The Reproductive System: Part B 27 The Reproductive System: Part B

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

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

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

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

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% 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 27.18 (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 27.18 (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 27.18 (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 27.18 (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 27.18 (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 27.18 (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 27.18 (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