Testis And Reproductive Tract Biology

Front 1

describe development of the foetal testis

Back 1

germ cells move down to rest on the basement membrane of sertoli cells

germ cells differentiate into spermatogonial stem cells

peritubular myoid cells form (flattened smooth msucle like cells) around the tubules

Leydig cells form in interstitium between tubules - this also contains blood vessles and lymph

Front 2

describe the mechanism of development of the foetal testis by SRY

Back 2

1. SRY induces sertoli cell differentiation

2. sertoli cells form sex cords and then tubules

3. sertoli cells secrete DHH and PDGF-A to induce Leydig cell formation

Front 3

describe the Leydig cells

Back 3

the leydig cells function to make androgens mainly testosterone under the control of LH

in mammals there are two different populations of Leydig cells - one foetal and one adult

Front 4

what does this shwo

Back 4

1st image = foetal Leydig cells

2nd image = adult Leydig cells

Front 5

what additional function other than testosterone production do Leydig cells have

Back 5

make INSL3

a combination of this and testosterone is essential for testis descent

Front 6

how does the Leydig cell mak testosterone

Back 6

LH binds to Leydig cell and causes ATP to form cAMP which induces fromaton of StAR protein

StAR protein causes cholesterol to move into mitochondria

cholesterl forms pregenelone which moves out into mitochondria and induces testosterone formation

testosterone moves out into smooth ER and then leaves the Leydig cell

Front 7

what controls the action of Sertoli cells

Back 7

FSH and androgen

Front 8

what are the functions of Sertoli cells

Back 8

1. essential regulator of testis development

- SRY acts to form SC

- SC regulates development of other cell types

2. forms the blood testis barrier

- tight junctions between SC 'seal off' the lumen of the tubule

3. secrete AMH

- prevents paramesonephric duct development

4, in adult maintains the Leydig cells - mechanism unknown

Front 9

describe features of the peritubular myoid cell

Back 9

contractile

androgen-dependant

essential for normal spermatogenesis

Front 10

how is testis function controlled

Back 10

mainly by endocrine regulation through LH and FSH secretion from the pituitary

also some input from ACTH, GH and thyroid hormones

paracrine control also essential

Front 11

describe testes descent

Back 11

1..androgens cause suspensory ligament to degenerate and star the shortening of the gubernaculum

2. INSL3 acts to complete shortening of the gubernaculum and movement of the testes into the scrotum

Front 12

summarise male devlopment

Back 12

Front 13

describe spermatogenesis

Back 13

massive amplification of cell numbers

1. proliferation

2. meiosis

3. spermiogenesis - differentiation process

Front 14

describe the proliferation/spermatogonia stage of spermatogenesis

Front 15

describe the meiosis stage of spermatogenesis

Back 15

begin with diploid resting primary spermatocyte

1. DNA replication starts

2. chromosomes line up

3. 1st meiotic division

4. 2nd meiotic division

end up with a haploid round spermatid which goes on to enter spermiogenesis

Front 16

describe the spermiogenesis stage of spermatogenesis

Back 16

begins with round spermatid

1. nuclear condensation

2. acrosome forms from golgi

3. tail develops from centriole

4. cytoplasm re-distributes - residual body lost

5. mitochondria re-arrange in middle piece

final result is an elongated spermatid called a spermatozoa

Front 17

what is spermatogenesis controlled by

Back 17

space and time

Front 18

describe hormonal control of spermatogenesis

Back 18

control mainly through the Sertoli cells

Sertoli cells secrete FSH and testosterone which stimulates spermatogonial differentiation

testosterone accts through the Sertoli cells and PTMC to ensure the passage through meiosis

Testosterone stimulates spermiogenesis

Front 19

what is the function of the epididymis

Back 19

to induce sperm maturation

non-motile, non-fertile sperm enter at the head and then become fertile and motile as they travel down the epididymis

tail acts as sperm storage area

Front 20

describe the histological structure of the epididymis

Back 20

psudostratified, columnar epithelium with stereolcilia

epithelium gets smaller towards tail

androgen sensitive structure

Front 21

what is the function of the accessory glands

Back 21

add fluid to ejaculate

4 accessory glands:

seminal vesicles

prostate

bulbourethral glands

preputial glands

all are exocrine glands

may be essential for embryo development

Front 22

describe features of the seminal vesicles

Back 22

compound tubular glands

lined with tall columnar secretory epithelium

surrounded by fibro-muscular capsule