Cells, Tissues and Homeostasis

• Ten organ systems of the human body are the:

  Nervous system, Endocrine system, Reproductive system, Respiratory System, Cardiovascular system, Digestive system, Urinary system, Musculoskeletal system, and integumentary system
• •Homeostasis is the regulation and maintenance of the internal environment
• •Pathology is the disease or illness (pathos = suffering)
• The study of bodily functions in a diseased state situation = pathophysiology
• The Extracellular Matrix compose of proteoglycans (a glycoprotein) and insoluble protein fibres.
• The ECM plays a role in physiological processes (such as growth, development and death)
• ECM

  Insoluble protein fibres such as collagen, fibronectin and laminin  provide strength and anchor cells in the tissue (particularly in cartilage and bone)
• Tissues with extensive ECM present include epithelial, neural and muscle
• Plasma in the blood and lymph are classed as an extracellular matrix!
• The Three main cell junctions in the body is the anchoring junctions, gap junctions, and tight junctions.
• The different types of anchoring junctions found in tissues are desmosomes, hemidesmosomes, focal adhesion and adherens junctions.
• Adherens Junctions (binding cell to cell)
• •Desmosomes (binding cell to cell)
• •Hemidesmosomes (binding cell to extracellular matrix)
• •Focal Adhesions (binding cell to extracellular matrix)
• All these junctions occur via proteins called CAMs (Cell Adhesion Molecules)
• •Many CAMS also extremely important in transient junctions needed in white blood (immune) cell communication and movement from blood to infected tissue during an inflammatory immune response.
• Cell adhesion molecule are membrane bound proteins such as: Cadherins which are proteins that link two cells together and

  Integrins which link the cytoskeleton of a cell to extracellular matrix proteins.
• Adherens Junctions

  These link actin fibres of the cytoskeleton together between adjacent cells, using cadherin proteins. This is therefore a cell/cell junction.
• Desmosomes, like adherens junctions, also use cadherin protein to link adjacent cells together but via intermediate filaments in the cytoskeleton, not actin.They are the strongest of the cell/cell junctions.
• Hemidesmosomes use cell surface integrin proteins to link keratin of the cell to the laminin protein found in the extracellular matrix.

  (cell/ECM interaction)
• Focal Adhesions:

  Also use integrin proteins to link cellular actin cytoskeleton fibres to mainly fibronectin proteins in the extracellular matrix.

  (cell/ECM interaction)