epithelial tissue

• All tissues can be placed into one of four categories

  –Epithelial Tissue

  –Connective Tissue  

  –Muscle Tissue

  –Nervous Tissue
• Epithelial Tissue Has:

  1. Epithelia: external coverings and internal linings
  2. Granular
• Origin of epithelial tissue

  From all embryonic layers

  -ectoderm

  -mesoderm

  -endoderm
• ectoderm

  • epidermis of skin
  • oral and nasal mucosae
  • cornea
  • glands of skin
• Mesoderm

  • Lining of abdominal cavities
• Endoderm

  • lining of major organs
  • large glands- liver and pancreas
• Functions of epithelial tissue

  • protection
  • trancellular transplant
  • secretion
  • absorption
  • control material movement
  • detection of sensation
• Epithelium

  • tightly bound continuous sheets
  • little intracellular space
• epithelium is separated from underlying tissue by: basal lamina
• ectracellular matrix is secreted by: epithelial cells
• One side of epithelium is not attached to other tissues
• epithelium is always avascular
• simple squamous epithelium

  • allows for transfer of materials through: pulmonary alveoli and loop of henle
  • lines blood vessels
• simple cuboidal epithelium function

  • limited protection
  • secretion and absorption
• simple cuboidal epithelium location

  • glands
  • ducts going to gland
  • part of kidney
  • part of thyroid
• simple columnar

  • lines most digestive organs
  • secretes mucous
  • absorbs nutrients
  • sometimes ciliated
• stratifies squamous

  • protection
  • lines many organs
• stratified squamous

  • most common stratified tissue
  • basal cells may appear cuboidal or columnar
  • outer cells may be keratinized
• stratified cuboidal

  • lines ducts of sweat glands
  • secretes water and ions
• stratified columnar

  • protection
  • small regions of lumen linings
• transitional epithelium

  • protection with extension
  • lining of urinary system
• pseudostratified epithelium

  • appears stratified
  • all cells have basal lamina
  • usually ciliated
  • often with goblet cells
  • some excretory ducts
  • some glands
• apical domain

  • one edge of tissue opens to lumen or outside
• basolateral domain

  • one side is attached to basal lamina
• apical domain characters

  • rich in ion channels and carrier proteins
• apical domain characters

  • Microvilli- cytoplasmic projections, contains cross-linked actin fibers
• apical domain characters

  • stereo cilia: long microvilli, not cilia
• apical domain characters

  • cilia: motile hair like projections, propel material past cells, ordered microtubules
• Cilia: moves materials past tissues. Mucous catches bad stuff and cilia moves it.
• Lateral membrane specializations: put together by tight junctions
• tight junctions: keeps cells from getting too big or too full, holds them together
• desmosomes

  • attachment plaques with filaments
  • work like a welded area
• plasma membrane infoldings

  • finger like structure
  • increase surface area
  • found in areas of absorption
  • many mitochondria provide energy for absorption processes
• hemidesomosomes

  • anchor membrane to basal lamellae
  • resemble half desmosomes
• basal lamina

  • separates epithelium from connective tissue
  • secreted by cells
  • extracellular matrice
  • acellular
• epithelial regeneration

  • replacement is rapid
  • basal cells are mitotic
• glands originate from: epithelial cells
• two major group of glands

  • exocrine (outside of body)
  • endocrine (inside of body)
• exocrine glands

  • secretions released onto epithelial surfaces
  • uses ducts to deliver secretions
• examples of exocrine glands

  • mucous
  • sweat
  • oil
  • salivary