MNSR 36 - Human Reproduction: embryological origins; Male System Flashcards
reproduction
for species to survive they must multiply and produce new individuals to replace those lost to predators, parasites and old age
implies transfer of genetic material from one partner to another
hermaphroditism
possessing both male and female sex organs in the same individual
examples of organism that feature aphroditism
lower invertebrates e.g. Platyhelminthes (i.e. flat worms),
parthenogenesis
reproduction from a female gamete without fertilisation by a male gamete
unfertilized egg develops to maturity via asexual reproduction
terrestrial tetrapods
repitles, birds and mammals - developed a mechanism of internal fertilization as they live in a terrestrial environment
oviparous
laying eggs
vviparous
producing live young
gonads
reproductive organs e.g. testis and ovaries
where do both the testis and ovary develop from
mesodermal genital ridge of the embryo
where is mesodermal genital ridge
medial to the mesonephros - nearby developing intermediate kidney
____ or ___are gradually taken over for reproductive purposes in males
- mesonephric
2. wolffian ducts
1.___ or2. ___ are taken over for reproduction in
females
1.paramesonephric or Mullerian
in males how are sperm conducted to the outside
in all male vertebrates, sperm are conducted to the outside via the closed tubes of the excretory system
in females how do ova shed coelom
ova are shed into the coelom and then pass into a special tube, the fallopian tube or Müllerian duct
where are the testes
upper lumbar region of coelomic cavity
how does the position of scrotal sacs change through fetal development
However, in most mammals the testes descend into scrotal sacs during foetal development passing through the inguinal canal
what also descends with the testes in fetal development
with the testes descends the sperm duct,
gubernaculum
testes and sperm duct with their nerve and blood supply and a fold of mesentery called the gubernaculum
how many seminiferous tubules are in each testis
1,000 highly coiled seminiferous tubules
function of seminiferous tubules
are open at both ends and produce spermatozoa into the rete testis which acts as a reservoir
vasa efferentia
A series of fine ciliated tubes the vasa efferentia (or efferent ducts), that connect the rete testis with the epididymis
epididymus
a single long convoluted duct lined with pseudostratified columnar epithelium with stereocilia (microvilli);
how are immobilised spermatoza transported
transported through the epididymis by peristalsis of the layer of smooth muscle in the wall
function of epididymus
Functionally the epididymis is the site of sperm maturation (acquire motility and ability to fertilize)
how does the spermatoza transported prior to ejaculation
epididymis (by peristalsis of the smooth muscle)
the vas deferens
bladder
prostate gland
urethra
in males the urethra is a common urino-genital duct.
vas deferens
a muscular tube, which brings them back into the abdominal cavity;
2 cavernous bodies in penis
corpora cavernosa - outer
corpus spongiosum - inner
surround the urethra
how are blood supplied from arteries
Essentially helicine arteries supplying the cavernous bodies dilate filling the cavernosa with blood while at the same time the veins are compressed
pH of semen
7.5
average volume of semen per ejaculation
3.5ml
normal amount of spermatoza per ml
120 million spermatazoa/ml
sperm count of infertile men
less than 20 million spermatozoa
accessory sex glands of male reproductive system
seminal vesicles
prostate gland
cowpers glands
function of seminal vesical
produce viscous fluid into vas deferens
makes up to 60% of semen volume
provides fructose for ATP production and enables sperm to swim
function of prostate gland
produces a thin milky alkaline fluid containing citric acid (used for ATP production by sperm)
acid phosphatase neutralise acidity of vagina which has pH of 3.5
function of cowpers gland/bulbourethral
(bulbo-urethral) produces a viscous mucous secretion for lubrication
path of secretions from accessory glands
Cowper’s secretions -> prostatic fluid –> spermatozoa –>seminal vesicle secretions
how does consistency change and what enzyme contributes to this change
the semen initially coagulates into a gelatinous mass and then dissolves over the next 15 to 20 minutes;
this is helped by a prostatic proenzyme
histology of testis - seminiferous tubules
germinal epithelium - undergoes meiosis those cells sit on a
basement membrane
- outside that membrane have fibroelastic connectice tissue and myoid cells that are muscle like cells can contract
describe cells resting on basement membrane
type A1 spermatogonia - divide by mitosis to make type B spermatogonia
diploid cells
Type B spermatagonia divide to make..
these type B spermatogonia now undergo a series of mitotic divisions to produce primary spermatocytes (2N);
primary spermatocytes (2N); divide
and these divide by meiosis (‘SPERMATOGENESIS’) to produce two secondary Spermatocytes (N);
why are secondary spermatocytes rarely seen
they rapidly undergo the second meiotic division to produce the haploid spermatids (N).
these by a process of SPERMIOGENESIS differentiate into spermatozoa, which are stored in the epididymis;
what hormone controls process of spermatogenesis
FSH from pituitary gland
leydig cells
between the seminiferous tubules are the Leydig cells, which secrete testosterone
testicular descent
the descent of the testis but the scrotal sac is high up or inguinal canal or abdomen
This is especially serious where the spermatic cord is not long enough to travel the complete journey
can lead to malignancy if elft intreated
testicular malignancy
Malignancy may quickly spread to Inguinal nodes
Males should examine themselves regularly as do women their breasts
inguinal hernia
The internal structures (intestines or fat) are forced out through the weakness in the abdominal wall (inguinal canal)
what gender is inguinal hernia more common and why
This is more common in males as the canal is larger
main cause of erectile dysfunction
insufficient release of nitric oxide which relaxes the smooth muscle of the penile arterioles and erectile tissue.
