogenital sinus forming the urethra 7- to 8-week male embryo Figure (2 of 5)

Ovaries Paramesonephric duct forming the uterine tube Mesonephric duct
(degenerating) Fused paramesonephric ducts forming the uterus Urinary bladder (moved aside) Urogenital sinus forming the urethra and lower vagina 8- to 9-week female fetus Figure (3 of 5)

Developmental Aspects: Development of External Genitalia
Genital tubercle  penis of male; clitoris of female Urethral fold  urethra of male; labia minora of female Labioscrotal folds  scrotum of male: labia majora of female

Genital tubercle Urethral fold Labioscrotal Anus swelling Tail (cut)
Urethral groove (a) Indifferent Figure 27.22a

Approximately 5 weeks Glans penis Labioscrotal Urethral swellings
(scrotum) Urethral folds Anus Glans penis Penis Scrotum Anus (b) Male development Figure 27.22b

Genital tubercle Urethral fold Labioscrotal Anus swelling Tail (cut)
Urethral groove (a) Indifferent Figure 27.22a

(c) Female development
Approximately 5 weeks Glans clitoris Urogenital sinus Labioscrotal swellings (labia majora) Urethral folds (labia minora) Anus Glans clitoris Labia majora Labia minora Anus (c) Female development Figure 27.22c

Development Aspects: Descent of the Gonads
About two months before birth Testosterone stimulates the migration of the testes toward the scrotum Ovaries also descend, but are stopped by the broad ligament at the pelvic brim Gubernaculum: fibrous cord from each testis to the scrotum or from ovary to labium majus; guides the descent

At birth: male development
Urinary bladder Seminal vesicle Prostate Bulbourethral gland Ductus deferens Urethra Efferent ductules Epididymis Testis Penis At birth: male development Figure (4 of 5)

At birth: Female development
Uterine tube Ovary Uterus Urinary bladder (moved aside) Vagina Urethra Hymen Vestibule At birth: Female development Figure (5 of 5)

Development Aspects: Puberty
In response to rising levels of gonadal hormones Reproductive organs grow to adult size and become functional Secondary sex characteristics appear Earliest time that reproduction is possible

Menopause Has occurred when menses have ceased for an entire year There is no equivalent to menopause in males

Declining estrogen levels 
Menopause Declining estrogen levels  Atrophy of reproductive organs and breasts Irritability and depression in some Hot flashes as skin blood vessels undergo intense vasodilation Gradual thinning of the skin and bone loss Increased total blood cholesterol levels and falling HDL

The Reproductive System: Part A

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The Reproductive System: Part A

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