E3 Male reproductive system Flashcards
function of male reproductive tract
- production of sperm (spermatogenesis)
- delivery of sperm to the female
primary male reproductive organ
testes
secondary male reproductive organs, also state their function
support the function of the testes
penis
scrotum
epididymis
vas deferens
seminal vesicles
prostate gland
what are the testes?
- male gonads
- 250-300 compartments each containing clusters of Leydig and Sertoli cells
what are the testes responsible for?
- sperm production
- development of sperm
- spermatogenesis
- delivery of sperm to female
where are sperm stored after they have fully developed?
- when fully developed they are deposited into the lumen of the epididymis
- they then move down the reproductive tract when it is time for delivery to the female
describe spermatogenesis
- production of male gametes from primordial germ cell
- original cells undergo division and development and post developmental modifications to produce specialised sperm cells
- involves seminiferous tubules
- cells produce and mature the sperm
what cells produce and mature the sperm in spermatogenesis?
Sertoli cells
what cells are responsible for the production of testosterone?
Leydig cells
where are the Leydig cells positioned?
interstitially and between Sertoli cells
state some cells and features of the testes
- Leydig cells
- Sertoli cells
- smooth muscle
- blood-testis barrier
location and function of Leydig cells
- interstitial cells found in the gaps of the seminiferous tubules
- secrete testosterone
structure and basic function of Sertoli cells
- epithelial cells
- support sperm development and maturation
- arranged in circular arrangement to create the seminiferous tubule and a hollow lumen which sperm are then released into when fully mature
function of smooth muscle in testes
- peristalsis
- propel sperm towards egg
structure and function of blood-testis barrier
- prevents sperm getting into the general circulation
- tight junctions
- luminal compartment and basal compartment so nothing produced in testes can leak into circulation
in depth functions of Sertoli cells
- support sperm development by providing nutrients in response to testosterone secreted by Leydig cells
- secrete luminal fluid in which sperm develop
- secrete androgen-binding protein into lumen of seminiferous tubules
- target cells for testosterone and FSH
- secrete inhibit (hormone of negative feedback loop for FSH)
- secrete Müllerian inhibiting substance (MIS) in foetal life
- form blood-testis barrier
explain the function of Sertoli cells: secrete androgen-binding protein into lumen of seminiferous tubules
- acts as an androgen buffer
- facilitate production and delivery of sperm into the epididymis
- helps maintain steady androgens in lumen
describe the conversion of spermatid to sperm
- migration and movement of cell from basal membrane of Sertoli cells down seminiferous tubule into inner lumen
- differentiation gives the sperm the structure for their function
what is the male copulatory organ?
- penis
- penetrates vagina and deposits sperm
describe erection and ejaculation
- during sexual arousal, penis undergoes erection
- blood flow to penis increases to make sure it undergoes erection
- engorges erectile tissue
- penis swells and elongates
- during ejaculation, sperm ejects through urethra
describe the scrotum
- suspended beneath penis
- houses testes
what is the purpose of the scrotum?
- sperm can’t mature at normal body temp
- scrotum has thin-walled sac that makes testes a couple of degrees cooler than normal body temp
how does the scrotum regulate temperature in the cold?
dartos and cremaster muscles contract
describe the scrotal sac
- lack of fat
- excess of sweat glands
- wrinkled to increase surface area (to increase transfer of heat to ensure temperature doesn’t drop too far when it is cold)
- convoluted network of arteries and veins (allows maintenance of homeostasis temperature)
explain the difference in the penis when flaccid and erect. relate this to Viagra mode of action
- when erect, there is more blood in the tissue of the penis due to arteries being more open than veins
- Viagra operates by controlling this blood flow too control erectile dysfunction
function of seminal vesicles (accessory gland)
secrete alkaline fluid with fructose, enzymes and prostaglandins
function of prostate gland (accessory gland)
- secrete citrate and enzymes that are needed to facilitate fertilisation
- these secretions help sperm get into female reproductive system
function of bulbourethral glands (accessory glands)
- secrete viscous fluid with mucus to help lubricate semen
- this makes it rich in liquids so sperm can migrate efficiently
state the order of structures in the male reproductive tract
- sperm released into seminiferous tubule lumen when mature
- Rete Testis
- efferent ductules
(leaves testes) - epididymis
- vas deferens
what happens once the semen is in the vas deferens?
- semen and seminal fluid are transported to the ejaculatory duct
- seminal vesicles and prostate gland then add more chemicals and all the semen collects in the urethra
label the image
describe the full method of how semen is made
- sperm from testes
- stored in epididymis
- transported through vas deferens
- seminal vesicle adds: fructose, prostaglandins and seminogelin
- prostate adds: basic solution for correct pH and prostate specific antigen (PSA)
why does the seminal vesicle add fructose to semen?
provides energy that cells need to produce ATP
why does the seminal vesicle add prostaglandins to semen?
important for causing contraction of smooth muscle in the penis and female reproductive tract
why does the seminal vesicle add seminogelin to semen?
lubricates the semen liquid
why does the prostate add a basic solution to semen?
for correct pH
it neutralises the pH
what else is transported into the semen in its manufacturing process if they are present?
viruses
what are the 2 types of hormones involved in the control of male reproduction? state example of each
steroid hormones
- male androgens eg. testosterone
peptide hormones
- gonadotrophins eg. FSH, LH
- gonadotrophin releasing hormone (GnRH)
describe GnRHs?
- gonadotrophin releasing hormone
- produced by and released from hypothalamus
- targets anterior pituitary to release FSH and LH
what does FSH stand for?
follicle stimulating hormone
what does LH stand for?
luteinising hormone
what does the hypothalamus produce?
GnRH
what does the anterior pituitary produce?
LH and FSH
what does LH target?
- targets Leydig cells
- produce testosterone
what does FSH target?
- targets Sertoli cells
- initiate spermatogenesis
what are secondary male sex characteristics produced by?
- 5α dihydrotestosterone
- testosterone is converted into the above system which drives the secondary male sex characteristics
effects of testosterone before birth
- masculinises reproductive tract and external genitalia
- promotes descent of testes into scrotum (very important that the testes move out of the body before birth, if one or both do not this requires surgical correction)
what produces GnRH?
hypothalamus
what produces LH and FSH?
anterior pituitary
effects of testosterone on sex-specific tissues after birth
- promotes growth and maturation of the reproductive system at puberty
- is essential for spermatogenesis
- maintains the reproductive tract throughout adulthood (after puberty)
other reproduction-related effects of testosterone
- develops the sex drive at puberty
- controls gonadotrophin hormone secretion (testosterone is involved in a negative and positive feedback loop)
effects of testosterone on secondary sexual characteristics
- induces male pattern of hair growth (beard, pubic hair, armpits)
- causes the voice to deepen because of thickening of the vocal cords
- promotes muscle growth responsible for the male configuration
non reproductive actions of testosterone
- exerts a protein anabolic effect
- promotes bone growth at puberty
- closes the epiphyseal plates after being converted to oestrogen by aromatase
- may induce aggressive behaviour
LH target and response
- targets Leydig cells
- create testosterone and causes production and maturation of sperm
FSH target and response
- targets Sertoli cells
- release inhibin
- causes less gonadotrophin hormone to be released which causes less LH and less FSH and therefore less testosterone
what does testosterone target and what for?
- targets somatic tissue for muscle growth and seminiferous tubule
- also causes change in sex drive, behaviour and deeper voice
why is negative feedback important for testosterone?
- must be maintained at a basal level
- negative feedback keeps level constant
describe blood levels of testosterone throughout life
- fairly constant on short term basis
- prepubescent: low blood levels
- puberty and adulthood: high blood levels
describe the effects of androgens in males (testosterone in this case)
- stimulate spermatogenesis
- promote development and maintenance of secondary sex characteristics
- increase sex drive
- promote protein synthesis in skeletal muscle
- stimulate growth hormone secretion, which permits bone growth during adolescence
- promote development of male reproductive structures during embryonic life
draw a negative feedback loop for the male reproductive system
state how males are specialised for sexual reproduction
- continuous supply of millions of light gametes
- support for gamete delivery (secondary reproductive organs are involved)
- internal fertilisation delivery system
- testosterone negative feedback loop
- behaviour and secondary characteristics
