Spermatogenesis

Question 1

Spermatogenesis

Answer 1

Production of spermatozoa by the testis

-spermatogonia – spermatocyte – spermatid – spermatozoa

Question 2

What all is included in spermatogenesis?

Answer 2

Consists of all cell divisions and morphological changes of developing germ cells occurring in epithelium of seminiferous tubules

Question 3

What are the 3 phases of growth?

Answer 3

Proliferation, meiosis and differentiation occur in tubular compartment of seminiferous tubules

Question 4

What is the proliferation stage?

Answer 4

Mitotic divisions of spermatogonia (A to B) and stem cell renewal (infinite supply of spermatogonia)

-occurs in basal compartment of seminiferous tubules, between basal lamina and sertoli junctions

Question 5

What is the meiotic stage?

Answer 5

B-spermatogonia differentiate into 1 degree spermatocyte and undergo meiosis

-meiosis 1: DNA replication and crossing over
- meiosis 2: 2 degree spermatocyte divides into haploid spermatids
-meiotic stage occurs in adluminal compartment, closer to compartment than lumen

Question 6

What is differentiation?

Answer 6

No cell divisions, spherical spermatid differentiates into a specialized spermatogonia

-occurs in adluminal compartment, close to lumen

Question 7

Differentiation of Sperm

Answer 7

First set of steps in conferring sperms ability to swim, deliver genetic material, and activate the oocyte for zygote development

Question 8

Spherical Spermatids

Answer 8

Undergo a series of modifications: becoming motile, condensing their nuclei (for protection), and forming acrosomes for fertilization

Question 9

Golgi Phase

Answer 9

Small vesicles of golgi fuse, form proacrosomic granules on one side of nucleus

Question 10

Cap Phase

Answer 10

Acrosomic vesicle forms a cap over one side of nucleus (anterior position) while golgi and other cytoplasmic organelles migrate towards distal portion

Question 11

Acrosomal Phase

Answer 11

Nucleus begins to elongate and microtubules organize and form manchette

Question 12

Maturation Phase

Answer 12

Manchette forms post-nuclear cap and mitochondria migrate to posterior side of nucleus to form a spiral assembly (defining feature)

Question 13

Main Components of Sperm Head

Answer 13

Nucleus, acrosome and post nuclear cap

Question 14

Nucleus in head of Sperm

Answer 14

Oval, flattened, with condensed DNA (di-sulfide cross-linking)

-degree of cross-linking determines level of maturation of sperm
-DNA remains inert until fertilization

Question 15

Acrosome in Head of Sperm

Answer 15

Membrane vesicle with hydrolytic enzymes covering anterior 2/3 of nucleus

-acrosome resides within apical ridge of head

Question 16

Postnuclear Cap of Sperm Head

Answer 16

Membrane component posterior to acrosome

Question 17

Components of Sperm Tail

Answer 17

Capitulum, Middle piece, principal piece, and terminal piece

Question 18

Capitulum of sperm tail

Answer 18

Neck of sperm, attaches flagellum to head

Question 19

Middle piece of sperm tail

Answer 19

Mitochondrial sheath, provides swimming power to spermatozoon

-mitochondria arranged in helical structure around middle flagellum

Question 20

Principal piece of sperm tail

Answer 20

Main part of flagellum, necessary for movement

Question 21

Terminal piece of sperm tail

Answer 21

End of microtubule

Question 22

Spermiation

Answer 22

Release of fully differentiated spermatozoa into lumen of seminiferous tubules

Question 23

How does spermatozoa formation occur?

Answer 23

In spermatogenic cycles/waves whose length is species dependent

Question 24

Is a segment of seminiferous tubules always undergoing spermiation?

Answer 24

Yes, it is a continuous and uniform process under constant/uniform endocrine control

Question 25

In bulls, what stage of the spermatic wave is undergoing spermiation?

Answer 25

The 8th (final stage) undergoes spermiation before returning to the 1st stage

Question 26

How many cycles does it take for all sections of the seminiferous tubules to go from stages 1-8?

Answer 26

4.5 cycles for all subsections to complete all stages

Question 27

How many days does it take for a full wave to be complete?

Answer 27

61 days (13.5 days for spermiation x 4.5 cycles)

Question 28

Apoptosis of germ cells

Answer 28

Common event in spermatogenesis of all species, rate is dependent on environmental factors

Question 29

What are the environmental factors in apoptosis of germ cells?

Answer 29

Heat stress, poor welfare, physical/psychological trauma, disease, hormone levels, nutrition and season