Body Tissues

Tissues - groups of cells that are similar in structure and function

Four tissue types and general function:

*EPITHELIUM - covering

*CONNECTIVE - support

MUSCLE - movement

NERVOUS - control

epithelial tissue (epithelium)

the lining, covering, and glandular tissue of the body

protection (skin, respiratory tract), absorption (stomach, small intestine), filtration (kidneys), and secretion (glands-sweat, oil, digestive enzymes, mucus)

special characteristics of epitheliumform continuous sheets, joined by desmosomes and tight junctions

apical surface= free surface or edge exposed to body’s exterior or cavity of internal organ

basement membrane =lower surface of epithelium, secreted by cells

no blood supply, depend on diffusion from capillaries for food and oxygen

regenerate themselves easily

classification of epithelium

by cell arrangement (simple, stratified) and cell shape (squamous, cuboidal, columnar)

simple = one cell layer

stratified = more than one cell layer

squamous = flattened like fish scales

cuboidal = cube-shaped like dice

columnar = shaped like columns

simple epitheliasimple squamous - single layer, filtration, rapid diffusion (alveoli, capillaries, serous membranes)

simple cuboidal - single layer on basement membrane (glands and ducts, kidney tubules and surface of ovaries)

simple columnar - single layer, tall close together (lines digestive tract from stomach to anus)

pseudostratified (ciliated) columnar - appear at different heights above basement membrane, absorption, secretion (lines respiratory tract)

stratified epitheliastratified squamous - several layers, receives frequent friction (esophagus, mouth, outer skin)

stratified cuboidal/columnar - two cell layers, cuboidal at surface, fairly rare (ducts of large glands) *not in table

transitional - modified stratified squamous, change shape, subject to stretching (urinary bladder, ureters)

types of epithelium (picture pg 80)

glandular epitheliumgland=one or more cells that secrete a product

duct = channel leading from a gland to epithelial surface

endocrine gland - ductless, secrete hormones directly into blood vessels (thyroid, adrenals, pituitary)

exocrine glands - have ducts, excrete product to internal or external surface (sweat, oil, liver, pancreas)

glands (picture)

connective tissuemost abundant and widely distributed tissue

most are well vascularized (good blood supply)

tendons and ligaments have a poor blood supply

cartilages are avascular

made up of many cell types plus nonliving substances called the extracellular matrix

extracellular matrixMade of two elements in varying amounts:

ground substance - water, adhesion proteins, large polysaccaride molecules

fibers - collagen, elastic, reticular

types of connective tissuebone (osseous tissue) - rocklike hardness, calcium salt matrix, protection, support (skull, bones)

hyaline cartilage - collagen fibers, rubbery matrix (larynx, attaches ribs to sternum, ends of bones, fetus skeleton)

fibrocartilage - chondrocytes and collagen fibers, highly compressible (between vertebrae)

elastic cartilage - elasticity (supports external ear)

connective tissuesdense connective (dense fibrous) -collagen fibers, fibroblasts, ropelike (tendons-muscle to bone, ligaments-bone to bone, lower layer of skin/dermis)

areolar - soft, pliable, “cobweb”, cushions and protects, soaks up fluid during inflammation, swelling/puffiness known as edema (widely distributed, holds organs together, underlies mucous membranes lamina propria)

adipose (fat) - areolar tissues in which fat cells predominate (subcutaneous tissue, protects kidneys, eyeballs, hips, breasts)

reticular - interwoven reticular fibers, support free blood cells (lymph nodes, spleen, bone marrow)

blood - blood cells and plasma, transports nutrients, gases, and wastes (in blood vessels)

connective tissues (pictures pg 83-84)

muscle tissue

Three types:

skeletal - striated (stripes), multinucleated, voluntary movements (attached to skeletal bones)

smooth - no striations, uninucleate, spindle-shaped, involuntary (walls of stomach, bladder, uterus, and blood vessels)

cardiac - striated, uninucleate, branching cells, intercalated disks (gap junctions that conduct electrical impulse, involuntary (heart)

muscle tissue (picture pg 157)

nervous tissue

neurons and supporting cells - cytoplasm drawn out into long extensions, electrochemical impulses (brain, spinal cord, nerves)

nervous tissue (picture pg 199)

tissue repair (wound healing)

Two major ways:

regeneration = replacement of destroyed tissue by same kind of cell

fibrosis = repair by dense (fibrous) connective tissue, the formation of scar tissue; strong but lacks flexibility

Which type used depends on type of tissue and severity. Clean cuts generally heal much more successfully than ragged tears of tissue.

Epithelia and connective tissues regenerate well. Mature cardiac muscle and nervous tissue are amitotic and are repaired by fibrosis.

At the clinic

Three patients in an intensive care unit are examined by the resident doctor. One patient has brain damage from a stroke, another had a heart attack that severely damaged his heart muscle, and the third has a severely damaged liver (a gland) from a crushing injury in a car accident.

All three patients have stabilized and will survive, but only one will have full functional recovery through regeneration. Which one and why?