cell differentiation : principles and applications of science

the nucleus of all human cells contain 23 pairs of chromosomes
these chromosomes are made of DNA
the DNA contains information in the form of genes
each gene contains a particular characteristic
genes controls the activities inside the cell
genes code for production of proteins inside the cell
these proteins have an effect on function of cells and are often enzymes
there are approximately 20,000 different genes in a human and all human cells process all 20,000 genes
in a developing red blood cell the gene for producing haemoglobin (a protein) would be switched on
in a developing bone cell this same gene is switched off

epithelial tissue - this is a tissue that either covers or lines an organ for example - blood vessels or the lining of gut
epithelial tissues forms the inner surface of glads that secrete substances such as sweat and digestive enzymes
simple epithelial : squamous, cuboid, columnar, ciliated
muscle tissues : skeletal muscle - movement (attached to the bone)
cardiac muscle - in the heart
smooth muscle - in the walls of artery,gut and the bladder
nervous tissue : transmit nerve impulses to the brain and they are the body’s communication system
connective tissue : any supporting tissue in an organism
consists of a non-living supporting matrix ; often containing protein fibers
living cells are present within in matrix
these cells often produce the matrix
includes : bones, cartilages, tendons, ligaments, blood, areolar tissue, adipose tissue
tendons are attached muscles to the bone
ligaments also attach to the bone
areolar tissue holds things together eg: skin and muscle in a chicken
adipose is a fatty tissue