Lecture 4: Uterus and menstural cycle

Question 1

Describe the uterus:

Answer 1

• 7.5cm long pear shaped
• ~10mls luminal volume (non-preg)
• Pregnant uterus ~5L baby, amniotic fluid and placenta (Multiplies with multiple babies)

Question 2

How does the uterus change in pregnancy?

Answer 2

• Initial growth of the uterus is at least partially under the control of estrogen (also prog) as ectopic implantation leads to some of the initial growth.
• Growth is largely due to stretching of existing cells rather than proliferating of cells
• 50um inlength non pregnant 400-600um at term

Question 3

What is the normal orientation of the uterus:

Answer 3

• The uterus is normally ANTEVERTED i.e the top of the uterus faces forwards
• Retroverted uterus occurs in 20-25% of women and is ‘normal’

Question 4

Describe the structure of the uterus:

Answer 4

• The ‘top’ of the uterus is the fundus.
• The bottom of the uterus is continuous with the cervix
• The uterus consists of three main layers:
  1. The serosa (perimetrium)
  2. The muscular myometrium
  3. The inner endometrium

Question 5

Writes some notes on the myometrium:

Answer 5

The myometrium is ~90% of uterus

• Main function of the myometrium is the forceful expulsion of the fetus at parturition
• The myometrium is approximately 10mm thick and this does not change significantly during the menstural cycle

Question 6

insert uterine wall histology

Answer 6

now please

Question 7

What are the uterine/endometrial cycle phases:

Answer 7

Menses (Destruction of functional layer)
Proliferative phase (Repair and regeneration of functional layer)
Secretory phase (secretion of uterine glands)

Question 8

What is the decidua?

Answer 8

specialised layer of endometrium that forms the base of the placenta

Question 9

How does the endometrium change for pregnancy?

Answer 9

In preparation for implantation the endometrium undergoes changes called the decidual reaction.
-> The stroma of the endometrium becomes oedematous, stromal fibroblasts expand and fill with glycogen - an energy source for the embryo

Question 10

Describe the uterine bloody supply:

Answer 10

Uterine artery
Arcuate arteries
Radial Arteries
Spiral arteries (key vessels to supply endometrium and placenta during pregnancy)

Question 11

Describe how uterine spiral arteries change during menses:

Answer 11

Menses

• Spiral artery terminal segments are lost along with the rest of the functionalis layer of the endometrium
• To prevent exsanguination the spiral arteries undergo spasm

Question 12

What happens to the endometrial glands and spiral arteries during the proliferative phase:

Answer 12

Spiral arteries and endometrial glands grow very rapidly

- Since they grow faster than the surrounding stromal the arteries develop into spring-like coils

Question 13

How long is the menstural cycle?

Answer 13

28 days is the average, but, varies considerably with age

Question 14

Which is longer, the follicular/proliferative phase or the luteal/secretory phase?

Answer 14

Follicular/proliferative phase is longer and more variable in length than the luteal/secretory phase

Question 15

What is evident in the mid proliferative phase under histology:

Answer 15

Stromal oedema

Mitotic bodies

Question 16

What is evident in the early luteal phase under histology:

Answer 16

Stromal oedema
Tortuous glands
Basal vaculotation
Glandular secretions

Question 17

What is the role of estrogen in the uterus?

Answer 17

Estrogen stimulates:

• Epithelial and stromal cell proliferation
• Stromal oedema
• Glandular secretions (serous)
• Synthesis of intracellular progesterone receptors (estrogen priming)
• Myometrial activity

Question 18

What is the role of progesterone in the uterus:

Answer 18

Progesterone stimulates:

• Glandular secretions (thick) in luteal phase (against an estrogen background)
• Strom cell differentiation

Progesterone inhibits:
- Myometrial activity

Question 19

Is the decidual reaction required for implanation?

Answer 19

This is not true:

• i.e ectopic pregnancy, most common in fallopian tubes

Question 20

What is endometriosis?

Answer 20

• Ectopic endometrium
  = Chronic pelvic pain
  = assc. with infertility

Essentially endometrial tissue outside of the uterus often on the ovaries

Question 21

What are the causes of endometriosis?

Answer 21

Not really known

• Retrograde mensturation
• transport of endometrial cells via blood or lymphatics
• Growth of endometrial-like tissue from stem cells

Question 22

Describe the structure of the cervix:

Answer 22

Endocervix

• Columnar epithelium
• Glands, Crypts
• Fibrous stroma, few SM

Juntional zone (HPV love these cells)
Transitional zone

Ectocervix
- Stratified squamous epithelium

Question 23

Write some notes on cervical mucous:

Answer 23

Changes with cycle:

• Volume
• Viscosity
• Threadability - Spinnbarkeit

Question 24

Insert the diagram of the cervical mucous and cycle features

Answer 24

Slide 38

Question 25

Describe how cervical mucous changes over the cycle and what is responsible for this:

Answer 25

E2 increases volume, and stimulates clear watery mucous with high threadability (spinnbarkeit) that is receptive to sperm. Mucous contains channel for sperm access.

P4 stimulates highly viscous and cross linked mucous that is a barrier to sperm penetration

Cervical mucus regulates the ability of sperm to transverse the cervix.