epithelial tissue

• EPITHELIAL TISSUE

  • Aggregated polyhedral cells
  • Small amount
  • Lining of surface or body cavities; glandular secretion
• Connective Tissue


  several types of fixed & wandering cells

  abundant amount

  support & protection of tissues / organs
• muscle tissue


  elongated contractile cells

  moderate amount

  strong contraction; body movements
• NERVOUS TISSUE

  Elongated cells with extremely fine processes

  Very small amount

  Transmission of nerve umpulses
• EPITHELIAL TISSUE

  • Tissue in which polyhedral cells are bound tightly together structurally and functionally to form a sheetlike or tubular structure.
  • It is made up of thin extracellular matrix/material.
  • It lines all external and internal surfaces of our body and all substances that leave and enter an organ must cross the epithelial tissue.
• Epithelial cells show polarity.
• • All epithelial tissues lie in the basement membrane.
  • All epithelial tissues are avascular (lacks blood vessels)
• Basal pole - faces the connective tissue.
• Apical pole - faces the space or lumen.
• BASEMENT MEMBRANE

  Acts as filters and it provides structural support to epithelial cells.

  Attaches the epithelia to underlying connective tissue.

  Thin extracellular layer of specialized proteins.
• Basal Lamina

  • Thin meshwork of type 4 collagen and laminin produced by the epithelial cells.
• reticular lamina

  • contains type 3 collagen & anchoring fibrils of 7 collagen
• TYPES OF JUNCTIONAL COMPLEXES

  • an intercellular attachment structure.
  • It is usually found around the apical membrane of an epithelial or endothelial cell
• OCCLUDING OR TIGHT JUNCTIONS

  • Also known as ZONULA OCCLUDENS.
  • Seals adjacent cells to one another, controlling passage of molecules between them.
  • Separates apical and basolateral membrane domains.
  • Major transmembrane link proteins:
  • Occludins
  • Claudins
  • ZO proteins
• ADHARENT JUNCTIONS

  Also known as ZONULA ADHERENS.

  • Provides points linking the cytoskeletons of adjacent cells.

  • Strengthens and stabilizes tight junction.
  • Site of strong adhesion.
  • Major transmembrane link proteins: E-cadherin, Catenin complexes
• DESMOSOME OR MACULA JUNCTIONS

  • Provides points of strong intermediate filament coupling between adjacent cells.
  • Strengthening the tissue.
  • Major transmembrane link proteins: Cadherin family proteins (desmoglein & desmocollin)
• Hemidesmosomes

  • Anchors cytoskeleton to the basal lamina.
  • Major transmembrane link proteins: Integrins
• What do gap or communicating junctions allow between cells?

  Direct transfer of small molecules and ions
• How do gap junctions primarily function?

  They facilitate intracellular interaction and communication
• What is each intracellular channel in a gap junction made of?

  A pair of connexon
• How many protein subunits make up a connexon?

  Six (6) protein subunits
• What is the diameter of a gap formed by a pair of connexon?

  1.5 nanometers
• What does the size limitation of the gap junction affect?

  It limits the size of transmitted molecules
• What does the gap junction allow in terms of nutrient exchange?

  Exchange of nutrients without loss into intercellular space
• What is the major transmembrane link protein in gap junctions?

  Connexin
• MICROVILLI

  Small membrane projection with cores of actin filaments that generally function to increase epithelial cells' apical surface for absorption.
• STEREOCILIA

  • Long microvilli with specialize mechanosensory function.
  • Provides the basis for the senses of touch, hearing, proprioception, pain, and the ability to sense movement.
  • Increase the cells' surface area facilitating absorption.
  • Longer and less motile than microvilli and show branching distally.
• Cilia

  • Larger projecting structures with a well-organized core of microtubules in which restricted, dynein-bases sliding of microtubules causes ciliary movement that propel material along an epithelial surface.
  • Made up of I | microtubules.
  • For movement substances.
  • Motile cilia exhibit rapid beating pattern which responsible for the movement of the cilia, suspended matter in one direction along the epithelium.
  • Axoneme is a 9+2 assembly of microtubules.
  • Responsible to the movement and rapid beating pattern.
• Pseudostratified Epithelium

  • Made up of closely packed cells that appear to be arranged in one layer because of different sizes and orientation of the nucleus.
• Transitional Epithelium/Urothelium

  Can be found in the ducts of the prostate glands as well as the lining of the urinary bladder, ureters, and urethra.
• Pseudostratified Columnar

  Epithelium

  It moves the substances along the surface of the epithelium.
• Stratified Squamous Epithelium

  Keratinized

  • It moves gradually from the basal surface going to the surface layers of the tissue.
• Keratin prevents dehydration from our tissue and protects tissue specifically epidermis of the skin.
• MESOTHELIUM

  • MESO - middle
  • Serous lining of cavities such as pericardium, pleura, peritoneum for lubrication.
• ENDOTHELIUM

  • Made up of flat cells that lines the blood vessel
• MYOEPITHELIUM

  • Basket cells
  • To remodel the scars in the skin.
• ENDOMETRIUM

  • Lining of the uterus.
• GERMINAL EPITHELIUM

  • Layer of the ovaries and seminiferous.
• GLANDUALAR EPITHELIUM

  • Responsible for the secretion of different molecules or substances in our body.
  • for secretion
• EXOCRINE GLANDS

  • They have epithelial ducts carrying secretions to specific sites
  • The ducts of simple glands are unbranched and those of compound glands are branched.