Diversity of all cell types

cell are genetically identical in a …

complex multicellular organism

some cellular functions need to be carried out by all cells

housekeeping functions

Differentiation

is the process by which an unspecialised cell develops into a specialised cell with a particular structure and function.

Cells are organised into tissues

epithelial tissue, nervous tissue, connective tissue, muscle tissue

What do epithelial cells form/

sheets that cover the inner and outer body surfaces

Absorptive cells

Have microvilli to increase their surface area

Ciliated cells

Have cilia which beat to move substances over the sheet

Secretory cells

Secrete substances out onto the sheet

Types of epithelial cells

Secretory epithelial cells

Often collected together to form glands … secretion of substances such as gastric juice and mucus

Exocrine glands

Secrete products into ducts

Endocrine glands

Secrete hormones into the blood

Neurones

Specialised for communication. The axon conducts electric signals away from the cell body.

Rod cells

Rod cells are specialised sensory cells in the retina. layers of disks contain the light sensitive pigment rhodopsin. Light evokes ab electrical signal transmitted to the brain.

Red blood cells also known as

erythrocytes

1cm³ blood contains

5 billion erythrocytes

Erythrocytes

Highly specialised cells for transportation of oxygen. Major protein component is haemoglobin.

Why can erythrocytes no longer replicate?

Have lost their nuclei and internal membranes. Lifespan - 120 DAYS

Where do connective tissues fall the spaces between

epithelial sheets and tubes. Fibroblasts and other cells secrete extracellular matrix.

Connective tissue- specialised forms- bone

• Made by osteoblasts, held together in the extracellular matrix.

• Calcium salts deposited in the cell matrix to form solid bone

Connective tissue- specialised forms- adipocytes

Produce and store fat. The cell contents are pushed aside by a large lipid droplet.

muscles

produce mechanical force by contraction and have 3 types in vertebrates.

skeletal muscle

moves joints, strong rapid contraction. striated.

smooth muscle

found in digestive tract, bladder, arteries and veins. not striated.

cardiac muscle

only found in the heart, produces the heart beat. Adjacent cels linked by electrically conducting junctions.

What are all cells derived from.

A single fertilised egg.

• embryonic stem (ES) cells {these are totipotent EXCEPT foetal membranes)

Stem cells in adult organisms

Pluripotent stem cells produce cells of a particular tissue. Monopotent stem cells produce only one cell type.

Differentiation is the end point

once a cell has fully differentiated it has limited or no capacity to divide.

colony- stimulating factors (CFS)

Can affect all aspects of hemopoiesis

Differentiated cells have a limited lifespan

• different cell types have different half lives eg skin v nerve cells

• stem cell pool

“normal” cell death is by apoptosis

evolutionarily conserved, genetically regulated process, morphologically
distinct cell death; roles in embryogenesis, tissue homeostasis, damage
limitation, control and functioning of immune system

maintenance of homeostasis … two gene families involved

Bcl-2 family (regulation) and caspase (execution) plus many accessory proteins e.g. DD proteins.

What happens when apoptosis goes wrong?

Too little apoptosis - cancer, autoimmune disease (immune cells) and prolonged viral infection

Too much apoptosis - neurodegenerative diseases, autoimmune disease, additional tissue damage following trauma, progression of AIDS.

3 ways on how does Apoptosis go wrong:

• Apoptosis controlling genes damaged or aberrantly expressed

• Inappropriate triggering

• Interference by exogenous genes (viral, bacterial, parasitic).

Cells are genetically identical, differentiated cells express different subsets of genes

Transcriptome and Proteome

differentiation is normally

irreversible

Tissue specific gene expression is primarily regulated at the level of

transcription

mECHANISMS OF DIFFERENTIATION - Development of organs and drug safety.

Pharmacogenetics - our genetic makeup can influence how we respond to medications.

cells within a multicellular organism are

genetically identical although perform different functions.