Chapter 15: The Urinary System
Urinary System Regulates Body Fluids
Excretion: processes that remove waste and excess materials from
the body
Digestive System: excretes food residues and waste produced by
the liver
Respiratory System (lungs): excretes carbon dioxide
Integumentary System (skin): excretes water and salt
Urinary System (kidneys): excretes nitrogenous wastes, excess
solutes and water
The Kidneys Regulate Water Levels:
To maintain homeostasis,
Water input = water output
Kidneys adjust water output as necessary
-water input: food, drink, metabolism
-water output: lungs, skin, feces, kidneys
-kidneys modify output based on intake and loss
-output varies from ½ liter/day to 1 liter/hour
The Kidneys Regulate Nitrogenous Wastes and Other Solutes:
Protein metabolism produces nitrogenous wastes
Initially, NH3 (ammonia) is produced during breakdown of amino
acids
Liver detoxifies NH3, producing urea
Urea is transported from liver to kidneys for disposal
Other solutes regulated by kidneys
-Sodium, chloride, potassium, calcium, hydrogen ions, creatinine
Organs and Urinary System:
, Kidneys
– Principal organ of urinary system
– Cortex: outer portion of the kidney
– Medulla: inner region of the kidney
– Renal pelvis: hollow space in center of kidney where urine
collects
Ureters
– Muscular tubes that transport urine from kidneys to bladder
Urinary bladder
– Three layers of smooth muscle, lined with epithelial cells
– Stores urine (600–1,000 ml)
Urethra
– Carries urine from bladder to outside of body
– Two sphincters control urination
The Internal Structure of the Kidney:
Nephron: functional unit of the kidney
– Two functional parts:
– Tubule
– Associated blood supply
1 million nephrons per kidney
Each nephron consists of a long thin hollow tube (tubule) plus
associated blood supply
Role of nephrons: remove approximately 180 liters of fluid from the
blood daily, and return most of it, minus the wastes that are excreted
Nephron structure
– Glomerular capsule: cuplike end of nephron tubule surrounding
glomerulus (network of capillaries)—this is where filtration
occurs
– Four distinct regions of tubule
– Proximal tubule: extends from glomerular capsule to
renal medulla
2
Urinary System Regulates Body Fluids
Excretion: processes that remove waste and excess materials from
the body
Digestive System: excretes food residues and waste produced by
the liver
Respiratory System (lungs): excretes carbon dioxide
Integumentary System (skin): excretes water and salt
Urinary System (kidneys): excretes nitrogenous wastes, excess
solutes and water
The Kidneys Regulate Water Levels:
To maintain homeostasis,
Water input = water output
Kidneys adjust water output as necessary
-water input: food, drink, metabolism
-water output: lungs, skin, feces, kidneys
-kidneys modify output based on intake and loss
-output varies from ½ liter/day to 1 liter/hour
The Kidneys Regulate Nitrogenous Wastes and Other Solutes:
Protein metabolism produces nitrogenous wastes
Initially, NH3 (ammonia) is produced during breakdown of amino
acids
Liver detoxifies NH3, producing urea
Urea is transported from liver to kidneys for disposal
Other solutes regulated by kidneys
-Sodium, chloride, potassium, calcium, hydrogen ions, creatinine
Organs and Urinary System:
, Kidneys
– Principal organ of urinary system
– Cortex: outer portion of the kidney
– Medulla: inner region of the kidney
– Renal pelvis: hollow space in center of kidney where urine
collects
Ureters
– Muscular tubes that transport urine from kidneys to bladder
Urinary bladder
– Three layers of smooth muscle, lined with epithelial cells
– Stores urine (600–1,000 ml)
Urethra
– Carries urine from bladder to outside of body
– Two sphincters control urination
The Internal Structure of the Kidney:
Nephron: functional unit of the kidney
– Two functional parts:
– Tubule
– Associated blood supply
1 million nephrons per kidney
Each nephron consists of a long thin hollow tube (tubule) plus
associated blood supply
Role of nephrons: remove approximately 180 liters of fluid from the
blood daily, and return most of it, minus the wastes that are excreted
Nephron structure
– Glomerular capsule: cuplike end of nephron tubule surrounding
glomerulus (network of capillaries)—this is where filtration
occurs
– Four distinct regions of tubule
– Proximal tubule: extends from glomerular capsule to
renal medulla
2
