Female Reproductive System PDF

THE FEMALE REPRODUCTIVE SYSTEM Zona Pellucida: A layer between the oocyte and granulosa cells, containing glycoproteins (ZP3, ZP4) critical for sperm...

THE FEMALE REPRODUCTIVE SYSTEM Zona Pellucida: A layer between the oocyte and granulosa cells, containing glycoproteins (ZP3, ZP4) critical for sperm recognition and acrosomal activation. Female Reproductive System Overview Theca Cells Components: Paired ovaries, oviducts (uterine tubes), uterus, vagina, external genitalia. Theca Interna: Vascularized endocrine tissue that produces Functions: androstenedione, a precursor to estrogen. ○ Produces female gametes (oocytes). Theca Externa: Fibrous layer containing fibroblasts and ○ Provides environment for fertilization. smooth muscle. ○ Houses the embryo during fetal development. Hormonal Control: Ovaries produce steroidal sex hormones Follicular Fluid (estrogen, progesterone) that regulate the reproductive system and affect other organs. Composition: Includes hyaluronic acid, growth factors, Menstrual Cycle: plasminogen, heparan sulfate proteoglycan, and steroids ○ Begins at menarche (first menstruation). (progesterone, estrogens, androstenedione). ○ Cyclic changes occur monthly, regulated by neurohormonal mechanisms. ○ Menopause marks the end of cyclic changes and Follicular Atresia leads to organ involution. Mammary Glands: Though not part of the genital system, Process: Most follicles undergo degeneration (atresia) at their function is influenced by reproductive organs. various stages of development, including near maturity. ○ Granulosa cells and oocytes undergo apoptosis, and macrophages phagocytose the debris. Ovaries ○ Atresia leads to the loss of follicles throughout a woman's reproductive life. Structure: ○ At menopause, ovarian reserve is reduced to ○ Almond-shaped, ~3 cm long, 1.5 cm wide, 1 cm fewer than ~1,000 follicles. thick. ○ Covered by simple cuboidal epithelium (germinal epithelium) and a connective tissue capsule Ovulation Cycle (tunica albuginea). ○ Divided into cortex (outer region) and medulla Dominant Follicle: Each menstrual cycle, one follicle (inner region). becomes dominant and continues developing, while others Function: Produce oocytes and steroidal sex hormones. undergo atresia. Development: Hormonal Effects: Growing follicles produce estrogen, ○ Primordial germ cells migrate to the gonads and preparing the reproductive tract for potential embryo support differentiate into oogonia. if fertilization occurs. ○ Oogonia proliferate and reach ~600,000 by 2 months gestation. Ovulation & Hormonal Regulation ○ Oogonia undergo mitosis, meiosis, and apoptosis, resulting in ~7 million oocytes by the fifth month of Ovulation: gestation. ○ Ovulation is the hormone-driven process where ○ At birth, ~2-2.5 million oocytes are present; the oocyte (egg) is released from the ovary. ~400,000 remain at puberty. ○ Typically occurs around the 14th day of a 28-day ○ Around 450 oocytes are ovulated during a menstrual cycle. woman's reproductive life. ○ Only one oocyte is usually released per cycle, though sometimes none or multiple may be Ovarian Follicles expelled. Oocyte Development: Structure: ○ The oocyte completes the first meiotic division 1. Oocyte surrounded by one or more layers of just before ovulation, producing: epithelial cells within a basal lamina. A secondary oocyte. 2. Primordial follicles (formed during fetal life) consist A first polar body (nonviable). of a primary oocyte and a single layer of flattened ○ The oocyte enters the second meiotic division follicular cells. but arrests at metaphase unless fertilization Development Stages: occurs. 1. Primordial Follicle: Primary oocyte with flattened Hormonal Regulation of Ovulation: follicular cells. ○ FSH (Follicle-Stimulating Hormone) from the 2. Primary Follicle: Follicular cells proliferate to form anterior pituitary stimulates follicular growth. a unilaminar (single layer) epithelium. ○ GnRH (Gonadotropin-Releasing Hormone) from 3. Secondary (Antral) Follicle: Granulosa cells form the hypothalamus stimulates FSH release. multiple layers, and fluid-filled spaces accumulate, ○ Estrogen produced by granulosa cells of the forming an antrum. follicle: 4. Mature (Graafian) Follicle: Large antrum with a Stimulates more pulsatile release of cumulus oophorus, corona radiata, and a fully GnRH. developed oocyte.  Triggers a surge in LH (Luteinizing Wall of the Oviduct: Hormone) from the pituitary, leading to ovulation. Layers: ○ Inhibin (produced by granulosa and luteal cells) 1. Mucosa: Folded, lined by simple columnar reinforces negative feedback on GnRH and FSH epithelium (with ciliated and secretory cells) secretion. 2. Muscularis: Well-defined, smooth muscle with Ovulation Process: circular/spiral and longitudinal layers ○ LH Surge: 3. Serosa: Thin covering with visceral peritoneum Causes meiosis I to complete, producing Mucosal Folds: Prominent in the ampulla, smaller near the a secondary oocyte and the first polar uterus body. Granulosa cells produce more fluid Epithelium of the Mucosa: (prostaglandins, proteoglycans) to loosen the oocyte. Cell Types: Plasminogen activation weakens the ○ Ciliated Cells: Sweep fluid toward the uterus ovarian wall at the stigma, leading to ○ Secretory Peg Cells: Non-ciliated, secrete follicle rupture. glycoproteins to nourish and protect oocytes and Smooth muscle contractions expel the sperm oocyte, corona radiata, and follicular Hormonal Regulation: Estrogen triggers ciliary elongation fluid into the uterine tube. and hypertrophy during the follicular phase, with atrophy Post-Ovulation: Corpus Luteum Formation: during the luteal phase ○ After ovulation, granulosa and theca interna cells transform into granulosa lutein and theca lutein cells. Oocyte Transport: ○ The corpus luteum forms, producing progesterone and estrogens under LH influence. At Ovulation: ○ Granulosa lutein cells convert androstenedione ○ Infundibulum and fimbriae move closer to the into estradiol and increase progesterone ovary, aiding the capture of the ovulated oocyte production. ○ Oocyte transported into the tube by fimbriae Fate of the Corpus Luteum: contractions and ciliary movement ○ If pregnancy does not occur: ○ Secretory mucus provides a nourishing The corpus luteum regresses, leading to environment and capacitation factors for sperm decreased progesterone secretion and the onset of menstruation. Major Events of Fertilization: Corpus albicans (scar tissue) forms from the degenerated corpus luteum. 1. Sperm Capacitation: Sperm must undergo capacitation in ○ If pregnancy occurs: the female reproductive tract to become capable of hCG (human chorionic gonadotropin) fertilization produced by the embryo maintains the 2. Acrosomal Reaction: corpus luteum. ○ Sperm contact the corona radiata cells, triggering The corpus luteum of pregnancy is release of hyaluronidase from the acrosome maintained for 4-5 months until the ○ Sperm penetrate the zona pellucida with the help placenta takes over progesterone of acrosin production. 3. Fusion of Sperm and Oocyte: Hormonal Feedback: ○ First sperm to penetrate zona pellucida fuses with ○ Estrogen produced by the corpus luteum inhibits oocyte, triggering Ca²⁺ release and exocytosis of FSH secretion, preventing the growth of new cortical granules follicles during the luteal phase. ○ Cortical Reaction: Forms the perivitelline barrier, ○ As the corpus luteum regresses and progesterone blocking polyspermy levels fall, FSH levels rise, initiating the next cycle. 4. Completion of Oocyte Meiosis: ○ Oocyte completes meiosis II, producing a second Uterine Tubes (Oviducts) Overview: polar body and a haploid female pronucleus 5. Pronuclei Fusion: Length: 10-12 cm ○ Male sperm nucleus decondenses to form the Structure: Paired, supported by ligaments and mesenteries male pronucleus for mobility ○ Fusion of male and female pronuclei forms a Regions: diploid zygote ○ Infundibulum: Funnel-shaped opening with 6. Embryo Transport: fimbriae near the ovary ○ Embryo divides as it is transported to the uterus ○ Ampulla: Longest and expanded region, site of (approximately 5 days) fertilization ○ Immotile ciliary syndrome shows that muscular ○ Isthmus: Narrower portion near the uterus contractions play a key role in transport. ○ Uterine/Intramural Part: Passes through the uterine wall into the uterus Uterus Structure and Function Shape and Parts: 1. Pear-shaped organ with thick muscular walls.  2. Body: Largest part, entered by uterine tubes. Embryonic Implantation, Decidua, and Placenta 3. Fundus: Curved superior area between tubes. 4. Isthmus: Narrowing section before the cervix. Blastocyst Development: 5. Cervix: Lower cylindrical part, has a cervical canal ○ Zygote forms morula, then blastocyst with with internal and external os. trophoblast (outer layer) and embryoblast (inner Support: mass). 1. Supported by ligaments and mesenteries ○ Implantation: Blastocyst attaches and penetrates (associated with ovaries and uterine tubes). the endometrial surface, starting around day 6 Wall Layers: after fertilization. 1. Perimetrium: Outer connective tissue layer, Trophoblast Differentiation: continuous with ligaments (serosa in most areas). ○ Cytotrophoblast: Inner layer of mitotically active 2. Myometrium: Thick smooth muscle layer, highly cells. vascularized. Contracts during childbirth. ○ Syncytiotrophoblast: Outer multinucleated cells 3. Endometrium: Mucosa, lined by simple columnar that invade the stroma. epithelium, includes uterine glands. Decidua Formation: ○ After implantation, endometrial fibroblasts become Myometrium decidual cells (polygonal, protein-synthesizing). ○ The endometrium is now called decidua and has Composition: Bundles of smooth muscle separated by 3 regions: connective tissue with venous plexuses and lymphatics. 1. Decidua basalis: Under the embryo, Pregnancy Changes: Growth via hyperplasia, hypertrophy, adjacent to the myometrium. and collagen production. 2. Decidua capsularis: Over the embryo, Post-Pregnancy: Shrinks and returns to pre-pregnancy size thins as the embryo grows. through apoptosis and collagen removal. 3. Decidua parietalis: On the side away from the embryo. Placenta Development: Endometrium ○ Primary Villi: Appear 2 days after implantation, consist of cytotrophoblast cells. Layers: ○ Secondary Villi: Form by day 15, as mesenchyme ○ Basal Layer: Adjacent to myometrium, contains invades primary villi. basal ends of uterine glands. ○ Tertiary Villi: Form capillary loops, connecting to ○ Functional Layer: Superficial, undergoes cyclic the embryonic circulatory system. changes during menstruation. ○ By the end of the first month, the placenta is rich in Blood Supply: branching villi for nutrient and gas exchange. ○ Arcuate arteries in the myometrium send straight Function of Placenta: arteries (to basal layer) and spiral arteries (to ○ Nutrient/Waste Exchange: Between fetal blood in functional layer, sensitive to progesterone). chorionic villi and maternal blood in lacunae of the Cyclic Changes: Influenced by estrogen and progesterone decidua basalis. during the menstrual cycle. ○ Endocrine Role: Produces hormones such as hCG, progesterone, estrogen, relaxin, and Menstrual Cycle Phases lactogen. 1. Menstrual Phase (Day 1-4): ○ Menstrual bleeding with sloughing of the functional endometrial layer. 2. Proliferative Phase (Day 5-14): ○ Estrogen from growing ovarian follicles induces regeneration of the endometrial lining. ○ Endometrial glands are straight and narrow, spiral arteries begin to lengthen. 3. Secretory Phase (Day 15-28): ○ Progesterone from the corpus luteum induces glandular secretion and edema in the endometrial stroma. ○ Glands become coiled, and the endometrium reaches its maximum thickness (5 mm). ○ Prepares for potential embryo implantation. 4. Menstrual Phase (End of Cycle): ○ If no pregnancy, corpus luteum regresses, progesterone levels drop, causing menstrual flow. ○ Spiral arteries constrict, leading to ischemia, cytokine release, and sloughing of the functional layer.  ○ Pre-puberty: Only lactiferous sinuses and small ducts. ○ Puberty: Estrogen causes growth, adipocyte accumulation, duct elongation. Lactiferous ducts: Lined with cuboidal epithelium; Cervix myoepithelial cells contract during milk ejection. Areola: Contains sebaceous glands, sensory nerves, and Structure: Lower, cylindrical part of the uterus. darker pigmentation during pregnancy. Histology: ○ Endocervical mucosa: Simple columnar Breasts During Pregnancy & Lactation epithelium with large, branched mucus-secreting glands. ○ Exocervical mucosa: Nonkeratinized stratified Hormonal Influence: Estrogen, progesterone, prolactin, and squamous epithelium continuous with the vagina. placental lactogen stimulate glandular development. ○ Transformation zone: Junction between Glandular Changes: squamous and columnar epithelium, shifts with ○ Alveolar growth: Spherical alveoli formed, uterine changes. secreting colostrum, rich in proteins and IgA. Cervical mucus: ○ Ducts and alveoli: Lined by cuboidal epithelium ○ Changes cyclically under progesterone (watery and myoepithelial cells; stroma becomes during ovulation, viscous in luteal phase). lymphocytic. ○ In pregnancy, forms a thick plug in the cervical Milk Production: canal. ○ Prolactin stimulates milk synthesis. Connective tissue: Deeper cervix composed mainly of ○ Milk components: Proteins (caseins), lipids, dense connective tissue, with little smooth muscle. lactose, iron, and calcium. During pregnancy: Cervix becomes rigid to retain the fetus; ○ Secretion Mechanism: Merocrine secretion for effaces before parturition through collagen remodeling, proteins, apocrine for lipids. softening, and dilation. Postlactational Changes Weaning: Alveoli and ducts regress, epithelial cells undergo apoptosis, and duct system returns to pre-pregnancy state. Vagina Menopause: Further reduction of alveoli and ducts, loss of connective tissue (fibroblasts, collagen). Structure: No glands; consists of mucosa, muscular layer, and adventitia. Histology: ○ Epithelium: Stratified squamous epithelium (150-200 μm thick). MEDICAL APPLICATIONS ○ Mucosa: Rich in elastic fibers, lymphocytes, neutrophils; mucus from cervical glands. Polycystic Ovary Syndrome (PCOS): ○ Muscular layer: Circular and longitudinal smooth muscle bundles. Enlarged ovaries with numerous cysts, anovulatory state. ○ Adventitia: Dense connective tissue with elastic Likely caused by increased androgen production by fibers, venous plexus, lymphatics, and nerves. ovaries/adrenals. Lubrication: Produced by cervical glands and vestibular Common cause of infertility in women. glands during sexual arousal (Bartholin glands). Protection: Low vaginal pH due to lactic acid from glycogen Follicular Cysts: metabolism, preventing pathogen growth. Late primary or antral follicles can form fluid-filled cysts. External Genitalia (Vulva) Usually benign, but can cause high estrogen levels and menstrual irregularities. Structures: If blood vessels are disrupted, hemorrhagic cysts may form. ○ Vestibule: Space with vestibular glands. ○ Labia Minora: Skin folds without hair follicles, Tubal Ligation & Salpingitis: numerous sebaceous glands. ○ Labia Majora: Similar to scrotal skin. Tubal ligation is a common contraceptive method. ○ Clitoris: Erectile tissue homologous to the penis. Salpingitis (inflammation of uterine tubes) caused by Mucosa: Stratified squamous epithelium, richly innervated infections can lead to infertility or ectopic pregnancy. for sexual arousal. Ectopic pregnancy can cause tube rupture and hemorrhage, which is life-threatening. Mammary Glands Endometriosis: Development: Originates from ectoderm along milk lines, forms 15-25 lobes. Endometrial cells can reflux into the pelvic cavity, leading to Lobes: Separate glands with own excretory lactiferous endometrial tissue growing outside the uterus. ducts, open independently in the nipple. Causes pelvic pain, inflammation, ovarian cysts, adhesions, Breast Development (Puberty): and infertility.  Tissue grows and degenerates under hormonal influence but cannot be removed. Placenta Previa: Placenta attaches near the internal os of the uterus, obstructing the vagina. Requires cesarean delivery to prevent fetal death due to obstructed parturition. Cervical Cancer: Pap smear screening reduces cervical cancer incidence. Epithelial dysplasia (precancerous change) occurs around age 54. HPV is strongly linked to the development of cervical cancer. Atrophic Vaginitis: Thinning of vaginal epithelium due to low estrogen levels, common in postmenopausal women. Leads to frequent inflammation and infections. Primary vaginal squamous cell carcinoma is rare; most vaginal cancers are secondary from cervix or vulva. Breastfeeding and Oxytocin: Nipple stimulation during breastfeeding releases oxytocin from the posterior pituitary. Oxytocin causes milk ejection by contracting smooth muscle in ducts and alveoli. Negative emotions (e.g., frustration) can inhibit oxytocin release and prevent milk ejection. Breast Cancer: Often originates from epithelial cells in the terminal lobules of the breast. Most common type: invasive ductal carcinoma, where cancer cells invade surrounding tissue. Metastasis to lungs or brain causes mortality. Early detection (e.g., mammography, self-examination) reduces mortality rates. Mastitis: Infection of mammary glands, common during lactation. Caused by milk obstruction in small ducts, leading to bacterial infection.