Tissues

Tissues

1. Epithelial Tissues

   • Line body cavities and cover extrernal and internal body surfaces
   • Distinguishable by having little extracellular matrix between closely packed cells
   • Are avascular
   • Have a nerve supply
   • Have a high capacity for cell division
   • Apical, Lateral, and Basal Surface
   • Basement Membrane
   • Covering and Lining Epithelium
     • Simple
     • Stratified
     • PseudoStratified
   • Glandular Epithelium
   • 4 Types of Shapes
     • Squamous
     • Cuboidal
     • Columnar
     • Transitional

2. Connective Tissue

   • General Facts
     • Most abundant Tissue Type
     • The function depends on its form
     • Composed of variety of cells widely dispersed throughout an extracellular matrix
       • The extracellular matrix determines the tissue's qualities
       • Consists of a fluid, gel or solid ground substance, plus protein fibers
       • Ground Substance
         • consists of water and a variety of large biomolecules
   • Types of Cells
     • Fibroblasts
       • Large, flat, branching cells
       • Secrete fibers & ground substance of matrix
     • Macrophages
       • formed from white blood cells
       • Irregular shape with short, branching projections
       • Engulf bacteria and cell debris by phagocytosis
     • Plasma Cells
       • small cells that develop from white blood cells
       • Make antibodies
         • Proteins that attack or neutralize foreign invaders
       • Important in immune responses
     • Mast cells
       • abundant alongside the blood vessels
       • Produce Histamine
         • A chemical that dilates blood vessels as part of the inflammatory response
       • Also kill bacteria
     • Adipocytes
       • Fat Cells
       • Store Triglycerides
       • Found below the skin and around organs such as the heart and kidneys
   • Fibers
     • Collagen Fibers
       • Very strong and flexible
       • Occur in parallel bundles
       • Found in most types of connective tissue, especially bone, cartilage, tendons, and ligaments
     • Elastic Fibers
       • smaller than collagen and form branching networks
       • made of elastin
       • can stretch up to 1.5x their length
       • recoil after having been stretched
     • Reticular fibers
       • also smaller than collagen and form branching networks
       • Found in basement membranes and provide support for many soft organs
   • Classification of Connective Tissue
     • Loose Connective Tissue
       • Areolar
         • Widely distributed throughout the body
         • Combined with adipose tissue, it makes up the subcutaneous layer of skin
           • Anchors skin to underlying tissues and organs
       • Adipose
         • Found whenever areolar connective tissue is found
         • Vascular
         • Provides same function as lipids
       • Reticular
         • Consists of fine, interlacing reticular fibers and cells
         • Forms the stroma (supporting framework) of organs
         • Helps bind together smooth muscle cells
         • Filters worn-out blood cells and bacteria
     • Dense Connective Tissue
       • Regular
         • Bundles of regularly arranged parallel collagen fibers
         • Tough, but pliable tissue
         • Makes up tendons and most ligaments
       • Irregular
         • Bundles of irregularly arranged collagen fibers
         • Found where pulling forces are exerted in various directions
         • Found in the dermis of the skin, heart valves, perichondrium, and periosteum
       • Elastic
         • Consists of branching elastic fibers
         • Makes up lung tissue and elastic arteries
     • Cartilage
       • General Facts
         • Collagen and elastic fibers embedded in chondroitin sulfate ground substance
         • Surface is surrounded by perichondrium
         • Has no blood vessels or nerves, except for in the perichondrium.
         • Cells: Chondrocytes
       • Fibrocartilage
         • Fibers visible
         • Strongest Type
         • Example: Vertebral discs, knee cartilages
       • Elastic
         • Chondrocytes in threadlike elastic network
         • Example: ear cartilage
       • Hyaline
         • Appears clear because fibers are not easily visible
         • Example: at ends of long bones, fetal skeleton
     • Bone: Osseous Tissue
       • Supports, protects, and allows movement
       • Cells called osteoblasts, osteoclasts, osteocytes
       • Site of blood formation (red marrow) and storage of minerals (Ca, P)
       • Houses yellow bone marrow, which stores triglycerides
     • Liquid Connective Tissue
       • Blood
         • Matrix is plasma
         • Cells: red blood cells, white blood cells, platelets
       • Lymph
         • Matrix is lypmh: similar to plasma but with much less protein
         • some white blood cells

3. Muscle Tissue

   • Functions
     • produces movement
     • release heat
     • maintains posture
     • supports soft tissues
     • Moves substances
   • Cells
     • Elongated, contractile
   • Types
     • Skeletal Muscle
       • pulls on bones allowing body movements; voluntary and striated
     • Cardiac Muscle
       • forms wall of heart; pumps blood through blood vessels; involuntary and striated
     • Smooth Muscle
       • found in walls of hollow organs such as stomach and bladder; involuntary

4. Nervous Tissue

   • conduct nerve impulses
   • Types of Cells
     • Nuerons: convert stimuli into nerve impulses and conduct them
     • Neuroglia: do not generate nerve impulses, but serve support functions

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