Lecture 4: Uterus and Menstrual cycle

Question 1

How does the uterus able to go from 10mls in non pregnant to 5L in pregnant or even 20L after multiple pregnancies? - What controls the growth of the uterus?

Answer 1

The initial growth of the uterus in pregnancy is partially controlled by estrogen (also progesterone) as ectopic implantation leads to some initial growth

The growth is mostly stretching of existing cells rather than proliferation so it can revert to similar to original state

Question 2

What is the tissue layers of the uterus and its most common position

Answer 2

1. serosa (perimetrium)
2. myometrium (muscle): for expulsion of fetus at birth
3. endometrium
   a) Basilar layer (unchanging- contains stem cells for regeneration of func layer
   b) Functional layer (affected by menstrual cycle to proliferate and then be shed during menses )

Question 3

What is the Decidua and what is the decidual reaction. Is it required for implantation

Answer 3

Decidua= what endometrium is called in pregnancy
Decidual reaction is in preparation for implantation of embryo invading the wall of the endometrium/decidua.
- stroma of endometrium becomes oedematous
-stromal fibroblasts expand and fill with glycogen: energy source for embryo

It is not required for implantation bc ectopic implantation happens anywhere in abdo cavity

Question 4

What is the main blood supply to the endometrium and placenta (in pregnancy) and how does this change during menstrual cycle

Answer 4

Spiral arteries: (from uterine artery->arcuate artery->radial artery)
In menses the spiral artery terminal segments are lost along with functional layer. the spiral arteries undergo spasm to prevent exsanguination.

In proliferative phase the spiral arteries (and endometrial glands) grow faster than the surrounding stroma, developing into spring like coils which can be stretched out in pregnancy as uterus stretches out.

Question 5

How does menstrual cycle length vary over time? which phase is more constant

Answer 5

Varies between 20-35 days. 28 days most common but 29.1 is the mean. Tends to longer in younger women and shorter as one gets older

Follicular/proliferative phase is longer and more variable in length than luteal/secretory phase (under control of progesterone with only one source (1 corpus luteum) vs oestrogen has variable sources : # of follicles activated, fat etc.

Question 6

What will be some main histological changes of endometrium in proliferative vs secretory vs menstruation

Answer 6

Proliferative: little stromal oedema, straight looking glands, not a lot of secretion, some mitotic bodies

Secretory: Tortuous glands, basal vaculoation, glandular secretion, more stromal oedema towards end of luteal phase

Menstruation: little secretions, heavy neutrophil infiltration against infection, pseudo-decidual reaction around arterioles- fibroblasts with oedema.

Question 7

Compare the role of E2 vs P2 in the uterus

Answer 7

E2 stimulates

• epithelial, stromal, spiral artery proliferation
• stromal oedema
• serous glandular secretions
• synthesis of intracellular P2 receptors - known as estrogen priming
• myometrial activity

P2 stimulates

• thick glandular secretions
• stromal cell differentiation (decidual reaction)
• inhibition of myometrial activity

Question 8

How often are smears for cervical cancer conducted

Answer 8

every 3 years from age of 20 until they turn 70

Question 9

Describe the histology of the cervix - endo vs ectocervix

Answer 9

Endo: columnar epithelium with glands and crypts.
Stroma is fibrous with few SM cells

Ecto: stratified squamous epithelium

Question 10

How does cervical mucus change with E2 and P2- volume, viscosity and threadability

Answer 10

E2:

• increases volume
• clear watery mucous with high threadability
• receptive to sperm and contains channels for sperm access

P2:

• stimulates highly viscous and cross-linked mucous
• barrier to sperm penetration