Lab 43 - Gametogenesis and the female cycles

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

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

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

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

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

Uterine Wall Three layers 1.Perimetrium: serous layer (visceral peritoneum) 2.Myometrium: interlacing layers of smooth muscle 3.Endometrium: mucosal lining

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

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

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)

Follicular Phase Primordial follicle becomes primary follicle 1.The primordial follicle is activated Squamouslike cells become cuboidal 2.Follicle enlarges to become a primary (1  ) follicle

Figure (1 of 7) Theca folliculi Primary oocyte Zona pellucida Antrum Secondary oocyte Secondary oocyte Corona radiata Primordial follicles 1

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

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

Establishing the Ovarian Cycle 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

Hormonal Interactions During a 28-Day Ovarian Cycle 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

Hormonal Interactions During a 28-Day Ovarian Cycle Days 26–28: corpus luteum degenerates and ovarian hormone levels drop sharply Ends the blockade of FSH and LH The cycle starts anew

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

Figure 27.20a (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. FSH LH

Figure 27.20b (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. Primary follicle Secondary follicle Vesicular follicle Ovulation Corpus luteum Degenerating corpus luteum Follicular phase Ovulation (Day 14) Luteal phase

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

Figure 27.20c (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). Progesterone Estrogens

Figure 27.20d (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. Menstrual phase Menstrual flow Endometrial glands Blood vessels Functional layer Basal layer Proliferative phase Secretory phase Days