Comprehensive 2025 ATI TEAS 7 Science Anatomy and Physiology Study Guide With Practice Questions

The endocrine system consists of glands that release hormones directly into the bloodstream (endocrine) or through ducts (exocrine). Some organs like the pancreas have both functions. Hormones, derived from amino acids or lipids (steroids), bind to target cells to trigger specific actions. Key glands and hormones: Hypothalamus (controls pituitary). Posterior Pituitary (stores and releases hypothalamus hormones): Oxytocin (uterine contractions), ADH (water reabsorption). Anterior Pituitary (produces own hormones): Growth hormone, Prolactin (milk production), TSH (thyroid stimulation), FSH (egg/sperm formation), LH (ovulation, androgens), ACTH (adrenal cortex stimulation). Pineal Gland: Melatonin (circadian rhythm). Thyroid Gland: T4, T3 (metabolic rate), Calcitonin (lowers blood calcium). Parathyroid Gland: Parathyroid hormone (increases blood calcium). Thymus Gland: Thymosin (stimulates T cells, immune function). Adrenal Glands: Medulla (epinephrine, norepinephrine for fight-or-flight), Cortex (glucocorticoids like cortisol for stress/inflammation, mineralocorticoids like aldosterone for electrolyte balance). Pancreas: Insulin (lowers blood glucose by facilitating uptake), Glucagon (raises blood glucose by releasing liver glycogen). Gonads (Ovaries/Testes): Ovaries produce estrogen (uterine lining, female characteristics) and progesterone (uterine lining maintenance, fetal development). Testes produce androgens like testosterone (sperm production, male characteristics). Hormone concentrations and primary functions vary between sexes.

The urinary system maintains osmotic pressure and eliminates metabolic waste (CO2, nitrogenous waste). Key organs include kidneys, ureters, bladder, and urethra. Kidneys contain millions of nephrons, the functional units for filtering blood and producing urine. Filtration begins in the glomerulus, encased in Bowman's capsule, where blood pressure pushes fluid (filtrate) containing water, glucose, amino acids, salts, ions, medications, and urea. The filtrate then undergoes intensive processing. Reabsorption involves specific filtrate components moving from the nephron back into interstitial fluid and recirculated. Secretion involves substances moving from interstitial fluid into the nephron. Passive transport follows a concentration gradient, while active transport requires ATP. The proximal convoluted tubule reabsorbs salt, water, glucose, amino acids, potassium, and bicarbonate; it secretes hydrogen ions and ammonium, regulating pH. The Loop of Henle has a descending limb (aquaporins, water reabsorption, salt retention) and an ascending limb (no aquaporins, salt exit passively then actively, dilutes filtrate). The distal convoluted tubule secretes hydrogen, potassium, and ammonium, while reabsorbing salts, water, and bicarbonate, further regulating pH. The collecting duct transforms filtrate into urine; water reabsorption here is tightly controlled by hormones (e.g., ADH in dehydration leads to more concentrated urine). Urea is also reabsorbed and secreted. Urine flows from kidneys to ureters, stored in the bladder, and expelled through the urethra.

The immune system defends against pathogens (viruses, bacteria, fungi, etc.). The first line of defense is non-specific external barriers like skin and mucous membranes. If breached, the second line of defense involves inflammatory responses. For example, a thorn prick introduces bacteria, activating mast cells to release histamine, which dilates blood vessels and increases permeability, allowing white blood cells (macrophages) to reach and engulf pathogens. The complement system enhances immune functions. This second line is also non-specific. The third line of defense is adaptive immunity, a more specific response targeting antigens (foreign substances). It has two types: cell-mediated and humoral. Cell-mediated immunity involves cytotoxic T cells destroying infected cells by inducing apoptosis (e.g., via perforin), halting pathogen replication. Helper T cells activate cytotoxic T cells and play a crucial role in both adaptive responses. Humoral immunity involves B cells producing antibodies. Antibodies (IgG, IgA, IgM, IgE, IgD) neutralize pathogens and mark them for destruction by macrophages. Memory B and T cells provide long-lasting immunity by remembering past antigens. Active immunity is acquired when the body produces its own antibodies (e.g., infection, vaccination), providing long-term protection. Passive immunity is receiving antibodies from another source (e.g., mother to baby, anti-serums), providing immediate but temporary protection.

The skeletal system supports the body, protects organs, stores minerals, produces blood cells, and enables movement with muscles. An adult has 206 bones. It's divided into axial (skull, ossicles, hyoid, vertebral column, rib cage) and appendicular (arms, shoulder girdle, legs, pelvic girdle). Bone shapes: long (cylindrical, longer than wide, for movement, e.g., femur, humerus), short (cube-shaped, length = width, for stability, e.g., carpals, tarsals), sesamoid (small, round, embedded in tendons, e.g., patella), flat (curved, thin, for protection, e.g., cranial bones, scapula), and irregular (complex shapes, e.g., vertebrae). Bone internal structures include compact bone (outer layer, hard) and spongy bone (inner, porous, contains red marrow for hematopoiesis - red/white blood cells, platelets - and yellow marrow for fat storage). Bones are vascular. Fractures can lead to internal bleeding or fat embolism syndrome (from yellow marrow). Intraosseous administration delivers medicine directly into bone marrow. Bone cells: osteoblasts (bone builders), osteocytes (maintain bone structure), osteoclasts (bone-resorbing cells, use enzymes/acids). Bone remodeling continuously replaces old bone: resting, resorption (osteoclasts break down bone), reversal, formation (osteoblasts lay new osteoid), mineralization (hardening). This process is vital for skeletal strength and calcium homeostasis. Chondroblasts produce cartilage, which supports bones (especially joints) and serves as a framework for fetal bone development. Fractures heal by forming a hematoma, then a callus (cartilage and bone) while osteoclasts remove damaged parts and osteoblasts build new bone. Fracture types: closed (simple), open (compound), comminuted (shattered), impacted (ends driven together), greenstick (bends/cracks, not through).

Common anatomical terms: Head (cephalic/cranial), face (facial/frontal/temporal/orbital/ocular/otic/buccal/nasal/oral/mental). Neck/Torso: cervical (neck), axillary (armpit), brachial (arm), antebrachial (forearm), carpal (wrist), palmar (palm), pollex (thumb), digital/phalanges (fingers), sternal (breastbone), thoracic (chest), mammary (breast), abdominal (abdomen), umbilical (navel). Anterior Lower Body: coxa (hip), femoral (thigh), patellar (front knee), crural (shin), pedal (foot), tarsal (ankle), digital/phalanges (toes), dorsum (top of foot), hallux (great toe), manual (hand), pelvic (pelvis), inguinal (groin), pubic (pubis). Posterior Body: occipital (base of skull), acromial (shoulder), scapular (shoulder blade), vertebral (spinal column), dorsal (back), olecranal/cubital (back of elbow), lumbar (loin), sacral (between hips), coccygeal (tailbone), gluteal (buttock), perineal (between anus and genitalia), popliteal (back of knee), sural (calf), plantar (sole of foot), calcaneal (heel). Anatomical planes: Transverse (horizontal, divides body into superior/inferior, allows rotational movement). Frontal/Coronal (divides into anterior/posterior, allows side-to-side movement like abduction/adduction). Sagittal/Lateral (divides into left/right, allows forward/backward movement like flexion/extension). Directional terms: Anterior (front), Posterior (back), Medial (closer to midline), Lateral (further from midline), Superior (above), Inferior (below), Proximal (closer to limb attachment), Distal (further from limb attachment).

The respiratory system facilitates air intake and gas exchange. Air enters through the nasal cavity, passes through the pharynx, larynx, and trachea (supported by cartilage rings), then branches into bronchi and bronchioles, eventually reaching alveoli for gas exchange. The conducting zone (trachea, bronchi, terminal bronchioles) warms, humidifies, and filters air without gas exchange, while the respiratory zone (respiratory bronchioles, alveolar ducts, alveoli) is where gas exchange occurs. The system collaborates with the circulatory, skeletal (rib cage protection), and muscular systems (intercostal muscles, diaphragm, abdominal muscles for breathing). Breathing is primarily involuntary, regulated by the nervous system based on blood pH levels, adjusting rate and depth to maintain homeostasis. Inspiration is an active process involving diaphragm and intercostal muscle contraction, expanding the thoracic cavity and drawing air in. Expiration is usually passive, involving muscle relaxation, reducing thoracic volume and expelling air. Ventilation is airflow in/out of lungs, and perfusion is blood flow to alveoli. Imbalances lead to hypoventilation (low oxygen, high CO2) or hyperventilation (high oxygen, low CO2).

The cardiovascular system transports blood, which is always red (dark or light depending on oxygenation), and maintains pH, temperature, and osmotic pressure. Blood consists of plasma (water, proteins, salts, lipids), red blood cells (gas transport), white blood cells (immune defense), and platelets (clotting). Hemoglobin gives blood its red color. Arteries carry blood away from the heart, and veins carry blood back; however, pulmonary arteries carry deoxygenated blood and pulmonary veins carry oxygenated blood. Capillaries facilitate gas exchange. The heart has four chambers: right atrium, right ventricle, left atrium, left ventricle. Atria walls are thinner than ventricular walls. Valves prevent backflow. Deoxygenated blood returns from the body via vena cava into the right atrium, then right ventricle, pumped to the lungs via the pulmonary artery. Oxygenated blood returns from the lungs to the left atrium, then left ventricle, and is pumped to the body via the aorta. Coronary arteries supply the heart itself with oxygenated blood. Septal defects involve abnormal openings between heart chambers, causing mixing of oxygenated and deoxygenated blood. The heart's electrical conduction system starts at the SA node (primary pacemaker), followed by AV node, bundle of His, bundle branches, and Purkinje fibers. The SA node sets the heart rate (60-100 bpm), with subsequent components having slower intrinsic rates for backup. ECG measures electrical activity: P-wave (atrial depolarization/contraction), QRS complex (ventricular depolarization/contraction, overshadowed atrial repolarization), T-wave (ventricular repolarization/relaxation). Systolic blood pressure is the peak arterial pressure during heart contraction, and diastolic is the lowest pressure during relaxation.

The nervous system comprises the central nervous system (CNS) with the brain and spinal cord, and the peripheral nervous system (PNS) with nerves throughout the body. The brain has a hindbrain (medulla oblongata, pons, cerebellum for vital functions, communication, balance), midbrain (alertness, sleep-wake, motor activities, reflexes), and forebrain (cerebrum with two hemispheres). The cerebrum, the largest part, features primary motor and sensory cortices for conscious control and processing. Gray matter (neuron cell bodies) processes information, while white matter (axons with myelin sheaths) transmits signals. Association areas enhance motor and sensory functions. The cerebral cortex is where conscious awareness emerges. The limbic system within the cerebrum is crucial for memory, emotion, and cognitive functions. Frontal, parietal, occipital, and temporal lobes each have specific roles (e.g., frontal for decision-making, occipital for vision, temporal for hearing). The PNS is divided into somatic (voluntary skeletal muscle control) and autonomic (involuntary internal environment regulation). The autonomic nervous system further divides into sympathetic (fight-or-flight) and parasympathetic (rest-and-digest). Neurons (cell body, dendrites, axon, axon terminal with synapse) transmit signals, while glial cells support neurons, maintain chemical balance, form myelin, and produce cerebrospinal fluid. Afferent neurons (sensory) carry signals to the CNS, and efferent neurons (motor) carry signals away from the CNS to muscles and glands.

The digestive system performs ingestion, digestion, absorption, and elimination. Ingestion starts in the mouth, where chemical digestion (salivary amylase for carbs) and mechanical digestion (chewing) begin. Saliva aids digestion, lubricates food (bolus), and protects teeth. The epiglottis covers the windpipe to prevent choking. Peristalsis moves the bolus down the esophagus to the stomach. The stomach holds about 2 liters, with highly acidic gastric juices (HCl, pepsin for proteins) and mechanical churning creating chyme. The lower esophageal sphincter prevents reflux, and the pyloric sphincter controls chyme release into the small intestine. The small intestine (duodenum, jejunum, ileum) is where digestion ends and absorption begins. The duodenum chemically digests chyme with enzymes from the pancreas and bile from the liver. The jejunum absorbs most nutrients via villi. The ileum absorbs B12, bile salts, and fat-soluble vitamins. The large intestine (ascending, transverse, descending colon) primarily absorbs water and salt, solidifying waste into stool for elimination. Accessory organs like the liver (metabolism, bile production), gallbladder (bile storage), and pancreas (pancreatic juices with enzymes, neutralizing chyme) are vital. Key hormones and enzymes include gastrin (stimulates gastric acid), cholecystokinin (digests fats/proteins, stimulates gallbladder/pancreas), secretin (regulates pH, stimulates bicarbonate), insulin (lowers blood sugar), glucagon (raises blood sugar), and bile (emulsifies fats).

The muscular system involves three types of muscle tissue. Cardiac muscle (heart) is branched, striated, involuntary, with single nuclei and intercalated discs for coordinated contractions. Smooth muscle (digestive system, arteries, bladder, eyes) is non-striated, spindle-shaped, involuntary, with single nuclei. Skeletal muscle (biceps, triceps) attaches to bones/skin, is striated, voluntary, with multiple nuclei, enabling rapid and forceful contractions. All muscle tissues exhibit extensibility (stretching), elasticity (returning to original shape), excitability (responding to stimuli), and contractility (contraction). Skeletal muscle contracts via the sliding filament model. Muscle fibers contain myofibrils, segmented into sarcomeres. Sarcomeres contain thin filaments (actin) and thick filaments (myosin). Myosin heads bind to ATP, hydrolyze it, bind to actin forming a crossbridge, release ADP, and perform a power stroke, pulling actin towards the sarcomere center. New ATP detaches myosin. Filaments slide past each other, shortening the sarcomere, but the filaments themselves do not shorten. Lack of ATP after death causes rigor mortis.

The reproductive system encompasses gonads (testes, ovaries), glands, ducts, external genitalia, and brain regions. Gonads produce sex hormones and gametes (sperm, eggs). Gametes are haploid cells produced via meiosis. Fertilization of sperm and egg forms a zygote, leading to embryonic development. The male reproductive system includes testes (produce testosterone, sperm via spermatogenesis in seminiferous tubules, stored in epididymis), scrotum (cooler temperature for sperm), vast deferens, ejaculatory duct, and urethra. The penis is the copulatory organ. Accessory glands: seminal glands (secrete semen for sperm motility/fertilizing ability), prostate gland (contracts during ejaculation, activates sperm), bulbourethral glands (lubricate glans penis). The female reproductive system includes ovaries (produce ova/egg cells via oogenesis, estrogen, progesterone), fallopian tubes (fertilization site), uterus (womb for implantation/development), cervix, and vagina (copulatory organ, birth canal). External genitalia (vulva) include mons pubis, labia majora, labia minora (enclosing vestibule with urethra and vagina orifices), and anus. Hormones (estrogen, progesterone, testosterone) from the endocrine system regulate reproductive development and function. Hypothalamus and pituitary gland control hormone release. Posterior pituitary releases oxytocin (uterine contractions) and ADH (water reabsorption). Anterior pituitary produces growth hormone, prolactin (milk production), TSH (thyroid), FSH (egg/sperm formation), LH (ovulation, androgens), ACTH (adrenal cortex).

The integumentary system, primarily the skin, is the largest organ and maintains homeostasis by regulating temperature and fluid balance. It acts as a physical barrier, protects from pathogens, synthesizes vitamin D, and provides sensory function. The epidermis consists of keratinocytes (produce keratin, harden, and move to surface) in layers: stratum corneum (dead, hardened cells), stratum lucidum (thick skin, transparent), stratum granulosum (flattening cells, granules), stratum spinosum (keratinocytes, Langerhans cells for immunity), and stratum basale (basal cells for mitosis, melanocytes for pigment, Merkel cells for touch). The dermis, made of connective tissue, contains blood vessels, sweat glands, nerves, and hair follicles; it is strengthened by collagen and elastin produced by fibroblasts. Scars (dermis cuts) differ from original skin due to collagen alignment and lack of accessory structures. Keloids are excessive collagen production. The hypodermis (subcutaneous layer) beneath the dermis connects skin to muscle/bone and is composed of adipose tissue for insulation. Accessory structures include sweat glands (cooling), sebaceous glands (oil for waterproofing/lubrication), hair follicles (hair growth), and nails (from nail root, protect fingertips). Skin cancer (basal cell carcinoma, melanoma, squamous cell carcinoma) is common, often due to UV exposure. Burns are classified by depth (1st, 2nd, 3rd, 4th degree), compromising skin function, fluid retention, protection, and increasing infection risk.