Tissues

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Tissues
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• Definition- group of similar cells that together
  perform a specialized function
• Histology- study of tissues
• Basic types
• Epithelial- covers body surfaces, lines cavities,
  organs, ducts, and forms glands
• Connective- protection, supports body, binds
  organs together, stores energy as fat, produces
  immunity
• Muscle- movement
• Nervous- initiates and transmits impulses that
  coordinate body activity

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Epithelial tissue

• Consist of closely packed cells, little
  intercellular fluid
• Single or multiple layers
• Avascular- no blood vessels
• Have nerve supply
• High turn over rate- constantly making more
• Functions
• Protection, filtration, lubrication, secretion,
  digestion, absorption, transportation, excretion,
  sensory receptors, reproduction

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• Simple- single layer found where transport is
  needed
• Stratified- 2 layers used for protection
• Psuedostratified- one layer but looks like more

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• Squamous- flat and attached together like tiles
• Cubiodal- cube or hexagonal shape
• Produce secretions (sweat, enzymes)
• Can absorb- intestinal tract

Simple Squamous
Simple cuboidal
Stratified cuboidal
Stratified squamous
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• Columnar- tall and cylindrical
• Protection of underlying tissue
• Specialized for secretion and absorption
• Transitional
• Vary in shape
• Flat to columnar due to stretching

Stratified columnar
Simple columnar
Transitional
Pseudostratified columnar
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Glandular Epithelium

• Functions for secretions- cells lie below outer
  epithelium
• Endocrine- ductless- hormones
• Exocrine- secreted into ducts- mucous, sweat,
  oil, digestive enzymes

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Connective Tissue

• Most abundant tissue in the body
• All connective tissue comes from embryonic
  mesenchyme
• Stem cells

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Connective Tissue Proper

• Intercellular material and matrix
• Hyaluronic acid
• Viscous, slippery substance that binds cells
• Chondroitin sulfate
• Provides support and adhesiveness in cartilage,
  bone, skin, and blood vessels

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Loose (areolar) tissue

• Most widely distributed
• Location- widespread- mucous membranes, around
  blood vessels and nerves, subcutaneous
• Fibrous
• Collagenous (white)
• Tough, resistant to pulling
• Made of collagen
• Elastic (yellow)
• Smaller, provides strength, skin, blood vessels,
  and lungs
• Reticular
• Thin, immature collagen
• Collagen coated with glyco-protein
• Supports walls of blood vessels, nerve cells, and
  smooth cells
• Forms stroma- framework of spleen and lymph nodes

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Cells

• Fibroblasts- most numerous, especially active in
  repair
• Macrophages- large and function to engulf
  bacteria and cellular debris by phagocytosis
• Plasma cells- secrete antibodies- immunity
• Melanocytes- pigmented cells below deepest layer
  of skin- produce melanin
• Mast cells- produce heparin (anti-coagulant) and
  histamine- a chemical that dilates small blood
  vessels during inflammation

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Adipose tissue

• Cells called adipocytes- fat storage
• Shape
• Signet ring shaped
• Location
• Subcutaneous
• Functions
• Good insulation, energy reserve, protection of
  internal organs

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• Dense collagenous tissue
• More numerous cells and thicker fibers
• Location muscles, ligaments, tendons
• Functions provide elasticity
• Elastic tissue
• Structure freely branched fibers- stretch and
  snap back
• Location muscles, ligaments, tendons
• Function allow for elasticity

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• Cartilage- no blood vessels or nerves (except in
  the perichondrium- tissue around carilage)
• Characteristics
• Dense network of collagen and chondroitin sulfate
• Resistant
• strong
• Types
• Hyaline- gristle- bluish white color, shiny, most
  abundant
• Found in embryonic skeleton (exclusively)
• Found on end of long bones and costal
• Fibrocartilage
• Found in matrix to give strength
• Bundles of collagen fibers
• Elastic
• Threadlike network for elasticity

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Hyaline cartilage
Elastic Cartilage
Cartilage from the external ear
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Osseous tissue (bone)

• Skeletal system- basic unit called an osteon-
  made of
• Lamellae
• Concentric rings of hard matrix- calcium
• Lacunae
• Spaces between lamellae- has Haversian canal-
  contains blood vessels and nerves

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Vascular tissue (blood)

• Connective tissue
• Plasma- mostly water with dissolved substances
  (nutrients, wastes, enzymes, hormones,
  respiratory gasses)
• Erythrocytes- red blood cells
• Leucocytes (WBC)- phagocytes, immunity
• Platelets- clotting

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Other tissues

• Muscle tissue- highly specialized cells for
  contraction
• Smooth- walls of internal organs (hollow)-
  involuntary- non striated
• Cardiac- wall of heart- involuntary- striated- 1
  nucleus
• Skeletal- striated- voluntary- fibers are
  cylindrical and striated- multiple nuclei

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Smooth muscle
Cardiac muscle
Skeletal muscle
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• Nerve tissue
• Consists of neurons
• Neurons
• Calls that receive stimuli and convert to
  impulse- carry impulses to other nerves, muscles,
  or glands
• Dendrites- converging branches that take impulse
  to cell body
• Axons- long, single strand that conduct impulses
  AWAY from cell body
• Neuroglea
• Cells for protection and support of neurons
• DO NOT CONDUCT
• Common sites of tumors

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• Membranes
• Mucous- line cavities that open to the outside
  world
• Serous- line cavities that do not open to
  outside, cover organs, produce serous fluid
• Synovial- line freely moving joints, not open to
  outside