3.1.H SA:Vol Ratio and Gas Exchange Humans

• What 3 features do our lungs have to increase the rate of diffusion? (Ficks Law)

  Large surface area to volume ratio.

  A thin surface which provides a short diffusion distance.

  A diffusion gradient.
• What is a squamous cell?

  A flattened cell
• What do our lungs have to increase the SA:V ratio? (3 things)

  Many alveoli.

  Many capillaries.

  A folded alveoli epithelium wall.
• What does our lung have to decrease diffusion distance? (3 things)

  The alveolar epithelium cells are squamous.

  Blood capillaries are close to the alveolar epithelium.

  The capillary epithelium/endothelium is one cell thick.
• What does our lung have to maintain a diffusion gradient? (2 things)

  Good circulation so that blood with a high O2 concentration is carried away, replacing it with blood with a low O2 concentration.

  Lung ventilation brings in air with a higher O2 concentration, removing air with a lower O2 concentration.
• "What happens when we breathe in? 5 ""stages"""

  External intercostal muscles contract while the internal relax.

  Ribcage lifts up and out.

  Diaphragm contracts and flattens.

  Volume of thorax increases so pressure decreases in the thoracic cavity.

  Air moves down a pressure gradient into the lungs
• What happens when we breathe out?

  Internal intercostal muscles contract while the external relax.

  Ribcage drops down and in.

  Diaphragm relaxes and lifts up.

  Volume of thorax decreases so pressure increases in thoracic cavity.

  Air moves down a pressure gradient out of the lungs.
• What is tidal volume?

  The volume of air taken in during each breath while resting
• What's the equation for ventilation (breathing rate)?

  60 seconds / Time taken for one breath = Breaths (min^-1)
• What is the equation for pulmonary ventilation?

  Pulmonary ventilation (dm^3 min^-1) = Tidal volume (dm^3) x Ventilation rate (min^-1)
• What is inspiratory reserve volume?

  The extra volume which can be breathed in during maximum inspiration
• What is expiratory reserve volume?

  The extra volume which can be breathed out during maximum expiration
• What is vital capacity

  The maximum volume which can be breathed in/out in one breath
• For exchange of materials to be effective should the SA:Vol ratio be large or small?

  Large
• Does SA:Vol ratio get bigger or smaller as an object gets bigger?

  It gets smaller
• Why do smaller organisms not require a specialised gas exchange system?

  Their surface area to volume ratio is large enough that they can meet their gas exchange needs by diffusion across their surface.
• Why do larger organisms require a specialised gas exchange system?

  They have a smaller surface area to volume ratio, so need a specialised gas exchange system to ensure rapid diffusion of gases.
• What is another factor that the SA:Vol ratio of an organism effects?

  Heat loss
• Why do smaller organisms have a larger respiration rate?

  They have a greater metabolic rate than larger organisms due to their small surface area to volume ratio so lose heat faster.
• What is ficks law?

  Diffusion rate = (surface area x difference in concentration gradient) ÷ length of diffusion pathway
• What five factors make a good exchange surface?

  Large surface area.

  Large concentration gradient (associated with an efficient transport system).

  Thin exchange surface (short diffusion pathway).

  Permeable.

  Moist (gases diffuse rapidly in solution).
• What is the trachea?

  The trachea is a tube like structure that carries air from the mouth to the lungs.
• What are the bronchi?

  The bronchi are after the trachea as it splits off into two bronchi as it enters the lungs, allowing air to go to the left or right lung.
• What are the bronchioles?

  The bronchioles are the smaller branches after the bronchi which supply the alveoli with air.
• What are the alveoli?

  The alveoli are the small sacks at the end of the bronchioles that act as the interface between the air and the lungs and the blood.
• How are the alveoli adapt to provide a large surface area?

  Their walls are folded.
• What helps the alveoli maintain a good concentration gradient?

  They have a very rich blood supply which circulates blood and combined with ventilation, helps to provide a large concentration gradient between the gases in the blood and the alveoli.
• Which vessel brings deoxygenated blood to the lungs from the heart.

  The pulmonary artery.
• Which vessel brings oxygenated blood from the lungs to the heart.

  The pulmonary vein.
• Describe the diffusion of gases in the lungs, starting with the blood that will be coming from the heart. [Too many marks]

  Deoxygenated blood from pulmonary artery = low concentration of O2 and high conc. of CO2, compared with the air inside the alveoli. Blood reaches the capillaries surrounding the alveo, O2 diffuses into blood through the squamous epithelial membrane, from a high to a low O2 conc.. At the same time CO2 in the blood moves from the blood into the alveoli, conc. of CO2 in the blood from the pulmonary artery is greater than that in the inhaled air in the alveoli. This all occurs via diffusion, blood is circulated from the lungs to the heart via heart contractions to be circulated around the body. Tgis circulation of blood and air maintains a conc. gradient at the alveolar epithelium, to ensure efficient diffusion and avoid equilibrium.
• How can the pulmonary ventilation rate be changed?

  By altering either the ventilation rate or the tidal volume or both.
• What is pulmonary ventilation?

  The amount of air exchanged in one breathing cycle.
• Describe the condition fibrosis.

  It causes damage to and scars the lung epithelium. This results in the deposition of fibrous tissue in the lung epithelium.
• What 2 effects can the scarring of the lung epithelium by fibrosis cause?

  A reduced rate of diffusion (longer diffusion pathway and less permeable). Reduced elasticity of the lungs, therefore breathing out if not as efficient.
• What can cause asthma to trigger and give examples?

  Asthma can be triggered by an allergic reaction. This may be due to; pollen, air pollution, dust, infection, or stress.
• What happens during an asthma attack?

  The effected area is infiltrated by a type of white blood cell called macrophage. These white blood cells release inflammatory chemicals such as histamine. The inflammation causes reduced air flow through the bronchioles.
• Describe the condition of emphysema. What causes it? What happens? Link to SA

  Emphysema is caused by exposure to irritants such as excessive dust and smoking. The elastic tissue becomes damaged and the elastic tissue cannot recoil as normal and remains permanently stretched. The alveolar wall starts to breakdown, reducing surface area for diffusion and the alveoli may start to fill with fluid also reducing surface area.
• Why do surfaces for gas exchange also have to consider water loss along with gas exchange?

  The most effective surface for gas exchange is the same for evaporation, which is a large, thin and permeable area. This leaves room for the potential of fatal dehydration.
• Fill in the following diagram:

  A) Cartilage ring

  B) Trachea

  C) Ribs

  D) Heart

  E) Bronchiole

  F) Diaphragm

  G) Alveoli

  H) Lung

  I) External Intercostal Muscle

  J) Internal Intercostal Muscle

  K) Bronchus

  
• Fill in the blank:

  A) Alveolar Air sack

  B) Epithelium

  C) Endothelium

  D) Capillary blood vessel