Collin College. BIOL Chapter 4. Tissue Levels CONNECTIVE TISSUE. C.T. derives from Mesenchyme embryonic tissue.

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1 Collin College BIOL Chapter 4 Tissue Levels. CONNECTIVE TISSUE C.T. derives from Mesenchyme embryonic tissue. Depending on the stimuli, mesenchyme develops into specific cells that give rise to the different C.T. types The cells of each C.T. type secrete a surrounding matrix The majority of connective tissue is the matrix; it is made out of ground substance extra-cellular protein fibers Depending on the type of C.T., the matrix will be fluid and flexible with few or many cells solid and rigid with few or many cells 1

2 CONNECTIVE TISSUE Functions Establishes structural frameworks Transport fluids and dissolved materials Protect delicate organs Support, surround and interconnect tissues Store energy reserves and minerals Defend the body from microorganisms CLASSIFICATIONS 2

3 CLASSIFICATIONS COMPOSITION AND ORGANIZATION Connective tissue proper Contains largest variety of cells, has viscous ground substance and different fibers Fibroblasts produce the fibers Macrophage engulf pathogens Adipocytes fat-storing cells Mesenchymal cells stem cells Types of Cells Types of Fibers Collagen fibers flexible, high strength Melanocytes pigment producers Mast cells trigger inflammation Lymphocytes attack foreign antigens Microphages engulf cell remnants Elastic Fibers coiled fibers with elastic properties Reticular supporting network fibers 3

4 Cells of Connective Tissue Proper Fibroblasts The most abundant cell type: Found in all connective tissue proper Secrete proteins and hyaluronan (cellular cement) Fibrocytes The second most abundant cell type Found in all connective tissue proper Maintain the fibers of connective tissue proper Adipocytes Fat cells : each cell stores a single, large fat droplet Mesenchymal Cells Stem cells that respond to injury or infection Differentiate into fibroblasts, macrophages, etc. Cells of Connective Tissue Proper Macrophages Large, amoeba-like cells of the immune system Eat pathogens and damaged cells. Fixed macrophages stay in tissue, Free macrophages migrate Mast Cells Stimulate inflammation after injury or infection Release histamine and heparin Lymphocytes Specialized immune cells in lymphatic (lymphoid) system For example, lymphocytes may develop into plasma cells (plasmocytes) that produce antibodies 4

5 Fibers of Connective Tissue Proper Collagen Fibers Most common fibers in connective tissue proper Long, straight, and unbranched Strong and flexible ; resist force in one direction For example, tendons and ligaments Reticular Fibers Network of interwoven fibers (stroma) Strong and flexible as well ; resist force in many directions Stabilize functional cells (parenchyma) and structures For example, sheaths around organs Elastic Fibers Contain elastin Branched and wavy; return to original length after stretching For example, elastic ligaments of vertebrae Ground Substance Connective Tissue Proper Ground Substance Is clear, colorless, and viscous Fills spaces between cells and slows pathogen movement Important note : fibers and ground substance are found in all connective tissues. Connective tissue proper just has a lot more variety of cells 5

6 CELLS AND FIBERS OF C.T. PROPER Reticular fibers Melanocyte Fixed macrophage Plasma cell Mast cell Elastic fibers Free macrophage Collagen fibers Blood in vessel Fibroblast Adipocytes (fat cells) Mesenchymal cell Ground substance Lymphocyte COMPOSITION AND ORGANIZATION Connective tissue Proper Classified as Loose or Dense Loose Embryonic mesenchyme, mucous connective tissues Areolar tissue Adipose tissue Reticular tissue Dense Dense regular CT Dense irregular CT 6

7 Mesenchyme Mesenchyme Tissue is Embryonic Connective Tissues Is not found in adults, but mesenchyme cells remain in many connective tissue proper It can differentiate into new connective tissues when properly stimulated Blood vessel Mesenchymal cells LM 136 This is the first connective tissue to appear in an embryo. Areolar Connective Tissue Areolar Tissue Least specialized Open framework with Viscous ground substance Elastic and collagen fibers Found under many simple epithelial tissues (in lamina propria)- holds blood vessels and capillary beds LOCATIONS: Within and deep to the dermis of skin, and covered by the epithelial lining of the digestive, respiratory, and urinary tracts; between muscles; around joints, blood vessels, and nerves FUNCTIONS: Cushions organs; provides support but permits independent movement; phagocytic cells provide defense against pathogens Fibrocytes or fibroblasts Macrophage Collagen fibers Mast cell Elastic fibers 7

8 ADIPOSE AND RETICULAR C.T. Adipose Tissue Contains many adipocytes (fat cells) Two types of adipose tissue 1. White fat Most common and Stores fat Absorbs shocks/slows heat loss (insulation) 2. Brown fat More vascularized tissue Adipocytes have many mitochondria When stimulated by nervous system, fat breakdown accelerates, releasing energy Absorbs energy from surrounding tissues Reticular Tissue Provides support via complex, three-dimensional network Supportive fibers (stroma) support functional cells (parenchyma) The form structural Reticular organs such as spleen, liver, lymph nodes, and bone marrow ADIPOSE AND RETICULAR C.T. Adipose Tissue LOCATIONS: Deep to the skin, especially at sides, buttocks, and breasts; padding around eyes and kidneys FUNCTIONS: Provides padding and cushions shocks; insulates (reduces heat loss); stores energy Adipocytes (white adipose cells) Adipose tissue LM 300 Reticular Tissue LOCATIONS: Liver, kidney, spleen, lym ph nodes, and bone m ar r ow FUNCTIONS: fr am ewor k Provides supporting Reticular fibers Reticular tissue from liver Reticular tissue LM 375 8

9 DENSE C.T. DenseRegular Connective Tissue Tightly packed, parallel collagen fibers Tendons attach muscles to bones Ligaments connect bone to bone and stabilize organs Aponeuroses attach in sheets to large, flat muscles Dense Irregular Connective Tissue Interwoven networks of collagen fibers Typical in the dermis of the skin Around cartilages (perichondrium) and bones (periosteum) Form capsules around some organs (e.g., liver, kidneys) DENSE C.T. 9

10 DENSE ELASTIC TISSUE Made mostly of elastic fibers For example, elastic ligaments between spinal vertebrae FLUID CONNECTIVE TISSUE Blood and lymph = a watery matrix of dissolved proteins Carry specific cell types (formed elements) Formed elements of blood RBC s(erythrocytes), WBC s(leukocytes), Platelets Lymphatic system returns extra interstitial fluid back to blood fluid it monitored by immune system 10

11 SUPPORTING CONNECTIVE TISSUE Cartilage and bone support soft tissues and the rest of the body Cartilages : Matrix is a firm gel containing chondroitin sulfate and protein fibers Cells are called chondrocytes Cells are found in lacunae ( living areas ) Perichondrium separates cartilage from surrounding tissues Chondrocytes produce an anti-angiogenesis factor prevents the development of blood vessels into cartilage ( they are thus avascular) Cannot get too thick nutrients passage and healing factors are dependent on diffusion Three types: hyaline, elastic and fibrocartilage SUPPORTING CONNECTIVE TISSUE Hyaline Cartilage Stiff, flexible support most common cartilage Reduces friction between bones and protects Found in synovial joints, rib tips, sternum, Keeps the trachea open Usually, lacunae are large and not touching, fibers not visible 11

12 SUPPORTING CONNECTIVE TISSUE Elastic cartilge Supportive but bends easily Found in external ear and epiglottis Lacunae very close to each other with visible thin elastic fibers between Fibrocartilage (Fibrous Cartilage) Limits movement - Prevents bone-to-bone contact Found between pubic bones and intervertebral discs Lacunae are tiny and occur in small groups far apart Fibers sometimes visible as smears Elastic Cartilage LOCATIONS: Auricle of external ear; epiglottis; auditory canal; cuneiform cartilages of larynx FUNCTIONS: Provides support, but tolerates distortion without damage and returns to original shape Chondrocytes in lacunae Elastic fibers in matrix Elastic cartilage LM 358 Fibrocartilage LOCATIONS: Pads within knee joint; between pubic bones of pelvis; intervertebral discs FUNCTIONS: Resists compression; prevents bone-to-bone contact; limits movement Chondrocytes in lacunae Fibrous matrix LM 400 Fibrocartilage 12

13 SUPPORTING CONNECTIVE TISSUE BONE Has osteocytes located in lacunae In compact bone, they are located in concentric circles around a central canal containing blood vessels Cells depend on diffusion through canaliculi for nutrients Little ground substance but dominating collagen protein fibers provide limited flexibility within a dense mineralized matrix hard to break unless changes occur within matrix Surrounded by periosteum BONE CONNECTIVE TISSUE Osteon Canaliculi Osteocytes in lacunae Matrix Central canal Fibrous layer Cellular layer Periosteum Blood vessels Osteon LM

14 MUSCLE TISSUE Specialized for contraction Three types Skeletal muscle : Striated and voluntary Cardiac muscle : Striated and involuntary Smooth muscle : not striated and involuntary Striations in muscle are due to a very organized arrangement of the two contractile protein strands : actin and myosin MUSCLE TISSUE Skeletal Muscle Tissue Cells are long, cylindrical, striated, and multinucleate. LOCATIONS: Combined with connective tissues and neural tissue in skeletal muscles Striations Nuclei FUNCTIONS: Moves or stabilizes the position of the skeleton; guards entrances and exits to the digestive, respiratory, and urinary tracts; generates heat; protects internal organs a Skeletal muscle Muscle fiber LM 180 Very long/thin cells that are multinucleate They have a striated appearance They are our voluntary muscle Divide/regenerate via satellite cells 14

15 MUSCLE TISSUE Cardiocytes occur only in the heart Microscopic short cells that are branched and connect via intercalated discs They are striated involuntary muscle Rely on pacemaker cells for regular contraction MUSCLE TISSUE They are not striated and short, tapered cells ---- involuntary muscle Found everywhere motion is needed inside the body 15

16 NEURAL TISSUE Conducts electrical impulses Conveys information from one area to another CONTAINS TWO MAIN TYPES OF CELLS Neurons Transmit electrochemical signals Organized into a cell body, axon, and dendrites Dendrites receive the information and electrical information is guided down the axon to other neurons Neuroglia : Support neural tissue and help supply nutrients to neurons NEURAL Tissue 16

17 BODY SYSTEM MEMBRANES They Form barriers to protect organs They are Composed of epithelium and connective tissue Four types Cutaneous Synovial Serous Mucous Body membranes 17

18 Cutaneous Membranes Cutaneous membrane = skin A dry membrane Outermost protective boundary Superficial epidermis Keratinized stratified squamous epithelium Underlying dermis Mostly dense irregular connective tissue Mucous Membranes Lines passage ways that communicate with the exterior Must be kept moist to reduce friction The epithelial layer is lubricated by mucus from goblet cells or via multicellular glands The epithelial layer can be simple (ex : lining of intestine) or stratified (ex: lining of mouth) The connective tissue layer under these membranes is called the lamina propria and is mostly areolar C.T. 18

19 Serous Membranes Line the sealed internal subdivisions of the ventral body cavity ( cavities that DO NOT open to the exterior) 3 main types of serous membranes are The pericardium The pleura The peritoneum Each serous membrane has two layers to it The parietal portion : attaches to the inner surface of the body cavity ( body wall) The visceral portion or serosa : covers the outer surface of the organ involved. The epithelial layer is lubricated by mucus from goblet cells or via multicellular glands Serous Membranes Serous layers are separated by serous fluid 19

20 Synovial Membranes Composed out of only Connective tissue only Lines fibrous capsules surrounding joints CONNECTIVE TISSUE FRAMEWORK Layers of CT connect the organs within the dorsal and ventral body cavities The layers provide strength, maintain position of organs and provide routing areas for bloodvessesl and nerves Fasciae are connective tissue layers that support and surround organs Superficial Fascia or Subcutaneous layer also called the Hypo dermis ( located under the dermis layer) areolar CT and fat Deep fascia dense irregular CT Subserous fascia layer of areolar CT between deep fascia and serous membranes 20

21 CONNECTIVE TISSUE FRAMEWORK 21