Gas Exchange Flashcards
Cellular respiration
- A chemical process taking place inside cells
- Glucose reacts with oxygen to produce carbon dioxide, water and energy (ATP and heat)
Breathing
- Mechanically ventilating the lungs
- Inhaling oxygen rich air and exhaling carbon dioxide rich air
Gas exchange
- A physical process taking place by diffusion
- Between air in the alveoli and blood
- Between the blood and tissues of the body
Diffusion
- Movement of a substance from a high to a low concentration until equilibrium
- No energy input required
Requirements for efficient gas exchange surface
- thin surface
- moist surface
- large surface area
- protected surface
- transport system close to surface
- adequate ventilation
Plant large surface for gas exchange
- Spongy mesophyl inside leaves
- Leaves themselves have a large surface area
Earthworm large surface for gas exchange
- Entire body surface can exchange gases
Insect large surface for gas exchange
- Tracheal system of branching tubes
- Ending in tiny channels called tracheoles
Fish large surface for gas exchange
- Gills with filaments and lamellae (folds)
Plant thin surface for gas exchange
- Gases exchanged directly into leaf cells
Earthworm thin surface for gas exchange
- Gases exchanged across columnar epithelium (short distance)
Insect thin surface for gas exchange
- Tracheoles very thin permeable walls in close contact with cells
Fish thin surface for gas exchange
- Very finely structured gills, water and blood in close contact
Moist surface for gas exchange in plants
- Water moves through xylem into the leaf and evaporates by transpiration
Moist surface for gas exchange in earthworm
- Epithelium secretes mucus
Moist surface for gas exchange in insects
- Exoskeleton prevents insect from drying out
Moist surface for gas exchange in fish
- Fish lives in water
Ventilated surface for gas exchange in plants
- Leaves exposed, constantly ventilated by air movement
Ventilated surface for gas exchange in earthworm
- Surface of worm exposed to air trapped between soil particles
Ventilated surface for gas exchange in insects
- Air sacs in tracheal system close to muscles
- When muscles contract and relax air is drawn into the tubes
Ventilated surface for gas exchange in fish
- As fish swim, water flows over gills
- Operculum also acts as a pump
Transport system for efficient gas exchange in plants
- Gases exchanged directly with cells in the leaf
Transport system for efficient gas exchange in earthworm
- Worm has a closed blood system with haemoglobin
- Capillaries close to surface of the skin
Transport system for efficient gas exchange in insects
- Oxygen diffuses directly from tracheoles to cells
Transport system for efficient gas exchange in fish
- Blood flows in vessels in opposite direction to water flow
Protection of gas exchange surface in plants
- Stoma and waxy cuticle protect the inside layers of the leaf
Protection of gas exchange surface in earthworm
- Protective layer of skin called cuticle
Protection of gas exchange surface in insects
- Exoskeleton of insects protects system
- Openings protected by valves called spiracles
Protection of gas exchange surface in fish
- Bony flap called operculum covers gills
Efficient gas exchange in humans
- Thin: walls of alveoli and capillaries single celled, flattened squamous epithelium
- Moist: lining of epithelium in alveoli covered in a thin layer of moisture
- Surface area: millions of alveoli air sacs add up to a large surface area
- Protection: thoracic cage made up of rib bones and muscles
- Transport: alveoli supplied by capillaries containing blood
- Ventilation: breathing system by muscles and rib bones
Function of nostrils
- Opening to air passages
- Lined with hairs to remove dust from inhaled air
Function of nasal passages
- Lined with ciliated columnar epithelium which secretes mucus
- Mucus moisten air and filters dust and germs by trapping these
- Turbinate bones slow air flow so it can be warmed by nearby blood
Function of pharynx
- Common to both air and food.
- Leads to trachea via valve called the glottis
Function of the larynx
- Also called the voice box as this contains vocal cords
- Guards the entrance to the trachea
- When food swallowed the glottis is closed by the epiglottis to prevent food entering trachea
Function of the trachea
- Held open by c-shaped rings of cartilage
- Lined with ciliated epithelium to remove dust etc.
Functions of bronchi and bronchioles
- Trachea divides into bronchi also with cartilage to hold them open
- Bronchi divide into numerous bronchioles
- These branch until ending in the alveoli
External structure of the lungs
- Cone shaped
- Base touches diaphragm
- Pleural membranes (pleura) line the inside of thoracic cavity and the outside of each lung
- Between pleura is pleural fluid that reduces friction during breathing
Internal structure of lungs
- Bronchi subdivide to form bronchioles
- Smallest bronchioles end in alveoli
- Walls of alveoli made of flattened squamous epithelium
- Each alveolus surrounded by a network of capillaries
- Walls of capillaries have a single layer of endothelium.
- Pulmonary artery (deoxygenated blood) enters the lung
- Pulmonary vein (oxygen rich) leaves the lungs
Mechanism of inhalation
- Diaphragm contracts and flattens
- External intercostal muscles contract
- Internal intercostal muscles relax
- Rib cage is lifted
- Internal volume of thoracic cavity increases
- Internal pressure decreases
- Air rushes into lungs
Mechanism of exhalation
- Diaphragm relaxes and moves up
- External intercostal muscles relax
- Internal intercostal muscles contract
- Rib cage is dropped
- Internal volume of thoracic cavity decreases
- Internal pressure increases
- Air rushes out of lungs
How is oxygen transported
- Oxyhaemoglobin (98,5%)
- Dissolved in blood plasma (1,5%)
How is carbon dioxide transported?
- Bicarbonate ions (70%)
- Carbaminohaemoglobin (23%)
- Dissolved in blood plasma (7%)
Gas exchange in the lungs after inhalation
- Alveolus has a high concentration of oxygen and a low concentration of carbon dioxide
- Blood capillaries have a high concentration of carbon dioxide and a low concentration of oxygen
- The oxygen diffuses from the alveolus into the blood
- The carbon dioxide diffuses in the opposite direction from the blood into the alveolus
Gas exchange in the tissues
- Blood arriving at the tissues has a high concentration of oxygen.
- The tissues have a high concentration of carbon dioxide.
- The oxygen diffuses from the blood into the tissues.
- The carbon dioxide diffuses in the opposite direction from the tissues into the blood.
Composition of inhaled vs exhaled air
- Inhaled oxygen 21% vs. exhaled oxygen 16%
- Inhaled carbon dioxide 0,04% vs. exhaled carbon dioxide 4%
- Nitrogen stays the same at about 79%
- Water vapour increases
To be continued…
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