histology

• Epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue, and nervous tissue.
• Marcelo Malpighi
• Anton philips van leewonhoekmade the first funcvtional microscope
• robert hooke introduced the word "cell"
• Caspar Friedrich Wolf "globules" " vesicle"
• Marie Francois Xavier Bichat father of modern histology and pathology
• lorenz oken presented a hypothesis trhat plant sand animals have repeated vesicle
• robert brown discovered the nucleus
• Matthias Jacob Schleiden declared that the cell is the basic building block of all plant matter
• Theodore Schwann "cell theory"
• Johannes evangilista purkinje pioneer in histology, embryology, and oharmacology
• Rudolf Ludwig Karl Virchow "omni cellula e cellula" or " all cells from cells" made the first electron microscope
• Cells - the basic functional and structural unit of living organisms.
• Eukaryotic cell, a cell type that has a true nucleus surrounded by nuclear membrane or envelope
• Prokaryotic cell which lacks a nuclear envelope and the nuclear substance is mixed or in direct contact with the rest of the protoplasm.
• The principal parts of a cells are the cell membrane, cytoplasm and nucleus.
• Cell Membrane - is the cytoplasmic component that is not clearly distinguishable in common hematoxylin and eosin stained preparation
• the Cytoplasm appears pinkish or reddish, and the Nucleus appears intensely blue or purple in color.
• Cell Membrane forms the outer boundary of all eukaryotic cells. They are also called plasma membrane or plasmalemma.
• ESSENTIAL FUNCTIONS OF CELL MEMBRANE

  - Gives shape to the cell.

  -Involves in cell to cell communication.
• Under the light microscope, the cell membrane is INVISIBLE, But under Electron Microscope, the cell membrane as a TRILAMINAR MEMBRANE
• membrane can be divided into 2 groups :

  Integral proteins — proteins that are directly incorporated within the lipid bilayer.

  Peripheral proteins — exhibit a lesser association with membrane surfaces.
• CELL COAT — is a surface coat made up of carbohydrates rich or polysaccharides components. covering part of cell membrane
• SPECIALIZATION OF CELL MEMBRANE

  1. Junctional Complexes
  2. Invaginations
  3. Microvilli

  4. Stereocilia

  5. Cilia
• Junctional Complexes

  • Structures that provide for cell attachment.
• 1. Macula Adherens (desmosomes)—It is a complex disk-shaped structure or cytoplasmic faces of cell membrane -attachments of the cytoskeleton
• 1. Zonula Adherens- (intermediate junction of Facia Adherens)This is acellular ring of attachments which increases the surface contacts of cells.
• Zonula Occludens (Tight junctions)-

  formation of a barrier that prevents the free passage across the epithelium.
• Nexus ( Gap Junction)It is a communicating junction in epithelial, muscular and nervous tissues.

  -Its significance Is for cell to cell communication.
• Invaginations

  A modification of cell membrane; maybe in the form of infoldings or vesicular pits.
• Infoldings This greatly increase the cell surface.
• Vesicular pits

  —This type occurs as pinocytic vesicles and phagocytic vesicles
• Pinocytic vesicles are drop-like Invaginations of the cell membrane.

  -Pinocytosis literally

  * means " cell drinking".
• phagocytosis —which literally means "cell engulfing".
• pinocytic and phagocytic vesicles that break off from the cell membrane are referred to as —phagosomes.
• Microvilli

  • It is a fingerlike projection of absorptive epithelial cells on free surfaces of cell membrane.
• Stereocilia

  -long process in the apical region of cell membranes.

  -a non-motile cilia

  -does not have the structure of a cilia.
• Cilia

  • It is an elongated, hairlike process,

  -found in the respiratory passages.
• CYTOPLASM

  -is the colloidal suspension of the cell. -It is composed of matrix, termed the "Cytosol"
• ORGANELLES

  -present in all eukaryotic cells

  -have a limiting membrane and contain enzymes that participate in cellular metabolic activity.

  -These are permanent components of the cytoplasm.