Glossary: The Tissue Level of Organization

adipocytes: lipid storage cells

adipose tissue: specialized areolar tissue rich in stored fat

anchoring junction: mechanically attaches adjacent cells to each other or to the basement membrane

apical: that part of a cell or tissue which, in general, faces an open space

apocrine secretion: release of a substance along with the apical portion of the cell

apoptosis: programmed cell death

areolar tissue: (also, loose connective tissue) a type of connective tissue proper that shows little specialization with cells dispersed in the matrix

astrocyte: star-shaped cell in the central nervous system that regulates ions and uptake and/or breakdown of some neurotransmitters and contributes to the formation of the blood-brain barrier

atrophy: loss of mass and function

basal lamina: thin extracellular layer that lies underneath epithelial cells and separates them from other tissues

basement membrane: in epithelial tissue, a thin layer of fibrous material that anchors the epithelial tissue to the underlying connective tissue; made up of the basal lamina and reticular lamina

cardiac muscle: heart muscle, under involuntary control, composed of striated cells that attach to form fibers, each cell contains a single nucleus, contracts autonomously

cell junction: point of cell-to-cell contact that connects one cell to another in a tissue

chondrocytes: cells of the cartilage

clotting: also called coagulation; complex process by which blood components form a plug to stop bleeding

collagen fiber: flexible fibrous proteins that give connective tissue tensile strength

connective tissue membrane: connective tissue that encapsulates organs and lines movable joints

connective tissue proper: connective tissue containing a viscous matrix, fibers, and cells.

connective tissue: type of tissue that serves to hold in place, connect, and integrate the body’s organs and systems

cutaneous membrane: skin; epithelial tissue made up of a stratified squamous epithelial cells that cover the outside of the body

dense connective tissue: connective tissue proper that contains many fibers that provide both elasticity and protection

ectoderm: outermost embryonic germ layer from which the epidermis and the nervous tissue derive

elastic cartilage: type of cartilage, with elastin as the major protein, characterized by rigid support as well as elasticity

elastic fiber: fibrous protein within connective tissue that contains a high percentage of the protein elastin that allows the fibers to stretch and return to original size

endocrine gland: groups of cells that release chemical signals into the intercellular fluid to be picked up and transported to their target organs by blood

endoderm: innermost embryonic germ layer from which most of the digestive system and lower respiratory system derive

endothelium: tissue that lines vessels of the lymphatic and cardiovascular system, made up of a simple squamous epithelium

epithelial membrane: epithelium attached to a layer of connective tissue

epithelial tissue: type of tissue that serves primarily as a covering or lining of body parts, protecting the body; it also functions in absorption, transport, and secretion

exocrine gland: group of epithelial cells that secrete substances through ducts that open to the skin or to internal body surfaces that lead to the exterior of the body

fibroblast: most abundant cell type in connective tissue, secretes protein fibers and matrix into the extracellular space

fibrocartilage: tough form of cartilage, made of thick bundles of collagen fibers embedded in chondroitin sulfate ground substance

fibrocyte: less active form of fibroblast

fluid connective tissue: specialized cells that circulate in a watery fluid containing salts, nutrients, and dissolved proteins

gap junction: allows cytoplasmic communications to occur between cells

goblet cell: unicellular gland found in columnar epithelium that secretes mucous

ground substance: fluid or semi-fluid portion of the matrix

histamine: chemical compound released by mast cells in response to injury that causes vasodilation and endothelium permeability

histology: microscopic study of tissue architecture, organization, and function

holocrine secretion: release of a substance caused by the rupture of a gland cell, which becomes part of the secretion

hyaline cartilage: most common type of cartilage, smooth and made of short collagen fibers embedded in a chondroitin sulfate ground substance

inflammation: response of tissue to injury

lacunae: (singular = lacuna) small spaces in bone or cartilage tissue that cells occupy

lamina propria: areolar connective tissue underlying a mucous membrane

loose connective tissue: (also, areolar tissue) type of connective tissue proper that shows little specialization with cells dispersed in the matrix

matrix: extracellular material which is produced by the cells embedded in it, containing ground substance and fibers

merocrine secretion: release of a substance from a gland via exocytosis

mesenchymal cell: adult stem cell from which most connective tissue cells are derived

mesenchyme: embryonic tissue from which connective tissue cells derive

mesoderm: middle embryonic germ layer from which connective tissue, muscle tissue, and some epithelial tissue derive

mesothelium: simple squamous epithelial tissue which covers the major body cavities and is the epithelial portion of serous membranes

mucous connective tissue: specialized loose connective tissue present in the umbilical cord

mucous gland: group of cells that secrete mucous, a thick, slippery substance that keeps tissues moist and acts as a lubricant

mucous membrane: tissue membrane that is covered by protective mucous and lines tissue exposed to the outside environment

muscle tissue: type of tissue that is capable of contracting and generating tension in response to stimulation; produces movement.

myelin: layer of lipid inside some neuroglial cells that wraps around the axons of some neurons

myocyte: muscle cells

necrosis: accidental death of cells and tissues

nervous tissue: type of tissue that is capable of sending and receiving impulses through electrochemical signals.

neuroglia: supportive neural cells

neuron: excitable neural cell that transfer nerve impulses

oligodendrocyte: neuroglial cell that produces myelin in the brain

parenchyma: functional cells of a gland or organ, in contrast with the supportive or connective tissue of a gland or organ

primary union: edges of a wound are close enough together to promote healing without the use of stitches to hold them close

pseudostratified columnar epithelium: tissue that consists of a single layer of irregularly shaped and sized cells that give the appearance of multiple layers; found in ducts of certain glands and the upper respiratory tract

reticular fiber: fine fibrous protein, made of collagen subunits, which cross-link to form supporting “nets” within connective tissue

reticular lamina: matrix containing collagen and elastin secreted by connective tissue; a component of the basement membrane

reticular tissue: type of loose connective tissue that provides a supportive framework to soft organs, such as lymphatic tissue, spleen, and the liver

Schwann cell: neuroglial cell that produces myelin in the peripheral nervous system

secondary union: wound healing facilitated by wound contraction

serous gland: group of cells within the serous membrane that secrete a lubricating substance onto the surface

serous membrane: type of tissue membrane that lines body cavities and lubricates them with serous fluid

simple columnar epithelium: tissue that consists of a single layer of column-like cells; promotes secretion and absorption in tissues and organs

simple cuboidal epithelium: tissue that consists of a single layer of cube-shaped cells; promotes secretion and absorption in ducts and tubules

simple squamous epithelium: tissue that consists of a single layer of flat scale-like cells; promotes diffusion and filtration across surface

skeletal muscle: usually attached to bone, under voluntary control, each cell is a fiber that is multinucleated and striated

smooth muscle: under involuntary control, moves internal organs, cells contain a single nucleus, are spindle-shaped, and do not appear striated; each cell is a fiber

stratified columnar epithelium: tissue that consists of two or more layers of column-like cells, contains glands and is found in some ducts

stratified cuboidal epithelium: tissue that consists of two or more layers of cube-shaped cells, found in some ducts

stratified squamous epithelium: tissue that consists of multiple layers of cells with the most apical being flat scale-like cells; protects surfaces from abrasion

striation: alignment of parallel actin and myosin filaments which form a banded pattern

supportive connective tissue: type of connective tissue that provides strength to the body and protects soft tissue

synovial membrane: connective tissue membrane that lines the cavities of freely movable joints, producing synovial fluid for lubrication

tight junction: forms an impermeable barrier between cells

tissue membrane: thin layer or sheet of cells that covers the outside of the body, organs, and internal cavities

tissue: group of cells that are similar in form and perform related functions

totipotent: embryonic cells that have the ability to differentiate into any type of cell and organ in the body

transitional epithelium: form of stratified epithelium found in the urinary tract, characterized by an apical layer of cells that change shape in response to the presence of urine

vasodilation: widening of blood vessels

wound contraction: process whereby the borders of a wound are physically drawn together