Histology and Tissue Types Flashcards

A comprehensive vocabulary flashcard set covering histology concepts, including tissue categories, cell junctions, epithelial types, gland secretions, connective tissue cells and fibers, tissue membranes, muscle types, nervous cells, and tissue repair mechanisms.

Histology

The study of tissues, which are collections of specialized cells and cell products that perform specific functions.

Epithelial Tissue

A primary tissue type that covers exposed surfaces, lines internal passageways and chambers, and forms glands.

Connective Tissue

A primary tissue type that fills internal spaces, provides structural support, transports materials, and stores energy.

Muscle Tissue

A primary tissue type specialized for contraction to produce movement.

Nervous Tissue

A primary tissue type specialized for propagating electrical impulses and carrying information.

Epithelia

Layers of cells covering internal or external surfaces.

Glands

Structures composed of epithelial cells that produce fluid secretions.

Apical Surface

The surface of an epithelial cell facing the exterior or internal space, which may feature microvilli to increase absorption/secretion or cilia to move fluids.

Cell Adhesion Molecules (CAMs)

Transmembrane proteins that hold cells together by connecting opposing plasma membranes.

Proteoglycans

Intercellular cement containing glycosaminoglycans such as hyaluronan (hyaluronic acid) that helps hold opposing cell membranes together.

Gap Junctions

Intercellular connections formed by interlocking transmembrane proteins called connexons that permit rapid communication and free diffusion of ions and small molecules between cells.

Tight Junctions

Junctions formed by the fusion of outer plasma membrane layers that encircle apical cell portions, attached to the adhesion belt and terminal web, preventing the passage of water and solutes.

Spot Desmosome

A junction formed by densely packed CAMs and proteoglycans linked to intermediate filaments that ties adjacent cells together while allowing bending and twisting.

Hemidesmosome

A junctional structure that attaches an epithelial cell to extracellular structures, such as protein fibers in the basement membrane.

Basal Lamina

The layer of the basement membrane closest to the epithelium, composed of a disorganized extracellular matrix layer secreted by the epithelium.

Reticular Lamina

The deeper portion of the basement membrane, consisting mostly of reticular fibers and ground substance secreted by underlying connective tissue to provide strength.

Simple Squamous Epithelium

A single layer of thin, flat cells that reduces friction, controls vessel permeability, and performs absorption and secretion.

Mesothelium

Simple squamous epithelium lining the pleural, pericardial, and peritoneal body cavities.

Endothelium

Simple squamous epithelium forming the inner lining of the heart and blood vessels.

Stratified Squamous Epithelium

Multiple layers of flat cells that protect against mechanical stresses, abrasion, pathogens, and chemical attack.

Simple Cuboidal Epithelium

A single layer of square-shaped cells located in glands, ducts, thyroid gland, and kidney tubules, functioning in limited protection, secretion, and absorption.

Stratified Cuboidal Epithelium

A rare epithelium found in ducts of sweat glands and mammary glands that provides protection, secretion, and absorption.

Transitional Epithelium

Epithelium found in the urinary bladder, renal pelvis, and ureters that tolerates repeated cycles of stretching without damage, appearing cuboidal when relaxed and squamous when stretched.

Simple Columnar Epithelium

A single layer of tall, slender rectangular cells that lines the stomach, intestine, gallbladder, uterine tubes, and collecting ducts of kidneys, functioning in protection, secretion, and absorption.

Pseudostratified Ciliated Columnar Epithelium

Epithelium lining the nasal cavity, trachea, and bronchi where nuclei exist at multiple levels but every cell attaches to the basement membrane; functions to protect, secrete, and move mucus with cilia.

Stratified Columnar Epithelium

A rare tissue providing protection in small areas of the pharynx, epiglottis, anus, mammary glands, salivary gland ducts, and urethra.

Endocrine Glands

Ductless glands that release hormones directly into the bloodstream.

Exocrine Glands

Glands that discharge secretions through ducts onto epithelial surfaces.

Merocrine Secretion

A secretion method where products are released from secretory vesicles at the apical surface of gland cells by exocytosis (e.g., merocrine sweat glands).

Apocrine Secretion

A secretion method involving the loss of apical cytoplasm filled with secretory vesicles, after which the cell repairs itself (e.g., mammary glands).

Holocrine Secretion

A secretion method where superficial gland cells burst to release contents, destroying the cell, which is then replaced by underlying stem cells (e.g., sebaceous glands).

Extracellular Matrix (ECM)

The non-cellular material surrounding cells, composed of extracellular protein fibers and ground substance, determining tissue function.

Fibroblasts

The most abundant cell type in connective tissue proper; secretes proteins and hyaluronic acid.

Fibrocytes

The second most abundant cell type in connective tissue proper; responsible for maintaining connective tissue fibers.

Mesenchymal Cells

Stem cells present in connective tissue that respond to injury or infection by differentiating into fibroblasts, macrophages, and other cells.

Mast Cells

Connective tissue cells that stimulate inflammation after injury or infection by releasing histamine and heparin.

Collagen Fibers

The most common protein fibers in connective tissue proper; long, straight, unbranched fibers that are strong, flexible, and resist force in one direction.

Reticular Fibers

Thin, highly branched protein fibers forming an interwoven network (stroma) that stabilizes functional cells (parenchyma) within organs.

Elastic Fibers

Branched and wavy connective tissue fibers containing elastin that return to their original length after stretching.

Areolar Tissue

Least specialized loose connective tissue containing elastic fibers and viscous ground substance, forming an open framework that holds capillary beds under the skin.

White Fat

The most common type of adipose tissue; stores fat, absorbs shocks, and insulates against heat loss.

Brown Fat

Highly vascularized adipose tissue found in infants and young children containing cells with abundant mitochondria that break down lipids to generate heat.

Reticular Tissue

Loose connective tissue featuring reticular fibers that form a 3D supporting framework (stroma) for organs such as the liver, kidney, spleen, lymph nodes, and bone marrow.

Dense Regular Connective Tissue

Connective tissue made of tightly packed, parallel collagen fibers that resist tension in one plane; forms tendons, ligaments, and aponeuroses.

Dense Irregular Connective Tissue

Connective tissue with an interwoven network of collagen fibers providing strength to resist forces from many directions; forms organ capsules, dermis, periosteum, and perichondrium.

Elastic Tissue

Dense connective tissue composed mainly of elastic fibers that cushions shocks, permits expansion/contraction, and stabilizes positions of vertebrae and penis.

Superficial Fascia

The layer of areolar and adipose tissue (subcutaneous layer or hypodermis) that separates skin from underlying tissues.

Deep Fascia

Sheets of dense regular connective tissue bound to capsules, tendons, and ligaments that form a strong internal framework.

Subserous Fascia

Layer of areolar tissue lying between deep fascia and serous membranes.

Red Blood Cells (Erythrocytes)

Anucleate formed elements in blood that transport oxygen (and carbon dioxide), accounting for about half of whole blood volume.

White Blood Cells (Leukocytes)

Nucleated cells in blood that defend the body against infection and disease.

Platelets

Membrane-enclosed packets of cytoplasm involved in the blood clotting response to seal damaged blood vessels.

Chondrocytes

Cartilage cells residing in matrix chambers called lacunae.

Perichondrium

Structure surrounding cartilage, containing an outer fibrous layer for support/protection and an inner cellular layer for growth/maintenance.

Hyaline Cartilage

The most common cartilage type; tough and flexible with collagen fibers, providing stiff support and reducing friction between bony surfaces.

Elastic Cartilage

Supportive cartilage rich in elastic fibers that tolerates distortion without damage and returns to its original shape.

Fibrocartilage

Durable cartilage with a fibrous matrix that resists compression, limits movement, and prevents bone-to-bone contact.

Osteocytes

Bone cells located in lacunae within a calcified matrix, arranged around central canals and linked by canaliculi.

Mucous Membranes

Tissue membranes coated with secretions of mucous glands that line passageways opening to the exterior, underlaid by lamina propria (areolar tissue).

Serous Membranes

Membranes consisting of mesothelium supported by areolar tissue that line closed internal body cavities, producing serous fluid to reduce friction.

Cutaneous Membrane

The skin covering the body; a thick, waterproof, dry membrane composed of epithelium, areolar tissue, and dense irregular connective tissue.

Synovial Membranes

Membranes lacking a true epithelium that line joint cavities and secrete synovial fluid for lubrication during movement.

Skeletal Muscle Tissue

Striated voluntary muscle tissue composed of long, cylindrical, multinucleate cells (muscle fibers) that do not divide.

Cardiac Muscle Tissue

Striated involuntary muscle tissue found in the heart consisting of short, branched cells with single nuclei interconnected by intercalated discs.

Smooth Muscle Tissue

Nonstriated involuntary muscle tissue made of short, spindle-shaped cells with a single central nucleus, found in blood vessels and hollow organs.

Neurons

Cells specialized for conducting electrical impulses, consisting of a cell body, dendrites to receive signals, and an axon to conduct signals.

Neuroglia

Diverse supporting cells in nervous tissue that anchor, protect, nourish, and support neurons, retaining the ability to divide by mitosis.

Regeneration

A tissue repair process in which dead or damaged cells are replaced with new cells of the same type, fully restoring normal function.

Fibrosis

A tissue repair process where fibroblasts divide and replace damaged tissue with collagen fibers, producing scar tissue composed of dense irregular connective tissue.