Week 12: Male Reproductive System Flashcards
what is the advantage to sexual reproduction?
genetic diversity
how do we get genetic diversity?
by mixing gene pools
- and getting genetic diversity gives us species more likely to survive
development of testes in utero starts with the testis up near?
the kidneys
the testes need to gradually move down and eventually move into?
the scrotum
what is that process called?
Descent of Testes
The testes are the most important organ of the male reproductive system because?
they produce the sperm
why are they not up near your lungs and surrounded by bone?
temperature control
to get optimal sperm production and healthy sperm that can swim and fertilize, the testes have to actually be at a temp that is?
slightly below body temp
- we wind up with very important reproductive organs that are not getting the same protection as other organs we consider to be very important in survival
as time passes, testes descend into the scrotum and the testes are connected to structures in the pelvic cavity by a group of structures called?
spermatic cords
one spermatic cord entering each cavity on each side of scrotum and in the spermatic cords we have?
artery, vein, lymphatics, nerve, and vas deferens (ductis deferens)
- all these things together are called the spermatic cords
they pass through a canal called?
inguinal canal
having the testis pass through that inguinal canal leaves a weak spot called?
inguinal hernia
if we get a tear in the inguinal canal, what happens?
intestine can get stuck or testis can get stuck
what are the layers of the scrotum?
skin on the outside, just deep to the skin we have some muscles (dartos muscle and cremaster muscle)
the dartos muscle is responsible for?
wrinkling the skin of the scrotum
why would you want to wrinkle the scrotum skin?
to be able to decrease surface area and less likely to lose heat
- part of temp regulation
the cremaster muscle has more of a protective function
- when the cremaster muscle contracts, the testis itself gets lifted up and the cremaster muscle will contract to bring testes closer to the body if temp is too low
- it will also contract if theres some sort of threat of injury to the testes.
the closer the testes are to the trunk of the body, the less..
likely they are to get injured
the testes are sitting in a pouch (each testis has its own pouch) and the testes move in that pouch and so we’re gonna have a serous membrane that helps?
line the scrotum and also cover the testis
what is that membrane called?
tunica vaginalis
where is the parietal and visceral layers of the tunica vaginalis located?
- the parietal layer is deep to the cremaster muscle
- the visceral layer sits just outside of the capsule around the testes
both of these layers produce a small amount of?
fluid that makes the testes in the scrotum a little more slippery
- decrease likelihood of damage from friction and if the testis is getting compressed, it slides more easily and it can hopefully slide out of the way of injury
just deep to the visceral layer of the tunica vaginalis, we have a structure called?
tunica albuginea
- a dense white connective tissue and it not only surrounds the testis but it also sends septa into the testis to divide into lobules
each testis is made up of somewhere around 200 lobules and in each lobule, we have somewhere around
1-3 seminferous tubules
the seminferous tubules are where the sperm are going to be?
produced and matured
how long is each seminferous tubule?
about 2 ft long
- 3 seminiferous tubule per lobule = 6 ft of seminferous tubules
- times 200 lobules=1200 ft of seminferous tubules
- times 2 testes = 2400 ft of seminferous tubules
why do we have 2400 ft of seminferous tubules ?
necessary for sperm production and sperm maturation
each of the seminferous tubules is gonna connect to a structure called?
rete testis
eventually the sperm will move from the seminferous tubules into the rete testis and then attached to the testis is the epididymis. the epididymis connects the rete testis through the efferent ductule (small tubules)
in between the seminferous tubules, there are another group of cells called?
interstitial cells AKA Leydig cells
- Leydig cells make testosterone
- interstitial cells are in between the tubules
what are the functions of testes?
- produce testosterone
- endocrine organ
- spermatogenesis (sperm production)
things about sperm
- have flagella (only cells in a human that have flagella)
- carry genetic material
- develop in stages
our cells, except the cels we use for reproduction, are diploid which means?
we have two copies of each chromosome. not necessarily identical
sexual reproduction means?
that mom and dad has to contribute DNA but if mom has diploid cells and dad has diploid cells and we put them together and now we have copies of everything and we are making smtn not human.
in order for sexual reproduction to produce humans, what do we have to do?
divide DNA so we get one copy of each chromosome in each sperm
review of mitosis and meiosis
- we have a cell thats duplicating its DNA, synthesis stage comes before mitosis. we’re gonna divide the DNA into two sets and get 2 cells (both cells will be diploid).
- what happens in meiosis is we get two division. first division (Meiosis I) looks just like mitosis. I replicate DNA and now have 4 copies of every chromosome and im gonna split into two diploid cells.
- next im going to divide the DNA again but im not goina to replicate it first. so each diploid cells divide and gives me two cells w one copy of everything. when we’re talking about producing sperm, my diploid cell can give me 4 haploid sperm.
- if we dont replicate the DNA again and just divide, we can’t get 2 copies of everything in the cell.
Meiosis is the first part of spermatogenesis:
taking diploid cells and making haploid cells from them. if we can’t do that, the next stage does us no good.
what is the second part of spermatogenesis called
spermiogenesis
- the diploid cells that give rise to sperm is round, they don’t have flagella and pointy little heads. we have
- what we have to do in spermiogenesis is take a round haploid cell and change its shape so it can function like a sperm. it can become a DNA delivery device that swims effectively and fertilizes effectively
the wall that makes up the seminferous tubules
Substentcular cells AKA nurse cells or sertoli cells
What do sertoli cells do
- are physically supporting developing sperm cells
- connect to each other with tight junctions that makes a barrier between the diploid spermatogonia and that haploid various stages of developing sperm called blood testis barrier
what is spermatogonia?
round diploid cells, stem cells for sperm development
how does the blood testis barrier help?
for some reason, the surface antigens ion a spermatogonia are recognized by a males body as self but surface antigens on haploid cells are different and the males immune system recognizes those as invader and without the blood testis barrier, a males immune system will attack developing sperm and they wind up with autoimmune infertility bc their own immune system is killing off their sperm and so the blood testis barrier limits that
while the last stages of spermiogenesis are going on, those cells that look like sperm at the luminal edge of cells, are attached to?
the sertoli cells
- each of these individual sperm has a parking place in the luminal end of cell and they stay there until theyve completed spermiogenesis and then theyre released and move into the lumen and then they’re free
sertoli cells secrete a hormone called?
inhibin
- act on anterior pituitary gland and decrease release of a hormone called follicle stimulating hormone (FSH)
FSH stimulates?
spermatogenesis
how does this negative feedback system work?
when the seminiferous tubules are fully occupied, the sertoli cells release inhibin which decrease FSH and will turn down spermatogenesis for a while, while the sertoli cells that are fully occupied support the end of spermatogenesis. as the seminiferous tubules get less occupied, the inhibin levels go down letting the FSH go up and we can increase level of spermatogenesis again
- good ole fashion negative feedback
sertoli cells make another hormone called?
Mullerian-Inhibiting Factor (MIF)
early in utero development, whether the fetus is male or female, early on, they develop both reproductive duct systems and the female repro system is made up of?
Mullerian ducts and so the sertoli cells release MIF and thats gonna block further development of the female duct system for reproduction
another thing made by sertoli cells that is not a hormone is a protein called?
Androgen binding protein (ABP)
- androgen is the name of the class of male repro hormones and steroids related to testosterone
what kind of hormone/category other than reproductive is testosterone
steroid
- hydrophobic, they can drift in and out wherever they want as long as there is a conc gradient
what is the problem? to finish spermiogenesis, we need a high conc of testosterone not in the blood but in?
the lumen of the seminiferous tubules and so the sertoli cells make ABP and release it into the lumen, testosterone diffuses in and its bound by an ABP and now its hydrophilic and can’t leave
ABP is a way to trap?
testosterone in the seminiferous tubules so we have enough testosterone in there to finish spermiogenesis
list of functions of seminiferous tubules
- physically and nutritionally supporting developing sperm
- blood testis barrier
- several things secreted by sertoli cells
to get sperm from a round thing without a tail and no way to swim to a mature sperm
- first start growing a flagella, make a whole much of microtubules
- golgi apparatus diffuse together to become one packet and become the acrosome
- develop digestive enzymes that will help a sperm trying to fertilize its egg and make its way through the wall of the egg and protective barrier associated w it
- organize mitochondria in the cell so theyre in the place where we need that energy which is at the base of the flagella bc that makes everything move
- all the mitochondria get moved to this area and finally get rid of some cytoplasm
a sperm is meant to be?
a delivery device for DNA and so its not built for long term survival without assistance
- we’re gonna make this as hydrodynamic as it can be so it can effectively deliver sperm
anatomy of sperm and what it consists of
in a sperm, the portion that actually has nucleus and DNA and the acrosome, thats the head. the midpiece and neck together have all the mitochondria and have a pair of centrioles (centrioles are necessary for mitosis, when sperm fertilizes egg, once a nuclei fuse, the next thing that happens is mitosis so we need to have centrioles from both mom and dad)
how long is the head and tail?
the head is 5 microns long, the tail is 55 microns long
when sperm fertilizes an egg, the nucleus and centrioles go in but the midpiece and tail don’t go in the egg which means?
no mitochondrial DNA from dad
- all mitochondria you have come from your mother
- we’re starting to use maternal mitochondrial DNA as a way to trace ancestry
the epididymis is the first part of the ?
reproductive duct system in males
- comma shaped
- little part that connects to the next duct, vas deferens, is the tail
vas deferens looks smooth and the epididymis looks?
convoluted
- so tightly coiled, it is 6 meters long
- all abt surface area
- just as long as the small intestine
the epididymis can store sperm for how long?
1-3 weeks
- without a loss of fertility
how is this possible?
epididymis makes a small amount fluid and theres nutrients in that fluid that help the sperm keep alive
sperm in the epididymis are?
fully matured, have high motility, swim very well, but cannot fertilize yet
- have to go through a process called capacitation
what is capacitation?
2 step process
1. when sperm gets exposed to secretions from seminal vesicles (one of the accessory glands from male repro syst)
2. sperm get exposed from secretions of the female reproductive tract (vaginal fluids)
without going through the two step process of capacitation, you have sperm that can?
swim, find an egg, but they can’t fertilize it
Vas deferens AKA Ductud deferens
all of a sudden we make transition from epididymis which is very convoluted to the vas deferens which have a ?
thicker wall and NOT convoluted
surface area is not as much of a factor in the job of the?
vas deferens
First step to vasectomy
you can palpate the vas deferens in the scrotal sac
- you find it, snip it, fold the ends over
three layers of smooth muscle in the Vas deferens:
middle layer is circular, the inner and outer are longitudinal
you will move sperm through the vas deferens by?
peristalsis
- much more rapid peristalsis than in the SI for exampler
what happens in a vasectomy?
they will find vas deferens in the scrotal sac and make a small incision in the sac, cut the vas deferens and fold the ends and sew them over
