Chapter 15
The Urinary System
Anatomy of the Kidney
• General
– filter all blood every 30 minutes
• kidneys organs of excretion
– eliminate nitrogenous wastes (urea)
– eliminate toxins
– eliminate drugs
– excess ions
– excess water
– metabolic wastes
• Regulate blood volume
• make enzymes for blood pressure and
red blood cell productions
• composition of system
– paired kidneys
– urinary bladder
– ureters
– urethra
• renal blood supply
• renal artery --> kidney
»kidney --> renal vein
– Nephrons
• functional unit of kidney
– 1 million per kidney, clean blood form urine
• glomerulus
– ball of capillaries, forces material to be filtered into
• bowman’s capsule
– transports materials (filtrate) into tubule
• renal tubule
– 1.25 inches
» proximal convoluted tubule - reabsorption of water
and solutes
» loop of henle - reabsorption of Na and Cl ions
» distal convoluted tubule - reabsorption of water
» Na, Cl
• collecting tubule
– contains urine - nitrogenous wastes, water and salts
Label with functions
23-7
Urine Formation
• Filtration
• glomerulus
• blood pressure
• nonselective
• Reabsorption
• tubules --> capillaries
• materials which need to be returned to blood
• Secretion
• capillaries --> tubules get rid of substances
not contained in the filtrate
Kidney Control of Blood Composition
• Nitrogenous wastes
• urea - break down of proteins
• uric acid - breakdown of nucleic acids
• creatinine - breakdown of creatine phosphate CP
• Water and electrolyte balance
• water
–
–
–
–
ADH ~ water to be reabsorbed
aldosterone ~ causes Na + to be going back to blood
polyuria ~ lose water and salt, DEHYDRATED
ANH ~ atrail natriueretic hormone lose Na+, lose water
• electrolytes
– Na +, K +, Cl -, Ca ++
• Blood acid - base balance
•
•
•
•
blood pH 7.35 - 7.45
alkalosis
acidosis
buffers
– pH goes up when kidneys excrete bicarbonate ions
– pH goes down when kidneys reabsorb bicarbonate
ions
Urine Characteristics
• Urinalysis
• physical aspects – color, clarity, specific
gravity, odor
• chemical aspects - water, urea, salt, ions, pH
• microscopic aspects – types of cells
• Characteristics
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•
•
•
•
color - clear to yellow
clarity - transparent
odor - odorless
pH - 5.5 to 8
specific gravity - 1.001 - 1.035
• Urine output
• 1-2 liters per day
• 95 % water 5% organic and inorganic
• volume
• dilute urine or concentrated urine
• Factors- heat, amount of sweat produced
amount of liquids consumed, salt in diet
• abnormal urine
•
•
•
•
•
•
•
glucose (glycosuria) ,
proteins – albumin & ketones,
hemoglobin, bile pigments (brown)
reddish - blood, liver problem
red blood cells - bleeding, kidney stones
leukocytes - pus , milky - pus
green - bacterial infection
• Structure
Ureters
• slender tubes, 10 -12 inches long
• function
• collect and transfer urine from all collecting
tubules to bladder
• Problems
• kidney stones:
• Uric Acid - forms crystals
• Calcium (oxalate or phosphate)
• Struvite (infection)
Urinary Bladder
• Functions
• stores urine 500 ml can hold 1000 ml
• expels urine 1-2 liters a day
• Urethra
• tube thru which urine is expelled
• males - 8 inches , urine & sperm
• females - 1.5 inches
Urethritis inflammation of urethra
• Sphincters
• internal - smooth muscle relaxes 200 -300 ml
• external – skeletal muscle
• Micturition
• voiding - empty bladder
• bladder contracts internal sphincter relaxes
and external
• incontinence - can’t control external
sphincter
• urinary retention - surgery, diseases, use
catheter
• cystitis
• bladder inflammation can lead to kidney
inflammation- pyelitis
Aging of the Urinary System
• Renal Function decreases with age
• incontinence increases, nocturia
• urinary tract infections increase
• dysuria
• painful urination
• polyuria
• frequent urination
• oliguria - low urinary output
• increase in prostate cancer
Disorders
• Infections
• E. Coli
• streptococcus --> glomerulonephritis
• sexually transmitted diseases
• polycystic kidney disease