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Tissues. What is a tissue? Groups of cells working together to perform a function Four Basic Types of Tissues Epithelial Covers surfaces, lines cavities, forms glands Connective Protect/support, stores energy, provides immunity Muscle Causes movement Nervous
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What is a tissue?Groups of cells working together to perform a function • Four Basic Types of Tissues • Epithelial • Covers surfaces, lines cavities, forms glands • Connective • Protect/support, stores energy, provides immunity • Muscle • Causes movement • Nervous • Detects changes, sends/receives impulses Tissue Basics
Arranged in closely packed sheets • Singular or multiple layers • Layered • Apical surface (most superficial) • Exposed to outer most layer of body cavities • Lines organs or exterior of body • Lateral surface (cells facing cells) • Basal Layer (deepest layer of cells) • Basement membrane fibers that bind and support • Avascular: Lacking blood vessels • Materials are exchanged by diffusion from connective tissue • Contain a nerve supply • High capacity for renewal Epithelial Tissue Characteristics
Called: Epithelium = singular, Epithelia = plural • Two Types: • Covering and Lining • Outer covering of the skin and internal organs • Lines body cavities and interiors of some systems, blood vessels • Glandular • Makes up the secreting portions of glands • Ex: Sweat glands Epithelial Tissue
Basic Epithelia Shapes • Categorized as either: • Simple cells organized in a SINGLE layer • Found where diffusion, osmosis, filtration, secretion, and absorption occur • Stratified cells organized in 2 or more layers • Found where protection is needed and there is often wear and tear
Simple Epithelium • Squamous= flat cells • Important for filtration (kidneys) or diffusion (lungs & capillaries) • Cuboidal= cube shaped cells • Important for secretion and absorption • Columnar= column shaped cells • Important in absorption and secretion of mucus
Pseudostratified Columnar appears stratified: nuclei at various levels
Pseudostratified Columnar appears stratified: nuclei at various levels
Stratified Epithelium • Squamous= flat cells • Apical layer cells are flat • Deep layers vary from cuboidal to columnar • Cells in the basal layer divide and move upward toward apical surface • Found in areas of surface wear & tear to provide protection • Mouth • Esophagus • Vagina • Tongue
Stratified Epithelium • Cuboidal= cube shaped cells • Apical and basal layers are cuboidal • Found in areas where protection, secretion, and absorption take place • Ducts of sweat glands • Esophageal glands • Male urethra
Stratified Epithelium • Columnar= column shaped cells • Apical layer cells are columnar • Found in areas where protection and secretion take place • Lines urethra • Esophageal glands • Anal mucous membrane • Conjunctiva of the eye