REPRO: Uterus, Uterine Tubes and Cervix Flashcards
How does the uterus and cervix size change as we grow?
Maternal steroids (oestrogen) increase the size of a newborn baby’s uterus. It grows with height during infancy.
The myometrium is dependant on oestradiol. The corpus of the uterus undergoes a greater increase in size than the cervix.
Uterine layers
Endometrium: inner lining
Myometrium: middle muscular layer
Perimetrium: the outer layer
Describe the structure of the myometrium.
The muscular myometrium grows gradually throughout childhood. It increases rapidly in size and configuration during puberty.
There are changes in size throughout the cycle. It is also capable of vast expansion during pregnancy.
Inner Layer: circular fibres
Middle Layer: figure-8/spiral fibres
Outer Layer: longitudinal fibres
What is the endometrium?
The inner epithelial lining of the uterus
very thin during childhood but thickens and develops during the menstrual cycle, into which a fertilised ovum can implant, and which sheds during mensuration if a pregnancy does not occur.
Describe the endometrial proliferative/follicular phase.
Proliferation/Thickening of endometrium
- stimulated by oestradiol from the dominant follicle in the follicular phase
- stromal cell division, ciliated surface
- glands expand and become tortuous, increased vascularity, neoangiogenesis
- maximal cell division by days 12-14
What maintains the thickness of the endometrium?
progesterone produced by the corpus luteum after ovulation
How does the thickening of the endometrium affect the myometrium?
when endometrium is >4mm there is induction of progesterone receptors and small muscular contractions of the myometrium
Describe the endometrial secretory phase.
Differentiation of Endometrium:
The secretory phase (luteal phase of the ovary) occurs 2-3 days after ovulation. The gradual rise in progesterone causes a reduction in cell division.
The glands increase in tortuosity and distend; the secretion of glycoproteins and lipids commences.
Oedema (increased vascular permeability) causes the arterioles to contract and grow tightly wound.
The myometrial cells enlarge and movement is suppressed as the blood supply increases.
Why does the endometrium shed?
when there is no fertilisation, the corpus luteum dies and progesterone falls, so the endometrium sheds, resulting in the stromal matrix with small columnar cells and glandular extensions
The lifespan of corpus luteum
14 days
Describe the regression of the corpus luteum.
The corpus luteum is stimulated by progesterone from the pituitary during the luteal phase.
The fertilised oocyte becomes a blastocyst and produces human chorionic gonadotrophin (hCG), which acts on the LH receptor, and ‘rescues’ the CL.
If no fertilisation
- no hCG to bind LH receptors and stimulate corpus luteum survival
- corpus luteum dies, no more progesterone, the endometrium is shed, causing menstruation
Why is hCG needed to rescue the corpus luteum?
hCG binds LH receptors to stimulate progesterone production needed for the maintenance of the endometrium
Endogenous LH can’t rescue corpus luteum due to the high progesterone levels exerting negative feedback, decreasing LH levels
How does menstruation actually occur?
- prostaglandin release causes the constriction of spiral arterioles, the ensuing hypoxia causes necrosis
- the vessels then dilate and bleeding ensues
- proteolytic enzymes are released from the dying tissue
- the outer layer of the endometrium is shed, 50% is lost in 24 hours, up to 80ml is considered normal; the bleeding normally lasts 4+ days
- the basal layer remains and is then covered by an extension of the glandular epithelium
- oestrogen from the follicle in the next follicular phase starts the cycle off again
What are the three parts of the uterine tube?
- the intramural portion
- the isthmus
- the ampulla
What are the three kinds of mucosal cells (outer surface) in the uterine tube?
1) secretory cells
2) columnar ciliated epithelial cells
3) non-ciliated peg cells
What is endometriosis?
Growth of endometrial tissue outside of the uterus
-could block the uterine tube
Laparoscopy and Dye
- cannula placed through cervix, into uterus and blue dye injected
- blue dye fills tubes and appears on fimbrae
- laporoscope inserted through the abdomen to look for blue dye
- if no blue dye is present, the tube is blocked
Hystero Salpingo-Contrast Sonography (HyCoSy)
- cannula placed through cervix, into uterus and ultrasound contrast dye injected
- ultrasound probe used to track the progress of the dye down the tube
Ectocervix
part of the cervix lined with non-keratinized stratified squamous epithelium
Endocervix
the 3mm thick mucous membrane lining the cervical canal
-it is lined with a single layer of columnar mucous cells, containing tubular glands which empty viscous alkaline mucus into lumen to stop bacteria and infection from getting into the uterus, but still allowing passage of sperm
Why is the vagina damp?
Bartholins glands located slightly posterior and to the left&right of the vagina opening secrete mucus to lubricate the vagina and are homologous to the bulbourethral glands in males.
