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Animal Tissues Introduction Animal bodies are organized into hierarchical levels with each level built from the level below it – cells – the smallest units of the body that are alive and all living things are composed of cells – tissues – group of like cells working together to perform the same function – organ – a group of several different types of tissues working together to perform a specific function – system – a group of organs working together to perform a very complex, integrated process – organisms – all the systems working together to sustain life 1. While cells are basic functional and structural unit of life, they function in groups as tissues to carry out specialized activities 2. Properties of tissues are influenced by factors such as extracellular material and connections between cells 3. Tissues may be hard, semisolid, or liquid 4. Vary with kind of cells present, cellular arrangement, and types of fibers present AnimalTissues Classified into four groups according to – function – structure Groups 1. epithelial 2. connective 3. muscle 4. nervous Body Tissues Classification 1. Epithelial Tissue • covers body surfaces, lines hollow organs, cavities, and ducts, and forms glands 2. Connective Tissue • • • • protects and supports body and organs binds organs together stores energy reserves as fat helps provide immunity Body Tissues Classification 3. Muscular Tissue • generates physical force 4. Nervous Tissue • • monitors and responds to changes in a variety of conditions inside and outside the body helps maintain homeostasis Epithelial Tissues General Features Epithelium (singular) or epithelia (plural) • lines body surfaces • cells closely packed – tightly held together with numerous junctions • cells arranged in sheets – single layers = simple – multiple layers = stratified • surfaces – apical = free surface or superficial layer – basal = attached to basement membrane or deepest layer Figure 4.1 Epithelial Tissue basement membrane • thin extracellular layer made up of – basal lamina • • • closest to epithelial cells secreted by epithelial cells components – collagen, laminin, and glycoproteins – reticular lamina • • • deep to basal lamina part of connective tissue layer produced by fibroblasts Epithelial Tissue Basement membrane functions • • • attach and support epithelium migration surface for growth and repair filter large molecules and cells Epithelium characteristics • • avascular high rate of cell division – because apical surface cells sloughed off, worn off, and damaged then replaced – two types 1. covering and lining 2. glandular Figure 4.2 Covering and Lining Epithelia Classified according to 1. arrangement of cells in layers • • • simple = single stratified = multiple pseudostratified = single but appears multiple 2. cell shapes • • • • squamous = flat apical surface cuboidal = shaped like cubes or hexagons columnar = taller than wide, apical surface may have cilia or microvilli transitional = change shape from cuboidal to flat and back allowing stretch and recoil Table 4.1 pt 1 Table 4.1 pt 2 Table 4.1 pt 3 Table 4.1 pt 4 Table 4.1 pt 5 Table 4.1 pt 6 Table 4.1 pt 7 Glandular Epithelia Glandular cell function is secretion • often lie in clusters deep to covering and lining epithelium • consist of single or multiple cells Classification of glands • exocrine – into ducts – onto a surface • endocrine – into the blood Table 4.1 pt 8 Table 4.1 pt 9 Connective Tissues Connective Tissue • • Most abundant tissue type Functions 1. binds together, supports, strengthens other tissue types 2. protects and insulates internal organs 3. compartmentalizes structures 4. major transport system 5. major site of stored energy reserves 6. main site of immune responses General Features Two basic elements 1. cells 2. extracellular matrix Characteristics 1. do not occur on surfaces 2. usually highly vascular • exceptions include cartilage and tendons 3. have nerve supply Types of Cells • Major types of connective tissues have immature “blast” cells – fibroblasts in loose and dense connective – chondrobasts in cartilage – osteoblasts in bone • Blast cell characteristics – mitotic – secret matrix – differentiate into “-cyte” cells Types of Cells 1. 2. 3. 4. 5. fibroblasts macrophages mast cells adipocytes white blood cells (WBC) Figure 4.3 Extracellular Matrix • • determines classification of connective tissues two components – ground substance – fibers Ground Substance • • • between cells and fibers can be fluid, semifluid, or calcified functions – – – – – supports cells binds cells together stores water provides medium for substance exchange active in tissue development, migration, proliferation, shape and metabolic functions Ground Substance • • contains large organic molecules complex combinations of polysaccharides and proteins – glycosaminoglycans or GAGs • • trap water example: hyaluronic acid Fibers • • Function to strengthen and support Three major types 1. collagen 2. elastic 3. reticular Collagen Fibers • • • • • • very strong resist pulling forces not stiff often occur in parallel bundles most abundant protein in body 25% of total proteins found in most connective tissue types – – – – bone cartilage tendons ligaments Figure 4.3 Elastic Fibers • • • • • • smaller in diameter than collagen branch and join together forming network protein named elastin can stretch up to 150% of relaxed length without breaking ability to return to original shape plentiful in – skin – blood vessel walls – lung tissue Reticular Fibers • • • • • collagen arranged in fine bundles coated with glycoprotein provide support in walls of blood vessels help form the basement membrane form network around cells of some tissues – – – – areolar adipose smooth muscle plentiful in reticular connective tissue Connective Tissue Types Two basic groups • embryonic connective tissue • mature connective tissue 1. 2. 3. 4. 5. loose dense cartilage bone liquid Mature Connective Tissue 1. loose • • • areolar connective tissue adipose tissue reticular connective tissue 2. dense • • • dense regular dense irregular elastic connective 3. cartilage • • • hyaline fibrocartilage elastic cartilage 4. bone 5. liquid • blood Figure 4.4 Table 4.2a Table 4.2b Table 4.2c Table 4.2d Table 4.2e Table 4.2f Table 4.2g Table 4.2h Table 4.2i Table 4.2j Table 4.2k Muscular Tissues Muscular Tissue • • • • • generates physical force needed to make body structures move produces movement maintains posture generates heat three types 1. skeletal 2. cardiac 3. smooth Skeletal Muscle • • • • • • striated long cells (up to 30-40cm) cylindrical in shape many nuclei at periphery of cell fibers are parallel voluntary Cardiac Muscle • • • striated branched single nucleus at center of cell – sometimes two nuclei • intercalated discs – cell junctions • • • strengthen tissue and hold cells together provide route for quick conduction of impulses involuntary Smooth Muscle • • • • • • nonstriated unbranched small spindle shaped (thick middle, tapered ends) single nucleus at center of cell involuntary Table 4.3 pt 1 Table 4.3 pt 2 Table 4.3 pt 3 Nervous Tissues • Nervous Tissue two principal types of cells 1. neurons – sensitive to various stimuli – convert stimuli into impulses – conduct impulses to: 1. other neurons 2. muscular tissue 3. glands – parts of a cell 1. cell body 2. dendrites 3. axon 2. neuroglia – smaller than neurons – support, nourish, protect neurons Table 4.4 Tissue Repair • Tissue Repair ability to repair depends on – extent of damage – tissue type • epithelium – continuous capacity for renewal • connective – some have continuous capacity for renewal – others replenish less readily because of smaller blood supply • muscle – relatively poor capacity for renewal • nervous – poorest capacity for renewal Tissue Repair • New cells originate by cell division from – parenchyma (functioning part of tissue) • repair will be near-perfect reconstruction – stroma (supporting connective tissue) • • • repair will include new connective tissue and scar formation will occur original function of tissue or organ is impaired tissue repair affected by – nutrition – blood circulation