14 - Spermatic Cord & Scrotum: Thermoregulation

Question 1

Roles of scrotum and spermatic cord

Answer 1

• support and maintain the male gonads
• regulate testicular temps

Question 2

What temps does spermatogenesis need to occur at?

Answer 2

Temps lower than normal body temperatures
- internal testicular temps generally 4-6C below rectal temp

Question 3

Scrotum skin has what

Answer 3

• sweat glands
• sensory tissue

Question 4

Slides 8, 9, 10

Answer 4

Spermatic cord

Question 5

What is the pampiniform plexus? Its role?

Answer 5

Specialized vascular network found within the spermatic cord
Consists of testicular veins that intertwine around the testicular artery

Provides countercurrent hear exchange mechanism that cools the arterial blood before it enters the testicle

Question 6

Slide 13

Answer 6

Countercurrent heat exchange

Question 7

Slide 13

Answer 7

Countercurrent heat exchange

Question 8

What is the cremaster muscle

Answer 8

Striated muscle that surrounds the spermatic cord and attaches to the testicular connective tissue

Question 9

What does the cremaster muscle do

Answer 9

• contracts to draw the testes close to the body during cold periods
• relaxes during periods of high temps: testes move away from the body

Question 10

Why does the cremaster muscle move testes away from the body

Answer 10

• cooler away from the body
• lengthens the pampiniform plexus allowing for greater surface area for countercurrent heat exchange to function

Question 11

Four layers of scrotum. Their roles

Answer 11

1. Scrotal skin: sweat glands and sensory tissue
2. Tunica dartos: smooth muscle that responds to temp
3. Scrotal fascia: connective tissue
4. Parietal vaginal tunic: connective tissue

Question 12

What does the scrotal skin do

Answer 12

Sweating allows the scrotum & testes to be cooled by evaporation
- scrotal sensory nerves control the degree of scrotal sweating

Question 13

Slides 17-19

Answer 13

Scrotal sweating

Question 14

What induces panting in males

Answer 14

Scrotal warming
Sends signal to respiratory center when ~40C in rams

Question 15

When does respiration rate increase in rams? Panting?

Answer 15

Increases if scrotal skin temp = 36C

Ram begins to pant at 40C scrotal skin temp

*warming an equivalent region of the body surface does not elicit same response

Question 16

What is the tunica dartos

Answer 16

Mesh like smooth muscle that lies beneath the scrotal skin
Degree of contraction constantly adjusting in response to scrotal temps (as detected by sensory nerves in the scrotal skin)

Question 17

Tunica dartos in cold vs hot periods

Answer 17

Cold: smooth muscle maintains sustained contraction to hold testes close to body
Hot: muscle relaxes and testes move away from body
- cooler away from body
- greater scrotal surface area to be cooled by evaporation of perspiration

Question 18

Two mechanisms of testicular cooling, structures

Answer 18

1. Heat dissipation
   - pampiniform plexus (countercurrent heat exchange)
   - scrotal skin (sweat glands) = perspiration
2. Testes position
   - cremaster muscle
   - tunica dartos

Question 19

Effects of short term testicular overheating

Answer 19

Compromised sperm viability (e.g. fevers, summer heat)
- reduced sperm motility
- poor embryo survival following fertilization

Question 20

Effects of long-term testicular overheating

Answer 20

Long term heat exposure causes cessation of spermatogenesis
- spermatogenic DNA polymerase b and recombinase activity is reduced

Question 21

Slide 24

Answer 21

important diagram

Question 22

What are varicoceles

Answer 22

Abnormal collection of dilated veins in the spermatic cord (varicose veins)

Question 23

What is the result of varicoceles

Answer 23

Impedes ability of the pampiniform plexus to cool arterial blood before it reaches the testes
Caused reduced fertility or infertility

Question 24

What are short “scrotumed” bulls

Answer 24

• testes are forced close to the body by placing rubber band around lower portion of scrotum
• this creates an artificial cryptorchid
• bull is sterile, but experiences better growth & efficiency & leaner carcasses due to continued T4 production by testes

Question 25

How do we select for testicular cooling capacity

Answer 25

Infrared thermography
- noninvasive means to evaluate testicular cooling capacity
- males with inefficient testicular cooling can be identified and eliminated as breeding males (good thermoregulation = more fertile)

Question 26

What mammals do not have scrotal sacs? How do they thermoregulate?

Answer 26

Seals, dolphins, whales, elephants have testes that remain in the abdomen
- have relatively low body temperature
- many have evolved unique cooling system to regulate body and testicular temps