Lecture 5: Physiology of the Male Reproductive System

Question 1

What are the seminiferous tubules composed of, and what is their purpose?

Answer 1

sertoli cells (spermatogenesis) and leydig cells (testosterone production)

Question 2

How are sperm moved from the seminiferous tubules?

Answer 2

There is a layer of contractile smooth muscle surround the Leydig cells to force out the sperm (sperm are initially immotile)

Question 3

What is the purpose of tight junctions (blood-testis barrier)?

Answer 3

Sperm are immunogenic

Question 4

How long does spermatogenesis take?

Answer 4

70 (+-4) days

Question 5

What is the structure of sperm?

Answer 5

1. Acrosome
2. Nucleus
3. Mid-piece
4. Principal piece
5. Tail

Question 6

What is the composition of semen and each components purpose (when are they released)?

Answer 6

Spermatozoa (<10%)
o 15-150 million per millilitre

Seminal vesicle fluid (60%) – last to be ejaculated
o Fructose and other nutrients for the sperm
o Fibrinogen to clot semen (keep it lodged in female reproductive tract)
o Prostaglandins to stimulate the uterus
o Last volume to be ejaculated

Prostate gland secretions (20%)
o Thin, milky, alkaline secretions (to neutralize some of the acid in the female reproductive tract)
o Prostate specific antigen (PSA)- Proteases to break down clotted semen
o Acid phosphatase to activate sperm

Bulbourethral gland secretions (10% released prior to ejaculation (pre-ejaculate)
o Mucoproteins to neutralize any urine in the urethra and lubricate the urethra

Question 7

______ must occur before sperm are capable of penetrating and fertilizing the ovum

Answer 7

Capacitation

Question 8

How long can sperm survive?

Answer 8

• Weeks in the male reproductive tract

- 24-72 hours in the female reproductive tract

Question 9

sperm clots at the base of the __?

Answer 9

cervix

Question 10

FSH and LH are produced by the ______ cells in the anterior pituitary

Answer 10

same

Question 11

___ acts upon the leydig cells to stimulate the production of testosterone
____ acts on the sertoli cells to support the process of spermatogenesis and to promote LH receptor synthesis on the leydig cells

Answer 11

LH and FSH

Question 12

How does testosterone promote spermatogenesis?

Answer 12

Testosterone has paracrine action on Sertoli cells, promoting spermatogenesis. Testosterone is also converted into other hormones including estradiol and 5α-dihydrotestosterone in the periphery. These come back to the testes through the circulation and promote spermatogenesis.

Question 13

the rate of spermatogenesis is accompanied by the production of ______ at the same rate? It only acts on…

Answer 13

inhibin and it only acts on FSH

Question 14

There is a small spike in testosterone at ?

Answer 14

Birth