Uterus, Uterine Tubes & Cervix

Question 1

What are the main changes that occur in your uterus and cervix?

Answer 1

Maternal steroids from mother increase size of new-born uterus.
Grows with height during infancy.
Myometrium dependent on oestradiol.
Corpus of uterus undergoes greater increase in size than cervix.

Question 2

What is the myometrium?

Answer 2

The myometrium is the muscular layer
Outer muscular myometrium grows gradually throughout childhood.
Increases rapidly in size and configuration during puberty.
Changes in size through the cycle. Capable of vast expansion during pregnancy.

Question 3

What are the three layers of the myometrium?

Answer 3

Myometrium has 3 layers:
Inner layer has circular fibres
Middle layer has figure of 8 or spiral fibres
Outer layer has longitudinal fibres 
So it can contract in all directions

Question 4

How does the endometrium change at different times? (Childhood, menstruation, post menses etc.)

Answer 4

Very thin in childhood. Begins to thicken at puberty.
Dependent on steroids and responds cyclically to hormone changes.
Oestrogen principally causes growth in proliferative phase.
Changes in glandular and epithelial cells through the cycle. Progesterone causes mainly differentiation in secretory phase.
At menstruation most of the endometrium is lost.
After menstruation - stromal matrix with small columnar cells with glandular extensions 2-3mm thick glands are simple and straight.

Question 5

What is the endometrial proliferative phase? What happens during this phase?

Answer 5

Proliferative phase (follicular phase of ovary) following menses.
Stimulated by oestrogen from the growing follicle.
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 6

What is the endometrial secretory phase and what happens during this phase?

Answer 6

Secretory phase (luteal phase of ovary) 2-3 days after ovulation, the gradual rise in progesterone causes a reduction in cell division.
Uterine glands increase in tortuosity and distend leading to secretion of glycoproteins and lipids commences.
Oedema increased vascular permeability arterioles contract and grow tightly wound.
Myometrial cells enlarge and movement is suppressed blood supply increases.

Question 7

What happens to the CL if fertilisation occurs?

Answer 7

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 8

What happens in the uterus during menstruation?

Answer 8

Prostaglandin release causes constriction of spiral arterioles.
Hypoxia causes necrosis.
Vessels then dilate and bleeding ensues.
There’s also some 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 9

What are the different components (3) of the uterine tubes?

Answer 9

Mucosa:
Secretory- secretes all kind of growth factors, and nutrients and signalling molecules required for early embryo development
Columnar ciliated epithelial- beat and wave the same as regular cilia in respiratory tract etc.
Non-ciliated Peg- nobody really knows what they do
Muscularis:
Inner circular & outer longitudinal layers.
Blood vessels & lymphatics
Serosa:
Outer layer

Question 10

What are the changes in cells lining the uterine tubes at different stages in the cycle?

Answer 10

With high oestrogen levels, in the first half of the cycle:
Epithelial cells express high numbers of oestrogen receptors & undergo differentiation in response to oestradiol increase in height mid-cycle.
At 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.
In the second half of the cycle, with increased progesterone:
After a few days of exposure to progesterone the oestrogen receptors are suppressed and oestrogen effects are overcome causing decrease in height mid-luteal onwards.

Question 11

What happens to the egg, and where does fertilisation occur?

Answer 11

Egg remains in the tube for approximately 5 days

Fertilisation occurs in ampulla

Question 12

Describe the way you would perform a laparoscopy and dye on a uterus? Why would you do a lap and dye if it is more invasive?

Answer 12

• The woman is lying on her back and we have this uterine cannula going in through the vagina and the cervix and we inject a blue dye into the uterus
  
  • That blue dye fills the uterus and fills the uterine tubes and it should emerge at the fimbril end of the uterine tube next to the ovary if it is patent
  • We look at that through a laparoscope inserted through the stomach, the perineal cavity

If we think there is some other pathology there the laparoscope gives us that visual inspection
There are a few patients that are allergic to the HyCoSy dye

Question 13

What happens when you perform a Hystero Salpingo-contrast Sonography (HyCoSy)?

Answer 13

• You have a catheter going into the cervix, injecting a dye into the uterus
  
  • This dye is ultrasound opaque
  • So you can see the passage of the dye emerging at the fimbril end

Question 14

What is the structure and role of the cervix?

Answer 14

Muscular structure capable of great expansion.
The endocervical mucosa is about 3mm thick, lined with a single layer of columnar mucous cells, containing numerous tubular mucous glands which empty viscous alkaline mucus into the lumen.
- Protective barrier to infection…
- However, it has to allow passage of motile sperm.
The ectocervix is covered with nonkeratinized stratified squamous epithelium, resembling the squamous epithelium lining the vagina.

Question 15

How does the cervix change in the follicular phase?

Answer 15

Oestrogen in the follicular phase causes…
- Change in vascularity of cervix.
- So we get vasodilation and more oedema.
Mid-cycle oestrogen levels cause change in mucous to become less viscous.
- Change in mucous composition.
- Mucus contains glycoproteins, glycoproteins which become aligned and form microscopic channels.
- Sperm swim up the channels!

Question 16

How does the cervix change in the luteal phase?

Answer 16

Progesterone in luteal phase causes…

- Reduced secretion and viscous mucous (reduced water content).
- Glycoproteins now form mesh like structure: acts as barrier to sperm and microorganisms.
- One mechanism of action of oral contraceptives.

Question 17

What is the structure of the vagina and how is infection in there prevented?

Answer 17

Thick-walled tube approximately 10cm.
Lined by specialised ‘squamous epithelial’ cells.
Warm damp environment containing glycoprotein…
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.
Bartholin’s glands located slightly posterior and to the left and right of the opening of the vagina secrete mucus to lubricate the vagina during sexual arousal and are homologous to bulbourethral glands in males