Gas exchanges

what must exchange gasses with the environment

all organisms

simple diffusion

how gasses are exchanged (slow)

small organisms simple diffusion

require large SA:V

large organisms simple diffusion

specialized gas exchange ratio

properties of gas exchange surfaces

• permeable

• large SA:V

• moist

• thin

permeable

can diffuse freely

• eg O2 and CO2

moist

gasses can dissolve

• interrestrial organisms have surface covered by film of moisture

thin

diffuse over short distances (usually single cell layers)

maintained concentration gradient

required by diffusion

• alveoli in animal lungs

• gills in fish

adaptations of mammalian lungs for gas exchange

• branched network of bronchioles

• type 1 and 2 pneumocytes

type 1 pneomocytes

thin epithelium cells, flattened, line inner surface, 95% SA in alveoli

type 2 pneumocytes

secret pulmonary surfactant in alveoli walls

• similar to phospholipids

• form monolayer on surface of moisture lining

• reduces surface tensions and prevents sides of alveoli sticking together upon exhalation

ventilation of the lungs

trachea and bronchi have cartilage in walls so they stay open

bronchioles have smooth muscle fiber in walls → allow widths to vary

inspiration (inhalation) (active)

• external intercostal muscles contract and move ribs up and out

• abdomen wall muscles relax

• diaphragm contracts

• thoracic cavity volume increases

diaphragm contracts

pushes abdomen wall out

thoracic cavity volume increases

pressure decreases → draws air in

expiration (exhalation) (passive)

• internal intercostal muscles contract and move ribs down and in

• abdomen wall muscles contract

• diaphragm relaxes

• thoracic cavity volume decreases

diaphragm relaxes

moves up

thoracic cavity volume decreases

pressure increases → pushes air out

measuring lung volumes

• tidal volume

• inspiratory reserve volume

• expiratory reserve volume

• vital capacity

tidal volume

volume of fresh air inhaled or stale exhaled → normal breath

inspiratory reserve volume

volume of air can inhale forcefully after normal inhale

expiratory reserve volume

volume of air can exhale forcefully after normal exhale

vital capacity

total volume of air that can be exhaled after max inhalation

gas exchange in leaves

• waxy cuticle

• epidermis

• spongy mesophyll

• palisade mesophyll

• veins

waxy cuticle

reduces loss of water and permeability to gasses

epidermis

reduces water loss/layer of protection

• contains stomatal guard cells

stomatal guard cells

changes shape to open/close pore

• takes in CO2 and releases O2

spongy mesophyll

site of gas exchange/moist

• contains air spaces

veins

contains xylem for water transport to the leaf cells

• phloem (food transport)

palisade mesophyll

photosynthesis occurs because there is more sun

transpiration

consequence of gas exchange in a leaf

• water loss due to opening of stomata in plants (during photosynthesis)

leaves to atmosphere

transpiration through stomata

evaporation

liquid → gas

factors affecting transpiration

• temperature (positive relationship)

• humidity (negative relationship

• wind (positive relationship) - biggest factor