CH 10 Endocrinology of the Male and Spermatogenesis

Question 1

What does the production of fertile spermatozoa require?

Answer 1

-endocrine regulation of the testis

-Mitotic divisions of spermatogonia

-meiotic divisions resulting in haploid spermatids
morphologic transformation of spermatids to spermatozoa

Question 2

the endocrine requirements for sperm to be produced are what?

Answer 2

-adequate production of GNRH from hypothalamus

-FSH and LH secretion from anterior pituitary gland

-secretion of gonadal steroids (testosterone mostly)

Question 3

what center(s) in the hypothalamus was the male develop?

Answer 3

the male does not develop a surge center and only has the tonic center in the hypothalamus

Question 4

what is the discharge of GNRH from the hypothalamus like in the male?

Answer 4

occurs in frequent, intermittent bursts

Question 5

what are LH pulses closely followed by?

Answer 5

pulses of testosterone

Question 6

why is pulsatile LH important?

Answer 6

high interstitial concentrations of testosterone are essential to spermatogenesis but need not to be present continually. The leydig cells may become refractory to high levels of LH. Thus the pulses will maintain a constant hormonal supply.

Question 7

what is a refractory period?

Answer 7

Unresponsive or not yielding to treatment

Question 8

why is pulsatile testosterone important?

Answer 8

an increase in testosterone leads to decreased FSH over time due to feedback on the anterior pituitary. However sertoli cells need FSH to function properly. This periodic decrease in testosterone remove the negative feedback on FSH so sertoli cells can continue to function appropriately

Question 9

What two things can testosterone do?

Answer 9

-cross basement membrane and diffuse into Sertoli cells and be converted into dihydrotestosterone and estradiol 17 beta

-Along with estradiol 17 beta, provide the negative feedback on the hypothalamus through vasculature

Question 10

what are Leydig cells similar to?

Answer 10

Similar to theca interna

Question 11

what are sertoli cells similar to?

Answer 11

similar to granulosa cell

Question 12

What are the three phases of spermatogenesis?

Answer 12

Proliferation, meiosis and differentiation

Question 13

what is proliferation of spermatogenesis?

Answer 13

mitotic divisions involving proliferation and maintenance of spermatogonia

Question 14

what is meiosis of spermatogenesis?

Answer 14

Spermatocytes give rise to spermatids

Question 15

what is differentiation of spermatogenesis?

Answer 15

morphological transformation of spherical spermatids into fully differentiated, highly specialized and elongated spermatozoa

Question 16

what are the three types of spermatogonia?

Answer 16

A spermatogonia (A1-4), I spermatogonia, and B spermatogonia

Question 17

How is spermatogenesis different from oogenesis?

Answer 17

a constant pool of sperm is always present. There is a constant supply stem cells that divide by topically to provide a continual supply of A spermatogonia therefore, the process of spermatogenesis can continue indefinitely.

Question 18

what are developing germs cells connected by?

Answer 18

interconnected by intracellular ridges. The cytoplasm of an entire cohort of cells is interconnected. The exact function of these intercellular bridges is not known but it is believed that they provide communication between cells that allows for synchronized development among cells of a cohort

Question 19

where are spermatogonia found and where do they move upon maturity?

Answer 19

Only mature spermatogonia are found in the basal compartment of the seminiferous tubules. As sperm mature, they moved toward the lumen

Question 20

What is differentiation marked by?

Answer 20

marked by development of the flagellum and mitochondrial Helix

Question 21

what are the four phases of differentiation?

Answer 21

golgi phase, cap phase, acrosomal phase, and maturation phase

Question 22

what happens during the golgi phase?

Answer 22

spermatid contains a large highly developed Golgi apparatus (intracellular packaging system for all secretory cell types). pro acrosomal granules form from the Golgi apparatus. these granules fused to form that acrosomic vesicle that contains a dense, acrosomic granule, smaller vesicles are continually added so that the acrosomic vesicle increases in size.

Question 23

What do centrioles do during the golgi phase?

Answer 23

Centrioles migrate from the cytoplasm to the base of the nucleus. The proximal central gives rise to the implantation apparatus that allows the flagellum to be attached to the nucleus. The distal central gives rise to the axoneme - the central portion of flagellum or sperm tail

Question 24

what happens during the cap phase?

Answer 24

acrosome forms distinct, easily recognized cap over the anterior portion of the nucleus. Has an outer across normal membrane in an inner acrosomal membrane.

Question 25

what happens to the Golgi body during the cap phase?

Answer 25

after completing its function of packaging, the acrosomal contents and membranes, the Golgi body moves away from the nucleus towards the caudal end. The primitive tail forms from the distal centriole and projects away from the nucleus toward the lumen of the seminiferous tubule

Question 26

What happens during the acrosomal phase?

Answer 26

Nucleus and cytoplasm began to elongate. The cytoplasm continues to spread until it covers about 2/3 of the anterior nucleus. Mitochondria appear. During this phase, the sperm become deeply embedded in the sertoli cells with their tails protruding into the lumen of the ST

Question 27

What does the manchette form during the acrosomal phase?

Answer 27

Once a unique set of microtubules = cylindrical elements that move chromosomes on the nuclear spindle during miosis and mitosis. Some of the manchette will form the post nuclear cap

Question 28

What happens during the maturation phase?

Answer 28

mitochondria assemble around flagellum and assemble in a helical fashion dash this forms the middle piece of the sperm tail. Dense fibers form around the flagellum. The post nuclear cap is formed from the microtubules of the manchette.

Question 29

What is in between the middle and principal piece of the sperm tail?

Answer 29

The annulus forms the juncture between the middle piece and the principal piece of the sperm tail

Question 30

What is spermiaition?

Answer 30

sperm are released from the Sertoli cells into the lumen of the seminiferous tubules

Question 31

spermiaition analogous to ovulation in the female except…

Answer 31

• Internal release of gametes instead of external
• continuously instead of cyclically

Answer 32

nucleus + acrosome + post nuclear cap

Question 33

What is the acrosome?

Answer 33

covers 2/3 of the anterior portion of the nucleus, membrane bound by lysosome which contains hydrolytic enzymes.

Question 34

what does the tail of sperm consist of?

Answer 34

middle piece + principle piece + terminal piece

Question 35

What is the head of sperm consist of?

Answer 35

Apical ridge, acrosome, plasma membrane, post nuclear cap, nuclear ring, and nucleus

Question 36

What is the acrosome reaction?

Answer 36

highly specialized exocytosis that allows release of enzymes packaged in acrosome to digest or penetrate the zona pellucida

Question 37

what is the nucleus like in a sperm head?

Answer 37

flattened Oval and surrounded by nuclear membrane. Chromatin is compacted in almost inert; DNA is highly keratinized. Keratinoid proteins found in hair, claws, hooves, and feathers. Have a high degree of disulfide crosslinking. This is important for protecting the DNA of sperm as it travels to the point of fertilization

Question 38

What is the tail of sperm composed of?

Answer 38

Capitulum, middle piece, principle piece, internal piece

Question 39

What is the capitulum of the tail?

Answer 39

It’s in to the implantation socket at the posterior portion of the head

Question 40

What is the middle piece composed of?

Answer 40

Composed of coarse outer fibers and laminated columns and mitochondrial Helix

Question 41

What do laminated columns do in sperm tail?

Answer 41

give neck region flexibility when sperm becomes motile so tail can move laterally from side to side during flagellar beat

Question 42

what is the mitochondrial Helix?

Answer 42

middle piece is surrounded by a mitochondrial sheath that provides energy/ATP

Question 43

what does the principal piece consist of?

Answer 43

annulus and end of flagellum mark boundaries of peace the accident is surrounded by 9 dense coarse outer fibers these are unique to the flagellum of sperm.

Question 44

what is the terminal piece in sperm?

Answer 44

end portion of the tail

Question 45

How long does one cycle of spermatogenesis last in the bull and how many cycles does it take for a spermatogonia to reach maturity?

Answer 45

1 cycle = 13.5 days in the bull

-It takes 4.5 cycles per a spermatogonia to develop and reach spermiation
13.5 x 4.5 cycles = 61 days in the bull

Question 46

What is a spermatogenic wave?

Answer 46

distribution of stages along the length of the seminiferous tubule in any instant time. During the wave, each stage of seminiferous epithelium changes to a more advanced phase.

Question 47

What stage of sperm does heat stress effect first? Does heat stress kill sperm?

Answer 47

heat stress affects the spermatids first and then spermatocytes but not much effect on spermatogonia. he stressed does not kill sperm it merely slows down spermatogenesis

Question 48

What are the events of a sperm’s life?

Answer 48

Fertilization of the oocyte or degeneration

Question 49

what type of metabolism does sperm have?

Answer 49

Catabolic: sperm DNA is inactive - breakdown of substrates into chemical ATP

Question 50

what is the order of sperm damage during heat stress?

Answer 50

1. Spermatids –> most sensitive (why? Undergoing morphological changes)
2. Secondary spermatocyte –> undergoing meiosis
3. Primary spermatocyte

Question 51

How long will heat stress effects last?

Answer 51

65 days