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					                                         Chapter 4: Tissues

Human tissues are collections of cells and cell products that


Four types of tissues: Epithelial, Connective, Muscular, Nervous

I. Epithelial
       • "covering" and “lining”
       • form glands

       Characteristics of Epithelial Tissue:
       • cellularity: formed of closely joined cells – in sheets

       • polarity – 2 different surfaces
                Apical (exposed)
                Basal (attached) surface of cells


       • attachment – attached to connective tissue via basal lamina (basement membrane).


       • avascular –

       • regeneration-


       Functions of Epithelial Tissue:
       1.) Provide physical protection


       2.) Control Permeability (absorption/secretion)


       3.) Sensation


       4.) Produce secretions
              Glandular epithelium

       Specializations of Epithelial Cells

               Microvilli: extensions of cell membrane on the apical surface


               Cilia: hair like structures which beat


       Maintaining the Integrity of Epithelia
       1.) intercellular connections
       2.) attachment to basal lamina
       3.) epithelial maintenance & repair

       1. Intercellular Connections: anchor cell membranes
               cell adhesion molecules (CAMs)
               intercellular cement: glycosaminoglycans – hyaluronan

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       Cell Junctions – specialized areas in cell membrane
              a. Tight (occluding) junctions: impermeable

                       Lining of intestinal tract – lumen


               b. Gap junctions: cells held together by connexons (channel proteins)


               c. Desmosomes (macula adherens): in areas subject to mechanical stress
                      Held with CAMs and proteoglycans


2. Attachment to basal lamina
       Two layers:
              1.) lamina lucida

               2.) lamina densa


3. Epithelial Maintenance and Repair
       • cells often only live for days and die/shed

       • stem cells (germinative cells) deep and have rapid mitotic rate

       • damaged cells quickly replaced



Classified by the number of layers and the shape of cells (Table 4-1 pg. 113)
        A. Layers:
                simple:
                stratified:

       B. Shape of Cells:
             squamous:
             cuboidal:
             columnar:


       1. Simple Squamous: one layer

               -good for
               -found in the linings of


               -also known as mesothelium and endothelium



       2. Stratified Squamous:
              -most widespread
              -functions:

               -found in areas subject to friction: mouth, vagina, anus


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       3. Simple Cuboidal: one layer

              -have large spherical central nucleus
              -found in glands: thyroid & nephron


       4. Transitional:
              - stretches & recoils without damage
              - appearance changes as it stretches

              -found in urinary bladder


       5. Simple Columnar:
             - function for absorption, secretion, protection

              -found in lining of


       6. Psuedostratified Ciliated Columnar:
              -looks striated but it isn’t

              - cilia function for?

              -found in


Glandular Epithelium
Exocrine vs. Endocrine Glands
       Endocrine glands: secrete directly into blood
              Secretions termed:
              Examples:


       Exocrine glands: secrete through ducts
              Examples:


              modes of secretion (Figure 4-6 pg. 119)
              1.) Merocrine: exocytosis of secretions
                     Salivary glands secrete (mucin) or mucus
                     Merocrine sweat glands


              2.) Apocrine: apical portion of cell shed with secretions
                     Mammary glands


              3.) Holocrine: entire cell ruptures to release secretions
                      Sebaceous glands



              Types of secretions:
              1.) serous glands


                                                                          3
                      2.) mucous glands

                      glands can be simple or compound in structure


II. Connective
       Functions:
               1. binds                   &            together & supports structure
               2. framework for                        cells
               3. protects
               4. storage sites for

               5. forms rigid skeletal framework of body
               6. limits ROM

               7. transports                  fights                 (defense of body)

       Connective tissue consists of few cells with a lot of intercellular matrix (ground
       substance)


       Classification of Connective Tissues
       1.) Connective tissue proper
       2.) Fluid connective tissues
       3.) Supporting connective tissues


       1.) Connective Tissue Proper
              • contains fibers, ground substance & cells

       Cells associated with connective tissue proper
              1. fibroblast:
                      Secreted hyaluronan and protein fibers
                      Important for tissue growth & repair


               2. macrophages: phagocytes:


               3. adipocytes: store fat


               4. mesenchymal cells: stem cells


               5. melanocytes: produce melanin


               6. mast cells: release histamine & heparin

               7. lymphocytes: WBC


               8. microphages: neutrophils and eosinophils



                                                                                            4
Connective Tissue Fibers

      A. Collagenous: most abundant – “white fibers”
             Inelastic
             Strong


      B. Reticular: short, thin


      C. Elastic:


Types of Connective Tissue Proper:
1. Loose Connective Tissues – “packing peanuts”
      Areolar, Adipose, Reticular

      A. Areolar: most abundant
            •consists mostly of collagenous fibers

             •large spaces between cells:


             •unorganized fiber arrangement

             •functions:     1.attach skin
                             2. fill spaces

                             3. surround & support


      B. Adipose Tissue:
             •functions:


             • cells do not undergo mitosis throughout life

             • white vs. brown fat
                     Brown fat very metabolically active


             • visceral vs. subcutaneous fat:
                     Subcutaneous fat found below skin

                     Visceral found in abdomen (belly fat)


                     Waist: hip ratio
                            < 1 ideal (better: <.95 men,      < .8 women)



      C. Reticular Connective Tissue:
             •similar to loose connective tissue, contains ground substance in network of
             interlacing fibers
             •make up the inner framework in

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       2. Dense Connective Tissues – Connective tissues proper, tightly packed with
       high numbers of collagen or elastic fibers

       A. Dense Regular Connective Tissue:
             • tightly packed bundles of collagenous fibers

              • many fibroblasts


              1. tendons

              2. ligaments

              3. fascia

              4. aponeuroses



       B. Dense Irregular Connective Tissue:

              •fibers oriented randomly:


              •found in:     1. dermis
                             2. fibrous coverings: (perichondrium), (periosteum), &
                                     (perineurium)

                             3. capsules of many organs


       C. Elastic Connective Tissue:
              •contains more elastic than collagenous fibers
              •good for
              •found in walls of



2. Fluid Connective Tissues –
       A. Blood: watery mix of dissolved proteins
              contains formed elements (cells) and plasma

              Formed elements: RBC, WBC, platelets




       B. Lymph: fluid contains protein, lymphocytes, fats
             Similar to interstitial fluid
             Circulates via lymphatics

3.) Supporting Connective Tissues: Support soft tissues & body weight

       Cartilage
          • Gel-type ground substance
          • For shock absorption and protection

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Bone
  • Calcified (made rigid by calcium salts, minerals)
  • For weight support


A. Cartilage
       •numerous collagen fibers in a firm matrix contains:
       1.) Proteoglycans derived from chondroitin sulfates
       2.) Ground substance proteins
       3.) Chondrocytes (cartilage cells) surrounded by lacunae (chambers)


       •fibers/matrix formed by cells:
               -chondroblast:

               -chondrocytes


       •avascular: due to secretion of antiangiogenesis factor

               - surrounded by perichondrium
                       Outer fibrous layer
                       Inner cellular layer


Cartilage growth (both stop in adults)
        1.) interstitial growth: chondrocyte undergoes mitosis
                 growth from within cartilage
                 mainly during embryonic development - adolescence


       2.) appositional growth: new layers of cartilage added to surface


               -does not occur in adults


Types of cartilage
      1. Hyaline:
                -most abundant
                -provides support & reduces friction


               -precursor to bone (fetal skeleton), costal cartilage
               -also found in



       2. Fibrocartilage (fibrous)
              -collagen fibers in thick bundles
              -slightly compressible
              -found in regions that

               -intervertebral discs, knee joint: menisci
               and pubic symphysis


                                                                             7
                      3. Elastic -contains collagen but
                             -found in


       8. Bone or osseous tissue:
             • strong mineralized matrix
                     Calcium & phosphate salts
                     Resist shattering


               •osteoblast:

               • osteocyte:
                      Inside lacunae
                      Lacunae interconnected with canaliculi

               • 2 differences between bone and cartilage:
                        1. bone well supplied by
                        2. canaliculi


               • surrounded by periosteum


Membranes: physical barriers that line
     Consist of: an epithelium supported by

       1.) mucous membranes: secrete mucus (sticky)
              Found in


       2.) serous membranes: line ventral body cavities
               Visceral

               Parietal



       3.) cutaneous membrane: skin


       4.) synovial membranes

Fasciae: provides strength, stability, route for blood & lymp vessels

       1.) superficial (hypodermis): areolar & adipose tissue


       2). deep: dense irregular connective



       3.) subserous fascia: areolar tissue




                                                                        8
III. Muscular (Figure 4-18 page 136)
       •specialized for

      • contains actin & myosin: proteins which produce all body movements


      •3 types of muscle tissue: all made up of myosin, actin, collagen
             All contract

              1. skeletal: largest cells & striated
                      Found

                      Appearance: long
                            multinucleated

                      Specializations: myosatellite cells (satellite cells) – stem cells for skeletal
                      muscle


              2. cardiac: striated
                      Cardiocyte – cardiac muscle cell

                      Found
                      Appearance:

                      Specializations: intercalated discs


              3. smooth (visceral): nonstriated
                    Found
                    Appearance:


IV. Nervous (neural) Tissue (Figure 4-19 pg. 137)
         – Specialized for conducting electrical impulses

          –   Rapidly senses internal or external environment

          –   Processes information and controls responses

          –   Forms the brain, spinal cord, nerves
          –

      •Two types of cells: neurons & supporting cells (neuroglia)

      Neurons: conduct nerve impulses
            - 3 parts: dendrite, cell body & axon
                    Cell body contains organelles

              -amitotic
              -need continuous supply of?

      Neuroglia cells:




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Tissue Response to Injury: (pg. 139)
      Tissues respond to injuries to maintain homeostasis

      Cells restore homeostasis via:
             1.
             2.

      1. Inflammatory Response (inflammation)
      immediately after injury area is isolated while damaged cells and microorganisms are
      cleaned up

      • infection: presence of pathogens


      •Inflammation: short term (acute) inflammation has 4 symptoms:
             1.                     2.                    3.                     4.


      •what causes this?
      1. initial injury causes release of chemicals (histamine, heparin, prostaglandins)from
               neutrophils, macrophages, mast cells

             -these chemicals cause vasodilation of blood vessels which increases blood flow
             to injured area = heat, redness


             -histamine increases permeability – makes blood vessels “leaky” = swelling

             -swelling puts pressure on nerve endings = pain


             -why is this good?
                     1. helps dilute toxins & remove wastes

                     2. brings oxygen & nutrients

                     3. brings phagocytes

                     4. increases temperature

                     5. brings antibodies

                     6. removes toxins & wastes


             -necrosis: tissue/cell death

             lysosomes: release enzymes to destroy injured cells and surrounding area –
             produces debris, fluid, dead/dying cells known as pus

             abcess: accumulation of pus in enclosed tissue space


      2. stasis: "standing"
             -slowdown of blood flow


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           Repair: 2 major ways:

           1. regeneration:




           2. fibrosis: scar tissue




Read the text pages 138, 140 on aging, tissue structure & cancer. Also read Applications Manual
page 40 - Tissue Structure and Disease.

Inflammatory Conditions:
Arthritis

Asthma

Colitis:

TX:
Ice therapy:

Non-steroidal anti-inflammatory drugs (NSAIDs – such as aspirin, ibuprofen or naproxen)

Corticosteroids (such as prednisone)



Note:
C-reactive protein (hs-CRP) assay: measures levels of C-reactive protein
       Increases during acute inflammation




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posted:11/13/2011
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