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ANSC 312 - Repro Physiology > Midterm 2 - Lecture 16 > Flashcards

Midterm 2 - Lecture 16 Flashcards

1
Q

Two important roles of the scrotum and spermatic cord

A
  1. support and maintain the male gonads
  2. regulate testicular temp
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2
Q

At what temperature must spermatogenesis occur at?

A
  • lower than normal body temp
  • internal testicular temperature is generally 4-6 degrees below rectal temperature
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3
Q

What 5 key tissues are involved in thermoregulation?

A
  1. testicular artery
  2. pampiniform plexus
  3. external cremaster muscle
  4. scrotum skin
  5. tunica dartos muscle
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4
Q

What is the pampiniform plexus?

A

specialized vascular network found within the spermatic cord
- consists of testicular veins that elaborately intertwine around the testicular artery

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5
Q

What is the function of the pampiniform plexus?

A
  • provides a countercurrent heat exchange mechanism that cools the arterial blood before it enters the testicle
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6
Q

What is the cremaster muscle?

A
  • striated muscle that surrounds the spermatic cord and attaches to the testicular connective tissue
  • contraction to draw the testes close to the body during cold periods (NOT CONSTANT)
  • muscle relaxes during periods of high temp so testes move away from the body = cooler AND lengthens the PP for greater SA for countercurrent heat exchange to fxn
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7
Q

4 major layers of the scrotum

A
  1. Scrotal skin
    - rich in sweat glands and sensory tissue
  2. Tunica dartos
    - smooth muscle that responds to temperature
  3. Scrotal fascia
    - connective tissue
  4. Parietal vaginal tunic
    - connective tissue
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8
Q

What does sweating of the scrotal skin allow for?

A
  • the scrotum & testes to be cooled by evaporation
  • scrotum heavily populated with sweat glands and thermosensitive nerves
  • scrotal glands are innervated by sympathetic nerves
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9
Q

What controls the degree of scrotal sweating and or respiratory rate via a reflex pathway?

A
  • scrotal sensory nerves
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10
Q

What do scrotal sensory nerves do?

A

Control the degree of scrotal sweating and/or respiratory rate via a reflex pathway

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11
Q

What does scrotal warming induce?

A
  • panting at 40 degrees
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12
Q

How is respiration linked to scrotal temperature?

A
  • respiration rate increases if scrotal skin temp reaches 36 degrees
  • at 40 degrees the ram will pant
  • warming an equivalent region of the body surface does not elicit the same response
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13
Q

What is the tunica dartos?

A
  • mesh like smooth muscle that lies beneath the scrotal skin
  • degree of contraction constantly adjusting in response to scrotal temp - as detected by sensory nerves in the scrotal skin
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14
Q

What does the Tunica Dartos do in cold periods vs hot periods?

A
  1. Cold periods - smooth muscle can maintain sustained contraction to hold the testes close to the body
  2. Hot periods - muscle relaxes and testes move away from the body = cooler AND greater SA to be cooled by evaporation of perspiration
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15
Q

What are the 2 mechanisms of testicular cooling?

A
  1. Heat dissipation
    - pampiniform plexus = countercurrent heat exchange
    - scrotal skin (sweat glands) = perspiration
  2. Testes position
    - cremaster muscle
    - tunica dartos (relaxes)
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16
Q

What are the effects of short-term heat exposure? (ex. fever, summer heat)

A
  • compromises sperm viability
  • reduced sperm motility
  • poor embryo survival following fertilization
17
Q

What are the effects of long-term heat exposure?

A
  • cessation of spermatogenesis
  • spermatogenic DNA polymerase b and recombinase activity is reduced
18
Q

What are varicoceles?

A
  • abnormal collection of dilated veins in the spermatic cord (varicose veins)
  • impedes the ability of the Pampiniform Plexus to cool arterial blood before it reaches the testes
  • caused infertility or reduced fertility
  • not common in livestock but highly heritable
19
Q

What is thermal “castration” aka short “scrotumed” bulls?

A
  • testes are forced close to the body by placing a rubber band around the lower portion of the scrotum
  • creates an artificial cryptorchid
  • bull is sterile, but experiences better growth efficiency and leaner carcasses due to continued T4 production by testes
20
Q

Why is thermal castration not a common practice?

A
  • elevated T4 causes aggressive behaviour amongst bulls = difficult to manage!
21
Q

What is a noninvasive means to evaluate testicular cooling capacity?

A
  • infrared thermography
  • males with inefficient testicular cooling can be identified and eliminated as breeding males
22
Q

What is unique about mammals who do not have scrotal sacs and instead the testes remain within the abdomen?

A
  • have a relatively low body temp
  • many have evolved unique cooling systems to regulate body and testicular temp

ANSC 312 - Repro Physiology (21 decks)

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