Uterus, Uterine Tubes & Cervix Flashcards
where does fertilisation occur? + where does embryo spend first week
What changes does cervix undergo thru menstrual cycle?
Fertilisation occurs in the ampulla region of uterine tube
- embryo spends first week of life within uterine tube- v protected, specialised environment
cervix - sometimes it’s penetrable to sperm, whilst other times the cervical mucus creates an impenetrable barrier
Describe the changes that occur in the uterus in:
neonate, infancy, puberty, pregancy, after menopause
what grows in size more - corpus or cervix?
Uterus= responsive to steroids, so neonatal uterus (exposed to maternal steroids) is larger than toddler uterus (no steroid exposure)
As height increases during infancy, so does uterus size. At puberty, oestrogen is produced–> uterus grows rapidly
Pregnancy= myometrium is affected by high oestradiol - hence nulliparous< parous uterus (uterus doesn’t quite return to its original size).
After menopause, lower oestrogen levels shrink the uterus again
Note - Corpus of uterus undergoes greater increase in size than cervix.
The uterus consists of 3 layers- what are these layers?
3 layer of myometrium?
Outer perimetrium, middle myometrium & inner endometrium
Myometrium can vastly expand during pregnancy and has 3 layers:
- Inner layer=circular smooth muscle fibres.
- Middle layer = spiral fibres.
- Outer layer= longitudinal fibres
The endometrium is dependent on steroids + responds to hormone changes in the menstrual cycle. Describe the changes during these phases:
Proliferative, ovulatory, menstruation
During proliferative phase increased oestrogen levels cause growth of the endometrium- seen on an USS. Good ‘bioassay’ of oestradiol level- 7-16mm
After ovulation, CL produces pg- some growth, but mainly differentiation of the endometrium
In mensturation, endometrium is lost. Left w a stromal matrix w small columnar cells w 2-3mm thick glandular extensions. These give rise to the new cells in the proliferative stage
What is the proliferative phase stimulated by?
What are 3 things which happen in the proliferative phase?
what happens when endometrium is over 4mm thick?
Estrogen from growing follicle, which also causes proliferative phase and endometrium proliferation
- stromal cell division & differentiation, giving rise to a ciliated surface
- Glands expand & become tortuous
- neoangiogenesis increases Endometrium vascularity
There is maximal cell division by 12-14 days
When endometrium >4mm thick, there is induction of pg receptors & small muscular contractions in myometrium
4 things which happen during endometrial secretory phase?
Secretory phase (luteal phase) 2-3 days after ovulation:
- CL releases pg, which inhibits mitosis
- Glands increase in tortuosity & distend–> secretion of glycoproteins & lipids.
- Increased vascular permeability & arteriole contraction leads to oedema, whilst tortuous vessels also enlarge to increase SA
- Myometrial cells enlarge, & their movement is suppressed & the blood supply increases
This all makes the endometrium more receptive to implantation
3things which happen to endometrium during menstruation?
what remains after menstruation?
Prostaglandin release constricts spiral arterioles, leading to hypoxia -> necrosis. Vessels then dilate & bleeding ensues.
Proteolytic enzymes released from dying tissue break down endometrium
Outer layer of endometrium shed, 50% lost in 24hrs, up to 80ml= normal.
Basal layer remains + is covered by an extension of glandular epithelium.
Describe the uterine tubes:
4 regions of Uterine tubes, 3 layers of tube, how do layers change as you get closer to the uterus?
- 4 regions: fimbriae, infundibulum, ampulla, isthmus
- Mucosa = inner layer of tube wall.
- The muscularis= middle layer. Has an inner circular + outer longitudinal layer, w blood vessels & lymphatics. There is some peristaltic activity in the uterine tubes.
- Serosa = protective outer wall layer
As we get closer to the uterus, the muscularis gets thicker, whereas mucosal layer gets thinner
The mucosa of the uterine tubes contains 3 cell types. Distinguish between these cell types
Ciliated columnar epithelial cells: have villi that help to push the oocyte along the tube
Secretory cells: secrete everything the embryo needs + responds to embryo signals to create the right environment for it
Non-ciliated peg cells: look like pegs driven between the other cell types. Undifferentiated cells that can differentiate into the other cell types
how do cells change during follicular phase VS mid cycle vs luteal phase?
Follicular/proliferative phase: epithelial cells express many oestrogen receptors & differentiate in response to E2.
The cells express cilia, so lengthen
Mid cycle: the cilia beat + secretory cells are active. The muscularis also contracts (peristalsis).
Luteal/secretory phase: pg exposure suppresses oestrogen receptors - so cells shorten from the mid-luteal phase onwards
How long does the ovulated oocyte stay in the uterine tube?
What happens if there is damage to the tube?
The ovulated oocyte remains in uterine tube for ~5 days, in which time it may meet a sperm
Damage to the lining of the uterine tube occurs by:
infection (mainly chlamydia)
endometriosis, surgery or adhesions (e.g. following pelvic inflammatory disease)
Damage may cause blockage or damage to ciliated epithelia -> pain, infertility or ectopic pregnancy
Uterine tubes= vital for fertility! So we look at tubal patency when investigating infertility
What are the 2 methods we use to look at tube patency?
Lap and dye: use uterine catheter to inject blue due into the uterus, whilst seeing the fimbral end w a laparoscope. Dye will pass from uterus–> tubes–> fimbral end if patent.
Although invasive, we can sort any issues whilst in there instead of scheduling a separate surgery later on
Hysteron-salpingo contrast sonography (HyCoSy): injecting radio-opaque dye into uterus and up into the tubes via transvaginal catheter. Look at patency w US
Describe the cervix
how many mm thick, what cells is it lined with + function, what is ectocervix covered with
Muscular structure which can expand (fits baby head!)
Endocervical mucosa = ~3mm thick
Lined w 1 layer of columnar mucous cells, which have numerous tubular mucous glands.
These glands empty viscous alkaline mucus into cervix lumen as an infection and sperm barrier. (ovulation changes cervical mucus, allowing sperm)
Ectocervix is covered w non-keratinised, stratified squamous epithelium, similar to vagina - This is bc columnar cells of endocervix don’t like vagina’s acidic environment
What happens to the cervix during follicular phase vs luteal phase?
Use this concept to explain how contraceptives work
Estrogen in the follicular phase causes change in cervix vascularity + subsequent oedema.
Mid-cycle estrogen levels change mucous to get less viscous; mucus glycoproteins form aligned microscopic channels, which sperm swim up!
Pg in the luteal phase reduces mucus secretion
Here glycoproteins in the mucus form a viscous mesh that acts as a barrier to sperm
pg-based oral contraceptive does this too
The vagina is a ~10cm thick-walled tube.
Describe the vagina in more detail
what cells line it + function, what does it contain, 3 features which prevent infection susceptibility
- Lined by specialised squamous epithelial cells that can withstand acidity
- Warm damp environment containing glycoprotein
These conditions increase infection susceptibility, which is prevented by:
- Layers of epithelial cells shedding constantly & ‘flowing’ downwards w secretions.
- Secretions are generally acidic providing anti-microbial protection
