Cells and differentiation

• Differentiation


  the process by which cells develop suitable structural features that allow them to carry out their specific functions
• During growth and development, organisms’ cells:

  -are constantly dividing through mitosis, with the exception of sex cells.

  -the division produces identical copies of the parent cell, containing the same genetic material.

  -specific genetic material is activated depending on where the undifferentiated cell is located in the body

  -the genes activated determine the structure of the cell (differentiatio), and therefore its specialised function.

  -once differentiated, cells, lose the ability to change into other cell types.
• Specialised cells of a multicellular organism can’t survive on their own.
• In order to function efficiently, there must be communication and collaboration between specialised cells.
• plants rely on chemical and physical contact, as there are no nerve cells or central control system
• cells involved in substance exchange have features that increase SA:V ratio. red blood cells are very small and biconcave, increasing SA:V ratio. this allows for movement in tiny capillaries, are rapid diffusion of oxygen. the absence of a nucleus or organelles allows the cells to carry more haemaglobin.
• animal cells-connective tissue:

  -varies in form and function, is made up of an extracellular matrix, composed of collagen and elastin, and cells are scattered throughout the extracellular matrix.
• nervous system: brain, spinal cord and peripheral nerves
• nerve cells are known as neurons, too
• nerve cells are highly specialised for sending messages between themselves and other cells in the body
• nerve cells consist of multibranched dendrites and an axon that extends out from the cell body
• dendrite: branching structure that receives information from other neurons and sends it to the cell body
• axon: the long extension of a neuron that carries nerve impulses away from the cell body
• in nerve cells, the branched structure increases the surface area of the dendrite, allowing for more effective reception of signals
• in nerve cells, signal take the form of electrical message
• muscle cells have an elongated from
• muscle cells can lengthen and shorten
• skeletal muscle:

  • long and striated fibres
  • attached to the bone
  • the contractions of the muscle cause the organism to move
• cardiac muscle:

  • striated
  • found in the heart
  • individual cells have connected junctions, allowing for coordinated pumps of the heart
• smooth muscle:

  • non-striated fibres
  • their contractions push substances through specialised organs eg blood vessels
• epithelial cells are densely packed and can occur in single sheets or layers, depending on their location
• epithelial tissue:

  • covers body surfaces
  • protects organs
  • forms glands
  • doesn't have blood vessels so they rely on underlying connective tissue for nutrients
  • may be specialised for absorption or secretion
• connective tissue:

  • varies in from and function
  • made up of extracellular matrix, composed of collagen and skin
• type of connective tissue-adipose tissue:

  • contains fat storage cells storing energy, providing insulation, protection and cushioning
• type of connective tissue-cartilage:

  • contains many dense collagen fibres, providing strength, flexibility and cushioning.
  • found in nose, joints and ribcage
• type of connective tissue-collagen:

  • an elastic fibrous that allows skin te maintain its shape and place, stopping it from being torn from the bone