REPRO: Uterus, Uterine Tubes and Cervix Flashcards
How does the uterus and cervix size change as we grow?
The maternal steroids (oestrogen) increase the size of a new-born 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.
Describe the structure of the myometrium.
The outer, 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. It is responsive to oestrogen.
Inner Layer: circular fibres
Middle Layer: figure-8/spiral fibres
Outer Layer: longitudinal fibres
Describe the endometrium of the uterus.
It is very thin in childhood, and begins to thicken at puberty.
It is dependant on steroids; it responds cyclically to hormone changes (oestrogen). Oestogen principally causes growth in proliferative phase. Can be seen and measured on an ultrasound scan. Good ‘bioassay’ of oestradiol level… 7-16nm.
There are changes in the glandular and epithelial cells through the cycle. Progesterone causes mainly differentiation in secretory phases. At menstruation, most of the endometrium is lost.
After menstruation, there is still the stromal matrix with small columnar cells with glandular extensions that are 2-3mm thick. The glands are simple and straight.
Describe the endometrial proliferative phase.
Proliferative phase (follicular phase of ovary) following mensus. This is stimulated by oestrogen from the growing follicle.
There is stromal cell division with a ciliated surface. The glands expand and become tortuous, with an increased vascularity (neoangiogenesis) and maximal cell division by days 12-14.
When the endometrium is >4mm thick, induction of progesterone receptors occurs, leading to small muscular contractions in the myometrium.
Describe the endometrial secretory phase.
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.
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.
In the absence of this, the falling levels of steroids from the CL result in menstruation.
How does menstruation actually occur?
- CL dies (LH level cut off) + progesterone levels fall this causes the release of prostaglandin
- prostaglandin release causes the constriction of spiral arterioles, the ensuing hypoxia causes necrosis of endometrium cells.
- 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 (where egg and sperm meet)
What are the three kinds of mucosal cells in the uterine tube?
1) secretory cells
2) columnar ciliated epithelial cells
3) non-ciliated peg cells
What are the muscularis and serosa of the uterine tube?
MUSCULARIS:
- comprised of inner circular and outer longitudinal layers
- contains blood vessels and lymphatics
SEROSA:
- the outer layer
Describe the changes to the cells lining the uterine tubes (ciliated and secretory) throughout the menstrual cycle.
FOLLICULAR/PROLIFERATIVE PHASE:
Epithelial cells express high numbers of oestrogen receptors and undergo differentiation in response to an oestradiol: they increase in height mid-cycle.
OVULATION:
The oocyte can only pass during mid-cycle. The cilia beat and the secretory cells are active, along with muscle layer contractions, all in response to oestrogen.
LUTEAL/SECRETORY PHASE:
After a few days of exposure to progesterone, the oestrogen receptors are suppressed and the effects of oestrogen are overcome, causing a decrease in height mid-luteal phase onwards. Progesterone opposes differentiation in this phase.
Where does fertilisation occur?
Fertilisation occurs in the ampulla of the uterine tube.
The egg remains in the tube for approximately 5 days.
What can damage to the lining of the uterine tube lead to?
Damage to the lining of the tube by infection (e.g. Chlamydia), endometriosis (endometrium cells leave and get lodged in other places - continue to grow), surgery or adhesions may cause blockage or damage to the ciliated epithelia, resulting in:
- pain
- infertility
- ectopic pregnancy
Tubal (uterine) Patency can be used to check for these potential damages. The 2 methods of doing this is:
- Laparoscopy and dye: uterine cannula inserted through vagina and cervix, it injects a blue dye into the uterus, uterine tubes and towards the fibral end of the ovary (if the uterine tube is patent) - it can be seen via an operating laproscope through incision into the abdomen.
- Hystero Salpingo-contrast Sonography (HyCoSy): catheter injects a dye through the vagina and cervix, this can be seen on ultrasounds - no incision required.
Describe the structure of the cervix.
It is a muscular structure between the vagina and uterus, capable of great expansion.
The endocervical mucosa is about 3mm thick, lined with a single layer of columnar mucous cells. These contain numerous tubular mucous glands which empty viscous alkaline mucus into the lumen.
It’s a protective barrier to infection; however, it has to allow the passage of motile sperm.
The ectocervix is covered with nonkeratinised, stratified, squamous epithelium, resembling the squamous epithelium lining the vagina.
Describe the cervix during the follicular phase.
The oestrogen in the follicular phase causes a change in vascularity of the cervix, and oedema.
The mid-cycle oestrogen levels cause changes in mucous to make it less viscous:
- a change in mucous composition
- contains glycoproteins which become aligned and form microscopic channels, up which sperm swim!
