Chapter 5: The Human Tissues

Vocabulary practice flashcards covering human tissue types, classification, histology methods, cellular junctions, glands, membranes, and tissue dynamics based on Chapter 5.

Histology

The study of tissues and how they are arranged into organs, also known as microscopic anatomy.

Tissue

A group of similar cells and cell products working together to perform a specific role in an organ.

Matrix

Extracellular material surrounding tissue cells, composed of fibrous proteins and a clear gel called ground substance.

Ground Substance

Clear gel component of extracellular matrix containing water, gases, minerals, nutrients, wastes, and hormones; also called tissue fluid, extracellular fluid (ECF), or interstitial fluid.

Ectoderm

The outer primary germ layer that gives rise to the epidermis and nervous system.

Endoderm

The inner primary germ layer that gives rise to the mucous membrane lining of the digestive and respiratory tracts, as well as digestive glands.

Mesoderm

The middle primary germ layer that becomes gelatinous mesenchyme, giving rise to cartilage, bone, and blood.

Mesenchyme

Gelatinous embryonic tissue derived from mesoderm, composed of wispy collagen fibers and fibroblasts in a gel matrix.

Longitudinal Section

A tissue specimen cut along its long axis.

Cross Section

A tissue specimen cut perpendicular to the long axis of an organ; also known as a transverse section.

Oblique Section

A tissue specimen cut at an angle between cross and longitudinal sections.

Epithelial Tissue

A sheet of closely adhering cells, one or more cells thick, with an upper surface exposed to the environment or an internal body space; it is avascular and covers body surfaces and lines cavities.

Basement Membrane

A layer between an epithelium and underlying connective tissue containing collagen, glycoproteins, and protein-carbohydrate complexes that anchors the epithelium.

Basal Surface

The surface of an epithelial cell that faces toward the basement membrane.

Apical Surface

The surface of an epithelial cell that faces away from the basement membrane toward an internal space or the external environment.

Goblet Cells

Wineglass-shaped, mucus-secreting cells found within simple columnar and pseudostratified columnar epithelia.

Simple Squamous Epithelium

A single row of thin, scaly cells that permits rapid diffusion or transport of substances and secretes serous fluid.

Simple Cuboidal Epithelium

A single layer of square or round cells functioning in absorption, secretion, and mucus production and movement.

Simple Columnar Epithelium

A single row of tall, narrow cells with oval nuclei in the basal half, often featuring microvilli or cilia, functioning in absorption and secretion.

Pseudostratified Columnar Epithelium

Epithelium where all cells touch the basement membrane but not all reach the surface, featuring cilia and goblet cells to secrete and propel mucus.

Keratinized Stratified Squamous Epithelium

Multilayered epithelium with surface layers of dead, flat scaly cells that resists abrasion, retards water loss through skin, and resists penetration by pathogens.

Nonkeratinized Stratified Squamous Epithelium

Multilayered epithelium lacking a surface layer of dead cells, providing abrasion resistance in moist internal spaces like the oral mucosa, esophagus, and vagina.

Stratified Cuboidal Epithelium

Epithelium consisting of two or more layers of cells with square or round surface cells, functioning in sweat secretion and production of sperm and ovarian hormones.

Urothelium

Multilayered epithelium unique to the urinary tract with surface cells that change from round to flat when stretched to allow filling of the ureter and bladder.

Fibroblasts

Connective tissue cells that produce the fibers and ground substance of the matrix.

Macrophages

Large phagocytic connective tissue cells arising from monocytes that devour foreign material and activate the immune system.

Plasma Cells

Connective tissue cells derived from lymphocytes that synthesize antibodies.

Mast Cells

Cells found along blood vessels that secrete heparin to inhibit clotting and histamine to dilate blood vessels.

Collagenous Fibers

Tough, flexible, and stretch-resistant matrix fibers made of collagen; called white fibers due to their appearance in fresh tissue.

Reticular Fibers

Thin collagen fibers coated with glycoprotein that form a sponge-like framework (stroma) for organs like the spleen and lymph nodes.

Elastic Fibers

Matrix fibers made of the protein elastin that allow tissue to stretch and recoil like a rubber band.

Glycosaminoglycans (GAGs)

Long polysaccharides composed of amino sugars and uronic acid in ground substance that regulate water and electrolyte balance in tissues.

Areolar Tissue

Loose connective tissue featuring loosely organized fibers, abundant blood vessels, and all six connective tissue cell types and fiber types.

Reticular Tissue

Loose connective tissue consisting of a mesh of reticular fibers and fibroblasts that forms a supportive stroma for lymphatic organs.

Dense Regular Connective Tissue

Connective tissue featuring densely packed, parallel collagen fibers and compressed fibroblast nuclei, forming tendons and ligaments.

Dense Irregular Connective Tissue

Connective tissue composed of densely packed, randomly arranged collagen fibers with few visible cells, designed to withstand unpredictable stresses in multiple directions.

White Adipose Tissue

The predominant adult fat tissue, providing thermal insulation, organ cushioning, and energy storage, composed of large empty-looking adipocytes with compressed nuclei.

Brown Adipose Tissue

Heat-generating fat tissue found mainly in fetuses, infants, and children, colored by blood vessels and abundant mitochondria.

Chondroblasts

Cartilage-producing stem cells that secrete matrix and become trapped in lacunae.

Chondrocytes

Mature cartilage cells that reside within matrix cavities called lacunae.

Perichondrium

A sheath of dense irregular connective tissue surrounding elastic and most hyaline cartilage, providing a reserve population of chondroblasts.

Hyaline Cartilage

Cartilage with a clear, glassy matrix due to fine collagen fibers; eases joint movement, keeps airways open, and forms the juvenile skeleton.

Elastic Cartilage

Cartilage containing an abundance of elastic fibers covered by perichondrium, providing flexible support in the external ear and epiglottis.

Fibrocartilage

Cartilage containing large, coarse bundles of collagen fibers that resists compression and absorbs shock in the pubic symphysis, menisci, and intervertebral discs.

Osteon

The structural cylinder of compact bone consisting of a central (osteonic) canal surrounded by concentric ringlike layers of bone matrix (lamellae).

Canaliculi

Tiny canals radiating from lacunae in bone matrix that allow osteocytes to connect and communicate with neighboring cells.

Erythrocytes

Red blood cells that appear as pale pink discs with light centers and function in transporting oxygen and carbon dioxide.

Neurons

Nerve cells specialized to detect stimuli, respond, and rapidly transmit electrical and chemical signals throughout the body.

Neuroglia

Glial cells that protect and assist neurons in the nervous system.

Skeletal Muscle

Voluntary, striated muscle tissue composed of long, cylindrical multinucleated cells (muscle fibers) attached to bones.

Cardiac Muscle

Involuntary, striated muscle tissue limited to the heart wall, consisting of short, branched cardiomyocytes with centrally located single nuclei joined end-to-end by intercalated discs.

Smooth Muscle

Involuntary, nonstriated muscle tissue composed of short, fusiform cells with a single central nucleus, forming walls of hollow visceral organs.

Tight Junction

A zipperlike linkage formed by transmembrane cell-adhesion proteins that encircles epithelial cells near their apical surface to seal off the intercellular space.

Desmosome

A patchlike cell junction featuring hook-like J-shaped proteins that holds adjacent cells together against mechanical stress.

Hemidesmosome

A half-desmosome junction that anchors the basal cells of an epithelium to the underlying basement membrane.

Gap Junction

A communicating cell junction formed by ringlike connexons that allows ions, nutrients, and small solutes to pass directly between adjacent cells.

Exocrine Glands

Glands that maintain contact with an epithelial surface via a duct to discharge secretions.

Endocrine Glands

Ductless glands that secrete chemical messengers (hormones) directly into the blood capillary network.

Parenchyma

The functional cells of a gland or organ that perform synthesis and secretion.

Stroma

The connective tissue framework of a gland or organ that supports and organizes the functional tissue.

Eccrine Secretion

Mode of exocrine secretion where product is released by exocytosis without cytoplasmic loss; also called merocrine secretion.

Apocrine Secretion

Mode of secretion where a lipid droplet wrapped in plasma membrane and cytoplasm buds off from the cell surface.

Holocrine Secretion

Mode of exocrine secretion where secretory cells accumulate a product and whole cells disintegrate to release the secretion.

Mucous Membrane

Membrane lining passages open to the external environment, composed of an epithelial layer, lamina propria (areolar tissue), and muscularis mucosae (smooth muscle); also called mucosa.

Serous Membrane

Membrane lining closed internal body cavities, consisting of simple squamous mesothelium resting on areolar tissue that secretes watery serous fluid.

Hyperplasia

Tissue growth accomplished through an increase in cell number via cell multiplication.

Hypertrophy

Tissue growth accomplished through enlargement of preexisting cells.

Neoplasia

Development of a tumor (neoplasm) composed of abnormal, nonfunctional tissue.

Metaplasia

The transformation of one mature, fully differentiated tissue type into another mature tissue type.

Totipotent Stem Cells

Stem cells from very early embryos that possess unlimited developmental plasticity, able to give rise to any cell type and accessory organ of pregnancy.

Pluripotent Stem Cells

Stem cells from the inner cell mass (embryoblast) of an embryo that can develop into any embryonic cell type, but not accessory organs like the placenta.

Regeneration

Replacement of dead or damaged cells by the exact same type of cell, fully restoring normal function.

Fibrosis

Replacement of damaged tissue with scar tissue, holding organs together without restoring normal tissue function.

Atrophy

Shrinkage of tissue through a loss in cell size or cell number due to factors like aging or disuse.

Infarction

Sudden pathological death of tissue that occurs when blood supply is completely cut off.

Apoptosis

Programmed cell death where cells fulfill their function and undergo controlled self-destruction.