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Components◦Kidneys◦Ureters◦Urinary bladder◦Urethra
The Urinary System: Anatomy and Physiology
Organs of the Urinary System
Kidneys
Ureters
Urinary bladder
Urethra
2
Function
1. Remove nitrogenous wastes (urine)2. Maintain electrolyte, acid-base, and
fluid balance of blood3. Homeostatic organ4. Acts as blood filter5. Release hormones: calcitriol &
erythropoietin
Kidneys are supplied with blood from renal arteries
• Located Retroperitoneally• Lateral to T 12 – L 3 Vertebra
The Urinary System: Anatomy and Physiology
Relationship of Kidneys to Vertebra and Ribs
Nephrons
About 1 million nephrons are in a kidney.
They are the functioning unit of the kidney
Consists of a renal corpuscle and a renal tubule.◦Glomerulus is a tangled cluster of blood
capillaries that makes up a renal corpuscle ◦Renal tubule leads away from the
glomerulus
Nephrons
Formation of Urine Glomerular filtration initiates urine
formation.◦Plasma is filtered by the glomerular
capillaries.◦Most of this fluid is reabsorbed into the
bloodstream.
Formation of Urine Urine formation summary:
◦ Glomerular filtration◦ Reabsorption of substances◦ Secretion of substances
urine
blood
filtration
tubular reabsorption and secretion
General Functioning of the NEPHRON
General Functioning of the NEPHRON
“refreshed” blood
Renin also controls the filtration rate.◦Responds to three types of stimuli:
1. Drop in blood pressure2. Sympathetic stimulation3. Decrease in chloride, potassium, and
sodium ions
Formation of Urine
Renin reacts with angiotensinogen to form angiotensin I.
Angiotensin-converting enzyme converts to angiotensin II
Helps maintain sodium and water balance Vasoconstricts the efferent arteriole Helps decrease glomerular filtration rate Stimulates kidneys to secrete aldosterone
Formation of Urine
Atrial natriuretic peptide(ANP) increases sodium excretion by increasing the glomerular filtration rate.
Formation of Urine
Urea is a result of amino acid catabolism. Uric acid is a result of the metabolism of
certain organic bases in nucleic acids. Urine is about 95% water.
◦ Contains urea and uric acid
Formation of Urine
Ureter drains into the urinary bladder Bladder empties to the outside of the body
through the urethra 1.5 to 2 L of urine is extracted every day.
Formation of Urine
Internal urethral sphincter:• Smooth muscle• Involuntary control• More superiorly located
External Urethral sphincter:• Skeletal muscle• Voluntary control• Posteriorly located
Sphincter Muscles on Bladder
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