Medicine

The skin (integumentary system). It covers approximately 1.5–2 m² in adults, protects against infection, regulates body temperature, and provides sensory input.

206 bones. They are divided into the axial skeleton (skull, spine, ribs — 80 bones) and the appendicular skeleton (limbs, shoulders, pelvis — 126 bones).

The right atrium, right ventricle, left atrium, and left ventricle. The right side pumps blood to the lungs; the left side pumps oxygenated blood to the body.

The liver detoxifies chemicals, metabolizes drugs, produces bile for digestion, stores glycogen for energy, synthesizes proteins (including clotting factors), and filters blood from the digestive tract.

The cerebrum (thinking, movement, senses), cerebellum (balance, coordination), and brainstem (breathing, heart rate, consciousness). Together they control all bodily functions.

Arteries carry oxygenated blood away from the heart (except pulmonary arteries) and have thick, muscular walls. Veins carry deoxygenated blood back to the heart and have thinner walls with valves to prevent backflow.

Mouth, esophagus, stomach, small intestine, large intestine (colon), rectum, and anus. Accessory organs include the liver, gallbladder, and pancreas.

The kidneys filter blood to remove waste and excess fluid (producing urine), regulate electrolytes (sodium, potassium), maintain acid-base balance, and produce hormones like erythropoietin (stimulates red blood cell production) and renin (regulates blood pressure).

Skeletal muscle (voluntary movement), cardiac muscle (heart contractions, involuntary), and smooth muscle (found in organs and blood vessels, involuntary). Each has a distinct structure suited to its function.

The spinal cord is a long bundle of nerves running from the brainstem through the vertebral column. It relays signals between the brain and body and controls reflexes.

Red blood cells (carry oxygen), white blood cells (fight infection), platelets (clotting), and plasma (liquid that carries cells, nutrients, hormones, and waste products). Blood makes up about 7% of body weight.

A network of tissues, organs (lymph nodes, spleen, thymus), and vessels that drains excess fluid from tissues, transports fats from the gut, and houses immune cells. It plays a key role in fighting infections.