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Reproduction - Gateway > Male reproduction and spermatogenesis > Flashcards

Male reproduction and spermatogenesis Flashcards

1
Q

What is the order of the male reproductive tract starting at the vas deferens?

A

Vas deferens - seminal vesicles - prostate - retractor penis muscle - sigmoid flexure - retractor penis muscle - glans penis
_ sigmoid flexure - testicles - testicular epididymis

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2
Q

What are the three secretory glands where sperm are ejaculated?

A

2x seminal vesicles

1x ampulla - thickening of vas deferens

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3
Q

What is the role of the retractor penis muscle?

A

Hold the penis in a s shape, by double retractor penis, while contracted the penis is held in the sigmoid flexure, when erect, relaxation of retractor penis muscle, allowing penis to straighten.

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4
Q

What are the 2 functions of the testis?

A
  • production and transmission of male genes (spermatozoa)

- production of reproductive hormones (androgens)

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5
Q

What are the 2 compartments of the testis?

A
  • within seminiferous tubules, sertoli cells present, sperm develops
  • between seminiferous tubules, leydig cells present, androgens synthesised
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6
Q

What is spermatogenesis?

A

formation of spermatozoa

- consists of 3 phases

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7
Q

What is the 1st phase of spermatogenesis?

A

Mitotic proliferation - multiple rounds
- produces large numbers of cells (spermatogenesis)
diploid + genetically identical

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8
Q

What is the 2nd phase of spermatogenesis?

A

Mitotic division 2 rounds
- generates genetic diversity (chromatids exchange genetic material)
- halves chromosome number (haploid)
1st round ——————— 2nd round
spermatocytes spermatids

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9
Q

What is the 3rd phase of spermatogenesis?

A

Cytodifferentiation

  • packages genes for delivery to oocyte
  • elongating spermatids - spermatozoa
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10
Q

What is in the interstitial compartment?

A

Leydig cell

Basement membrane

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11
Q

What is in the basal compartment?

A

Spermatogonia
1/2 of a sertoli cell
1st stage of spermatogenesis

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12
Q

What is in the adluminal compartment?

A 
1/2 sertoli cell 
Spermatocyte 
Spermatid 
Spermatozoa 
2nd + 3rd stage of spermatogenesis
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13
Q

What are sertoli cells?

A

Attached to the basement membrane of the seminiferous tubules

  • is in very close association with developing sperm at every stage of development
  • joined to adjacent sertoli cells via gap junction
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14
Q

How do sertoli cells control spermatogenesis?

A
  • transfer developmental proteins - spermatocytes
  • remove material from elongating spermartids
  • mediate androgen hormone (testosterone) action
    because they are all linked via gap junctions = coordinated spermatogenesis
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15
Q

What are androgens?

A

Principle testicular androgen is testosterone
Synthesised by leydig cells
Testosterone passes from leydig cells into:
- blood (feedback on anterior pituitary and hypothalamus)
- seminiferous tubules

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16
Q

What is the sertoli cells role in production of dihydrotestosterone?

A

Convert cholesterol into dihydrotestosterone

- dihydrotestosterone then passes into testicular fluid to stimulate male reproductive tract and spermatogenesis

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17
Q

How is dihydrotestosterone produced?

A

Leydig cells:
1.Cholesterol in the blood is converted into pregnenolone
2. Pregnenolone is then converted into oestradiol (goes to blood) and testosterone (some goes to blood and some goes to the sertoli cells)
Sertoli cells:
3. Testosterone is converted into oestradiol (goes into the blood) and dihydrotestosterone

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18
Q

What is the Hypothalamic - pituitary axis?

A

Gonadotrophin Releasing Hormones (GnRH) synthesised in hypothalamus
GnRH transported to anterior pituitary via blood hypophysal port vessels
Anterior pituitary secretes: Lutenising hormone (LH) + follicle stimulating hormone (FSH)

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19
Q

Is the hypothalamic-pituitary axis negative or positive feedback?

A

Negative feedback

20
Q

What happens if the pituitary gland is removed?

A
  • testes shrink
  • no spermatogenesis
  • leydig cells deteriorate
  • testosterone output falls
21
Q

Pituitary derived __ stimulates ___ to produce ____ and supports ____

A

LH
Leydig cells
Testosterone
Spermatogenesis

22
Q

What is FSHs role in spermatogenesis?

A
  • Stimulate the production of androgen receptor proteins in sertoli cells
  • allows sertoli cells to respond to androgens
23
Q

What is castration?

A
  • removal of testis
    • stops sperm + testosterone production
    • controls behaviour
24
Q

How is a castration performed in a lamb?

A

Rubber ring applied to scrotum above testis, constricting blood supply, testis drop off

25
Q

How is a castration performed in a dog?

A

Anaesthetise, skin incisions, remove connective tissue, expose sctrotal contents

26
Q

What is the spermatic cord made up of?

A

Artery, veins, Vas deferens, nerves, cremaster muscle

- passes from scrotum into abdominal cavity via the inguinal ring

27
Q

What makes up the blood supply to the testis?

A

-Testicular artery- aorta (below renal artery)
Right testicular vein (inferior vena cava)
Left testicular vein (left renal vein)

28
Q

How is the blood supply arranged in the testis?

A

Pampiniform plexus - counter current temperature regulation

29
Q

What is a vastectomy?

A

Human contraceptive

Vasectomised rams can bring ewes into season

30
Q

How is a vasectomy performed?

A

Cutting Vas deferens, stops transmission of sperm, maintains testosterone production
Bi-lateral scrotal incisions
Vas deferens identified and a section is cut out
Vas Deferens ligated
- few side effects

31
Q

How are sperm transported to the epididymis?

A

Sperm released from associate sertoli cells into seminiferous tubules - in fluid secreted by sertoli cells
Sperm travel into the rete testis, vasa efferentia and the epididymis but are not motile until they reach the epididymis

32
Q

How is the epididymis structured?

A 
Caput 
- fluid from sertoli cells released 
- sperm concentrated 100 fold 
- sperm subsequently transported by muscles in the epididymis 
Corpus
- modification of environment and sperm modification 
Cauda
- sperm storage
33
Q

How long does passage through the epididymis take?

A

10 days

34
Q

What happens in epididymal maturation?

A

Sperm structure
- loss of surplus cytoplasm (cytoplasmic droplet)
- condensation of nuclear chromatin by disulphide bridges
Sperm membranes
- add surface glycoproteins to plasma membranes
- membrane fluidity and lipid composition change - cholesterol selectively metabolised shifting balance toward unsaturated fatty acid
Metabolism
- depression of metabolic activity to prolong life of cells
- increased dependance on external fructose for energy production
Motility
- cAMP content of tail increases allowing acquisition of motility

35
Q

In the bull, where is seminal plasma formed?

A

Accessory glands

  • prostate gland
  • seminal vesicle
  • ampulla
  • bulbourethral
36
Q

What is seminal plasma composed of?

A

Glycoprotein decapacitation factors
Fructose + sorbitol - energy substrate
Citric acid - stops coagulation seminal stops
Acid phosphotase - phospholipid metabolism
Buffers - neutralise acid pH of vaginal fluids
Ascorbic acid - reducing agent to protect against sperm oxidation at ejaculation
Prostaglandins - stimulate muscle contractions in female tract

37
Q

What are the two types of penis structure?

A
  1. Fibroelastic
    - Ram, bull, boar
    - erectile tissue - corpus cavernosum + corpus spongiosum
    - sigmoid flexure
  2. Musculovascular
    - Stallion, human
    - large corpus cavernosum fills with blood during erection
    - no sigmoid flexure
    - retractor penis muscle
38
Q

What is the glans penis?

A

Highly specialised
Tom cat androgen dependant spines - induce ovulation
Boar corkscrew
ram urethral process

39
Q

What is the echidna penis?

A

Monotreme

  • most primitive living mammals
  • at erection one side of the retracts with enlargement of alternative side
  • ejaculations alternate between sides, maintains sperm concentration if interval between mating is brief
40
Q

What is an argonaut penis?

A

Species of octopus
Male places sperm in a tentacle called a hectocotylus, tentacle detaches and swims towards the female
Females can be fertilised by hectocotylus from multiple males

41
Q

What are pshycogenic stimuli of erection?

A

Visual cues - mating in others, lordosis

Olfactory cues - sniffing of vulva, female urination, pheromones, androgens (boar and male)

42
Q

What is erection?

A

stimulation of pelvic nerve - arterial dilation and increased blood flow
Relaxation of retractor penis muscle - straightens sigmoid flexure
Muscles of vas deferens, seminal vesicles and prostate contract

43
Q

What is ejaculation?

A

Spermatozoa and seminal plasma expelled

44
Q

What is the 1st stage of coitus in the dog?

A

1-2 min

  • male mounts female
  • 1st + 2nd fractions of sperm ejaculated
45
Q

What is the 2nd stage of coitus in the dog (the turn)?

A

Dog turns by lifting one leg over the bitch

46
Q

What is the 3rd stage of coitus in the dog?

A

5-45 mins
3rd fraction of semen ejaculated (30ml)
Inter-uterine deposition deposition
- maintains high vaginal pressure

47
Q

How is erection performed in the dog?

A

Os penis
Bulbus Glandis forms copulatory lock
Venous outflow restricted - muscles in female contract

Reproduction - Gateway (6 decks)

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