MCDB 240: Testes I

Question 1

what are the two major components of the testes?

Answer 1

spermatozoa: transmit male’s genes to embryo
hormones: need for maintenance of male reproductive functions

Question 2

go over the development of testes; define the role of SRY, TDF, and MIF

Answer 2

1) gonads are bipotential for two weeks
2) SRY gene on y-chromosome encodes testis determing factor (TDF)
3) TDF promotes mullerin inhibiting factor (MIF), prevents mullterian duct from forming
4) Wolfian duct forms

Question 3

define the wolfian duct and mullerian duct

Answer 3

wolfian: vas deferens and epidydimis
mullerian: fallopian, uterus, cervix, upper cervix

Question 4

describe the testes compartments; where do the spermatozoa reside, where do the androgens reside

Answer 4

spermatozoa develop w/i tubules, associated w/ Sertoli cells

androgens are synthsized between tubules IN leydig cells

both compartments are separated by cell barriers which develop puberty

Question 5

describe the three phases for spermatogenesis

Answer 5

1) mitotic proliferation produces a large # of cells
2) meiotic divisions promote gene diversity, halves chromosome #
3) cytodifferentiation packs chromosomes for delivery to oocyte

Question 6

list three types of cells in the testes

Answer 6

1) Sertoli
2) Leydig
3) germ cells: different stages of sperm development

Question 7

explain the importance of Leydig cells

Answer 7

• produce testosterone (downregulated LH), located externally outside basement membrane (b/t tubules)
• are interstitial endocrinocyteses
• contribute <1% of total testis mass
• activated by LH

Question 8

explain the origins of Leydig cells

Answer 8

1) differentiation from mesenchymal cells

2) leydig cells divide under influence influence of LH and FSH

Question 9

explain the importance of Sertoli cells

Answer 9

• think of them as the nurse cells
• PART of tubules, activated by FSH
• equivalent to ovarian granulosa cells (surround oocyte and control its development)
• provide nutrients/ions to spermatogonia (support and protect)
• produces inhibin (downregulates FSH)
• don’t divide in adult testis
• consist of the blood-testes barrier,* because sperm is antigenic to the body

Question 10

describe the blood-testes barrier

Answer 10

barrier b/t blood vessels and tubules, formed b/t Sertoli cells

Question 11

describe the order of spermatogonia maturation

Answer 11

Basal lamina

1) spermatogonia
2) mitosis
3) spermatocyte, 1st order
4) meiosis
5) spermatocyte, 2nd order
6) meiosis
7) spermatid
8) spermatogenesis
9) mature spermatid

Question 12

describe endocrine function

Answer 12

• occurs b/t tubules

- Leydig, again, important for production of androgens (testosterone)

Question 13

HPT axis: what is it and why is it important?

Answer 13

hypothalamus-pituitary testicular axis. HPT axis deals w/ endocrines.

male fertility depends on endocrine (distant) and paracrine (local) functions of androgens testes produces

Question 14

how do hormones work?

Answer 14

via cell membrane and sometimes nuclear receptors

Question 15

what determines how and which receptor a hormones reacts with?

Answer 15

the chemical structure (ensures RECEPTOR-SPECIFICITY)

Question 16

describe the feedback mechanisms in the HPT axis

Answer 16

1) hypothalamus
2) emits LHRH
3) pituitary
4) emits LH (Leydig) and FSH (Sertoli)
5a) Leydig produces testosterone (neg fb on pituitary and hypo)
5b) Sertoli produces inhibin (neg fb on pituitary and hypo)

Question 17

define feedback mechanism

Answer 17

action of a hormone increases or decreases effect of a hormone or itself

Question 18

go over testosterone in detail, from fetus to puberty, how it’s released, how it’s made, and how does it act

Answer 18

• testosterone is activated by maternal human chorionic gonadotropin (NCG) during fetal neonatal life
• low secretion until puberty
• puberty: increased testosterone b/c LH
• released in a pulsatile manner (as w/ LH)
• synthesized from cholesterol, obtained from blood-borned HDL’s
• acts via androgen receptors located in target cells to stimulated secondary characteristics
• negative feedback on Sertoli cells, acts to increase sperm

Question 19

go over inhibin; how does it cross-talk w/ testosterone

Answer 19

both control plasma FSH levels

Question 20

define hypogonadotropic hypogonadism

Answer 20

low testosterone + low FSH + low LH

Question 21

what is the percentage of free, unbound testosterone?

Answer 21

2%

Question 22

what are usually tested for hormones in a male?

Answer 22

FSH and testosterone; rare to see abnormalities in LH

Question 23

what has higher levels in pituitary cancers?

Answer 23

prolactin has 2x-3x higher levels; prolactinoma is a type of pituitary cancer

Question 24

what can be used to treat prolactinoma?

Answer 24

bromacriptine is used to treat elevation of prolactin

Question 25

define spermatogenesis

Answer 25

the maturation of spermatogonia to spermatozoa

-mitosis AND meiosis are involved, w/ changes in both cytoplasmic and nuclear architecture

Question 26

how is the outcome of spermatogenesis determined?

Answer 26

1) proliferation
2) differentiation
3) apoptosis

Question 27

what crosses the blood-testes barrier?

Answer 27

spermatocytes pass via tight junction to become spermatids, then elongated spermatids, then mature spermatozoa (differentiation)