Reproductive Physiology of the Male

Question 1

what enzyme converts testosterone into estradiol

Answer 1

aromatase

Question 2

what enzyme converts testosterone into DHT

Answer 2

5𝛼-reductase

Question 3

what is de la chapelle syndrome

Answer 3

XXsry+
male internal and external genitalia but infertile due to lack of Eif2s3y gene

Question 4

what does masculinization of the sexually dimorphic nucleus require

Answer 4

estradiol (E2)
testosterone produced in the testes converted to E2 via aromatase

Question 5

what protects E2 from the female from entering the brain in the fetus

Answer 5

𝛼fetoprotein

Question 6

3 parts of the male brain and what they are regulated by

Answer 6

1. Libido - estradiol E2 (can be testosterone converting to E2)
2. male behaviors (aggression, scent marking) - testosterone
3. pulse generator - kisspeptin producing neurons w/ Testosterone, E2 and P4

Question 7

explain the HPT axis

Answer 7

kisspeptin
GnRH
LH –> leydig cells, T production
FSH –> sertoli cells, inhibin, androgen binding protein and acts on sperm cells supporting mitosis/meiosis

Question 8

days for spermatogenesis

Answer 8

60 days

Question 9

days for epididymis travel

Answer 9

10-14 days

Question 10

how do anabolic steroids affect reproductive function

Answer 10

5-10x T levels needed to maintain spermatogenesis
anabolic steroids only have 2-3x T = no spermatogenesis

Question 11

what produces melatonin
precursor for melatonin
function of melatonin

Answer 11

pineal gland in absence of light
tryptophan
acts on pulse generator cells to regulate GnRH

Question 12

how do animals regulate seasonal breeding?

Answer 12

melatonin

Question 13

long day breeders (horse, wolf, fox, rodents, birds)

Answer 13

melatonin (-) kisspeptin
decreases GnRH

Question 14

short day breeds (cattle, elk/deer, sheep)

Answer 14

melatonin (+) kisspeptin
increases GnRH

Question 15

how does melatonin differ between males and females

Answer 15

males less affected - most species produce sperm year round

Question 16

describe the effects on sperm with short term heat vs long term heat

Answer 16

short term heat - sperm abnormalities during spermatogenesis
long term heat - spermatogenesis ceases (e.g. cryptorchid)

Question 17

Four Mechanisms of Thermoregulation

Answer 17

1. arterioles/venous blood close to surface of skin of scrotum for dissipation
2. sweat glands in skin of scrotum for evaporation
3. pampiniform plexus (countercurrent exchange)
4. tunica dartos & external cremaster muscle - contract/relax of scrotum and testes respectively

Question 18

how does illness, stress and fat affect reproduction

Answer 18

illness - fever - elevated temp - negative effect on spermatogenesis
stress - cortisol - decreases kisspeptin - decreases T
fat - difficult thermoregulation in scrotum

Question 19

at what temperature can spermatogenesis occur

Answer 19

temperatures 2-5 degrees
lower than body temp

Question 20

describe cryptorchidism

Answer 20

no spermatogenesis
leydig cells functional - T produced
increased incidence of seminoma
heritable or environmental

Question 21

describe spermatocytogenesis

Answer 21

occurs in basal compartment
spermatogonia > primary spermatocytes

Question 22

describe meiosis I

Answer 22

primary spermatocyte > secondary spermatocyte

Question 23

describe meiosis II

Answer 23

secondary spermatocyte > spermatid

Question 24

describe spermiogenesis

Answer 24

occurs in adluminal compartment
no cell division
spermatids (round then elongated) > spermatozoa

Question 25

what is critical for spermiogenesis? why?

Answer 25

**Testosterone** because cells cannot make mRNA = no proteins need sertoli cells to make enzymes and proteins via androgen binding protein maintain testosterone levels so cells can mature and progress

Question 26

function of the blood testis barrier

Answer 26

protects developing sperm from immune system attack

Question 27

what is unique about the stages in seminiferous tubules

Answer 27

see different stage in each seminiferous tubules on cross section - allows release of sperm everyday

Question 28

what determines the shape and size of sperm heads in different species

Answer 28

proamines

Question 29

what structure of the sperm head is responsible for penetrating/digesting the zona pellucida of the oocyte

Answer 29

acrosome

Question 30

where are the centrioles located

Answer 30

neck region of sperm

Question 31

what part of the sperm contains the mitochondria

Answer 31

midpiece

Question 32

what is the cytoplasmic droplet

Answer 32

cytoplasms migrates down tail as sperm matures through the epididymis and is lost when sperm becomes motile

Question 33

what occurs if the cytoplasmic droplet remains

Answer 33

problem in spermiogenesis or epididymal maturation → decreased fertility

Question 34

what is the order of sperm transport to the epididymis

Answer 34

sertoli cell > seminiferous tubule > rete testis > efferent ducts > head of epididymis

Question 35

what is the only part of the male reproductive tract that has cilia

Answer 35

efferent ducts

Question 36

head of epididymis muscle? epithelium? villi? fertility? motility?

Answer 36

thin smooth muscle more epithelium, long microvilli (bc majority of fluid is absorbed) not fertile not motile

Question 37

body of epididymis muscle? fertility? motility?

Answer 37

thin smooth muscle not fertile not motile

Question 38

tail of epididymis muscle? epithelium? villi? fertility? motility?

Answer 38

large amount smooth muscle less epithelium , short microvilli fertile not motile

Question 39

when does sperm become motile

Answer 39

when mixed with seminal plasma due to water, proteins, sugars, salts, citrate/bicarb, gel

Question 40

erection is parasympathetic or sympathetic

Answer 40

parasympathetic

Question 41

ejaculation is parasympathetic or sympathetic

Answer 41

sympathetic

Question 42

what 2 structures of the female require sperm motility

Answer 42

cervix utero-tubule junction NOT the uterus bc sperm moves via uterine contraction

Question 43

what is capacitation and where does it occur

Answer 43

oviductal epithelium loss of cholesterol, increase in IC calcium, loss of seminal plasma proteins coating the cell exposing receptor for zona pellucida

Question 44

what induce the acrosomal reaction

Answer 44

zone pellucida proteins

Question 45

what is the acrosomal reaction

Answer 45

release of acrosomal enzymes (ZP1, ZP2, ZP3) to expose receptor for oolemma so sperm (sumo 1) can bind to oolemma fusing sperm and oocyte membranes

Question 46

methods of semen collection

Answer 46

artificial vagina "gold standard" electroejaculation chemical ejaculation manual stimulation