The Male Reproductive System

Question 1

What is role does the testis have in the male reproductive system ?

Answer 1

Testis: An organ which produces spermatozoa (male reproductive cells)

Question 2

What is the epididymis and what is its function ?

Answer 2

The epididymis is a coiled tube behind the testis that connects the testicles to the vas deferens, which transport sperm to the urethra.

Function: Collects and stores sperm, and helps sperm mature before ejaculation

Question 3

What affect does overheating have on the testes?

Answer 3

Overheating of testes reduced sperm count

Question 4

Meiosis in males: what happens during the interphase ( S-phase) in meiosis?

Answer 4

Each chromosome is duplicated

Question 5

What are tetrads?

Answer 5

Tetrads (group or set of 4) are two pairs of sister chromatids (sister chromatids)

Question 6

Meiosis in males: what happens in prophase? (2)

Answer 6

the chromosomes condense (they become shorter and fatter) and the nuclear envelope disintegrates.

The centrioles move to opposite poles of the cell and form spindle fibres.

Question 7

Meiosis in males: what happens in metaphase I? (3)

Answer 7

Tetrads align at the metaphase plate (equator), each connected to the spindle fibre via their centromeres.

Crossing over occurs leading to different combinations of genes

Centrioles contract-> sister chromatids move to opposite poles of the cell

Question 8

Meiosis in males: what is the result of meiosis I ?

Answer 8

After meiosis I, each cell has one pair of sister chromatids that are no longer identical due to crossing over.

Question 9

Meiosis in males: what is the result of meiosis II?

Answer 9

MII is another cycle of cell division in which the sister chromatids separate to give a single unique chromosome in each daughter cell.

4 genetically different daughter cells each contains one chromosome ( haploid)

Question 10

What is spermatogenesis?

Answer 10

Spermatogenesis: the process by which spermatogonia (germ/stem cells) undergo meiosis to produces primary spermatocytes which further differentiate into mature haploid spermatozoa

Question 11

Where is spermatogonia found ?

Answer 11

spermatogina (germ cells/stem cells) are found on the basement membrane of the seminiferous tubules

Question 12

1. What does mitosis of spermatogonia produce?
2. What does meiosis of spermatogonia produce ?

Answer 12

1. More spermatogonia
2. Primary spermatocytes

Question 13

What happens to primary spermatocytes ?

Answer 13

Primary spermatocytes move into the adluminal compartment between adjacent Sertoli cells and undergo meiosis I.
Meiosis II occurs to give 4 haploid spermatids (23 single chromosomes).

Round spermatids then differentiate into elongated spermatids. Mature spermatozoa are extruded into the lumen

Question 14

What hormone does the hypothalamus release that plays an important role in the male reproductive system?

Answer 14

The Hypothalamus produces Gonadotrophin Releasing Hormone (GnRH) which is a 10 amino acid long dipeptide. It is released in pulses from the hypothalamus and travels to the pituitary gland where it is secreted to stimulate the release of LH and FSH from the pituitary gland.

Question 15

What effect does pulsating vs continuous release of GnRH have on LH and FSH ?

Answer 15

Pulsatile GnRH secretion : stimulates LH and FSH secretion

Continuous GnRH secretion: decreases LH and FSH secretion

Question 16

What are group of hormones do FSH and LH belong to ?

Answer 16

FSH and LH are glycoprotein hormones collectively known as Gonadotrophins

Question 17

What is the difference between Gonadotrophin hormones FSH and LH

Answer 17

Gonadotrophin hormones are heterodimeric peptides which a common alpha-subunit and hormone specific beta-subunit
( beta strands are different lengths )

Question 18

What is the role of FSH in the males?

Answer 18

.FSH stimulates the gonads (testes) - for growth and sperm production

.FSH maintains healthy testicular cells and regulates spermatogenesis

Question 19

What is the role of LH in males?

Answer 19

. LH causes the testes to produce testosterone and other androgens

Question 20

What are Gonadotrophins used for in pharmacology?

Answer 20

. stimulate the gonads, primarily in cases of infertility or subfertility. They are commonly used in females especially for ovulation induction or in IVF cycles.

Question 21

What is the main sex steroid in men

Answer 21

Testosterone

Question 22

How many carbons are in progestogens (female) vs androgens (male)?

Answer 22

Progestogens- 21 carbons

Androgens- 19 carbons

Question 23

What nervous system pathway is responsible for erections ?

Answer 23

Parasympathetic nervous system

Question 24

What causes an erection ? (2)

Answer 24

Parasympathetic derived acetylcholine binds to muscarinic receptors on endothelium causing release of nitric oxide which diffuses to arterial smooth muscle causing relaxation and vasodilation. = swelling
Greater blood flow into the penis compresses the veins causing partial constriction of the venous return.

Question 25

What nervous system pathway is responsible for ejaculation?

Answer 25

Sympathetic nervous system

Question 26

What causes ejaculation ? (3)

Answer 26

.Co-ordinated smooth muscle contractions of vas deferens, glands and urethra.

•Movement of sperm into epididymis, vas deferens, penile urethra (emission).

•Expulsion of the glandular secretions & evacuation of urethra (ejaculation).

Question 27

How do antagonists of GnRH work ?

Answer 27

Antagonists of GnRH bind to GnRH receptors without stimulating it . This blocks GnRH from stimulating FSH and LH- acts as a puberty blocker

Question 28

What do all sex steroids have in common?

Answer 28

All sex steroids (progestogens and androgens) are derived from cholesterol

Question 29

What does viagra do?

Answer 29

Inhibits phosphodiesterase meaning less cGMP is converted back into GMP -> increases relaxation of arterial smooth muscle -> increased vasodilation=erection