Male reproductive organs LO1, LO2

Question 1

Penis

Answer 1

Designed to deliver sperm to the female reproductive
tract
Penile erection:
Parasympathetic nerves to penile arterioles release
nitric oxide (NO)
1. Blood vessels dilate
2. Increased blood flow to penis
3. Vascular channels become engorged with blood
4. Erection of penis occurs

Question 2

Scrotum

Answer 2

Sac of skin housing the testes outside the abdominal
cavity of the body
- temperature regulation of testes (maintain optimal temperature for sperm production)
– Dartos muscle (smooth muscle) - contracts to make scrotum wrinkled and thick, decreases heat loss
– Cremaster muscle (skeletal muscle) – contracts to bring
scrotum and testes closer to body
– Both muscles contract in cold, and relax in warm, temperatures

Question 3

Testes

Answer 3

Each lobule contains seminiferous tubules
- factory for sperm
- Each seminiferous tubule is surrounded by smooth
muscle to help squeeze sperm out of testes and into
the epididymis

Question 4

Epididymis

Answer 4

Functions:
1. Stores, nourishes and protects spermatozoa
2. Facilitates functional maturation
3. Recycles damaged sperm
4. Ejaculates the sperm
- Sperm arrive as immature, non-motile spermatozoa.
- takes ~ 20 days to move through the epididymis, after which time, they are capable of swimming
- Sperm are stored in the tail of the epididymis for
several months
- Sperm are ejaculated from the epididymis into the
ductus deferens

Question 5

Sperm travels..

Answer 5

– Epididymis
– Ductus/Vas deferens
– Ejaculatory ducts
– Urethr

Secretions are added to the sperm by the accessory glands:
– Seminal vesicles
– Bulbourethral gland
– Prostate

Question 6

Ductus Deferens &
Seminal Vesicles

Answer 6

Sperm ejaculated from the epididymis enter the ductus
deferens
– Ductus deferens is a tube that runs from the scrotal sac up into the abdominal cavity, then downward towards the urethra
- Seminal vesicles attach to the ductus deferens.
– Release a viscous fluid which makes up 60-70% of semen volume and contains substances that enhance sperm motility and their ability to fertilise an ovum

Question 7

Ejaculatory Duct, Urethra &
Prostate

Answer 7

After the seminal vesicles join the vas deferens, the
tube becomes known as the ejaculatory duct
- The ejaculatory duct is very short and immediately joins
the urethra and travels through the prostate gland
- The prostate gland - a doughnut shaped gland that
surrounds the urethra and produces fluid that accounts
for up to 30% of semen volume
- The urethra descends through the prostate and down to the tip of the penis (within the corpus spongiosum)
- The paired bulbourethral glands are located inferior to
the prostate on either side of the urethra

Question 8

Ejaculation

Answer 8

• Sympathetic response
• Bladder sphincter muscle constricts
• Reproductive ducts and accessory glands contract
• Bulbospongiosum muscle of penis contracts to eject
  semen

Question 9

Spermatogenesis

Answer 9

Sperm production
– Occurs in the seminiferous tubules of the testes
– Begins at approximately 14 years of age
– Results in 400 million new sperm per day!
– Continues throughout adult life
– Each mature sperm takes about 10 weeks to make!

Question 10

Gametes

Answer 10

Body cells
- 46 chromosomes as 23 pairs
- termed diploid or 2n
gametes
- 23 chromosomes (one of ear pair)
- termed haploid or n

Question 11

Meiosis

Answer 11

Meiosis is the nuclear division in the gonads in which the number of chromosomes is halved (from 2n to n)
* When fertilization occurs, the normal diploid
chromosomal number is restored (in human, 2n = 46)

Question 12

Sperm structure

Answer 12

Head: genetic region; nucleus and a vesicle (acrosome) containing enzymes that enable the sperm to penetrate an ovum
Midpiece: metabolic region,
mitochondria - energy
Tail: locomotor region;
flagellum –> movement

Question 13

hypothalamic-pituitarygonadal (HPG) axis

Answer 13

• The testes make sperm
  and hormones
• These activities require
  interactions with the
  hypothalamus and anterior
  pituitary

Question 14

HPG(hypothalamic-pituitary-gonadal) axis:

Answer 14

1. The hypothalamus releases GnRH
2. GnRH signals the release of FSH and LH from the anterior pituitary
3. FSH stimulates sustenocytes (Sertoli cells) in the seminiferous
   tubules to produce ABP which concentrates testosterone
4. LH stimulates interstitial (Leydig) cells in the seminiferous tubules
   to produce testosterone
5. Concentrated testosterone drives spermatogenesis
6. Increased testosterone levels negatively feed back to inhibit GnRH and FSH/LH release
7. Inhibin is also produced during spermatogenesis and has negative feedback effects on FSH and GnRH

Question 15

testosterone

Answer 15

• Stimulates spermatogenesis
• Increases growth of reproductive ducts and glands
• Increases size of penis
• Enhances ability to maintain erection and obtain
  ejaculation
• Stimulates male secondary sex characteristics