Human Anatomy and Physiology I - Introduction and Tissues

Flashcards summarizing human anatomy and physiology concepts, organ systems, homeostasis, body regions, directional terms, planes, cavities, cell junctions, and tissue classifications.

Anatomy

The study of the body's structure.

Physiology

The study of the body's function.

Histology

The microscopic study of tissues.

Metabolism

The sum of all chemical processes that occur in the body, consisting of catabolism (the breakdown of complex substances) and anabolism (the building up of complex substances).

Homeostasis

The maintenance of key physiological parameters within a narrow range, such as normal body temperature ($36.2^\circ\text{C} - 37.5^\circ\text{C}$), blood glucose ($70 - 110\,\text{mg}/100\,\text{mL}$ blood), and blood pH ($\text{pH } 7.3 - \text{pH } 7.5$).

Interstitial Fluid

The extracellular fluid that fills the narrow spaces between tissue cells.

Blood Plasma

The fluid portion of extracellular fluid located within blood vessels.

Negative Feedback System

A homeostatic control mechanism that reverses a change in a controlled condition to return the system to normal (e.g., lowering elevated blood pressure via baroreceptor signals to the brain that slow heart rate and dilate blood vessels).

Positive Feedback System

A control mechanism that strengthens or reinforces a change in a controlled condition, temporarily driving the variable further away from homeostasis (e.g., cervical stretch triggering oxytocin release during labor to cause stronger uterine contractions).

Disorder

Any abnormality of structure and/or function in the body.

Disease

A specific illness or disorder characterized by a recognizable set of signs and symptoms.

Sign vs. Symptom

A sign is an objective, observable change that can be measured or evaluated by an observer; a symptom is a subjective change experienced by the patient that is not directly observable by others.

Anatomical Position

A standard position of reference in which the body stands upright and erect, facing forward, with feet flat on the floor and palms facing outward.

Supine vs. Prone

Supine describes a body reclining face up; prone describes a body reclining face down.

Sagittal Plane

A vertical plane that divides the body or an organ into right and left sides; includes midsagittal (directly along the midline) and parasagittal (unequal right and left portions) planes.

Frontal (Coronal) Plane

A plane that divides the body or an organ into anterior (front) and posterior (back) portions.

Transverse Plane

A horizontal plane that divides the body or an organ into superior (upper) and inferior (lower) portions.

Serous Membrane

A thin, double-layered membrane lining closed internal body cavities and covering organs, composed of a parietal layer (lining cavity wall), visceral layer (covering organ surface), and a fluid-filled serous cavity.

Mediastinum

The central anatomical space in the thoracic cavity extending from the sternum to the vertebral column between the lungs, containing all thoracic viscera except the lungs themselves.

Retroperitoneal Organs

Organs located behind the parietal peritoneum against the posterior abdominal wall, remembered by the mnemonic SAD PUCKER (Suprarenal glands, Aorta/IVC, Duodenum, Pancreas, Ureters, Colon, Kidneys, Esophagus, Rectum).

Tight Junctions

Web-like networks of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to prevent fluid leakage between epithelial cells.

Desmosomes

Cell junctions composed of protein plaques and cadherins attached to keratin intermediate filaments in adjacent cells, forming spot-weld-like anchors against mechanical tension.

Gap Junctions

Cellular connections formed by fluid-filled protein tubes called connexons that connect adjacent cells, allowing ions and small molecules to move directly between cytoplasms.

Epithelial Tissue

A basic tissue type consisting of closely packed cells arranged in continuous single or multiple layers attached to a basement membrane, featuring little to no extracellular matrix and no blood vessels.

Basement Membrane

A thin extracellular structure consisting of a basal lamina and reticular lamina that anchors an epithelium to underlying connective tissue.

Simple Squamous Epithelium

A single layer of flat, tile-like cells with central nuclei, specialized for filtration, diffusion, and secretion in serous membranes, blood vessels, and lung air sacs.

Simple Cuboidal Epithelium

A single layer of cube-shaped cells with central round nuclei, functioning in secretion and absorption within kidney tubules and small gland ducts.

Non-ciliated Simple Columnar Epithelium

A single layer of non-ciliated rectangular cells with basal nuclei, containing absorptive cells with microvilli and goblet cells, lining the GI tract from stomach to anus.

Ciliated Simple Columnar Epithelium

A single layer of rectangular ciliated cells with basal oval nuclei, functioning to move mucus and other materials via ciliary action in uterine tubes and airways.

Pseudostratified Columnar Epithelium

An epithelial tissue that appears stratified because nuclei lie at different levels, though all cells touch the basement membrane; commonly ciliated with goblet cells in upper respiratory airways.

Stratified Squamous Epithelium

A multi-layered tissue with flat apical cells and cuboidal/columnar basal cells, providing protection against abrasion in keratinized form (skin) or non-keratinized form (mouth, esophagus, vagina).

Transitional Epithelium

A stratified epithelium with variable apical cell shape (ranging from cuboidal when relaxed to squamous when stretched) that allows distension in the urinary bladder lining.

Endocrine Gland

A ductless gland that secretes hormones into interstitial fluid, which then diffuse directly into the blood stream to regulate body activities.

Exocrine Gland

A gland that secretes non-hormonal products (such as sweat, oil, wax, saliva, or enzymes) into ducts that empty onto covering/lining epithelium.

Eccrine (Merocrine) Gland

An exocrine gland that releases its secretory product via exocytosis from secretory vesicles without damaging or losing any part of the cell (e.g., salivary glands).

Apocrine Gland

An exocrine gland in which the secretory product gathers at the apical surface of the cell, which then pinches off from the remainder of the cell to release the secretion (e.g., mammary glands).

Holocrine Gland

An exocrine gland that accumulates secretory product in the cytosol; as the cell matures, it ruptures completely to release the secretion (e.g., sebaceous glands).

Connective Tissue

A widely distributed tissue composed of sparse cells embedded within an abundant extracellular matrix (ground substance and protein fibers), functioning to support, bind, insulate, and protect body organs.

Fibroblasts

Large, flat, active connective tissue cells that synthesize and secrete the fibers and ground substance of the extracellular matrix.

Glycosaminoglycans (GAGs)

Complex polysaccharides in ground substance (such as hyaluronic acid) that trap water to make connective tissue matrix fluid, viscous, or supportive.

Areolar Connective Tissue

A loose connective tissue consisting of collagen, elastic, and reticular fibers and multiple cell types in a semi-fluid ground substance, found in the subcutaneous layer to provide strength and elasticity.

Adipose Tissue

A loose connective tissue made of specialized fat-storing cells (adipocytes) that reduces heat loss, stores energy reserves, and cushions body organs.

Reticular Connective Tissue

A loose connective tissue consisting of a meshwork of thin reticular fibers and reticular cells that forms the internal structural framework (stroma) of organs like the spleen and lymph nodes.

Dense Regular Connective Tissue

A dense connective tissue dominated by parallel bundles of collagen fibers with rows of fibroblasts in between, providing strong unidirectional attachment in tendons and ligaments.

Dense Irregular Connective Tissue

A dense connective tissue containing randomly arranged collagen fibers and scattered fibroblasts, providing multidirectional strength in the dermis and organ capsules.

Elastic Connective Tissue

A dense connective tissue predominantly formed of branching elastic fibers and fibroblasts, enabling stretch and recoil in lung tissue, bronchial tubes, and arterial walls.

Hyaline Cartilage

The most abundant cartilage type, featuring a glossy, smooth matrix with fine collagen fibers and chondrocytes residing in lacunae; provides flexibility and low-friction movement at joints.

Fibrocartilage

A tough cartilage with prominent, visible collagen fiber bundles and chondrocytes in lacunae, providing shock absorption and support in intervertebral discs and the pubic symphysis.

Elastic Cartilage

A flexible cartilage containing a dense network of threadlike elastic fibers surrounding chondrocytes in lacunae, maintaining structural shape in the auricle of the ear and epiglottis.

Compact (Cortical) Bone

An osseous tissue consisting of osteocytes in lacunae surrounded by calcified extracellular matrix arranged in concentric rings (lamellae) around central blood vessel canals.

Mucous Membrane

An epithelial membrane lining body cavities that open directly to the exterior, composed of surface epithelium over an areolar connective tissue layer called the lamina propria.

Synovial Membrane

A membrane composed purely of connective tissue (lacking epithelium) that lines joint cavities of freely movable joints and secretes lubricating synovial fluid.

Skeletal Muscle Tissue

Voluntary muscle tissue consisting of long, cylindrical, striated fibers with multiple peripherally located nuclei, attached primarily to bones.

Cardiac Muscle Tissue

Involuntary heart muscle consisting of branched, striated fibers with central nuclei and intercalated discs that connect adjacent cells.

Smooth Muscle Tissue

Involuntary muscle tissue composed of non-striated, spindle-shaped fibers with a single central nucleus, located in the walls of hollow organs and blood vessels.

Neuron

An excitable nerve cell consisting of a cell body, dendrites, and an axon that converts stimuli into nerve impulses and conducts them to other cells.

Neuroglia

Non-conductive supporting cells in nervous tissue that protect, nourish, and support neurons.

Parenchyma vs. Stroma

Parenchyma consists of the functional cells of an organ or tissue (enabling tissue regeneration); stroma consists of supporting connective tissue framework cells (division leads to scar tissue/fibrosis).