October 2026 HESI A2 Anatomy and Physiology Study Guide

The cardiovascular system The heart and the vessels that carry blood. Blood moves right atrium, tricuspid valve, right ventricle, pulmonary artery, lungs, pulmonary vein, left atrium, mitral valve, left ventricle, aorta, body. Arteries carry blood away from the heart, veins carry it back, and capillaries are where exchange happens. Read the full guide The respiratory system Air travels nose, pharynx, larynx, trachea, bronchi, bronchioles, alveoli. Gas exchange happens across the alveolar membrane by diffusion. The diaphragm contracts and flattens to draw air in, and relaxes to push it out. Read the full guide The nervous system The central nervous system is brain and spinal cord; everything else is peripheral. The autonomic division splits into sympathetic, which is fight or flight, and parasympathetic, which is rest and digest. Neurons receive at the dendrites, transmit along the axon and communicate across a synapse. Read the full guide The muscular system Three muscle types: skeletal, which is voluntary and striated; cardiac, which is involuntary and striated; and smooth, which is involuntary and not striated. Contraction happens when actin and myosin filaments slide past each other, which requires calcium and ATP. Read the full guide The skeletal system Bone supports the body, protects organs, stores calcium and produces blood cells in the marrow. Osteoblasts build bone and osteoclasts break it down, and the balance between them determines bone density. Read the full guide The digestive system The path is mouth, oesophagus, stomach, small intestine, large intestine, rectum. Chemical digestion starts in the mouth with salivary amylase, continues in the stomach with acid and pepsin, and finishes in the small intestine, where almost all absorption occurs. Read the full guide The urinary system The kidneys filter blood, regulate fluid and electrolyte balance and help control blood pressure. The nephron is the functional unit, and urine forms through filtration, reabsorption and secretion before excretion. Read the full guide The endocrine system Glands releasing hormones into the bloodstream, giving slower and longer-lasting effects than nerve signalling. The pituitary is the master gland, directed by the hypothalamus; insulin lowers blood glucose and glucagon raises it; thyroid hormones set metabolic rate. Read the full guide The reproductive system The male and female structures, the hormones that regulate them, and the phases of the menstrual cycle. Oestrogen and progesterone drive the female cycle; testosterone drives male development. Read the full guide The integumentary system Skin, hair and nails. Skin is the largest organ and provides a barrier, temperature regulation, sensation and vitamin D synthesis. Its layers are epidermis, dermis and the subcutaneous layer beneath. Read the full guide The lymphatic system and immunity Lymph vessels return fluid to the bloodstream, and lymph nodes filter it. Immunity is innate, meaning present from birth and non-specific, or adaptive, meaning learned and specific. B cells make antibodies; T cells attack directly. Read the full guide Special senses Sight, hearing, balance, taste and smell. Light passes cornea, pupil, lens and retina; sound passes outer ear, eardrum, ossicles and cochlea. Balance is handled by the semicircular canals in the inner ear. Read the full guide

Human body plan How the body is organised: cells into tissues, tissues into organs, organs into systems. The main body cavities are cranial, thoracic, abdominal and pelvic, and knowing which organs sit in which is assumed by later questions. Read the full guide Anatomical terminology The shared vocabulary of position and direction: superior and inferior, anterior and posterior, medial and lateral, proximal and distal, superficial and deep. Everything else in the subject is described using these terms. Read the full guide Anatomical imaging How structures are viewed and described in planes: sagittal divides left from right, frontal divides front from back, transverse divides upper from lower. Imaging questions test the plane rather than the technology. Read the full guide Clinical anatomy Applying structure to practice: which landmark you palpate, where an injection goes, which structure a symptom points to. This is where anatomy stops being memorisation and starts being nursing. Read the full guide