Nem’s Notes…
Phase 2 Year 3
HUMAN LIFE CYCLE 6 (page 1 of 2)
The Endometrium
Uterus
The two main parts of the uterus are:
(a) Body
(b) Cervix
It is approximately 7-8 cm in length, 5-7cm wide and 2-3 cm thick.
The three layers are:
(a) Perimetrium
(b) Myometrium
(c) Endometrium
Endometrium
The endometrium is 4-5mm thick at its peak of development and varies according to
the endometrial cycle.
The three layers of the endometrium are:
(a) Compact Layer
connective tissue (nearest lumen)
(b) Spongy Layer
thick oedematous connective tissue
(c) Basal Layer
ends of uterine glands (not shed in period)
Endometrial
Cycle
Fertilization
The endometrial cycle controls menstruation and mirrors the ovarian cycle responding
to fluctuations in hormone concentration. It has a length of 28 days with day 1 being
menstrual flow.
(a) Menstrual Phase
Menstruation, flow shedding blood and endometrium
4-5 days
(b) Proliferative Phase
Growth of follicles controlled by oestrogen, 2-3 times
increase in endometrium. Increased glands and
lengthening of spiral arteries
9 days
(c) Secretory Phase
Formation of corpus luteum controlled by progesterone.
Ovulation. Increased endometrial thickening
13 days
After fertilization the zygote forms and cleaves to become the morula and blastocyst.
Implantation occurs on day 20-28 of the cycle (6th day of secretory phase). The
sycytiotrophoblast produces hCG and the corpus luteum continues secretion of
oestrogen and progesterone. The secretory phase then continues and menstruation
does not occur. The endometrium enters pregnancy phase.
If fertilization does not occur the corpus luteum degenerates and oestrogen and
progesterone levels fall. This causes an ischaemic phase of the endometrium and
menstruation occurs. Glandular secretion stops, interstitial fluid decreases and the
spiral arteries constrict. Venous stasis ensue with patchy necrosis. Blood breaks
through the endometrial surface into the uterus and vagina.
Menstrual
Flow
Menstrual flow is approximately 20-80 mls of blood over 3-5 days. The compact and
spongy layers are shed whilst the basal layer remains.
more online at http://homepage.virgin.net/nemonique.sam/noteindx.htm page 1 of 2
Nem’s Notes…
Phase 2 Year 3
HUMAN LIFE CYCLE 6 (page 2 of 2)
The Endometrium
Fertility
The embryo will not implant in the endometrium unless the conditions are favourable.
This is called the ‘window of implantation’. Implantation failure is common and is the
major reason for IVF fertility treartment.
Contraceptive techniques can interfere with endometrial receptivity to the embryo.
These include:
(a) Intrauterine contraceptive device (IUD coil)
(b) Combined oral contraceptive (and progestogen-only)
(c) Post-coital contraception
Endometrial
Cancer
Normal growth of the vascular, stromal and epithelial cells is tightly controlled. Excess
growth may lead to hyperplasia and then onto endometrial cancer. It mostly occurs in
post-menopausal women (55-65 years) and are mainly adenocarcinomas which
spread locally and to the pelvic nodes. Most present with postmenopausal bleeding.
Risk factors for endometrial cancer include:
(a) Polycystic Ovaries
(b) Obesity
(c) Diabetes
(d) Nulliparity
Diagnosis is by means of hysteroscopy and biopsy, and treatment is by total
abdominal hysterectomy and bilateral salpingo-ooterectomy.
Menorrhagia
Menorrhagia is most commonly caused by fibroids and is one of the most common
causes for women to consult their GP and gynaecologist. Most have heavy regular
bleeds but some have irregular bleeding. Most have dysfunctional uterine bleeding not
associated with any pathology.
Menorrhagia appears linked to endometrial changes including:
(a) Increased vasodilatation (prostaglandins)
(b) Decreased vasoconstriction (endothelins)
But it is still poorly understood.
Endometriosis
Deposits of endometrium outside the uterine lining are called endometriosis and are
most commonly found in the pelvis. They are thought to migrate down the fallopian
tubes and implant. It is associated with the following:
(a) Pain
(b) Infertility
(c) Menstrual irregularity
(d) Menorrhagia
(e) Adenomyosis
Amenorrhoea
Secondary amenorrhoea may result if the basal layer is destroyed. This may be
accidental or deliberate. Hormonal levels will be normal and ovulation will still occur.
Imaging &
Sampling
Different imaging and sampling techniques are available:
(a) Ultrasound (assess thickness and structures)
(b) Hysteroscopy (direct imaging + biopsy or operative)
(c) Biopsy (investigate bleeding/thickening/hyperplasia)
more online at http://homepage.virgin.net/nemonique.sam/noteindx.htm page 2 of 2