Spermatogenesis

Question 1

What effect does LH have on gonads. State the cells they act on, what the downstream affects are including enzymes.

What is function of stAR protein?

Answer 1

Stimulates cAMP production , increase Ca+ and therefore promote transport /conversation of cholesterol to/in mitocondria to conversion to pregnenolone. via demolase.

StAR protein inhanced synthesis

Question 2

What is FSH’s role in spermatogenesis

Answer 2

FSH binds to GPCR receptors of sertoli cells and initiate the proliferation. They are also responsible for increased aromatase.

Without FSH @postnatal- no onset of sperm production.

without FSH in adulthood= no affects

Question 3

What stimulates inhibit production. Name what it is, what it acts on, what is downstream affect

Answer 3

Inhibin is released from FSH stimulated sertoli cells. Inhibit acts at level of Anterior pituitary to inhibit FSH release. (negative feedback)

Question 4

What is the feedback control for LH & FSH

Answer 4

LH release regulated by negative feedback of Testosterone from leydig cells.

FSH is regulated from inhibit released from sertoli cells and acting at levels of anterior pituitary

Question 5

What are expected results of ____hormone levels after a castration 1) control 2) castration 2)castration+T

Answer 5

FSH levels are not inhibited due to no inhibit release from sertoli cells.

1) LH level rise as normal
2) erratic variation and high concentration LH
3) No LH increased release

Question 6

Where is Testosterone released from, how is it stimulated, what affect does it have at brain levels. Where are its R at brain levels.

Answer 6

LH–> leydig cells–> testosterone release. This acts at the level of AP and hypothalamus. suppresses responsiveness to GnRH by down regulation of receptors and suppresses releases of GnRH @hypo

Question 7

Where does Inhibit have its affects., Where is inhibit released from (what type of cells). What what stimulates those cells

Answer 7

AP–>FSH –> sertoli cells –> inhibin release –>negative–>AP.

1. inhibin release of FSH at AP @gonadotrops
2. inhibin synthesis for FSH B-Subunit

Question 8

What androgens act on sertoli cells and where are those androgens released from

Answer 8

Testosterone and androgens from adrenal medulla act on serology cells. deficiency in testosterone or androgens results in infertility

Question 9

Other than releasing inhibit, what other affect does FSH binding to sertoli cells illicit. and what downstream affect does that have

Answer 9

FSH binding to serology cells stimulate production of androgen-binding protein (ABP). this sequesters testosterone ensuring large amount are continuously available to support spermatogenesis

Question 10

How do the sertoli cells sustain spermatogenesis . what are they stimulated by and what do they release to bind to the androgen that is required for spermatogenesis

Answer 10

Sertoli cells are stimulated by FSH. They release androgen binding protein (ABP) which captures testosterone before it is released into circulation and uses it for sperm maturation instead.

Question 11

Define the stages of spermatogenesis

Answer 11

Spermatocytogenesis- mitotic proliferation during which spermatogonia form primary spermatocytes

Meiosis- primary spermatocytes undergo reduction division to form round spermatids w. haploid nuclei

Cytodifferentiation (spermigenesis) - spermatids undergo metamorphosis forming spermatozoa (packaged sperm for delivery to oocyte)

Question 12

Give the stages of spermatogonium division. what happens to get it to next stage? what is name of next stage of spermatogenesis

Answer 12

1. Type A1
2. Type A2, A3, A4
3. Intermediate Spermatogonium
4. Spermatogonium type B
5. Resting primary spermatocyte

When primary spermatocyte puts pressure on tight junction, it leads into meiotic division (stage2)

Question 13

What allows regeneration of spermatogonia

Answer 13

The reversion of SECOND A2 back to an A1 cell allows for stem cell regeneration as other A2 cels is further differentiated. There is variation of this regeneration between species which dictates efficiency

Question 14

Give stages of spermatocytogensis in human. include which step has decreased proliferation. Also include numbers

Answer 14

A1: A1 + A2 (A1 reversion)
A2(1)>I(2)>B1(4)>1(8)>2(16)>TIDS (32)

INTERMEDIATE STEP is site of mutation and also decreased proliferation in humans. therefore decreased viability/ efficiency of humans

Question 15

What compartment does meiosis and mitosis happen in. Where is the spermacytotogenesis and meiosis steps ?

Answer 15

Spermatocytogensis (mitosis) is inthe basal compartment of the seminephorous tubule spermatagonia to spermatocyte

meiosis occurs inthe adluminal compartments. now a primary spermatocyte going under meiotic differentiation

Question 16

Explain steps of spermatogenesis that happen in sertoli cells (and identity their compartments). then explain what step is associated with the lumen.

Answer 16

Mitosis and meiosis are both associated with the nursing of the sertoli cells. in the mitotic process, this is located in the basal compartment. the meiotic process is in the adluminal compartment.

The release of SPERMATOZOA is located in the lumen.

Question 17

When does karyokinesis occur (stage +anatomy)? When does complete cytokinesis occur ?

Answer 17

Karyokinesis occurs in mitotic division in the basal compartment.

Cytokinesis occurs in last stages of spermatogenesis. While also surrounded by sertoli cells

Question 18

give meiosis process beginning with resting primary spermatid –>round spermatids

Where are most susceptible to damage? where is reduction occurring

Answer 18

Resting 1spermatocyte> Leptotene>Zygotene>pachytene>diplotene>2spermatocyte> 2 round spermatids = 4 round spermatids.

prophase (pachytene.diplotene) are most susectible to damage. mitotic reduction and division at secondary step

Question 19

Explain the process of spermiogenesis. What does it start at, what does it end at? what stage of sperm development is this? give the process and explain fate of organelles

Answer 19

During cytpdifferenciation, the round spermatid id developing into a swimming spermatazoa. Golgi- creates acrosomal vessicles with granulosa enzyme> fuse with nucleus > =devlopment of acrosomal cap> centriole form at distal+ proximal ends> =form axonome–tail + neck > cytoplasmic movement (axonome), nuclear elongation (tail). Microtubules = machete, SR-dissapear, mitocondria=move distal=midpeice , now, we’re swimmin.

Question 20

What is function of machete? What does it develop with?

Answer 20

Function is to surround lower (distal) portion of nucleus and direct cytoplasm downward. Develops along with flagella

Question 21

What separates the head from the tail

Answer 21

The capitulum

Question 22

Draw out sperm. Identify:

1. Head, midpiece, prinicpal, end piece
2. nucleus, acrosomal cap, post nuclear cap, capitulum, Post acrosomal sheath

Answer 22

GO !

Question 23

Define/ give function/ location of following:

1. Protamine
2. annulus
3. post nuclear cap
4. connecting piece
5. Capitulum
6. 9:2
7. Post acrosomal sheath

Answer 23

1. packing DNA into more compact form. Better than histones
2. Under mitocondria. (f)= separate the mid piece from principal tail
3. believe derived from machete. plays role in fertilization
4. allow for flexibility of flagella. located at the mid piece and surrounded by mitcondrial helix
5. Capitulum separate head from tail
6. 9 axonome : 2 microtubules (motility via dynein)
7. also attached and used for oocyte fertilization

Question 24

What is definition of spermatogenic cycle? why do we consider it a spatial AND temporal process. What are the days for spermatogenic cycle. What are days for spermatogenesis?

Answer 24

The time it takes for TWO different STEAM cells to initiate mitotic division at the SAME location within the seminiferous tubule.
Spatial- SAME location
Temporal- DIFFERENT times

64 days spermatogenesis (48)
16 days for spermatogenic cycle (12 days Rat)

Question 25

Compare Rat and human cycles start to finish

Answer 25

DO IT with group

Question 26

List 8 functions of sertoli cells during spermatogenesis

Answer 26

1. (pachytene - communication/ receiving of material via gap junctions.
2. ectoplasmic specializations for anchoring + remodeling
3. Elongation of spermatids + andherens that move material during cytoplasmic condensation
4. blood testes barrier
5. phagocytosis pf defective sperm
6. androgen binding protein
7. convert testosterone to E
8. produce inhibin