Lecture 23: Male Reproduction

Question 1

What is primary sex organs and what is their function?
What are the accessory reproductive organs?
What do sex hormones play roles in?

Answer 1

Primary sex organs (gonads): testes
-produce sex cells (gametes)
-secrete steroid sex hormones, androgens
Accessory reproductive organs: ducts, glands and external genitalia
Sex hormones play roles in:
-development and function of the reproductive organs
-sexual behaviour and drives
-growth and development of many other organs and tissues

Question 2

Sperm are delivered to the exterior through a system of ducts, what are they?
Name the accessory sex glands, what do they do with their secretions?

Answer 2

The system of ducts is the epidiymis, ductus deferens, ejaculatory duct and the urethra
Accessory sex glands: seminal vesicles, prostate, and bulborethral glands
-empty their secretions into the ducts during ejaculation

Question 3

Be able to label the diagram of the male penis on slide 7

Answer 3

Do it!

Question 4

The scrotum. What is its anatomy?

Temp is kept constant by two sets of muscles, what are they?

Answer 4

It’s a sac of ski. And superficial fascia
-hangs outside abdominopelvic cavity
-contains paired testes
-3 degrees lower than core body temp needed for sperm production
Temperature is kept constant by two set of muscles:
-smooth muscle that wrinkles scrotal skin (dartos muscle)
-bands of skeletal muscle that elevate the testes (cremaster muscles)

Question 5

Be able to label the diagram on slide 7

Answer 5

Do it!

Question 6

The testes.
What are the 2 tunics that surround the testes?
Sperm are conveyed through?

Answer 6

Each is surrounded by two tunics: 
A) tunica vaginalis
B) tunica albuginae, the fibrous capsule 
The septa divide the testis into 250-300 lobules, each containing 1-4 seminiferous tubules (site of sperm production) 
Sperm are conveyed through
-seminiferous tubules
-rete testes
-efferent ductules
-epididymis

Question 7

The testes

Blood supply?

Answer 7

Blood supply comes from the testicular arteries and exits by the testicular veins

• spermatic cord encloses nerve fibres, blood vessels, and lymphatics that supply the testes
• interstitial (Leydig) cells outside the seminiferous tubules produce androgens

Question 8

Be able to label the diagram of the testes on slide 10

Answer 8

Do it!

Question 9

The penis which is the external genitalia.

What does the penis consist of?

Answer 9

Penis is the male copulatory organ
The penis consists of:
-root and shaft that ends in the glans penis
-prepuce, or foreskin- the cuff of loose skin covering the glans
-crura: the proximal end surrounded by ischiocavernosus muscle; anchors penis to the pubic arch.
Spongy urethra and 3 cyclical bodies of erectile tissue (spongy network of connective tissue and smooth muscle with vascular spaces)
-corpus spongiosum: surrounds the urethral and expands to form the glands and bulb
-corpora cavernosa are paired dorsal erectile bodies

Question 10

Be able to label diagram on slide 14

Answer 10

Do it!

Question 11

What are the four parts of the male duct system

Answer 11

Epidiymis
Ductus deferens
Ejaculatory duct
Urethra

Question 12

Epididymis

Answer 12

Head: duct of the epididymis

• nonmotile sperm enter, pass slowly through, and become motile
• during ejaculation the epididymis contracts, expelling sperm into the ductus deferens

Question 13

Ductus deferens and ejaculatory duct

Answer 13

Ductus deferens
-passes through the inguinsl canal
-expands to form the ampulla and then joins the duct of the seminal vesicle to form the ejaculatory duct
Propels sperm from the epididymis to the urethra
-vasectomy: cutting the ductus deferens as form of birth control

Question 14

Urethra

Answer 14

Conveys both urine and semen (at different times) 
Has three regions: 
1. Prostatic urethra 
2. Membranous urethra 
3. Spongy (penile) urethra

Question 15

Accessory gland: Seminal vesicles

Answer 15

Produces viscous alkaline seminal fluid
-fructose, ascorbic acid, coagulating enzyme, and prostaglandins
-70% of the volume of semen
Duct of the seminal vesicle joins the ductus deferens to form the ejaculatory duct

Question 16

Accessory glands: prostate

Answer 16

Encircles part of the urethra inferior to the bladder
-secretes milky, slightly acidic fluid:
Contains:
-citrate, enzymes, and prostate-specific antigen (PSA)
-plays a role in the activation of sperm
-enters the prostatic urethral during ejaculation

Question 17

Accessory glands: bulbourethral glands

Answer 17

• pea size glands inferior to the prostate
• prior to ejaculation, produce thick, clear mucus
• lubricates the glans penis
• neutralises traces if acidic urine in the urethra

Question 18

Semen

Answer 18

• mixture of sperm and accessory gland secretions
• contain nutrients (fructose), protects and activates sperm, and facilitates their movement
• alkalinity neutralises the acid in the male urethra and female vagina
• antibiotic chemicals destroy certain Bastia
• clotting factors coagulate semen just after ejaculation
• only 2-5ml of semen are ejaculated, containing 20-150 million sperm/ml

Question 19

Male sexual response

Answer 19

Erection:

• parasympathetic reflex
• erectile tissue fills with blood
• expansion if the corpora cavernosa
  
  • compresses drainage veins and maintains engorgement
• corpus spongiosum keeps the urethra open
• impotence: the inability to attain erection

Ejaculation:

• propulsion of semen from the male duct system
• sympathetic spinal reflex causes:
• ducts and accessory glands to contract and empty their contents
• bladder sphincter muscle to constrict, preventing expulsion of urine
• bulbospongiosum muscles to undergo a rapid series of contractions

Question 20

Spermatogenesis

Answer 20

Sequence of events that produces sperm in the seminiferous tubules of the testes
Most body cells are diploid (2n) and contain:
-2 sets of chromosomes (one maternal, one paternal)
-23 pairs of homologous chromosomes
Gametes are haploid (n) and contain
-23 chromosomes
Spermatogonia:
Begins at puberty
-stem cells in contact with the epithelial basal lamina

Question 21

What is the role of the sustentacular cells?

Answer 21

Large supporting cells (sertoli cells)

• provide nutrients and signals to dividing cells
• secrete testicular fluid into lumen for transport of sperm

Question 22

Male secondary sex characteristics:

Answer 22

Features induced in the nonreproductive organs by male sex hormones (mainly testosterone)

• appearance of pubic, axillary and facial hair
• enhanced growth of the chest and deepening of the voice
• skin thickens and becomes oily
• bones grow and increase in density
• skeletal muscle increase in size and mass