Testes and Spermatogenesis

Question 1

main testis function (general)

Answer 1

sperm and androgen production

- nearly all testosterone is made by them (Leydig cells
5% is made in zona reticularis of adrenal gland)

Question 2

dense irregular CT surrounding the testes

Answer 2

tunica albuginea

Question 3

mediastinum testis

Answer 3

inward projection of the tunica albuginea on the posterior surface of the testis

holds the rete testis

Question 4

septa in testis

Answer 4

CT going from the capsule inward

splits the testis into 250 lobules

Question 5

Cells that are not inside the convulted tubule in testis

Answer 5

fibroblasts = cells with a thin nucleus outside of the tubule

Leydig cells = bigger cells with bigger nucleus outside of the tubule

Question 6

Leydig cells

Answer 6

make and secrete testosterone

variable in size but round usually

cytoplasm = acidophilic

a lot of large smooth ER and filled with lipid droplets to create steroids

Question 7

inside the convoluted seminiferous tubule

Answer 7

consists of lamina propria with myoid cells and collagen fibrils

basement membrane

seminiferous epithelium = complex stratified
- has sertoli cells and spermatogenic cells on top of one another

Question 8

myoid cells in convoluted seminiferous tubule

Answer 8

flat elongated SmM like cells that contract to move sperm and fluid in the duct system

Question 9

where a more immature spermatogenic cells located?

Answer 9

rest on basal lamina = ‘spermatogonia’

Question 10

spermatids

Answer 10

most mature spermatogenic cells

located at the apical portion of sertoli cells (bordering the lumen)

Question 11

progression of spermatogenesis (general)

Answer 11

1 spermatogonum –>

1 primary spermatocyte –> 1st round of meiosis

2 secondary spermatocyte –> 2nd round of meiosis

4 total spermatids –> maturation (spermiogenesis)

4 spermatozoa (mature sperm cells)

Question 12

the secondary spermatocyte cells to the late spermatids are connected via….

Answer 12

cytoplasmic bridge

essential for synchrous development

allow free communication between cells

***allow haploid cells to be supplied with proteins and RNAs encoded by complete diploid genome

Question 13

how does the cytoplasmic bridge go away

Answer 13

sertoli cells phagocytose the unneeded cytoplasm while making mature…

spermatozoa

Question 14

what spermatocyte are really hard to find histologically

Answer 14

secondary

Question 15

spermatogonia

Answer 15

most immature and relatively large

rounded nucleus with chromatin

always in contact with basal lamina, so very easy to spot

divide and differentiate into primary spermatocytes

3 types:

1. type A dark
2. type A pale
3. type B

do not need to be able to tell the difference

Question 16

primary spermatocyte

Answer 16

largest germ cell present and cells that are spherical or ovoid

large round nucleus with heterochromatin***

undergo first meiosis to produce 2 secondaries

Question 17

when does genetic variation via crossover and random inclusion of either paternal chromosome occur?

Answer 17

1st meiosis

primary –> secondary spermatocyte

Question 18

secondary spermatocyte

Answer 18

half the size as primary

differentiates into 2 spermatids

Question 19

spermatids

Answer 19

will undergo no further division…instead undergo spermiogenesis and differentiate into spermatozoa

early spermatids =
- small size, with round nuclei and condensed chromatin

late

• elongated, condensed nucleus
• has a tail and is attached to apical portion of sertoli bordering the lumen
• looks like sperm but the cytoplasmic cross bridge still present

Question 20

4 processes of spermiogenesis

Answer 20

1. nuclear condensation and elongation
2. acrosome formation to break down zona pellucida of ovum and allow for fertilzation to occur
3. flagellum formation
4. cytoplasm reduction

Question 21

rate of spermiation determines what

Answer 21

of sperm in semen

Question 22

spermatozoon

Answer 22

free in lumen

much of cytoplasm has been phagocytosed by sertoli cells

released as non-motile, gain motility in epididymis, wehre they are stored before ejaculation

Question 23

sertoli cells GENERAL function

Answer 23

• structural organization to the tubules
• support and nurse maturing sperm cell by exchanging substrates and wastes…also phagocytosed unneeded cytoplasm
• unable to differentiate
• extend from basement membrane to lumen surface of epithelium

Question 24

structure of sertoli cells

Answer 24

tall and columnar

nucleus is ovoid, triangular, and large and lightly staining

nucleolus is large and prominent (like eye of owl)

cell borders are not visible

well developed RER, SER, lipid droplets, and lots of mitochondria

Question 25

endocrine functions of sertoli cells

Answer 25

estradiol = aromatase converts testosterone --> estradiol in neonatal and prepubertal mammals to inhibit testosterone production by leydig cells and regulate spermatogenesis inhibin B = (-) feedback on FSH mullerian-inhibiting factor (MIH) = cause regression of mullerian ducts growth factors (GDNF and stem cell factor) = maintain the number of spermatogonia

Question 26

exocrine sertoli cell

Answer 26

fluid = helps move sperm along seminiferous tubules to intra-testicular ducts androgen binding protein (ABF) - promoted by FSH - binds testosterone to make it lipophilic and keep it in the lumen of the tubules - more testosterone in lumen is best for sperm production

Question 27

tight junction between sertoli cells

Answer 27

divide epithelium into basal and adluminal compartments basal = spermatogonia and early spermatocytes adluminal = rest of the cells early spermatocytes move to adluminal compartment by sertoli cells making a new tight junction under the cell that is moving compartments...the tight junction above the cell degrades forms the basis for blood-testis barrier - allow ionic, amino acid, carb, and protein composition to be different from that of blood plasma

Question 28

where does meiosis and spermiogenesis occur

Answer 28

adluminal compartment

Question 29

what is very sensitive to elevated temperature

Answer 29

seminiferous epithelium (not spermatogonia) why testis dangle outside body

Question 30

Cryptorchidism

Answer 30

undescended testis - causes degeneration of spermatogenic cells, besides spermatogonia, leaving only intersitial structures like fibroblasts and leydig cells

Question 31

how is temperature in testis regulated

Answer 31

through the pampiniform plexus has a countercurrent heat exchange between the plexus and the testicular artery to cool off the arterial blood also uses cremaster muscle and dartos muscle

Question 32

pampiniform veins

Answer 32

have uncharacteristically thick SmM, which allows for propulsion of blood against gravity into abdominal veins

Question 33

Cremaster reflex

Answer 33

works by contraction and relaxation of the cremaster (skeletal) allowing scrotum to move toward or away from the body to regulate temperature cold temperature also causes dartos (SmM) muscle of the scrotum to contract --> scrotum wrinkles which helps regulate heat loss