Chapter 4 : THE LIVING FABRIC . Tissue: group of cells that are similar in structure and function . Histology: study of tissues

Types of Tissues: 1. (covering) 2. Connective (support) 3. Muscle (movement) 4. Nervous (control)

Preparing tissues for microscopy

. Specimen is fixed (preserved) . Cut into thin sections (slices) . Stained with colored dyes Part I: Epithelial Tissue Epithelial Tissue

. “epithe” = laid on, covering . Structure: 1. Covering and lining epithelium 2. Glandular epithelium . Function:  Protection  Absorption  Filtration 

Special Properties 1. Polarity  Apical surface = exposed free surface or edge (some with microvilli, cilia)  Basal surface = lower, attached surface 2. Specialized contacts  Fits close together to form continuous sheets

Special Properties 3. Supported by connective tissue  Rests on basement membrane 4. No supply (avascular)  Rely on diffusion and underlying connective

tissue for food/O2 5. Regeneration – Replace lost cells

Classification . Two names = (# layers) + (shape of cells) . Cell Layers: simple or stratified . Shapes: squamous, cuboidal, or columnar

Simple Epithelium

. Absorption, secretion, filtration . Very thin

Simple Epithelium Simple Epithelium

. Simple squamous  Filtration, rapid diffusion  Capillary walls, air sacs in lungs, kidney filtration  Serous membranes: slick layer lining ventral body cavity and its organs

Simple Epithelium . Simple cuboidal  Secretion & absorption  Lines ducts of (salivary), kidney tubules, ovary surface

Simple Epithelium

. Simple columnar  Absorption and secretion  Lines digestive tract  Microvilli, cilia  Mucous membranes: lubricating

Simple Epithelium

. Pseudostratified columnar  Rests on basement membrane – false impression (pseudo) of being multi-layered  Secretes or absorbs  – cilia propels mucus from lungs

Stratified Epithelium

. 2+ layers, more durable . Main function = protect Stratified Epithelium

. Stratified squamous  Withstand abuse, friction  , mouth, outer portion of Stratified Epithelium

. Stratified cuboidal  Usually 2 layers  Mainly in ducts of large glands (sweat, mammary, salivary)

Sweat Stratified Epithelium

. Stratified columnar  Thick, waterproof layer  Pharynx, male urethra, lining ducts

Transitional Epithelium

. Able to change shape (cuboidal  squamous) . Lining of hollow urinary organs (bladder, ureter, urethra) . Stretches when filled with urine

Glandular Epithelium

. Gland: make and secrete a particular product . 2 Types:  : produce secreted into tissue fluid or bloodstream  : secrete products into ducts  onto body surfaces or body cavities  Eg. mucous, sweat, oil, saliva, Exocrine Glands

Unicellular Multicellular . Mucus cells or goblet . structure cells