4.2 Day 26 Reproduction Testes

bio mechanisms that contribute to development of sex-related traits in humans

gametes (reprod. cells)

chromosomes

genes

endocrine system (reg of H)

physical characteristics

sex determination in non-humans

temp. dependent sex determination

haplodiploidy: sex deter. by chromosome #

hermaphroditism: both M + F sex organs or changing from M → F

alternative (non XX/XY) chrom. system

light dependent sex determination

hermaphroditism

non-humans: functional sets of M + F organs

in humans: functional sets of testes + ovaries is rare

• intersex biologically accurate

gonads glands

compound

endocrine → hormones (steroids/peptides)

holocrine → whole cells (gametes)

testis composed of

seminiferous tubule

• sperm + precursors

• steroli cells

leydig cells

testis sperm + precursors

move towards lumen as they mature

Sertoli cells produce

nutrition to germ cells

androgen binding proteins (ABP)

GnRH

MIH (hullarian inhibiting H) (development only)

inhibit (peptide, blocks FSH at pit.)

leydig cells

interstitial (btw seminiferous tubules)

primarily endocrine in funct.

prod. testosterone + 5aDHT (dihydrotestosterone)

(many cells can’t use test., convert to 5DHT or E2 for effect)

classic steroidal mechanism of action

T diffuses into target cell

T converts to DHT

DHT translocates into nucleus

DHT binds nuclear receptor

DHT/R dimerizes

dimer binds DNA at androgen response element (ARE)

influence gene expression

androgen function in organisms w/ testes

1. embryonic indication + differentiation of testes-related organs ducts + glands

2. functional devel. of testes-related organs

3. spermatogenic: sperm maturation

4. protein anabolic

5. erythropoietic

6. stims. CNS to inc. respiration + metabolic rate

7. behavior

8. secondary sex characteristics

embryonic induction + differentiation accessory organs

prostate

bulbourethral gland

seminal vesicles

spermatogenic function

sperm maturation

protein anabolic function

T directly in skeletal muscle

erythropoietic function

incr. # of RBCs to inc oxygen capactiy

behavior function examples

doves: courtship, aggressiveness song

penile reflexes during copulation

secondary sex characteristics function examples

hair distribution

coloration/pigmentation (non-humans)

antlers

androgen function in organisms w/ functional ovaries + estrogen-dominated bodies

follicular growth (in + direct mechs.)

granulosa cell maintenance

initiate puberty

non-repro. functs. (sexual response + behavior)

estrogens in testosterone-dominant bodies

in many tiss. T not funct. but must be converted to E2 or DHT to func.

concentrates sperm in fluids (fertility)

masculinization of brain that controls sex behavior (mice), courtship, aggression

normal long bone epiphyseal plate fusion

cardiovasc. health (true for organisms w/ funct. ovaries)

• arteriole elasticity (not stretch but retract)

• healthy HDL/cholestserol levels

hormonal regulation

GnRH (gonadotropin-releasing H)

FSH

LH

prolactin

feedback

gonadotropin-releasing hormone (GnRH) release governed by

hypothalamic neurosecretory cells → ME → portal vein → PD

internal: nutrients; species

external: photoperiod in seasonal breeders

released in pulsate manner - change freq. (vs. amplitude)

direct control unknown

follicle stimulating hormone (FSH) hormonal regulation

pars distalis of adenohypophysis

stims spermatogenesis

synergistic w/ andorgens

targets Sertoli cells of testis

• stims. ABP

• through GPCR → cAMP → genomic actions

leutinizing hormone (LH) hormonal regulation

of pars distalis of adenohypophysis

targets leydig cells

• stims androgen prod.

prolactin hormonal regulation

of pars distalis of adenohypophysis

targets leydig cells

• inc. LH receptor expression

hormonal regulation androgens neg. affect

hypothalamus: GnRH

pituitary: LH, FSH

hormonal regulation inhibin

peptide H

stim. by FSH

of sertoli cells

targets adenohypophysis

• blocks FSH release

• androgen prod. w/out spermatogenesis