Organization of the Body, Homeostasis and Anatomical Terminology: every key term you need (+ practice quiz)
25 flashcard terms for Anatomy & Physiology I Topic 1, written to match the course framework. Study them here, then drill them as interactive flashcards, or test yourself with the 15-question quiz — free, no account needed.
The study of body structures and the spatial relationships among them. It asks what a part is made of, where it sits, and how it is shaped, and it supplies the vocabulary that physiology then uses to explain function.
Physiology
The study of how living structures work: the chemical, electrical and mechanical processes that keep cells, organs and systems operating. Physiology explains why a structure behaves as it does under normal and stressed conditions.
Complementarity of structure and function
The organizing principle that what a structure can do is limited by its form. Flattened alveolar cells permit rapid gas diffusion; thick ventricular walls permit high-pressure ejection. Form is read as evidence of function.
Gross anatomy
Anatomy studied at a scale visible without magnification, through dissection, imaging or surface inspection. It is subdivided into regional, systemic and surface approaches depending on how the material is organized.
Histology
Microscopic anatomy of tissues, examined in stained sections under a light or electron microscope. It bridges cell biology and gross anatomy by showing how cells and matrix are arranged into functional sheets, bundles and layers.
Levels of structural organization
The nested hierarchy running from chemical to cellular, tissue, organ, organ system and finally organism. Each level acquires properties absent at the level below, which is why an organ can do what its isolated cells cannot.
Homeostasis
The maintenance of a relatively stable internal environment despite changing external conditions. It is dynamic rather than static: variables such as temperature, pH and glucose oscillate within a narrow tolerable range around a target value.
Set point
The target value a regulated variable is held near, such as roughly thirty-seven degrees Celsius for core temperature. Set points can be reset physiologically, as when pyrogens raise the thermal target during fever.
Negative feedback
A control loop in which the response opposes the original change, driving the variable back toward its set point. It stabilizes most regulated variables, including blood glucose, osmolarity, blood pressure and body temperature.
Positive feedback
A loop in which the response amplifies the original change, pushing the variable further from its starting value until an outside event ends the cycle. Examples include oxytocin in labor, platelet plug formation and the upstroke of an action potential.
Homeostatic receptor
The sensor limb of a control loop. It detects the value of a regulated variable and sends afferent information to the control center. Thermoreceptors, baroreceptors and osmoreceptors are common examples.
Control center
The integrating element of a homeostatic loop, usually a brain region or endocrine gland. It compares incoming sensory information against the set point and issues efferent commands proportional to the size of the error.
Effector
The structure that carries out the corrective response ordered by the control center. Sweat glands, arteriolar smooth muscle, skeletal muscle and hormone-secreting cells all act as effectors in different loops.
Anatomical position
The standard reference posture: standing erect, feet slightly apart and flat on the floor, head and eyes facing forward, arms at the sides with palms turned anteriorly. All directional terms assume this posture regardless of the actual body position.
Supine and prone
Two terms for a body lying horizontally. Supine describes lying face upward, with the anterior surface uppermost; prone describes lying face downward, with the posterior surface uppermost.
Sagittal plane
A vertical plane dividing the body into right and left portions. The midsagittal or median plane passes through the midline and yields equal halves, while a parasagittal plane lies off-center and yields unequal ones.
Frontal plane
A vertical plane, also called coronal, that divides the body into anterior and posterior portions. It runs at right angles to the sagittal plane and is the plane in which abduction and adduction occur.
Transverse plane
A horizontal plane dividing the body into superior and inferior portions, producing the cross sections seen on a standard computed tomography image. It is sometimes called an axial or horizontal plane.
Proximal and distal
Paired directional terms used along a limb. Proximal means closer to the point of attachment to the trunk, distal means farther from it, so the elbow is proximal to the wrist and distal to the shoulder.
Superficial and deep
Directional terms describing distance from the body surface. Superficial structures lie nearer the surface, deep structures lie farther inward, so the epidermis is superficial to the muscles of the abdominal wall.
Dorsal body cavity
The posterior cavity enclosing the central nervous system. It comprises the cranial cavity, which houses the brain within the skull, and the vertebral canal, which houses the spinal cord within the vertebral column.
Ventral body cavity
The anterior cavity housing the viscera, divided by the diaphragm into a thoracic cavity above and an abdominopelvic cavity below. Its subdivisions are lined by serous membranes that reduce friction during organ movement.
Serous membrane
A double-layered membrane whose parietal layer lines a cavity wall and whose visceral layer covers the organ, separated by a thin film of lubricating serous fluid. Pleura, pericardium and peritoneum follow this pattern.
Mediastinum
The central compartment of the thoracic cavity lying between the two pleural sacs. It contains the heart in its pericardial sac along with the great vessels, trachea, esophagus, thymus and associated nerves.
Abdominopelvic quadrants
A clinical scheme dividing the abdomen into four regions by a vertical and a horizontal line crossing at the umbilicus, used to localize pain. Appendicitis classically presents in the right lower quadrant.