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)
What are the events in the hours before ovulation?
1) Completion of the first meiotic division
- secondary oocyte
- first polar body
2) Secondary oocyte begins the second meiotic division
- but arrests at metaphase II
- never completes meiosis unless fertilisation occurs
3) Formation of the stigma
- a whitish or translucent ischemic area
- caused by the mature dominant follicle bulging against the tunica albuginea
What is the corpus luteum?
A temporary endocrine gland in the ovarian cortex
How is the corpus luteum formed?
1) Granulosa cells
- changing to granulosa lutein cells
- invaded by capillaries
- increase greatly in size, without dividing, and eventually comprise about 80% of the CL
- expand their role in aromatase conversion of androstenedione into estradiol
2) Theca interna
- changing to theca lutein cells
- half of the size of the granulosa lutein cells
- typically aggregated in the folds of the wall of CL
- becomes well vascularised
- produce large amounts of progesterone and androstenedione
What do cells of the granulosa and theca interna have in common?
Both change histologically and functionally under the influence of LH
Both become specialised for more extensive production of progesterone (for 10-12 days) in addition to estrogens
What is the fate of the corpus luteum if pregnancy occurs?
Production of hCG by trophoblast cells of the implanted embryo
- with targets and activity similar to that of LH
- prevents the drop in circulating progesterone
- maintains and promotes further growth of the corpus luteum
- stimulates secretion of progesterone to maintain the uterine mucosa
After 4-5 months of pregnancy:
- production of progesterone (and estrogens) at levels adequate to maintain the uterine mucosa by placenta
- CL degenerates and is replaced by a large corpus albicans
What is the consequence of decreased secretion of progesterone by the corpus luteum?
Menstruation
What is the role of the corpus luteum during menstruation?
- Persistence of CL for part of only one menstrual cycle
- Phagocytosis of the remnants of CL by macrophages
- Invasion of fibroblasts and production of a scar
What is the corpus albicans?
A structure that is formed due to diminished LH stimulation and absence of pregnancy. Occurs due to reduced steroid production in CL and apoptosis and regression of CL.
Identify the 4 regions of the uterine tubes.
1) Infundibulum
- fringed with finger-like extensions called fimbriae next to the ovary
2) Ampulla
- the longest and expanded region
- where fertilisation normally occurs
3) Isthmus
- more narrow portion nearer to the uterus
4) Uterine/intramural part
- passes through the wall of the uterus
- opens into the uterine cavity
What are the key histological features of the wall of the uterine tube?
1) Mucosa
* Numerous branching, longitudinal folds which are most prominent in the ampulla
* Smaller in the regions closer to the uterus and are absent in the intramural portion of the tube
* Epithelium: simple columnar epithelium
–> ciliated cells: ciliary movements sweep fluid toward the uterus
–> secretory peg cells: non-ciliated and often darker staining - secrete glycoproteins of a nutritive mucus
* lamina propria: loose connective tissue
2) Muscularis:
* Thick, with interwoven circular (or spiral) and longitudinal layers of smooth muscle
3) Serosa
* Thin, covered by visceral peritoneum with mesothelium
What are the 3 anatomical parts of the uterus?
1- Fundus
2- Body
3- Cervix
- internal os
- external os
What are the 3 histological layers of the uterus?
1- Endometrium/Mucosa
2- Myometrium
3- Perimetrium
Outline the endometrium layer of the uterus.
Epithelium; simple columnar
- ciliated cells
- secretory cells
Lamina propria or stroma
Zones:
A) Functional layer; undergoes profound changes during menstrual cycle
- compact layer
- spongy layer
B) Basal layer; remains relatively unchanged during the menstrual cycles
What are the two types of arteries in the endometrium?
1) Straight arteries: supply only the basal layer
2) Spiral arteries: progesterone-sensitive; bring blood throughout the functional layer
Outline the histology of the myometrium and perimetrium of the uterus.
Myometrium:
* a thick tunic of highly vascularised smooth muscle
* interwoven layers, with fibres of the inner and outer layers
Perimetrium:
* Largely; serosa covered by mesothelium
* in some areas: adventitia
Identify the three stages of the menstrual cycle.
1) Proliferative/Follicular/Estrogenic Phase
2) Secretory/luteal phase
3) Menstrual phase
Outline key features of each stage of menstruation.
1) Proliferative/Follicular/Estrogenic:
* 8-10 days on average
* increase in thickness of uterine mucosa
* coincides with rapid growth of a small group of ovarian follicles growing as vesicular follicles
* estrogens act on the endometrium, inducing regeneration of the functional layer lost during menstruation
2) Secretory/luteal phase
* starts as a result of the progesterone secreted by the corpus luteum
* maximum thickness (5mm) of endometrium during the secretory phase as a result of the accumulation of secretions and edema in the stroma
3) Menstrual phase
* Day 1 of the menstrual cycle = the day when menstrual bleeding appears
* Lasts 3-4 days on average
* Caused by reduced circulating levels of progesterone and estrogens when fertilisation and implantation do not occur/regression of the corpus luteum
What are the two histological landmarks of the cervix?
Endocervical and exocervical mucosa
Outline the endocervical mucosa of the cervix
- Epithelium: simple columnar
- Lamina propria:
- with many large, branched, mucus-secreting cervical glands
- lacks spiral arteries
Outline the exocervical mucosa of the cervix
- the cervical region around the external os projecting slightly into the upper vagina
- nonkeratinised stratified squamous epithelium continuous with that of the vagina
What is the transformation zone?
Junction between the squamous epithelium and the mucus-secreting columnar epithelium of the endocervix
Outline the key histological features of the vagina.
1) Mucosa
* Epithelium:
- stratified squamous
- synthesising and accumulating glycogen by estrogens stimulation
- when the cells desquamate, bacteria metabolise glycogen to lactic acid, causing a relatively low pH within the vagina
* Lamina propria
- no glands: mucus in the vagina is produced by the cervical glands
2) Muscular layer
* two indistinct layers of smooth muscle
- circular bundles; next to the mucosa
- longitudinal bundles; near the adventitia
3) Adventitia
* rich in elastic fibres
* contains an extensive venous plexus, lymphatics and nerves
Outline the histology of the external genitalia/vulva.
All covered by stratified squamous epithelium
Vestibule:
* a space whose wall includes the tubuloacinar vestibular glands
Labia minora:
* folds of skin lacking hair follicles but with numerous sebaceous glands
Labia majora:
* homologous and histologically similar to the skin of the scrotum
Clitoris:
* an erectile structure homologous to the penis with paired corpora cavernosa
Outline key features of the mammary glands
- Highly modified apocrine sweat glands
- each mammary gland has 15-20 lobes of the compound tubuloalveolar type
- each lobe consists of many lobules (TLDU) as well as a separate gland with its own excretory lactiferous duct
What is the histology of the mammary glands during puberty (non-pregnant adults)
- Secretory alveoli; composed of
- cuboidal epithelium
- myoepithelial cells
- basal lamina
- terminal ducts and lactiferous ducts;
- lined with simple cuboidal epithelium
- lactiferous sinuses;
- lined with stratified cuboidal epithelium
What is the function of alveolar cells of the lactating mammary gland?
Secretion of proteins (exocytosis or merocrine secretion) and secretion of lipids (apocrine secretion)
