Diversity of cell types in multicellular organism Flashcards
Give examples of different cell types
(cells are organised into tissues)
• epithelial
• nervous tissue
• connective tissue
• muscle tissue
What is differentiation?
The process of producing different cell types
What is epithelia and the cells within?
• epithelial cells form sheets that cover the inner and outer body surfaces
- absorptive cells have microvilli to increase SA
- ciliated cells have cilia which beat to move substances over the sheet
- secretory cells secrete substances out onto the sheet
What are the types of epithelial tissue and their example?
• simple squamous (lung)
• simple cuboidal (kidney)
• simple columnar (stomach)
• pseudo-stratified columnar (trachea)
• stratified squamous (oesophagus)
• stratified cuboidal (sweat gland)
• stratified columnar (salivary duct)
• transitional (bladder)
What do secretory epithelial cells do?
• often collected together to form glands for secretion of substances eg gastric juice and mucus
- exocrine glands: secrete product into ducts
- endocrine glands: secrete hormones into the blood
How are neurones specialised and how do they work?
• specialised for communucation
• The axon conducts electric signals away from the cell body
What are rod cells and how do they work?
• Specialised sensory cells in retina
- layers of disks contain light sensitive pigment rhodopsin
- light evokes an electrical signal transmitted to the brain
What are red blood cells specialised for?
• Specialised for transportation of oxygen so major protein component is haemoglobin
How many red blood cells does 1cm^3 of blood contains?
and can they replicate?
• 5 billion erythrocytes
• can no longer replicate due to loss of nuclei and internal membranes. Their lifespan is ~120 days
What is connective tissue and give examples of specialised forms?
• they fill spaces between epithelial sheets and tubes (fibroblasts and other cells secrete extracellular matrix)
- bone: calcium salts deposited in the cell matrix to form solid bone
- adipocytes: produce and store fat
What does skeletal muscle do?
move joints, strong rapid contraction. striated
where is smooth muscle found?
found in digestive tract, bladder, arteries and veins. not striated
What does cardiac muscle do?
Only found in heart- produces heart beat. Adjacent cells linked by electrically conducting junctions
What does totipotent mean?
able to differentiate into any type of cell- eg embryonic stem cells
How does differentiation occur in adult organisms?
• pluripotent stem cells produce cells of a particular tissue
• monopotent stem cells produce only one type of cell
• differentiation is the end point- once a cell has fully differentiated it has limited or no capacity to divide
How does differentiation happen from stem cells in the bone marrow? (hemopoiesis)
1) hematopoeitic stem cells collected from bone marrow
2) these become either lymphoid progenitor cells or myeloid progenitor cells
3) lymphoid progenitor cells become T-Cells or B-cells
4) Myeloid progenitor calls become other blood cells eg RBC, platelets, neutrophyls etc
How is homeostasis maintained?
• Differentiated cells have a limited lifespan
• Apoptosis- programmed cell death
• Two main gene families involved- Bcl-2 family (regulation) and caspase (execution)
What happens when apoptosis goes wrong?
• Too little
- cancer
- autoimmune diseases (immune cells)
- prolonged viral infection
• Too much
- neurodegenerative diseases
- autoimmune diseases
- additional tissue damage following trauma
- progression of AIDS
How does apoptosis go wrong?
• apoptosis controlling genes damaged or aberrantly expressed
• inappropriate triggering
• interference by exogenous genes (viral, bacterial, parasitic)
What are the mechanisms of differentiation?
• cells are genetically identical, differentiated cells express different subsets of genes (transcriptome and proteome)
• tissue specific gene expression is primarily regulated at the level of transcription
• development of organs and drug safety
Give a summary of specialisation
• Cells within a multicellular organism are genetically identical although they perform different functions
• stem cells can give rise to multiple cell types
• differentiation is normally irreversible
• differentiation is achieved through expression of different subsets of genes in different cells
