Uterus, uterine tubes and cervix

Question 1

What’s the difference between the myometrium and endometrium?

Answer 1

• endometrium is renewable every month - the layer shed during menses - mucous membrane that lines the uterus
• on the outside is the muscular myometrium, several layers

Question 2

What hormone is the myometrium dependent on?

Answer 2

oestraidol

Question 3

What undergoes greater increase in size than the cervix?

Answer 3

corpus of uterus

Question 4

Describe growth of myometrium through life and pregnancy

Answer 4

• outer muscular myometrium grows gradually throughout childhood
• increases rapidly in size + configuration during puberty
• changes in size through the cycle
• capable of vast expansion during pregnancy

Question 5

Describe the structure of the myometrium

Answer 5

• inner layer - circular fibres
• middle layer - figure of 8 or spiral fibres
• outer layer - longitudinal fibres

Question 6

The endometrium is dependent on steroids, it responds cylically to hormone changes. Can be seen + measured on an US scan. Describe the growth of the endometrium through childhood, puberty + menstruation

Answer 6

• very thin in childhood
• begins to thicken at puberty
• changes in glandular + epithelial cells through cycle
• at menstruation most of endometrium is lost

Question 7

What is the histological structure of the endometrium after menstruation?

Answer 7

• stromal matrix
• with small columnar cells
• with glandular extensions 2-3mm thick
• glands are simple + straight

Question 8

Describe the structural characteristics of the endometrial proliferative phase and what it is stimulated by?

Answer 8

• by oestradiol from the dominant follicle
• stromal cell divison, ciliated surface
• glands expand + become tortuous
• increased vascularity
• neoangiogenesis
• maximal cell divison by days 12-14

Question 9

What happens when the endometrium is >4mm thick?

Answer 9

• induction of progesterone receptors
• small muscular contractions of the myometrium

Question 10

What phase follows the endometrial proliferative phase?

Answer 10

Endometrial secretory phase (luteal phase of ovary)

Question 11

When is the endometrial secretory phase?

Answer 11

2-3 days after ovulation

Question 12

What happens in the endometrial secretory phase?

Answer 12

• gradual rise in progesterone causes a reduction in cell divison
• glands increase in tortuosity + distend
• secretion of glycoproteins + lipids commences
• oedema, inc vasc perm, arterioles contract + grow tightly wound
• myometrial cells enlarge + movement is suppressed
• blood supply increases

Question 13

What is the corpus luteum stimulated by?

Answer 13

• by LH from pituitary during luteal phase

Question 14

What does the fertilised oocyte become and what does it produce?

Answer 14

• blastocyst
• produces hCG
• acts like LH ie. on LH receptor, and ‘rescues’ the CL
• in absence of this, falling levels of steroid from CL results in menstruation

Question 15

Describe the events of menstruation

Answer 15

• prostaglandin release -> constriction of spiral arterioles
• hypoxia -> necrosis
• vessels then dilate + bleeding ensues
• proteolytic enzymes released from 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 + is covered by extension of glandular epithelium
• oestrogen from follicle in next follicular phase starts cycle off again

Question 16

How does the mucosa differ at various points across the uterine tube?

Answer 16

• intramural - secretory
• isthmus - columnar ciliated epithelial
• ampullary - non-ciliated peg

Question 17

Where does fertilisation occur in the uterine tube?

Answer 17

Ampulla

Question 18

Describe changes undergone by cells lining the uterine tubes over the cycle - when can the oocyte pass here?

Answer 18

• epithelial cells undergo differentiation in response to oestradiol increase in height mid-cycle
• oocyte can only pass during mid-cycle
• after a few days of exposure to progresterone, oestrogen effects are overcome causing decrease in height mid-luteal onwards

Question 19

How is the egg transported along the uterine tube?

Answer 19

• by beating of cilia, stimulated to grow by oestrogen
• rapid contractions of muscular layer caused by oestrogen

Question 20

There are high number of oestrogen receptors present in the follicular phase. How are these receptors suppressed?

Answer 20

• oestrogen receptors suppressed by progresterone
• by mid-luteal phase, even if an egg was released it would be unable to pass as there is no transportation of the egg at this point

Question 21

How long does the egg remain in the tube for?

Answer 21

5 days approx

Question 22

Damage to lining of the tube by infection, endometriosis, surgery or adhesions may cause blockage or damage to ciliated epithelia, resulting in what 3 things?

Answer 22

• pain
• infertility
• ectopic pregnancy

Question 23

Describe the basic/general structure of the cervix

Answer 23

• muscular structure capable of great expansion
• mucosa 2-3mm thick

Question 24

The cervix has many secretory glands producing mucous. What is this for?

Answer 24

• protective barrier to infection
• however has to allow passage of motile sperm

Question 25

What happens to the cervix in the follicular phase? How do these changes accompany/help sperm?

Answer 25

• oestrogen in the follicular phase causes change in vascularity of cervix + oedema
• mid-cycle oestrogen levels cause change in mucous to become less viscous.
  
  • change in mucous composition
  • contains glycoproteins
  • glycoproteins become aligned + form microscopic channels
  • sperm swim up channels!

Question 26

What happens to the cervix in the luteal phase?

Answer 26

progesterone in luteal phase causes…

• reduced secretion + viscous mucous
• glycoproteins now form mesh like structure
• -> acts as barrier
• one mechanism of oral contraceptives

Question 27

Describe the structure of the vagina

Answer 27

• thick walled tube approx 10cm
• lined by specialised ‘squamous epithelial’ cells
• warm damp environment

Question 28

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

Answer 28

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