PP 1Gas exchange

Features of gas exchange in animalsFish Humans•The gills of a fish are like alveoli: give oxygen to blood and take the carbon dioxide from the blood along with other nutrients in the water.

•Lungs remain moist simply because of their location within the body.

•Most fish are unable to breathe on land because the structure of air does not support their gills, leading to their collapse.

•There would also be too much water loss due to evaporation, and both gills and lungs need to remain moist.

•When oxygen rich water is passed over their gills, the blood in the capillaries flowing in the opposite direction to the water in a process called counter current exchange, the fish are able to absorb all the oxygen they require.

•The deoxygenated water then returns to the surrounding water through openings in the side of the pharynx.

•The alveoli in humans do the same thing except for getting nutrients.

•From the alveoli - the blood then carries O2 to all our cells via our many capillaries, (no cell is more than a few mm away from one.)

Inspired vs. expired airInspired air Expired air

Oxygen % 21 16

CO2 % 0.04 4

N % 78 78

Water vapor Variable High

•Body produces CO 2 due to respiration• Nitrogen diffuses into blood and then diffuses back out (inspire/ expire)

Know the differenceVentilation: pumping mechanism that moves air

into and out of the lungs efficiently, thereby maintaining the concentration gradient of diffusion

Gas Exchange: The exchange of gases between an organism and its surroundings (uptake of oxygen and release of carbon dioxide in animal and plants)

Cell Respiration: The controlled release of energy in the form of ATP from organic compounds in cells (a continuous process in all cells)

Intercostal Muscles

Internal and External Intercostal Muscles (ICM)

Steps to ventilationInspiration (inhale) Expiration (exhalation)

Diaphragm contracts down (pushing abdominal down)

Diaphragm relaxes and pulls up (pressure from abdominal pushes up)

External (ICM) contractInternal (ICM) relax

External (ICM) relaxesInternal (ICM) contracts

Ribs move up and out Rib cage moves down and in

Volume of thorax cavity increases

Volume of thorax cavity decreases

Air pressure of thorax drops (below atmospheric pressure)

Air pressure of thorax rises above atmospheric pressure

Air flows in Air flows out

Mucus / Cillia / Gas ExchangeMucous Membranes - a physical barrier

that traps potential pathogensEpithelium cells form mucus membrane

(more fragile than skin)Constantly flushed with fluids ( mucus,

saliva, tears)

CiliaCILIA in the trachea - move inhaled

material trapped in the mucous to the top of the trachea where it is dumped down the oesophagus to be destroyed by stomach acids (HCl)and enzymes.

Eye lashesCilia moves in unison – moving moving along partials like a brush

Nicotine in tobacco can kill these cells!

Exercise on Breathing Muscles work hard – rapid respiration Faster respiration – more CO2 generated CO2 goes to blood and dissolves in blood plasma It produces a weak acid – carbonic acid (lowers

pH)Brain detects pH changeSends signal to intercostal muscle & DiaphragmCausing these muscles to contract hard and fastResult – rapid breathing Therefore fast oxygen delivery to cells / CO2

removal faster