B3 Flashcards
Gas exchange
all organisms absorb gas from the environment and release one
Exchange surfaces must have these properties
- Permeable - oxygen and carbon dioxide can diffuse freely
- Large - the surface area is large in relation to the volume of an organism
- Moist - the surface area is covered by a film of moisture in terrestial organisms so gases can dissolve
- Thin - the gases must diffuse only a short distance, in most cases through a single layer of cells
Explain how concentration gradients are maintained at exchange surfaces in animals
Through a combination of 2 processes:
1. Ventilation - animals actively replace the air near their gas exchange surfaces to ensure fresh oxygen-rich air is brought and carbon dioxide air is removed. HIGH OXYGEN, LOW CO2
2. Blood flow - blood is pumped through dense capillary networks located close to the exchange surfaces. Blood arriving at the exchange surface is HIGH IN CO2 and LOW IN OXYGEN, it has collected watse products from tissues. As oxygen and carbon dioxide diffuses, the blood is replaces with deoxygenated blood. This ensures the concentration gradients across the exchange surface are maintained
Adaptation of mammalian lungs for gas exchange
Alveoli - its shape further increases surface area, one cell thick walls, moist walls help gases dissolve in them
Pneomocytes - cells that line alveoli and compromise of the majority of the inner surface of lungs
Type 1: involved in the process of gas exchange between alveoli and capillaries - extremely thin
Type 2: responsible for the secration of PULMONARY SURFACTANT, which reduces surface tension in the alveoli.
Explain the process of ventilation - inhaling
Inhaling (inspiration):
*the external intercostal muscles contract, moving the ribcage up and out
*the diaphragm contracts, becoming flatter and moving down
*these muscle movement increase the volume of thorax
*the pressure inside the thorax therefore drops below atmospheric pressure
*air flows into the lungs from outside the body until the pressure inside the lungs rises to atmospheric pressure
Explain the process of ventilation - exhaling
Exhaling/expiration
*The internal intercostal muscles contract, moving the ripcage down and out
*the abdominal muscles contract, pushing the diaphragm up into a dome shape
*these muscle movements decrease the colume of the thorax
*the pressure inside the thorax therefore rises above atmospheric pressure
*air flows out from the lungs to outside the body until the pressure inside the lungs falls to atmospheric pressure
Tidal volume
the volume of fresh air inhaled or the volume of stale air exhaled with each ventilation
Vital capacity
the total volume of air that can be exhaled after a maximum inhalation
Inspiratory reserve volume
the amount of air a person can inhale forcefully after normal tidal inhalation
Expiratory reserve volume
the amount of air a person can exhale forcefully after normal tidal exhalation
Ventilation rate
the number of times that air is drawn in or expelled per minute
Device used to measure lung columes
a spirometer
Capillaries
Smallest blood vessels and serve as the site material exchange between blood and tissues
Adaptations:
*Large surface area - vast network of capillaries provides enormous surface area for exchange
*Thin walls - one cell thick, allowing for every diffusion of substances
*Slow blood flow - reduced speed allows more time for exchange
Arteries
Carry oxygenated blood away from the heart to body’s titssues.
*Thicker wall, narrower lumen, inner surface corrugated
*Elasticity allows arteries to expand and recoil maintaining blood pressure
*3 layers - collagen fibres (make arteries strong enough to withstand high blood pressure without bursting), smooth muscle and endothelium
Veins
carry low pressure blood from the organs to the heart.
Thin walls - low blood pressure
large lumen
smooth inner surface
valves - contain one-way valves that prevent backflow of blood
