Oral Histology andEmbryology: Tissues

Tissues: a group of cells with similar characteristics of form and function
1. Tissue Properties
  1. Regeneration: The natural renewal of tissue by the growth of new tissue to replace the old
    1. Tooth enamel doesn't regenerate
  2. Turn over time: the time it takes for new cells to differentiate and replace old tissue
    1. Varies between tissue types
2. Basic Tissue Types
  1. Epithelial: Tissue type covering and lining all internal and external body surfaces
    1. Histology of epithelial tissue:
      1. Can be derived from any of the three embryonic layers: 1) ectoderm- epidermis and oral regions 2) mesoderm- 3) endoderm
      2. Capable of rapid regeneration because there is only one cell type
      3. Avascular (Receives blood supply from the CT below
      4. ALWAYS has a basement membrane between any epithelium and it's underlying CT
    2. Function
      1. Serves as a protective covering but is also involved itissue absorption, secretioin, sensory, and specialized functions
    3. Classification:
      1. Arrangement
        Simple: One layer of cells
        Stratified: More than one layer of cells
        Pseudostratified: One layer of cells that all attach to the basement membrane, and appears to be multiple layers. This is due to the nuclei being at different levels.
      2. Shape
        Squamous: Platelike and flattened. Height is less than width
        Cuboidal: Cube shaped. Equal height and width
        Columnar: Rectangles with height greater than their width
      3. Most of the epithelial tissues in the body are stratified squamous
  2. Muscle
    1. Types of muscle tissue
      1. Skeletal muscle
        Voluntary, and typically attach to bone. Ex. muscles in the pharynx, tongue, esophagus, and for facial expression and mastication
        Histology: Striped or striated. Muscle --> Muscle bundle (fascicle) --> muscle cells (myofibers) --> myofibrils --> myofilaments (actin and myosin)
      2. Smooth muscle
        Involuntary, and under the control of the ANS. Contractions are slow and can be maintained over time
      3. Cardiac muscle
        Has characteristics of smooth muscle and striated muscle. Only muscle tissue that has Purkinje fibers or a Bundle of His
    2. Function: Movement, support, etc.
  3. Nerve Tissue
    1. Function: Carry impulses based on electric potentials. Results in movement of muscles, stimulation of glands, regulations of systems, perceptions of sensations like pain, touch, taste, and smell
    2. Histology of nerve tissue (derived from neuroectoderm)
      1. Neuron: the functional cellular component of the nervous system
        Neuron Components
        Cell body
        Cytoplasmic components:
        Axon: A long, thin, singular cablelike process that conducts impulses away from the neuron
        Dendrite: a threadllke process, usually with multiple branches that receives impulses travelling to the neuron
      2. Nerve: A bundle of neural processes in the PNS (not in CNS)
        Afferent Nerves: Sensory. BODY TO BRAIN
        Efferent Nerves: Motor. BRAIN TO BODY
    3. Divisions of nervous system
      1. Central nervous system: CNS: Brain and spine
      2. Peripheral Nervous System: Spinal and cranial nerves
        Autonomic Nervous system: Operates without conscious control and is responsible for the sympathetic (fight or flight) response and the parasympathetic (rest and digest) response.
        Somatic Nervous System: Voluntary skeletal movement
  4. Connective Tissue
    1. Function: support, attachment, packing, insulation,storage, transport, repair and defense
    2. Properties: By weight the most abundant type of basic tissue --> Lots of matrix (which is intercellular substance and fibers
    3. Fibroblast: Most common cell in CT- long flat and elongated- Fixed- Differentiate into all CT cell types
      1. Protein FIbers
        Elastic Fibers: Have the ability to stretch and return to their original shape. Composed microfilaments embedded in elastin
        Reticular Fibers: Prominent in embryonic tissues, and only in the spleen and lymph nodes in adults. Very fine hairlike fibers composed of reticulin
        Collagen Fibers: Main fibers in CT- about twelve common types- types 1-4 most
    4. CT Classification:
      1. Soft
        CT Proper
        Loose CT
        Dense CT
        Specialized
        Adipose Tissue
        Elastic Tissue
        Reticular Tissue
      2. Firm: Cartilage-
        Function: Forms temporary skeleton of embryo, and is present in articulate surfaces of movable joints
        Cell Types:
        Chondroblasts- Lie internal to the perichondrium and PRODUCE the cartilage matrix
        Appositional Growth- chondroblasts on external surface replace damaged tissue by building layers upon preexisting cartilage
        Chondrocytes- Mature chondroblasts these MAINTAIN the cartilage matrix
        Interstitial Growth- chondrocytes undergo mitosis inside of the lacuna and expand from the inside out
        Types of Cartilage:
        Elastic cartilage: Has numerous elastic fibers in addition to collagen fibers
        Fibrocartilage: Never found alone. Transitional type between hyaline cartilage and dense CT. No true perichondrium.
        Hyaline cartilage: Most common type of cartilage, all cartilage starts out as this. Only collagen fibers
        Repair- As cartilage ages it becomes less cellular and the chondrocytes die. Fibers become firm and repair is slow because it is avascular
        Avascular and no nerve supply. Surrounded by the perichondrium which is a fibrous CT sheath containing blood vessels
      3. Rigid: Bone-
        Functions: Protection and structural support for soft tissues, attachment mechanism, movement, manufactures blood cells through bone marrow, stores calcium and other minerals
        Anatomy (superficial-deep)
        Periosteum: Double layered dense CT sheath covering bone. The outer layer contains blood vessels and nerves and the inner layer has cells that form osteoblasts.
        Compact bone:
        Cancellous bone
        Endosteum- similar to the periosteum however it lines the inside of the bone
        Bone marrow: location of blood stem cells
        Development
        Intramembranous Ossification
        Endochondral ossification
        Repair
      4. Fluid
        Function
        Components
        Plasma
        Formed Elements
        Thrombocytes
        Erythrocytes
        Leukocytes
        Granulocytes
        Eosinophils
        Basophils
        Neutrophill
        Agranulocytes
        Lymphocytes
        B Cells
        T cells
        Natural killer cells
        Monocytes

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Oral Histology andEmbryology: Tissues

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	Creado por Rachel Hibray hace alrededor de 7 años