Male Reproduction

Question 1

What are the functions of the male reproductive tract

Answer 1

Testis: sperm production and steroid hormone production

Epididymis: sperm collection and maturation

Ductus deferens: transport and storage

Accessory glands: contributions to seminal fluid

Urethra: transport

Seminiferous tubules: sperm production

Question 2

Where does the majority of testosterone synthesis occur?

Answer 2

Leydig cells

Question 3

Describe the process steroid binding to its receptor

Answer 3

Steroid bind to receptor

This produces a complex that acts on DNA

Binding of the complex to sites on DNA alters the the genes being expressed by target cells

Question 4

Describe the process of androgens binding to their receptor

Answer 4

Androgens interact with AR - all major cell populations in the testis, epididymis and accessory glands express AR

Androgen-AR binding is needed in sperm production, transport and activation

Question 5

Why are androgens important?

Answer 5

They are responsible for the development of secondary sex characteristics, anabolic effects and spermatogenesis

Question 6

Describe the HPO axis for the production of spermatozoa and sex steroids

Answer 6

Hypothalamus stimulated to secrete GnRh which acts on the anterior pituitary to stimulate the secretion of LH and FSH which have their effect on the testis to produce spermatozoa and sex steroids

Question 7

Describe gonadotropin action in the testis

Answer 7

Androgen binding protein (ABP) binds to testosterone and DHT and concentrated them in the luminal fluid of the seminiferous tubules and downstream regions f the male tract

Question 8

What does ABP binding stimulate?

Answer 8

Spermatogenesis in the seminferous tubules
Spem maturation in the epididymis
Accessory gland secretions
Myoid cell contractile activity to propel sperm along the tract

Question 9

Describe the process of spermatogensis

Answer 9

Maturation stages are androgen-dependent

Myoid cell contractility is required to to move released sperm along the seminiferous tubule
Myoid cells are AR positive, action is androgen-dependent

At the point of release of sperm into the lumen of the tubule, sperm are not yet motile

The ability to swim is initially acquired in the epididymis with further activation in the female tract

Question 10

Describe the composition of semen

Answer 10

Volume of ejaculate: 1.5-5.0ml
Sperm count: 40-250 million/ml
Leukocyte count: 0-200/ml (indicative of UTI)

Question 11

How does an erection occur?

Answer 11

Erectile tissue becomes engorged with blood, arterioles dilated as a result of parasympathetic nervous system activity

Question 12

What are the causes of erectile dysfunction?

Answer 12

Pathological causes: psychogenic, neurogenic, vascular and endocrine

Latrogenic causes: drugs such as SSIRs, tricyclics, antihypertensives

Question 13

What are the symptoms of prostate cancer?

Answer 13

Urgent and frequent urination
Nocturnal enuresis
Difficulty starting or emptying the bladder
Urine flow weak, interrupted or difficult to control
Back/pelvic pain

Question 14

What is the treatment for prostate cancer?

Answer 14

GnRH agonists and antagonists
Androgen antagonist: cyproterone acetate
5⍺ reductase inhibitors: dustasteride and finesteride

Question 15

Give a use of anabolic steroids

Answer 15

Treatment of some aplastic anaemias

Question 16

How can testosterone be used as a contraceptive?

Answer 16

Exogenous testosterone reduces LH and FSH which reduces fertility

Question 17

What is the disadvantage of using exogenous testosterone as a contraceptive?

Answer 17

High doses are needed as it is difficult to reduce sperm count - can lead to iatrogenic hypogonadotropic hypogonadism

Question 18

Give an example of male contraceptive other than exogenous testosterone

Answer 18

Vasalgel - Reversible inhibition of sperm under guidance
Soft gel is injected into the lumen of the vas deferent
Sperm can’t penetrate and are reabsorbed