Anatomy and Physiology: Tissues - Structure, Classification, Membranes, and Repair

Comprehensive vocabulary flashcards covering histological classification, epithelial and connective tissues, cell junctions, gland functions, muscle and nervous tissues, body membranes, tissue healing, aging, and neoplasia based on Chapter 5 lecture notes.

Histology

The microscopic study of the appearance, function, and organization of tissues.

Pathology

The study of changes in tissues and organs that occur with disease.

Levels of Structural Organization

The biological hierarchy ranging from atoms and molecules at the chemical level, to cells, tissues, organs, organ systems, and the complete organismal level.

Cellular Connections

Specialized contact points between cells, consisting of tight junctions that fuse membranes, desmosomes that provide flexible mechanical attachment, hemidesmosomes anchoring cells to the extracellular matrix, and gap junctions that establish intercellular passageways.

Tight Junctions

Intercellular connections that fuse the plasma membranes of adjacent cells together, preventing fluid leakage between them.

Desmosomes

Intercellular junctions that anchor neighboring cells together to provide strong, flexible connections.

Hemidesmosomes

Specialized cell junctions that attach epithelial cells to the underlying extracellular matrix and basement membrane.

Gap Junctions

Protein channels between adjacent cells that allow direct intercellular passage of ions, nutrients, and signaling molecules.

Epithelial Tissue

One of the four primary tissue classes; composed of tightly packed, avascular cells that form body coverings, luminal linings, and secretory glands.

Basement Membrane

An extracellular layer consisting of the lamina lucida and lamina densa that anchors an epithelium to underlying connective tissue.

Apical Surface

The free or exposed surface of an epithelium facing an open body cavity, lumen, or the external environment.

Basal Surface

The lower anchored surface of an epithelium that directly adheres to the basement membrane.

Apical Surface Modifications

Structural specializations of the epithelial apical membrane, including motile cilia that sweep substances across surfaces and microvilli that expand surface area for absorption.

Cilia

Elongated, motile cellular projections on the apical surface of certain epithelia that move mucus and other materials across the cell surface.

Microvilli

Non-motile, finger-like extensions of the apical plasma membrane that significantly increase epithelial surface area for absorption and secretion.

Simple Epithelium

An epithelial tissue made up of a single layer of cells, all of which rest directly on the basement membrane.

Stratified Epithelium

An epithelial tissue comprising two or more cell layers, primarily specialized for protection against mechanical, chemical, and environmental wear.

Squamous Cells

Thin, flattened epithelial cells.

Cuboidal Cells

Box-shaped, cube-like epithelial cells with roughly equal height and width.

Columnar Cells

Tall, rectangular, column-shaped epithelial cells whose height exceeds their width.

Pseudostratified Columnar Epithelium

A single layer of columnar cells of varying heights whose nuclei appear at different levels; all cells touch the basement membrane, and ciliated forms line the trachea and upper respiratory tract to secrete and move mucus.

Transitional Epithelium

A stratified epithelium lining the urinary bladder, ureters, and urethra whose cells stretch and alter their shape to accommodate organ volume changes.

Goblet Cells

Unicellular exocrine glands distributed within simple columnar and pseudostratified epithelia that synthesize and secrete lubricating mucus.

Simple Squamous Epithelium

A single layer of flattened cells lining the air sacs of the lungs, heart, blood vessels, and lymphatic vessels; functions in rapid diffusion, filtration, and secreting lubricating fluid.

Simple Cuboidal Epithelium

A single layer of box-shaped cells that lines kidney tubules and small glandular ducts; active in secretion and absorption.

Simple Columnar Epithelium

A single layer of tall cells lining the digestive and reproductive tracts; functions in absorption as well as the secretion of mucus and digestive enzymes.

Stratified Squamous Epithelium

A multi-layered tissue whose surface cells are flattened; lines the esophagus, mouth, and vagina to protect underlying tissues against abrasion.

Stratified Cuboidal Epithelium

A rare multi-layered epithelium featuring cube-shaped cells; found in ducts of sweat glands, salivary glands, and mammary glands to secrete and protect.

Stratified Columnar Epithelium

A multi-layered epithelium with columnar apical cells found in the male urethra and ducts of certain glands; provides secretion and protection.

Gland

One or more specialized epithelial cells that synthesize and secrete an aqueous fluid called a secretion.

Endocrine Glands

Ductless glands that secrete chemical regulatory messengers called hormones directly into blood or lymph (e.g., pituitary gland, thymus, adrenal glands).

Exocrine Glands

Glands that release secretions (such as mucus, sweat, saliva, or breast milk) through epithelial-lined ducts directly onto an apical surface.

Multicellular Exocrine Gland Structures

Glandular architectures classified by duct pattern (simple with one unbranched duct vs. compound with branched ducts) and secretory unit geometry (tubular forming tubes vs. acinar forming sac-like pockets).

Merocrine Secretion

A secretory process in which products are enclosed within vesicles and discharged across the plasma membrane by exocytosis without cellular loss.

Apocrine Secretion

A mode of secretion in which the secretory product concentrates at the cell apex and is released along with a pinched-off portion of the apical cytoplasm.

Holocrine Secretion

A mode of secretion where the entire mature gland cell disintegrates and dies, releasing its accumulated contents into the lumen to become the secretory product.

Serous Glands

Exocrine glands that produce thin, watery secretions.

Mucous Glands

Exocrine glands that secrete viscous, mucus-rich fluids.

Mesenchyme

The embryonic tissue of origin from which all connective tissue classes develop.

Extracellular Matrix (ECM)

The largely nonliving material separating connective tissue cells, consisting of ground substance and structural protein fibers, which enables tissues to bear weight and withstand tension.

Ground Substance

The unstructured material filling the spaces between cells and fibers in connective tissue, serving as a diffusion medium for solutes passing between capillaries and cells.

Collagen Fibers

Tough, highly abundant protein fibers composed of collagen that impart high tensile strength to connective tissues.

Elastic Fibers

Networks of long, slender fibers containing the protein elastin that allow tissues to stretch and recoil.

Reticular Fibers

Short, fine, highly branched collagenous fibers that interweave into supportive structural networks (stroma) offering give in soft tissues and organs.

"Blast" Cells

Immature, mitotically active connective tissue cells (such as fibroblasts, chondroblasts, and osteoblasts) responsible for secreting ground substance and fibers.

"Cyte" Cells

Mature connective tissue cells (such as chondrocytes and osteocytes) that monitor, maintain, and sustain the extracellular matrix.

Mast Cells

Connective tissue cells that detect foreign microorganisms and initiate a local inflammatory response through chemical mediator release (such as histamine).

Macrophages

Phagocytic cells of connective tissue and the immune system that engulf cellular debris, foreign microorganisms, and dead cells.

Areolar Connective Tissue

A loose connective tissue located in the subcutaneous layer with loosely arranged collagen and elastin fibers; provides a water and salt reservoir and soaks up excess fluid when inflamed.

Adipose Tissue

A loose, richly vascularized connective tissue dominated by lipid-storing adipocytes with a sparse extracellular matrix; provides energy storage, cushioning, and insulation.

Reticular Connective Tissue

A loose connective tissue featuring reticular cells and fibers that forms a supportive internal stroma in lymph nodes, the spleen, liver, and bone marrow.

Elastic Connective Tissue

A dense connective tissue with a high proportion of elastic fibers, located in the walls of large arteries and ligaments stabilizing adjacent vertebrae.

Dense Regular Connective Tissue

A poorly vascularized connective tissue containing tightly packed, parallel bundles of collagen fibers that resists mechanical pull along a single axis (found in tendons and ligaments).

Dense Irregular Connective Tissue

A connective tissue packed with thick collagen fiber bundles oriented haphazardly in all directions, permitting it to withstand forces exerted from various planes (found in the dermis and joint capsules).

Cartilage

An avascular, aneural supportive connective tissue containing chondrocytes within lacunae, comprised of up to $80\%$ water that enables it to rebound after compressive loading.

Hyaline Cartilage

The most abundant cartilage type in the human body; covers the articular ends of bones in synovial joints, forms the costal cartilages of ribs, and reinforces the nose.

Fibrocartilage

The strongest cartilage type, characterized by dense collagen fibers; located in the intervertebral discs, pubic symphysis, and knee menisci.

Elastic Cartilage

The most pliable cartilage type, enriched with elastic fibers; maintains structural shape in the external ear and epiglottis.

Compact Bone

A dense, solid, richly vascularized form of osseous tissue that provides robust structural support and protection for internal organs.

Spongy Bone

A porous form of osseous tissue containing empty spaces filled with red bone marrow, the primary site of blood cell synthesis.

Blood

An atypical fluid connective tissue consisting of erythrocytes, leukocytes, and platelets suspended in liquid plasma, with soluble protein fibers that precipitate during clotting.

Lymph

A predominantly acellular fluid connective tissue derived from excess extracellular fluid, transported through lymphatic vessels to support immune defense.

Muscle Tissue Types

Contractile tissues responsible for pulling forces and movement: skeletal muscle (voluntary, striated, multinucleated), cardiac muscle (involuntary, striated, branched, uninucleated), and smooth muscle (involuntary, non-striated, tapered ends, uninucleated).

Skeletal Muscle

Voluntary muscle tissue attached to bones and body orifices; characterized by long, cylindrical, striated cells with multiple peripherally located nuclei that generate body movement and heat.

Cardiac Muscle

Involuntary muscle tissue restricted to the heart wall; consists of branched, striated cells with a single nucleus that contract to force blood out of heart chambers.

Smooth Muscle

Involuntary, non-striated muscle tissue with spindle-shaped, uninucleated cells lining hollow internal organs and blood vessels to regulate blood flow and propel luminal contents.

Nervous Tissue Anatomy

Excitable communication tissue comprising neurons that transmit action potentials and supportive neuroglial cells (such as oligodendrocytes) that insulate axons to facilitate rapid signal conduction.

Neurons

Excitable nervous tissue cells that transmit electrical impulses down their axons and release chemical signals to communicate with neighboring cells.

Glial Cells

Non-excitable supporting cells in nervous tissue that protect, nourish, and insulate neurons (such as myelinating oligodendrocytes).

Cutaneous Membrane

The dry epithelial membrane covering the external surface of the body (the skin); composed of a keratinized stratified squamous epithelium (epidermis) bound to underlying connective tissue (dermis).

Mucous Membranes (Mucosae)

Moist epithelial membranes lining internal cavities open to the external environment (digestive, respiratory, urinary, and reproductive tracts) that are bathed in secretions or urine.

Serous Membranes (Serosae)

Double-layered, moist membranes lining closed ventral body cavities and covering visceral organs (e.g., pericardium, pleura, peritoneum); lubricated by serous fluid to minimize friction.

Parietal Serosa

The outer layer of a serous membrane that adheres to and lines the interior walls of a closed body cavity.

Visceral Serosa

The inner layer of a serous membrane that adheres directly to the external surface of organs housed within a closed body cavity.

Serous Membrane Balloon Analogy

A anatomical concept illustrating how an organ pushes into a closed serous sac during development, analogous to a fist indenting an underinflated balloon to create an inner visceral layer and an outer parietal layer separated by a narrow fluid-filled cavity.

Synovial Membranes

Connective tissue membranes lining the interior joint capsules of freely moving articulations; produce synovial fluid that lubricates the joint and nourishes articular cartilage.

Meninges

A protective set of three connective tissue membranes that enclose the brain and spinal cord, bathing these central nervous organs in cerebrospinal fluid (CSF).

Regeneration

A tissue repair mechanism where destroyed cells are replaced by the same original cell type, fully restoring normal tissue function.

Fibrosis

A tissue repair process wherein damaged tissue is replaced by dense connective (scar) tissue composed of hastily woven collagen fibers, resulting in a loss of original function.

Granulation Tissue

A rapidly vascularized, temporary connective tissue layer formed during wound healing that serves as a foundation for migrating epithelial cells to cover the wound.

Inflammation

The body's immediate protective response to injury that restricts damage and initiates healing; characterized by histamine release, increased capillary permeability, and leukocyte recruitment.

Benign Tumor

A non-cancerous mass of proliferating cells that does not invade adjacent tissues or metastasize to other body sites.

Malignant Tumor

A cancerous mass of cells that exhibits uncontrolled proliferation, invades neighboring tissues, causes systemic disease, and can metastasize to distant anatomical sites.