Session 2 - Control of Reproductive Processes

Question 1

What type of tissue is the anterior and the posterior pituitary?

Answer 1

Anterior - Endocrine gland Posterior - Nervous tissue

Question 2

What is secreted by the anterior pituitary?

Answer 2

Glycoproteins hormones - FSH, LH, TSH Polypeptide hormones - GH, ACTH, Prolactin

Question 3

What is secreted by the posterior pituitary?

Answer 3

ADH Oxytocin (although produced in the hypothalamus)

Question 4

Describe in general how FSH and LH are released?

Answer 4

Gonadotrophin Releasing Hormone is released by the hypothalamus which travels by the hypophyseal portal circulation to the anterior pituitary. The amount of FSH and LH released is directly correlated to the amount of GnRH released.

Question 5

What is the general action of LH and FSH?

Answer 5

Act on the gonads and control gamete production and stimulate secretion of the gonadal steroid. E.g. testosterone, oestrogen, progesterone.

Question 6

In the male how are FSH and LH levels altered?

Answer 6

Testosterone acts as a negative feedback mechanism by reduces the amount of GnRH that is secreted.

Question 7

In the female how are FSH and LH levels altered?

Answer 7

Moderate levels of oestrogen reduce GnRH secretion via negative feedback mechanisms. High levels of oestrogen increase the amount of LH and FSH secretion. High levels of oestrogen and progesterone prevent the high levels of LH and FSH. (however as inhibin is present only LH rises)

Question 8

Describe the HPA in the male:

Answer 8

Testosterone levels must be kept constant in the male as spermatogenesis is constant. LH and FSH are released by the anterior pituitary in response to GnRH. FSH binds to Sertoli LH binds to Leydig Testosterone is produce by Leydig cells in response to LG but can only pass into seminiferous if FSH has been primes by FSH. Inhibin is released by Sertoli cells in response to the amount of spermatogenesis that occurs. Inhabit acts on the pituitary gland to prevent FSH production. Testosterone is produced in Leydig cells but inhibits GnRH release, this keeps testosterone at constant levels.

Question 9

How do testosterone levels fluctuate?

Answer 9

Testosterone levels are highest in the morning. Testosterone levels are also affected by environmental stimuli.

Question 10

Describe what occurs during the follicular phase:

Answer 10

Follicles are only partially developed therefore little oestrogen or inhibin is produced. Progesterone levels are also low. There is little inhibition at the pituitary so FSH and LH rises. FSH binds to granulosa cells and stimulate follicle development. They also stimulate inhibin release. LH stimulates the theca interna and this causes the secretion of oestrogen. As the follicle grows there is an increase in oestrogen and inhibin secretion. This results in increased LH levels (but not FSH as inhibin is preventing its release - need low FSH levels so another follicle is not stimulated to develop) the LH surge triggers ovulation.

Question 11

Describe what occurs during the Luteal Phase:

Answer 11

After ovulation a corpus luteum forms spontaneously. The corpus luteum secretes oestrogen and progesterone. Progesterone prevents the positive feedback loop of oestrogen on the gonadotropin so FSH and LH levels are low. Also inhibin levels are still high so FSH levels are low (again you don’t want another follicle developing) after 14 days precisely the corpus luteum dies. There is a drop in oestrogen and progesterone stimulating the menses. This drop in hormones then causes FSH and LH levels to rise again and follicular development begins again.

Question 12

What is the interval between ovulation and do menses?

Answer 12

14 days

Question 13

List the stages of the menstrual cycle:

Answer 13

Preparation Ovulation Waiting - exactly 14 days

Question 14

Describe the following chart:

Answer 14

During the follicular phase of the ovarian cycle FSH andLH promote the developing follicle. As the follicle grows the level of oestrogen increases due to increasing granulosa and theca interna cells.

As inhibin levels rise due to stimualtion by FSH (inhibin is released by granulosa cells) they inhibit FSH release so it decreases. As oestrogen levels continue to rise due to LH release is stimulated. This results in an LH surge and ovulation occurs.

During the luteal phase the follicle under influence of high LH becomes the corpus luteum. Oestrogen and now progesterone are produced by the corpus luterum however less oestrogen than before was generated by the corpus luteum.

Progesterone and oestrogen present prevent the FSH and LH release. Progesterone stimulates the uterine lining in preparation for pregnancy. It stimulates the development of spiral arteries and stimulates secretion from glands. It also reduced contractilty of myometrium (Prevent embryo expulsion)

After 14 days the corpus luteum dies. Progesteron adn oestrogen levels drop, this stimualtes the menses. It also allows FSH and LH levels to rise again and so follicular development can start to occur and the cycle begins again.

Question 15

What maintains the corpus luteum is the egg is fertilised?

Answer 15

The blastocyst produces human chorionic gonadotrophin which is structurally similar to LH so it maintains the corpus luteum so it carries on producing hormones until the placenta develops.

The hormones are needed to maintain the endometrial lining.

Question 16

Describe the microscopic structure of the ovary:

Answer 16

Has a cortex and medulla.

Its outer surface is covered by squamous epithelium - a layer of peritoneum - or broad ligament

At one pole of the ovary is the hilum where the artery vein and nerve exit.

The cortex of the medulla contains germ cells in numerous stages of development.

Question 17

Describe a primordial follicle

Answer 17

An oocyte with a single layer of granulosa cells surrounding it.

Question 18

Describe a primary follicle:

Answer 18

An oocyte with a zona pellucida surrounding it. Then several layers of granulosa cells. Then outside the stromal cells differentiate into theca follicula.

Question 19

Describe a secondary follicle:

Answer 19

The theca folliculi differentiate into theca interna and externa. Fluid filled spaces devleop between the granulosa cells.

Question 20

Describe a tertiary follicle:

Answer 20

The fluid filled spaces move towards the periphery and an antrum develops. The oocyte is surrounded by a few layers of granulosa cells calles the coronar radiata.

Question 21

Describe a Graafian follicle:

Answer 21

The oocyte with its surrounding granulosa cells (corona radiata) is attached to the rest of the granulosa cells via the cumulus oophorus a peg of granulosa cells. This loosens prior to ovulation so that the occyte and corona radiata floats free in the antral fluid.

Question 22

What happens to granulosa and theca interna cells after ovulation?

Answer 22

Granulosa cells become granluosa lutein cells which produce progesterone.

Theca interna cells theca lutein cells which produces oestrogen.

Question 23

Describe the different parts of the fallopian tube:

Answer 23

Fimbria - catch the ovum - not attached the ovary

The infundibulum - bell shaped area that joins the fimbria to the ampulla

Ampulla - wide section where fertilsation normally occurs

Isthmus - narrowing where the ampulla connects to the uterus

Intramural - within the uterine wall

Question 24

Describe the wall of the fallopian tube:

Answer 24

Columunar epithelium with varying degrees of folding, glands, and cilia.

As you approach the uterus there are more peg cells- mucous secreting and fewer ciliated cells.

The most folded area is in the ampulla.

Lamina propria

Muscular layer - 2 layers in the ampulla and 3 in the isthmus.

Serosal covering - broad ligament

Question 25

Describe the layers of the uterus.

Answer 25

Endometrium - Lined by simple columnar epithelium and has a lamina propria. The lamina propria contains glands/connective/stromal elements.

The endometrium can be further divided into the stratum fucntionalis and stratum basalis. With the stratum functionalis being divided further into outer compact and deeper spongy layers.

Myometrium - Has 4 poorly defined muscle layers.

Question 26

Describe the blood supply to the uterus:

Answer 26

The uterus recieves blood supply from uterine arteries which form arcuate arteries in the myometrium.

The arcuate arteries then give rise to two sets of the branches:

Straight arteries which supply the stratum basalis

Coiled arteries which supply the stratum functionalis.

Question 27

Describe the changes that happen to the endometrial lining during the proliferative phase:

Answer 27

Stratum functionalis regenerates from the cells lining the glands in the stratum basalis which remains intact during menstruation. The growth of S.functionalis also leads to increasing length of the endometrial glands. Cells surrounding the glands - stromal cells also develop and proliferation to fill the spaces between the glands.

This regeneration is under the influence of oestrogen.

Question 28

Describe the changes that occur in the endometrium in the secretory phase:

Answer 28

Progesterone stimulates the endometrium to develop further. The glands devleop further and become coiled. The stroma becomes oedematus and the stromal cells develop into decidual cells. If fertilsatiion occurs decidual cells contribue to the formation of the placenta and produce prolactin.

Question 29

Describe the changes that occur to the endometrium during the menstrual phase:

Answer 29

Progsterone and oestrogen levels drop. The lack of progesterone leasd to spasm of the spiral arteries. The stratum functionalis is derived of nutrients and dies. This spasm is due to locally produced prostaglandins.

The stratum functionalis is not shed as the coiled arteries do not go into spasm.

Question 30

Describe the cervix:

Answer 30

Entrance is via the Internal Os and exit via the External Os with the cervical cavity between the two.

The cervix is lines by simple columnar epithelium which contains mucous secreting glands. However on the inner aspect of the internal Os there is an abrupt change in the epithlium to stratified squamous epithelium. This is called the squamocolumnar junction and is where the majority of neoplasms occur.

Question 31

Describes the structure of the vagina:

Answer 31

Fibromuscular tube that connects the cervix to the exterior.

Mucosa - stratified squamous non-keratinised epiethlium. No glands.

Sub mucosa

Muscular layer containg smooth and skeletal muscle.

Question 32

The vagina lacks glands so how is it lubricated?

Answer 32

By mucus produced by glands in both the cervix and the vestibule.

Question 33

What generates the acidic environment of the vagina?

Answer 33

Under the influence of oestrogen the epithelial cells accumulate glycogen which is a substrate for lactobacillus to produce lactic acid which causes a low pH.

Question 34

Describe breast tissue at puberty:

Answer 34

Under influence of increasing oestrogens the breast enlarges due to deposition of adipose and the duct system becomes much larger.

At this stage the secretory portions are poorly developed and surrounded by myoepithelial.

Question 35

What changes occur to the breasts during the menstrual cycle?

Answer 35

The mammary glands are stimulated by the oestrogen peak during each cycle which induce duct proliferation and lead to enlargements adn sometimes oedema and tenderness.

Question 36

What changes are seen to breast tissue during pregnancy?

Answer 36

Oestrogen causes proliferation of the duct system.

Progesterone influences development of secretory tissues.