W4 - Uterus, Uterine tubes and cervix Flashcards
What are changes in the uterus and cervix?
Maternal steroids increase size
of new-born uterus.
Grows with height during
infancy.
Myometrium dependent on
estradiol.
Corpus of uterus undergoes
greater increase in size than
cervix.
What is the myometrium?
Outer muscular myometrium grows gradually
throughout childhood.
Increases rapidly in size and configuration during
puberty.
Changes in size through the cycle. Capable of vast expansion during pregnancy.
Inner layer circular fibres.
Middle layer figure of 8 or spiral fibres.
Outer layer longitudinal fibres.
What is the endometrium?
Very thin in childhood. Begins to thicken at puberty.
Dependent on steroids and responds cyclically to
hormone changes.
Estrogen principally causes growth in proliferative
phase. Can be seen and measured on an ultrasound scan. Good ‘bioassay’ of estradiol level…7-16mm.
Changes in glandular and epithelial cells through the cycle. Progesterone causes mainly differentiation in secretory phase.
At menstruation most of the endometrium is lost.
After menstruation - stromal matrix with small
columnar cells with glandular extensions 2-3mm thick glands are simple and straight.
Nearly all of it is replaced every month.
What is the endometrial proliferative phase?
Proliferative phase (follicular phase of ovary) following menses. Stimulated by estrogen from the
growing follicle.
Stromal cell division, ciliated surface. Glands expand and become tortuous, increased vascularity, neoangiogenesis maximal cell division by days 12-14.
When endometrium >4mm induction of progesterone receptors and small muscular contractions of the myometrium.
Stage 1 -> ovulation -> stage 2
1) Previous corpus lutetium has died and formed a corpus albicans, progesterone levels dropped, lost endometrium at menstruation, taken breaks off pituitary and hypothalamus - recruit more follicles with the rise in FSH, the follicles start to make estrogens, ends up selecting a dominant follicle (oestrogen levels keep rising causing proliferation of the endometrium). This is also called the follicular phase if we are looking at the follicles. The continuous development of the dominant follicle is producing oestrogen - leading to the rise in oestrogen.
The oestrogen feed backs negatively and reduces FSH, which is involved in the selection of the dominant follicle.
What is the endometrial secretory phase?
Secretory phase (luteal phase of ovary) 2-3 days after ovulation, the gradual rise in progesterone causes a reduction in cell division.
Glands increase in tortuosity and distend…secretion of glycoproteins and lipids commences.
Oedema, increased vascular permeability arterioles contract and grow tightly wound.
Myometrial cells enlarge and movement is suppressedblood supply increases.
At the end of the follicular phase, the oestrogen levels were very high. When this is very high for a long time, the feedback on the pituitary becomes reversed and becomes positive - releases LH. This LH spikes causes ovulation resumption and completion of Meiosis I and initiation of meiosis II. The corpus luteum now starts to produce progesterone. The second half of the cycle is called secretory phase.
What is the regression of the corpus luteum?
Corpus luteum stimulated by LH from pituitary during luteal phase.
In the absence of this, falling levels of steroid from the CL results in menstruation.
Corpus luteum produces a lot of progesterone and this gets fed back to the pituitary and hypothalamus and reduces the amount of LH. The corpus luteum has LH receptors and needs LH to stay alive. The production of progesterone is great for the endometrium, but it’s reducing it’s own life by doing it. It then undergoes apoptosis and becomes a corpus albicans. When this happens, the progesterone drops very suddenly, this causes the loss of endometrium.
In a pregnancy, we do not want to lose the endometrium, so the fertilised oocyte becomes a blastocyst and produces human chorionic gonadotrophin (hCG) which acts like LH ie on LH receptor, and ‘rescues’ the corpus luteum.
The progesterone created by the embryo continues to feedback to the hypothalamus so there is no FSH or LH being produced. There is a maintenance of the endometrium so the embryo can implant.
hCG maintains balance until the placenta forms and takes over that role.
What is menstruation?
If we are not pregnant, the corpus luteum dies - lowers progesterone causing Prostaglandin release causes constriction of spiral arterioles.
The cells in the endometrium undergoes Hypoxia that causes necrosis.
Vessels then dilate and bleeding ensues.
Proteolytic enzymes released from the dying tissue, which helps to get rid of the rest of the tissue.
Outer layer of endometrium shed, 50% lost in 24hrs, up to 80ml is considered normal. Bleeding normally lasts 4+ days.
Basal layer remains and is then covered by extension of glandular epithelium.
Estrogen from follicle in next follicular phase starts cycle off again.
What is the uterine tube?
The uterine tube is primarily subdivided into 3 sections: Intramural, Isthmus, Ampullary.
The ampullary is widest part where the egg and sperm fertilise. The embryo will then spend 5-6 days moving along the tube into the uterus and around the 11th day will implant onto the endometrium.
Mucosa:
1) Secretory - secretes all kinds of growth factors, nutrients and signalling molecules required for early embryonic development.
2)Columnar ciliated epithelial - wafts embryo down the tube while it’s there.
3) Non-ciliated Peg - not sure what they are, could be incomplete form of other cells.
Muscularis:
Inner circular & outer, longitudinal layers, Blood vessels & lymphatics
Sersoa:
Outer layer
What may be changes in the cell lining the uterine tubes?
Epithelial cells express high
numbers of estrogen receptors &
undergo differentiation in response
to estradiol increase in height mid-
cycle.
Oocyte can only pass down the tube during mid-cycle. Cilia beat and secretory cells are active along with muscle layer contractions, all in response to estrogen.
After a few days of exposure to
progesterone the estrogen receptors
are supressed and estrogen effects are
overcome causing decrease in height
mid-luteal onwards.
What happens with fertilisation and early development of the embryo?
Egg remains in the tube for
approximately 5 days.
Fertilisation occurs in ampulla.
Damage to lining of the tube by
infection, endometriosis, surgery or
adhesions may cause blockage or
damage to ciliated epithelia, resulting
in…
pain
infertility
ectopic pregnancy
How do you test tubal patency?
Laparoscopy and dye:
The woman is lying on her back. There is a uterine cannula going in through the vagina, through the cervix and we inject a blue dye into the uterus. It fills up the uterus and passes down the uterine tubes and it should emerge at the fibril end of the tube if the tube is patent. The way we see it is with a laparoscope. We put it through the abdomen into the peritoneal cavity, inflate it with air to open it so we can see. We will then have forceps on the laparoscopes and a light source so we can see.
Hystero Salpingo-contrast Sonography (HyCoSy):
Less invasive. We have a catheter/ cannula type thing going in through the cervix, we fill the uterus with an ultrasound opaque dye. We can monitor it with the ultrasound and see the passage of the dye.
While HyCoSy is preferable, if there is suspicion of there being lots of endometriosis, adhesion, or we want to take a look at the pelvis, the laparoscope gives us the visual inspection of the pelvis. They may also be allergic to the ultrasound opaque dye.
What is the cervix?
Muscular structure capable of great
expansion.
The endocervical mucosa is about 3mm thick, lined with a single layer of columnar mucous cells, containing numerous tubular mucous glands which empty viscous alkaline mucus (protective barrier to infection and it can either block/allow the passage of sperm) into the lumen.
Protective barrier to infection…However, it has to allow passage of motile sperm.
The ectocervix is covered with nonkeratinized stratified squamous epithelium, resembling the squamous epithelium lining the vagina.
The sperm can get lost going round and round in the grooves of the endocervical canal. This allows a slow release of sperm. It increases the chances of fertilisation by delaying the proportion of sperm and releasing them slowly to widen the window where the sperm can meet the egg. This means if the egg hasn’t ovulated yet, it means it can get delayed enough so it can be fertilised.
What is the follicular phase of the cervix?
Estrogen in the follicular phase causes…Change in vascularity of cervix and oedema.
Mid-cycle estrogen levels cause change in mucous to become less viscous.
Change in mucous composition.
Mucus contains glycoproteins glycoproteins which become aligned and form microscopic channels.
Sperm swim up the channels!
What is the luteal phase in the cervix?
Progesterone in luteal phase causes…
Reduced secretion and viscous
mucous (reduced water content).
Glycoproteins now form mesh like
structure: acts as barrier to sperm
and microogranisms.
One mechanism of action of oral
contraceptives.
Progesterone creates sticky mucus that makes it hard for the sperm to swim through.
What is the vagina?
Thick-walled tube approx 10cm.
Lined by specialised ‘squamous epithelial’ cells.
Warm damp environment containing glycoprotein…
Susceptible to infection, which is prevented by…
Layers of epithelial cells shed constantly and ‘flow’ downwards
with the secretions.
Secretions are from cervix and transudation from vaginal
epithelium.
Secretions change with cycle and are generally acidic providing anti
-microbial protection.
Bartholins glands located slightly posterior and to the left and right of
the opening of the vagina secrete mucus to lubricate the vagina and are
homologous to bulbourethral glands in males.
