15 - Spermatogenesis

Question 1

Goals of spermatogenesis (4)

Answer 1

• provide a male with continual supply of gametes
• provide billions of sperm each day to maximize reproductive efficiency
• provide genetic diversity (each sperm has unique DNA)
• provide an immunologically privileged site where spermatogenic cells will not be destroyed by males immune system

Question 2

Where does spermatogenesis occur? What happens after

Answer 2

Occurs in the seminiferous tubules in the parenchyma

Sperm then drains into the mediastinum then the epididymis head, then body then is stored in the tail until ejaculation

Question 3

Three phases of spermatogenesis

Answer 3

1. proliferation
2. meiosis
3. differentiation

Question 4

What is the proliferation stage of spermatogenesis

Answer 4

Mitotic division of spermatogonia to form primary spermatocytes
Constant replacement of spermatogonia

Question 5

What is the meiosis phase of spermatogenesis? How is genetic diversity guaranteed?

Answer 5

Diploid (2N) primary spermatocytes go through meiotic division to produce haploid (1N) spermatids
Genetic diversity is guaranteed by processes such as homologous recombination and DNA methylation

Question 6

What is differentiation phase of spermatogenesis

Answer 6

Spermogenesis
Spermatids develop into fully formed spermatozoa

Question 7

Slide 8**

Answer 7

phases of spermatogenesis

Question 8

Slide 9

Answer 8

Important diagram: been in like every slideset

Question 9

What is the blood-testis barrier

Answer 9

Cellular barrier that prevents immune system from affecting developing sperm (sperm can be recognized as foreign cells and be attacked by immune response)

Question 10

Blood-testis barrier has two cellular layers:

Answer 10

1. peritubular cells: surrounding the seminiferous tubules
2. junctional complexes: tight connections between the sertoli cells within the seminiferous tubules

Question 11

Junction complexes divide the seminiferous lumen into 2 distinct compartments

Answer 11

1. Basal compartment
2. Adluminal compartment

Question 12

Slides 11, 12

Answer 12

Blood testis barrer*

Question 13

Duration of spermatogenesis in the bull, stallion

Answer 13

Bull
- spermatogonia to spermatid = 13.5 days
- spermatid to spermatozoa = 61 days

Stallion
- spermatogonia to spermatid = 12.2 days
- spermatid to spermatozoa = 55 days

Slide 13***

Question 14

Spermatozoa consist of … (6)

Answer 14

• nucleus + genetic material
• little cytoplasm
• no endoplasmic reticulum
• numerous mitochondria
• a tail
• plasma membrane + acrosome

Question 15

Why do sperm have numerous mitochondria

Answer 15

Provides energy for motility to reach fertilization site and to penetrate

Question 16

Four phases of change spermatids go through during differentiation

Answer 16

1. Golgi phase = acrosomic vesicle formation and centriole migration
2. cap phase = acrosomic vesicle spreads over nucleus & initiation of axoneme (tail) formation
3. acrosomal phase = nuclear + cytoplasmic elongation & neck + annulus formation
4. maturation phase = final assembly of sperm

Question 17

Slide 15-25

Answer 17

Differentiation phases (so much info)

Question 18

In differentiation, the golgi becomes what? The centrioles become… The mitochondria? The cytoplasm? Manchette?

Answer 18

Golgi -> acrosome

Centrioles
- proximal -> sperm neck
- distal -> tail

Mitochondria -> mitochondrial sheath

Cytoplasm -> lost as cytoplasmic droplet

Manchette -> postnulear cap

Question 19

How is testicular weight related to sperm production?

Answer 19

Association with testicular growth weight and sperm produced
More weight in testes = more sperm per gram of testicular parenchyma = more daily sperm production

Question 20

What animal has high testes weight and daily sperm production

Answer 20

Boar
750 gram testes

Slide 26

Question 21

Three functions of the epididymus

Answer 21

1. sperm concentration: fluids that suspended the sperm in sem tub absorbed by epididymal head and uppder body
2. sperm maturation: as they move through epid body into upper tail they mature, become motile and gain potential to fertilize
3. storage: sperm stored in distal tail of the epidid until time of ejaculation (or reabsorbed into body)

Question 22

Slides 28, 29, 30, 31

Answer 22

Sperm stages
Epididymal transit time

Question 23

What animal has the longest epididymal transit time?

Answer 23

Bull = 14 days (10 days in tail)
Boar = 9-14 days

Question 24

Describe the golgi phase

Answer 24

1. small vesicles of the golgi fuse and start to produce proacrosomic granules
2. centrioles (proximal and distal) migrate around nucleus opposite of golgi
3. fusion of golgi vesicles continues, producing large acrosomic vesicle containing dense acrosomic granule
4. proximal centrioles position to become point of attachment btw sperm head and tail. Distal centrioles positioned to become axoneme (tail)

Question 25

Describe the cap phase

Answer 25

1. remainder of golgi migrates around nucleus towards centrioles
2. distal centriole starts forming the axoneme (tail)
3. acrosomal vesicle flattens and begins to form outer acrosomal membrane, inner acrosomal membrane and acrosomal contents

Question 26

Describe the acrosomal phase

Answer 26

1. nucleus elongates & acrosome stretches to cover most of developing sperm head
2. manchette microtubules and stretch plasma membrane down to give mitochondria access to developing tail
3. Sperm neck and annulus form

Question 27

Describe the maturation phase

Answer 27

1. mitochondria form spiral assembly around the tail to create well defined middle piece
2. manchette tubules regress and form the postnuclear cap
3. cytoplasm sloughs off and forms cytopalsmic droplet
4. annulus forms a defined junction between the middle and principle pieces