Erection and ejaculation

Question 1

Define libido?

Answer 1

Behavioural manifestation of sexual desire.

Question 2

Define intromission?

Answer 2

Entrance of the penis into the vagina.

Question 3

Define emision?

Answer 3

Movement of accessory gland fluid into male urethra to mix with sperm.

Question 4

Define ejaculation?

Answer 4

Reflex expulsion of sperm from male reproductive tract

Question 5

What are the three parts of the penis?

Answer 5

• Crura (legs of penis attached to
ischiatic arch)
• Body
• Glans

Question 6

What do the paired ischiocavernosum muscles do and where are they?

Answer 6

— Originates at ischial arch and inserts on root of penis

— They force blood into corpus cavernosum and corpus spongiosum.

Question 7

What do the urethralis and bulbospongiosis muscle surround?

Answer 7

The urethra.

Question 8

Where do the paired retractor muscles originate and insert? And what are their function?

Answer 8

— Originates at caudal vertebrae and inserts on
• Sigmoid flexure (ruminants! pig) or
• Distal penis
— Allows for retraction / protrusion of the penis

Question 9

What needs to happen for an erection to occur?

Answer 9

. Overall erection requires:
— Elevated arterial blood inflow
— Dilation of corporal sinusoids
— Restricted venous outflow
— Elevated intra-penile pressure
— Relaxation of the retractor penis muscle

Question 10

What is erectile tissue surrounded by?

Answer 10

. Erectile tissue is surrounded by a heavy capsule of

varying thickness called the tunica albuginea.

Question 11

What do the connective tissue trabeculae that penetrate into the erectile tissue break the space up into and what are these spaces lined with?

Answer 11

Connective tissue trabeculae penetrate into the erectile tissue and break up the space into sinusoids
Sinusoids are lined by endothelium.

Question 12

How does the ischiocavernosus aid in erection?

Answer 12

— contraction causes compression of penile
veins.
— Intermittent contractions of this muscle cause
pump like action at base of penis.
_engorgement of cavernous tissues causes a blockage of venous return.

Question 13

How does the parasympathetic nervous system cause and erection?

Answer 13

Parasympathetic fibres inhibit (relax) longitudinal muscle fibers in helicine arteries
>blood flows into central sinusoids
->swelling
->results in compression of oblique veins
-> further penile swelling

Question 14

In the dog how does the female repro tract aid erection?

Answer 14

Constrictor vestibulae muscle contraction

of the female restricts outflow from dog penis and this is called a copulation lock.

Question 15

What is the principle neurotransmitter that drives erectile tissue?

Answer 15

Nitric Oxide is the principle neurotransmitter

that drives the erectile process

Question 16

What causes the helicine arteries to relax?

Answer 16

— cGMP causes smooth muscle of helicine arteries to relax.

Question 17

How does viagra work?

Answer 17

— cGMP is broken down to GTP by phosphodiesterase 5 (PDE5)

— Sildenafil citrate (Viagra) blocks the action of PDE5.

Question 18

How does erection work in a fibroelastic penis?

Answer 18

BULL, RAM, BOAR

Length increased by straightening of sigmoid flexure as a result of relaxation of retractor penis.

Question 19

How does erection work in musculocavernosus penis?

Answer 19

HORSE AND CARNIVORES

Allow expansion in diameter and length during erection.

Question 20

Which parts of the nervous system are involved in (a) erection and (b) ejaculation?

Answer 20

(a) parasympathetic (via pelvic nn to Pelvic plexus then via fine nerves)
(b) sympathetic (via hypogastric nn to the pelvic plexus then via blood vessels)

Question 21

What causes loss of erection?

Answer 21

Loss of erection sympathetic tone predominates

• > close of helicine arteries
• > blood flows out of sinusoids and erection subsides slowly

Question 22

What causes ejaculation?

Answer 22

*Stimulation of the glans penis (pressure and temperature) via the internal pudendal nerve to the lumbosaccral region of the spinal cord.
*Firing of nerves within the spinal cord.
Reflex innervation of;
— Urethralis muscle
(bulbospongious)
— Ischiocavernosus

Question 23

Features of stallion ejaculate?

Answer 23

— Sperm rich fraction ejaculated in 3 to 4 squirts

— Last 5 to 8 squirts are at lower pressure + less sperm

Question 24

Features of Boar ejaculate?

Answer 24

— First fraction: accessory fluids + few sperm
– 2nd fraction: rich in spermatozoa
— Final fraction: thick coagulum (prevents loss of sperm
from vagina)

Question 25

Features of Dog ejaculate?

Answer 25

— Pre-sperm fraction from prostate
— Sperm rich fraction
— Prostate derived fraction delivered with greater force
(forces sperm rich fraction into the uterus)

Question 26

What are some venereal pathogens of the horse?

Answer 26

. Equine herpesvirus 3
. Equine viral arteritis virus
. KJejeî,pneumoniae
. Pseudomonas aeruginosa
• Taylorella equigenitalis  (organism
associated with equine metritis)

Question 27

Campylobacter fetus is a commensal pathogen in the bull and they can carry no clinical signs and it shows no effect on semen quality. When is it a danger?

Answer 27

Contaminated semen (mating, AI) results in uterine infection and devastating infertility or early pregnancy loss.
Bulls can be cross-contaminated by sharing bedding

Question 28

Haemophilus somnus is an organism found in up to 30% of normal cows and 80% of normal bulls. What can it cause in bulls and cows?

Answer 28

— In cows
. May cause vaginitis, cervitis, endometritis and abortion.
— In bulls
Normally asymptomatic but may cause epididymitis
and testicular degeneration

Question 29

erection is?

ejaculation is?

Answer 29

parasympathetic

sympathetic