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Horse Systems and Management > Stallion-Reproductive Anatomy > Flashcards

Stallion-Reproductive Anatomy Flashcards

1
Q

what does a stallion’s reproductive organs consist of? (6)

A
  1. 2 testes
  2. scrotum
  3. epididymis
  4. two ductus deferens
  5. accessory sex glands
  6. penis
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2
Q

what is each testis suspended by? (2)

A

spermatic chors and external cremaster muscle

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3
Q

what are the 3 accessory sex glands?

A
  1. paired vesicular glands/seminal vesicles
  2. one prostate gland
  3. paired bulbourethral/cowper’s glands
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4
Q

why are the testes held outside the body cavity?

A

so that the sperm can be held at cooler-then-body temperature in order to not kill sperm

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5
Q

what is the function of the bulbourethral/cowpers glands? (2)

A
  1. contribute gel fraction of ejaculate
  2. causes seminal plasma to coagulate following ejaculation
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6
Q

what is the function of the testes? (2)

A
  1. production of spermatozoa
  2. production of androgens
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7
Q

what is the function of the scrotum? (3)

A
  1. support the testes
  2. temperature control of the testes
  3. protection of the testes
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8
Q

what is the function of the spermatic chord (2)?

A
  1. support the testes
  2. temperature control of testes
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9
Q

what is the function of the epididymis? (4)

A
  1. concentration of spermatozoa
  2. storage of spermatozoa
  3. maturation of spermatozoa
  4. transport of spermatozoa
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10
Q

what is the function of the vas deferens?

A

trnasport of spermatozoa

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11
Q

what is the function of the urethra?

A

transport of semen

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12
Q

what is the function of the vesicular glands/seminal vesicles?

A

contributes fluid, energy substrates, and buffers to semen

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13
Q

what is the function of the prostate gland?

A

contributes fluid and inorganic ions to semen

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14
Q

what is the function of the penis?

A

male organ of copulation

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15
Q

what is the scrotum?

A

an outpouching of the skin, divided into 2 sacs

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16
Q

what does each sac of the scrotum contain, located where?

A

a testis, located on either side of the penis

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17
Q

where should testes descend and when?

A

from the abdominal cavity through the inguinalcanal into the scrotum, during the last 3 weeks of gestation up to the first two weeks after birth

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18
Q

at what point should you get worried if your colt’s testes haven’t descended?

A

if you can’t palpate them at 18months, be worried; then act if can’t feel by 2 years old

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19
Q

what is the temperature of the testes? compare to body temp

A

testes: 30.5-32.5C or 86.9-90.5F
body: 38C or 100F

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20
Q

what is a cryptorchod testis?

A

one that stays in the abdomina cavity or inguinal canal

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21
Q

what are the 2 major functions of the male reproductive organs?

A
  1. produce testosterone to allow sperm production
  2. produce, store, and deliver mature viable sperm
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22
Q

where does sperm production begin?

A

with the seminiferous tubules of the testes

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23
Q

where does sperm production end?

A

with the urethral orifice of the penis

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24
Q

where are spermatozoa produced and begin to mature?

A

in the seminiferous tubules of the testes

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25
Q

after spermatozoa are formed where do they go? give general and then the next 4 places in the path after leaving seminiferous tubules

A

pass through remaining tubules of the testes
1. seminiferous tubules
2. straight tubules
3. rete tubules
4. efferent tubules/ductules
5. then reach the duct of the head of the epididymis

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26
Q

what is the epididymis made up of?

A

head (caput), body (corpus), tail (cauda)

27
Q

what happens in the epididymis?

A

final maturation of spermatozoa into motile, viable sperm

28
Q

where are mature sperm stored and until when?

A

mature sperm stored in the tail of the epididymis until ejaculation

29
Q

how long is spermatogenesis in the stallion from start to finish?

A

57-58 days

30
Q

what happens to sperm shortly before ejaculation?

A

they are carried to the pelvic urethra from the epidiymis by the ductus deferens

31
Q

what happens as sperm reach the pelvic urethra before ejaculation?

A

they are mixed with seminal fluid and secretions from the accessory sex glands

32
Q

what do the secretions of the accessory sex glands do? (3)

A
  1. provide required nutrition (energy and protein) for the sperm
  2. act as a buffer
  3. prepare the lumen of the pelvic urethra for favorable passage of the sperm (lubricant)
33
Q

what makes up the majority of the ejaculate volume?

A

the seminal plasma

34
Q

what is the proposed function of seminal plasma? what is the known drawback?

A

appears to be important to sperm function, but long-term exposure to seminal plasma components may be detrimental to sperm survival of some stallions

35
Q

in fresh or chilled programs, what happens to plasma?

A

it is diluted with extenders

36
Q

what is done to remove seminal plasma in frozen semen?

A

centrifugation; will get a sperm pellet once you remove the supernatant

37
Q

what kind of response do all mares have to frozen semen?

A

some level of inflammatory response

38
Q

list the 5 aspects of neuroendocrine control of stallions

A
  1. hypothalamus
  2. pituitary gland
  3. pineal gland
  4. testes
  5. vomeronasal organ
39
Q

what causes the hypothalamus to release GnRH in the stallion?

A

response to neural and hormonal inputs

40
Q

what is the vomeronasal organ? what is it also called? describe and give its location

A

also called the Jacobson’s organ; is an accessory olfactory organ that is a duct lying beneath the nasal mucosa

41
Q

what is the vomeronasal organ connected to?

A

connected to 2 small openings in the anterior roof of the mouth just behind the upper lip

42
Q

how do chemicals enter the vomeronasal duct? what happens next?

A

through the oral cavity by the nasopalaitne ducts, that lead to the vomeronasal organ, where sensory neurons in the vomeronasal organ evaluate the material aspirated

43
Q

describe the flehman response in stallions (3)

A
  1. direct air across the openings conveys olfactory information from pheromones to the hypothalamus
  2. this causes GnRH to act on the anterior pituitary, which regulates production and release of LH and FSH
  3. these gonadotropins act on cells of the testes, regulating spermatogenesis and steriodogenesis
44
Q

what is the source of the pheromones that cause stallions to exhibit the flehmen response?

A

estrogen is released in the urine when a mare in heat urinates as an estrus behavior

45
Q

are stallions the only animals that can exhibit the flehman response? if not, provide 4 others

A

no;
1. mares and foals
2. cats
3. dogs (esp bloodhounds)
4. cows

46
Q

what does FSH do in stallions?

A

regulates compounds produced by sertoli cells, which are nurse cells that are important in sperm production

47
Q

what does LH do in stallions?

A

regulates the Leydig cells of the testes, stimulating production of testosterone and estrogen

48
Q

what is testosterone mainly important for?

A

normal spermatogenesis

49
Q

give 3 functions other than normal spermatogenesis that testosterone is important for

A
  1. maintaining accessory sex organs
  2. development of secondary sex characteristics of stallion
  3. maintain libido
50
Q

give 2 examples of secondary sex characteristics in stallions

A
  1. they are more muscular
  2. thick neck (cresty neck)
51
Q

what does estrogen do in stallions?

A

may also function in maintenance of accessory sex gland function and libido via feedback on the hypothalamus and anterior pituitary gland to regulate LH release

52
Q

how can you tell a cryptorchid without ever palpating it?

A

cryptorchids have the highest estrogen levels of any make horse! this can help you tell if that “gelding” actually has a retained testicle

53
Q

is the photoperiod important to a stallion? compare to mare

A

yes, but the importance of the pineal gland and influence of season is less obvious in stallions than mares, since stallions produce sperm throughout the year

54
Q

describe when the max values of testicular size, semen production, libido, and hormone concentrations are observed in stallions

A

in spring and summer, or May-July, which is also the peak period of cyclicity for mares

55
Q

describe stallion repro activity in December-February (2)

A
  1. spermatozoal output is 50% of peak
  2. volume ejaculated is 50% of peak
56
Q

what does exposure of stallions to 16 hours of artificial light and 8 hours of dark do intially? then after a while?

A

results in early attainment of peak production, but prologned exposure to artificially long days does not maintain peak production, as these stallions will experience a photorefractory period and display earlier than normal regression of testicular size

57
Q

at least how old must a stallion be before he is producing viable sperm to be bred?

A

at least one year old

58
Q

when do some start sparingly breeding a stallion and why?

A

at 2 years old but only if has great genetics and conformation, as is not old enough to have proved himself as great in any other way yet

59
Q

what is the risk in breeding a young stallion live cover? (2)

A
  1. may be savaged by mares
  2. may start to savage mares himself
60
Q

when are most stallions put into full service?

A

at four years old

61
Q

how many mares can a 2 year old stallion breed per season?

A

6/7

62
Q

describe the breeding schedule of a three year old stallion

A

either 4-6 services/week or 12 mares/season

63
Q

describe the breeding schedule of a mature stallion

A

serviced daily for 7-8 days a week with one day off, or twice daily, 3-4 days in a row

Horse Systems and Management (18 decks)

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