Uterus, Uterine Tubes and Cervix

Question 1

What do maternal steroids do?

Answer 1

They increase size of new-born uterus. It grows with height during infancy.

Question 2

What is the myometrium dependent on?

Answer 2

It is dependent on estradiol.

Question 3

Which part of the uterus undergoes a greatest increase than the cervix?

Answer 3

The corpus of the uterus

Question 4

Describe the changes of the myometrium throughout life

Answer 4

• Outer muscular myometrium grows gradually throughout childhood.
• It increases rapidly in size and configuration during puberty.
• Changes in size through the cycle. It is capable of vast expansion during pregnancy.

Question 5

Describe the fibres of the uterine walls

Answer 5

Inner layer circular fibres
Middle layer figure of 8 or sprial fibres
Outer layer longitudinal fibres

Question 6

Describe how the endometrium changes in thickness

Answer 6

It is dependent on steroids and responds cyclically to hormone changes.

Question 7

How is the endometrium measured and seen, what is the good “bioassay” of estradiol level?

Answer 7

They can be seen and measured on an ultrasound scan. The good “bioassay” of estradiol level: 7-16 mm.

Question 8

What happens to the endometrium throughout menstruation?

Answer 8

• At menstruation, most of the endometrium is lost.
• After menstruation, the endometrium is a stromal matrix with small columnar cells with glandular extensions that are 2-3 mm thick. The glands are simple and straight.

Question 9

What is the endometrial proliferative phase?

Answer 9

• The stromal cell division, ciliated surface.

- The glands expand and become tortuous, increased vascularity, neoangiogenesis maximal cell division by days 12-14.

Question 10

What stimulates the proliferative phase?

Answer 10

Estradiol from the dominant follicle

Question 11

What happens when the endometrium is >4 mm?

Answer 11

There is induction of progesterone receptors and small muscular contractions of the myometrium

Question 12

What happens in the endometrial secretory phase?

Answer 12

• Happens 2-3 days after ovulation, the gradual rise in progesterone causes a reduction in cell division.
• Glands increase in tortuosity and distend. There is secretion of glycoproteins and lipids.
• Oedema - increased vascular permeability arterioles contract and grow tightly wound.
• The myometrial cells enlarge and movement is suppressed. The blood supply increases.

Question 13

What stimulates the corpus luteum?

Answer 13

LH from the pituitary during luteal phase

Question 14

How and why is human chorionic gonadotrophin (hCG) produces?

Answer 14

It is produced by the fertilised oocyte becoming a blastocyst which releases hCG.
It acts like LH on the LH receptors to ‘rescue’ the CL.

Question 15

What happens in the absence of hCG?

Answer 15

Falling levels of steroid are released from the CL which results in menstruation.

Question 16

Describe the process of menstruation

Answer 16

• Prostaglandin release causes constriction of the spiral arterioles. Hypoxia causes necrosis.
• The vessels dilate and bleeding ensues.
• The proteolytic enzymes released from the dying tissue.
• The outer layer of the endometrium is shed, 50% is lost in 24 hrs, up to 80ml is considered normal.
• The basal layer remains and is then covered by extension of glandular epithelium.
• Estrogen from follicle in next follicular phase starts the cycle off again.

Question 17

How long does bleeding in menstruation normally last?

Answer 17

4+ days

Question 18

Layers of the uterine tube

Answer 18

Mucosa
Muscularis
Serosa

Question 19

What are the mucosa layers in the uterine tube?

Answer 19

1. Secretory
2. Columnar ciliated epithelial
3. Non-ciliated Peg

Question 20

Define the structure of the muscularis of the uterine tube

Answer 20

Inner is circular and outer longituidnal layers.

Has blood vessels and lymphatics

Question 21

What is the serosa of the uterine tube?

Answer 21

Outer layer

Question 22

Describe the changes in the cells lining the uterine tube throughout the cycle

Answer 22

During the follicular/proliferative phase, there is an increase in estradiol. The epithelial cells express high numbers of estrogen receptors and undergo differentiation in response to estradiol and increase in height mid-cycle.
The oocyte can only pass during mid-cycle. The cilia beat and secretory cells are active along with muscle layer contractions all in response to oestrogen.
After a few days of progesterone exposure, the estrogen receptors are suppressed and estrogen effects are overcome causing decrease in height mid-luteal onwards.

Question 23

How long does the egg stay in the tube?

Answer 23

Approximately 5 days

Question 24

Where does fertilisation occur?

Answer 24

In the ampulla

Question 25

What can cause pain, infertility and ectopic pregnancy?

Answer 25

Damage to the lining of the tube by infection, endometriosis, surgery or adhesions may cause blockage or damage to ciliated epithelia.

Question 26

What is the function of the cervix?

Answer 26

It is a muscular structure capable of great expansion.

Question 27

Describe the structure of the endocervical mucosa

Answer 27

• About 3 mm thick
• Lined with a single layer of columnar mucous cells.
• Mucous cells contain tubular mucous glands that empty viscous alkaline mucus into the lumen.

Question 28

What is the function of the viscous alkaline mucus?

Answer 28

• Protective barrier to infection

- allow passage of motile sperm

Question 29

Describe the structure of the ectocervix

Answer 29

Covered with neokeratinised stratified squamous epithelium, resembling the squamous epithelium lining the vagina

Question 30

What happens to the cervix during the follicular pahse?

Answer 30

Estrogen causes change in vascularity of cervix and oedema

Question 31

What happens to the cervix mid-cycle?

Answer 31

The oestrogen levels cause:

• Change in mucous to become less viscous
• Change in mucous composition -> contains glycoproteins that become aligned and form microscopic channels and sperm swim up the channels.

Question 32

What happens to the cervix during the luteal phase?

Answer 32

• Progesterone in luteal phase causes:
• Reduced secretion and viscous mucous (reduced water content)
• Glycoproteins form mesh-like structures that act as a barrier.
• Mechanism of action of oral contraceptives

Question 33

Describe the structure of the vagina

Answer 33

• Thick-walled tube approx 10 cm
• Lined by specialised ‘squamous epithelial’ cells
• Warm damp environment containing glycoprotein

Question 34

The vagina is susceptible to infection. How is this prevented?

Answer 34

• Layers of the epithelial cells shed constantly and ‘flow’ downwards with the secretions
• Secretions are from the cervix and transudation from vaginal epithelium
• Secretions change with cycle and are generally acidic providing anti-microbial protection

Question 35

What lubricates the vagina and what are they homologous to?

Answer 35

The bartholins glands

• located slightly posterior and to the left and right of the opening of the vagina secrete mucus to lubriate
• homologous to bulbourethral glands in males