Module 3 Exchange Surfaces Flashcards
Why do multicellular organisms need exchange surfaces?
Have a large size, small surface area to volume ratio and high metabolic rate, so
diffusion alone is not sufficient for exchange of substances e.g. oxygen.
What are common features of specialised exchange surfaces?
Large surface area
Short diffusion distance
Good blood supply and ventilation
What are the adaptations of the alveoli/lungs to exchange oxygen and carbon
dioxide?
Lots of alveoli provide large surface area.
Individual alveoli have a large surface area to volume ratio
One cell thin walls made of squamous epithelium tissue to provide a short diffusion
distance.
Surrounded by a network of capillaries for good blood supply to maintain a steep
concentration gradient.
Pulmonary surfactant inside the alveoli stops the walls sticking together and the
alveoli collapsing.
Elastic fibres in walls for stretch and recoil.
Describe the structure of the trachea
Lined with ciliated epithelium tissue.
Cilia waft mucus and foreign particles back up the trachea to stop them reaching the
alveoli, instead being swallowed.
Goblet cells secrete mucus into the trachea to trap pathogens and other foreign
particles.
C shaped cartilage rings to prevent the trachea from collapsing.
Mainly made of smooth muscle.
Describe the structure of the bronchi.
Contain cartilage and smooth muscle, similar to the trachea.
Describe the structure of the bronchioles
Split off from the bronchi into smaller tubes.
No cartilage
More smooth muscle and elastic fibres.
Able to constrict/narrow or relax/widen in order to control air flow to the alveoli.
Explain the process of inhalation
The diaphragm contracts, flattening and lowering, and the external intercostal
muscles contract, pushing the ribcage upwards and outwards.
The volume of the thorax increases and pressure decreases.
Why do multicellular organisms need exchange surfaces?
Have a large size, small surface area to volume ratio and high metabolic rate, so
diffusion alone is not sufficient for exchange of substances e.g. oxygen.
What are common features of specialised exchange surfaces?
Large surface area
Short diffusion distance
Good blood supply and ventilation
What are the adaptations of the alveoli/lungs to exchange oxygen and carbon
dioxide?
Lots of alveoli provide large surface area.
Individual alveoli have a large surface area to volume ratio
One cell thin walls made of squamous epithelium tissue to provide a short diffusion
distance.
Surrounded by a network of capillaries for good blood supply to maintain a steep
concentration gradient.
Pulmonary surfactant inside the alveoli stops the walls sticking together and the
alveoli collapsing.
Elastic fibres in walls for stretch and recoil.
Describe the structure of the trachea
Lined with ciliated epithelium tissue.
Cilia waft mucus and foreign particles back up the trachea to stop them reaching the
alveoli, instead being swallowed.
Goblet cells secrete mucus into the trachea to trap pathogens and other foreign
particles.
C shaped cartilage rings to prevent the trachea from collapsing.
Mainly made of smooth muscle.
Describe the structure of the bronchi.
Contain cartilage and smooth muscle, similar to the trachea.
Describe the structure of the bronchioles
Split off from the bronchi into smaller tubes.
No cartilage
More smooth muscle and elastic fibres.
Able to constrict/narrow or relax/widen in order to control air flow to the alveoli.
Explain the process of inhalation
The diaphragm contracts, flattening and lowering, and the external intercostal
muscles contract, pushing the ribcage upwards and outwards.
The volume of the thorax increases and pressure decreases.
