3.1 Exchange surfaces and breathing Flashcards
1
Q
What is surface area to volume ratio?
A
The surface area of an organism divided by its volume, expressed as a ratio.
2
Q
What are some examples of substances organisms need to survive?
A
- Oxygen
- Glucose
3
Q
What are some examples of what animals need to get rid of to survive?
A
- Urea
- Lactic acid
4
Q
What factors effect the need for an exchange system?
A
- size
- surface area to volume ratio
- level of activity
5
Q
Why don’t some organisms need exchange systems?
A
In very small organisms, such as single-celled organisms, all the cytoplasm is very close to the environment in which they live. Diffusion will supply enough oxygen and nutrients to keep the cell alive and active.
6
Q
Why do some organisms need exchange systems?
A
Multicellular organisms need exchange systems because they have multiple layers of cells so that oxygen or nutrients diffusing in from the outside have a longer diffusion pathway- diffusion is too slow to enable a sufficient supply to the innermost cells.
7
Q
Is the surface area to volume ration large or small to small organisms?
A
They have a large surface area to volume ratio- meaning that there surface area is large enough to supply all their cells with sufficient oxygen.
8
Q
Is the surface area to volume ration large or small to larger organisms?
A
Larger organisms have a small surface area to volume ratio.
This is because they have a larger surface area but also a large volume- as volume rises more quickly than surface area, when u divide surface area by volume, you get a small number.
9
Q
How have some organisms adapted to have a larger surface area to volume ratio?
A
Some organisms have adapted by increasing their surface area by adopting a different shape. e.g. a flat worm has a very thin, flat body.
10
Q
How does level or activity effect an organisms need for exchange systems?
A
Metabolic activity uses energy from food and requires oxygen to release the energy in aerobic respiration. The cells of an active organism need for good supplies of nutrients to supply the energy of movement. The need for energy is increased in those animals, such as mammals, that keep themselves warm.
11
Q
What are the features of a good exchange system?
A
- Large surface area
- Thin barrier to reduce the diffusion distance
- Good blood supply
12
Q
Why does having a large surface area make a good exchange system? How can it be achieved? Example of where this can be seen?
A
Provides more space for molecules to pass through. Often achieved by folding the walls and membranes involved. Root hair cells in plants is a good example of having a large surface area.
13
Q
Why does having a thin barrier make a good exchange system? Example of where this can be seen?
A
Reduces the diffusion distance- and that barrier must be permeable to the substances being exchanged. This can be seen well in the alveoli of the lungs.
14
Q
Why does having a good blood supply make a good exchange system? Example of where this can be seen?
A
This can bring fresh supplies of the molecule on one side, keeping the concentration gradient high, or it may remove molecules from the demand side to keep the concentration low. This is important to maintain a steep concentration gradient so that diffusion can occur rapidly. The gills on a fish is a good example.
15
Q
Why does some exchange systems being moist make them work better?
A
Gases dissolve in the moisture helping them to pass across the gas exchange surface.
16
Q
Define alveoli.
A
Tiny folds of the lung epithelium to increase the surface area.
17
Q
Define bronchi and bronchioles.
A
Smaller airways leading into the lungs.
18
Q
What is a diaphragm?
A
A layer of muscle beneath the lungs.
19
Q
What are intercostal muscles?
A
Muscles between the ribs. Contraction of the external intercostal muscles raises the ribcage.
20
Q
What is the trachea?
A
The main airway leading back from the mouth to the lungs.
21
Q
Define ventilation.
A
The refreshing of air in the lungs, so that there is a higher oxygen concentration than in the blood, and a lower carbon dioxide concentration.
22
Q
What does the gaseous exchange system in mammals consist of?
A
The lungs and associated airways that carry air into and out of the lungs.
- Lungs
- Trachea
- Bronchi
- Bronchioles
- Alveoli
23
Q
What are the ribs held together by?
A
Intercostal muscles.
24
Q
What produce breathing movements in the lungs?
A
The intercostal muscles and the diaphragm.
25
How does gaseous exchange occur in the lungs?
Gases pass by **diffusion** through the thin walls of the alveoli. Oxygen passes from the **air in the alveoli to the blood in the capillaries**. Carbon dioxide passes from the blood to the air in the alveoli. The lungs **must maintain a steep concentration gradient** in each direction in order to ensure that diffusion can continue.
26
how are the lungs adapted for gaseous exchange?
* Large surface area
* Barrier to exchange is permeable to oxygen and carbon dioxide
* Thin barrier
* Good blood supply
* Ventilation
27
How do the lungs have a large surface area?
Individual **alveoli** are very small however, they are so **numerous** that the total surface area is much larger than that of our skin.
28
Why are the alveoli lined by a thin layer of moisture?
They are lined by a thin layer of moisture, which evaporates and is lost when we breath out.
The lungs produce a surfactant that coats the internal surface of the alveoli to **reduce the cohesive forces** between **water** molecules, as these forces tend to **make the alveoli collapse**.
29
How do the lungs have an exchange barrier that is permeable to oxygen and carbon dioxide?
The barrier is composed of the wall of the blood capillary
The cells and their plasma membranes readily allow the diffusion of oxygen and carbon dioxide, as the molecules are **small and nonpolar**.
30
How do the lungs have a thin barrier to reduce the diffusion distance?
* Alveolus wall is one cell thick
* Capillary wall is one cell thick
* Both walls consist of squamous cells
* Capillaries are in close contact with the alveolus walls
* Capillaries are narrow so red blood cells are squeezed against capillary walls- making them closer to the air in the alveoli and reducing their rate of flow.
So total barrier to diffusion is only 2 flattened cells, and is less than 1um thick.
31
How do the lungs have a good blood supply?
Blood system transports **carbon dioxide from the tissues to the lungs**. This ensures that the concentration in the blood than in the air in the alveoli. Therefore, carbon dioxide diffuses into the alveoli.
Blood also transported **oxygen away from the lungs**. This ensures that the **concentration** of oxygen in the blood is lower than that in the alveoli- so that the oxygen diffuses into the blood.
32
What does ventilation ensure?
* The concentration of oxygen in the air of the alveolus remains higher than that in the blood.
* The concentration of carbon dioxide in the alveoli remains lower than that in the blood.
33
What words do we use for ‘breathing in’?
Inspiration/ Inhalation
34
What words do we use for ‘breathing out’?
Expiration/ Exhalation
35
What is happening during inspiration and expiration?
Ventilation.
36
What happens during inspiration?
* The **diaphragm contacts** to move down and become flatter- displacing digestive organs downwards.
* **External intercostal muscles contract** to **raise the ribs**.
* The **volume** of the **chest cavity** is **increased**.
* The **pressure** in the **chest cavity** drops **below the atmospheric pressure**.
* **Air** is **moved into** the lungs.
37
What happens during expiration?
* The **diaphragm relaxes** and is pushed up by the displaced organs below.
* The **external intercostal muscles relax** and **ribs fall**; the internal intercostal muscles can contact to help push air out more forcefully- this only happens during exercise, coughing or sneezing.
* The **volume of chest cavity is decreased**.
* The **pressure in the lungs is increased** and rises above the pressure in the surrounding atmosphere.
* **Air is moved out** of the lungs.
38
What is cartilage?
A form of connective tissue.
39
What is ciliated epithelium?
A layer of cells that have many hair like extensions called cilia.
40
What are elastic fibres?
Protein fibres that can deform and then recoil to their original shape.
41
What are goblet cells?
Cells that secrete mucus.
42
What is smooth muscle?
Involuntary muscle that contracts without the need for continuous thought.
43
Describe what lung tissue looks like under a light microscope and why does it look like this?
Under the microscope, you will mostly see **alveoli**.
Alveoli are made of **squamous epithelium** and are surrounded by **blood capillaries**, so that the distance for diffusion is very short. The alveoli walls are so then, it **may not be possible to distinguish separate cells** under a light microscope.
44
What path does air take from the mouth to the bloodstream?
Trachea, bronchi, bronchioles, alvioli.
45
To be effective, what do the lungs must be adapted to be?
* Must be large enough to allow sufficient air to flow without obstruction.
* Be supported to prevent collapse when the air pressure is low during inspiration.
* Be flexible in order to allow movement.
46
How do ciliates epithelium and goblet cells work together in the airways?
The **airways are lines with ciliated epithelium**, which contributes to keeping the lungs healthy. **Goblet cells** in the epithelium **release mucus**, which **traps pathogens**. Then the cilia then **waft** the **mucus** up to the top of the airway, where it is **swallowed**.
47
What is the difference between the structure of the trachea and the bronchi?
The bronchi is narrower than the trachea.
48
What is similar between the trachea and bronchi?
The trachea and bronchi are **supported by rings of cartilage** which prevent collapse during inhalation. The rings of cartilage in the **trachea are C-shaped** rather than a complete ring which allows **flexibility** ans **space for food to pass down the oesophagus**.
49
Do bronchioles have cartilage?
Larger bronchioles may have some but smaller ones have none.
50
What is the structure of bronchioles?
* Bronchioles are much narrower than bronchi.
* The wall is comprised mostly of smooth muscle and elastic fibres.
* Smallest bronchioles end in clusters of alveoli.
* Larger ones may have cartilage, however, the smaller ones do not.
51
What does a trachea look like under a light microscope?
52
What happens in the lungs as a response to harmful substances in the air?
The **smooth muscles contact** which will **constrict the airway**. This will make the lumen narrower and restrict air flow to the alveoli.
53
What may cause the airways to contact?
**Harmful substances** in the air or as a result of an **allergic reaction.**
54
How does the contacted airway relex.
The contraction of the smooth muscle and control of the airway is **not a voluntary act** and once it has contacted, it cannot reverse the effect on it's own.
The smooth muscle is **elongated again** by the **elastic fibres**. When the muscle fibres contract, it **deforms the elastic fibres**- as they **relax**, the **elastic fibres recoil** to their original size and shape. This **dilates the airway**.
55
What produces mucous in the airways?
Goblet cells.
56
What is the meaning of the term ‘tissue’?
A collection of similar cells performing the same function.
57
What are the differences between squamous epithelium and ciliated epithelium?
Squamous epithelium is flat and the cells are very thin; ciliated epithelium is usually thicker (with columnar cells) and has numerous hair-like projections called cilia.
58
What tissues are found in the lungs?
* Squamous epithelium
* Ciliated epithelium
* Elastic fibres
* smooth muscle
* Cartilage
* Glandular tissue
* Blood
* Nervous tissue
* Connective tissue
59
Cartilage supports the airways by keeping them open, Without this support, what would cause the airways to collapse?
During inspiration, the pressure inside the gaseous exchange system drops below atmospheric pressure.
60
How do the cilia and mucous work together in the airways?
Mucus traps pathogens, cilia move mucus and trapped pathogens up to back of mouth, where they may be swallowed.
61
What does glandular tissue do?
The glandular tissue in the loose tissue produces mucous.
62
Why does smoking cause increased infections in the lungs?
Smoke paralyses the cilia. Therefore, mucus is not moved along and accumulates in the airway. Pathogens have ideal conditions to reproduce.
63
Lungs contain lots of small blood vessels, why is this important?
Blood carries carbon dioxide in towards alveoli and oxygen away, many small blood vessels give a larger surface area for gas exchange than fewer larger vessels.
64
How does the tissues in the lungs work together to produce a functioning organ?
Muscle of diaphragm causes ventilation, which refreshes the air in the alveoli; blood vessels and alveoli have squamous epithelium, which produces a short diffusion pathway; blood transports carbon dioxide in and oxygen away; elastic tissue allows dilation of airways and alveoli and recoils to return them to original size; smooth muscle can constrict the airway, which may protect lungs; ciliated epithelium keeps lungs free from infection.
65
Define breathing rate.
The number of breaths per minute.
66
Define oxygen uptake.
The volume of oxygen absorbed by the lungs in one minute
67
Define tidal volume.
The volume of air inhaled or exhaled in one breath, usually measured at rest.
68
What is a spirometer?
A devise that can measure the movement of air into and out of the lungs.
69
Define vital capacity.
The greatest volume of air that can be expelled by the lungs after taking the deepest breath possible.
70
What devise can be used to measure lung volume?
A spirometer.
71
What does a spirometer consist of and how does it work?
A spirometer consists of a **chamber of air** or medical-grade oxygen **floating** on a tank of **water**. During **inspiration**, air is drawn from the chamber so that the **lid moves down**. during **exhalation**, air returns to the chamber, **raising the lid**. These movements can be recorded on a **datalogger**.
72
What does a spirometer look like?
73
What precautions must be taken when using a spirometer?
* The subject should be **healthy** and, in particular, **free from asthma**.
* The **soda lime should be fresh** and functioning.
* There should be **no air leaks** in the apparatus, as this would give invalid or inaccurate results.
* The mouthpiece should be **sterilised**.
* The water chamber must **not** be **overfilled** (or water may enter the air tubes).
74
What happens to the carbon dioxide which is exhaled in a spirometer?
The carbon dioxide-rich air is passed through a chamber of soda lime, which absorbs the carbon dioxide.
75
Why must the carbon dioxide be absorbed in a spirometer?
To measure the consumption of oxygen.
76
What does total lung volume consist of?
Vital capacity and residual volume.
77
How can vital capacity measured?
Measured by taking a deep breath and expiring all the air possible from the lungs.
78
What does vital capacity depend upon?
* **Size** of the person (particularly their height)
* Their **age** and **gender**
* Their level of regular **exercise**
79
What usually is the value of vital capacity?
**2.5-5.0 dm3**. However, this may rise above in trained athletes.
80
What is the residual volume?
Residual volume is the volume of the air that remains in the lungs even after forced expiration. The air that remains in the airways and alveoli. This is approximately 1.5dm3.
81
What is the typical tidal volume?
**0.5 dm3**. This is usually enough to supply all the oxygen required at rest.
82
Why does the trace on the spirometer travel downwards?
The carbon dioxide is absorbed by the soda lime, so that the air in the chamber decreases.
83
How can we calculate the rate of oxygen uptake from a spirometer?
We can assume that the **volume of carbon dioxide** released and that **absorbed** by the soda lime **equals** the **volume of oxygen** **absorbed** by the **blood.** Therefore, measuring the **gradient** of the **decrease** in the **volume** enables us to **calculate the rate of oxygen uptake**.
84
What factors affect the bodies oxygen uptake?
* Breathing rate
* deeper breaths
85
During exersice, hoe does someones oxygen uptake increase?
During exercise, **intercostal muscles** function to **increase volume** of inspiration and expiration.
86
Why are we unable to exhale all the air out of our lungs?
Alveoli are held open by elastic fibres and airways are held open by cartilage – the space inside is filled by air. This is called the **residual volume**.
87
Define the buccal cavity.
A fishes mouth.
88
Define countercurrent flow.
Where two fluid flow in opposite directions.
89
Define filaments.
**Slender branches of tissue** that make up the **gill.** They are often called **primary lamellae**.
90
Define lamellae.
**Folds of the filament** to increase the surface area. They're also called gill plates or **secondary lamellae.**
91
Define the operculum.
A **bony flap that covers the gills** in bony fish.
92
Define a spiracle.
An **external opening** or pore that **allows air in** or out of the tracheae in insects.
93
Define tracheal fluid.
The **fluid** found at the **ends of the tracheoles** in the tracheal system.
94
What is the tracheal system.
A system of air-filled tubes in insects.
95
What do gills do?
Absorb oxygen dissolved in water and release carbon dioxide into the water.
96
How many pairs of gills does a typical bony fish have and where are they found?
**5 pairs** which are **covered** by a bony plate called the **operculum**.
97
What does each gill on a body fish consist of?
**Two rows of gill filaments** (primary lamellae) attached to a bony arch. The filaments are very thin, and their **surface is folded into many secondary lamellae** (or gill plates).
This provides a large surface area. **Blood capillaries** carry deoxygenated blood **close to the surface** of the secondary **lamellae** where exchange takes place.
98
Why are the lamellae good for gaseous exchange?
Provides a very large surface area.
99
what sort of flow does the water and blood have to each other in a bony fish?
A countercurrent flow.
100
How does a countercurrent flow work in a bony fish's gills?
Blood flows **along the gill arch and out along the filaments** to the secondary **lamellae**. The blood then flows through the **capillaries in the opposite direction to the flow of the water** over the lamellae. This lets oxygen rich water meet oxygen rich blood and oxygen poor water meet oxygen poor blood which **maintains a favourable concentration gradient**.
This arrangements creates a countercurrent flow that **absorbs the maximum amount of oxygen** from the water.
101
How do bony fish get water to go through their gills?
Bony fish can keep water flowing over the gills by using a **buccal-opercular pump**. The fish will **change the pressure** in its **buccal cavity**, coordinated with movements of the **operculum** to push water through it's lungs.
102
How does a bony fish change the pressure to force water through their lungs?
The floor of the mouth is **pushed downwards**, drawing water into the **buccal cavity**. The mouth closes and the floor is **raised again, pushing water** through the gills. As water is pushed from the buccal cavity, the **operculum moves outwards**. This movement **reduced the pressure** in the opercular cavity, helping water to move through the gills.
103
What sort of circulatory system does an insect have?
An open circulatory system.
104
Describe an insects circulatory system.
Insects have an **open circulatory system** in which the **body fluid acts as both blood and tissue fluid**. **Circulation is slow** and in affected by **body movements**.
105
What does an insects circulatory system made up of?
Insects posses an **air-filled tracheal system** which supplies air directly to the respiring tissues. Air enters the system via a pore in each segment, called a **spiracle**. The air is transported through a series of tubes called **tracheae**. These divide into smaller and smaller tubes, called **tracheoles**. The ends of the tracheoles are open and filled with fluid called tracheal fluid.
106
Where does gaseous exchange occur in an insect?
Gaseous exchange occurs **between the air in a tracheole and the tracheal fluid**. Some exchange can also occur across the **thin walls of the tracheoles**.
107
What is circulation affected by in insects?
Body movement.
108
What can an insect do to get more oxygen when it's tissues are active?
When tissues are active, the **tracheal fluid can be withdrawn into the body fluid** in order to **increase** the **surface area of the tracheole** wall **exposed** to **air**. This means more oxygen can be absorbed when the insect is active.
109
How can an insect expanding sections of their tracheal system and having flexible walls help to ventilate larger insects?
Sections of expanded tracheal systems **act as air sacs** which can be squeezed by the action of the **flight muscles**. **Repetitive expansion** and **contraction** of the sacs **ventilate** the tracheal system.
110
How can insects moving their wings increase ventilation of their circulatory system?
In some insects, movement of their wings **alter the volume of the thorax**. As the thorax volume decreases, air in the tracheal system is **put under pressure** and is pushed out of the tracheal system. When the thorax increases in volume, the **pressure decreases** and air is pushed into the tracheal system from the outside.
111
How can insects altering the volume of their abdomen increase ventilation of their circulatory system?
Some insects like locusts have adapted so they can alter the volume of their abdomen. These are **coordinated with opening and closing** valves in the **spiracles**. As the abdomen expands, spiracles at the front of the body open and air enters the tracheal system. As the abdomen reduced in volume, the spiracles at the rear end of the body and air can leave the tracheal system.
112
What 3 ways have larger insects adapted to aid ventilation of their tracheal system by movements of the body?
* Sections of the tracheal system are expanded.
* Movements of the wings alter the volume of the thorax.
* Alter the volume of their abdomen.
113
Why cannot fish survive out of water?
Gill collapses out of water, so surface area exposed to air is small – insufficient to allow enough gaseous exchange. Eventually the gills will dry out.
114
Why are there many filaments and lamellae in fish gills?
To increase the surface area for gaseous exchange.
115
Some sharks do not have an operculum and have lost the ability to pump water through there buccal cavity. Why would these sharks die if they stop moving?
Buccal pump and operculum flap pump water over the gills. If the fish is unable to pump water, then the flow will stop if fish stops moving. All the **oxygen in the water in the gills will be used up**.
116
Why do insects have a separate tracheal system instead of blood to transport oxygen around the body?
With an open circulation, an insect cannot easily direct the flow of blood to the tissues that need it most; the flow is also affected by body movements. Using **separate air-filled tubes** allows development of a **system** that can **bring more air to the tissues that need it**. If the insect relies on diffusion to some extent, the **oxygen can diffuse more quickly through air than through blood fluid**.
117
Why is tracheal fluid withdrawn when an insect is more active?
Oxygen can diffuse through the walls at the end of the tracheoles into the tissue fluid, withdrawing fluid from the end of the tube **increases the surface area over which exchange can occur**.
118
How the structure of an artery related to its function?
* **Smaller lumen** so blood travels at high pressure.
* **Thick walls** so can withstand pressure.
* **Elastic tissue**/elastic recoil allowing stretch.
* **Lined with smooth endothelium** which reduces friction.
* **No valves** so can travel at high pressure.
* **Circular cross section** so that the maximum blood volume can come into contact with minimum wall contact, reducing friction.
119
How is the wall of an artery different from that of a vein?
Arteries have no valves, thicker walls, more collagen and more muscle.
120
Why pressure in the capillaries much lower compared to the pressure in arteries?
* The distance from the heart is longer.
* Been through more friction.
121
Why is it important blood in the capillaries have a low pressure?
* Walls only one cell thick so if they were at high pressure, they would burst.
* Allows time for exchange.
122
Pressure in veins is very low, how is blood returned to the heart?
* Valves prevent backflow.
* Residual pressure.
* Gravity (from areas above the heart).
