Our external environment

Our internal environment

Homeostasis HOMEOSTASIS means maintaining a constant, unchanging internal environment for our cells. What are some ways the human body maintains this constant internal environment?

The Urinary System Structure and Function

Learning Outcomes: C13 – analyze the functional interrelationships of the structures of the urinary system Identify organs of the urinary system and their functions Identify parts of the kidney Describe the structure of the nephron

Excretion Excretion refers to the removal of metabolic (cellular) wastes from the body Organs of excretion include the lungs, liver, skin and kidneys

Fig. 16A

Fig. 16.1

Functions of the Kidneys Removal of nitrogenous metabolic wastes such as urea, uric acid, creatinine from the blood Maintenance of water and salt balance in the blood (affects blood pressure) Maintenance of blood pH by excreting or reabsorbing ions

Nitrogenous Wastes When amino acids are metabolized by the liver, the amino group is removed

This produces ammonia, which is toxic to cells

Urea Ammonia combines with carbon dioxide to form urea, which is less toxic and can be safely transported in the blood

Urea and other nitrogenous wastes are removed from the blood by the kidneys

All of the blood in the body passes through the kidneys more than 20 times a day

Kidney Structure 3 major areas: –Renal cortex - granulated outer layer –Renal medulla - striated middle layer –Renal pelvis - inner cavity

Fig. 16.3

Nephrons Structural unit of the kidneys Tubule surrounded by capillary network Microscopic ~ 10 6 nephrons per kidney In renal cortex and medulla

Nephron Structure Bowman’s capsule (glomerular capsule) in the cortex - contains a bundle of capillaries called the glomerulus

Proximal convoluted tubule - in the cortex nearest to the capsule

Loop of Henle (loop of the nephron) - extends from the cortex into the medulla

Distal convoluted tubule - in the cortex

Collecting duct - extends into the medulla Empties into the renal pelvis

Blood vessels Renal artery enters the kidney, Renal vein takes blood away from the kidney after it has been processed

Afferent arteriole goes into the capsule Glomerulus is a bundle of capillaries inside the capsule Efferent arteriole comes out of the capsule

Peritubular capillary network follows the nephron and surrounds it, allowing for exchange of substances

Fig. 16.4