Notes on Human Organ Systems: Digestion & Circulation

Organs and Organ Systems

• Organ: $\ge 2$ tissues working for a specific function (e.g., brain, heart).
• Organ System: Multiple organs with related functions perform a major body function.
• Excretory System: Kidneys, bladder remove waste, excess water/salt.

Digestive System Components and Functions

• Oral Cavity: Breaks down food into smaller particles.
• Esophagus: Transports food to stomach.
• Stomach: Kills germs, stores food, gradually releases it for small intestine digestion.
• Pancreas & Liver: Provide enzymes for small intestine.
• Small Intestine: Site of most digestion and nutrient absorption into blood.
• Large Intestine: Absorbs water, stores feces.

Structure-Function Relationship

• Principle: Structure is directly related to function.
• Examples:
  • Sperm Cell: Tail for movement.
  • Red Blood Cells: Efficient shape for blood flow.
  • Stomach: Withstands acid, stores food.

Small Intestine Structure and Function

• Muscle Tissue: Mixes food and moves it through.
• Villi: Folds create large surface area for increased nutrient absorption.
• Capillaries within Villi: Absorb nutrients into blood.

Circulatory System

• Components: Blood (transports $O_2$, glucose), blood vessels, heart (pumps blood).

Interplay of Digestive and Circulatory Systems

• Digestive system breaks down food; small intestine passes nutrients to circulatory system.
• Circulatory system transports nutrients to body cells.

Importance of Digestive Pathway Sequence

• Prior processing in oral cavity and stomach is crucial.
• Without it: Food too large, germs not killed, digestion/absorption impaired.