Male Reproductive System Flashcards
what does the male reproductive system consist of?
in essence, a pair of male gonads and other associated structures that produce sperm and transport it to the outside, as close to an oocyte as possible (the female cervix)- this is dependent on a physiologically functioning penis which undergoes an erectile process. there are accessory glands involved in the production of ejaculate.
sperm are produced in the seminiferous tubules in the testes held outside outside the body in a scrotal sacker cooling purposes. produced sperm collect in a lengthy coiled tube called the epididymis. a seminal vesicle, one on each side, close to the prostate gland empties into the ejactulatory duct, into the urethra. prostatic ducts from the prostate empty into the urethra. many urethral glands secreted mucus into the urethra, and there are 2 bulbo-urethral glands that add mucous to the ejaculate. the urethra extends along the penis and ends in the glans.
describe sperm production
seminiferous tubules contain very many germinal epithelial cells called spermatogonia. these proliferate to replenish themselves and eventually become sperm. the spermatogonia migrate amongst the sertoli cells and become spermatids with 22 chromosomes and either a X or Y. spermatids are embedded into the sertoli and are nurtured by them.
within the interstitial spaces, they are also Leydig cells that produce testosterone, stimulated to do so by LH. The leydig cells produce testosterone which is essential for maturation of sperm cells into spermatozoa. serteli cells are stimulated by FSH. they also secrete oestrogen under the influence of FSH that is also essential to maturation of sperm. growth hormone is also required for cell devision of spermatogonia and is essential to sperm production.
describe endocrinological control of spermatogenesis
production of sperm is driven by combined action of FSH on the sertoli and LH on the Leydig cells. product of the leydig cell is testosterone which inhibits its own production by negative feedback at the anterior pituitary and also the hypothalamus to inhibit release of gandotropin releasing hormone. FSJ causes the sertoli cells to produce inhibin which also acts by negative feedback on the anterior pituitary and on the hypothalamus. Inhibin acts to prevent spermatogenesis from occurring spontaneously.
what are effects of testosterone in the development of the secondary sexual characteristics and general development into adulthood
during puberty testosterone secretion causes the penis, scrotum and testes to enlarge in size. in addition, secondary sexual characteristics emerge.
hair growth on the face, pubis and sometimes chest
later on testosterone causes pattern baldness, provided there is genetic predisposition
enlargement of the larynx and the voice “breaks”
sometimes acne
muscle formation increases
calcium retention and increased bone thickness
increase in basal metabolic rate
red cell count increases
extracellular and blood volume increases as testosterone resembles aldosterone
describe the male sexual act
combination of stimulation of the glans penis and psychic stimulation causes erection, with the former causing impulses to be conveyed via the pudendal nerve to the sacral part of the spine and undefined parts of the brain.
such stimulation causes parasympathetic nerves from the sacral portion of the spinal nerve to secrete nitric oxide which causes relaxation of arteries in the penis. blood accumulates in the corpus cavernosum and the corpus spongiosum. these are large, usually empty blood sinuses that cause erection by filling but also because venous outflow is also inhibited. the high pressure causes ballooning of the tissue such that it becomes harder than normal and is elongated.
during erection the urethral and bulb-urethral glands secrete mucus to provide some lubrication in the vagina, but most lubrication comes from the woman.
with a satisfactory amount of stimulation reflex centres in lumbar segments 1 & 2 emit a sympathetic impulse that causes emission, the prelude to ejaculation. evacuation occurs with connotation of the vas deferens and expulsion of some prostatic fluid into the urethra. vigorous smooth muscle contractions increase the pressure in the urethra and the sperm is propelled into the exterior
describe fertilisation
sperm from the vas deferens, seminal vesicle fluid, and peostate fluid are ejaculated, seminal vesicle fluid last of all to flush sperm out. sperm have about 24-48 hours “shelf life”. once inside the vagina , uterine fluid causes capacitation of the sperm and this includes making sperm more calcium permeable so that the flagellum become very active, the sperm travels to the ovum and penetrates the zona pellucidia after combining with a receptor protein. it is thought that the successful sperm depolarises the ovum membrane and makes the entry of second spermatozoon no longer possible.
