The Urinary System: Anatomy and Physiology Components Kidneys Ureters Urinary bladder Urethra

Organs of the Urinary System Kidneys Ureters Urinary bladder Urethra

Function Remove nitrogenous wastes (urine) Maintain electrolyte, acid-base, and fluid balance of blood Homeostatic organ Acts as blood filter Release hormones: calcitriol & erythropoietin Calcitriol increases the level of calcium (Ca2+) in the blood by increasing the uptake of calcium from the gut into the blood, and possibly increasing the release of calcium into the blood from bone

The Urinary System: Anatomy and Physiology Kidneys are supplied with blood from renal arteries Located Retroperitoneally Lateral to T 12 – L 3 Vertebra

Relationship of Kidneys to Vertebra and Ribs

Nephrons About 1 million nephrons are in a kidney. They are the functioning unit of the kidney

Nephrons 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

PARTS OF NEPHRON

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

General Functioning of the NEPHRON blood General Functioning of the NEPHRON filtration tubular reabsorption and secretion urine “refreshed” blood

Formation of Urine Renin also controls the filtration rate. Responds to three types of stimuli: Drop in blood pressure Sympathetic stimulation 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.

Sphincter Muscles on Bladder Internal urethral sphincter: Smooth muscle Involuntary control More superiorly located External Urethral sphincter: Skeletal muscle Voluntary control Posteriorly located