Uterus, Uterine Tubes and Cervix Flashcards
Which layer of the uterus undergoes dramatic changes in the menstrual cycle and is replenished each month?
What is the muscle layer of the uterus?
Describe the blood supply of the whole of the uterus?
The endometrium (inner lining)
The myometrium
Very good blood supply
What happens to the endometrium during the proliferative phase?
Why is a pregnant woman’s uterus bigger?
What happens to the myometrium during pregnancy?
Why does the uterus size decrease of a post-menopausal woman?
When does the uterus grow in a lifetime?
Which part of the uterus undergoes greater increase in size, the corpus or cervix?
It proliferates due to oestrogen
The oestrogen caused it to increase in size
It is the part of the uterus that gets bigger due to oestrogen
Fall in oestrogen levels
The uterus of a new-born is big (bigger than age 4). It then grows in height during infancy and then in puberty
The corpus
Describe the fibres of the myometrium
Why can the myometrium be described as adaptive?
Which part of the myometrium grows gradually throughout childhood?
Which layer is on the outside of the myometrium?
What non-cancerous uterine growths originate from the myometrium?
3 types of fibre - longitudinal (outer), spiral (middle) and circular fibres
It changes in size and configuration e.g. from the size of a pear to watermelon in pregnancy so it can cause muscle contractions to push the baby out; changes in size through a menstrual cycle; rapid change in size and configuration in puberty too
The outer muscular myometrium grows gradually throughout childhood
The perimetrium
Uterine fibroids
Thickness of endometrium in childhood and puberty?
Which hormones does the endometrium respond to?
What is the stromal matrix?
Why does the endometrium thicken when the menstrual cycle starts again?
What causes differentiation of the endometrium after ovulation and how and why?
How can an endometrium be seen and measured?
It is very thin in childhood but thickens in puberty
Oestrogen and progesterone
The smallest the endometrium can get (after shedding in menstruation) - 2-3 mm
Oestrogen causes the endometrium to thicken. When the corpus luteum dies, progesterone falls and so a release of -ve feedback causes FSH to rise. FSH causes development of early antral follicles which produce oestrogen which affect the endometrium (thickens it from 2-3mm to 10-15mm)
Progesterone causes differentiation of the endometrium; it forms spiral arteries/ glands to appear which secrete mucus, adhesion molecules, nutrients. This also provides lots of blood supply and lots of oxygen.
This gives the perfect environment for embryo to implant.
An endometrium can be seen via ultrasound and you can measure estradiol level via a bioassay. 7-16mm.
What stimulates the endometrial proliferative phase to occur?
What happens in the proliferative phase to the endometrium?
What happens when the endometrium is greater than 4mm?
Estradiol from the dominant follicle
- Stromal cell division - max by day 12-14
- Forming of a ciliated surface
- Glands expand and become tortuous (twisting)
- Increased vascularity (angiogenesis)
Progesterone receptors get expressed, so the endometrium is ready for progesterone in the secretory phase. The myometrium also has small muscular contractions.
What causes a reduction in the endometrium’s cell division and when does this happen?
What else happens in the endometrial secretory phase?
The gradual rise in progesterone in the secretory phase causes reduction in cell division (occurs 2-3 days after ovulation)
- Glands keep increasing in tortuosity + they distend - increased secretory surface area
- Glands secrete glycoproteins and lipids
- Oedema occurs (increased vascular permeability and blood supply), arterioles contract and grow tightly wound (spiral)
- Myometrial cells enlarge
What sustains the corpus luteum in the luteal phase?
What happens when there is an absence of hCG?
Human chorionic gonadotrophin (hCG) from blastocyst acts like LH on the LH receptor to sustain the CL
No embryo? No hCG. No CL sustenance. No progesterone. No endometrium sustenance. Menstruation.
How is the endometrium lost in menstruation?
What causes the bleeding in menstruation?
What does the dying tissue release to cause further degradation?
Which layer of the endometrium sheds in menstruation?
How much of the outer layer is lost in 24 hours?
How much blood release is normal?
How long does the bleeding normally last?
Which part of the endometrium remains? What happens to it when it grows in the next cycle?
What starts the endometrial cycle again?
Prostaglandin release causes constriction of spiral arterioles, depriving the endometrium of oxygen so hypoxia and necrosis occurs
Bleeding occurs when the vessels dilate after the above
Proteolytic enzymes
The outer layer
50%
80ml
4 days
The basal layer
It gets covered by extensions of the glandular epithelium
Oestrogen from the follicles in the next follicular phase
Where does fertilisation occur in the uterine tube?
What causes the uterine tube to sustain the embryos growth in it for the first few days?
Describe the structure of a uterine tube
Ampulla
Signalling between the embryo and uterine tube. The UT released secretory molecules in response - exactly what the embryo needs
The outer layer is the serosa
Then there are smooth muscle layers - outer muscular layer is longitudinal, inner muscular layer is circular muscle
The mucosal layer has 3 types of cells
1. Secretory cell
2. Cilia that beat (columnar ciliated epithelial cells)
3. Non-ciliated peg cells
The cilia move the embryo along
What type of cells line the tube?
How is oestrogens and progesterones effect on the endometrium different to their effects in the uterine tube?
Ciliated and secretory cells in the mucosal lining
Oestrogen increases due to the dominant follicle
There are oestrogen receptors on UT epithelial cells
When oestrogen binds them, it causes differentiation of the endometrium
Cells grow taller, ciliated cells start to beat, secretory cells secrete growth factors, sugars, hormones etc., muscle of UT starts contracting to prepare environment for embryo development
Progesterone produced by the CL suppress the oestrogen receptors so the cilia beating/ secretions are lost. This happens a few days after ovulation.
This means if the egg is late it cannot continue it’s passage since the tube is shut off.
How big is an oocyte?
100 micrometers
How long does the oocyte remain in the uterine tube?
How can the uterine tube get damaged? What can this lead to?
5 days
Infection - chlamydia
Endometriosis - cells of endometrium lodge in tube
Ectopic pregnancy - fertilized egg implants in UT
Adhesions/ inflammations caused by pelvic inflammatory disease
Surgery
Can result in tube being removed
What are 2 methods of investigating a blockage in the uterine tube?
- Laparoscopy and dye
Laparoscope used to view inside abdomen. Dye injected into uterus via uterine cannula.
If dye does not appear out of tube it is blocked. - HyCoSy (less invasive method as no laparoscope)
Ultrasound probe put on abdomen and dye monitored on ultrasound
Describe the structure of the cervix
How is the cervical mucus different during a cycle?
What is the ectocervix covered with?
- Muscular structure capable of great expansion
- Has cervical crypts that sperm get into
- Has mucosal lining that is 3mm thick
Lined with single layer of columnar mucous cells, has numerous tubular mucous glands which secrete viscous alkaline mucus into the lumen
Mucus is protective barrier against infection
At the start/ end of the cycle the mucus is stiff and blocks the cervix since there is no chance of fertilization and so you must block bacteria/ sperm from passing through.
Around ovulation time (in the window of opportunity) the mucus becomes more liquid and forms channels for sperm to swim through
The ectocervix is covered with nonkeratinized stratified squamous epithelium, resembling the squamous epithelium lining the vagina.
What happens to the cervix in early/ late phase menstrual cycle?
What happens to the cervix due to oestrogen in the follicular phase and ovulation?
Mucus contains glycoproteins. They form a mesh through which sperm cannot get through.
Follicular phase - increased blood flow/ oedema in the cervix
Ovulation - mucus becomes less viscous/ more watery; glycoproteins align to form channels through which sperm can swim
