exchanging substances in organisms *3

• in mammalian gas exchange systems what is the trachea?

  a flexible airway lined with cells and supported by rings of cartilage, through which air moves toward and away from the lung.
• the trachea and large bronchi are supported by cartilage. how does this adaptation help support their function ?

  prevents airways from collapsing when air pressure drops while breathing in.
• how are alveoli adapted for efficient gas exchange?

  the alveolar ephithelium is one cell thick which creates a short diffusion pathway for gas exchange
• in humans the trachea and bronchi are lined with cilia. how does this adaptation support their function?

  cilia move mucus towards the throat
• where are goblet cells found and what is their function ?

  goblet cells are found in the ciliated epithelium lining the air passages in the lungs. they secrete mucus which traps inhaled dust and microorganisms
• what is the function of the elastic fibres found in the walls of the bronchi and bronchioles?

  to allow the airways to stretch when inhaling and help to squeeze air out of the lungs when exhaling via a feature called elastic recoil
• what is the function of the smooth muscle fibres found in the walls of the bronchioles ?

  it allows the bronchioles to dilate and contract to regulate the amount of air flowing to the lungs
• which muscles are responsible for raising the rib cage during ventilation ?

  the external intercostal muscles
• which muscles are responsible for lowering the rib cage during forced exhalation ?

  the internal intercostal muscles
• what volume and pressure changes occur in the thorax during inspiration ?

  Volume increases, pressure decreases.
• what volume and pressure changes occur in the thorax during expiration ?

  Decreased volume, increased pressure.
• what is the meaning of the term vital capacity ?

  The maximum amount of air a person can exhale after taking a deep breath.
• what is the meaning of the term tidal volume ?

  The amount of air inhaled or exhaled during normal breathing.
• what is the meaning of the term inspiratory reserve volume ?

  The additional volume of air that can be inhaled after a normal inhalation.
• what is the meaning of the term expiratory reserve volume ?

  The extra amount of air that can be exhaled after a normal exhalation.
• what is the meaning of the term residual volume ?

  The amount of air remaining in the lungs after maximum exhalation.
• what is the name of the organs of gas exchange in fish ?

  gills
• what is the name of the bony flap which covers the gill cavity in fish ?

  Operculum
• ventilation in fish is achieved by the movement of which three structures ?

  the mouth, the floor of the buccal cavity and the operculum
• what is the name of the component of the gills across which gas exchange takes place ?

  Lamellae
• define counter current flow ?

  when two materials flow in opposite directions to maintain a concentration gradient
• insect tracheoles have thin walls. how does this increase the efficiency of gas exchange ?

  Short diffusion distance.
• insects have a large number of highly branched tracheoles. How does this increase the efficiency of gas exchange ?

  in means there is a short diffusion distance to cells and a large surface area for gas exchange.
• Insect tracheae provide tubes full of air. How does this increase the efficiency of gas exchange ?

  gases diffuse quickly into tissues
• Fluid in the ends of tracheoles moves out into tissues during exercise. How does this increase the efficiency of gas exchange ?

  The final diffusion pathway is gas rather than liquid, so diffusion to the gas exchange surface is faster and surface area for gas exchange is larger.
• Insects can use their muscles to move air through tracheae. How does this increase the efficiency of gas exchange ?

  maintains a steep diffusion gradient for oxygen and carbon dioxide
• what are the features of an open circulatory system ?

  there are few vessels and the transport medium is pumped into a open body cavity
• what are the features of a single closed circulatory system ?

  blood passes through the heart once for each circuit of the body. blood is pumped around the body in vessels so it does not have direct contact with cells
• what are the features of a double closed circulatory system ?

  blood passes through the heart twice for each circulation of the body. blood is pumped in vessels so it does not have direct contact with cells