Regulation of Reproduction

Question 1

Why are the testes outside the body?

Answer 1

Maintain optimal temperature for sperm production

Question 2

Where is sperm produced/stored and mature?

Answer 2

• produced in the seminiferous tubules of testes
• mature and stored in the epididymis
• delivered to the urethra via the vas deferens

Question 3

What is semen and what does it consist of?

Answer 3

• consists of sperm (5%) in a fluid that nourishes them and facilitates fertilisation
• contains mucus and fibrinogen
• contains a clotting enzyme - acts on fibrinogen from seminal vesicle to convert semen into a coagulum (gelatinous mass)

Question 4

Where is semen produced?

Answer 4

• components of seminal fluid produced in seminal vesicles, prostate gland and bulbourethral glands
• all components of semen join the urethra and ejaculated through the penis by muscle contractions

Question 5

Why is semen alkaline?

Answer 5

to neutralise the acid environment of the vagina and facilitate fertilisation

Question 6

Describe the different structures the sperm has to pass to reach the oocyte

Answer 6

• seminiferous tubule
• epididymus
• vas deferens
• ampulla and ejaculatory duct
• urethra
• vagina
• uterus
• oviduct

Question 7

What hormones are involved in the regulation of reproduction and where are they secreted?

Answer 7

• hypothalamus secretes GnrH which signals the pituitary gland to release LH and FSH
• anterior pituitary releases tropic hormones which control the activities of other endocrine glands
- LH: luteinizing hormone
- FSH: follicle stimulating hormone

Question 8

Describe the series of steps in the regulation of reproduction in a man

Answer 8

> hypothalamus secretes GnRH
pituitary gland - secretes LH and FSH
LH > leydig cells
• stimulates the production of testosterone which affects reproductive tract and organs

FSH > sertoli cells > induces spermatogenesis, and releases inhibin (inhibits FSH release)

Question 9

In a male what hormone affects the leydig cells?

Answer 9

Leutinizing Hormone (LH)

Question 10

In a male what hormone affects the sertoli cells?

Answer 10

Follicle Stimulating Hormone (FSH)

Question 11

What are the 2 main cells in the testes involved in the regulation of hormones?

Answer 11

• Sertoli cells

* Leydig cells

Question 12

What is the function of the leydig cells?

Answer 12

• produces testosterone
• testosterone affects the reproductive tract and other organs
• testosterone also affects the sertoli cells

Question 13

What is the function of the Sertoli cells?

Answer 13

• induces spermatogenesis

* release the hormone inhibin - which signals the anterior pituitary and inhibits the release of FSH production

Question 14

How is a high level of testosterone regulated?

Answer 14

• Negative feedback
• high level of testosterone
> hypothalamus signalled to inhibit GnRH production
OR > anterior pituitary signalled to inhibit LH production

Question 15

Why do the testosterone levels increase at puberty? what is the effect of this?

Answer 15

• sensitivity of the hypothalamus to the negative feedback by the testosterone declines
• circulating Testosterone increase
• therefore, there is an increase in GnRH and hence an more LH and FSH

Question 16

Describe the steps involved in the hormonal control of reproduction in the female?

Answer 16

• hypothalamus releases GnRH
• anterior pituitary releases LH and FSH
• signals ovary to release eostrogen and progesterone
• uterus is signalled to grow and vascularise the endometrium

Question 17

What type of feedback occurs in the hormonal control of reproduction in a female?

Answer 17

• positive feedback occurs during days 12 to 14 -

* negative feedback occurs throughout most of the cycle

Question 18

What happens on days 12-14 in the woman’s reproductive cycle?

Answer 18

• estrogen stimulates The release of LH and FSH

* during the rest of the cycle, estrogen inhibits release of LH and FSH

Question 19

What is the corpus luteum?

Answer 19

• After the oocyte is released, the surge in LH causes the mature follicle to develop into a corpus luteum
• A hormone secreting structure that develops in an ovary after an ovum has been discharged
• degenerates after a few days unless pregnancy has begun

Question 20

Summarise the events in the ovarian cycle

Answer 20

1. oocyte maturation
2. developing follicle
3. ovulation - surge of hormone LH triggers the release of egg fro ovary
4. corpus luteum
5. degenerates if pregnancy does not occur
6. developing oocyte forms

Question 21

What structure is affected in a vasectomy?

Answer 21

The vas deferens is cut off and tied so that sperm can no longer enter the semen

Question 22

What are the steps involved in IVF?

Answer 22

1. follicles are stimulated using gonadotropins
2. mature eggs are removed from ovary
3. eggs are fertilised with sperm
4. fertilised embryos are grown in the laboratory and subsequently replaced into the uterus

Question 23

At what stage of meiosis is the mammalian oocyte ovulated?

Answer 23

In metaphase of the second meiotic division (metaphase II)

Question 24

What are the different types of contraceptives available?

Answer 24

1. Non-technological methods
   • rhythm - avoiding intercourse between days 10-20 in ovarian cycle
2. Barrier methods
   • condom
   • cervical cups - blocks cervix so sperm cannot enter
3. Hormone base contraceptives
   • oral hormones -
   “the pill”

Question 25

How do oral hormones work in preventing pregnancies?

Answer 25

Mimic pregnancy so that the ovarian cycle and ovulation are suspended
- this is by the synthetic oestrogen and progesterone in the pill

Question 26

How common is infertility?

Answer 26

1 in 6 couples require medical intervention to conceive

Question 27

What is the function of the corpus luteum?

Answer 27

Essential for establishing and maintaining pregnancy

• releases progesterone which is a steroid hormone responsible for the growth and development of the endometrium