Female Tract, Oogenesis and Endocrine Control 2

Question 1

How many women have 28 day menstrual cycles?

Answer 1

This number is determined on averages

Can be from 19 to 35 days!

• The cycle length decreases with age, and is more variable at beginning and end!

Question 2

Are the follicular and luteal phases the same length?

Answer 2

No!

1. Follicular/Proliferative Phase is longer and more variable
2. Luteal/secretory phase is short and constant/stable

Therefore we can work backwards only from the constant luteal phase to see the start of the cycle!

Question 3

Concept of Cycles

Answer 3

• A relatively recent phenomenon
• Early ancestors had only 30-40 cyles in a lifetime
• Puberty later and 1-2 years in cycle most anovulatory
• First pregnancy with 2-3 years of lactational amenorrhoea followed immediately by another pregnancy
• average 5 kids
• Shorter lifespan

WHereas nowafay (due to early cessation of breaast feeding and less pregnancies) = 400 cycles

Question 4

Fallopian Tubes Sections!

Answer 4

• The fimbrae swept around the surface of the overy
• Hopefully pick up oocyte with cumulus cells
• Then oocyte has to pass through tube

Tube: becomes simplier towards uterine body

• *Infundibulum**: where finger-like fimbrae are
• *Ampulla**: widening, where fertilsation often takes place. Tortuous nature of the tube so the embryo can be in close contact with tubal secretions.
• *Isthmus:**

Question 5

Structure and Spithelium of Fallopian tubes!

Answer 5

Structure

• epithelial lining:
• Muscular coat; inner circ. and outer longit.
• Serosal coat

Epithelium

• Ciliated: transport of fertilised oocyte throuhg the tube
• Secretory: helpful products for sperm, oocyte and fert. oocyte
• Responsive to steroids.

Question 6

Effect of E₂ (oestrogen) in the fallopian tubes during the follicular phase, it promotes:

Answer 6

1. Increase in Cilia
2. Increase in secretory activity: so f.tubes aren’t dry, allowing nourshment and motility of oocyte
3. Increase in muscular activity of Fallopian tubes!

The overall aim is to get the oocyte moving down the fallopian tubes to get to the uterus for implantation, takes ~5 days!

Question 7

What are the effects of P₄ (progesterone) on the fallopian tubes during the luteal phase? WHY IS THIS DONE?

Answer 7

• Decreases Cilia, but increases in the beat frequency after estrogen priming,
• Decrease in muscular activity
• Decrease in the volume of secretions

As around _day 21 implantation occur_s, you no longer need the oocyte moving!!

Question 8

Describe the Uterus

Answer 8

• 7.5cm long and pear shaped
• Very little luminal volume! Non-pregnant uterus =10ml volume
• Pregnant uterus= 5L (baby, amniotic fluid and placenta)
  
  • Therefore major changes in the physiology of the uterus are required during pregnancy

Question 9

Placement of the uterus within the pelvis

Answer 9

1. Usually anteverted (top of the uterus faces forward): fetus has to turn 90º to be born via vagina
2. Retroverted uterus occurs in 20-25% of women

Both are considered normal!

Question 10

Describe the sections and layers of the uterus.

Answer 10

Layers:

1. Serosa (perimetrium)
2. Muscular Myometrium (controls labour)
3. Inner Endometrium***(changes wiht the menstrual cycle)

Top: fundus
Middle: Body
Bottom: continuous with the Cervix

Question 11

Describe the uterus Myometrium

Answer 11

• Makes up the ‘bulk’ of uterine tissue (90%)
• For forceful expulsion of the fetus at parturition
• Approx. 10mm thick and this is relatively constant

Question 12

Describe the two layers of the Endometrium!

Answer 12

Functional Layer: what changes with menstrual cycle

Basal Layer: Relatively unaffected by menstruation

Contains secretory glands that empty contents into the uterine lumen

Question 13

What is the ‘decidua’, and what part of the endometrium does this relate to?

Answer 13

Decidua: The piece of tissue lost during menstruation, (like leaves lost on a tree)

Functional Layer: is what is lost. How this occurs:

1. Menses: tissue is breaking down, (note glands still there in basal layer**)
2. Proliferative phase: circular glands
3. Secretory Phase: Tortuous gland profile

Question 14

Briefly describe the tissue changes in menses, prolif. phase and secretory phase!

Answer 14

1. Menses (0-6days): loss of the functional layer of tissue, during the end of this tissue begins to mend.
2. Proliferative Phase: Tissue grows under the influence of increasing E₂ levels (released from follicle) and produces circular glands
3. Secretory Phase: P₄ from progesterone induces tortuous secretory glands.

Question 15

What is the ‘Decidual Reaction’?

Answer 15

Human embryos implant entirely inside the uterine wall (not the case in many other animals), so in preperation for this the functional layer of the Endometrium undergo changes called the decidual Reaction.

• Endometrial Stroma becomes odematous
• Stomal fibroblasts expand and fill with glycogen (providing an energy source for the embryo when it first implants)

This only occurs in a few species, but occurs spontaneously each menstrual cycle in women, therefore relatively uncommon (**only post implantation in many species, “pseudodecidual reaction’)

Question 16

The endo metrium is growing at an extremely rapid rate, which requires a huge amount of food + O₂.

What are the arteires which supply the Uterus?

Answer 16

Big Uterine Artery → arcuate arteries (circular & run around uterus) → Radial Arteries (project in towards endometrium) → spiral arteries (at myometrial/endometrial boundaries)

** off the raidal arteries, there are also “Basal arteries” which supply the basal layer and are unaffected by menstruation

Question 17

The key vessels that supply the endometrium + pregnancy + the placenta are ________.

Describe these vessels

Answer 17

Spiral Arteries

1. Tonically active like other vessels
2. Terminal Spiral art. segments are lost along with the rest of the Functional layer. (not 100% confirmed)
3. Spasm (to prevent exsanguination → necrosis of func. layer which is then sloughed off “menstruation”(draining of a person))
4. These grow rapidly (as well as endo. glands) in the proliferative phase of the cycle.

Question 18

How is it that spiral arteries are formed in spring-like coils?

Why is this an important physiologically adaptation

Answer 18

Since they grow way faster then the surrounding stromal tissue.

This allows for expansion of the uterine cavity during pregnancy.

In fact ALL uterine arteries have a significant degree of coiling, due to this expansion!

((The same applies for the glands!!))

Question 19

Briefly link the relationship of follicular growth to the Menstrual cycle

Answer 19

1. Post-puberty we produce large follicles which secrete a larger amount of estrogen.
2. Estrogen is a mitogen that drives cell proliferation → thickening of the endometrium following menstruation.
3. Post- ovulation we have the corpus Luteum take over as the main steroid producer, producing primarily Progesterone (with some oestrogen), which acts in the F.tubes, uterus.

Question 20

Dating of the endometrium.
Review and memorise pg 198 of the module

Answer 20

Allows us to date relatively accurately the day of the cycle the uterus is in

Question 21

What’s the role of Estrogen in the uterus

Answer 21

1. Epithelial and stromal cell proliferation
2. Stromal Oedma: vascular permeability agent
3. Glandular Secretions (serous)
4. Synthesis of intracellular progesterone receptors (‘estrogen priming’)
5. Myometrial activity

Question 22

What’s the role of Progesterone in the uterus

Answer 22

1. Promotes thick(er) glandular secretions in the luteal phase (this requires a previous estrogen stimulation)
2. Stromal Cell Proliferation
3. “Decidual Reaction”

**Inhibits Myometrial activity as oocyte should be now in the uterus and you want implantation to be able to occur

Question 23

How do we know you don’t 100% require the decidua/decidual rection for implantation?

Answer 23

Because of Ectopic Pregnancies (implantation somewhere other then the uterus, usually the fallopian tubes, which don’t have an endometrium)

Question 24

What is Endometriosis?

Answer 24

“endometrial tissue outside of the uterus”: Ectopic Endometrium

• Often in ovaries
• 6-10% in women
• Chronic pelvic pain and potentially infertility
• Aetiology still unknown, but could be from:
  
  • Retrograde menstruation; where tissue travels back up to pelvis during menstruation
  • Endometrial cells travel via blood or lymphatics
  • Stem cells that inappropriately differentiate outside of uterus

Question 25

The Cervix is divided into 2 compartments; what are the tissue types of these?

Answer 25

1. Endocervix
   
   • Columnar epithelium
   • Glands, crypts (sperm can move)
   • Fibrous stroma, few SM cels
2. Ectocervix
   
   • Stratified Squamous Epithelium

Question 26

What part of the cervix is targeted by HPV?

Answer 26

The Squamocoloumnar junction. Closer to the endocervix.

**transformation zone between ecto/endo is squamous only!

• Cervical cancer is caused by HPV here
• Regular smears required every 3 years in sexually active women, from 20-70yrs
• Smears can reduc a women risk by 90%
• Vaccine exists for sterotypes of 16 and 18, but other stereotypes also cause it!