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Animal Production > Male Repro II > Flashcards

Male Repro II Flashcards

1
Q

Spermatocytogenesis

A

Proliferation of spermatogonia

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2
Q

Spermiogenesis

A

Differentiation from Primary spermatocytes to secondary to spermatids

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3
Q

Spermatogenesis

A

Include proliferation and differentiation.

From spermatogonia to the spermatids

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4
Q

Male germline stem cells

A

-connect generations together
-includes PGCs, gonocytes, spermatogonial stem cells (SSCs)

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5
Q

Spermatogonial stem cells (SSCs)

A

-can self renew and produce differentiated germ cells
-the only adult stem cells that can pass on genes to next generation

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6
Q

Two models in which formation of SSCs may occur

A
  1. All gonocytes are the same but some random ones transition to SSCs, which can renew and give rise to progenitors. Other ones give rise to spermatogonia
  2. Different types of gonocytes are responsible for forming SSC pool, initial progenitor population, and initial differentiating spermatogonial population
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7
Q

Symmetrical self renewal of SSC

A

-occurs during neonatal development and for regeneration

SSC produces 2 SSCs

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8
Q

Symmetrical differentiation

A

Occurs in balance with symmetrical self-renewal during steady-state spermatogenesis

SSC becomes committed progenitor spermatogonia

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9
Q

Asymmetric division

A

SSC produces one new SSC and one transient amplifying progenitor

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10
Q

Classification of spermatogonia

A
  1. undifferentiated
  2. Differentiating
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11
Q

Stages of spermatogenesis

A
  1. Spermatogonia type A single (As) divides
  2. 2 new As spermatogonia OR a connected pair (Apair) which divide
  3. Aaligned (Aal)- which are chains of 4,8, 16 cells
    4.Activated by retinoic acid (no cell division) leading to differentiation
    5.Five synchronized cell divisions leading to A2, A3, A4, Intermediate (In), and B-spermatogonia
  4. B-spermatogonia physically pass through blood-testis barrier to adluminal compartment
  5. Divide into 2 primary spermatocytes, then begin phase 1 of meiosis where they undergo 5 stages and produce
  6. two secondary spermatocytes (haploid) which then immediately begin 2nd meiotic division
  7. Each secondary spermatocyte will produce 2 haploid round spermatids
  8. Testosterone will drive round spermatids to differentiate (spermiogenesis) into elongated spermatids
    11.Spermiation
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12
Q

Undifferentiated spermatogonia

A

As, Apr, Aal

As are rare, relatively quiescent, true SSCs

Apr, Aal have some SSC potential but are on wy to differentiation and called transit amplifying progenitor cells

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13
Q

Differentiating spermatogonia

A

Includes A1 to A4, Intermediate, and B-spermatogonia

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14
Q

What happens in 1st phase of meiosis of the 2 primary spermatocytes?

A

During the long prophase of 1st meiosis, DNA undergoes complete replication to form tetrads, followed by crossing over of homologous chromosomes to ensure genetic heterogeneity of gametes

After completion of 5 stages, leads to two secondary spermatocytes which then undergo 2nd meiotic division

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15
Q

Primary spermatocytes 5 stages that they go through during 1st meiosis

A

-preleptotene
-leptotene
-zygotene
-pachytene
-diplotene

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16
Q

Round spermatids

A

Produced by secondary spermatocytes. Testosterone drives them to become elongated

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17
Q

Spermiation

A

Retinoic acid causes the spermatozoa to be released into the lumen of seminiferous tubules

18
Q

What does a elongated spermatid have that a round spermatid does not?

A

-Acrosome
-condensation of nuclear material
-outgrowth of a motile tail
-loss of excess cytoplasm, organelles, water

19
Q

4 phases of spermiogenesis

A
  1. golgi phase
  2. Cap phase
  3. Acrosomal phase
  4. Maturation phase
20
Q

Golgi phase

A

1.newly formed spermatid is spherical with well developed golgi
2. Small golgi vesicles fuse to form proacrosomic secretory granules and centrioles start migrating to opposite site
3. Contains acrosomic vesicle, proximal centriole (will give rise to the tail attachment site), distal centriole (will give rise to axoneme)

21
Q

Cap phase

A
  1. Golgi migrates to caudal pole
    2.distal centriole forms axoneme or flagellum
  2. Acrosomic vesicle flattens and starts forming cap. Cap has outer acrosomal membrane and inner acrosomal membrane and enzymes
22
Q

Purpose of cap

A

contains enzymes that can be used to drill into the oocyte

23
Q

Acrosomal phase

A
  1. nucleus begins to elongate and acrosome covers most of its anterior. Manchette forms from caudal half and extends down
  2. Neck and annulus are formed. All components are within the cytoplasm, including mitochondria
24
Q

Maturation phase

A
  1. Mitochondria form a spiral assembly around flagellum that defines middle piece
  2. Postnuclear cap is formed from manchette microtubules
  3. Annulus forms the junction between middle piece and principal piece
25
Q

Sperm length in different species

A

Humans: 50 micrometers
Boar and stallion: 60
Ruminants: 75
Rodents: 150-250

26
Q

Staining of sperm cap for evaluating quality

A

Post-nuclear cap has fibrous sulphur rich proteins. They stain intensely with eosin-bromophenol blue in dead sperm making them easy to evaluate

27
Q

Spermatid head

A

-usually spatula shaped
-nucleus oval, flat, covered with nuclear membrane
-chromatin is compact and inactive due to high keratinoid proteins

28
Q

Acrosome

A

-covers anterior 2/3rds of nucleus
-a membrane covered lysosome containing hydrolytic enzymes

29
Q

Acrosome rxn

A

during fertilization acrosome undergoes a special exocytosis

30
Q

Post-acrosomal sheath

A

Region contains receptors for recognition of homologous oocyte

31
Q

Spermatid tail

A

composed of capitulum, middle piece, principle piece, terminal piece

32
Q

Capitulum

A

fits into the implantation socket of head

33
Q

Middle piece of tail

A

-has laminated columns, gives side to side flexibility
-9 coarse outer fibres
-axoneme composed of 9 pairs of microtubules (doublets) around 2 central filaments
-all covered by helical mitochondrial sheath

34
Q

Principal piece of tail

A

-forms majority of tail and continues to almost end of flagellum

35
Q

Terminal piece of tail

A

where only microtubules remain

36
Q

Sperm production timing

A

-continuous in non-seasonal males
-before one spermatogenic series finishes, 4 or more initiate
-all descendants of B-spermatogonia develop synchronously
-predictable intervals define transitions

37
Q

Seminiferous tubules showing stages of cycle

A

-cross sections show different stages of cycle=spermatogenic wave. Each stage follows or precedes adjacent stages.

38
Q

How long is spermatogenic wave in bull?

A

10mm long

39
Q

LH and testosterone release

A

Each LH release drives a pulse of testosterone release by Leydig cells

Both remain high in serum for 0.5-1 hour

40
Q

Hormonal regulation of spermatogenesis

A

-FSH acts on sertoli cells= facilitates spermatogenesis. Also increased spermatogonia proliferation INDIRECTLY!

-LH acts on Leydig cells= stimulates testosterone production

-Testosterone and inhibin act in a negative feedback loop= temporarily inhibit further release of GnRH, FSH, LH

-Testosterone= needed for transition of spermatocytes to spermatids (OCCURS INDIRECTLY, mediated through somatic cells)

-Estradiol converted from testosterone by aromatase in sertoli cells= spermatogenesis

41
Q

Why is testosterone higher in testis?

A

100-500x higher in testis than in circulation

occurs because of pampiniform plexus

42
Q

Where are androgen receptors present?

A

-sertoli cells, peritubular myoid cells, leydig cells

**not present in germ cells

Animal Production (17 decks)

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