7- Uterus, Uterine Tubes And Cervix

Question 1

Describe how the changes that occur in the uterus and cervix from birth occur

Answer 1

The maternal steroids (oestrogen) increase the size of a new-born baby’s uterus. It grows with height during infancy.

The myometrium is dependant on oestradiol. The corpus of the uterus undergoes a greater increase in size than the cervix.

Question 2

Describe the structure of the myometrium

Answer 2

The outer, muscular myometrium grows gradually throughout childhood. It increases rapidly in size and configuration during puberty.
There are changes in size throughout the cycle. It is also capable of vast expansion during pregnancy.

Inner Layer: circular fibres
Middle Layer: figure-8/spiral fibres
Outer Layer: longitudinal fibres

Question 3

Describe the structure of the endometrium

Answer 3

It is very thin in childhood, and begins to thicken at puberty.

It is dependant on steroids; it responds cyclically to hormone changes (oestrogen).

There are changes in the glandular and epithelial cells through the cycle. At menstruation, most of the endometrium is lost.

After menstruation, there is still the stromal matrix with small columnar cells with glandular extensions that are 2-3mm thick. The glands are simple and straight.

Question 4

What are the effects of oestrogen and progesterone on the endometrium of the uterus?

Answer 4

• Oestrogen principally causes growth in proliferative phase.
• Progesterone causes mainly differentiation in secretory phase.

Question 5

What is the proliferative phase in the endometrium, when does it occur and what is it stimulates by?

Answer 5

• Its the follicular phase of the ovary and it occurs after menses
• It is stimulated by oestrogen from the growing follicle

Question 6

What happens during the endometrial proliferative phase?

Answer 6

There is stromal cell division, ciliated surface. Glands expand and become tortuous, increased vascularity, neoangiogenesis
maximal cell division by days 12-14.

When endometrium >4mm induction of progesterone receptors and small muscular contractions of the myometrium.

Question 7

What is neoangiogenesis?

Answer 7

The development of new blood vessels from the pre-existing vasculature.

Question 8

What is the endometrial secretory phase and when does it occur?

Answer 8

• Its the luteal phase of the ovary
• It occurs 2-3 days after ovulation

Question 9

What happens during the endometrial secretory phase?

Answer 9

The gradual rise in progesterone causes a reduction in cell division

The glands increase in tortuosity and distend; the secretion of glycoproteins and lipids commences.

Oedema (increased vascular permeability) causes the arterioles to contract and grow tightly wound.

The myometrial cells enlarge and movement is suppressed as the blood supply increases.

Question 10

Describe the regression of the corpus luteum

Answer 10

The corpus luteum stimulated by LH from pituitary during luteal phase.

The fertilised oocyte becomes a blastocyst and produces human chorionic gonadotrophin (hCG) which acts like LH ie on LH receptor, and ‘rescues’ the CL.

In the absence of this, falling levels of steroid from the CL results in menstruation.

Question 11

What happens during menstruation?

Answer 11

• Prostaglandin release causes constriction of spiral arterioles.
• Hypoxia causes necrosis.
• Vessels then dilate and bleeding ensues.
• Proteolytic enzymes released from the dying tissue.
• Outer layer of endometrium shed, 50% lost in 24hrs, up to 80ml is considered normal. Bleeding normally lasts 4+ days.
• Basal layer remains and is then covered by extension of glandular epithelium.
• Oestrogen from follicle in next follicular phase starts cycle off again.

Question 12

What are the 3 sections of the uterine tubule?

Answer 12

1- The intramural portion
2- The isthmus
3- The ampulla (site of fertilisation)

Question 13

What are the 3 types of cells in the mucosa?

Answer 13

1- Secretory cells
2- Columnar ciliated epithelial cells
3- Non ciliated peg cells

Question 14

What are the muscularis and serosa of the uterine tube?

Answer 14

MUSCULARIS:
- comprised of inner circular and outer longitudinal layers
- contains blood vessels and lymphatics

SEROSA:
- the outer layer

Question 15

What changes occur in the cell lining of the uterine tubes during the phases of the menstrual cycle?

Answer 15

Follicular/Proliferative Phase:
- Epithelial cells express high numbers of oestrogen receptors & undergo differentiation in response to oestradiol increase in height mid-cycle.

Ovulation:
- Oocyte can only pass down the tube during mid-cycle. Cilia beat and secretory cells are active along with muscle layer contractions, all in response to oestrogen.

Luteal/Secretory Phase:
- After a few days of exposure to progesterone the oestrogen receptors are supressed and oestrogen effects are overcome causing decrease in height mid-luteal onwards.
- cells become undifferentiated

Question 16

Where does fertilisation occur?

Answer 16

In the ampulla
The egg remains in the tube for approximately 5 days.

Question 17

What can cause damage to the lining of the tube and what can it cause and what does this result in?

Answer 17

Damage to lining of the tube can be caused by:
- infection
- endometriosis
- surgery or adhesions
and it may cause blockage or damage to ciliated epithelia, which results in…
- pain
- infertility
- ectopic pregnancy

Question 18

How can tubal patency be tested?

Answer 18

Laparoscopy and dye:
- blue dye is injected into uterus through the cervix
- if the tube is patent the dye should move through the tube and into the fimbral end of the tube near the ovary
- advantage: good to look at other pathologies
- disadvantage: invasive

Hystero Salpingo-contrast Sonography (HyCoSy)
- canula inserted into the cervix with dye and is injected into the uterus
- dye is monitored in ultrasound
- dye should be present in the fimbral end of the uterine tube
- advantage: less invasive
- disadvantage: patients may be allergic to dye

Question 19

Describe the structure of the cervix

Answer 19

It is a muscular structure between the vagina and uterus, capable of great expansion.

The endocervical mucosa is about 3mm thick, lined with a single layer of columnar mucosa cells. These contain numerous tubular mucous glands which empty viscous alkaline mucus into the lumen.

It’s a protective barrier to infection; however, it has to allow the passage of motile sperm.

The ectocervix is covered with nonkeratinized, stratified, squamous epithelium, resembling the squamous epithelium lining the vagina.

Question 20

Describe the changes that occur in the cervix during the follicular phase

Answer 20

The oestrogen in the follicular phase causes a change in vascularity (more vasodilation) of the cervix, and oedema (more oedema).

The mid-cycle oestrogen levels cause changes in mucous to make it less viscous:
- a change in mucous composition
- mucus contains glycoproteins which become aligned and form microscopic channels, up which sperm swim!

Question 21

Describe the changes that occur in the cervix during the luteal phase

Answer 21

Progesterone (increase in progesterone) in the luteal phase causes:
- reduced secretion and viscous mucous (reduced water content)
- glycoproteins now form a mesh-like structure: acts as a barrier (harder for sperm to swim through)
- one mechanism of action of oral contraceptives

Question 22

Describe the structure of the vagina

Answer 22

It is a thick-walled tube, approximately 10 cm long. it is lined by specialised ‘squamous epithelial’ cells. It is a warm, damp environment containing glycoproteins.

Bartholins glands are located slightly posterior and to the left and right of the opening of the vagina. They secrete mucus to lubricate the vagina and are homologous to the bulbourethral glands in males.

Question 23

What prevents the vagina from infections?

Answer 23

The vagina is susceptible to infection, which is prevented by…
- Layers of epithelial cells shed constantly and ‘flow’ downwards with the secretions.
- Secretions are from cervix and transudation from vaginal epithelium.
- Secretions change with cycle and are generally acidic providing anti-microbial protection.