Physiology Behrouz Mahmoudi Epithelial Tissue 1

 Tissue: group of cells that are similar in structure and function  Histology: study of tissues Types of Tissues: 1.Epithelium (covering) 2.Connective (support) 3.Muscle (movement) 4.Nervous (control) 2

Preparing tissues for microscopy Specimen is fixed (preserved) Cut into thin sections (slices) Stained with colored dyes 3

Epithelial Tissue “epithe” = laid on, covering Structure: 1.Covering and lining epithelium 2.Glandular epithelium Function: – Protection – Absorption – Filtration – Secretion 4

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 5

Special Properties 3.Supported by connective tissue – Rests on basement membrane 4.No blood supply (avascular) – Rely on diffusion and underlying connective tissue for food/O 2 5.Regeneration – Replace lost cells 6

Classification Two names = (# cell layers) + (shape of cells) Cell Layers: simple or stratified Shapes: squamous, cuboidal, or columnar 7

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Simple Epithelium  Absorption, secretion, filtration  Very thin 11

Simple Epithelium 12

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 13

Simple Epithelium  Simple cuboidal  Secretion & absorption  Lines ducts of glands (salivary), kidney tubules, ovary surface 14

Simple Epithelium Simple columnar – Absorption and secretion – Lines digestive tract – Microvilli, cilia – Mucous membranes: lubricating mucus 15

Simple Epithelium Pseudostratified columnar – Rests on basement membrane – false impression (pseudo) of being multi-layered – Secretes or absorbs – Respiratory tract – cilia propels mucus from lungs 16

Stratified Epithelium 2+ layers, more durable Main function = protect 17

Stratified Epithelium Stratified squamous – Withstand abuse, friction – Esophagus, mouth, outer portion of skin 18

Stratified Epithelium Stratified cuboidal – Usually 2 layers – Mainly in ducts of large glands (sweat, mammary, salivary) Sweat GlandEsophageal Gland 19

Stratified Epithelium Stratified columnar – Thick, waterproof layer – Pharynx, male urethra, lining ducts 20

Transitional Epithelium Able to change shape (cuboidal  squamous) Lining of hollow urinary organs (bladder, ureter, urethra) Stretches when filled with urine 21

Glandular Epithelium Gland: make and secrete a particular product 2 Types: – Endocrine gland: produce hormones secreted into tissue fluid or bloodstream – Exocrine gland: secrete products into ducts  onto body surfaces or body cavities Eg. mucous, sweat, oil, saliva, bile 22

Exocrine Glands Unicellular Mucus cells or goblet cells Multicellular Duct structure 23