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The Tissue Level of Organization Introduction Histology: the study of tissues – Tissue: composed of cells, and extracellular materials & fluids 4 Types of Tissues: – A) Epithelial: covers surfaces, lines passageways & chambers, produces gland secretions – B) Connective: fills internal spaces, supports & binds organs, stores energy – C) Muscle: contracts to produce movement – D) Neural: conducts electrical impulses & carries info throughout body Epithelial Tissue Includes epithelia & glands Functions: – – – – 1) Provides protection 2) Controls skin permeability 3) Provides sensation 4) Produces gland secretions Epithelial Cells (con’t) Shapes: – Squamous – Cuboidal – Columnar Arrangements: – Simple: single layer – Stratified: multiple layers – Pseudostratified: single layer, but appears to be multi-layered • All cells attach to basement membrane Epithelial Tissue - Simple Simple Squamous: lines ventral body cavities & blood vessels – decreases friction, provides absorption & secretion Simple Cuboidal: glands & ducts – protection, absorption, secretion Simple Columnar: lines stomach, intestines, gallbladder, uterine – protection, absorption, secretion Epithelial Tissue - Other Pseudostratified Ciliated Columnar: lines nasal cavities, trachea & bronchi – protection & secretion Transitional: urinary bladder, ureters – allows expansion & recoil for stretching Stratified Squamous: skin surface, lines mouth, throat, esophagus – protects against abrasion, pathogens & chemicals Connective Tissue Includes: bone, cartilage, blood, fat, etc. Composed of: – specialized cells surrounded by a matrix (protein fibers & ground substance fluid) Functions: – – – – 1) Support & Protection 2) Transport of Materials 3) Energy Storage 4) Body Defenses Types of Connective Tissue Connective Tissue Proper Types 1) Loose “areolar” – Separates skin from muscle, provides padding, & contains extensive blood supply 2) Adipose (loose with many fat cells) – Provides shock absorption, insulation, energy storage 3) Dense “fibrous/collagenous” – Tendons: connect muscle to bone – Ligaments: connect bone to bone Supporting Connective Tissue Cartilage: composed of chondrocyte cells & covered in perichondrium; NO blood supply – Hyaline cartilage: connects ribs to sternum & covers joints – Elastic Cartilage: forms outer ear & epiglottis – Fibrocartilage: pad between vertebrae & in pubic bone Bone: composed of osteocyte cells & covered in periosteum; EXTENSIVE blood supply “Membranes” May refer to plasma membrane, a barrier (i.e. basement membrane), OR A covering composed of epithelia tissue & connective tissue Types of Membranes 1) Mucous: line cavities that communicate with the exterior (i.e. respiratory, reproductive, & urinary tracts) – Kept moist by secretions & fluids 2) Serous: line sealed, internal divisions of body cavities (i.e. heart, lungs, etc.) – ↓ friction & allows for movement 3) Cutaneous: covers the body (skin) – Provides thick, waterproof protection 4) Synovial: fills cavities in bone joints – Lubricates and ↓ friction in joints Muscle Tissue Contraction involves the action of myosin & actin proteins 3 Types: – 1) Skeletal: composed of large, multinucleated cells • Most large muscles in the body • Appear striped, or STRIATED • Under VOLUNTARY control of nervous system Muscle Tissue (con’t) Types: – 2) Cardiac: striated, but composed of small, single-nucleus cells • Compose most of the heart • Controlled by pacemaker cells in heart (not nervous system) • Under INVOLUNTARY control – 3) Smooth: non-striated & composed of long, slender singlenucleus cells • Line blood vessels, urinary bladder, resp. & digest. tracts • Under INVOLUNTARY control of nervous system Neural Tissue Conducts electrical impulses throughout the body Mostly found in brain and spinal cord Composed of 2 types of cells: – 1) Neurons: send & receive impulses – 2) Neuroglia: provide support, nutrition, & defense for neurons Tissue Injury and Repair After injury happens, 2 processes occur: – 1) Inflammation: includes swelling, warmth, redness, & pain • Mast cells release chemicals to ↑ blood flow & stimulate nerve endings at injured area – 2) Regeneration: fibroblasts produce scar tissue • Skin, most connective tissues, & smooth muscles regenerate well • Striated muscles & nerve cells do not • Fibrosis: replacement of cardiac tissue with fibrous connective tissue