Lecture 2: Preparing for pregnancy

Question 1

Layers of the wall of the uterus

Answer 1

Myometrium

Endometrium

Question 2

Details of Endometrium:

Answer 2

Structure:  
Columnar surface epithelium
Uterine glands
Connective tissue stroma
Spiral arterioles

Layers:
Functional layer
Basal Layer

Question 3

Uterine Structure (Cervix)

Answer 3

Mucosal surface is characterized by numerous crypts

Epithelium produces a glycoprotein-rich cervical mucous:

Mucous composition varies throughout uterine cycle, being thinnest around the time of ovulation.

Question 4

Vagina

Answer 4

Lined with stratified, non-keratinized squamous epithelium

Epithelium secreted glycogen throughout menstrual cycle:
*Glycogen breakdown

Question 5

The menstrual cycle is controlled by

Answer 5

… alternating levels of hormones: FSH, LH, estradiol, and progesterone, that cycle over an average of a 28 day period.

Question 6

Hormones for the menstrual cycle are controlled where?

Answer 6

These hormone levels are controlled by the hypothalamus via the anterior pituitary.

Question 7

What areas of the female reproductive tract are affected by the menstrual system

Answer 7

The areas of the reproductive system affected include the ovarian follicle and the endometrium of the uterus (and also the myometrium).

Question 8

Two sub cycles of the menstrual cycles:

Answer 8

• Ovarian cycle

* Endometrial cycle

Question 9

Follicular Phase:

Answer 9

• The follicular phase of the ovarian cycle occurs during days 1- 14 of the menstrual cycle.
• During this phase there is development of the mature Graafian follicle and secondary oocyte within the ovary.

Question 10

Development of the Graafian follicle is under the influence of:

Answer 10

FSH (follicle-stimulating hormone) produced by the anterior pituitary as a result of FSH-releasing factor from the hypothalamus.
• The granulosa cells of the developing follicle secrete estradiol, which is responsible for the proliferation phase of the endometrium.

Question 11

Ovarian Cycle: Ovulation

Answer 11

• Ovulation occurs on day 14 of the cycle.
• The stimulus for ovulation is a rise in levels of FSH and a sharp rise in LH (also from the anterior pituitary).
• During ovulation, an egg is released from the Graafian follicle. • The egg is surrounded by a layer of follicle cells (the corona radiata).
• The egg is arrested in the second half of meiosis (metaphase II).
• The egg will not complete meiosis unless fertilized.
• The egg is accompanied by a very small, nucleated sister cell (product of the first meiotic division) called a polar body.
• The outer part of the Graafian follicle remains behind and is made up of thecal cells, which secrete progesterone.O

Question 12

Ovarian Cycle: Luteal Phase:

Answer 12

• During this phase the residual thecal and granulosa cells of the follicle, left over after ovulation, secrete estrogen and progesterone.
• The residual theca and granulosa cells proliferate and form a large glandular structure called the corpus luteum.
• The progesterone and estradiol are necessary to maintain the implantation of the fertilized oocyte.

Question 13

If fertilization does not occur:

Answer 13

• The corpus luteum regresses and levels of progesterone and estradiol
decrease, resulting in the beginning of the next menstrual phase.
• Inhibin, released by the granulosa cells, inhibits secretion of gonadotropins, especially FSH, resulting in regression of the corpus luteum.

Question 14

Endometrial cycle:

Answer 14

• The endometrial cycle refers to the cyclic changes in the endometrium and lasts, on average, 28 days.
• The cycle begins with the first day of menstruation and ends 28 days later.

Question 15

The endometrial cycle can be divided into three phases:

Answer 15

• Menstrual phase (Days 1-4 or 5)
• Proliferation phase (Days 4-14)
• Secretory phase (Days 15-28)

Question 16

Menstrual Phase:

Answer 16

• During this phase the endometrial build-up from the previous cycle sloughs off, resulting in the menstrual flow.
• Menstruation begins with vasoconstriction of the spiral arteries that have been supplying the endometrium, followed by local ischemia.

Question 17

Menstrual Phase, local ischemia:

Answer 17

• This vasoconstriction is mediated by prostaglandins.
• Inflammatory cells invade the area and continue the process of
endometrial breakdown.
• Factors that inactivate the clotting process maintain bleeding until the lining is sloughed off.

Question 18

Endometrial phase: Proliferation phase:

Answer 18

• Endometrial growth increases the endometrial thickness from 1-2 mm to 8-10 mm by day 14.
• Blood vessels and glands grow with the expanding endometrium.
• Cells that initiate the growth come from the bases of the glands that formed in the previous endometrium that were deep enough to survive the loss of the previous endometrium.
• The proliferation phase is due to an increase in levels of estradiol secreted by the granulosa cells of the developing ovarian follicle.
• Near the end of this phase there is a sharp rise in estradiol levels.

Question 19

Endometrial phase: Secretory phase

Answer 19

• During this phase levels of estrogen decrease and the endometrial growth stops.
• Mucous glands develop more fully and begin secretion.
• The spiral arterioles in this area expand and heavily
vascularize the area.
• The secretory phase is controlled by rising levels of progesterone, secreted by both the granulosa and thecal cells of the ovarian follicle.

Question 20

Endometrial CYCLE:

Answer 20

• The endometrial cycle essentially prepares the lining of the uterus to receive the fertilized egg.
• Implantation of the fertilized egg occurs about seven days after ovulation.
• Ovulation occurs on day 14 of the menstrual cycle.
• If fertilization does not occur, then decreasing levels of estradiol and progesterone result in the vasoconstriction of the spiral arterioles supplying the endometrium followed by the sloughing off of the endometrium at the beginning of the next cycle.

Question 21

In Females:

Answer 21

• All of the stem cells (oogonia) are committed to the first half of meiosis prior to birth.
• In the early female embryo, there are about 7 million of these oogonia cells.
• Shortly after birth, only about 500,000 remain, and these continue to decrease over time.
• Almost all of these eggs and the surrounding support cells (follicle cells) will degenerate (become atretic) before menopause.
• Only about 400-450 eggs will actually be ovulated during a women’s reproductive years.
• By menopause, all of the follicles have either degenerated or have undergone ovulation.
• Therefore, at menopause, there are no follicles left to produce estradiol and progesterone.
• This leads to the characteristics that are associated with menopause.