Size and shape of the non and pregnant uterus?
About 7.5cm, pear-shaped and with a luminal volume of 10ml
The uterus is anteverted but is retroverted in 20-25% with no impact on fertility
Single pregnancy contains about 5L with up to 20L in multiple pregnancies. Made up of the baby, amniotic fluid and placenta
Growth of the Uterus?
- Initially is at least in part under oestrogen control (and prog.) as ectopic implantation leads to some of the initial growth
- Growth is however, mostly due to stretching of existing cells rather than proliferation. (50um -- 400-600um)
Regions and layers of the uterus?
The "top" of the uterus is the fundus with the bottom being continuous with the cervix
The three layers are:
- The serosa (perimetrium) - non-pregnant uterus
- The muscular myometrium - non-pregnant uterus
- The inner endometrium - functional (shed) and basal layers
Myometrium structure, function?
- Makes up 90% of uterine tissue
- Functions to produce forceful contractions of the foetus at parturition
- Approx 10mm thick and does not change significantly due to hormones in the menstrual cycle
Is the tissue that dissociates from the uterus when the placenta is delivered, it is the area into which the human embryo implants
Endometrium becomes decidualised during each menstrual cycle
What are the two cycles and what hormones link them?
- The uterine/menstrual cycle should align with e ovarian hormone cycle
- Lasts 5-6 days where the functional epithelium is lost along with 30ml of blood (VARIABLE)
2. Proliferative phase (until D14 - ovulation)
- Caused by the increasing oestrogen levels, a mitogen released from the granulosa cells
3. Secretory phase
- From progesterone released by the leutinised cells of the corpus luteum, causing glandular cells to release their secretions
- In preparation for implantation the endometrium undergoes changes called the decidual reaction
- The stroma of the endometrium becomes oedematous, stromal fibroblasts expand and fill with glycogen - an energy source for the embryo.
Uterine blood supply?
Uterine arteries feed into large branches known as radial arteries. Off these come the arcuate arteries which run around the uterus and feed into the inner branches of the radial arteries. The radial then feed down into the endometrium.
Within the endometrium they are called the spiral arteries.
Significance of the sprial arteries?
- The Spiral arteries supply the placenta during pregnancy
- They are tonically active like other arteries
- During menses the spiral artery terminal segments are lost
- To prevent exsanguination they undergo spasm
- grow faster than the surrounding tissue so have to spiral
Purpose of finding out where a lady is in her uterine cycle?
Often hormone treatments cause asynchrony between the ovarian and uterine cycles. This would lead to infertility/fertility issues.
Role of Estrogen in the Uterus?
Estrogen: mitogen + vascular permeabilising agent
- Epithelial and stromal proliferation
- stromal oedema
- glandular secretion (serous)
- synthesis of intracellular progesterone receptors (estrogen priming)
- myometrial activity
Role of Progesterone in the uterus?
- Glandular secretions (thick) in luteal phase
- Stromal cell differentiation
- inhibits myometrial activity
- Ectopic endometrium in 6-10% of women
- Causes chronic pelvic pain and is associated with infertility
- Somewhat unknown cause
- Retrograde menstruation, transport in blood or lymph, from stem cells
Regions of the cervix? HPV infections?
Endocervix: columnar epi. glands, crypts, fibrous stroma, few SMC
Transition zone: mixture, site of HPV infection
Ectocervix: stratified squamous epi.
Cervical mucous changes?
E2 increases volume, and stimulates clear watery mucous with high thredability that is receptive to sperm. Mucous contains channels for sperm access.
P4 stimulates a highly viscous and cross-linked mucus that is a barrier to sperm penetration