Epithelial Tissues

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EpithelialTissues
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Epithelial Tissue

• Epithelial tissue forms layers of cells that
• line body cavities
• create coverings over external internal body
  surfaces.
• are found widespread throughout the body.
• Generally lack blood vessels
• replaced frequently
• The cells come in a variety of shapes and
  arrangement determined by their function.
  (secretion, absorption, excretion, sensory)

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Types of Cells

• SIMPLE SQUAMOUS.
• Flat cells
• Functions in the exchange of gases in the lungs
  and lines blood and lymph vessels as well as body
  cavities.
• Thin, one layer, covering of epithelium

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Types of Cells

• STRATIFIED SQUAMOUS.
• Made up of layers of flattened cells that are
  designed to protect underlying layers
• Makes up the outer layer of skin, and lines the
  mouth , throat, vagina and anal canal

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Types of Cells.

• SIMPLE CUBOIDAL.
• cube shaped with centrally located nucleus
• Functions in secretion absorption in the
  kidneys and some glands
• Usually associated with structures that produce
  secretions
• Simple

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Types of Cells.

• STRATIFIED CUBOIDAL.
• Consists of 2-3 layers of cells lining the lumen
  of the mammary glands, sweat glands, salivary
  glands, and pancreas
• Several layers provide more protection than one

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Types of Cells..

• SIMPLE COLUMNAR
• tall column-shaped cells, nuclei are located near
  the basement membrane
• Lines the uterus, stomach, intestines where it
  protect underlying tissues, and secretes
  digestive juices absorbs nutrients
• Mucus secreting goblet cells can be found among
  columnar cells
• Simple, Stratified, Pseudostratified, Ciliated

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Types of Cells..

• STRATIFIED COLUMNAR
• Consists of several layers of cells and is found
  in the vas deferens, part of the male urethra and
  parts of the pharynx

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Types of Cells..

• PSEUDOSTRATIFIED COLUMNAR
• Appear layered due to the varying postions of
  their nuclei, but are not truly layered
• Cilia may be present, along with mucus-secreting
  goblet cells, that line and sweep debris from the
  respiratory tubes
• In the female reproductive tract, cilia on these
  cells aid in moving eggs through the oviducts to
  the uterus

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Types of Cells..

• TRANSITIONAL..
• Occurs in areas where cells change shape from
  columnar to squamous for stretch and expansion.
• Found in the lining of the urinary bladder

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Types of Cells

• Glandular Epithelium
• Designed to produce and secrete substances into
  ducts or into body fluids
• Merocrine glands..release fluid products by
  exocytosis (pancreas) and are grouped as serous
  or mucus producing
• Apocrine glands lose portions of their cell
  bodies during secretion (mammary glands)
• Holocrine glands release entire cells (sebaceous
  glands)

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Terminology.

• Simple
• Single layer of cells
• Stratified
• Multi-layered arrangements found in ares where
  the cells are likely to be subjected to wear and
  tear.
• ie. Skin
• Pseudostratified
• Actually has only a single layer of cells, but
  looks like it is stratified.
• Found in the tubes leading to the lungs (trachea
  and bronchial tubes)
• Ciliated
• Some columnar or pseudostratified cells may be
  ciliated (hair-like projections)