Skeletal System Framework: The human adult skeleton consists of 206 bones divided into the axial skeleton (80 bones: skull, vertebral column, sternum, ribs) and appendicular skeleton (126 bones: pectoral and pelvic girdles, upper and lower limbs), providing structural support, protection for delicate organs, and anchor points for skeletal muscles.
Digestive System Anatomy & Physiology: Ingestion, digestion, absorption, assimilation, and egestion occur across the alimentary canal (approx. 9 meters long), comprising the buccal cavity, oesophagus, stomach, small intestine (duodenum, jejunum, ileum), and large intestine, aided by accessory glands like the liver and pancreas.
Circulatory System Mechanics: A closed double-circulatory system centered around the 4-chambered human heart pumps deoxygenated blood to the lungs via pulmonary circulation and oxygenated blood to systemic tissues via systemic circulation, driven by rhythmic cardiac cycles (0.8 seconds).
Nervous System Coordination: The central nervous system (CNS, comprising the brain and spinal cord) integrates sensory inputs and coordinates motor responses via the peripheral nervous system (PNS), with neurons transmitting electrochemical impulses through action potentials and chemical synapses.