URINARY
SYSTEM
URINARY SYTEM
The urinary system consists of all organs involved in the
formation and release of urine.
It includes the kidney, ureters, bladder and urethra.
The kidneys are bean shaped organs which help the body
produce urine to get rid of unwanted waste substances.
When urine is formed, tubes called ureters transport it to the
urinary bladder, where it is stored and exerted via the
urethra.
The kidneys are also important in controlling our blood
pressure and producing red blood cells.
KIDNEY
Kidney
The kidneys are large, bean-shaped organs towards the back of the abdomen (belly). They
lie behind a protective sheet of tissue within the abdomen. The kidneys perform many vital
functions which are important in everyday life. A special system of tubes within the kidneys
allow substances such as sodium and chloride to be filtered. On the side of the kidney with the
smaller curve is an opening called the hilum, where blood vessels, nerves, and the ureters
enter the kidney. The kidney can be divided into two distinct regions. There is an outer red-
brown part called cortex and inner lighter colored part called medulla. The cortex is made up of
special units called corpuscles, nephrons, and a system of straight and curvy collecting tubules
supplied by many blood vessels. In the outer part of the kidney, there are many nephrons
which act as filtering units. Each nephron is supplied by a ball of small blood vessels, called
glomeruli. The inner part of the kidney called the medulla is a continuation of the specialized
nephrons in the kidney. A small blood vessels network called the vasa recta supplies the
medulla. Each kidney is supplied by the renal arteries, which give off many smaller branches to
the surrounding parts of the kidney. Renal veins drain the kidney.
URETERS
URETERS
The ureters carry urine to the bladder; they are 25-
30 cm long tubes lined with smooth muscles. The
muscular tissue helps force urine downwards. The
ureters enter the bladder at an angle, so urine doesn’t
flow up the wrong way. On one end of the ureters is a
funnel-shaped expansion, called the renal pelvis, where
urine collects.
BLADDER
Bladder
The bladder is a pyramid-shaped organ which sits in the pelvis. The
main function of the bladder is to store urine and, under the appropriate
signals, release it into a tube which carries the urine out of the body.
Normally, the bladder can hold up to 500 mL of urine. The bladder has three
openings: two for the ureters and one for the urethra. The bladder consists of
smooth muscles. The main muscle of the urethra forms a ring-like muscle that
controls the passage of urine. When we want to urinate, stretch receptors in
the bladder are activated, which send signals to our brain and tell us that the
bladder is full. The ring-like muscle relaxes and the detrusor muscle contracts,
allowing urine to flow. The blood supply of the bladder is from many blood
vessels. Some of these blood vessels are named: the vesical arteries, the
obturator, uterine, gluteal and vaginal arteries.
URETHRA
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URETHRA
The male urethra is 18-20 cm long, running from the bladder
to the tip of the penis. The male urethra is supplied by the inferior
vesical and middle rectal arteries. The veins follow these blood
vessels. The nerve supply is via the pudendal nerve.
The female urethra is 4-6 cm long and 6 mm wide. It is a tube
running from the bladder neck and opening into an external hole
located at the top of the vaginal opening. As the female urethra
is shorter than the male urethra, it is more likely to get infections
from bacteria in the vagina. The female urethra is supplied by
the internal pudendal and vaginal arteries.
