Uterus, menstrual cycle, cervix, and vagina

Question 1

Micro of uterus 1

Answer 1

• The myometrium is composed of SmM that look like dark horizontal lines near the outer wall of the uterus
• The myometrium/endometrium interface is the transition from dark SmM bands to light pink endometrial storm w/ lots of ascending spiral arteries (towards lumen)
• The endometrium is broken up into 2 levels, depending on the phase of the menstrual cycle

Question 2

Micro of uterus 2

Answer 2

• Stratum basalis (lowest level, closest to the myometrium) is always present (kept even during menses)
• Stratum functionalis is above the basalis and is grown during the proliferative and secretory phases and is lost during menses
• Epithelial glands that dive into the basalis layer are continuous w/ the uterine surface epithelium
• There is no distinct border btwn the basalis and the functionalis

Question 3

Endometrial changes during menstrual cycle: proliferative phase

Answer 3

• Proliferative phase (day 4/6- day 14): E2 causes the stratum functionalis to regenerate from the stratum basalis
• There is extensive proliferation of stromal, glandular, vascular, and epithelial cells (glands may appear stratified)
• Increased blood flow leads to edema in the tissue and there is increased glycogen accumulation (in glands)

Question 4

Endometrial changes during menstrual cycle: secretory phase

Answer 4

• Corresponds to luteal phase of ovary, at this point the uterus is edematous and spongy (saw-tooth appearance in glands)
• Glands undergo basal vacuolization as cells accumulate glycogen for embryo
• There is a rich vascular supply creating a looser storm for embryo implantation
• Fertilization occurs very soon after ovulation, and implantation occurs about 1 wk after fertilization, in the middle of the luteal phase
• Veins are dilated (venous lakes) and thin walled, arteries have thick walls (donut appearance) and spiral throughout endometrium
• Glands enlarge and secrete the glycogen

Question 5

Endometrial changes during menstrual cycle: menses

Answer 5

• In the final days of secretory phase (as CL regresses) there are changes in circulatory pattern of spiral arteries that lead to the sloughing of the functionalis
• As menstrual phase continues there is loss of surface epithelium, hemorrhage from rupture of blood vessels (mostly arteries)
• Stromal cells, epithelial cells, and blood are all released into the uterine lumen

Question 6

Cervix micro

Answer 6

• Cervix is non-contractile composed of DCT and lined by epithelia (squamous and columnar)
• The cervix has many glands that make and secrete cervical mucus
• Just outside of the os the cervical lining is stratified squamous (ectocervix), and there is an abrupt transition to simple columnar (endocervix)
• Cervical mucus composition changes based on phase of menstrual cycle: under E2 stimulation it increases in volume and elasticity until ovulation when it reduces in volume and becomes viscous (so sperm do not pass)
• The quality of cervical mucus is characterized by its ability to fern and is maximal right before ovulation

Question 7

Vagina micro

Answer 7

• Vagina extends from cervix to external genitalia
• Vagina is lined by stratified squamous epithelium and underlying CT
• There are no glands in underlying CT, little contractile tissue
• Vaginal wall thickness sensitive to E2 levels: if E2 levels are low the wall will thin
• Epithelial cells accumulate glycogen for the lactobacilli (they prevent growth of other pathogens)