Production of seminal fluid

Question 1

What is the structure of the tail of the sperm called?

Answer 1

9 + 2 axonemal structure

Question 2

What is thought to be the overall length of the seminiferous tubules?

Answer 2

~ 250m

Question 3

How many sperms cells are released per ejaculate?

Answer 3

~ 20 million

Question 4

What is the epididymis is comprised of what?

Answer 4

Head, body and tail

Question 5

How much sperm can the tail of the epididymis contain?

Answer 5

100 million

Question 6

What happens when the sperm travels from the end of the body to the tail?

Answer 6

They become fully active ready for capacitation (journey can last 6 - 12 days)

Question 7

How long after a vasectomy are men still advised to use protection?

Answer 7

3 - 4 months

Question 8

What are the changes that hapeen to the spermatozoa in the epididymis?

Answer 8

• 100 fold increase in concentration
• Sperm are remodelled: nuclear condensation and acrosome shaping, cytoplasmic droplet shed
• Increased dependance on external fructose for glycolytic energy, little oxidative metabolism
• Increased intracellular pH (due to Na+/H+ exchange)
• Increased motility dueto increased disulphide bridges between proteins in outer dense fibres of tail, cAMP rises in tail, able to move forward
• Composition of membrane changes

Question 9

By how much does the sperm concentration change in the epididymis?

Answer 9

100-fold (5x10^7/ml to 5x10^9/ml leaving)

Question 10

How long is the epididymis if spread out?

Answer 10

~ 4m

Question 11

How many parts of the vas deferens are there?

Answer 11

5

Question 12

What is the proportion of muscle to lumen in the vas deferens

Answer 12

10:1 (most muscle abundant tube in human body, used to propel sperm)

Question 13

What are the functions of the vas deferens?

Answer 13

• Propels sperm
• Gives sperm glycoproteins
• Absorption features which get rid of dead sperm

Question 14

What is the volume produced by each gland?

Answer 14

• Testes: 0.1-0.2 ml
• Seminal vesicle: 1-3ml
• Prostate 0.5-1ml
• Bulbourethral glands 0.1-0.2ml

Question 15

What does the bulbourethral glands produce?

Answer 15

Viscous, clear, alkaline fluid, lubricates urethra

Question 16

What are the constitutes of the seminal vesicle?

Answer 16

alkaline, gelatinous

Question 17

What does the prostate secretion contain?

Answer 17

acidic, watery

Question 18

What are the major constituents of ejaculate?

Answer 18

• Spermatozoa (50 - 150)
• Fructose (8-37)
• Inositol (1-3)
• Citric acid (5-73)
• Glycerylyphosphorylcholine (2-3)
• Acid phosphatase

Question 19

Where is fructose produced?

Answer 19

Seminal vesicle and ampulla

Question 20

Where is citric acid produced?

Answer 20

Prostate

Question 21

Where is glycerylphosphoryl-choline produced?

Answer 21

Epididymis

Question 22

Where is acid phosphatase produced?

Answer 22

Prostate

Question 23

How does the penis become turgid?

Answer 23

• Haemodynamic changes

- Involves corpus cavernosa (sinuses along length of penis)

Question 24

What is fructose used for?

Answer 24

Anaerobic energy metabolism

Question 25

What does inositol do?

Answer 25

Osmotic ballast

Question 26

What does citric acid do?

Answer 26

Ca2+ chelator - Depresses semen coagulation

Question 27

What does glycerlyphosphorylcholine do?

Answer 27

Used as a source of choline in phospholipid metabolism

Question 28

What does acid phosphatase do?

Answer 28

Cleaves choline from glycerophosphorylcholine

Question 29

What is the main veins of the penis?

Answer 29

• Subcutaneous dorsal vein

- Deep dorsal vein

Question 30

What are the arteries in the penis?

Answer 30

Dorsal artery, profunda artery, circumflex artery, cavernous artery, hecline arteries

Question 31

What is the main nerve of the penis?

Answer 31

Dorsal nerve

Question 32

What can arousal be produced by?

Answer 32

• Erotic psychological stimuli (eg visual, olfactory)
• Tactile stimuli at the level of the brain
• Tactile stimuli can also mediate local spinal reflexes

Question 33

What maintains flaccidity?

Answer 33

Lower thoracic and lumbar spinal segments

Question 34

What increases turgidity?

Answer 34

• Increased activity of parasympathetic control centre in sacral spinal segments
• Shunts between arteries and veins close
• Dilation of arterioles to c. cavernosa and c. spongiosum

Question 35

What are the 3 main components of ejaculate?

Answer 35

1st component: Prostate 
- Rich in acid phosphatase and citric acid 
2nd component: Vas deferens 
- Rich in spermatozoa
3rd component: Seminal vesicle
- Rich in fructose

Question 36

What follows coagulation?

Answer 36

Liquefaction

Question 37

How long is the refractory phase

Answer 37

10 minutes to an hour

Question 38

How does parasympathetic stimulation relax vascular smooth muscle?

Answer 38

• Para action involves ACh acting on vascular endothelial cells
• Indirectly triggers release of nitric oxide
• NO causes relaxation of vascular smooth muscle

Question 39

What enzyme is activated after ejaculation?

Answer 39

PDE V (PDE V catalyses cGMP to an acive product0

Question 40

What type of compound is Viagra or Sildenafil?

Answer 40

PDE V inhibitor (also used to treat pulmonary hypertension)

Question 41

WHat can failure to obtain an erection be due to?

Answer 41

• Mechanical damage to c cavernosa
• Obstruction to arteries of the penis
• Drugs that block parasympathetic actions
• Psychological
• Stress associated with high sympathetic activity, NA causes vasoconstriction of penile arterioles and so inhibits erection

Question 42

What are the 2 phases of ejaculation?

Answer 42

Emission phase
- SM contraction in walls of genital tract
- Expels semen into urethra; bulb
Expulsion phase
- Rhythmic contractions of penis and bulbocavernous muscle
- Ejects semen in spurts