Exchange surfaces and Breathing Flashcards
Why is there a need for exchange surfaces?
- Diffusion alone can not meet the oxygen demands of a multicellular organism
- So we need lots of exchange of O2 and CO2
What are the features of an effective exchange system?
- Increased SA:V (more particles can diffuse at once)
- Thin layer ( reduces diffusion distance)
- Good blood supply (Maintaining a steep concentration gradient)
- Good ventilation (flow of water / air)
What happens to air when it enters through the nasal cavity?
- Becomes warmer (close to body temp)
- Traps dust / bacteria via mucus
- increases humidity of the air
What is the role of cartilage in the trachea?
- stops the trachea and bronchi from collapsing (provides structure to the trachea and bronchi)
- incomplete cartilage rings so that food can pass easily down the oesophagus
What is the function of the ciliated epithelium?
- found in the trachea
- waft mucus produced by the goblet cells
- waft dirt/microorganisms away from the lungs
- most of it goes into the throat where it is swallowed
What are the effects of cigarettes on the cillia?
-stop the beating of the cilia
What is the function of the goblet cells?
- secrete mucus onto the lining of the trachea
- this is to trap dust and microorganisms
What is the function of smooth muscle cells?
-to constrict the bronchioles
What is the function of elastic fibres?
- allow the alveoli to stretch as air is drawn in
- also when recoiling help squeeze air out
- helps with the elastic recoil of the lungs
Where can gaseous exchange happen?
- bronchioles & alveoli
- through flattened (pavement cells)
Inspiration
- Diaphragm contracts and flattens
- External Intercostal muscles contract moving the ribcage up and out
- this increases the thoracic volume
- therefore decreasing thoracic pressure which is now lower than the external pressure
- This draws air in through the nasal cavity the trachea bronchi bronchioles and into the alveoli for gas exchange
- Until the difference in pressure is equal
Expiration
- Diaphragm relaxes and moves up
- External intercostal muscles relax moving the ribcage down and in
- This decreases thoracic volume
- This increases thoracic pressure compared to the external pressure
- Air moves out of the lungs
- Until the difference in pressure is equal
When do the internal intercostal muscles contract?
-During forced exhalation
What is used to measure lung capacity?
- Spirometer (Need to know)
- Peak flow meter
Tidal volume
-Volume of air that moves in and out of the lungs
Vital capacity
-The volume of air that can be breathed in after the strongest possible exhalation
Breathing rate
-number of breaths per minute
ventilation rate
tidal volume * breathing rate
Why is a nose clip used?
- to keep the volume of air breathed by the patient the same
Why is there soda lime?
- to absorb the CO2 from the subject
How does air enter insects?
-through spiracles in the thorax and the abdomen of insects
Why does the spiracle need to be closed most of the time?
- when the insect is at rest to prevent water loss
- spiracles are controlled by sphincters
What tube carries the air into the body?
-tracheae
What makes the tracheae impermeable to gasses?
-chitin spirals
What gives large surface area for gas exchange in insects?
-tracheoles
Explain the gaseous exchange in insects
- air enters through spiracles
- Abdominal movement pushing oxygen through tracheae
- air goes through the tracheae into the tracheoles where gaseous exchange takes place
- O2 dissolves into the water lining the tracheoles
- tracheal fluid limits the penetration of gases
- When the insect is active it produces lactic acid due to anaerobic respiration
- This draws the tracheal fluid out of tracheoles
- increasing SA and more gas exchange
Ventilation in bony fish: (how does water enter the buccal cavity?)
- Mouth opens and buccal cavity expands (Lowered)
- This increases Buccal Volume and decreases Buccal pressure
- Water moves into the buccal cavity down a pressure gradient
Ventilation in bony fish: (how does water travel from the buccal cavity to the opercular cavity?)
- Floor of the buccal cavity moves up Opercular cavity expands (valves shut) (at the same time as the buccal cavity being moved up)
- This increases the opercular volume and decreases opercular pressure while the pressure in the buccal cavity increases
- Therefore Water moves from the buccal cavity to the opercular cavity OVER THE GILLS down a pressure gradient
Ventilation in bony fish: (how does water leave the opercular cavity?)
- Buccal cavity and opercular cavity both constrict
- This decreases buccal and opercular volume increasing the pressure on both the buccal and opercular cavity
- Water LEAVES the OPERCULAR cavity to outside down a pressure gradient
Effective gas exchange in water
- tips of adjacent gill filaments overlap slowing water down
- Countercurrent exchange system
Explain the countercurrent exchange system in fish
- blood in the gills and water flow in opposite directions
- This MAINTAINS a concentration gradient for oxygen to diffuse across
- so a Much higher oxygen saturation in the blood is achieved
