The urinary system is composed of the kidneys,
ureters, bladder and urethra.
Blood from the heart travels down the aorta
where it enters the kidney via the renal arteries.
The kidney acts as a filter and regulator,
removing waste products (urea) and balancing
glucose, electrolytes (salt, potassium and other
minerals) and water levels in the blood.
Urine from the kidney flows through the ureter
to the bladder, where is leaves the body via the
5. Urine is formed in the nephrons through a
complex three-step process: glomerular filtration,
tubular re-absorption, and tubular secretion.
The various substances which are normally
filtered by the glomerulus, reabsorbed by the
tubules, and excreted in the urine include:
sodium, chloride, bicarbonate, potassium,
glucose, urea, creatinine, and uric acid.
6. Within the tubule, some of these substances are
selectively reabsorbed into the blood.
Some substances, such as glucose, are completely
reabsorbed in the tubule and normally do not appear
Filtrate becomes concentrated in the distal tubule and
collecting ducts under the influence of antidiuretic
hormone (ADH) and becomes urine.
9. FUNCTIONS OF THE KIDNEYS
To remove waste products
Remove drugs from the body
Balance the body's fluids
Formation of urine
Release hormones that regulate blood pressure
Control the production of red blood cells.
10. THE URETERS
-consist of three layers of tissue:
An outer covering of fibrous tissue, continuous with
the fibrous capsule of the kidney
A middle muscular layer consisting of interlacing
smooth muscle fibres that form a syncytium spiralling
round the ureter, some in clockwise and some in
anticlockwise directions and an additional outer
longitudinal layer in the lower third
An inner layer, the mucosa, lined with transitional
11. Each ureter is a small tube, about 25 cm long that
carries urine from the renal pelvis to the urinary
bladder. It descends from the renal pelvis, along the
posterior abdominal wall, behind the parietal
peritoneum, and enters the urinary bladder on the
posterior inferior surface. The
wall of the ureter consists of three layers ,These are:
The outer layer
The middle layer
The inner layer.
12. The outer layer or the fibrous coat is a supporting layer made
of fibrous connective tissue.
The middle layer, the muscular coat, consists of inner circular
and outer longitudinal smooth muscle. The main function of
this layer is peristalsis to propel the urine.
The inner layer, the mucosa, is transitional epithelium that is
continuous with the lining of the renal pelvis and the urinary
bladder. This layer secretes mucus which coats and protects the
surface of the cells.
13. Functions of the ureter
To propel the urine from the kidneys into the bladder
by peristaltic contraction of the smooth muscle layer.
Peristaltic waves occur several times per minute,
increasing in frequency with the volume of urine
produced, and send little spurts of urine into the
14. THE URINARY BLADDER
The bladder is roughly pear-shaped, but becomes
more oval as it fills with urine. It has anterior, superior
and posterior surfaces. The size and shape of the
urinary bladder varies with the amount of urine it
contains and with pressure it receives from
The bladder is located in the pelvic cavity, posterior to
the symphysis pubis, and below the parietal
peritoneum. The urinary bladder serves as a temporary
storage reservoir for urine.
The posterior surface is the base. The bladder opens
15. The peritoneum covers only the superior surface before it turns
upwards as the parietal
peritoneum, lining the anterior abdominal wall. Posteriorly it
surrounds the uterus in the
female and the rectum in the male.
The inner lining of the urinary bladder is a mucous membrane of
transitional epithelium that
is continuous with that in the ureters. When the bladder is
empty, the mucosa has numerous
folds called rugae. The rugae and transitional epithelium allow
the bladder to expand as it
16. The second layer in the walls is the submucosa that
supports the mucous membrane. It is
composed of connective tissue with elastic fibres.
The next layer is the muscularis, which is composed of
smooth muscle. The smooth muscle
fibres are interwoven in all directions and collectively these
are called the detrusor muscle.
Contraction of this muscle expels urine from the bladder.
On the superior surface, the outer
layer of the bladder wall is parietal peritoneum. In all other
regions, the outer layer is fibrous
There is a triangular area, called the trigone, which is formed by three openings
in the floor of
the urinary bladder. Two of the openings are from the ureters and form the
base of the
trigone. Small flaps of mucosa cover these openings and act as valves that allow
enter the bladder but prevent it from backing up from the bladder into the
ureters. The third
opening, at the apex of the trigone, is the opening into the urethra. A band of
muscle encircles this opening to form the internal urethral sphincter. Figure
150 shows the a
section of the bladder with the trigone.
18. The Urethra
Structure and Function
The urethra is a canal extending from the neck of the bladder to the exterior, at
urethral orifice. It is the final passageway for the flow of urine. Its length differs
in the male
and in the female.
The urethra is a thin-walled tube that conveys urine from the floor of the
urinary bladder to
the outside. The opening to the outside is the external urethral orifice. The
mucosal lining of
the urethra is transitional epithelium. The wall also contains smooth muscle
fibres and is
supported by connective tissue. The internal urethral sphincter surrounds the
the urethra, where it leaves the urinary bladder
19. This sphincter is a smooth (involuntary)
muscle. Another sphincter, the external urethral
sphincter, is a skeletal (voluntary) muscle
that encircles the urethra where it goes through the
pelvic floor. These two sphincters control
the flow of urine through the urethra.
In females, the urethra is short, only 3 to 4 cm (about
1.5 inches) long. The external urethral
orifice opens to the outside just anterior to the
opening for the vagina.
20. The male urethra is associated with the urinary and
the reproductive systems. The urethra is much longer,
about 20 cm (7 to 8 inches) in length, and transports
both urine and semen. The first part, next to the
urinary bladder, passes through the prostate gland and
is called the prostatic urethra.
21. The second part, a short region that penetrates the
pelvic floor and enters the penis, is called the
membranous urethra. The third part, the spongy
urethra, is the longest region. This portion of the
urethra extends the entire length of the penis, and the
external urethral orifice opens to the outside at the tip
of the penis.
22. Physiology of Micturition
The urinary bladder acts as a reservoir for urine.
When 300 to 400 ml of urine have accumulated,
afferent autonomic nerve fibres in the bladder wall
which are sensitive to stretch are stimulated. In the
infant this initiates a spinal reflex action and
23. Micturition occurs when autonomic efferent fibres
convey impulses to the bladder causing contraction of
the detrusor muscle and relaxation of the internal
When the nervous system is fully developed the
micturition reflex is stimulated but sensory impulses
pass upwards to the brain and there is an awareness of
the desire to pass urine.
24. Investigations And Procedures
done in the urinary system
Urine examination: M/C/S and urinalysis
Renal function tests: blood urea and nitrogen (BUN),
urea and creatinine and electrolyte tests.
This is an X- ray examination, which visualises the
urinary tract after IV injection of the contrast media
25. Retrograde pyelogram
This is an x- ray of the urinary tract which is taken
after injection of contrast material into kidneys
cystoscope is inserted and ureteral catheters are
inserted through it into renal pelvis
In this procedure, contrast media is injected into the
bladder via cystoscope or catheter
26. Digital rectal examination
This is visualization of the internal structure of the
bladder by use of an endoscope
ultrasound enables visualization of the various organs
of urinary system