Summary of "[중2 과학] 5단원 모든 개념 완벽 정리"

Summary of [중2 과학] 5단원 모든 개념 완벽 정리

The animal body is organized hierarchically: cells → tissues → organs → organ systems → individual organism.
Cells are the basic units; examples include muscle cells and epithelial cells.
Tissues are groups of similar cells; organs are formed by different tissues with specific shapes and functions (e.g., stomach stores and digests food).
Organ systems consist of multiple organs working together (e.g., digestive system).
Plants also have tissues and organs (stem, root) but do not have organ systems like animals.
An individual organism is made up of multiple organ systems.

Nutrients provide energy, build the body, and regulate functions.
Three major nutrients:
- Carbohydrates: main energy source, 4 kcal/g; excess stored as fat.
- Proteins: build body, energy source (4 kcal/g), regulate body functions.
- Fats: energy source (9 kcal/g), build body.
Inorganic salts (e.g., sodium, iron, calcium, potassium) form bones/blood and regulate functions.
Vitamins regulate body functions in small amounts.
Water (60-70% of body) transports substances and regulates temperature due to its high specific heat.

Digestion breaks down large nutrients into smaller molecules for absorption.
Digestive enzymes are specific to certain nutrients and work best at body temperature and specific pH.
Digestive system includes:
- Digestive tract (mouth, esophagus, stomach, small intestine, large intestine).
- Accessory organs (liver, gallbladder, pancreas) secrete digestive juices but food does not pass through them.
Key Digestive enzymes:
- Amylase (mouth, pancreas): starch → glucose.
- Pepsin (stomach, with hydrochloric acid): protein → smaller peptides.
- Trypsin (pancreas): proteins → peptides.
- Lipase (pancreas): fats → fatty acids + monoglycerides.
- Bile (liver/gallbladder): emulsifies fats but contains no enzymes.
Nutrients absorbed mainly in the small intestine, aided by villi and microvilli increasing surface area.
Water-soluble nutrients absorbed into capillaries; fat-soluble nutrients absorbed into lacteals (lymph vessels).

Transports nutrients, oxygen, and wastes.
Heart pumps blood via contractions (heartbeat).
Heart structure:
- Right atrium receives deoxygenated blood from body via vena cava.
- Right ventricle pumps blood to lungs via pulmonary artery.
- Left atrium receives oxygenated blood from lungs via pulmonary vein.
- Left ventricle pumps oxygenated blood to body via aorta.
Blood vessels:
- Arteries: thick, elastic walls, high pressure, carry blood away from heart.
- Capillaries: thin walls for exchange of gases, nutrients, and wastes.
- Veins: thinner walls, valves prevent backflow, carry blood to heart.
Blood components:
- Plasma: yellow liquid, mostly water, transports substances.
- Red blood cells: carry oxygen via hemoglobin.
- White blood cells: immune defense via phagocytosis.
- Platelets: blood clotting.
Blood circulation:
- Arterial blood: oxygen-rich.
- Venous blood: oxygen-poor, carbon dioxide-rich.
- Blood circulates from heart → body → heart → lungs → heart.

Function: absorb oxygen and expel carbon dioxide.
Pathway: nose → trachea → bronchi → lungs (Alveoli).
Nose filters, warms, and moistens air.
Alveoli: tiny air sacs surrounded by capillaries; large surface area for gas exchange.
Gas