describing spermatogenesis in cellular level

1. SPERMATOGENESIS
CYCLE OF
SEMINIFEROUS
EPITHELIUM
SPERMATOGENIC WAVE
submitted by,
fathima suhra.Y.P
22-MVP-45
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2. SPERMATOGENESIS
Spermatogenesis = proliferation + meiosis + differentiation

3. goals of spermatogenesis :
● continual supply of male gametes through stem cell renewal
● genetic diversity
● billions of sperm to maximize reproduction
● immunologically privileged site to developing germ cells
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4. 4

5. 1) Proliferation phase:
All mitotic divisions of spermatogonia
Generations of spermatogonia
B- spermatogonia
Primary spermatocyte
Mitotic divisions
Last mitotic division
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6. ● Stem cell renewal
● Immature germ cells ( diploid ) located at periphery
● Mature, move towards the lumen
● Intercellular bridges- communication synchronized
development
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7. 2) Meiotic phase :
● 2 divisions
● Primary & secondary spermatocytes
● Genetic diversity
● Diploid haploid
● Interphase
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8. Primary spermatocyte
preleptotene
leptotene
zygotene
pachytene
diplotene
1st meiotic
prophase
Secondary spermatocyte
Spermatid (1N)
2nd meiosis
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9. ● Preleptotene phase: DNA replication - tetrads - chiasmata
● Crossing over genetic heterogeneity
● Prophase is long process
● Life span of 1° spermatocyte > other germ cells
● Life span of 2° spermatocyte is 1.1 - 1.7 days
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10. 3) Differentiation phase :
Maturation phase
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final assembly that forms a
spermatozoon
Acrosomal phase
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Nuclear and cytoplasmic
elongation
Cap phase
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Acrosomic vesicle
spreading over the nucleus
Acromic vesicle formation
Golgi phase
01
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11. 1)Golgi phase :
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12. 2) Cap phase
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13. 3) Acrosomal phase
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14. 4) Maturation phase
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15. Spermatozoa = head + tail
Head = nucleus + acrosome + postnuclear cap
Tail = middle piece + principal piece + terminal piece
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16. Spermiation :
➢ Sertoli to lumen
➢ Analogous to ovulation
➢ occurs continuously throughout the testis
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17. Structure of spermatozoa
Head
● characteristic shape
● oval, flattened and surrounded by a nuclear membrane
● highly keratinized compacted chromatin - inert
● Keratinoid proteins have a high degree of disulfide cross linking -
insoluble
● nuclear histones are replaced by protamines - DNA condensation
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18. ● At this point in spermiogenesis, transcription and translation stops
● DNA remains inert until the time of fertilization
● prevent damage between spermiation and fertilization
● At fertilization, process is reversed
● disulfide cross-links are reduced by glutathione
● protamines are replaced with histones - nuclear decondensation -
male pronucleus
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19. Acrosome
● anterior 2/3 of the nucleus
● Membrane bound lysosome
● acrosin, hyaluronidase, zona lysin, esterases and acid hydrolases
● acrosome reaction
● membrane component posterior to the acrosome is the postnuclear cap
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20. Tail
• Self-powered flagellum
•
• Capitulum fits to implantation socket
• axoneme from distal centriole , composed of 9 pairs of microtubules ,
arranged radially around 2 central filaments
• mitochondrial sheath - helical pattern
• annulus - juncture between the middle piece and the principal piece
• majority of the tail - principal piece
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22. • male produces gametes continually and uniformly throughout reproductive
lifespan
• exception , seasonal breeder
• germinal epithelium "turn-on" and "turn-off' as a function of environmental
influences
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23. Cycle of seminiferous epithelium
• cellular generations
• stages of the cycle
• duration of one cycle - species unique
• how the cycle is repeated
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24. • same type Germ cell generations located at one site within the seminiferous
epithelium
• cross-section of a seminiferous tubule, 4 or 5 concentric "layers" of germ
cells
• Cells in each layer comprise a generation
• Cross-sections along the length of a seminiferous tubule will have
different appearance but the entire cross-section at a given location will
usually appear similar
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25. 25

26. 26

27. Stage = specific cellular associations
Stage duration = time required for completion of one stage (cell
association)
Cycle = progression through sequence of all stages
Cycle duration = time required to complete one cycle
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28. Stage Bull Ram Boar Stallion Rabbit
I 4.2 2.2 1.1 2.0 3.1
II 1.2 1.1 1.4 1.8 1.5
Ill 2.7 1.9 0.4 0.4 0.8
IV 1.7 1.1 1.2 1.9 1.2
V 0.2 0.4 0.8 0.9 0.5
VI 0.8 1.3 1.6 1.7 1.7
VII 1.1 1.1 1.0 1.6 1.3
VIII 1.6 0.8 1.0 1.9 0.9
1 cycle duration 13.5 10.1 8.3 12.2 11.0
duration of
spermatogenesis
61 47 39 55 48
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29. 29

30. spermatogenic wave
•
• refers to the differences at any given instant in time along the
length of the seminiferous tubule
• distance between these spermiation sites is relatively constant
• site of spermiation along the tubule is constantly changing, creating a
"wave" of sperm release down the length of the tubule
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