Human Body Systems: Digestive, Respiratory, Circulatory, and Genetic Basics

Function of the Digestive System

Breaks down food into small molecules, absorbs nutrients, and removes waste.

Organs Involved in Digestive System

Mouth, Esophagus, Stomach, Small intestine, Large intestine, Liver, pancreas, gallbladder (helpers)

Ingestion

Taking in food.

Digestion

Mechanical + chemical breakdown.

Absorption

Nutrients move into bloodstream (small intestine).

Elimination

Removing solid waste.

Villi & Microvilli

Tiny finger-like projections in the small intestine that increase surface area for more nutrient absorption.

Function of Respiratory System

Takes in oxygen and removes carbon dioxide. Works with circulatory system for gas exchange.

Organs Involved in Respiratory System

Nose/mouth, Pharynx, Larynx, Trachea, Bronchi, Bronchioles, Alveoli, Lungs, Diaphragm.

Inhalation

Diaphragm contracts + moves down, rib cage expands, lung volume increases, pressure decreases → air enters lungs.

Exhalation

Diaphragm relaxes + moves up, rib cage lowers, lung volume decreases, pressure increases → air leaves lungs.

Gas Exchange

Happens in alveoli (air sacs) and capillaries where oxygen diffuses into blood; CO₂ diffuses out.

Factors That Affect Gas Exchange

Large surface area (many alveoli), thin membrane (1 cell thick), moist surface (gases dissolve).

Function of Circulatory System

Moves nutrients, oxygen, hormones, and removes wastes.

Organs Involved in Circulatory System

Heart, Blood vessels (arteries, veins, capillaries), Blood.

Path of Blood Through the Body

Body → vena cava → Right atrium → Right ventricle → Pulmonary artery → lungs → Pulmonary vein → Left atrium → Left ventricle → Aorta → body.

Heart Attack

When blood flow to heart muscle is blocked → heart cells die.

Causes / Risk Factors for Heart Attack

Plaque buildup in arteries (atherosclerosis), Smoking, Poor diet, Lack of exercise, High cholesterol, High blood pressure, Genetics.

Respiratory + Circulatory Interaction

Respiratory brings in O₂ and removes CO₂; Circulatory transports O₂ to cells and brings CO₂ back to lungs.

Digestive + Circulatory Interaction

Digestive breaks food into nutrients; Circulatory absorbs nutrients through villi and carries them around the body.

What is DNA?

A molecule that carries genetic information used to build and run the organism.

Why is DNA Important?

Controls traits, directs protein production, needed for cell function and division.

Role of a Gene

A small section of DNA that codes for a specific protein.

Benefits of DNA Screening

Detect genetic disorders early, allows prevention or treatment.

Risks of DNA Screening

Privacy issues, insurance/employment discrimination.

Benefits of Cloning

Preserve endangered species, produce identical cells for research.

Risks of Cloning

Low success rate, ethical concerns, possible health problems in clones.

Benefits of Transgenic Organisms (GMOs)

Resistant to pests, grow faster, higher nutrition.

Risks of Transgenic Organisms (GMOs)

Environmental impact, allergies, cross-breeding with wild plants.

Dermal Tissue

Outer covering that protects the plant and controls water loss (cuticle, stomata).

Ground Tissue

Middle layer responsible for photosynthesis, storage, and support.

Vascular Tissue

Transports water and nutrients; Xylem carries water up, Phloem carries sugars down.

Roots

Absorb water and minerals, anchor plant; Fibrous Roots prevent erosion, Tap Root is a strong anchor.

Stems

Support the plant and transport materials between roots/leaves.

Leaves

Main site of photosynthesis, contain stomata for gas exchange.

Photosynthesis Equation

6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ + 6O₂ (carbon dioxide + water + energy → glucose + oxygen).