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Physiology > Spermatogenesis and Oogenesis > Flashcards

Spermatogenesis and Oogenesis Flashcards

1
Q

Spermatogenesis

A

Process of formation of sperm

  • begins at puberty
  • rarely totally ceases
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2
Q

Where is the site of sperm formation?

A

Seminiferous tubule of the testicle

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3
Q

Events of spermatogenesis

A

Start with 2n chromosome (spermatogonium) –> mitotic division = primary spermatocyte (2n) –> at end of meiosis 1 = secondary spermatocyte (2 1n chromosomes) –> meiosis 2 = early spermatids (4 n chromosomes) –> differentiation, seroli cells provide nutrients –> sperm cells (spermatozoa)

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4
Q

Spermatogenesis progress from the cortex of the semineferous tubule and ends in the _____

A

Lumen

- where fully formed sperm cells are released

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5
Q

Each spermatogonia produces _____

A

4 sperm cells

- 1:4 ratio

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6
Q

Events of oogonium

A

Begin with primary oocyte (2n) –> meiosis 1 = secondary oocyte and first polar body –> secondary ooctye undergoes meiosis 2 = ootid and second polar body –> ootid differentiates into 1 ovum

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7
Q

Females only produce _____ from an oogonium

A

1 ovum

- do not undergo mitosis!!!

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8
Q

Seasonality’s effect on spermatogenesis

A

Produce sperm throughout the year, but may produce more during the species’ season of breeding
- high vs low production

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9
Q

Meiosis 1

A

2 haploid cells form

  • chromosomes are still double
  • telophase and cytokinesis with cleavage furrow
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10
Q

Meiosis 2

A

Sister chromatids separated

  • 4 haploid daughter cells result
  • contains single chromosomes
  • prophase 2 - telophase 2
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11
Q

Epididymis

A

Storage of produced sperm

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12
Q

Blood flow of the testicle

A

Enters testicular artery

  • artery and venous return are intertwined = pampiniform plexus
  • acts to cool the blood entering the testis
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13
Q

Testosterone secreted by Leydig cells has a _______ feedback

A

Negative

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14
Q

LH stimulates Leydig cells to secrete ______

A

Testosterone

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15
Q

FSH stimulates Sertoli cells to produce _____

A

Inhibin

  • also converts testosterone to estrogen
  • helps with spermiogenesis
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16
Q

Males: LH released from AP in a ______ fashion

A

Pulsatile

  • only have a tonic center, no surge
  • prevents refractoriness to sustained LH
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17
Q

Testosterone secretion is ______ and ______

A

Short; pulsatile

- elevated testosterone in testis is essential for spermatogenesis

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18
Q

Pampiniform plexus helps maintain high levels of ______ in the testis

A

Testosterone

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19
Q

Large spikes of _____ has a negative feedback and ______ LH production

A

Testosterone; downregulates

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20
Q

Is peripheral blood a good indicator of the testicular environment?

A

No, 500x dilution of testosterone, estrogen, and DHT by systemic circulation

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21
Q

What are the 3 biological events involved in spermatogenesis?

A
  • mitosis
  • meiosis
  • spermiogenesis
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22
Q

Mitosis

A

Proliferation phase which allows for continual supply of germ cells

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23
Q

Meiosis

A
  • allows for diploid to haploid
  • allows for crossing over
  • assures genetic diversity
24
Q

Spermiogenesis

A

Dramatic morphological changes from spermatids to spermatozoa

25
Q

The proliferation phase of spermatogenesis occurs in the ______ area of the seminiferous tubules

A

Basal

26
Q

Meiosis and differentiation of spermatogenesis occurs in the ______ area of the seminiferous tubules

A

Adluminal

27
Q

______ envelop the developing spermatogonia

A

Seroli cells

28
Q

What process of spermatogenesis is very heat sensitive?

A

Maturation of spermatogonia into primary spermatocytes

- mitosis

29
Q

Primary spermatocytes undergo _____ and form ______

A

Meiosis 1; secondary spermatocytes

- haploid!

30
Q

Secondary spermatocytes undergo ____ and become ______

A

Meiosis 2; spermatids

31
Q

What is one cycle of the seminiferous tubule?

A

Progression through all stages at one location along a seminiferous tubule
- cycle length is unique to each species

32
Q

What are the approx days to complete spermatogenesis for the bull and stallion?

A
  • bull: 61 days

- stallion: 55 days

33
Q

Stages of cycle

A

Arbirtarily defined cellular associations that transition one to the next at predictable intervals

34
Q

Breakdown of spermatogenesis in the bull

A

8 stages in the bull

  • takes 13.5 days to transition thu all 8 stages (or 1 cycle)
  • complete spermatogenesis takes 4.5 cycles
  • 4.5 cycles x 13.5 days = 61 days
35
Q

Spermatogenesis must occur _____ cooler than body temperature

A

3-7 degrees C

36
Q

What structures are involved in temperature control of the testicles?

A
  • scrotal sweating
  • tunica dartos muscle
  • cremaster muscle
  • pampiniform plexus
37
Q

Blood testis barrier

A

Sertoli cells are joined by tight junctions which effectively create a barrier from the immune system

  • allows metabolism of developing sperm to occur in a controlled environment
  • developing sperm are not allowed access to the interstitial space where the immune system will recognize them as foreign
38
Q

Sex determination

A

One pair of chromosomes determines sex of the animal

39
Q

Females can only contribute an ____

A

X

40
Q

Males contribute an ____ or a _____

A

X; Y

41
Q

Sex of the offspring is determined by whether an __________ fertilizes the oocyte

A

X or Y bearing sperm

42
Q

Chromosomal sex

A

Determined at fertilization

43
Q

Gonadal sex

A

Determined by presence of XY chromosome

44
Q

Phenotypic sex

A

Determined by secretion of testosterone to suppress estrogen

45
Q

Head

A

Contains the DNA

- acrosome cap contains enzymes which aid in fertilization

46
Q

Midpiece

A

Contains mitochondria which produce power for the tail action

47
Q

Tail

A

Flagellum like action provides movement

- 1-4 mm/minute in fluid environment

48
Q

Semen

A

Name given for the sperm and associated fluids which are ejaculated
- all spermatozoa plus fluid from accessory sex glands

49
Q

Accessory sex glands

A
  • ampulla
  • prostate
  • seminal vesicles
  • bulbourethral glands
50
Q

Oogenesis

A

Development of the oocyte

51
Q

When do oogonia undergo mitosis?

A

During prenatal growth

52
Q

Oogonia enter meiosis near the time of _______

A

Birth

  • remain in resting prophase until puberty
  • meiosis then resumes in a few cells each cycle
53
Q

Following oogenesis, ____ ovum and _____ polar bodies are produced

A

1; 3

54
Q

A secondary oocyte is capable of fertilization ________

A

Immediately

- exception: dogs ovulate a primary ooctye that is not capable of fertilization for 2 days

55
Q

Differences in germ cell production

A
  • males constantly replenish germ cells thru ongoing mitosis
  • females are born with all they will ever have and slowly deplete their supply
  • great increase in number of sperm by mitosis in the male
  • oogenesis involves limited number of oogonia each cycle

Physiology (33 decks)

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