Uterus, Uterine tube and Cervix Flashcards
What are the different uterine layers?
Endometrium: inner lining
Myometrium: middle muscular layer
Perimetrium: outer layer
Describe the stucture of the myometrium.
3 layers of muscle fibres:
- inner layer of circular fibres
- middle layer with figure of 8 spiral fibres
- outer layer with longitudinal fibres
*allow contraction in every direction
Describe the structure of the endometrium.
The inner epithelial lining of the uterus that 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.
What maintains the thickness of endometrium?
progesterone produced by the corpus luteum after ovulation
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
Describe the endometrial Proliferative Phase.
Proliferation/Thickening of endometrium
- stimulated by oestradiol from dominant follicle in follicular phase
- stromal cell division, ciliated surface
- glands expand and become tortuous, increased vascularity, neoangiogenesis
- maximal cell division by days 12-14
What is the proliferative phase known as in the ovary?
Follicular phase
How does 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 Secretory Phase.
Differentiation of Endometrium
- 2-3 days after ovulation where the rise in progesterone from corpus luteum causes more differentiation than proliferation of endometrium
- glands increase in tortuosity & distend, secreting glycoproteins and lipids
- increased vascular permeability leading to oedema
- myometrial cells enlarge and movement is suppressed
What is the secretory phase known as in the ovary?
luteal phase
What is Lifespan of corpus luteum?
14 days
Describe the Regression of corpus luteum.
If no fertilisation
- no hCG to bind LH receptors and stimulate corpus luteum survival
- corpus luteum dies, no more progesterone, endometrium is shed, causing menstruation
Why is hCG needed to rescue corpus luteum?
hCG binds LH receptors to stimulate progesterone production needed for maintenance of endometrium
Endogenous LH can’t rescue corpus luteum due to the high progesterone levels exerting negative feedback, decreasing LH levels
How does menstruation occur?
As corpus luteum dies:
- prostaglandins are released causing constriction of spiral arterioles, starving tissue of oxygen
- vessels then dilate and necrotic tissue bleeds, releasing proteolytic enzymes
- outer endometrial layer shed
- basal endometrial layer remains and is covered by extension of glandular epithelium
Describe the Structure of Uterine Tube.
MUCOSA- outer surface
>Secretory epithelial cells
>Ciliated epithelial cells
>Non-ciliated Peg cells
MUSCULARIS- smooth muscle
>inner circular layer
>outer longitudinal layer
SEROSA-connective tissue
>outer protective layer