Transcript Functions of Urinary System

Urinary System
Functions of Urinary System:
1. Excretion- removing nitrogenous
wastes, certain salts and excess
water from blood.
2. Maintain acid-base balance
3. Secrete waste products in the form
of urine – remove waste from body
4. Eliminate urine from bladder
What if kidneys are not
working properly?
 Toxic wastes would
accumulate in the cells,
poisoning them
Reasons for elevated BUN
Kidneys
 Bean-shaped organs
 Located between peritoneum and the
back muscles (RETROPERITONEAL)
 Renal Pelvis- funnel shaped structure
at the beginning of the ureter
Medulla
 Inner, striated layer
 Striated cones (divisions) are renal
pyramids
 Base of each pyramid faces cortex,
while apex empties into cuplike
cavities called calyces
Cortex
 Composed of millions of microscopic
functional units called nephrons
Nephrons
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Functional unit of the kidney
Over 1 million in each kidney which
comprise 140 miles of filters and tubes
 Parts include:
1. Bowman’s capsule
2. Glomerulus
3. Proximal convoluted tubule
4. Loop of Henle
5. Distal convoluted tubule
6. Collecting tubule
Nephron structure
 Afferent arteriole – blood from renal
artery enters through this…
 Bowman’s capsule – double-walled
hollow capsule – surrounds glomerulus
 Glomerulus – knotty ball formed from
afferent arterioles finely dividing –
contains 50 separate capillaries
 Proximal convoluted tubule – twisted
tubular branch off Bowman’s capsule
Nephron structure cont’d
 Loop of Henle – proximal convoluted
tubule descends into the medulla forming
large loop
 Distal convoluted tubule – ascending limb
of Henle’s loop
 Collecting tubule – distal tubule opens
into collecting tubule
Urine Formation in the
Nephron
1- Filtration
2. Reabsorption
3- Secretion
Filtration
• First step in urine formation
• Blood from renal artery enters glomerulus
• High blood pressure in glomerulus forces
fluid (Filtrate) to move into Bowman’s
capsule (function of glomerulus is to filter
substances from the blood)
• Filtrate does not contain plasma proteins or
RBCs- they are too big
• Bowman’s capsule filters out 125cc of
fluid/min. – 7500cc/hour
• As filtrate continues through nephron, 90%
of water is reabsorbed
Reabsorption
 Water and useful substances are
reabsorbed in proximal convoluted
tubule
 If blood levels of certain substances are
high (glucose, amino acids, vitamins,
sodium) then those substances will not
be reabsorbed
 Useful substances filter out of the renal
tubules and back into the capillaries
around the tubules = reabsorption
Filtration
Secretion
 Opposite of reabsorption
 Secretion transports substances from
blood into collecting tubules
 Substances include creatinine,
hydrogen ions, potassium ions, and
some drugs
 Electrolytes are selectively secreted to
maintain body’s acid-base balance
Urinary Output
 Average= 1500 ml/day
 Urinalysis- examination of urine to
determine presence of blood cells,
bacteria, acidity level, specific gravity
and physical characteristics (color,
clarity and odor)
 Normal in urinalysis = Ammonia
 not normal = glucose, blood, pus
Ureters
 One from each kidney
 Carry urine from kidney to bladder
 Smooth muscle tube with mucous
membrane lining
 Peristalsis pushes urine down ureters
 The tubes that connect the kidneys
and bladder.
Path of urine formation
 Afferent arteriole - Glomerulus –
Bowman’s capsule – proximal convoluted
tubule – loop of Henle – distal convoluted
tubule – collecting tubule – renal pelvis ureter
Urinary Bladder
 Hollow, muscular organ – in the pelvic
cavity
 Made of elastic fibers and involuntary
muscle
 Stores urine- usually about 500cc
 Emptying urine (voiding) is involuntary but
controlled through nervous system
(voluntary)
 Function = store and aid in elimination of
urine
 Urine leaves through urethra to outside
opening = Urinary Meatus
Chemical Control
 Reabsorption of H2O in distal
convoluted tubule controlled by ADH
(antidiuretic hormone)
 Secretion and regulation of ADH
controlled by hypothalamus
 Diuretics inhibit reabsorption of H2O
 Medications can replace chemicals
created by body i.e. renin = diuretic
 Production of urine is controlled by
ADH and aldosterone
Chemical Control
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Renin Urinary System
 Whereas adrenaline and noradrenaline enhance
vasoconstriction, aldosterone influences the filtration
function of the kidneys. The kidneys retain more
sodium and water in the body and excrete more
potassium. The vasopressin from the pituitary gland
prevents the excretion of water without affecting the
electrolytes sodium and potassium.
 In this way, the overall volume of blood in the body is
increased: more blood is pumped through constricted
arteries, which increases the pressure exerted on the
artery walls – the blood pressure.
Chemical Control
 Aldosterone: promtoes excretion of potassium and
hydrogen ions and reabsorption of sodium ions; acting
on the distal tubules and collecting ducts of
the nephron, increasing reabsorption of ions and water
in the kidney, to cause the conservation of sodium,
secretion ofpotassium, increase in water retention, and
increase in blood pressure and blood volume
 If blood pressure drops too low, or blood
volume gets too low, or too concentrated
(not enough water in it), ADH released
ADH
 When the blood becomes more concentrated,
as happens when an animal is deprived of
water, ADH is secreted and causes more water
to be absorbed from the collecting ducts so
that concentrated urine is produced. When
plenty of water has been consumed, and the
blood is dilute, no ADH is secreted and no or
little water is absorbed from the collecting
ducts, so dilute urine is produced.
Chemical Control
 Diuretics increase urinary output by
inhibiting reabsorption of water
Nervous Control
 Direct control through nerve impulses
on kidney blood vessels
 Indirect control through stimulation of
endocrine glands, whose hormonal
secretions will control
urinary secretion
Disorders of the Urinary
System
Renal Calculi (Kidney Stones)
 Made of crystals of calcium phosphate and
uric acid
 Gradually they get larger until they block
ureters…can causey hydronephrosis
 First symptom- severe pain
 Other symptoms- nausea and vomiting,
frequency, chills, fever, hematuria
 Diagnosis- by symptoms, ultrasound, or xray
 Rx- increase fluids to flush out stone,
medications, and if needed- lithotripsy
Lithotripsy
 Surgical procedure to remove kidney
stones
 Shock waves hit dense stones and
break them up
 Done on outpatient basis
Nephritis
 Inflammation of the kidney (kidney
infection)
Incontinence =
 Involuntary urination
Cystitis
 Inflammation of the mucous
membrane lining of the urinary
bladder
 Most common cause- E. Coli
 Symptoms- Dysuria (painful
urination), lower abd pain, and
frequency
 Usually in females (shorter urethra)
 Rx- antibiotics
Dialysis (Hemodialysis)
 Used for kidney failure
 Involves the passage of blood through
device with semipermeable membrane
 Dialysis serves as substitute kidney…
replaces filtration
 Blood from patient flows through
machine and is filtered
 Can be done at home or in clinic
 Takes 2-4 hours, 2-3 times a week
Kidney Transplant
 As a last resort
 Involves donor organ from someone
with a similar immune system
 Main complication- rejection
Terminology
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Enuresis- bedwetting
Incontinence – involuntary urination
Gylcosuria- sugar in urine
Nocturia- frequent urination at night
Polyuria- large amounts of urine
Anuria- no urine produced
Hematuria- blood in urine
Diuretic- drug or substance to
increase urine production
 Oliguria – decreased urine production
(sign of kidney failure)