exchange surfaces Flashcards
1
Q
What are exchange surfaces?
A
Surfaces over which materials are
exchanged from one area to another
2
Q
What is surface area to volume
ratio (SA:V)?
A
The surface area of an organism divided by its volume As size increases.. • Surface area increases • Volume increases, more quickly than surface area • Surface area to volume ratio decreases
2
Q
What is surface area to volume
ratio (SA:V)?
A
The surface area of an organism divided by its volume As size increases.. • Surface area increases • Volume increases, more quickly than surface area • Surface area to volume ratio decreases
3
Q
Why is diffusion alone enough
to supply single-celled
organisms?
A
• Single-celled organisms have low metabolic activity, so oxygen demands are carbon dioxide production of the cell are relatively low • They have a large surface area to volume ratio (SA:V)
4
Q
Why do multicellular organisms
require specialised exchange
surfaces?
A
• Small SA:V ratio • Distance is too far for effective diffusion to take place • Diffusion is too slow for the oxygen and nutrients to diffuse across the whole organism • Surface area is no longer large enough to supply the needs of the larger volume • Multicellular organisms are also metabolically active
5
Q
List the features of effective
exchange surfaces
A
• Increased surface area • Thin layers • Good blood supply • Ventilation to maintain diffusion gradient
6
Q
Why do exchange surfaces
have increased surface area?
A
Provides the area needed for exchange and overcomes the limitations of the SA:V ratio of larger organisms • e.g. root hair cells in plants, and villi in the small intestine
7
Q
Why do exchange surfaces
have thin layers?
A
These mean the distances substances have to diffuse are short, making the process fast and efficient • e.g. alveoli in the lungs, and villi of the small intestine
8
Q
Why do exchange surfaces
have good blood supply?
A
The steeper the concentration gradient, the faster 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 • e.g. the alveoli of the lungs, the gills of a fish, and the villi of the small intestine
9
Q
Why do exchange surfaces
have ventilation?
A
• For gases, a ventilation system helps maintain concentration gradients and makes the process more efficient • e.g. the alveoli, and gills of a fish where ventilation means a flow of water carrying dissolved gases
10
Q
Describe mammals
A
• Relatively big; small SA:V ratio and large volume of cells • High metabolic rate because they are active and maintain their body temperature • Therefore need lots of O2 for cellular respiration and produce CO2 which needs to be removed
11
Q
Describe the features of the
nasal cavity
A
• Large surface area with good blood supply which warms the air to body temperature • Hairy lining which secretes mucus to trap dust and bacteria • Moist surfaces which increase humidity of incoming air, reducing evaporation from the exchange surfaces
12
Q
What is the trachea?
A
The main airway, supported by
incomplete rings of cartilage, which
carries warm moist air down from
the nasal cavity into the chest
13
Q
Describe the function of
cartilage supporting the
trachea
A
Incomplete rings of strong, flexible cartilage, which stop the trachea from collapsing • Rings are incomplete so that food can move easily down the oesophagus behind the trachea
14
Q
Describe the lining of the
trachea and its branches
A
Lined with a ciliated epithelium with goblet cells between and below the epithelial cells • Goblet cells secrete mucus onto the lining of the trachea • Cilia beat and move the mucus along with anything trapped, away from the lungs • Most of it goes into the throat, is swallowed and digested • Cigarette smoke stops these cilia beating
15
Q
Describe the bronchi
A
Similar to the trachea, with the same
supporting rings of cartilage, but
they are smaller. Cartilage rings are
complete here
16
Q
Describe the bronchioles
A
• Smaller bronchioles (diameter >1mm) have no cartilage rings • Walls contain smooth muscle; contracts: the bronchioles constrict (close), relaxes: they dilate (open) • This changes amount of air reaching the lungs • Lined with a thin layer of flattened epithelium making some gas exchange possible
17
Q
What are alveoli?
A
Tiny air sacs which are the main gas exchange surfaces of the body • Unique to mammalian lungs • Each has a diameter of 200-300μm and consists of: • Thin layer of flattened epithelial cells, along with some collagen and elastic fibres (composed of elastin)
18
Q
What if the function of elastic
tissues in the alveoli?
A
• They allow the alveoli to stretch as air in drawn in • When they return to their resting size, they help squeeze the air out • This is known as the elastic recoil of the lungs
23
Q
What happens in inspiration
(inhaling)?
A
Diaphragm contracts to move down and become flatter - this displaces the digestive system organ downwards • External intercostal muscles contract to raise the ribs • Volume of chest cavity increases • Pressure in the chest cavity drops below the atmospheric pressure • Air is moved into the lungs
24
Q
What is expiration (exhaling)?
A
• Diaphragm relaxes and is pushed up by the displaced organs underneath • External intercostal muscles relaxed and rises falls; internal intercostal muscles can contract to help push air out more forcefully (only happens during exercise, or coughing and sneezing) • Volume of chest cavity decreases • Pressure in the lungs increases and rises above pressure in the surrounding atmosphere • Air is moved out of the lungs
26
Q
How does a spirometer work?
A
1. Subject should wear a nose clip to ensure no O2 escapes from the system and no additional air is added 2. Subject breathes through the mouth piece 3. As the subject inhales, O2 is drawn from the air chamber which therefore descends 4. As the subject exhales, the air chamber rises again 5. Air returning to the air chamber passes through the canister of soda lime which absorbs CO2 6. Movements of the air chamber are recorded by a data logger or on a revolving drum
27
Q
Define the following
A
1. Tidal volume: Volume of air that moves into and out of the lungs with each resting breath. About 500cm3, which uses 15% of the vital capacity of the lungs 2. Vital capacity: Volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath 3. Inspiratory reserve volume: Maximum volume of air you can breathe in over and above a normal inhalation 4. Expiratory reserve volume: Extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out 5. Residual volume: Volume of air that is left in your lungs when you have exhaled as hard as possible. This can’t be measured directly 6. Total lung capacity: The sum of the vi
27
Q
Define the following
A
1. Tidal volume: Volume of air that moves into and out of the lungs with each resting breath. About 500cm3, which uses 15% of the vital capacity of the lungs 2. Vital capacity: Volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath 3. Inspiratory reserve volume: Maximum volume of air you can breathe in over and above a normal inhalation 4. Expiratory reserve volume: Extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out 5. Residual volume: Volume of air that is left in your lungs when you have exhaled as hard as possible. This can’t be measured directly 6. Total lung capacity: The sum of the vi
37
Q
How does gas exchange take
place in insects?
A
1. Insects don’t transport O2 in blood 2. They have an air-filled tracheal system that supplies air directly to all the respiring tissues 3. Air enters the system via pores called spiracles 4. Air passes through the body in a series of tubes called tracheae 5. These divide into smaller tubes called tracheoles 6. The end of the tracheoles open into tracheal fluid 7. Gas exchange occurs between the air in the tracheole and the tracheal fluid
43
Q
How are the gills adapted for
successful gas exchange?
A
• Efferent blood vessel carries the blood leaving the gills in the opposite direction to the incoming water, maintaining a steep concentration gradient • Each gill consists of 2 rows of gill filaments (primary lamellae) attached to a gill arch. Their rich blood supply and large surface area, are the main site of gas exchange in the fish • Gill filaments are very thin, and their surface is folded into many secondary lamellae (gill plates) and need a flow of water to keep them apart, exposing the large surface area needed for gas exchange
