3.1.1 Exchange surfaces Flashcards
1
Q
Explain the need for specialised exchange surfaces in multicellular organisms
A
Specialised exchanged surfaces are needed in multicellular organisms because:
* Metabolic activity is much higher than single celled organisms as organisms are larger
* Smaller Sa:V ratio as they are bigger organisms
* So less sa for diffusion of nutrients
* And a greater diffusion distance due to a greater volume
Demand is not being met through diffusion alone as it is too great
2
Q
Surface area of a sphere equation
A
Sa = 4 pi r^2
3
Q
Volume of a sphere equation
A
V= 4/3 pi r^3
4
Q
The bigger the organism……..
A
the smaller the sa:v ratio
5
Q
Name the features of a good exchange surface
A
- Large surface area
- Thin layers
- Good Blood supply
- Ventilation
6
Q
Why does a large surface area make for a good exchange surface?
A
- Provides area for exchange
- Overcomes Sa:V ratio of larger organisms
- Eg, root hair cells, villi
7
Q
Why do thin layes make for a good exchange surface?
A
- Shorter diffusion distance
- Increases the speed and efficiency
- Examples: alveoli, villi
(instead of saying efficiency in EQ state what the function of the surface is actually eg, alveoli= increasing the speed it moves O2 in and CO2 out etc)
8
Q
Why does a good blood supply make for a good exchange surface?
A
- Steeper concentration gradient
- Faster diffusion
- Substances are constantly delivered and removed from surface
- Examples: alveoli, gills, villi
9
Q
Why does good ventillation (gases) make for a good exchange surface?
A
- Maintains concentration gradient
- Makes process more efficient (specify the process)
- Example: Fish gills- ventillation means a constant flow of dissolved gases in water
- Example: Villi
10
Q
Why do mammals need a gaseous exchange system?
A
- They are relatively big with a small SA:V ratio and a large volume of cells
- High Metabolic rate
- Because they are active and maintain their body temp independent of the environment
- So, need lots of oxygen for cellular respiration
- And, produce CO2 which needs removed
11
Q
Important features of the nasal cavity
A
- Large SA with good blood supply which warms the air to body temperature
- Hairy lining which secretes mucus to trap dust and bacteria (protecting lung tissue from irritation and infection)
- Moist surfaces which increases humidity of incoming air, reducing evaporation from exchange surfaces
12
Q
Trachea function (summary)
A
Tube which carries air into lungs, branches into two bronchi
13
Q
Trachea tissues related to function
A
- Supported by C-shaped rings of cartillage preventing collapse during inhalation
- C-shaped to allow passage of food down oesophagus
- Lined with ciliated epthilium
- Mucus is released by goblet cells
- Mucus traps pathogens
- Cilia waft mucus to top of airway
- Contain smooth muscle and elastic fibres
14
Q
Bronchi function (summary)
A
Two tubes carry air into left and right lung which branches into bronchioles
15
Q
Bronchi structure related to function
A
- Narrower than trachea
- Full rings of cartillage to prevent collapse during inhalation
- Lined with ciliated epithelium calls
- Goblet cells release mucus
- Mucus is wafted by cilia away from bronchioles and alveoli
- Contains smooth muscle and elastic fibres
16
Q
Bronchioles function (summary)
A
Many tubules carrying air and the smallest tubules terminate into alveoli
17
Q
Bronchioles structure related to function
A
- Larger tubes contain cartillage but small tubes don’t
- Wall comprised (mainly) of smooth muscle and elastic fibres
- Smooth muscle contracts to constrict airways
- When muscle stops contracting, elastic fibres recoil to return bronchioles to original diameter (dilated)
- Also lined with ciliated epithelium and goblet cells
18
Q
Alveoli function (summarised)
A
Air sacs, site of gaseous exchange
19
Q
Alveoli structure related to function
A
- Composed of squamous epithelium which is one cell thick
- So, very short diffusion distamce
- Contain elastic fibres
- These stretch when inhaling and recoil to push air out when exhaling
- Also contains collagen
20
Q
Adaptations of alveoli for effective gas exchange
A
- Large surface area
- Thin layers- alveoli + capillaries are one squamous epithelial cell thick so diffusion distance between air in alveolus and blood in capillary are short
- Good blood supply- constant flow of blood through capillaries brings carbon dioxide and carries off oxygen, maintaining a steep conc gradient
- Good ventillation- breathing moves air in and out of alveoli mainting steep diffusion rate between blood and air
21
Q
Describe inspiration/inhalation in mammals
A
- External intercostal muscles contract moving the ribcage upwards and outwardss
- Diaphragm muscle contracts and moves downwards
- Volume of the thorax is increased by these 2 actions
- Pressure in the chest therefore decreases
- Pressure in thorax is now lower than pressure outside so air is drawn into lungs
22
Q
Describe expiration/exhalation
A
- External intercostal muscles relax so the rib cage falls under its own weight due to gravity
- Diaphragm muscle relaxes and moves upwards
- Volume inside the thorax/chest cavity decreases due to these 2 actions
- Pressure inside chest therefore increases
- So, air moves out of lungs as pressure inside thorax is greater than outside
23
Q
Explain how the lungs are specifically adapted to gas exchange
A
- Pulmonary vein continually removes oxygenated blood
- Pulmonary artery bring deoxygenated blood to the lungs
- Concentration gradient is maintained
- Squamous epithelium cells in alveoli are flattened so diffusion path is short
- RBC carry oxyegn in haemoglobin
- Oxygen moves into blood by diffusion down conc gradient
- Carbon dioxide moves out of alveoli by diffusion down conc gradient
- Frequent ventillation keeps oxygen high and carbon dioxide low
24
Q
Define tidal volume
A
Volume of air that moves in OR out in each resting breath
25
Define vital capacity
The volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest breath in
26
Define inspiratory reserve volume
Maximum volume breathed in over and above normal tidal
27
Expiratory reserve volume
The extra air that can be forced out of the lungs over the normal tidal volume breathed out
28
Residual volume
Volume of air left in the lungs when you have exhaled as hard as possible. Cannot be directly measured
29
Breathing rate
Number of breaths per miniute
30
Ventilation rate
Tidal volume x breathing rate (min^-1)
31
Oxygen uptake
The volume of oxygen absorbed by the blood. It is assumed that this is equal to the volume of carbon dioxide absorbed by the soda lime in a spirometer
32
Describe the relationship between tidal volume, breathing rate and oxygen uptake
As breathing rate increases, oxygen uptake increases because more oxygen is being breathed in. During excercise tidal volume increases as does the depth of breathing and the rate of breathing.
Ventillation rate = breathing rate x tidal volume
33
34
What are tracheae + how are they adapted?
* Tracheae are air filled tubes branching throughout the body
* Reinforced with chitin to prevent collapse
* There are multiple throughout the body so the SA is higher
35
What are tracheoles and how are they adapted?
* **Tracheoles** are fine **branches** of tracheae that **deliver gases** to cells
* Penetrate **directly into tissues** to reduce the **diffusion distance** of gases
* Have **thin** walls to reduce the **diffusion distance** of gases
* Highly **branched** to maximise SA
* **Not** reinforced with **chitin** to allow **gas exchange** to occur
* Fluid at ends of tracheoles (**tracheal fluid**) so all oxygen can **dissolve** and aid **diffusion** and **reduce water loss**
36
Describe how gas exchange occurs in insects
1. Air enters the tracheal system through **open spiracles.**
2. Air moves into larger tracheae and **diffuses** into smaller tracheoles.
3. **Tracheoles** **branch** throughout the body, transporting air directly to cells.
4. **Oxygen dissolves** in water in **tracheal fluid** and **diffuses** down its concentration gradient from **tracheoles** into body cells.
5. **Carbon dioxide diffuses** down its concentration gradient **out** of **body cells** into the **tracheoles**.
6. Air is then carried back to the **spiracles** **via the tracheae** and released from the body.
37
Ventilation mechanisms in insects
1.**More spiracles open** - This allows more oxygen to enter the tracheal system.
2. **Mechanical active ventilation** - This is when **muscles** around the tracheae **contract** and **relax**, changing the **volume** and **pressure** in the abdomen and squeezing the tracheae to **pump** air in and out of the spiracles.
3. **Movement of tracheal fluid out into tissues** - This **increases** the **diffusion** rate and **surface area** for gas exchange.
4. **Enlarged collapsible tracheae**, accessory sacs, and air reservoirs - These inflate or deflate to ventilate the tracheal system and can increase the volume of air moved through the system.
5. **Movement of wing muscles connected to sacs** - These pump air to ventilate the tracheal system.
6. **Vibration of thoracic muscles** - This pumps air to ventilate the tracheal system.
*3, 4 + 6 are named in spec*
38
Challenges of bony fish gas exchange
1. Water is denser and more viscous than air, resulting in slower diffusion of oxygen.
2. Water has less oxygen than air.
3. Bony fish are very active so have high oxygen demands.
39
Structure of the gills
1. Gills are covered by an operculum flap.
2. Gills consist of stacked filaments containing gill lamellae.
3. Gill lamellae are surrounded by extensive blood vessels.
40
Adaptations of the gills for efficient gas exchange
1. The lamellae provide a large surface area.
2. The lamellae membranes are thin to minimise diffusion distance.
3. The gills have a rich blood supply to maintain steep diffusion gradients.
4. The countercurrent flow of blood and water creates even steeper concentration gradients.
5. Overlapping filament tips increase resistance, slowing water flow over gills and allowing more time for gas exchange.
41
Explain how the countercurrent system works in bony fish
1. Blood and water flow over the lamellae in opposite directions.
2. This means that oxygen-rich blood meets water that is at its most oxygen rich when it first moves across the gills, maximising diffusion of oxygen into the blood.
3. Oxygen-poor blood returning from body tissues meets oxygen-reduced water that has had most of its oxygen removed, still allowing diffusion of oxygen into the blood.
4. This maintains a steep concentration gradient across the entire gill as oxygen conc in water is always higher than in blood of gill
42
Explain ventillation in bony fish
1. Fish opens its mouth which lowers floor of buccal cavity and increases the volume of the buccal cavity
2. This lowers pressure inside the buccal cavity which forces pressure into it
3. Thee operculum is shut
4. The fish closes ita mouth, reducing the volume in the buccal cavity
5. Pressure inside the buccal cavity increases, forcing water across gill filaments
6. The operculum opens and water flows out of gills
