Histology: Study of Tissues

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Chapter 4

• Histology Study of Tissues

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TISSUE TYPES

• Epithelial
• Connective
• Muscle
• Nervous

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Embryonic Development

• Blastocyst- ball of cells
• Germ layers
• Endoderm- outer layer
• Mesoderm- middle layer
• Ectoderm- inner layer
• Gastrulation- process of blastocyst to germ
  layers
• Histogenesis- process of germ layers developing
  into different kinds of tissues.

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Epithelial Tissue

• Types locations
• membranous cover/lining found in serous
  cavities, bld lymph vessels, respiratory,
  digestive genitourinary tracts.
• Glandular grouped in solid cords or specialized
  follicles that form secretory units of endocrine
  exocrine glands.

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Epithelial Tissue

• Functions
• Protection
• Sensory functions
• Secretion
• Absorption
• Excretion

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Epithelial Tissue

• Generalizations
• Limited matrix material
• Connects to connective tissue
• Avascular
• Cells tightly packed
• Frequently replace themselves

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Epithelial Tissue

• Classifications
• Membranous epithelium
• Classification based on cells shape
• Squamous cells
• Cubiodal cells
• Columnar cells
• Pseudostratified columnar cells

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Epithelial Tissue

• Classifications
• Classification based on layers of cells
• Simple epithelium
• Stratified epithelium
• Transitional epithelium

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Epithelial Tissue

• Glandular epithelium
• Unicellular glands- single-celled glands Goblet
  Cells
• Multicellular glands- clusters, solid cords,
  specialized follicles
• Exocrine glands- secrete into ducts
• Endocrine glands- ductless glands

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Connective Tissue Categories

• Embryonic or mesenchyme
• Adult
• Loose
• Dense
• Connective tissue with special properties
• Cartilage
• Bone
• Blood

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Extracellular Matrix

• Components
• Protein fibers
• Collagen which is most common protein in body
• Reticular fill spaces between tissues and organs
• Elastic returns to its original shape after
  distension or compression
• Ground substance
• Shapeless background
• Fluid

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Loose Connective Tissue

• Also known as areolar tissue
• Loose packing material of most organs and tissues
• Attaches skin to underlying tissues
• Contains collagen, reticular, elastic fibers and
  variety of cells

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Dense Connective Tissue

• Dense regular
• Has abundant collagen fibers
• Tendons Connect muscles to bones
• Ligaments Connect bones to bones
• Dense regular elastic
• Ligaments in vocal folds
• Dense irregular
• Scars
• Dense irregular collagenous
• Forms most of skin dermis
• Dense irregular elastic
• In walls of elastic arteries

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Connective Tissue with Special Properties

• Adipose tissue- Fat storage
• Consists of adipocytes
• Types
• Yellow (white)
• most abundant, white at birth and yellows with
  age
• Brown
• found only in specific areas of body as axillae,
  neck and near kidneys
• Reticular tissue
• Forms framework of lymphatic tissue
• Characterized by network of fibers and cells

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Cartilage

• Composed of chondrocytes
• located in spaces called
• lacunae
• Next to bone firmest
• structure in body
• Types of cartilage
• Hyaline
• Fibrocartilage
• Elastic

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Hyaline Cartilage

• Found in areas for strong support and some
  flexibility
• Rib cage and cartilage in trachea and bronchi
• Forms most of skeleton before replaced by bone in
  embryo
• Involved in growth that increases bone length

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Fibrocartilage

• Slightly compressible and very tough
• Found in areas of body where a great deal of
  pressure is applied to joints
• Knee, jaw, between vertebrae

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Elastic Cartilage

• Rigid but elastic properties
• External ears, epiglottis

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Osseous Tissue

• Commonly called bone tissue
• Function is to support protect
• Made of osteocytes
• Compact Bone
• Cancellous or Spongy Bone

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Blood

• Matrix between the cells is liquid
• Hemopoietic tissue
• Forms blood cells
• Found in bone marrow
• Yellow
• Red

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Muscle Tissue

• Characteristics
• Contracts or shortens with force
• Moves entire body and pumps blood
• Types
• Skeletal- moves bones
• Striated and voluntary
• Cardiac- pumps heart
• Striated and involuntary
• Smooth- covers organs moves fluids
• Nonstriated and involuntary

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Nervous Tissue

• Found in brain, spinal cord and nerves
• Ability to produce action potentials
• Cells
• Nerve cells or neurons
• Consist of dendrites, cell body, axons
• Consist of multipolar, bipolar, unipolar
• Neuroglia or support cells

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Membranes

• Mucous
• Line cavities that open to the outside of body
• Secrete mucus
• Serous
• Line cavities not open to exterior
• Pericardial, pleural, peritoneal
• Synovial
• Line freely movable joints
• Produce fluid rich in hyaluronic acid

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Inflammation

• Response when tissues damaged or with an immune
  response
• Manifestations
• Redness, heat, swelling, pain, disturbance of
  function
• Mediators
• Include histamine, kinins, prostaglandins,
  leukotrienes
• Stimulate pain receptor and increase blood vessel
  permeability