Exchange and transport systems

• two adaptations for gas exchange

  • have a large surface area
  • they are thin - provides them with a short diffusion pathway
  • maintains a steep concentration gradient of gases across the exchange surface
• fish gas exchange - counter current system
• fishes gas exchange

  1. water containing oxygen enters the fish through its mouth and passes out through the gills
  2. each gill is made up of gill filaments which provide a larger surface area for gas exchange
  3. the gill filaments are covered in lamellae which also increase the surface area for gas exchange
  4. the lamellae have lots of capillaries and a thin surface layer to speed up diffusion
  5. blood flows through the lamellae in one direction and the water flows in the opposite. it maintains a large concentration gradient between water and blood.
• label the lamella and gill filaments

  A) gill filaments

  B) lamella

  C) artery

  D) artery

  
• label the counter current diagram

  A) blood flow

  B) water flow

  C) blood

  D) high oxygen concentration

  E) blood

  F) low oxygen concentration

  G) water

  H) low oxygen concentration

  I) water

  J) high

  
• insect gas exchange

  1. air moves into the trachea through spiracles
  2. oxygen travels down the concentration gradient towards the cells
  3. the trachea branch of into tracheoles which have thin permeable walls and go to individual cells. this means that oxygen diffuses directly into the respiring cells
  4. carbon dioxide from the cells moves down its own concentration gradient towards the spiracles to be released into the atmosphere
  5. insects use rhythmic abdominal movements to move air in and out of the spiracles
• label the areas of the insects gas exchange

  A) tracheae

  B) tracheoles

  C) spiracle

  D) tracheal tubes

  E) tracheole

  F) tracheal tubes

  G) respiring cells

  
• plants exchange gases at mesophyll cells

  1. gases move in and out through special pores in the epidermis called stomata
  2. the stomata can open to allow exchange of gases and close if the plant is loosing to much water. Guard cells control the opening and closing of stomata
• label the diagram of the leaf

  A) waxy cuticle

  B) upper epidermis cell

  C) palisade mesophyll cell

  D) xylem

  E) phloem

  F) spongy mesophyll cells

  G) waxy cuticle

  H) lower epidermis cell

  I) guard cells

  J) stoma

  
• losing too much water

  • insects - close spiracles and have a waterproof cuticle and tiny hairs which reduce evaporation
  • plants - close the stomata
• gas exchange in humans

  1. air enters the trachea
  2. the trachea splits into two bronchi - one bronchus leading to each lung
  3. each bronchus then branches into bronchioles
  4. the bronchioles end with alveoli
  5. the ribcage, intercostal muscles and diaphragm all work together to move air in and out
• label the human gas exchange system

  A) trachea

  B) ribcage

  C) lung

  D) diaphragm

  E) intercostal muscles

  F) bronchus

  G) bronchiole

  H) alveoli

  
• xerophytic plant adaptations

  • stomata sunk in pits that trap air reducing the concentration gradient of water between the leaf and air. this reduces the amount of water diffusing out of the leaf and evaporating away
  • a layer of hairs on the epidermis which trap moisture
  • curled leaves with the stomata inside protecting them from wind
  • a reduced number of stomata so less places for the water to escape
  • waxy waterproof cuticles on leaves and stems to reduce evapouration
• describe the process of inspiration

  1. the external intercostal and diaphragm muscles contract and internal intercostal muscle relax
  2. this causes the ribcage to move upwards and outwards and the diaphragm flatten, increasing the volume of the thorax cavity
  3. as the volume in the thorax cavity increases the pressure decreases to below atmospheric pressure
  4. air will always flow from and area of higher pressure to an area with lower pressure
  5. inspiration is an active process so requires energy
• label the diagram of inspiration

  A) increases

  B) decreases

  C) contract

  D) downwards

  E) flatten

  F) external

  G) outwards

  H) upwards

  
• describe the process of expiration

  1. the external intercostal and diaphragm muscles relax
  2. the ribcage moves downwards and inwards and the diaphragm becomes curved
  3. the volume of the thorax cavity decreases causing the air pressure to increase to above atmospheric pressure
  4. air is pushed down the concentration gradient and out of the lungs
  5. normal expiration is a passive process so does not require energy
• alveolar epithelium - single layer of thin and flat cells
• alveoli in the lungs: there is a large number of them so creates a large surface area for exchanging oxygen and carbon dioxide and are surrounded by capillaries
• how is carbon dioxide removed from the body?

  • oxygen diffuses out of the alveoli across the alveolar epithelium and the capillary endothelium and into the haemoglobin in the blood
  • carbon dioxide diffuses into the alveoli from the blood and is breathed out
• alveoli adaptations for gas exchange

  • a thin exchange surface - the alveolar epithelium is only one cell thick this means there is a short diffusion pathway
  • a large surface area - the large number of alveoli means there is a large surface area for gas exchange