TISSUE The Living Fabric

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Epithelial Tissue  Epithelial tissue (epithelium)  Sheet of cells that covers a body surface or lines a body cavity.  Two types: Covering and lining epithelium Outer layer of skin, lines open cavities Glandular epithelium Fashions the glands of the body

Epithelial Tissue  Epithelium has many functions:  Protections  Absorption  Filtration  Excretion  Secretion  Sensory reception

Classification of Epithelia  Each epithelium is given two names  First - # of layers Simple and stratified Simple epithelia – single cell layer (found where absorbtion and filtration occur Stratified epithelia – two or more layers (high abrasion areas)

Classification of Epithelia  Second name – shape of cells  Three common shapes Squamous cells – flattened and scalelike Cuboidal cells – boxlike Columnar cells - tall and column shaped

Simple Epithelia  Simple Squamous  Flattened laterally, cytoplasm is sparse  Look like a fried egg Allows passage of materials by diffusion and filtration Areas where protection is not important Kidneys, air sacs of lungs, lining of heart  Two names that reflect their location Endothelium – ‘inner covering’ Mesothelium – covering organs

Simple Cuboidal Epithelium  Consists of a single layer of cells as tall as they are wide, spherical central nuclei  Functions: Secretion Absorption  Location Ovary surface, ducts and secretory protions of small glands

Simple Columnar Epithelium  Single layer of tall closely packed cells, round/oval nuclei  Some contain cilia which help move substances through pathway  Function: Absorption, secretion of mucus  Location: Lines most of the digestive tract, gallbladder

Stratified Epithelia  Two or more layers of cells  More durable  Regenerate from below  Role is protection

Stratified Epithelia  Stratified Squamous Epithelium  Thick membrane composed of several layers  Function: Protects underlying tissues in areas subjected to abrasion  Locations: Moist linings of mouth and esophagus

Stratified Epithelia  Stratified Cuboidal and Columnar Epithelia  Cuboildal Quite rare in the body Mostly found in ducts of larger glands  Columnar Small amounts are found in pharynx, and lining of some glandular ducts

Connective Tissue

 Found everywhere in the body  Most abundent and widely distributed of the primary tissues  Four main classes  Connective tissue proper  Catilage  Bone tissue  blood

Connective Tissue  Functions:  Binding and support  Protection  Insulation  Transportation of substances within the body

Common Characteristics  Despite their diverse functions, they have many common characteristics  Common origin All connective tissue comes from mesenchyme (embryotic tissue)  Degrees of vascularity Have many degrees of vascularity (contain vessels)  Extracellular Matrix Seperates the living cells of the tissue Because of matrix connective tissue can bear weight

Structural Elements of Connective Tissue  Connective Tissues have 3 main elements:  Ground substance  Fibers  Cells

Ground Substance  Unstructured material that fills the space between the cells and contains the fibers  Composed of: Interstitial fluid Cell adhesion proteins Acts like glue, helps attach themselves to matrix elements Proteoglycans  Holds large amounts of fluid and functions as a molecular sieve, or medium for nutrients to diffuse between blood capliaries and cells

Fibers  Provide support  Three main types of fibers: Collagen Elastic Reticular fibers

Fibers  Collagen fibers  By far the strongest and most abundant  Constructed mainly of collagen Secreted into the extracellular space Cross-linked fibrils Because of this cross-linked pattern they are very strong  Have a glistening white appearance – also called white fibers

Elastic Fibers  Long, thin fibers that form branching networks in the extracellular matrix  Contain rubber-like protein elastin Allows them to stretch and recoil  Found where elasticity is needed Skin, lungs, and blood vessel walls  Sometimes called yellow fibers

Reticular Fibers  Short, fine, collagenous fibers  Branch extensively, forming delicate networks that surround small blood vessels and support soft tissue

Cells  Each connective tissue has a fundamental cell type  Blast – ‘bud’ or ‘sprout’, means ‘forming’  Primary blast cell types by connective tissue class are: Connective tissue proper (fibroblast) Cartilage (Chondroblast) Bone (osteoblast) Blood (hematopoietic stem cell) Is no located in its tissue (blood)  These cells make the matrix of their connective tissue.

Connective Tissue Proper  Has two subclasses:  Loose connective tissues  Dense connective tissues  Except for bone and blood, all mature connective tissues belong to this class

Loose Connective Tissue  Areolar Connective Tissue  Gel-like matrix with three fiber types Fibroblasts, macrophages, mast cells, and some white blood cells  Function Wraps and cushions organs Plays important role in inflammation (holds fluids)  Location Widely distributed under epithelia of body Surrounds capillaries

Loose Connective Tissue  Adipose (fat) tissue  Closely packed fat cells  Have nucleus pushed to side by large fat droplet  Function:  Provides reserve food fuel  Insulates against heat loss  Supports and protects glands  Location:  Under skin  Around kidneys and eyeballs  Within abdomen and breasts

Loose Connective Tissue  Reticular Connective Tissue  Network of reticular fibers in a typical loose ground substance; lie on the network  Function:  Fibers from soft internal skeleton that supports other cell types of cells including white blood cells  Location:  Lymphoid organs

Pictures Adipose Tissue Areolar Tissue Reticular Tissue