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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. Epithelial tissue. Includes glands and epithelium

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Tissues and tissue types

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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


Epithelial tissue

  • Includes glands and epithelium

    • Glands are secretory

  • Is avascular

  • Forms a protective barrier that regulates permeability

  • Cells may show polarity


Functions of epithelium

  • Physical protection

  • Control permeability

  • Provide sensation

  • Produce specialized secretions


Specializations of epithelium

  • Perform secretory functions

  • Perform transport functions

  • Maintain physical integrity

  • Ciliated epithelia move materials across their surface


The Polarity of Epithelial Cells


Maintaining the integrity of epithelium

  • Cells attach via cell adhesion molecules (CAM)

  • Cells attach at specialized cell junctions

    • Tight junctions

    • Desmosomes

    • Gap junctions


Intercellular connections


Structure of typical epithelium

  • Basal lamina attaches to underlying surface

    • Lamina lucida

    • Lamina densa

  • Germinative cells replace short-lived epithelial cells


Classification of epithelia

  • Number of cell layers

    • Simple

    • Stratified

  • Shape of apical surface cells

    • Squamous

    • Cuboidal

    • Columnar


Squamous Epithelia


Cuboidal Epithelia


Cuboidal Epithelia


Transitional Epithelium


Columnar Epithelia


Columnar Epithelia


Columnar Epithelia


Glandular epithelia

  • Exocrine glands

    • Secrete through ducts onto the surface of the gland

  • Endocrine glands

    • Release hormones into surrounding fluid


Glandular secretions can be:

  • Merocrine (product released through exocytosis)

  • Apocrine (involves the loss of both product and cytoplasm)

  • Holocrine (destroys the cell)


Mechanisms of Glandular Secretion


Glands

  • Unicellular

    • Individual secretory cells

  • Multicellular

    • Organs containing glandular epithelium

    • Classified according to structure


A Structural Classification of Exocrine Glands


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


A Classification of Connective Tissues


Connective tissues contain

  • Specialized cells

  • Matrix

    • Composed of extracellular protein fibers and a ground substance


Connective tissue proper

  • Contains varied cell populations

  • Contains various fiber types

  • A syrupy ground substance


Fluid connective tissue

  • Contains a distinctive cell population

  • Watery ground substance with dissolved proteins

  • Two types

    • Blood

    • Lymph


Supporting connective tissues

  • Less diverse cell population

  • Dense ground substance

  • Closely packed fibers

  • Two types

    • Cartilage

    • Bone


Connective tissue proper

  • Contains fibers, a viscous ground substance, and a varied cell population

    • Fibroblasts

    • Macrophage

    • Adipocytes

    • Mesenchymal cells

    • Melanocytes

    • Mast cells

    • Lymphocytes

    • Microphages


Connective tissue proper

  • Three types of fiber

    • Collagen fibers

    • Reticular fibers

    • Elastic fibers


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


The Cells and Fibers of Connective Tissue Proper


Connective Tissue in Embryos


Adipose and Reticular Tissues


Dense Connective Tissues


Dense Connective Tissues


Dense Connective Tissues


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


Formed Elements of the Blood


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


The Perichondrium and Types of Cartilage


The Perichondrium and Types of Cartilage


The Perichondrium and Types of Cartilage


Bone, or osseus tissue

  • Has osteocytes

    • Depend on diffusion through canaliculi for nutrients

  • Little ground substance

  • Dense mineralized matrix

  • Surrounded by periosteum


Bone


Membranes are simple organs

  • Form a barrier

  • Composed of epithelium and connective tissue

  • Four types

    • Cutaneous

    • Synovial

    • Serous

    • Mucous


Membranes


Mucous membranes

  • Line cavities that communicate with the exterior

  • Contain lamina propria


Serous membranes

  • Line sealed internal cavities

  • Form transudate


  • Cutaneous membrane

    • Covers the body surface

  • Synovial membrane

    • Incomplete lining within joint cavities


Organs and systems are interconnected

  • Network of connective tissue proper consisting of

    • Superficial fascia

    • Deep fascia

    • Subserous fascia


The Fasciae


Muscle tissue

  • Specialized for contraction

  • Three types

    • Skeletal

    • Cardiac

    • Smooth


Muscle Tissue


Muscle Tissue


Muscle Tissue


Skeletal muscle

  • Cells are multinucleate

  • Striated voluntary muscle

  • Divides via satellite cells


Cardiac muscle

  • Cardiocytes occur only in the heart

  • Striated involuntary muscle

  • Relies on pacemaker cells for regular contraction


Smooth muscle tissue

  • Non-striated involuntary muscle

  • Can divide and regenerate


Neural tissue

  • Conducts electrical impulses

  • Conveys information from one area to another


Neural tissue cells

  • Neurons

    • Transmit information

  • Neuroglia

    • Support neural tissue

    • Help supply nutrients to neurons


Neural Tissue


Neural anatomy

  • Cell body

  • Dendrites

  • Axon (nerve fiber)

    • Carries information to other neurons


Inflammation and regeneration

  • Injured tissues respond in coordinated fashion

  • Homeostasis restored by inflammation and regeneration


Inflammatory response

  • Isolates injured area

  • Damaged cells, tissue components and dangerous microorganisms removed

    • Infection avoided

  • Regeneration restores normal function


An Introduction to Inflammation


Aging and tissue repair

  • Change with age

  • Repair and maintenance less efficient

  • Structure altered

  • Chemical composition altered


Aging and cancer incidence

  • Incidence of cancer increases with age

  • 70-80% of all cases due to exposure to chemicals or environmental factors


Changes in a Tissue under Stress


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