THE URINARY SYSTEM7.4

From the Heart to the Pelvis

Aorta renal arteries kidneys.

Kidney: fist-shaped, about 0.5 kg.

Can hold as much as 25% of body’s blood.

Wastes are filtered from blood by kidneys and conducted to the urinary bladder by ureters.

Urinary sphincter: muscle located at base of bladder acting as a valve. Voluntary emptying

When bladder stretches, sends signal to brain. 200 mL: small signal sent 400 mL: more stretch receptor activated 600 mL: voluntary control is lost.

Sphincter relaxes, urine enters urethra, and is voided.

General Kidney Structure Cortex: outer layer Medulla: inner layer Renal pelvis: joins kidney to ureter.

Nephrons Nephron: slender tubules

About one million in each kidney Renal artery afferent arterioles

nephrons efferent arterioles peritubular capillaries (net of capillaries that wrap around kidney tubules.

Glomerulus: capillary bed from afferent arterioles. Surrounded by funnel-like part of nephron:

Bowman’s Capsule In the cortex of the kidney.

Bowman’s Capsule Where fluids (from blood) to be processed

into urine enter the kidney. Capsule tapers into thin tubule: proximal

tubule. Proximal tubule loop of Henle (descends

into the medulla of the kidney) distal tubule (last segment of nephron) collecting ducts.

Collecting duct: collects urine from many nephrons merge in kidney pelvis.

urine

blood

filtration

tubular reabsorption and secretion

General Functioning

of the Kidney

“refreshed” blood

Organs of the

Urinary

System

kidneys

ureters

urinary bladder

urethra

vein

artery

afferent

arteriole

efferent arteriol

eglomerulus

peritubular

capillaries

Bowman’s capsule

proximal convoluted tubuledistal convoluted tubule

loop of

Henle

collecting duct

renal cortex

renal medulla

Each kidney contains over 1 million nephrons and thousands of collecting ducts

Collecting duct

Loop of Henle

PCT

DCTGlomerulus

Glomerular

Filtration

afferent arteriole

glomerulus

efferent

arteriole

Bowman’s capsule

Filters blood; proteins can’t pass through

With help from your textbook, define the following terms:

Ureters Urethra Cortex Medulla Renal pelvis Nephron Afferent arterioles Glomerulus Efferent arterioles Peritubular capillaries Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct

Summary

Seatwork/Homework Page 348, #1,2,3,4