The Tissue Level of Organization

Introduction Histology: the study of tissues –T–Tissue: composed of cells, and extracellular materials & fluids 4 Types of Tissues: –A–A) Epithelial: covers surfaces, lines passageways & chambers, produces gland secretions –B–B) Connective: fills internal spaces, supports & binds organs, stores energy –C–C) Muscle: contracts to produce movement –D–D) Neural: conducts electrical impulses & carries info throughout body

Epithelial Tissue Includes epithelia & glands Functions: –1–1) Provides protection –2–2) Controls skin permeability –3–3) Provides sensation –4–4) Produces gland secretions

Epithelial Cells (con’t) Shapes: –S–Squamous –C–Cuboidal –C–Columnar Arrangements: –S–Simple: single layer –S–Stratified: multiple layers –P–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 –d–decreases friction, provides absorption & secretion Simple Cuboidal: glands & ducts –p–protection, absorption, secretion Simple Columnar: lines stomach, intestines, gallbladder, uterine –p–protection, absorption, secretion

Epithelial Tissue - Other Pseudostratified Ciliated Columnar: lines nasal cavities, trachea & bronchi –p–protection & secretion Transitional: urinary bladder, ureters –a–allows expansion & recoil for stretching Stratified Squamous: skin surface, lines mouth, throat, esophagus –p–protects against abrasion, pathogens & chemicals

Connective Tissue Includes: bone, cartilage, blood, fat, etc. Composed of: –s–specialized cells surrounded by a matrix (protein fibers & ground substance fluid) Functions: –1–1) Support & Protection –2–2) Transport of Materials –3–3) Energy Storage –4–4) Body Defenses

Types of Connective Tissue

Connective Tissue Proper Types 1) Loose “areolar” –S–Separates skin from muscle, provides padding, & contains extensive blood supply 2) Adipose (loose with many fat cells) –P–Provides shock absorption, insulation, energy storage 3) Dense “fibrous/collagenous” –T–Tendons: connect muscle to bone –L–Ligaments: connect bone to bone

Supporting Connective Tissue Cartilage: composed of chondrocyte cells & covered in perichondrium; NO blood supply –H–Hyaline cartilage: connects ribs to sternum & covers joints –E–Elastic Cartilage: forms outer ear & epiglottis –F–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) –K–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) –P–Provides thick, waterproof protection 4) Synovial: fills cavities in bone joints –L–Lubricates and ↓ friction in joints

Muscle Tissue Contraction involves the action of myosin & actin proteins 3 Types: –1–1) 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: –2–2) 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 –3–3) Smooth: non-striated & composed of long, slender single- nucleus 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: –1–1) Neurons: send & receive impulses –2–2) Neuroglia: provide support, nutrition, & defense for neurons

Tissue Injury and Repair After injury happens, 2 processes occur: –1–1) Inflammation: includes swelling, warmth, redness, & pain Mast cells release chemicals to ↑ blood flow & stimulate nerve endings at injured area –2–2) 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