00:00
Let's briefly now look
at the ureter, shown
here on the right hand side. It's a muscular
tube. It passes the urine down to
the bladder. It's lined by what we call a
transitional epithelium or a urothelium.
00:18
And this persist this type of epithelium
all the way down through the bladder, and
to some degree, through the urethra. It's
called transitional epithelium because
it changes its appearance. When the
bladder and the ureter is distended
during flow of the urine, the epithelium
changes its shape. And because of that,
it's called transitional, and I'll
describe that in a moment. But it's just a
muscular tube. Here is a section of the
bladder on the right-hand side. Have a
look at the diagram of the male bladder indicated
here. It's a bag for storing urine.
00:59
And on the right-hand side, you see
sections through the mucosa of the
bladder when the bladder is empty, and
the mucosa and the epithelial cells, in
particular, are very thick. It's a very thick
stratified layer. On the left-hand side
is this epithelium of the bladder, and
it's typical of the epithelium of the
ureter as well, stratified epithelium.
Notice on the surface of these cells,
there are some eosinophilic stains.
These are plaques.
01:33
And what you see here on the right-hand
side is the bladder when it's
distended, and the surface cells flattened
out from the more cuboidal shape
that you see at the surface on the left-hand
side in more a relaxed bladder. Hence the
name transitional epithelium, but also gets
the name urothelium. Those plaques are very,
very important, because what they do is they
prevent water and salts going back, out
of the bladder back into the body. They
form a seal and they're impermeable,
which is very important when you're storing
rather toxic substances and
components of the blood you feel that you
don't want in the body. You want
to eliminate in the urine. And finally, the male
and female urethra. In the
female, it's short. The urothelium persists
for a while and then it changes
to a non-keratinized stratified squamous
epithelium. In the male, the urethra is
long because there are three different
parts, the prostatic urethra, the
membranous urethra, and the penile urethra.
There's a little star next to the
urethra, the membranous urethra in the
male because that's where urothelium changes
from typical transitional epithelium
I've described to stratified squamous
epithelium throughout the penis and then
beyond towards the skin. Sometimes in
the urethras you find mucus secreting
glands, which are probably
there just to protect the epithelium
from perhaps an acidic
urine.
03:21
So let's just summarize now what the
functions of these components are.
03:28
The kidney has a very important structure
of the nephron, which consists of the
glomerulus filtration apparatus. And all
the tubules that you will learn in
physiology have a very important role in
filtering our blood, getting a filtrate
plasma based solution, and it then gets
rid of products that we don't want to
retain, or excessive products, and passes
it into the urine. The ureter conveys
that urine to the bladder, the bladder stores
that urine and make sure things don't leak
back into the system, into the body.
And the urethra is the tube whereby we
eliminate urine from the bladder in both
the male and the female. So I hope you
now understand histology of the major
organs of the urinary system. And
thank you very much for listening to this lecture.