Exchange Surfaces and Breathing
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- Created by: LBCW0502
- Created on: 14-02-17 17:50
Why is diffusion alone enough to supply the needs of single-celled organisms? (2)
There is low metabolic activity (oxygen demands/carbon dioxide production is low). Large surface area to volume ratio
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What happens as the organism becomes larger?
Metabolic activity increases, oxygen demands increase, diffusion distances increase, smaller SA:Vol ratio (diffuse is not enough)
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What are the four features of specialised exchange surfaces?
Increased surface area, thin layers, good blood supply and ventilation to maintain diffusion gradient
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In which organ does the exchange of gases take place in humans?
In the lungs
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What are the features of a nasal cavity? (3)
Large surface area with a good blood supply which warms body temperature. Hair lining which secretes mucus to trap dust/bacteria to prevent infection. Moist surfaces to increase humidity, reducing evaporation from exchange surfaces
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?Which structure in the trachea prevents the airway collapsing?
Incomplete rings of cartilage (rings are incomplete to allow food to pass down oesophagus behind trachea)
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What is the trachea lined with?
Ciliated epithelium (with goblet cells between and below the epithelial cells)
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What is the function of goblet cells?
Secrete mucus onto the lining of the trachea, to trap dust and micro-organisms that has escaped the nose lining
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What is the function of cilia?
They beat in unison (rhythmic manner) to move mucus (and dirt/microbes) away from the lungs. Most of it goes into the throat and is swallowed and digested
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What is one of the effects of cigarette smoke on cilia?
They stop cilia from beating
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Describe the structure of the bronchus
Trachea divides into left bronchus (left lung) and right bronchus (right lung). Similar structure to trachea with same supporting rings of cartilage, but they are smaller
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Describe the structure of bronchioles
Diameter of 1mm or less, no cartilage rings, walls are made of smooth muscle (constrict/dilate). Lined with flattened epithelium to make gaseous exchange possible
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Describe the structure of alveoli
Tiny air sacs, diameter of around 200-300 micrometres. Thin layer of flattened epithelial cells with collagen and elastin fibres (allow elastic recoil)
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What are the feature of alveoli which make it a suitable exchange surface?
Large surface area, thin layers, good blood supply and good ventilation
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What is lung surfactant?
Covers inner surface of alveoli. Makes it possible for alveoli to remain inflated
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What is ventilation?
The movement of air
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List the parts of the body involved in ventilation
Rib-cage, diaphragm, external intercostal muscles, internal intercostal muscles
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What are pleural membranes?
Membranes which line the thorax and surround the lungs
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What is the pleural cavity?
The space between pleural membranes - usually filled with a thin layer of lubricating fluid so the membranes slide easily over each other as you breathe
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Describe inspiration
Energy-using process. Diaphragm contracts, external intercostal muscles contract, ribs move up/out, volume of thorax increases, pressure decreases, air is drawn through nasal passages/trachea/bronchi/bronchioles to equalise pressure
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Describe expiration
Passive process. Diaphragm relaxes, external intercostal muscles relax, ribs move down/in, elastic fibres recoil, volume of thorax decreases, pressure increases, air moves out of lungs to equalise pressure
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Describe what happens during forced exhalation
Energy-using process. Internal intercostal muscles contract, ribs move down hard and fast, abdominal muscles contract, forcing the diaphragm up to increase pressure in the lungs rapidly
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What is a peak flow meter?
A simple device that measures the rate at which air can be expelled from the lungs (e.g. people with asthma monitor function of lungs)
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What are vitalographs?
Sophisticated versions of the peak flow meter. Patient breaths out quickly through mouthpiece and instrument produces a graph of the amount of air exhaled and how quickly air was inhaled. The volume of air is called forced expiratory volume in 1 s
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What is a spirometer?
Used to measure different aspects of lung volume/investigate breathing patterns
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What is tidal volume?
The volume of air that moves into and out of the lungs with each resting breath. It is around 500 cm3 in most adults at rest, which uses about 15% of the vital capacity of the lungs
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What is vital capacity?
The volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest intake of breath
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What is inspiratory reserve volume?
The maximum volume of air you can breathe in over and above normal inhalation
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What is 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
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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 directly
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What is total lung capacity?
The sum of the vital capacity and the residual volume
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What is the breathing rate?
The number of breaths taken per minute
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What is ventilation rate?
The total volume of air inhaled in one minute
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How do you calculate the ventilation rate?
Tidal volume x breathing rate (per minute)
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What happens when oxygen demands of the body increase?
Tidal volume increases (larger percentage of vital capacity), breathing rate increases, ventilation of lungs/oxygen uptake increases
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Describe the structure of gaseous exchange system in insects (2)
Tough exoskeleton allows little/no gaseous exchange to take place. No blood pigments to carry oxygen
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What are spiracles?
Small openings along the thorax/abdomen. Air enters/leaves and water is lost
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How do insects maximise efficiency of gaseous exchange and minimise loss of water
Spiracles can be opened or closed by sphincters. Spiracle sphincters are kept closed as much as possible to minimise water loss (open during high demand of oxygen, close during low demand of oxygen)
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What are tracheae?
Largest tubes of the insect respiratory system (up to 1mm in diameter). They carry air into the body. Run in/along body of insect
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What are the tracheae tubes lined with?
Chitin - keeps them open if they are bent/pressed. It makes up the cuticles and is relatively impermeable to gases (little gaseous exchange)
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Describe the features of tracheoles in insects
Narrower tubes (diameter 0.6-0.8 micrometers). Each tracheole is a single, greatly elongated cell with no chitin lining (freely permeable to gases). Run between cells (gaseous exchange between air/respiring cells)
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What is the advantage of a large number of tiny tracheoles?
Provides a very large SA:Vol ratio for gaseous exchange
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What is tracheal fluid?
Fluid located towards the end of the tracheoles which limits the penetration of air for diffusion
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What happens when oxygen demands build up? (e.g. insect is flying)
There is a build up of lactic acid in tissues which results in water moving out of tracheoles via osmosis. This exposes more surface area for gaseous exchange
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Describe mechanical ventilation of the tracheal system
Air is actively pumped into the system by muscular pumping movements of the thorax/abdomen. Movements change volume of body and pressure in tracheae/tracheoles. Air id drawn into the tracheae/tracheoles or forced out as the pressure changes
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Describe the function of collapsible enlarged tracheae/air sacs which act as air reservoirs
Used to increase the amount of air moved through the gas exchange system. They are usually inflated and deflated by ventilating movements of the thorax/abdomen
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Describe the features of gills which make it a suitable exchange surface
Large surface area, good blood supply and thin layers
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Where are the gills located?
Contained in a gill cavity and covered by a protective operculum (bony flap) which active in maintaining a flow of water over the gills
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Describe inhalation in the ventilation of the gills
Mouth is opened, floor of buccal cavity lowered. Increase in volume/decrease in pressure. Water moves into buccal cavity. Opercular valve is shut and opercular cavity containing gills expands (lowers pressure)
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What happens when the buccal cavity moves up?
There is an increase in pressure so water moves from the buccal cavity over the gills
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Describe exhalation in the ventilation of the gills
Mouth closes. Operculum opens and sides of opercular cavity move inwards. Increase in pressure of opercular cavity and force water over the gills and out of the operculum. Floor of buccal cavity is moved up, maintaining a flow of water over the gills
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Describe the features of gill filaments which make it effective in gaseous exchange
Tips of adjacent gill filaments overlap. This increases resistance to flow of water over the gill surfaces and slows down the movement of water. There is more time for gaseous exchange to take place
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What is a parallel system?
Blood in the gills and water flowing over gills travel in the same direction. There is an initial steep oxygen concentration gradient. Diffusion takes place until there is equilibrium (no net movement)
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What is a countercurrent system?
Blood and water flow in opposite directions. There is a steep oxygen concentration gradient which a much higher level of oxygen saturation of blood achieved
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Other cards in this set
Card 2
Front
What happens as the organism becomes larger?
Back
Metabolic activity increases, oxygen demands increase, diffusion distances increase, smaller SA:Vol ratio (diffuse is not enough)
Card 3
Front
What are the four features of specialised exchange surfaces?
Back
Card 4
Front
In which organ does the exchange of gases take place in humans?
Back
Card 5
Front
What are the features of a nasal cavity? (3)
Back
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