Uterus, uterine tubes and cervix

Question 1

At what time does the embryo implant into the uterus?

Answer 1

After 6 days the embryo will enter into the uterus, lined with a receptive lining for implantation of the embryo called the endometrium.

Question 2

What is the muscular layer of the uterus called?

Answer 2

Myometrium

Question 3

What is the outside of the uterus called?

Answer 3

The outside of the uterus is the perimetrium

Question 4

Describe the size of the uterus when pregnant and why it is that size

Answer 4

• During pregnancy there is lots of oestrogen and progesterone that results in an enlarged uterus. It does not go back to its normal size.
• Uterus enlarges after pregnancy.

Question 5

Why is the uterus larger in a newborn than in an infant?

Answer 5

The uterus in a newborn is larger than it is at 4 years old. This is because when the baby is in the womb, she is exposed to a huge amount of oestrogen from the mother. This causes proliferation of the baby’s uterus.

Question 6

What hormone influences the myometrium?

Answer 6

E2

Question 7

Describe the growth of the myometrium and what hormone does it respond to?

Answer 7

• 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.
• Grows in response to oestrogen

Question 8

What are the 3 layers of fibres of the myometrium?

Answer 8

inner layer in circles, middle layer in a figure of 8 and an outer layer arranged longitudinally. So the muscle can contract in every direction

Question 9

When does the endometrium grow?

What is it dependant on and what does it respond cyclically to?

Does it grow in the proliferative phase and what hormone causes this?

What changes throughout the cycle?

What does progesterone cause?

What happens at menstruation?

Answer 9

• Very thin in childhood. Begins to thicken at puberty.
• Dependent on steroids and responds cyclically to hormone changes.
• Estrogen principally causes growth in proliferative phase. Can be seen and measured on an ultrasound scan. Good ‘bioassay’ of estradiol level…7-16mm.
• After ovulation we get progesterone dominating the cycle.
• Proliferation of spiral of blood vessels providing a large surface area for exchange.
• Uterine glands become secretory: glucose and hormones
• 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.
• Replaced every month

Question 10

Describe the endometrial proliferative phase (follicular phase of the ovary)

When does it occur?

What events occur in this phase?

Answer 10

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

Progesterone levels have dropped, corupus luteum has died, endometrium has been lost, breaks off hypothalamus, getting a rise in FSH and produce oestrogen, select a dominant follicle. The rise in oestrogen causes proliferation of the endometrium. Occurs during the first half of the cycle

• 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 11

Describe what happens in the Endometrial secretory phase (after ovulation) (follicular luteal phase)

Answer 11

• Secretory phase (luteal phase of ovary) 2-3 days after ovulation, the gradual rise in progesterone causes a reduction in cell division.
• Glands increase in tortuosity and distend…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 12

Describe the regression of the corpus luteum

Answer 12

• 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. This stays alive, continues to produce progesterone, which feedbacks negatively so theres no follicle recruitment.
• In the absence of this, falling levels of steroid from the CL results in menstruation.

Question 13

What happens in Menstruation?

Answer 13

• Corpus luteum dies because of no LH, progesterone levels drop which causes 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.
• Estrogen from follicle in next follicular phase starts cycle off again.

Question 14

What is found in the ampulla, isthmus and intermural region?

Answer 14

• In the ampullary there is a huge surface area for secretory cells
• In the isthmus there is an inner circular layer and longitudinal muscle – containing blood vessels and lymphatics. This allows it to contract in longitudinal and circular directions.
• In the intermural regions there is little mucosa and very muscular.

Question 15

What are the 3 types of mucosa cells?

Answer 15

1. Secretory
2. Columnar ciliated epithelium - waft egg and sperm along
3. Non-ciliated Peg

Question 16

What is the muscularis and Serosa?

Answer 16

Muscularis = inner circular and outer, longitudinal layers, blood vessels and lymphatics

Serosa = outer layer

Question 17

Describe changes in the cells lining the uterine tubes in the proliferative, ovulatory and secretory phase

Answer 17

• Epithelial cells express high numbers of oestrogen receptors & undergo differentiation in response to estradiol increase in height mid-cycle.
• 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.
• 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.

Question 18

Have a look at inside the uterine tube

Answer 18

On image

Question 19

What effect does chlamydia and endometriosis have?

Answer 19

Damage to the lining of the tube by infection (chlamydia), endometriosis (cells from the endometrium leave the endometrium and become lodged in other places in the pelvis they implant and grow there and continue to respond to oestrogen and progesterone as they would in the endometrium they proliferate under oestrogen and differentiate with progesterone and they bleed once the corpus luteum dies (can occur inside the uterine tube), surgery or adhesions may cause blockage or damage to ciliated epithelia, resulting in:
• pain
• infertility
• ectopic pregnancy

Question 20

How do we check the patency of the uterine tube?

Answer 20

You can check the patency of the uterine tubes. There are two ways to do this:

1. Laparoscopy and dye – we have a uterine canula through the vagina and cervix and inject a blue die into the uterus. This fills up the uterus and passes through the uterine tube up to the fibrrila end next to the ovary. If the uterine tube is blocked we wont see any
2. Hystero Salpingo-contrast Sonography (HyCoSy) – die is ijected into the uterus, this an an opaque ultrasound die that can be monitored.

We might still want to use lapaoscropy because there might be additional pathologies – need to look in the pelvis. You can be allergic to the HyCoSy die.

Question 21

What is the function of the endocervical mucosa?

Answer 21

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 22

Describe the changes that occur in the cervix in the follicular phase and mid-cycle

Answer 22

Estrogen in the follicular phase causes…
• Change in vascularity of cervix and oedema. We get vasodilation and more oedema.

Mid-cycle estrogen levels cause changes in mucous to become less viscous.
• Change in mucous composition.
• Mucus contains glycoproteins which become aligned and form microscopic channels.
• Sperm swim up the channels!

Question 23

What are the changes that occur in the cervix in the luteal phase?

Answer 23

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 microogranisms.
• One mechanism of action of oral contraceptives.

Question 24

What cells are found in the vagina?

What type of environment is in the vagina?

Answer 24

Lined by specialised ‘squamous epithelial’ cells.

Warm damp environment containing glycoprotein…

Question 25

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

Answer 25

• 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.