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The Urinary System
adipose
bladder
capacity
excretes
folds
hilus
kidneys
tubes
ureters
urethra
urine
waste products
The urinary system is the system which (1) the largest part of the (2) of the body.
It consists of the (3), right and left, the (4), a tube from each kidney which conveys
the urine to the (5), the (6), a tube that leads from the bladder, along which the
urine is passed out of the body.
The kidneys («renes» — Latin) are placed one on each side in the lumbar region
of the spine, on the posterior abdominal wall, at the level of the twelfth thoracic and
first-second lumbar vertebrae. A kidney weighs about 150 grams and is covered
by membranes. The connective tissue membrane which directly adheres to the
kidney is called the fibrous capsule. This capsule is surrounded by perirenal fat and
is called the (7) capsule. The kidneys are two bean-shaped organs. The kidneys
contain one million small (8), which have to excrete products of metabolism and con-
trol the concentrations of most of the constituents of body fluids. These small tubules
make up the parenchyma of the kidney. They are very fine and may be of various shape.
Since dissolved wastes may be excreted by diffusion through the various cell membranes
there is little evidence that such excretion occurs.
The inner margin of the kidney is known as the (9). At the hilus the ureter which
conveys urine is a tube about 30 cm long. When the ureter leaves the hilus it
descends along the posterior abdominal wall into the cavity of the pelvis where it
perforates the wall of the bladder and opens into its cavity. As the muscular coat of
the ureter contracts it has to perform peristaltic movements.
The bladder is a reservoir for (10). It is situated in the cavity of the pelvis. The
bladder has three parts: the superior part or apex, the middle part or body, and the
inferior part or fundus. The wall of the bladder consists of three coatings —
mucous, muscular and connective tissue. The mucous membrane of the bladder
forms numerous (11). If the bladder fills, the folds of the mucous coat will straighten
out. The muscular coat consists of three layers of smooth muscles which are able to
extend in different directions. It should be known that the (12) of the bladder of an
adult is about 350—500 ml.