Female Reproductive System 1 Flashcards
What does the female reproductive system consist of?
Consists of organs located in the pelvic cavity as well as external genitalia. • Ovary • Uterine tube • Uterus • Placenta • Vagina • *Mammary glands Many of these organs undergo hormone mediated changes • At puberty (menarche = 1st period) • During the menstrual cycle • Pregnancy
Summarize the structure function of the ovaries
Function:
• Produce gametes = oogenesis
• Secrete hormones = (steroidogenesis): estrogens and progesterone
Structure:
- Germinal epithelium
- Tunica albuginea
- Cortex
- Medulla (M):
- Cyclic ovarian function is regulated by hormones from the pituitaryluteinizing and follicle stimulating hormones (LH &FSH)
Summarize the histological structure of the ovaries
- “Germinal” epithelium (GE)
− Covers ovary; is continuous with mesovarium
− Single layer of cuboidal cells (mesothelial origin)
− 70% of ovarian cancer arise from the GE - Tunica albuginea
− Deep to germinal epithelium
− Dense connective tissue layer - Cortex
− Peripherally located
− Parenchyma: Follicles in different stages of development
− Cellular rich Connective tissue - Medulla
− Central portion
− Loose connective tissue
− Blood vessels/nerves/lymphatics
explain oogenesis
- Parenchyma: follicle with oocyte
- Oogenesis and follicular development begins before
birth
I. Oogonia forms primary oocyte
• ~600,000 – 800,000 by birth
II. Primary oocyte arrested in prophase of meiosis I
until puberty
• Lasts between 12-50 yearsrisk of
chromosomal anomalies
III. After menarche, mature every month
• Just before ovulation Meiosis I complete secondary oocyte (arrested in metaphase II)
• ~400 ovulated during reproductive years
IV. Meiosis complete at fertilization
Summarize follicular development
The oocyte associates with ovarian follicular cells to form follicles
During follicle development, hormone-controlled changes occur in the oocyte, follicular cells and ovarian stroma.
1. Primordial follicle
2. Growing follicles:
I. Primary: A. Early B. Late II. Secondary
3. Mature/ Graafian
4. Atretic
Summarize follicular phase of the ovary
Under influence of FSH & LH Development of follicles FSHGranulosa & Theca cells ESTROGEN - Principal Hormone Late follicular phase • Increased progesterone • LH surge • Small FSH increase • OVULATION
What is the primordial follicle?
Most numerous follicles
Located just deep to the tunica albuginea
Oocyte (size ~30μ)
• Primary oocyte in prophase I of meiosis Diploid (2n)
Further meiotic activity arrested
• Large eccentric nucleus, large nucleoli
Follicular cells
• Single layer of squamous follicular cells surrounds oocyte
• Basal lamina separates follicular cells from stroma
Describe the growing follicle:early primary
Some (~10-20) follicles begin to mature at puberty Primordial follicleearly primary follicle
Deeper in cortical stroma
Oocyte
• Primary oocyte enlarges (follicle ~50-80 μm)
• Secretes an Amorphous glycoprotein layer around itself
Zona Pellucida
o Homogenous, refractile o Eosinophilic, PAS +
Zona pellucida glycoproteins (ZP-1, ZP-2, ZP-3 & ZP-4)
• Sperm-binding receptor
• Induces acrosome reaction
Follicular cells (FC)
• Follicular cells become cuboidal (unilaminar)
Describe growing follicle: late primary
Zona pellucida (ZP) is well defined: • Processes of granulosa cells • Microvilli of oocyte Follicular cells • Multilayered mass (Multilaminar) Granulosa cells (GC) – Stratum granulosum • Receptors for FSH • Secrete aromataseandrostenedione to estrogen • Distinct basal lamina Adjacent stroma forms Theca folliculi 1. Theca interna (TI) ― Highly vascularized area close to basement membrane ― Receptors for LH (and LDL) ― Steroid-secreting cells ― Produce androstenedione (precursor of estrogen) 2. Theca externa (less defined) ― connective tissue and smooth muscle
Describe the growing follicle: secondary (Antral)
Oocyte
• Eccentric position; Size 125μm
• No further growth
Stratum Granulosum
• •
•
6-12 layers of granulosa cells surround oocyte Appearance of Antral spaces containing liquor folliculi
Secreted by granulosa cells
o Hyaluronan and hormones o Oocyte maturation inhibitor
Granulosa cells begin to organize into a thickened mound
Theca layers are more defined
• Basal lamina between theca interna and granulosa
Describe the mature or Graafian follicle
Located close to ovarian surface (bulge) Extends through full cortical thickness Large (≥ 10mm) at ovulation
Oocyte
• Primary oocytesecondary oocyte just before ovulation
Stratum Granulosum (SG)
• Single large crescent-shaped antrum
• Cumulus oophorus (CO):
”hillock” of cells connecting oocyte to follicular wall
• Corona radiata:
1-2 layers cells lining oocyte
Microvilli of these cells and oocyte communicate via
gap junctions
• Membrana granulosa remaining mural granulosa cells
surrounding antral lumen
Thin stratum granulosum
Theca layers thick and well defined
Describe the collaborative synthesis of hormones
Theca Interna
• LH receptors – stimulate androgen production
• Secrete Androgens
Granulosa cells
• FSH receptors – stimulate aromatase activity
• Secrete aromatase: convert androgens to estrogen
• Which area of cells have highest aromatase activity?
Estrogens stimulate granulosa proliferation • further increase in estrogen (estradiol)
• *Net rapid increase in follicle size
What are the functions of hormones and ovarian surface in pre-ovulation?
Hormones
• Estrogensensitization of LH and FSH to GnRH
• LH surge (~24 hours before ovulation)
Smaller FSH increase
• Follicle
Desensitization of LH receptors
Decreased estrogen production
• Oocyte
Primary oocyte completes first meiotic division
forms secondary oocyte & first polar body Which follicle?
Immediately enters second meiotic division - arrested at metaphase II
Ovarian Surface
• Cessation of blood flow to surface over bulge
• Follicular Stigma
Elevates, then ruptures (Indication of impending ovulation)
What causes ovulation?
Increase follicular fluid volume and pressure • Spaces between granulosa cells enlarge
Follicular wall proteolysis + GAG deposition
• Oocyte + cumulus cells loosen from GC
• Corona radiata becomes single layer
Smooth muscle contraction in theca externa
Secondary oocyte (+ corona radiata) released
Meiosis II complete ONLY upon fertilization
Failure of fertilization leads to degeneration of the oocyte.
Describe the luteal phase of ovary
Begins after ovulation
Formation of Corpus Luteum
PROGESTERONE - Principal Hormone
LH responsible for maintenance of corpus luteum
Degeneration of corpus luteum without fertilization
What are the significance of Corpus Hemorrhagicum and Luteum?
After ovulation: follicle wall collapses, thrown into folds
Corpus hemorrhagicum
• Filled with blood (thecal capillaries)
Corpus Luteum (CL)
Stromal CT invades cavity (FC)
Luteinization of Granulosa and Theca Interna cells
Increase size, fill with lipid droplets
Secretes hormones:
Inhibit LH + FSH (prevent follicle development & ovulation)
Prepares the uterus for implantation CL of menstruation (no fertilization):
− Declines after 10 days
CL of pregnancy (fertilization):
− first few (~8) weeks of pregnancy (declines as placenta develops)
What are the functions of the corpus Luteum ?
Cells have features characteristic of steroid production:
− Lipids and lipochrome pigment- yellow appearance
− SER, abundant mitochondria with tubular cristae
1. Membrana granulosaGranulosa Lutein cells (GLC)
− Large, round cells with spherical nuclei
− 80% of cells
− Central location
− Secrete: progesterone, inhibin and estrogen
2. Theca internaTheca Lutein cells (TLC)
− Smaller, more deeply staining cells with spherical
nuclei
− 20% of cells
− Peripheral location scattered between GLC
− Secrete: progesterone and androgens
What is the Atretic follicle?
Several follicles develop during oogenesis, menstrual cycles
Usually, ONE ovum released (ovulation)
Others degenerate Atretic follicles
Mediated by apoptosis
• Smallerfollicles
Oocyte and GC shrink, degenerates Disappears from stroma
• Larger follicles:
Oocyte + GC: apoptotic changes
Zona pellucida: prominent, distorted (fold or collapse)
Glassy Membrane: thickening of BM between GC and TI
Theca cells: Interstitial glands
o Cluster of epithelioid cells – continue secreting hormones
What are Polcystic ovaries?
• Excessive androgenestrogen • Graafian follicle fails to mature anovulatory cycle • Anovulatory cycles result in infertility Findings -enlarged ovary -Thick tunica albuginea (TA) -Impairs ovulation -Multiple fluid fill cavities—> follicular cysts
What are the structures/functions of ovarian/Fallopian tubes/ ovarian ducts?
Pair of fibromuscular tubes, 10-12 cm Functions • Conduct ova expelled from ovary to the uterus. • Provide environment for fertilization* Parts • Infundibulum • Ampulla* • Isthmus • Intrauterine (intramural) Layers • Serosa • Muscularis • Mucosa Mucosa forms longitudinal folds—>well defined infundibulum and ampulla.
Describe the histology of uterine tubes
Mucosa – simple columnar epithelium with 2 cell types:
Ciliated columnar epithelial cells (above)
• Most numerous in infundibulum + ampulla (almost 75%)
• Number of cells increased by estrogen (Which phase?)
Secretory cells or peg cells (arrows and below )
• Non-ciliated
• Wedged between ciliated cells (arrow)
• Number of cells increased by progesterone (Which phase?)
• Secretes nutritive material for ovum.
The ciliated cells keep the fluids secreted by the peg cells in motion
Oocyte is carried along the tube by Ciliary movements and peristaltic muscular activity
What are the layers of the uterine tubes?
Mucosa:
Mucosal folds more prominent in the infundibulum
Peg cells increase and ciliated cells decrease towards uterus
Muscular layer
Thicker in intramural region
What is the uterus?
Muscular pelvic organ
Provides protective and nutritive
environment for the fetus
Three Anatomical Parts: • Fundus
• Body
• Cervix.
Three Histological Layers:
• Endometrium: Mucosa (glandular)
• Myometrium: Muscular
• Perimetrium: Outer serosa/ adventitia
Endometrium and myometrium undergo cyclic changes:
• Menstrual cycle
Give the general structure of the endometrium
General Structure Simple columnar epithelium Simple tubular glands Lamina propria (endometrial stroma): Mesenchymal like connective tissue Highly vascularized
What are the layers of the endometrium?
- Stratum functionale
− Surface epithelium
− Superficial portion (remainder) of glands
− Supplied by branches of spiral arteries
− Changes dramatically during the menstrual cycle
− Sheds as menstrual debris if pregnancy does not occur
2. Stratum basale (~1mm) − Stem cell niche of the functionale − Basal portion (origin) of glands − Lower portion spiral arteries − Retained during menstruation − Close to myometrium
What are the ovarian hormones and uterus?
Pituitary gonadotrophins regulate ovarian follicle maturation after puberty
Ovarian follicle development (ovarian
cycle) results in sex hormone release
• Follicular phase
• Luteal phase
Affects the uterus—>Preparation for implantation
Changes in the uterine lining—> menstrual cycle
Summarize the menstrual cycle
Cyclical changes that occur in the endometrium in response to ovarian hormones
Typical cycles
28 days long
Ovulation at day 14
Phases:
− Menstrual (Day 0 of cycle)
− Proliferative
− Secretory
Describe the proliferative phase of the menstrual cycle
After menses 5th to 14th day of the cycle
Under influence of ovarian estrogen
Also called estrogenic phase Which ovarian phase?
Stratum Functionale proliferates:
• Epithelial cells – reconstitute glands
Narrow lumens, relatively straight/ slightly wavy Basal glandular cells accumulate glycogen
• Endothelial cells – lengthening of spiral arteries Slightly coiled, lower 2/3 of functionale
• Stromal cells – proliferate, make CT
Endometrium reaches thickness of ~3mm
Describe the secretory phase of the menstrual cycle
1-2 days after ovulation.
Under the influence of progesterone
AKA progesterone phase Which ovarian phase?
Stratum functionale hypertrophies:
• Glands elongate, coil and dilate
Mucoid secretions: glycogen and glycoproteins
• Spiral arteries highly coiled and longer Extend to superficial part of stratum functionale
• Endometrium becomes edematous Stromal cells filled with glycogen
• Endometrium attains its greatest height (~5-6mm)
Divided into:
• Early secretory phase
• Late secretory phase
Differentiate the early and late secretory phase of the menstrual phase
Early
― More epithelium than glands
― Glands slightly elongated & coiled
― Spiral arteries 2/3 into functionale
Late
― Glands: elongated, coiled (saw-tooth), dilated (sacculated)
― Cells and glands filled with glycogen, glycoprotein
― Spiral artery in superficial part of stratum functionale
Describe the menstrual phase of the menstrual cycle
Due to decline in progesterone How long after ovulation?
• Periodic contraction of spiral arteries
• Ischemia around day 28
• Glands degenerate, endometrium shrinks
• Rupture of blood vessels
Functional layer sheds menstruation • Blood, fluid, necrotic stroma + epithelium
Only Basale remains intact: straight (proximal spiral) arteries intact
Lasts ~5 days