L3 - cell organisation and specification

• Differentiation refers to the changes occurring in cells of a multicellular organism so that each different type of cell becomes specialised to perform a specific function
• Stem cells:

  -undifferentiated cells

  -capable of self renewal, and can undergo cycles of cell division while staying undifferentiated

  -cell potency refers to the varying ability of stem cells to differentiate into specialised cell types. Cells with the greatest potency can generate more cell types than those with lower potency
• Stem cell potency:

  -totipotent

  -pluripotent

  -multipotent

  -unipotent
• Totipotent cells can produce all of the differentiated cells in a organism

  -eg. cells found in the zygote
• Pluripotent cells can differentiate into most adult cell types

  -eg. embryonic stem cells
• Multipotent cells can differentiate into multiple cell types in the same lineage

  -eg. haematopoeitic stem cells can develop into all types of blood cells, including white blood cells, red blood cells, and platelets
• Unipotent cells can differentiate into only one type of cell

  -eg. skin cells
• Production of blood cells:

  -stem cells in bone marrow are called hemocytoblasts and give rise to all blood cells

  -they divide by mitosis

  -give rise to 8 to 16 proerythrocytes and are now committed to differentiate into red blood cells (erythrocytes)
• Production of blood cells:

  -haemoglobin gradually builds up

  -the cell nucleus breaks down and is extruded from the cell

  -cell organelles, such as mitochondria, are lost

  -the cell gradually gets smaller
• Specialised cells:

  -nerve cells

  -striated muscle fibre

  -epithelial cells

  -fat cells

  -smooth muscle cells

  -bone cells

  -cartilage cells

  -leucocytes

  -liver cells
• Two types of phagocytes:

  -macrophage

  -neutophil
• Gametes:

  -ovum

  -sperm
• Organising cells:

  -tissues

  -organs

  -organ system
• Tissues are a collection of similar cells that perform a common function
• Organs are a collection of tissues working together to form a function
• Organ systems are several organs working together to perform an overall life function
• Blood function:

  -transport gases and nutrients
• Specialised cells in blood:

  -erythrocytes

  -neutrophils

  -monocytes

  -platelets
• Ciliated epithelium function:

  -movements of fluids
• Specialised cells in ciliated epithelium:

  -ciliated epithelial cells

  -goblet cells
• Squamous epithelium function:

  -lining alveoli and blood vessels
• Specialised cells in squamous epithelium:

  -squamous epithelial cells
• Cartilage function:

  -provide support and protection
• Specialised cells in cartilage:

  -chondrocytes
• Skeletal muscle function:

  -contractions to move the body
• Specialised cells in skeletal muscle:

  -striated muscle fibres (multinucleate)
• Smooth muscle function:

  -contractions to move substances along tubes by peristalsis
• Specialised cells in smooth muscle:

  -smooth muscle cells
• Cardiac muscle function:

  -contraction to pump blood
• Specialised cells in cardiac muscle:

  -cardiac muscle cells
• Xylem function:

  -transport water and ions
• Specialised cells in xylem:

  -vessel elements organised into xylem
• Phloem function:

  -transport assimilates such as sucrose
• Specialised cells in phloem:

  -sieve tube elements organised into sieve tubes