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Chapter 4:: Tissues
Tissue Level of Organization
| Question | Answer |
|---|---|
| Tissues | Collections of specialized cells and cell products that perform a relatively limited number of functions; combine to form organs. |
| 4 Tissue Types | Epithelial Connective Muscle Neural |
| Define Epithelial Tissue | Tissue composed of layers closely spaced cells that cover organ surfaces (epithelia) and form glands. |
| Functions of Epithelial Tissue | -Protection (isolate external environment from cell) -Absorption/Control Permeability -Sensation (detect stimuli with large sensory nerve supply) -Secretion Production (higher # of ER, with Glandular Epithelial Tissue) |
| Glandular Epithelium | Epithelia containing gland cells scattered throughout that produce secretions into surface (for physical protection or temp regulation) or into surrounding interstitial fluid and blood (chemical messengers). |
| Define Interstitial Fluid | The liquid between the cells of the body. |
| Characteristics of Epithelial Tissue | -Cellularity -Polarity -Attachment -Avascularity -Regeneration |
| Epithelia Cellularity | Composed of bound cells in a matrix. Unlike other tissue types' cells that are often widely separated by extracellular materials. |
| Epithelia Polarity | An uneven distribution of cytoplasmic components and function between apical (exposed) surface and basal (attached) surface. |
| Epithelia Attachment | Attached to underlying connective tissues by a basal lamina. |
| Epithelia Regeneration | Germanative stem cells at base continually replace short-lived epithelial cells at outer surface. |
| Epithelial cell Specializations | Strongly polar individual cells may be specialized for: -movement of fluids over surface for protection and lubrication -movement of fluids to control permeability -production of secretions that provide protection or act as chemical messengers |
| Functional regions of epithelia | Apical surface (exposed to an internal or external environment) vs. basolateral surface (includes base, where cells attached to deeper cells or tissues, and sides, where the cell contacts its neighbors) |
| Specializations of Apical Surface | Transport (w/ microvilli that increase surface area for absorption) or movement/lubrication (ciliated epithelium) |
| Intercellular connections | General connection: -Cell Adhesion Molecules (CAMs) -Intercellular Cement Specialized connection sites/cell junctions: -Occluding/Tight Junctions -Gap Junctions -Desmosomes/Macula Adherens (spot or hemi-) |
| Cell Adhesion Molecules | Transmembrane proteins that connect large areas of opposing cells' plasma membranes |
| Intercellular Cement | A thin later of proteoglycans that contain polysaccharide derivatives known as glycosaminoglycans (esp. hyaluronan) that hold adjacent cell membranes together. |
| Occluding/Tight Junctions | Sites between lipid portions of two opposing plasma membranes tightly bound by interlocking membrane proteins. Prevents water and solute passage, and isolates wastes in the lumen. |
| Gap Junctions | Sites between cells, are held together by interlocking junctional (channel) proteins called connexons. Allow rapid communication by allowing ions to pass, coordinate heart muscle contractions. |
| Spot Desmosomes/Spot Macula Adherens | Sites between cell plasma membranes linked by CAMs (bricks) and intercellular cement (cement). Ties cells together by "dense areas", which are connected to cytoskeleton (reason peeling dead skin comes off in sheets) and allows bending and twisting. |
| Hemidesmosomes | Resembles half of a spot desmosome. Connects cell to extracellular filaments in the basal lamina. |
| Classification of Epithelia by Shape | Squamous (flat), cuboidal (box-like), or columnar (tall box-like). |
| Classification of Epithelia by Number of Cell Layers | Simple (single layer) or stratified (multiple layers) |
| Transitional Epithelium | Tolerates cycles of stretching and recoiling without damage, appearance changes from shorter and stretched to taller and relaxed. Found in urinary linings. |
| Pseudostratified Columnar Epithelium | Appears to be multiple layers, however is irregular cells that all touch basal lamina. Typically ciliated. Found in respiratory linings, portions of male reproductive tract. |
| Simple vs. Stratified locations | Simple found in already protected areas, regions of secretion or absorption. Stratified found in areas in need of protection. |
| Simple Squamous | Single layer of flat cells. Most delicate. Located in regions of absorption or diffusion, or where slick, slippery surfaces reduce friction. (mesothelium=lines ventral body cavity, endothelium=lines inner heart surface, vessels) |
| Stratified Squamous | Multiple layers of flat cells. On exposed body surfaces (top layers toughened with keratin), internal surfaces of severe mechanical stresses (nonkeratinized). |
| Simple Cuboidal | Single layer of box-like cells. Found where slight protection is needed, and secretion/absorption occurs. |
| Stratified Cuboidal | Multiple layers of box-like cells. Rare, located along gland ducts. |
| Simple Columnar | Single layer of tall box-like cells. Located where stronger protection is needed and secretion/absorption occurs. |
| Stratified Columnar | Multiple layers of box-like and tall box-like (superficial) cells split into 2 or more sub-layers. Found in a few large ducts, provide protection. |
| Endocrine Glands | Ductless, hormone glands. (touched on in later chapters) |
| Exocrine Glands | Glands that release their secretions into ducts that open onto an epithelial surface or on a lining of an internal passageway that communicates with the exterior. (ie sweat, tears, milk, etc) |
| Modes of Secretion | Merocrine, apocrine, holocrine |
| Merocrine Secretion | Product released from secretory vesicles by exocytosis. Most common mode of secretion. Cell stays in tact. |
| Apocrine Secretion | Involves the loss of cytoplasm along with the secretory product collected at the apical surface of the cell. Cell pretty much fully in tact. |
| Holocrine Secretion | Entire cell becomes packed with secretory products, then bursts to release secretion. Cell is killed in the process. |
| Types of Secretion | Serous (water+enzymes), mucous (water+mucins->mucous), mixed (more than one gland cell type, may produce 2 different secretions). |
| Define Connective Tissue | Tissue that provides a structural framework that stabilizes the relative positions of the other tissue types; connects the epithelium to the rest of the body. |
| Functions of Connective Tissue | -Structural framework -Transport -Protection -Support, surround, interconnect other tissue -Energy Reserve -Defense (in blood & lymph, can provide immune response) |
| Types of Connective Tissue | CT Proper, CT Fluid, and Supporting CT. |
| Connective Tissue Proper | Connective tissue containing extracellular fibers, a viscous ground substance, and a varied cell population. |
| Cell Populations of Connective Tissue Proper | -fibroblasts -fibrocytes -adipocytes -mesenchymal cells -mast cells -macrophages -lymphocytes -microphages -melanocytes |
| Fibroblasts | Cells found in all connective tissue proper that secretes proteins and hyaluronan/cell cement (extracellular matrix). The most abundant cell type. |
| Fibrocytes | Cells found in all connective tissue proper that maintain the fibers of connective tissue proper. The 2nd most abundant cell type. |
| Adipocytes | Fat cells, each of which stores a single large fat droplet. |
| Mesenchymal Cells | Stem cells that respond to injury or infection. Differentiates into whatever lost cell it needs to replace within the CT proper population. |
| Mast Cells | Stimulate inflammation after injury or infection. Releases histamine and heparin to trigger healing chain. |
| Basophils | Leukocytes (white blood cells) that also contain histamine and heparin. |
| Macrophages | Large, amoeba-like cells of the immune system. Eat pathogens and damaged cells. |
| Fixed vs. Free Macrophages | Fixed=stay in designated tissue Free=migrate throughout body |
| Lymphocytes | Specialized immune cells in the lymphatic (lymphoid) system. For example, may develop into plasma cells (plasmocytes) that produce antibodies. |
| Microphages | Phagocytic blood cells that respond to signals from macrophages and mast cells. Includes neutrophils and eosinophils. |
| Melanocytes | Synthesize and store the brown pigment melanin. |
| Connective Tissue Fibers | -Collagen Fibers -Elastic Fibers -Reticular Fibers -Ground Substance |
| Collagen Fibers | Most common fibers in CT Proper. Long, straight, unbranched, strong, and flexible. Resists force in ONE direction. (ie tendons and ligaments). |
| Elastic Fibers | Contain the protein elastin. Branched and wavy, returns to original length after stretching. (ie elastic ligaments of vertebrae) |
| Reticular Fibers | Network of interwoven fibers (stroma). Strong and flexible. Resists force in MANY directions. Stabilizes functional cells (parenchyma) and structures. (ie sheaths around organs) |
| Ground Substance | A clear, colorless, viscous substance that fills spaces between cells to slow pathogen movement to slow the spread of infection. |
| Types of Connective Tissue Proper | -Loose (areolar, adipose, reticular) -Dense (regular, irregular, elastic) |
| Loose Connective Tissues | The "packing materials" of the body. Fill spaces between organs, cushion and stabilize specialized cells in many organs, and support epithelia. Surround and support blood vessels and nerves, store lipids, and provide a route for the diffusion of materials |
| Areolar Tissue | -loose tissue -least specialized -viscous ground substance makes up most of the volume, absorbs shocks -loosely organized fibers (including elastic) -HIGHLY vascular (holds blood vessels and capillary beds -example=under skin/subcutaneous layer |
| Adipose Tissue | Fat tissue. Volume mostly made up of adipocytes (fat cells). Regenerative. Provides padding, absorbs shocks, acts as an insulator to slow heat loss through the skin, and serves as a packing or filler around structures. Can be white fat or brown fat. |
| White Fat | -Most common -stores fat -absorbs shocks -slows heat loss |
| Brown Fat | -More vascularized -many fat cells contain mitochondria -when stimulated by nervous system, fat breakdown speeds up, releasing energy -absorbs energy from surrounding tissue as heat -rarely found in adults |
| Reticular Tissue | Stabilize functional cells (parenchyma) of some organs with supporting framework of reticular fibers (stroma). |
| Dense Connective Tissue | Tightly packed, parallel collagen fibers. Most of the volume is made up of fibers, mostly collagen fibers. |
| Examples of Dense CT | Tendons (attach muscle to bone), ligaments (connect bones, stabilize organs), aponeuroses (attach in sheets to large, flar muscles). |
| Types of Dense CT | Dense Regular, Dense Irregular, and Elastic Tissue |
| Dense Regular Connective Tissue | Provides firm attachment, conducts pull of muscle, reduces friction between muscles, stabilizes relative positions of bones. |
| Dense Irregular Connective Tissue | Provides strength to resist forces applied from many directions, helps prevent overexpansion of organs such as the urinary bladder. |
| Elastic Tissue | Stabilizes positions of the vertebrae and penis, cushions shocks, permits expansion and contraction of organs. |
| Fluid Connective Tissues | Blood and lymph |
| Blood | Liquid plasma + formed elements (RBCs, WBCs, platelets) |
| Erythrocyte | AKA red blood cell. Red cells in blood that transport oxygen (and to a lesser degree, CO2). Makes up almost half of the volume of the blood. |
| Leukocyte | AKA white blood cells. Important components of the immune system. Include the phagocytic microphages (neutrophils and eosinophils), basophils, lymphocytes, and monocytes, cells related to the macrophages found in other connective tissues. |
| Platelets | Tiny membrane-enclosed packets of cytoplasm. Contain enzymes and special proteins, function in clotting response that seals breaks in the endothelial lining. |
| Arteries | Carry blood away from the heart into body tissues. |
| Capillaries | Smallest blood vessels. Thin wall permits the diffusion of gases, nutrients, and wastes between plasma and interstitial fluids. |
| Veins | Carry blood from capillary bed, back to the heart. |
| Lymph | Checks for infection. |
| Supporting Connective Tissue | Provide a strong framework that supports the rest of the body. Includes bone and cartilage. |
| Cartilage | A firm gel that contains polysachharide derivatives called chondroitin sulfates. Avascular, so all nutrient and waste exchange is done by diffusion through the matrix. |
| Chondrocytes...Lacunae | Cartilage cells. The only cells in the cartilage matrix, occupy small chambers called lacunae. |
| Cartilage Matrix | Chondroitin sulfates mixed with proteins in the ground substance, producing proteoglycans. Physical properties of cartilage dependent on the matrix proteoglycans as well as type and abundance of extracellular fibers (ie collagen=strength, flexibility). |
| Cartilage Growth Mechanisms | Interstitial growth and appositional growth |
| Interstitial Growth | Cartilage cells undergo cell division, daughter cells produce additional matrix. Enlarges cartilage from within. Begins in early embryonic development through teen years. [interstitial=split] |
| Appositional Growth | New layers of cartilage are added to the surface, with the inner layer of the perichondrium undergoing repeatedly dividing and differentiating into immature cartilage cells. Increases cartilage size by adding to its outer surface. |
| Types of Cartilage | Hyaline, elastic, and fibrous |
| Hyaline Cartilage | Provides stiff but somewhat flexible support; reduces friction between bony surfaces. Contains closely packed collagen fibers. ie between synovial joints |
| Elastic Cartilage | Provides support, but tolerates distortion without damage and returns to original shape. Contains high amount of elastin fibers. ie ear |
| Fibrous Cartilage | Resists compression; prevents bone-to-bone contact; limits relative movement. Matrix is dominated by densely interwoven collagen fibers, making the tissue extremely durable and tough. ie between spinal discs |
| Structural Differences between Bone and (Cartilage) | Osteocytes in lacunae (vs. chondrocytes), ground substance is small volume of liquid surrounding calcium salt crystals, mostly collagen fibers (vs. collagen, elastic, and reticular), vascular, doesnt bend but breaks at certain point(vs bend but not break) |
| Metabolic Differences between Bone and (Cartilage) | High oxygen demands (vs. low) , delivers nutrients through cytoplasm and fluid in caniculi/outer branches (vs. diffusion through matrix), only appositional only (vs. interstitial and appositional), extensive repair capabilities (vs. limited). |
| Body Membrane Types | Mucous, serous, cutaneous, synovial. |
| Mucous Membrane | Line passageways and chambers that communicate with the exterior. Epithelial lining must be kept moist with mucus or other fluids to reduce friction and sometimes facilitate absorption or secretion |
| Serous Membrane | Line the sealed, internal subdivisions of the ventral body cavity. Very thin, but firmly attached to the body wall and organs they cover. Minimize friction between the parietal portion (inner body cavity surface) and the visceral portion (organ surface). |
| Cutaneous Membrane | AKA skin. Covers the body surface. Consists of stratified squamous epithelium and a layer of areolar tissue reinforced by underlying dense irregular CT. Thick, relatively water-proof, and usually dry. |
| Synovial Membranes | Lines the synovial joint cavities. Consists of an extensive area of areolar tissue containing a matrix of interwoven collagen fibers, proteoglycans, and glycoproteins. Produce synovial fluid. Provides lubrication for cartilage around joints. |
| Fasciae: Definition and functions | Framework of connective tissue layers and wrappings that support and surround organs. Functions: provide strength and stability, maintain the relative positions of organs, and provide route for blood vessels. |
| Types of Fasciae | -superficial/subcutaneous -deep -subserous |
| Superficial Fascia | AKA subcutaneous layer or hypodermis. Layer of areolar tissue and fat that separates the skin from underlying tissues and organs, providing insulation and padding, and letting the skin and underlying structures move independently. |
| Deep Fascia | Consists of dense irregular connective tissue. In each layer of fibers run in same direction, but changes between layer. Outer layers of bones and ligaments and the connective tissues of muscles are connected to deep fascia as well as organs. |
| Subserous Fascia | Layer of areolar tissue that lies between the deep fascia and serous membranes that line body cavities. Not distorted by muscle movement. |
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