Levels of organisation

the cell theory: [3]

-all living organisms are composed of one ore more cells

-cells r organisms basic units of structure, function and organisation

-cells come only from existing cells

what can stem cells do

hv potential to become any cell in the body

differentiation=

the development of a cell into a specific type

tissue=

a group of cells working tg w a common function, structure and origin in the embryo

3 types of tissues in mammal

epithelial, muscular, connective

location + structure of epithelial tissue

-covers the whole surface of the body

-made up of cells closely packed and arranged in one or more layers

-specialised to form the covering or lining of all internal and external body surfaces

-cells sit on a basement membrane made of collagen and protein

epithelial tissue on interior surface of body called

endothelium

purpose of epithelial tissue

often hv a protective or secretory function

cuboidal epithelium structure + location

-roughly square

-tissue is one cell thick

-each cell has a spherical nucleus in the centre

-found in the ducts of salivary glands and in the lining of the kidney tubules

ciliated columnar epithelium structure + location

-elongated cells

-hv cilia on their free surfaces

-found lining tubes in which substances move through -trachea + oviducts

cilia capable of what

rapid, rhythmic wavelike beatings in a certain direction

squamos epithelium structure + location

-flattened cells on a basement membrane

-fit closely tg to provide a smooth, low friction surface

-thinness enables rapid diffusion of gases

-form the walls of the alveoli and line the renal (bowmans) capsule of the nephron

3 main types of muscle tissue:

skeletal (stripped/striated), smooth + cardiac

muscle tissue made up of what

cells or fibres capable of contraction

skeletal muscle structure + location

-also known as stripped or striated muscle

-bands of long cells, or fibres held tg by connective tissue

-attached to bones of the skeleton by tendons

skeletal muscle features

-powerful contractions possible but tires easily

-generates locomotion

-under voluntary control

smooth muscle structure + location

-spindle shaped cells arranged in sheets or bundles (unstripped/ unstriated)

-found in skin, walls of hollow organs like the digestive + respiratory tracts, walls of blood vessels

smooth muscle tissue features

-contract rhythmically (less powerful than skeletal) and do not fatigue easily

-involuntary control

cardiac muscle structure + location

-only found in heart

-cells hv stripes but lack long fibres

features of cardiac muscle

-contract rhythmically without any stimulation from nerves or hormones, although they can modify their contraction

-does not tire

connective tissue structure + location

-cells separated by extracellular substance

-cells account for only a small fraction of the tissue volume

-collagen

-conatins elastic fibres + collagen fibres in an extrecellular fluid or matrix

-between the fibres r fat-storing cells and cells of the immune system

purpose of connective tissue + collagen fibres in it

connects, supports or separates tissues and organs

-collagen fibres is to add strength to the connective tissue

-collagen fibres r the dominant fibre type in most connective tissue

organ=

a group of tissues in a structural unit, working together and performing a specific function

e.g. of human organ + explain

-the eye

-contains nervous, connective, muscle + epithelial tissues

-organ of sight

e.g. of plant organ + explain

-a leaf

-contains epidermal, vascular, packing tissue

-specialised 4 photosynthesis

organ system=

a group of organs working tg to perform specific functions

e.g. organs of the organ systems:

1-excretory

2-skeletal

3-circulatory

4-respiratory

5-nervous

1-kidney, bladder

2-cranium, femur

3-heart, aorta

4-trachea, lung

5-brain, spinal cord

whats a organism

all the systems of the body work tg making an organism which is a discrete individual