Chapter 3

Tissues and early embryology

epithelia

sheets of cells that cover every exposed body surface and line any internal cavities and passageways

basement membrane

a complex structure produced by the epithelium and cells of the underlying connective tissue

basal lamina

superficial portion of the basement membrane

reticular lamina

contains bundles of coarse protein fibers that anchor the basement membrane to the underlying connective tissue

simple epithelium

found only in protected areas inside the body; thoracic, abdominal, pelvic cavities, chambers of the heart, and all blood vessels

stratified epithelium

found in surfaces of the skin and the lining of the oral cavity

squamous epithelium

thin, flat and irregular in shape

mesothelium

simple squamous epithelium that lines body cavities

endothelium

simple squamous epithelium that lines the heart and blood vessels

stratified squamous epithelium

cells form a series of layers; protects the surface of the skin, throat, esophagus, rectum, vagina, and anus

keratin

apical layers of epithelial cells that are packed with filaments of protein

cuboidal epithelium

hexagonal boxes and appear square; each nucleus is centrally located

simple cuboidal epithelia

found where secretion and absorption take place; lining of kidney tubules

stratified cuboidal epithelia

found in the ducts of sweat and mamary glands

columnar epithelium

hexagonal, with a much greater width; nuclei are located within the basal portion of the cell

simple columnar epithelium

found in the lining of the stomach, intestinal tract, uterine tubes, and many excretory ducts

stratified columnar epithelia

has more than two layers; found in the pharynx, urethra, and anus

pseudostratified columnar epithelium

lines most of the nasal cavity, trachea, bronchi, and also portions of the male reproductive tract

transitional epithelium

lines the renal pelvis, ureters, and urinary bladder

exorcrine glands

release their secretions onto an epithelial surface through epithelial ducts

serous glands

secrete a watery solution that usually contains enzymes; saliva

mucous glands

secretes mucins that absorb water to form a slippery mucus

mucins

glycoproteins

endocrine glands

ductless glands that release their secretions by exocytosis directly into the interstitial fluid surrounding the cell

connective tissue

tissues that are not exposde to the environment outside the body

fibroblasts

produce connective tissue fibers

fibrocytes

maintain connective tissue fibers and matrix

fixed macrophages

phagocytize pathogens and damaged cells

adipocytes

store lipid reserves

mesenchymal cells

connective tissue stem cells that can differentiate into other cell types

melanocytes

synthesize melanin

free macrophages

mobile/traveling phagocytic cells that can differentiate into other cell types

mast cells

stimulate local inflammation

lymphocytes

participate in immune response

neutrophils and eosinophils

mobilize during infection or tissue injury

collagen fibers

strongest and most common fibers

tendons

connects skeletal muscles to bones

ligaments

connects bone to bone

reticular fibers

thin and form a branching, interwoven framework that is tough but flexible; found in th espleen and liver

elastic fibers

branching and wavy; can recoil

loose connective tissue

fill spaces between organs, provide cushioning and support epithelia

areolar tissue

least specialized connective tissue; delivers oxygen and nutrients and remocing carbon dioxide and wastes

adipose tissue

immobile and clustered together like tightly packed grapes

reticular tissue

consists of reticular fibers, macrophages, fibroblasts, and fibrocytes; supports connective tissue of the liver, spleen, lymph nodes, and bone marrow

dense connective tissues

consists of a mass amount of fibers

dense regular connective tissue

collagen fibers that are tightly packed and aligned parallel to applied forces; tendons, aponeuroses, elastic tissue, and ligaments

dense irregular connective tissue

tissue strengthens and supports areas subjected to stress from many directions