Female Reproductive Histology Flashcards
What are the key functions of the female reproductive system?
- produces the female gametes (oocytes)
- produces steroidal sex hormones
- provides the environment for fertilization
- holds the embryo
What are ovaries?
Almond-shaped cytogenic sex glands
What are the 4 key structural elements of the ovaries?
1) Surface (or germinal) epithelium
- simple cuboidal epithelium
- continuous with the mesothelium
- overlying tunica albuginea
2) Tunica albuginea
- a layer of dense CT capsule underneath germinal epithelium
3) Cortex; a region with a stroma of;
- highly cellular connective tissue
- many ovarian follicles varying in size after menarche
4) Medulla
- loose connective tissue
- blood vessels
What is the histology of primordial follicles?
1) A primary oocyte:
- spherical and about 25um in diameter
- with a large nucleus containing chromosomes in the first meiotic prophase
2) Follicular cells
- a single layer of the flattened cells enveloping the primary oocyte
3) Basal lamina
- surrounds the follicular cells
- marking a clear boundary between the follicle and the vascularised stroma
- acts as a blood-follicle barrier
How does follicular development begin?
Begins in puberty with the release of FSH
A small group of primordial follicles each month begins a process of follicular growth
What does follicular development involve?
1) Growth of the oocyte
2) Proliferation and changes in the follicular cells
3) Proliferation and differentiation of the stromal fibroblasts around each follicle
How are follicles selected to grow and ovulate?
Complex hormonal balances
Subtle differences among follicles in:
- FSH receptor numbers
- Aromatase activity
- Estrogen synthesis
What are the two types of primary follicles?
1) Unilaminar primary follicle:
- a simple cuboidal epithelium (follicular cells) around the growing oocyte
2) Multilaminar primary follicle:
- a stratified follicular epithelium (granulosa)
- follicular cells; now termed granulosa cells (still avascular and surrounded by a basement membrane)
What is the follicular theca?
Stromal cells immediately outside each growing primary follice
What does the follicular theca differentiate into?
1) Theca interna:
- a well-vascularised endocrine tissue
- with typical steroid-producing cells secreting androstenedione
2) Theca externa:
- a fibrous tissue with fibroblasts and smooth muscle merges gradually with the surrounding stroma
What is androstenedione?
A secretory product of theca externa that is converted to estradiol by enzyme aromatase of granulosa cells
What is the zona pellucida?
A layer between oocytes and follicular cells.
Contains 4 glycoproteins (ZP1, ZP2, ZP3 and ZP4) secreted by the oocyte and follicular cells
What tends to happen as primary follicles grow?
They move deeper in the cortex
- emergence of small spaces between the granulosa layers as the cells secrete follicular fluid (liquor folliculi)
What are key features of secondary/antral follicles?
1) Germ cell/gamete; primary oocyte
2) Granulosa cells:
A) Membrana granulosa/stratum granulosum; line the follicular wall
B) Cumulus oophorus; the hillock of granulosa cells around the oocyte
C) corona radiata; the tightly adhering granulosa cells immediately surrounding zona pellucida - accompany the oocyte when it leaves the ovary at ovulation
3) Antrum
4) Follicular theca;
A) Theca interna
B) Theca externa
What is follicular atresia?
Degenerative process that happens in most ovarian follicles due to apoptosis or removal by phagocytic cells
What are key features of mature/graafian follicles?
1) Germ cell/gamete; secondary oocytes
2) Granulosa cells;
A) Membrana granulosa/stratum granulosum
B) Cumulus oophorus
C) Corona radiata
3) Antrum; single large vesicle
- rapidly accumulates more follicular fluid
- expands to a diameter of 2cm
- forms a bulge at the ovary surface visible with ultrasound imaging
4) Follicular theca
- theca interna
- theca externa
What happens during ovulation?
Ovulation is a hormone-stimulated process by which the oocyte is released from the ovary.
Dominant follicle reaches most developed stage of growth and undergoes ovulation.
Normally occurs midway through the menstrual cycle (around the 14th day of a typical 28-day cycle)