Spermatogenesis

Question 1

what is the developmental pathway from germ cell to mature sperm?

Answer 1

spermatogenesis

Question 2

when and where does spermatogenesis occur?

Answer 2

at puberty
in the recesses between the Sertoli cells

Question 3

what are the three major phases of spermatogenesis?

Answer 3

(1) proliferative phase where sperm stem cells (spermatogonia) increase by mitosis
(2) meiotic phase where there are two divisions that create the haploid stage
(3) postmeiotic “shaping” phase - spermiogenesis - the round
cells (spermatids) eject most of their cytoplasm and become the streamlined sperm

Question 4

what do you call the primordial germ cell when they arrive at the genital ridge of a male embryo?

Answer 4

gonocytes

Question 5

as the sex cords turn into the seminiferous tubules, the gonocytes in them become ___________

Answer 5

undifferentiated spermatogonia

Question 6

in the seminiferous tubules, the undifferentiated spermatogonia are located in the __________

Answer 6

basal end

Question 7

what is the epithelium of the seminiferous tubules?

Answer 7

sertoli cells

Question 8

spermatogonia reside in stem cell niches at the junction of the (3)

Answer 8

(1) sertoli cells
(2) interstitial leydig cells
(3) testicular blood vessels

Question 9

testosterone-producing cells

Answer 9

leydig cells

Question 10

what joins the spermatogonia directly to the sertoli cells and nourishes the developing sperm?

Answer 10

adhesion molecules

Question 11

what type of spermatogonia does the mitotic proliferation amplify?

Answer 11

type A spermatogonia (more than 1000 sperm per second in adult human males)

Question 12

As the spermatogonia divide, they remain attached to each other by _________

Answer 12

cytoplasmic bridges

Question 13

since cytoplasmic bridges are fragile, what happens when one cell splits from the others

Answer 13

it becomes an undifferentiated spermatogonia again

Question 14

what makes the glial cell line-derived neurotrophic factor (GDNF)? (2)

Answer 14

(1) sertoli cells
(2) myoid cells

Question 15

what surrounds the tubules and give them strength and easticity?

Answer 15

myoid cells

Question 16

what helps keep the spermatogonia from dividing as stem cells?

Answer 16

GDNF (a paracrine factor)

Question 17

what activates the Stra8 transcription factors during puberty that causes the levels of the BMP8b paracrine factor to reach a critical concentration

Answer 17

retinoic acid levels

Question 18

what instructs spermatogonia to produce receptors that enable them to respond to proteins such as stem cell factor (SCF)

Answer 18

BMP8b

Question 19

what secretes stem cell factors?

Answer 19

sertoli cells

Question 20

The transition between mitotically dividing spermatogonia and the spermatocytes that initiate meiosis appears to be mediated by the opposing influences of _____ and ______

Answer 20

GDNF and SCF

Question 21

what promotes the transition to spermatogenesis?

Answer 21

stem cell factors

Question 22

what promotes the division of spermatogonial stem cells

Answer 22

GDNF

Question 23

(meiotic phase)
Spermatogonia with high levels of Stra8 and responding to SCF divide to become ___________

Answer 23

type B spermatogonia

Question 24

(meiotic phase)
what are the precursors of the spermatocytes and are the last cells of the line that undergo mitosis?

Answer 24

type B spermatogonia

Question 25

(meiotic phase) type B spermatogonia divide once to generate the ____________, each of these undergo the first meiotic division to yield a pair of __________

Answer 25

primary spermatocytes secondary spermatocytes

Question 26

(meiotic phase) what do you call the haploid cells formed after the second division of meiosis?

Answer 26

spermatids (still connected to one another through their cytoplasmic bridges)

Question 27

(meiotic phase) what does this mean? The spermatids that are connected in this manner have haploid nuclei but are functionally diploid, since a gene product made in one cell can readily diffuse into the cytoplasm of its neighbors.

Answer 27

Imagine a bunch of young tadpoles still connected by little strings. Each tadpole (spermatid) has half the usual number of instructions (haploid), but they can share what they make (proteins and such) with their neighbors through the strings. So, even though they're individuals, they can kind of work together as a team to develop properly.

Question 28

(meiotic phase) during the divisions from undifferentiated spermatogonia to spermatids, the cells travel from the basal lamina of the seminiferous tubule and closer to where?

Answer 28

lumen

Question 29

(meiotic phase) what happens to the spermatids as they move toward the border of the lumen? what do they turn into?

Answer 29

they lose their cytoplasmic connections and differentiate into spermatozoa

Question 30

(meiotic phase) in humans, how many days does it take for spermatogonial stem cell to mature into spermatozoa?

Answer 30

65 days

Question 31

where is a spermatogenic cycle and spermatogenic wave observed?

Answer 31

along the seminiferous tubule

Question 32

a cycle of progressive stages occurring within a particular segment of the seminiferous tubule

Answer 32

spermatogenic cycle (cycle: same stage reappears for a certain duration at a particular segment)

Question 33

how many spermatogenic cycles does a mouse have? (no. of stages and number of days)

Answer 33

twelve stages numbered from I to XII occurring over 8.6 days

Question 34

how many spermatogenic cycles do humans have? (no. of stages and number of days)

Answer 34

six stages (I-VI) in a cycle and it takes four 16-day cycles for a spermatogonium to be transformed into a spermatozoon

Question 35

refers to the distance from one stage to another similar stage

Answer 35

spermatogenic wave

Question 36

how does the spermatogenic wave move? where is its direction headed towards?

Answer 36

moves in spirals (corkscrew) towards the inner part of the lumen

Question 37

in the spermatogenic wave, where does the spermatogonia lie?

Answer 37

outside, on the edge of the tubule, at the beginning of the spiral

Question 38

what is the end of the spermatogenic cycle called? on what phase of development is the sperm located there?

Answer 38

lumen fully developed sperm

Question 39

as time goes on, the wave of spermatogenesis is shifted towards the ______ in order to always ________

Answer 39

right newly begin again

Question 40

info

Answer 40

spermatogenesis - occurs in overlapping waves which pass along the tubules of the testis - the stages of spermatogenesis observed at any given level of a tubule will be different - each specific segment of the tubule is in one stage of the cycle at a certain time - wave moves slowly

Question 41

(oldest wave) what is/are seen in the oldest wave? where is it seen?

Answer 41

cells bordering the lumen maturing spermatozoa / metamorphosing spermatids

Question 42

(intermediate wave) where are the cells seen?

Answer 42

cells in the middle layer of the tubular wall

Question 43

(youngest wave) where are the cells seen? at what phase of devt. are they?

Answer 43

cells near the outer surface of the tubule spermatogonia ready to undergo meiosis

Question 44

how are we able to observe all the stages of spermatogenesis in just one section of the testis?

Answer 44

because each specific segment of the tubule is in one stage of the cycle

Question 45

what are the glands in which the male reproductive cells are formed?

Answer 45

testes or testicles (they lie one on each side in the scrotum)

Question 46

what is the shape of the testes? what is its size? where is its long axis directed?

Answer 46

oval one and a half inches long long axis directed downward, backward, and inward

Question 47

what are the functions of the testes? (2)

Answer 47

(1) producing sperm from stem cell spermatogonia (2) producing androgens (maintain and regulate androgen mediated functions throughout the body)

Question 48

compare the shape of the frog testis and mammalian testis

Answer 48

frog: elongated ovoid mammalian: ovoid

Question 49

what is a strong fibrous coat, from which vertical and horizontal septa penetrate into the substance, dividing it into compartments or lobules?

Answer 49

tunica albuginea

Question 50

where are the seminiferous tubes coiled?

Answer 50

tunica albuginea

Question 51

what consists of a basement membrane surrounding several layers of epithelial cells, some of which are constantly being transformed into spermatozoa or male sexual cells? (it is estimated that the total length in the two glands is little short of a mile)

Answer 51

seminiferous tubules

Question 52

what is a plexus of tubules into which the seminiferous tubes open?

Answer 52

rete testis

Question 53

what is soft body lying behind the testis?

Answer 53

epididymis

Question 54

what is the enlarged part (head) of the epididymis?

Answer 54

globus major

Question 55

what is the lesser swelling (tail) part of the epididymis?

Answer 55

globus minor

Question 56

what is the epididymis made of? how long is it?

Answer 56

made up of a convoluted tube about 20ft. long

Question 57

what comes off of the epididymis?

Answer 57

one long diverticulum (vas aberrans)

Question 58

what is the continuation of the tube of the epididymis and starts at the globus minor?

Answer 58

vas deferens

Question 59

what is the initial appearance of the vas deferens? where does it eventually run to?

Answer 59

at first it is convoluted soon it becomes straight - runs up on the inner (mesial) side of the epididymis to the external abdominal ring in the abdominal wall

Question 60

what is the connective tissue sheath surrounding the testis?

Answer 60

tunica albuginea

Question 61

what are the 2 kinds of epithelia the testis consists of?

Answer 61

(1) germinal epithelium (2) glandular epithelium

Question 62

what are the compartments of the testis separated by septula?

Answer 62

seminiferous tubule

Question 63

what is the stratified epithelium that is a gametogenic cell lining the seminiferous tubule?

Answer 63

germinal epithelium

Question 64

what are somatic cells that form part of the glandular epithelium of the testis and are also non-gametogenic?

Answer 64

leydig and sertoli cells

Question 65

where are leydig cells/interstitial cells located?

Answer 65

at the septula (found in between seminiferous tubules outside of the basement membranes)

Question 66

what are ovoid cells with granulated cytoplasm, which are responsible for the secretion of the male hormone testosterone stimulated by luteneizing hormone in anterior pituitary gland?

Answer 66

leydig cells/interstitial cells

Question 67

what hormone do leydig cells/interstitial cells secrete? what stimulates this hormone?

Answer 67

testosterone (male hormone) luteneizing hormone in anterior pituitary gland?

Question 68

where are Sertoli/ Sustentacular cells located?

Answer 68

at the basal layer of the germinal epithelium (occur singly) - when found at free apical ends (end of sertoli cell, facing the lumen), it is associated with the development of gametes

Question 69

what is the appearance of Sertoli/ Sustentacular cells? (4)

Answer 69

(1) few large triangular cells (2) bear a prominent nucleus (3) have an elongated pyramidal epithelial cell ( its base resting on the edge of the seminiferous tubule wall and its pointed end facing the lumen) (4) pale in histological section

Question 70

what is the order of development of sperm cells? (5)

Answer 70

(1) spermatogonia (2) primary spermatocytes (3) secondary spermatocytes (4) spermatids (5) spermatozoa

Question 71

what is the male form of gamecytogenesis and involves stem cells (spermatogonia) dividing to replace themselves and to produce a population of cells destined to become mature sperm?

Answer 71

spermatocytogenesis

Question 72

what are the 3 functionally separate spermatogonial cell types that are recognized on the basis of the appearance of the nuclei?

Answer 72

(1) type A dark spermatogonia (Ad) (2) type A pale spermatogonia (Ap) (3) type B spermatogonia (B)

Question 73

what type of spermatogonia maintains the population of spermatogonia?

Answer 73

type Ad spermatogonia

Question 74

how does type Ad spermatogonia maintain the supply of stem cells for spermatogenesis?

Answer 74

each type Ad spermatogonium divides to produce (1) another type Ad spermatogonium (carry on spermatogenesis) (2) one type Ap spermatogonium (differentiates further)

Question 75

Type Ap spermatogonia repeatedly divide _____________ to produce __________ linked by __________.

Answer 75

mitotically identical cell clones cytoplasmic bridges

Question 76

what is the stage where repeated division of type Ap ceases and the cells differentiate into type B spermatogonia?

Answer 76

spermatogonial phase

Question 77

what happens when the repeated division of type Ap ceases?

Answer 77

they differentiate into type B spermatogonia

Question 78

Type B spermatogonia undergo ________ to produce diploid intermediate cells called _____________

Answer 78

mitosis primary spermatocytes

Question 79

how long does the entire process of spermatogenesis in human take? what if the includes the transport on ductal system?

Answer 79

74 days 3 months

Question 80

how long does it take for spermatogenesis in rats to take place?

Answer 80

20 days