Animal Physiology: Circulation, Respiration, and Excretion
Maintaining Homeostasis in Animals
Circulatory system
The circulatory system transports oxygen, nutrients, hormones, and wastes. In many animals, the heart generates pressure that drives blood flow through vessels and capillaries.
Respiration and gas exchange
Gas exchange depends on diffusion gradients. In mammals, alveoli provide a large surface area and short diffusion distance for oxygen and carbon dioxide exchange.
Structure supports function
Thin exchange surfaces and rich blood supply increase diffusion efficiency.
Why are capillaries important in gas exchange and nutrient delivery?
Capillaries are thin enough to allow diffusion between blood and surrounding cells.
Correct answer: They have thin walls that allow exchange with tissues
What is the main job of kidneys?
Kidneys maintain homeostasis by adjusting excretion and reabsorption.
Correct answer: To filter blood and regulate water, ions, and wastes.
Organ system roles
| System | Primary function |
|---|---|
| Circulatory | Transport |
| Respiratory | Gas exchange |
| Excretory | Waste removal and osmotic balance |
| Endocrine | Hormonal regulation |
Which process is the primary mechanism by which oxygen moves from alveoli into blood?
Oxygen moves down its concentration gradient by diffusion.
Correct answer: Diffusion