Tissues are:

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Tissues and tissue types

• Tissues are
• Collections of specialized cells and cell
  products organized to perform a limited number of
  functions
• Histology study of tissues
• The four tissue types are
• Epithelial
• Connective
• Muscular
• Nervous

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Epithelial tissue

• Includes glands and epithelium
• Glands are secretory
• Is avascular
• Forms a protective barrier that regulates
  permeability
• Cells may show polarity

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Functions of epithelium

• Physical protection
• Control permeability
• Provide sensation
• Produce specialized secretions

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Specializations of epithelium

• Perform secretory functions
• Perform transport functions
• Maintain physical integrity
• Ciliated epithelia move materials across their
  surface

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The Polarity of Epithelial Cells
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Maintaining the integrity of epithelium

• Cells attach via cell adhesion molecules (CAM)
• Cells attach at specialized cell junctions
• Tight junctions
• Desmosomes
• Gap junctions

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Intercellular connections
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Structure of typical epithelium

• Basal lamina attaches to underlying surface
• Lamina lucida
• Lamina densa
• Germinative cells replace short-lived epithelial
  cells

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Classification of epithelia

• Number of cell layers
• Simple
• Stratified
• Shape of apical surface cells
• Squamous
• Cuboidal
• Columnar

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Squamous Epithelia
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Cuboidal Epithelia
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Cuboidal Epithelia
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Columnar Epithelia
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Columnar Epithelia
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Columnar Epithelia
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Transitional Epithelium
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Glandular epithelia

• Exocrine glands
• Secrete through ducts onto the surface of the
  gland
• Endocrine glands
• Release hormones into surrounding fluid

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Glandular secretions can be

• Merocrine (product released through exocytosis)
• Apocrine (involves the loss of both product and
  cytoplasm)
• Holocrine (destroys the cell)

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Mechanisms of Glandular Secretion
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Glands

• Unicellular
• Individual secretory cells
• Multicellular
• Organs containing glandular epithelium
• Classified according to structure

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A Structural Classification of Exocrine Glands
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Connective tissue functions

• Establishing a structural framework
• Transporting fluids and dissolved materials
• Protecting delicate organs
• Supporting, surrounding and interconnecting
  tissues
• Storing energy reserves
• Defending the body from microorganisms

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A Classification of Connective Tissues
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Connective tissues contain

• Specialized cells
• Matrix
• Composed of extracellular protein fibers and a
  ground substance

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Connective tissue proper

• Contains varied cell populations
• Contains various fiber types
• A syrupy ground substance

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Fluid connective tissue

• Contains a distinctive cell population
• Watery ground substance with dissolved proteins
• Two types
• Blood
• Lymph

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Supporting connective tissues

• Less diverse cell population
• Dense ground substance
• Closely packed fibers
• Two types
• Cartilage
• Bone

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Connective tissue proper

• Contains fibers, a viscous ground substance, and
  a varied cell population.
• The ground substance is the non-living material
  in which the cells and protein fibres are found.
• Can contain varying amounts of water.
• Can be of viscous (blood), semi-solid (cartilage)
  or solid (bone).
• The ground substance and the extracellular
  proteins form the matrix.

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• Types of cells found in connective tissue
• Macrophage
• Adipocytes
• Mesenchymal cells
• Fibroblasts
• Melanocytes
• Mast cells
• Lymphocytes
• Microphages

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Connective tissue proper

• Three types of fiber
• Collagen fibers
• Reticular fibers
• Elastic fibers

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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

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The Cells and Fibers of Connective Tissue Proper
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Connective Tissue in Embryos
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Adipose and Reticular Tissues
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Dense Connective Tissues
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Dense Connective Tissues
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Dense Connective Tissues
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Fluid connective tissues

• Distinctive collections of cells in a fluid
  matrix
• Blood
• Formed elements and plasma
• Red blood cells, white blood cells and platelets
• Arteries carry blood away, veins carry to the
  heart
• Capillaries allow diffusion into the interstitial
  fluid
• Lymph
• Interstitial fluid entering the lymphatic vessels

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Formed Elements of the Blood
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Supporting connective tissues

• Cartilage and bone support the rest of the body
• Cartilage
• Grows via interstitial and appositional growth
• Matrix is a firm gel containing chondroitin
  sulfate
• Cells called chondrocytes
• Cells found in lacunae
• Perichondrium separates cartilage from
  surrounding tissues
• Three types hyaline, elastic and fibrocartilage

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The Perichondrium and Types of Cartilage
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The Perichondrium and Types of Cartilage II
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The Perichondrium and Types of Cartilage III
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Bone, or osseus tissue

• Has osteocytes
• Depend on diffusion through canaliculi for
  nutrients
• Little ground substance
• Dense mineralized matrix
• Surrounded by periosteum

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Bone
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Membranes are simple organs

• Form a barrier
• Composed of epithelium and connective tissue
• Four types
• Cutaneous
• Synovial
• Serous
• Mucous

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Membranes
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Mucous membranes

• Line cavities that communicate with the exterior
• Contain lamina propria

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Serous membranes

• Line sealed internal cavities
• Form transudate

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• Cutaneous membrane
• Covers the body surface
• Synovial membrane
• Incomplete lining within joint cavities

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Organs and systems are interconnected

• Network of connective tissue proper consisting of
• Superficial fascia
• Deep fascia
• Subserous fascia

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The Fasciae
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Muscle tissue

• Specialized for contraction
• Three types
• Skeletal
• Cardiac
• Smooth

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Muscle Tissue
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Muscle Tissue
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Muscle Tissue
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Skeletal muscle

• Cells are multinucleate
• Striated voluntary muscle
• Divides via satellite cells

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Cardiac muscle

• Cardiocytes occur only in the heart
• Striated involuntary muscle
• Relies on pacemaker cells for regular contraction

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Smooth muscle tissue

• Non-striated involuntary muscle
• Can divide and regenerate

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Neural tissue

• Conducts electrical impulses
• Conveys information from one area to another

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Neural tissue cells

• Neurons
• Transmit information
• Neuroglia
• Support neural tissue
• Help supply nutrients to neurons

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Neural Tissue
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Neural anatomy

• Cell body
• Dendrites
• Axon (nerve fiber)
• Carries information to other neurons

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Inflammation and regeneration

• Injured tissues respond in coordinated fashion
• Homeostasis restored by inflammation and
  regeneration

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Inflammatory response

• Isolates injured area
• Damaged cells, tissue components and dangerous
  microorganisms removed
• Infection avoided
• Regeneration restores normal function

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An Introduction to Inflammation
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Aging and tissue repair

• Change with age
• Repair and maintenance less efficient
• Structure altered
• Chemical composition altered

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Aging and cancer incidence

• Incidence of cancer increases with age
• 70-80 of all cases due to exposure to chemicals
  or environmental factors

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Changes in a Tissue under Stress