Flashcards in Exchange Surfaces and Breathing Deck (89):
What are the two main reasons why diffusion alone is enough to supply the needs of single-celled organisms?
1) The metabolic activity of the organism is low so oxygen demands and carbon dioxide production is low
2) The surface area to volume ratio of the organism is large
Why can't larger, multicellular organisms rely on diffusion?
The difference between the cells where the oxygen is needed and the supply of oxygen is too great for effective diffusion to take place. Large SA:V ratio so gases can't be exchanged fast enough.
What is the benefit of an exchange surface having an increased surface area? Give an example of an exchange surface with an increased surface area.
Provides the area needed for exchange and overcomes the limitations of the SA:V ratio of larger organisms.
Examples are root hair cells and the villi in the small intestine.
What is the benefit of an exchange surface having thin layers? Give an example of an exchange surface with thin layers.
These mean the distances that substances have to diffuse are short, making the process fast and efficient.
Examples are the alveoli and the villi of the small intestine.
What is the benefit of an exchange surface having a good blood supply? Give an example of an exchange surface with a good blood supply.
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.
An example is the gills of a fish.
What is the benefit of an exchange surface having ventilation to maintain a diffusion gradient? Give an example of an exchange surface with ventilation to maintain a diffusion gradient.
For gases, a ventilation system helps to maintain concentration gradients and makes the process more efficient.
An example is the alveoli.
Explain why mammals need a gaseous exchange system.
They have a small SA:V ratio and a high metabolic rate due to high levels of activity and they have to maintain their body temperature.
What are the three important features of the nasal cavity?
1) a large SA with a good blood supply, which warms the air to body temperature
2) a hairy lining which secretes mucus to trap dust and bacteria protecting delicate lung tissue from irritation and infection
3) moist surfaces which increase the humidity of the incoming air, reducing evaporation from the exchange surfaces
True or false? After passing through the nasal cavity, the air entering the lungs is a similar temperature and humidity to the air already there.
What is the trachea?
The trachea is the main airway carrying clean, warm, moist air from the nose down into the chest.
The trachea is a wide tube supported by incomplete rings of strong, flexible cartilage. What is the function of these rings?
They stop the trachea from collapsing and are incomplete so that food can move easily down the oesophagus behind the trachea.
What are the two types of cells found in the lining of the trachea and its branches?
Ciliated epithelial cells and goblet cells.
What is the function of ciliated epithelial cells in the lining of the trachea?
The cilia beat and move the mucus, along with any trapped dirt or microorganisms, away from the lungs.
What happens to the trapped dirt, mucus and microorganisms once the cilia moves it along?
Most of it does in to the throat and is swallowed and digested.
Give one substance that affects cilia cells and describe what it does.
Cigarette smoke prevents the cilia from beating.
What is the function of goblet cells in the lining of the trachea?
Goblet cells secrete mucus onto the lining of the trachea to trap dust and microorganisms that have escaped the nose lining.
Describe where the bronchus is located and explain the structure.
In the chest cavity, the trachea divides to form the left bronchus leading to the left lung and the right bronchus leading to the right lung. They are similar in structure to the trachea with the same supporting rings of cartilage, but they are smaller.
Describe the structure of the bronchioles.
They are 1mm in diameter and have no cartilage rings. The walls contain smooth muscle and are lined with a thin layer of flattened epithelium.
How does the smooth muscle lining in the bronchioles relate to its function?
When the smooth muscle contracts the bronchioles constrict. When it relaxes, the bronchioles dilate. This changes the amount of air reaching the lungs.
What does the thin layer of flattened epithelium in the lining of the bronchioles allow?
Some gaseous exchange.
What are alveoli?
Tiny air sacs which are the main gas exchange surfaces of the body.
Describe the structure of an alveolus. How does it's structure relate to it's function?
Each alveolus consists of a layer of thin, flattened epithelial calls along with some collagen and elastic fibres (composed of elastin). The elastic tissues allow the alveoli to stretch as air is drawn in. When they return to their resting size, they help to squeeze air out. this is known as elastic coil.
The alveoli have many adaptations for effective gaseous exchange. Why is surface area adapted?
Due to their shape, they have a much larger surface area. this means that it is large enough to allow enough oxygen to diffuse into the body.
The alveoli have many adaptations for effective gaseous exchange. Why is the thickness adapted?
Both the alveoli and the capillaries that surround them have walls that are thin, only one single epithelial cell thick. This means the diffusion distances are very short.
The alveoli have many adaptations for effective gaseous exchange. How is good blood supply an adaptation?
The constant blood supply through the many capillaries brings carbon dioxide and carries away oxygen. This maintains a steep concentration gradient for both carbon dioxide and oxygen between the air and blood.
The alveoli have many adaptations for effective gaseous exchange. How is good ventilation an adaptation?
Breathing air in and out of the alveoli helping to maintain a steep diffusion gradient for oxygen and carbon dioxide between the blood and the air.
What is the purpose of the inner surface of the alveoli being covered in a thin layer of a solution of water, salts and lung surfactant.
The surfactant makes it possible for the alveoli to remain inflated. Oxygen can dissolve into the water before diffusing into the blood.
What is ventilation?
The movement of air in and out of the lungs as a result of pressure changes in the thorax brought about by the breathing movements.
What is the diaphragm?
A broad, domed sheet of muscle which forms the floor of the thorax.
Where are the internal and external intercostal muscles located?
Between the ribs.
What is the thorax lined with?
Pleural membranes which surround the lungs.
What is the pleural cavity filled with and why?
Filled with a thin layer of lubricating fluid so the membranes slide easily over each other as you breathe.
Fill in the gaps. The _____ cage provides a semi-______ case within which _____ can be lowered with respect to the _____ outside it.
The RIB cage provides a semi-RIGID case within which PRESSURE can be lowered with respect to the AIR outside it.
What is inspiration?
Is Inspiration an energy-using process?
Describe the process of inspiration.
The dome-shaped diaphragm contracts, flattens and lowers. The external intercostal muscles contract moving the ribs upwards and outwards. The volume of the thorax increases so the pressure decreases. The pressure is now lower than the pressure in the environment. Air is drawn in through the nasal passages, trachea, bronchi and bronchioles into the lungs. Pressure is now equalised.
Is normal expiration and energy-using process?
No, it is passive
What is expiration?
Describe the process of expiration.
The muscles of the diaphragm relax so it returns to its resting domed shape. The external intercostal muscles relax so the ribs move down. The elastic fibres in the alveoli return to their normal length. The volume of the thorax decreases. The pressure inside the thorax is greater than the pressure of the environment so the air moves out until pressure equalises.
What happens if you forcibly exhale using energy?
The internal intercostal muscles contract, pulling the ribs down hard and fast and the abdominal muscles contract forcing the diaphragm up to increase the pressure in the lungs rapidly
A peak flow meter can be used to measure the capacity of the lungs. Explain what it is.
It is a simple device that measures the rate at which air can be expelled from the lungs. It is often used by people who have asthma to monitor how well their lungs are working
What is a spirometer used for?
A device commonly used to measure different aspects of the lung volume or to investigate breathing patterns
What is the tidal volume? What is it at rest in most adults?
Tidal volumes the volume of air that moves into and out of the lungs with each resting breath. It is around 500cm3 in most adults at rest
What is vital capacity
The volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath.
What is inspiratory reserve volume?
The maximum amount of air you can breathe in over and above a normal inhalation.
What is expiratory reserve volume?
The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out.
What is residual volume?
The volume of air that is left in your lungs when you have exhaled as hard as possible. This cannot be measured.
What is total lung capacity?
The sum of the vital capacity and the residual volume
On a spirometer recording, where would you find the residual volume?
Underneath the bottom of the lowest trough.
On a spirometer recording, where would you find the tidal volume?
The distance between the peak and trough of the normal waves.
On a spirometer recording, where would you find the inspiratory capacity?
From trough to highest peak.
On a spirometer recording, where would you find the inspiratory reserve volume?
From the top of the ordinary peak to top of the highest peak.
On a spirometer recording, where would you find the vital capacity?
From the highest peak to the lowest trough.
What is breathing rate?
The number of breaths taken per minute.
What is ventilation rate?
The total volume of air inhaled in one minute.
How do you calculate ventilation rate?
Tidal volume X breathing rate (per minute)
What happens to tidal volume and breathing rate when oxygen demands of the body increase? Why does this occur?
Tidal volume can increase from 15% to 50% of vital capacity. The breathing rate can also increase. The ventilation of the lungs and so the oxygen uptake during gaseous exchange can be increased to meet the demands of the tissues.
What do insects have that means that little or no gaseous exchange can take place?
A tough exoskeleton and no blood pigments that can carry oxygen.
True or false? The gaseous exchange system of insects has evolved to deliver the oxygen straight to the cells and remove carbon dioxide in the same way.
How does air enter and leave an insect?
Along the thorax and abdomen of most insects are small openings known as spiracles. Air enters and leaves through these
How do insects try to minimise water loss?
The spiracles can be opened or closed by sphincters. They are kept closed as much as possible to minimise water loss.
How is spiracle opening linked to activity level?
When an insect is inactive and oxygen demands are very low, the spiracles will all be closed most of the time. When the oxygen demand is raised or the carbon dioxide levels build up, more of the spiracles open.
Describe the structure of the tracheae which lead away from the spiracles in insects.
They are the largest tubes of the insect respiratory system that carry air into the body. The tubes are lined by spirals of chitin which will keep them open.
What is chitin?
An impermeable material to gas that makes up the cuticle.
What are tracheoles?
Each tracheole is a single, greatly elongated cell with no chitin lining so they are freely permeable to gases.
Where does most of the gaseous exchange take place between the air and the respiring cells in insects?
In the tissues of the insect, running between individual cells.
How are the tracheoles in insects adapted for gas exchange?
There are a vast number of tiny tracheoles so there is a very large surface area for gaseous exchange. The walls are moist so oxygen dissolves in it easily.
When an insect is particularly active, lactic acid builds. Explain the effect that this has on the insect.
At the end of the traceless there is tracheal fluid which limits the penetration of oxygen. The lactic acid build up means that water diffuses out of the traceless by osmosis which exposes more surface area for gas exchange.
True or false? All of the oxygen needed by the cells of an insect is supplied to them by the tracheal system.
Larger insects have higher energy demands. One way of increasing energy is mechanical ventilation of the tracheal system. Explain how this works.
Air is actively pumped in to the system by muscular pumping of the thorax and/or the abdomen. This changes the volume of the body and in turn changes the pressure in the tracheae and tracheoles. Air is drawn in and forced out as pressure changes.
Larger insects have higher energy demands. One way of increasing energy is collapsable enlarged tracheae and tracheoles. Explain how this works.
These are used to increase the amount of air moved through the gas exchange system. They are inflated and deflated by the ventilating movements of the thorax and abdomen.
Why is it not possible for fish to move water in and out of lung like respiratory organs?
Water is more dense than air and is more viscous so it would use too much energy.
How did bony fish overcome the problem of moving the thicker more dense water?
They move water in only one direction.
Why do bony fish have a high oxygen demand?
Because they are very active.
What are gills?
A fish organ of gaseous exchange
Describe the structure of gills in bony fish.
They have a large surface area, good blood supply and thin layers needed for gaseous exchange.
Where are the gills located in bony fish? How are they protected?
In a gill cavity. They are protected by a operculum (bony flap)
Other than protection, what is a role of the operculum?
It is active in maintaining a flow of water over the gills
What are gill lamellae? What is their structure?
They have a rich blood supply and large surface area so are the main site of gaseous exchange in the fish.
What are gill filaments?
They occur in large stacks (gill plates) and need a flow of water to keep them apart, exposing a large surface area needed for gas exchange.
How does a fish maintain a current of water over their gills whilst swimming?
By opening their mouth and operculum.
What is ram ventilation?
Relying on the continuous movement to ventilate the gills.
How do bony fish move water when they aren't moving? (Stage 1, water in)
The mouth is opened and the buccal cavity is lowered. This increases the volume and so the pressure decreases. Water moves into the buccal cavity. The opercular valve is shut and the popular cavity expands. The pressure of the opercular cavity is lowered. The floor of the buccal cavity moves up and pressure increases. Water moves from the buccal cavity over the gills.
How do bony fish move water when they aren't moving? (Stage 2, water in)
The mouth closes, the operculum opens and the sides of the opercular cavity move inwards. All of these actions increase the pressure in the opercular cavity and force the water over the gills and out of the operculum. The floor of the buccal cavity is steadily moved up, maintaining a flow of water over the gills.
Name the five adaptations that gills have to ensure effective gaseous exchange in water.
Large surface area for diffusion, a rich blood supply to maintain a concentration gradient, thin layers so a short diffusion distances, overlapping adjacent gill filaments and a countercurrent system.
One of the extra adaptations that gills have is that the tips of adjacent gill filaments overlap. Why is this good?
Having gill filaments that overlap increases their resistance to the flow of water over the gill surfaces and slows down the movement of the water. As a result there is more time for gaseous exchange to take place.
One of the extra adaptations that gills have is they have a countercurrent system. What is meant by this and why is it good?
A steep concentration is needed for fast efficient diffusion. Because the blood and water flow in opposite directions, a countercurrent exchange system is set up. This adaptation ensures that steeper concentration gradients are maintained than if blood and water flow in the same direction. As a result more gaseous exchange can take place.
What is the percentage of oxygen that bony fish can extract from the water compared with cartilaginous fish? Why?
80% compared with 50%. Bony fish have a countercurrent system whilst cartilaginous fish have a parallel system.