Uterus, Uterine Tubes and Cervix

Question 1

What are the three layers of the uterus?

Answer 1

• The inner walls of the uterus are lined by the endometrium
• The middle layer is the muscular layer called the myometrium
• The outer layer is called the perimetrium

Question 2

What is the difference between the uterus size of a new born baby and a four year old? And why?

Answer 2

• The uterus of a new born baby is significantly bigger than the uterus of a four-year-old.
• This is because the myometrium responds to maternal steroid oestrogen increasing the size of new-born uterus.
• The uterus grows with height during infancy

Question 3

What hormone is the myometrium dependant on?

Answer 3

Oestradiol

Question 4

Which part of the uterus undergoes a greater increase in size than the cervix?

Answer 4

Corpus of the uterus

Question 5

Describe the changes of the myometrium throughout life

Answer 5

• The outer muscular myometrium will grow gradually throughout childhood
• It increases rapidly in size and configuration during puberty
• Changes in the size throughout the cycle and is capable of vast expansion during pregnancy

Question 6

What are the different fibres of the myometrium?

Answer 6

• Inner circular fibres
• Middle figure of 8 fibres
• Outer longitudinal fibres (allow for large expansion during pregnancy)

Question 7

Describe how the endometrium will change in thickness

Answer 7

• Thin during childhood, thickens during puberty
• Dependant on steroids and responds cylically to hormone changes

Question 8

What happens to the endometrium throughout menstruation?

Answer 8

• Changes in glandular and epithelial cells through cycle.
• At menstruation most of the endometrium is lost (if no pregnancy corpus luteum dies and the endometrium is lost)
• After menstruation - stromal matrix with small columnar cells with glandular extensions 2-3mm thick
  
  • The glands are simple and straight

Question 9

What is the endometrial proliferative phase?

Answer 9

• Reffered to as the follicular phase in the ovaries
  
  • Proliferative phase is stimulated by oestradiol from the dominant follicle
  • Stromal cell division, ciliated surface
  • The glands expand and become tortuous, increased vascularity, neoangiogenesis maximal cell division by days 12-14
  • When endometrium is greater than 4mm induction of progesterone and small muscular contractions of the myometrium

Question 10

What stimulates the proliferative phase?

Answer 10

Oestradiol from the dominant follicle

Question 11

What happens when the endometrium is greater than 4mm?

(Endometrial Proliferative Phase)

Answer 11

• Induction of progesterone receptors
• Small muscular contractions of the myometrium

Question 12

When does the endometrial secretory phase come in?

Answer 12

2-3 days after ovulation (around the stage of the luteal phase of the ovary)

Question 13

Describe the endometrial secretory phase

Answer 13

• Gradual rise in progesterone causes reduction in cell division
• Progesterone acts on endometrium and makes it differentiate
  
  • Allows glands to increase in tortuosity and distension, secretion of glycoproteins and lipids
• Oedema, increased vascular permeability arterioles contract and grow tightly wound.
• Myometrial cells enlarge and movement is suppressed
• blood supply increases.

Question 14

What stimulates the corpus luteum during the luteal phase?

Answer 14

LH from the pituitary

Question 15

What rescues the corpus luteum is a female becomes pregnant?

Answer 15

• Fertilised oocyte will form a blastocyst (differentiating cells trophoblast, blastocoel and embryoblast (inner cell mass)) which will produce human chorionic gonadotrophin (hCG)
  
  • hCG will act like LH on the LH receptor and rescue the corpus luteum

Question 16

What happens to the corpus luteum if no hCG is produced?

Answer 16

• Falling levels of steroid from the corpus luteum result in menstruation
  
  • (Reminder: less negative feedback of progesterone on HPG axis meaning increased FSH levels, selection of dominant follicle, follicles start to produce estradiol)

Question 17

Describe the process of menstruation?

Answer 17

• 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 18

How long does bleeding in menstruation normally last?

Answer 18

4+ days

Question 19

What are the layers of the uterine tube?

Answer 19

• Mucosa contains three types of cells
  
  • Secretory, columnar ciliated epithelial cells, non ciliated peg cells
• Muscularis
• Serosa - Outer protective layer

Question 20

What are in the mucosa layers of the uterine tube?

Answer 20

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

Question 21

Define the structure of the muscularis of the uterine tube?

Answer 21

• Inner is circular and outer longitudinal layers
• Has blood vessels and lymphatics

Question 22

What is the serosa of the uterine tube?

Answer 22

Outer Layer

Question 23

What are the changes in the cells lining the uterine tube throughout the menstrual cycle

Answer 23

• During the follicular/proliferative phase there is an increase in estradiol
• Epithelial cells express high number of oestrogen receptors and undergo differentiation in response to estradiol and increase in height mid cycle
• The oocyte can only pass mid cycle
• Cilia beat and secretory cells are active along with muscle layer contractions - responding to oestrogen
• After being exposed to progesterone, oestrogen receptors are supressed and there is a decrease in height mid luteal onwards

Question 24

How long does the egg stay in the tube?

Answer 24

Approximately 5 days

Question 25

Explain how oestrogen and progesterone have opposing effects

Answer 25

* Whilst progesterone is differentiating the endometrium it is dedifferentiating the uterine tube * Whilst oestrogen is causing proliferation of the endometrium at the start of the cycle it is causing differentiation of the uterine tube

Question 26

What can cause pain, infertillity and ectopic pregnancy?

Answer 26

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

Question 27

How can we check if the uterine tubes are functioning properly?

Answer 27

1. **_Laparoscopy and dye_** - blue dye should appear at fimbrial ends, if it doesn't appear at the ends then the tube is blocked 2. **_Hystero Salpingo-contrast sonography:_** ultrasound probe is used to see if the dye also appears at the fimbrial ends (less invasive)

Question 28

What is the function of the cervix?

Answer 28

Muscular structure capable of expansion

Question 29

What does endocervical mucosa do?

Answer 29

* Lined with a single layer of **columnar mucous cells** * contain numerous tubular mucous glands that **empty viscous alkaline mucus into the lumen**

Question 30

What is the function of the viscous alkaline mucus secreted by the endocervical mucosa?

Answer 30

* protective barrier to infection... * however has to allow passage of motile sperm

Question 31

What is the purpose of the grooves in the cervix?

Answer 31

Trap sperm which provides reservoir for slow release of sperm

Question 32

What is the ectocervix?

Answer 32

covered with **nonkeratinized stratified squamous epithelium**, resembling the squamous epithelium lining the vagina.

Question 33

What happens to the cervix during the follicular phase?

Answer 33

**Estrogen in the follicular phase causes…** * change in vascularity of cervix and oedema

Question 34

What happens to the cervix mid-cycle?

Answer 34

**Mid-cycle estrogen levels cause change in mucous to become less viscous.** * change in mucous composition * contains glycoproteins glycoproteins which become aligned and form microscopic channels andsperm swim up the channels!

Question 35

What happens to the cervix during the luteal phase?

Answer 35

**Progesterone in luteal phase causes…** * Reduced secretion and viscous mucous (reduced water content) * Glycoproteins now form mesh like structure: acts as barrier * One mechanism of action of oral contraceptives.

Question 36

What is the structure of the vagina?

Answer 36

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

Question 37

How is infection of the vagina prevented?

Answer 37

* 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

Question 38

What lubricates the vagina and what are they homologous to?

Answer 38

* ***BARTHOLINS GLAND*** * located posterior to left and right side of vaginal opening * Secrete mucus to lubricate vagina * Homologous to **bulbourethral glands in males**