The Reproductive System: Part B

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

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

Ovaries Blood supply: ovarian arteries and the ovarian branch of the uterine artery Surrounded by a fibrous tunica albuginea

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 cavity

Ovaries Vesicular (Graafian) follicle Ovulation
Fluid-filled cavity forms; follicle bulges from ovary surface Ovulation Ejection of the oocyte from the ripening follicle Corpus luteum (‘Yellow body’) develops from ruptured follicle after ovulation (that acts as endocrine gland producing estrogen and progesterone; becomes corpus albicans, scar tissue)

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 fimbriae 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

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

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

(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)

STOP 5/6

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

(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 Growth of the breasts Increased deposit of subcutaneous fat (hips and breasts) Widening and lightening of the pelvis

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

External Genitalia (Vulva or Pudendum)
Mons pubis: fatty area overlying pubic symphysis Labia majora: exterior fatty skin folds Labia minora: interior 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 Erectile tissue hooded by a prepuce
Glans clitoris: exposed portion

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

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

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

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

Stop for day 2

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 (Gonadotropin Releasing Hormone) As puberty nears, GnRH is released; FSH (Follice Stimulating Hormone) and LH (Luteinizing Hormone) are released by the pituitary, and act on the ovaries These events continue until an adult cyclic pattern is achieved and menarche occurs

The Reproductive System: Part B

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