exchange surfaces and breathing

Question 1

list some features of effective exchange surfaces along with some examples

Answer 1

• increased surface area -
• thin layers
• good blood supply
• ventilation to maintain diffusion gradient

Question 2

describe how increased surface area is a feature

Answer 2

provides the area needed for exchange and overcomes the limitation of SA:V ratio of larger organisms
EG, root hair cells in plants and villi of the small intestine

Question 3

describe how thin layers is a feature

Answer 3

• these mean the distances that substances have to diffuse are short
• making the process fast and efficient
• examples include in the alveoli in the lungs and the vili of the small intestine

Question 4

describe how a good blood supply is a feature

Answer 4

• the steeper the concentration gradient, the faster the diffusion takes place
• having a good blood supply ensures substances are constantly delivered to and removed from the exchange surface
• this maintains a steep concentration gradient for diffusion
• EG, alveoli of the lungs, gills of a fish and villi of a small intestine

Question 5

describe how ventilation is a feature

Answer 5

• helps maintain concentration gradients and makes the process more efficient
• alveoli and gills of a fish where ventilation means a flow of water carrying dissolved gases

Question 6

what are the features nasal cavity ?

Answer 6

• large surface area with a good supply which warms the air to body temperature
• a hairy lining which secrets mucus to trap dust and bacteria protecting delicate lung tissue from irritation and infection
• moist surfaces, which increase the humidity of the incoming air reducing evaporation from the exchange surfaces

Question 7

what is the trachea and what happens in it.

Answer 7

• it is main airway carrying clean, warm, moist air from the nose down into the chest
• it is supported by in complete rings of strong flexible cartilage which stop the trachea from collapsing
• the trachea and its branches are lined with a ciliated epithelium, with goblet cells between and below the epithelial cells goblet cells secrete mucus onto the lining of the trachea to trap dust and microorganisms away from the lungs

Question 8

describe the bronchus

Answer 8

• in the chest cavity the trachea divides to form the left bronchus leading to the left lung and the right bronchus leading to the right lung
  they are similar in structure to the trachea with the supporting rings of cartilage but smaller

Question 9

describe bronchioles

Answer 9

• in the lungs the bronchi divide to from many small bronchioles , have no cartilage
• the walls of the bronchioles contain smooth muscle
• when the smooth muscle contracts the bronchiole constrict and when it relaxes it dilates
  this changes the amount of air reaching the lungs.
  bronchioles are lined with a layer of epithelium.

Question 10

describe alveoli

Answer 10

• they are tiny air sacs which are the main gas exchange surfaces of the body.
• each alveolus has a diameter of 200-300Um and consists of thin flattened epithelium cells and collegen and elastic fibres
• these elastic tissues allow the alveoli tissues allow the alveoli to stretch as air is drawn in.
  when they return to their resting size they help squeeze the air out
  this is known as elastic recoil

Question 11

what are the adaptations of the alveoli for effective gaseous exchange

Answer 11

• large surface area
• thin layers - one cell thick
• good blood supply
• good ventilation

Question 12

describe and explain inspiration ( inhalation)

Answer 12

1. ) diaphragm contracts flattening and lowering
2. ) external inter-coastal muscles contract moving the ribs upwards and outwards
3. ) the volume of the thorax increases so the pressure in the thorax is reduced
4. ) it is now lower than the pressure of the atmospheric air
5. ) so air is drawn through the nasal passages

Question 13

describe and explain expiration ( exhalation)

Answer 13

1. ) diaphragm relax so it moves up into its resting shape
2. ) external intercoastal muscles relax so the ribs move down and inwards under gravity
3. ) the volume is decreased of the thorax
4. ) pressure inside the thorax is greater than the pressure of the atmospheric air so air moves out until pressure inside and out is equal

Question 14

how do you measure the capacity of the lungs

Answer 14

• a peak flow meter is a simple device that measures the rate at which air can be expelled from the lungs
• people who have asthma use these to see how there lungs are
• a spirometer is a commonly used to measure different aspects of the lung volume or to investigate breathing patterns
• there are many different forms of the spirometer but they all use the principle
• vitalographs are more sophisticated versais of the peak flow meter
• the patient being tested breathes out quickly as they can through a mouth price and the instrument produces a graph if the amount of air they breathe and how quickly it is breathed out

Question 15

what are the components of the lung volume

Answer 15

1. ) tidal volume - volume of air that moves into and out of the lungs with each resting breath
2. ) vital capacity- volume of air that can be exhaled when the deepest possible intake of breath is followed by the strongest possible exhalation
3. ) residual volume - volume of air that is left in your lung when you have exhaled as hard as possible
4. ) inspiratory reserve volume - maximum volume of air you can breath in over
5. ) expiratory reserve volume - extra amount of volume you can force out of your lungs over and above normal tidal volume
6. ) total lung capacity - sum of the vital capacity and residual volume