HESI A2 A&P flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Anatomical position

Standing erect, face and palms facing forward, feet flat and arms at the sides. All directional terms such as medial, proximal, and anterior are defined relative to this reference stance.

Dorsal body cavity

The posterior cavity containing the cranial cavity, which houses the brain, and the vertebral (spinal) canal, which houses the spinal cord. It is continuous and lined by meninges.

Diaphragm

Dome-shaped skeletal muscle separating the thoracic cavity from the abdominopelvic cavity. Its contraction flattens it during inspiration, increasing thoracic volume and lowering intrapulmonary pressure.

Epithelial tissue

Avascular tissue that covers surfaces and lines cavities and glands. Cells are tightly packed, rest on a basement membrane, and have an apical surface facing the lumen or exterior.

Connective tissue

Tissue characterized by cells scattered within an abundant extracellular matrix. Examples include bone, cartilage, adipose tissue, blood, and dense fibrous connective tissue such as tendons and ligaments.

Skeletal muscle

Voluntary, striated muscle attached to bones that produces body movement. It is multinucleated, contracts via the sliding filament mechanism, and fatigues more readily than cardiac muscle.

Cardiac muscle

Involuntary, striated muscle found only in the heart wall. Cells are branched, joined by intercalated discs with gap junctions, and generate rhythmic contractions without nervous input.

Smooth muscle

Involuntary, nonstriated muscle in the walls of hollow organs, blood vessels, and the digestive tract. It contracts slowly and sustains tone, producing peristalsis and regulating vessel diameter.

Negative feedback

A control mechanism in which the response reverses the original deviation, restoring the set point. Examples include thermoregulation, insulin lowering blood glucose, and baroreflex control of blood pressure.

Positive feedback

A control mechanism in which the response amplifies the initial stimulus, driving a process to completion. Examples include oxytocin release during labor and thrombin activation in blood clotting.

Osmosis

Passive movement of water across a semipermeable membrane from a region of lower solute concentration to one of higher solute concentration. It requires no ATP and equalizes osmolarity.

Na+/K+ pump

Primary active transport protein using ATP to move three sodium ions out of the cell and two potassium ions in. It maintains the resting membrane potential and cell volume.

Mitochondrion

Membrane-bound organelle with folded cristae where aerobic respiration and oxidative phosphorylation occur. It produces most of the cell's ATP and contains its own DNA.

Ribosome

Small RNA-protein complex that assembles amino acids into polypeptides during translation. Free ribosomes make cytosolic proteins; ribosomes on the rough ER make secreted and membrane proteins.

Golgi apparatus

Stack of flattened membranous sacs that modifies, sorts, and packages proteins and lipids received from the endoplasmic reticulum, then ships them in vesicles to destinations.

Lysosome

Membrane-bound vesicle containing hydrolytic enzymes that digest worn organelles, engulfed material, and macromolecules. Its interior is acidic, and it is abundant in phagocytic cells.

Mitosis

Nuclear division producing two genetically identical diploid daughter cells, proceeding through prophase, metaphase, anaphase, and telophase. It underlies growth, repair, and replacement of somatic cells.

Meiosis

Two successive nuclear divisions producing four haploid gametes with genetic recombination through crossing over and independent assortment. It halves chromosome number and creates genetic variation.

Resting membrane potential

The voltage across a resting neuron's membrane, about -70 millivolts inside relative to outside. It is maintained mainly by potassium leak channels and the sodium-potassium pump.

Osteoclast

Large multinucleated bone cell that resorbs bone matrix by secreting acid and enzymes. It works opposite osteoblasts and is stimulated by parathyroid hormone during calcium mobilization.

Osteoblast

Bone-forming cell that synthesizes and secretes collagen and mineralizes new bone matrix. Osteoblasts become osteocytes when trapped in matrix and are stimulated by calcitonin.

Sarcomere

The functional contractile unit of a muscle fiber, extending between two Z lines. Actin thin filaments slide over myosin thick filaments to shorten it during contraction.

Sliding filament theory

Explanation of muscle contraction in which calcium binds troponin, tropomyosin shifts, and myosin heads bind actin and pull thin filaments toward the sarcomere center, shortening the fiber.

SA node

The sinoatrial node in the right atrial wall, the heart's natural pacemaker. It spontaneously depolarizes, setting the intrinsic heart rate, and its impulse spreads to the AV node.

Cardiac output

The volume of blood pumped by one ventricle per minute, calculated as heart rate multiplied by stroke volume. Typical resting value is about five liters per minute.

Hematocrit

The percentage of blood volume occupied by red blood cells after centrifugation, normally about 45 percent. Plasma forms the remaining portion and contains proteins and dissolved solutes.

Universal donor

Type O negative red blood cells, which lack A, B, and Rh antigens and therefore are not attacked by recipient antibodies in an emergency transfusion.

Hemoglobin

Iron-containing protein in red blood cells that binds oxygen in the lungs and releases it in tissues. Each molecule carries up to four oxygen molecules and also transports some carbon dioxide.

Surfactant

Lipoprotein secreted by alveolar type II cells that lowers surface tension in the alveoli, preventing collapse during expiration and reducing the work of breathing.

Villi

Fingerlike projections of the small intestinal mucosa containing capillaries and a lacteal. Together with microvilli, they greatly increase surface area for nutrient absorption.

Glomerular filtration

First step of urine formation in which hydrostatic pressure forces water and small solutes from blood in the glomerulus into Bowman's capsule, excluding cells and large proteins.

Insulin

Hormone secreted by pancreatic beta cells that lowers blood glucose by promoting cellular uptake and glycogen storage. Deficiency or resistance produces hyperglycemia characteristic of diabetes mellitus.