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Transcript
Anatomy: Chapter 4 Epithelial Tissue Sheet of cells that covers a body surface or lines a body cavity Forms boundaries between different environments Outer layers of skin, lines open cavities of cardiovascular and respiratory systems Epidermis of skin, bladder Serves many functions Protection – skin protects from infection, injury Absorption- digestive tract specialized Filtration- kidneys performs all the next 3 Excretion Secretion - glands Sensory reception Characteristics of Epithelium Cellularity Specialized contacts Polarity Supported by CT Avascular but innervated Regeneration Characteristics of Epithelium Cellularity Composed almost entirely of closely packed cells Very little extracellular space Specialized contacts Fit close together to form continuous sheets Bound by lateral contacts called tight junctions or desmosomes Characteristics of Epithelium Polarity Have apical or exposed surface and basal or attached surface Polarity means cells near apical surface differ from those near basal surface in both structure and function Apical – are smooth with microvilli Basal lamina- thin supporting sheet for basal surface. Non cellular, acts like tape for cells. Made of glycoproteins Very sticky Supported by CT Rests upon CT and is supported by CT Just below basal lamina is the reticular lamina Contains fine network of collagen fibers that belong to underlying CT Basal lamina + reticular lamina = basement membrane Basement membrane defines epithelial boundary Characteristics of Epithelium Avascular but innervated Contains no blood vessels Supplied by nerve fibers Nourished by diffusion from blood vessels Regeneration High regeneration capacity Often removed by abrasion As long as nutrition is adequate then they can replace at a high rate Classifications of Epithelia Simple vs Stratified Simple Stratified Squamous vs Columnar vs Cuboidal Squamous Columnar Cuboidal Simple Epithelia Simple – made of a single layer of cells Typically found where absorption and filtration occurs Sub levels to follow Simple Squamous Epithelia Single layer of flattened cells with disc shaped central nuclei and sparse cytoplasm Function: passage of materials by diffusion Location: kidney, alveoli of lungs, blood vessels, lymphatic vessels Simple Cuboidal Epithelium Single layer of cubelike cells with large central nuclei Function: secretion and absoption Location: kidney tubules, ducts of small glands, ovary surface Simple Columnar Epithelium Single layer of tall cells with oval nuclei; some have cilia or mucus secreting cells Function: absoption, secretion of mucus and enzymes Location: nonciliated lines digestive tract, gallbladder, and excretory system Pseudostratified Columnar Epithelium Single layer of cells of differing heights, some not reaching apical surface, nuclei seen at different levels, may contain goblet cells or cilia Function: secretion(mucus), ciliary action Location: trachea and upper respiratory tract Stratifed Epithelium All contain 2 or more layers of cells Regenerate from basal cells (from below) Considerably more durable than simple epithelia cells Typically used for protection Stratified Squamous Epithelium Thick membrane composed of several cell layers, basal cells are cuboidal/columnar and metabolically active, upper cells flattened Function: protects from abrasion Location: mouth, esophagus, epidermis of skin Stratified Columnar Epithelium Several cell layers, base cells usually cuboidal, superficial cells elongated and columnar Location: rare in body, urethra and large glands Function: protection, secretion Transitional Epithelial Tissue Resembles both strat. Squamous and strat. Cuboidal. Basal cells cuboidal or columnar; surface cells domed Function: distention of urinary organ (helps you pee) Location: lines ureters, bladder, and part of urethra Assignment Pg. 147 Questions 3 M.C. and 2 C. T. Connective Tissue Found literally everywhere in the body Most abundant and widely distributed of the primary tissues Class of C.T. C.T. Proper Cartilage Bone blood Functions of C.T. Binding and Support Protection Bone and cartilage Transportation Bone and cartilage blood Insulation Fat (adipose tissue) Common Characteristics of C.T. Common origin Degrees of vascularity Arise from mesenchyme (embryonic) Range from avascular (cartilage) to poorly vascular (dense CT) to very vascular (tissue that supply blood vessels) Extracellular Matrix (ECM) Non-living womb Allows CT to bear weight, withstand great tension, and endure abuses. Structural Elements of C.T. Ground Substance Fibers Cells Properties of cells and composition and arrangement of ECM vary greatly Tough: tendons and ligaments Fragile: around organs Structural Elements of C.T. Ground Substance Unstructured material that fills space between cells Composed of: Interstitial fluid Cell adhesion proteins Act like cell glue Proteoglycans Have core that GAG’s attach to GAG = glycosaminoglycans High GAG content = stiffer ground substance Holds large amounts of fluid and fuction as molecular sieve Fibers Provide support 3 types Collage Elastic Reticular Collagen strongest and most abundant Collagen fibers Made of strong protein “collagen” They are extremely strong and have a high tensile strength Tests have shown that collagen fibers are stronger then steel fibers of the same size White in color; called “white fibers” Elastic fibers Made of a very rubbery, stretchy protein called “elastin” These fibers can stretch and recoil much like a rubber band They are found in skin, lungs, and blood vessels, where there is much elasticity needed Fresh fibers are yellow in color; called “yellow fibers” Reticular fibers Made of very fine collagenous fibers Branch extensively and form very delicate networks Support soft tissue of organs Abundant where CT meets other tissue Ex: basement membrane of epithelium or capillaries Cells Types Both immature and mature forms exist “blast” cells are the forming cells “cyte” cells are the mature cells Blast cells are very mitotic and secrete ground substance and ECM Primary Blast Cells Fibroblasts Chondroblasts Form cartilage Osteoblasts Form CT Proper Form bone Hematopoietic stem cells Form blood Primary Blast Cells to “Cytes” After ECM and ground substance are synthesized then the cells assume their mature “cyte” form These mature cells maintain the health of the ECM, however if the matrix is injured they can revert back to their more active “blast” form and repair and regenerate the matrix Other Types of Cells Connective tissue is home to many other types of cells Fat cells White blood cells Mast cells Macrophages Plasma cells, these produce antibodies Mast cells and macrophages are important to overall body defense. Mast Cells and Macrophages Mast cells are oval shaped cells that cluster along blood vessels Their job is to detect foreign substances and initiate local inflammation Ex: bacteria, fungi, pathogens Macropahges are large irregular cells that avidly phagocytize the forgeign substances ( They eat ) Scattered throughout loose CT, bone marrrow and lymphatic tissue. Types of Connective Tissue Embryonic CT Mesenchyme, first definitive layer formed from mesoderm, embryonic germ layer Arises early in development and differentiates into all forms of CT Mucous CT Temporary, rare but also derived from mesenchyme CT Proper Loose CT Proper areolar Adipose reticular Dense CT Proper Dense regular Dense irregular elastic CT Proper - Loose Areolar CT Gel like matrix, 3 fiber types; contains fibroblasts, macrophages, mast cells and WBC Wraps and cushions organs, important in inflammatory response, holds tissue fluid Location: widely distributed under epithelia, packages organs, surrounds capillaries; forms lamina propia of mucous membranes More Areolar CT Gelatin like ground substance Holds liquids for all other cells Inflammatory response: When area is injured, areolar CT soaks up fluids and can cause edema Areolar is most widely distributed CT, essentially packing material for the body Loose CT Proper Adipose Tissue “fat” Very sparse matrix, closely packed adipocytes, nucleus pushed to side by large fat droplet Provide reserve fuel, insulation, supports organs Under skin, around kidneys and eyeballs, in abdomen, breast tissue More Adipose Tissue Similar in structure to areolar but able to store way more nutrients 90% of mass is adipocytes (fat cells) Highly vascular and metabolic “Brown fat”- different form Consumes stores and creates heat “White fat” – reglar adipose tissue Loose CT Proper Reticular Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network Form soft internal skeleton that supports other cells Location: lymphoid organ (bone marrow, spleen, lymph nodes) Dense Regular CT Parallel collagen fibers, few elastin fibers, main cell is fibroblast Attaches muscles to bones or to other muscles, attaches bones to bone Location: tendons, most ligaments Dense irregular CT Irregularly arranged collagen fibers, some elastic fibers, major cell is fibroblast Able to withstand tension is many directions Dermis of skin, fibrous capsule of organs and joints Cartilage Stands up to both tension and compression Qualities b/t dense CT and bone Avascular, lacks nerve fibers Ground substance contains large amounts of Chondroitin and hyaluronic acid Up to 80% water Closely bound collagen fibers and a few elastic fibers Chondroblast is primary cell More Cartilage Old cartilage loses its ability to divide Heals very slowly (Sports injuries) 3 types Hyaline Elastic fibrocartilage Hyaline Cartilage Most abundant cartilage Firm matrix, large number of collagen fibers “gristle” Supports, reinforces; cushioning properties Embryonic skeleton, costal cartilage More Cartilage Elastic Nearly identical to hyaline but with more elastin fibers in matrix Maintains shape while allowing flexibility External ear, epiglottis Fibrocartilage Similar to hyaline but less firm with larger collagen fibers High tensile strength with ability to resist compression Meniscus of knee, “discs” of back Other CT Bone Hard, calcified matrix Well vascularized Osteocyte is main cell Supports, protects, stores calcium, blood cell formation Skeleton Blood RBC and WBC in a fluid matrix Transports gases, nutrients, waste, etc Inside blood vessels Nervous Tissue Main component of the nervous system (brain, spinal cord, nerves) Regulate and control body functions Neurons – nerve cell; highly specialized cell that generates nerve impulses The Neuron Parts of the neuron Soma (cell body) Dendrites – highly branched Conduct and transmit nerve impulses Myelin sheath- white fatty substance Receive signals Axon – nerve fiber Contains organelles, carries on cell function Proteolipoid (mix of proteins and lipids) Insulates and speed up nerve impulses Axon terminal – links to dendrites to form synapse Neuron facts Extreme longevity They are amitotic They cannot replace themselves if destroyed High metabolic rate Given good nutrition can live up to 100 years Require constant supply of oxygen and glucose to function Very large complex cells Muscle Tissue Muscle tissue is: Highly cellular Well vascularized Responsible for most movements Made of myofilaments 3 types: Skeletal muscle Cardiac muscle Smooth muscle Skeletal Muscle Attached to bones of skeleton Form flesh of body and are responsible for movement of skeleton Muscle fibers are often striated in appearance. Long cylindrical multinucleated Fast Twitch vs Slow Twitch Cardiac Muscle Found only in walls of the heart Contractions propel blood through circulatory system Cells are branching, striated, uninucleated that fit closely/tightly together at junctions called intercalated discs Smooth Muscle No external striations Spindle shaped with central nucleus Found mainly in walls of hollow organs (urinary and digestive tract) Function is to squeeze substances along a path by contracting and relaxing Muscle contractions Voluntary = skeletal muscle Involuntary = smooth and cardiac muscle Other muscle functions: Maintaining posture (core,trunk) Generating body heat 40% of body mass Stabilizing joints Tissue Repair and Inflammation Step 1: Inflammation Step 2: Organization, 1st phase of tissue repair Step 3: Regeneration Step 1: Inflammation Tissue trauma causes injured cells to release inflammatory chemicals Capillaries dilate and become more permeable WBC and plasma w. antibodies flood the wound and form a clot Leftover stuff is phagocytized by macropahges Step 2: Organization Occurs while inflammation is going on Clot replaced by granuation tissue Granulation tissue has capillaries that bleed freely; also contains fibroblasts that produce growth factors that signal for repair Macrophages again digest leftover materials Step 3: Regeneration During repair, surface epithelium begins to regenerate Epithelium grows under scab until it resembles the epithelium around it Scar tissue may be present still The severity of the wound determines healing time and repair process varies across tissue types Germ Layers Ectoderm Mesoderm Forms epithelial tissues Muscle and all CT Endoderm Nervous tissue All primary tissues are developed and major organs formed by the 2nd month