Human Anatomy, 3rd edition
Prentice Hall, © 2001

Introduction
– Cellular metabolism produces wastes
• CO
2
• Urea
• Ammonia
– Kidneys rid the body of most nitrogenous wastes
– Kidneys regulate the chemical make-up of blood
Human Anatomy, 3rd edition
Prentice Hall, © 2001

General Functions
– Serves as a blood filter
– Toxins, metabolic wastes leave the body in urine
– H
2
O, glucose, and amino acids are returned to blood
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Organs of the Urinary System
– Kidneys (paired)
• Perform filtering functions and manufacture urine
– Ureters (paired)
• Transport urine
– Urinary bladder (single)
• Stores urine
– Urethra (single)
• Transports urine
Human Anatomy, 3rd edition
Prentice Hall, © 2001

The Urinary System
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Location of Kidneys
– Lie against the dorsal body wall
– Beneath the parietal peritoneum
– In the superior lumbar region
• Protected by the lower part of the rib cage
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Location of the Kidneys
Human Anatomy, 3rd edition
Prentice Hall, © 2001

External Structure of the Kidney
– Hilus
– Renal capsule
– Renal artery
– Renal vein
– Ureter
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Internal Structure of the Kidney
– Renal cortex
– Renal medulla
• Renal pyramids
• Renal papilla
– Renal pelvis
– Calyces
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Structure of the Kidney
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Blood Supply of the Kidney
– Approximately ¼ of the total blood supply of the body passes through the kidneys each minute
– Renal artery branches inside the kidney
• Supplies the pyramids and the cortex
– Venous blood leaves the cortex and medulla
• Small veins join the renal vein
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Blood Supply of the Kidney
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Blood Supply of the Kidney
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Nephrons and Urine Formation
– Nephrons form the urine product
• Filtration
• Reabsorption
• Secretion
– Each kidney contains about 1 million nephrons
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Structure of a Nephron
– 2 main structures
•
Glomerulus
– a knot of capillaries
•
Renal tubule
– Bowman’s capsule surrounds the glomerulus
– Proximal convoluted tubule
– Henle’s Loop
– Distal convoluted tubule
– Renal tubule enters collecting duct
• Receives urine from nephrons
• Delivers final urine product into the calyces
Human Anatomy, 3rd edition
Prentice Hall, © 2001

A Renal Corpuscle
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Renal Corpuscles
Human Anatomy, 3rd edition
Prentice Hall, © 2001

A Typical Nephron
Human Anatomy, 3rd edition
Prentice Hall, © 2001

A Typical Nephron
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Blood Supply of the Nephron
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Urine Formation
– Filtration
• Blood in afferent arteriole is under high pressure
• Glomerulus acts as a filter
•
Filtrate = the substance that is filtered from the blood into the renal tubule
• Blood leaves the glomerulus through the efferent arteriole
– Reabsorption
• Filtrate contains useful substances (as well as wastes) which are returned to the blood
• Most depends on active transport
– Transported into peritubular capillaries
– Most occurs in the proximal convoluted tubule
– Secretion
• Substances move from cells or blood (peritubular capillaries) into the filtrate
• Important in controlling pH of blood
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Control of Blood Composition
– Excretion of nitrogen-containing compounds
• Urea
• Uric acid
– Water and electrolyte balance
• Regulated by hormones
Human Anatomy, 3rd edition
Prentice Hall, © 2001

Summary of Urine Flow
– Kidneys produce urine
• Filtration
• Reabsorption
• Secretion
– Ureters
– Bladder
– Urethra
Human Anatomy, 3rd edition
Prentice Hall, © 2001