11. Production of seminal fluid

Question 1

Evolution of male gametes?

Answer 1

Spermatocyte

• -> Spermatid
• -> Speratozoon

Question 2

What is the process of sperm transfer to epidydmis?

Answer 2

Sperm in seminiferous tubules in a large volume of fluid. Washes sperm into rete testis, vasa efferentia and epididymis
If vasa efferential blocked, seminiferous tubules and testis swells
6-12 days to travel through vasa efferntia and epididymis
Various products secreted into the seminal fluid in the epididymis

Question 3

Changes to spermatozoa in epididymis in Concentration?

Answer 3

Concentration: 100-fold (5 x 10^7/ml entering, 5 x 10^9/mol leaving)

Question 4

Changes to spermatozoa in epididymis in Sperm modelling?

Answer 4

1. Nuclear condensation and acrosome shaping completed

2. Cytoplasmic droplet shed

Question 5

Changes to spermatozoa in epididymis in motility?

Answer 5

1. ↑ disulphide bridges between proteins in outer dense fibres of tail
2. [cAMP] rises in the tail
3. Acquires the capacity for forward movement

Question 6

Changes to spermatozoa in epididymis in metabolism?

Answer 6

1. ↑ dependence on external fructose for glycoly c energy 2. Little oxidative metabolism
   ↑ Intracellular pH (due to 3. NA+/H+ exchange)

Question 7

Changes to spermatozoa in epididymis in Membrane?

Answer 7

Composition of various components change makes them more resilient to changes in temp

Question 8

Where is seminal fluid formed

Answer 8

Accessory glands

Question 9

role of seminal fluid?

Answer 9

Provides nutrients etc to protect spermatozoa.

Produces an alkaline and gelatinous fluid

Question 10

Which infectious agents exploit seminal fluid?

Answer 10

Hep B

HIV

Question 11

what are the 6 main constituents of ejaculate?

Answer 11

Spermatozoa
Fructose
Inositol
Citric acid
Glycerlyphosphoryl-choline
Acid phosphatase

Question 12

Source and function of fructose in ejaculate?

Answer 12

From seminal vesicle and ampulla

For anaerobic energy metabolism

Question 13

Source and function of inositol in ejaculate?

Answer 13

Source: Testes and epididymis
Function: Osmotic ballast to keep fluid in semen and not move into sperm (swelling)

Question 14

Source and function of citric acid in ejaculate?

Answer 14

Source: Prostate
Function: Ca2+ chelator which depresses semen coagulation

Question 15

Source and function of glyceryphosphoryl-choline in ejaculate?

Answer 15

Source: Epididymis
Function: Used as a source of choline in phospholipid metabolism

Question 16

Source and function of acid phosphatase in ejaculate?

Answer 16

Source: Prostate
Function: Cleaves choline from glycerophosphorylcholine

Question 17

What is the process by which the penis is made turgid?

Answer 17

Haemodynamic changes involving the corpora cavernosa. These are sinuses along most of the length of the penis

Question 18

3 sources of arousal?

Answer 18

– erotic psychological stimuli (e.g. visual, olfactory)
– tactile stimuli at the level of the brain
– tactile stimuli can also mediate local spinal reflexes

Question 19

Sympathetic control of erection?

Answer 19

– lower thoracic and lumbar spinal segments
– maintains flaccidity

Innervates prostate gland and seminal vesicle

Question 20

Sympathetic leads to constriction of bv everywhere apart from…

Answer 20

skeletal muscles

Question 21

Parasympathetic control of erection?

Answer 21

Control centre in sacral spinal segments
Increased activity produces turgidity

Innervates erectile tissue

Question 22

What is the tumescence of the penis?

Answer 22

Erection centre in the sacral spinal cord which mediates the erection reflex

Question 23

Action of the tumescence of the penis?

Answer 23

1. Dilatation of arterioles to c. cavernosa and c. spongiosum
2. Closing of arteriovenous shunts that normally bypass the c. cavernosa
3. Occlusion of vein draining penis

Question 24

Parasympathetic action on vascular smooth muscle during erection?

Answer 24

Relaxation of vasculature by release of ACh acting on the vascular endothelial cells.
Indirectly triggers release of NO which causes relaxation of the vascular smooth muscle

Question 25

Failure to obtain an erection can result from?

Answer 25

– mechanical damage to the c. cavernosa
– obstruction of the arteries to the penis
– drugs that block parasympathetic actions
– psychological factors
-Stress associated with high symp activity. NA causes vasoconstriction of penile arterioles and so inhibits erection.

Question 26

Sympathetic role in ejaculation?

Answer 26

– ejaculatory centre in lower thoracic and lumbar spinal cord
– signals to ducts of genital tract and to bulbocavernosus muscle at the base of penis

Question 27

What are the two phases of ejaculation?

Answer 27

Emission
– smooth muscle contraction in walls of the genital tract
– expels semen into urethral bulb

Expulsion
– rhythmic contractions of penis and bulbocavernosus muscle
– ejects semen in spurts

ejaculation normally followed by a refractory phase of 10 mins to an hour

Question 28

Order of ejaculate composition?

Answer 28

First component: Prostate
Rich in acid phosphatase and citric acid

Second component: Vas deferens
Rich in spermatozoa

Third component: Seminal vesicle
Rich in fructose

Coagulation followed by liquefaction

Question 29

How does sildenafil/viagra work to produce erections?

Answer 29

Inhibitors of PDE V.
In NO pathways to produce vasodilation the cGMP can be inactivated by PDE V. If inactivation is inhibed then the cGMP and continue it’s reaction to…
cGMP–> PKG –> Vasodilation and erection