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.

The left ventricle has the thickest wall because it pumps to the whole body. The pulmonary artery is the only artery carrying deoxygenated blood.

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.

Oxygen is carried on haemoglobin; most carbon dioxide travels dissolved as bicarbonate, not on haemoglobin.

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.

Depolarisation is sodium moving in, repolarisation is potassium moving out. Getting those two the right way round covers most action-potential questions.

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.

Origin is the fixed attachment, insertion is the moving one. The muscle pulls the insertion towards the origin.

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.

The axial skeleton is skull, spine and ribs. The appendicular skeleton is the limbs and the girdles that attach them.

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.

The liver makes bile, the gallbladder stores it, and the pancreas supplies both enzymes and bicarbonate. Three organs, three distinct jobs.

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.

Learn the four steps in order. Most urinary questions are really asking which step something happens in.

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.

Pair each hormone with the gland and the effect. Questions almost always test the trio rather than the hormone alone.

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.

Ovulation is roughly day 14 of a 28-day cycle, triggered by a surge in luteinising hormone.

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.

The epidermis has no blood supply of its own. That fact explains a surprising number of questions about healing and burns.

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.

Active immunity is your own antibodies, from infection or vaccination. Passive immunity is borrowed antibodies, and it does not last.

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.

The retina converts light to a nerve signal and the cochlea converts vibration to one. Each sense has one such conversion point, and that is usually what is asked about.

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.

The diaphragm separates the thoracic cavity from the abdominal one. That boundary is worth fixing early.

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.

All directional terms assume anatomical position: standing, facing forward, palms out. Answers change if you forget that.

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.

Picture the cut. Sagittal is a slice down the middle from front to back; transverse is a slice straight across.

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.

For each system, learn one clinical application. It anchors the structural detail far better than repetition does.