Organ Systems and Their Connection

Heart

Muscular organ that pumps blood throughout the body; ensures one-way blood flow through chambers

Artery

Blood vessel with thick muscular walls and small diameter; carries oxygenated blood away from the heart at high pressure

Vein

Blood vessel with thin walls, large diameter, and valves; carries deoxygenated blood back to the heart at low pressure

Capillary

One cell layer thick blood vessel; site of gas and nutrient exchange between blood and body tissues

Oxygenated blood

Blood rich in oxygen from the lungs; travels in arteries away from the heart

Deoxygenated blood

Blood low in oxygen; travels in veins back to the heart and then to the lungs

Blood pressure

Pressure exerted by blood on vessel walls; highest in arteries near heart, decreases in capillaries and veins

Gas exchange in capillaries

Oxygen diffuses into body tissues and carbon dioxide diffuses into blood to be carried to lungs

Epiglottis

Flap of tissue that closes off the trachea during swallowing to prevent food from entering airways

Trachea

Windpipe; tube that carries air from pharynx to bronchi; conducts air to the lungs

Bronchioles

Small branches of bronchi that lead directly to alveoli in the lungs

Alveoli

Tiny air sacs in lungs surrounded by capillaries; site of gas exchange between air and blood

Diaphragm

Muscle below the lungs that contracts to pull air in (inhalation) and relaxes to push air out (exhalation)

Inhalation

Process where diaphragm contracts, lungs expand, and air is drawn into the body

Exhalation

Process where diaphragm relaxes, lungs contract, and air is pushed out of the body

Gas exchange in alveoli

Oxygen diffuses from alveoli into capillaries; carbon dioxide diffuses from blood into alveoli to be exhaled

Thin alveoli membrane

Only one cell layer thick; allows quick diffusion of oxygen and carbon dioxide for efficient gas exchange

Esophagus

Muscular tube that transports food from the mouth to the stomach using peristalsis

Stomach

Muscular organ that churns and mixes food with gastric juices; begins protein digestion

Pancreas

Gland that produces digestive enzymes and insulin; enzymes break down carbohydrates, proteins, and fats

Small intestine

Organ where most nutrient absorption occurs; has villi to increase surface area for diffusion

Villi

Finger-like projections in small intestine that increase surface area; only one cell thick for nutrients to diffuse into bloodstream

Large intestine (colon)

Absorbs water and electrolytes from food; stores waste (feces) until elimination

Mechanical digestion

Physical breakdown of food (chewing, churning in stomach)

Chemical digestion

Breakdown of food using enzymes and acids (in stomach and small intestine)

Nutrient absorption

Process where digested nutrients pass through villi into the bloodstream for transport to cells

Circulatory & Respiratory connection

Circulatory carries oxygen to cells and removes CO₂; respiratory provides oxygen and removes CO₂

Circulatory & Digestive connection

Circulatory distributes nutrients from digestive system and provides oxygen to digestive organs

Respiratory & Digestive connection

Respiratory provides oxygen and digestive provides nutrients; both support cellular respiration

Cellular respiration

Process where cells use oxygen and glucose to produce ATP energy; requires all three systems

Why capillaries are thin

One cell layer allows rapid diffusion of oxygen and nutrients; maximizes surface area for exchange

Why alveoli are thin

One cell layer allows quick diffusion of gases; maximizes surface area for gas exchange

Why small intestine has villi

Finger-like projections increase surface area; one cell thick for rapid nutrient diffusion

Why arteries are muscular

Thick muscular walls withstand high pressure from heart and help propel blood

Why veins have valves

Prevent backflow of blood; ensure one-way movement back to heart at low pressure

Why heart has chambers

Separate oxygenated and deoxygenated blood; ensure efficient one-way blood flow

Blood pressure trend

Decreases from arteries to capillaries to veins due to friction and distance from heart

Breathing rate in fit vs unfit person

Unfit person breathes faster during same exercise; fit person is more efficient

Blood glucose after meal

Rises after eating; insulin increases to help cells absorb glucose; levels return to normal