L21 Ch27 Female Reproductive System

Overview of the Biological Female Reproductive System

• The lecture focuses strictly on biological sexes and anatomy, specifically addressing biological females.
• Key internal organs of the system include:
  • Ovaries: A paired set of gonads located on either side of the pelvis.
  • Uritan tubes (also called fallopian tubes): These serve as the link connecting the ovaries to the uterus.
  • Uterus: A centrally located, pear-shaped organ.
  • Cervix: The lower, narrow portion of the uterus that opens into the vagina.
  • Vaginal canal: An elastic canal connecting the uterus to the outside of the body.
• External genitalia is collectively known as the vulva, which includes:
  • Leon minus (singular) and Leon major (singular), which refer to the paired folds of skin (labia minora and labia majora) protecting the urethral and vaginal openings.
• Accessory organs include the breasts or mammary glands, located in the upper thoracic region, which are considered part of the reproductive system due to their role in lactation and newborn nourishment.

Support and Ligaments of the Reproductive Organs

• The ovaries, uritan tubes, and uterus are supported and anchored within the pelvic cavity by several ligaments:
  • Broad ligament: A large, sheet-like fold of peritini (the membrane lining the abdominal cavity) that connects and supports the ovaries, uritan tubes, and uterus.
  • Mess ovarium: A specific thickening of the broad ligament dedicated to suspending and supporting each ovary.
  • Ovarian ligament: A fibrous core connecting the lateral wall of the uterus (near the uritan tube junction) to the medial surface of the ovary.
  • Suspensory ligament: Extends from the lateral surface of the ovary to the pelvic wall. This ligament is crucial as it also contains the major blood vessels that supply and drain the ovary.
  • Uterosacral ligament: Paired ligaments connecting the lateral surface of the uterus to the anterior surface of the sacrum (the triangular bone at the base of the spine).

Detailed Anatomy of the Ovaries

• Physical Dimensions: A typical ovary is a flattened oval measuring approximately $5\,\text{cm}$ in length, $2.5\,\text{cm}$ in width, and $8\,\text{mm}$ in thickness.
• Ovarium helum: A specific point on the ovary where blood vessels, lymphatic vessels, and nerves enter and exit. This is also the site where the ovary attaches to the mess ovarium.
• Internal Organization: The ovary consists of two main stroma layers:
  • Cortex: The outer, superficial region where gamete production occurs.
  • Medulla: The deeper central region containing loose connective tissue, blood vessels, lymphatics, and nerves.
• Covering Layers:
  • Germinal epithelium: The outermost layer of simple cuboidal epithelium.
  • Itunica albonia (also referred to as tunical alongia): A tough fibrous layer of dense connective tissue located directly beneath the germinal epithelium.

Core Reproductive Processes and Cycles

• The biological female reproductive system orchestrates three primary, interconnected, and highly regulated processes:
  • Oenesis: The production of the female gamt (gamete), known as the oite or egg.
  • Ovarian cycle: A monthly series of events focused on the development and maturation of the ovarian follicle within the ovary.
  • Uterine cycle (or menstrual cycle): A monthly series of events within the uterus preparing the endometrium (uterine lining) for potential implantation.
• These processes are tightly linked and regulated by hormonal fluctuations throughout the month.

Oenesis and Follicular Development

• Oenesis Timeline: This process begins before birth during fetal development, accelerates at puberty ($initiated by FSH$), and ends at menopause.
• Initial Development:
  • Oonia (or oronia): Diploid stem cells that undergo mitosis in the fetus to increase their numbers.
  • Primary oites: Some oonia undergo meiosis I and become arrested as primary oites until puberty.
• Follicle Maturation Stages:
  • Primordial ovarian follicles: The basic unit consisting of a primary oite surrounded by a single layer of flattened follicle cells.
  • Primary ovarian follicles: Development is stimulated by Follicle Stimulating Hormone ($FSH$). Follicle cells divide into multiple layers of cuboidal granulosa cells.
    • Sona pelucida: A glycoprotein-rich extracellular matrix secreted by the oite that acts as a protective coat.
    • Granulosa cells produce estrogen and provide nutrients to the oite.
  • Secondary ovarian follicles: Characterized by significant enlargement and the active production of follicular fluid by granulosa cells.
  • Tertiary follicles (also known as Graphian follicles or vicular follicles):
    • Antrum: A large, fluid-filled cavity within the follicle.
    • Corona radiata: A specialized layer of granulosa cells immediately surrounding the oite that will travel with it after ovulation.
    • The primary oite completes meiosis I at this stage to become a secondary oite and a polar body.

Hormone Regulation and Ovulation

• Estrogen (Estradiol):
  • Estradiol is the most dominant and active estrogen.
  • It is synthesized from testosterone through an enzymatic conversion and is derived from cholesterol (a steroid hormone).
  • Functions: Stimulates bone/muscle growth, maintains secondary sex characteristics, affects sex drive, and initiates repair of the uterine lining.
• Ovulation:
  • Triggered by a surge in lutaneine hormone ($LH$) from the pituitary gland.
  • The LH surge weakens the wall of the mature tertiary follicle, causing it to rupture.
  • The secondary oite is expelled from the ovary and captured by the fimry (finger-like projections of the uritan tube).
• Post-Ovulatory Structures:
  • Corpus lethium: The "yellow body" formed from the empty follicle; acts as a temporary endocrine gland secreting progesterone and some estrogen to prepare the uterus for pregnancy.
  • Corpus albeans: The "white body" or fibrous scar tissue that forms if fertilization does not occur and the corpus lethium degenerates (approximately $12$ days post-ovulation).

The Uritan Tubes and Fertilization

• Uritan Tubes: Paired hollow muscular tubes approximately $13\,\text{cm}$ long.
• Regional Anatomy:
  1. Fimry: Projections that sweep over the ovary to direct the oite into the tube.
  2. Infundib (infundibulum): Funnel-shaped opening nearest the ovary; contains cilia that create currents to move the oite.
  3. Ampula: The longest and widest middle section of the tube.
  4. East moose (isthmus): A short, constricted region connecting to the uterine wall.
  5. Uterine part: The segment that passes through the uterine wall and opens into the cavity.
• Histology: The tubes are lined with ciliated and non-ciliated columnar cells and contain smooth muscle layers for peristas (peristaltic contractions).
• Fertilization Details: Union of sperm and egg typically occurs $12$ to $24$ hours after ovulation, usually in the distal $2/3$ of the uritan tube within the ampula region.

Anatomy and Layers of the Uterus

• Dimensions: Approximately $7.5\,\text{cm}$ in length and $5\,\text{cm}$ in diameter.
• Functions: Protection of the fetus, nutritional support, and waste removal.
• Anatomical Parts:
  • Body: Largest central region.
  • Fondus (fundus): Superior rounded portion.
  • Uterine cavity: Hollow space inside the body.
  • Isthmus: Constricted inferior region.
  • Cervix: Projects into the vaginal canal.
    • Internal O: Opening to the uterine cavity.
    • External O: Opening to the vagina.
    • Cervical canal: The space between the two opens.
• The Uterine Wall Layers:
  • Endometrium: Deepest glandular layer consisting of two sub-layers:
    • Functional layer: Contains uterine glands; undergoes cyclical changes and occupies the area adjacent to the cavity.
    • Basil layer: Deep to the functional layer; remains stable to rebuild the functional layer.
  • Myometrium: Thick middle layer of smooth muscle tissue.
  • Perimetrium: Outermost incomplete serosa (visceral peritini).

The Uterine Cycle Phases

1. Menstrual Phase:
   • Triggered by a drop in progesterone and estrogen.
   • Causes constriction of spiral arteries in the functional layer, leading to tissue death.
   • The functional layer is shed through the vagina as demenses (bleeding).
2. Proliferative Phase:
   • Triggered by rising estrogen from developing ovarian follicles.
   • The basil layer undergoes rapid cell division to regenerate and thicken the functional layer and uterine glands.
3. Secretory Phase:
   • Driven by high levels of progesterone and estrogen from the corpus lethium.
   • Endometrial glands grow and become active, secreting nutrient-rich fluid (glycogen).
   • The lining reaches its peak development to support an embryo.

The Vagina and External Genitalia

• Vagina: Elastic muscular tube ($7.5$ to $9\,\text{cm}$ long) serving as the elimination pathway for menstrual fluids, the receptacle for the penis/sperm, and the birth canal.
  • Vaginal forex: The recess or space surrounding the edge of the cervix at the superior end of the vagina.
  • Hyman: A thin elastic mucous membrane that may partially or completely separate the vaginal canal from the vestibule.
• External Genitalia (Vulva):
  • Vestibule: Central space enclosed by the leon minora; contains vestibular glands that secrete lubricating mucus.
  • Clitoris: A small erectile organ anterior to the leon minora; homologous to the male penis and covered by the prepuse (clitoral hood).
  • Leon majora: Larger outer folds forming the boundary of the vulva, homologous to the scrotum.
  • Mon's pubis: A raised mound of adipose tissue providing cushion over the pubic symphysis.

Mammary Glands and Lactation

• Breasts: Accessory organs for nourishment via lactation.
• Structural Components:
  • Nipple: Center point for milk release.
  • Areola: Pigmented area with large sebaceous glands for lubrication.
  • Pectoral fat pad: Location of the mammary glands.
• Lactation Pathway:
  • Alvolar cells in lobules synthesize milk.
  • Milk travels through small loar ducts into larger lactophorious ducts.
  • Lactophorious sinus: An expanded reservoir for storage just beneath the nipple.
  • Approximately $15$ to $20$ sinuses open onto the nipple surface.

Menopause and Aging

• Menopause: Typically begins between the ages of $45$ and $55$.
• Definition: A substantial and sustained decline in estrogen levels.
• Physiological Effects:
  • Reduction in the size of the uterus and breasts.
  • Thinning and loss of elasticity in vaginal walls.
  • Weakening of supporting pelvic tissues.
  • Increased risk of osteoporosis (thinning of bone tissue/fractures).
  • Hot flashes: Sudden sensations of intense heat due to hormonal fluctuations.

Recommended Resources

• The Great Sperm Race: A documentary recommended by the lecturer (found on YouTube) that visualizes the journey of the sperm from the testes to the secondary oite using analogies and engaging visuals.