Exchange Surfaces and Breathing Flashcards
what are the main reasons diffusion is enough to supply the needs of single-celled organisms?
- the metabolic activity of a single-celled organism is usually low, so the oxygen demands and carbon dioxide production of the cell are relatively low
- the SA:V ratio of the organism is large
what are some characteristics of an effective exchange surface?
- increased surface area
- thin layers, so the distance the substances have to diffuse is short
- good blood supply, which maintains a steep concentration gradient
- ventilation to maintain diffusion gradient
why do humans have a high metabolic rate?
because they are active and maintain their body temperature independent from the environment
what are some important features in a nasal cavity?
- large surface area with a good blood supply, which warms the air to body temp
- has a hairy lining, which secretes mucus to trap dust and bacteria, protecting delicate lung tissue from irritation and infection
- has moist surfaces, which increases humidity of the incoming air, reducing evapouration from the exchange surfaces
what is the trachea?
the main airway carrying clean, warm, moist air from the nose down into the chest
what keeps the trachea supported?
incomplete rings of strong, flexible cartilage, which stops the trachea from collapsing
why are the rings of the trachea incomplete?
so that food can move easily down the oesophagus behind he trachea
what is the trachea lined with?
ciliated epithelium, with goblet cells between and below the epithelial cells
what do goblet cells do in he trachea?
secrete mucus onto the lining of the trachea to trap dust and microorganisms that have escaped the nose lining
what do the cilia do in the trachea?
beat and move mucus, along with any trapped dirt and microorganisms, away from the lungs
what is an effect of smoking on the cilia in the trachea?
they stop beating
what do the trachea divide into in the chest cavity?
divides to form the left bronchus, leading to the left lung, and the right bronchus leading to the right lung
how is the structure of the bronchus similar to the trachea?
has the same supporting rings of cartilage, but they are smaller
what do the bronchi divide into in the lungs?
many small bronchioles
what do the smaller bronchioles not have?
cartilage rings
what do the walls of bronchioles contain?
smooth muscle
what happens when the smooth muscle in the walls of bronchioles contract and relax?
contract- the bronchioles constrict
relax- bronchioles dilate
what are bronchioles lined with?
a thin layer of flattened epithelium, making some gaseous exchanges possible
what are alveoli?
tint air sacs, which are the main gas exchange surfaces of the body`
what is the diameter of each alveolus?
around 200-300 um
what do alveolus consist of?
a thin layer of flattened epithelial cells, along with some collagen and elastic fibres
what do the elastic tissues in the alveoli allow?
allow the alveoli to stretch as air is drawn in
what is elastic recoil?
when the alveoli stretch to draw air in and return to resting size to help squeeze the air out
what are the main adaptations of the alveoli for effective gaseous exchange?
- large surface area
- thin layers
- good blood supply
- good ventilation
how is air moved in and out of the lungs?
as a result of pressure changes in the thorax (chest cavity) brought about by the breathing movements
what does the rib cage provide?
provides a semi-rigid case within which pressure can be lowered with respect to the air outside it
what is the diaphragm?
a broad, domed sheet of muscle, which forms the floor of the thorax
where are the external and internal intercostal muscles found?
in between the ribs
what is the thorax lined with?
the pleural membranes, which surround the lungs
what is the pleural cavity usually filled with?
a thin layer of lubricating fluid so the membranes slide easily over each other as you breathe
what happens in inspiration?
- the dome shaped diaphragm contracts, flattening, and lowering
- the external intercostal muscles contract, moving the ribs upwards and outwards
- the volume of the thorax increases so the pressure in the thorax is reduced
- it is now lower than the pressure of the atmospheric air, so air is drawn through the nasal passages, trachea, bronchi and bronchioles into the lungs
what type of process is inspiration?
an energy-using process
what type of process is expiration?
a passive process
what happens in expiration?
- the muscles of the diaphragm relax so it moves up into its resting domed shape
- the external intercostal muscles relax so the ribs move down and inwards under gravity
- the elastic fibres in the alveoli of the lungs return to their normal length
- now the pressure inside the thorax is greater than the pressure of the atmospheric air, so air moves out of the lungs until the pressure inside and out is equal again
how can the volume of air that is drawn in and out of the lungs be measured?
- a peak flow meter
- vitalograph
- spirometer
what is a peak flow meter?
a simple device that measure the rate at which air can be expelled from the lungs
what are the aspects of lung volume that can be measured?
- tidal volume
- vital capacity
- inspiratory reserve volume
- expiratory reserve volume
- residual volume
- total lung capacity
what is tidal volume?
the volume of air that moves into and out of the lungs with each resting breath
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 volume of air you can breathe in 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
what is total lung capacity?
the sum of the vital capacity and residual volume
what do recordings from a spirometer show?
the different volumes of air moved in and out of the lungs
what is the breathing rate?
the number of breaths taken per minute
what is the ventilation rate?
the total volume of air inhaled in one minute
what is the equation for ventilation rate?
tidal volume x breathing rate per minute
what happens when the oxygen demands of the body increases?
the tidal volume of air can increase from 15% to as much as 50% of the vital capacity
why can diffusion into the body of insects not occur?
- they have a touch exoskeleton through which little or no gas exchange can take place
- they do not usually have blood pigments that carry oxygen
what are spiracles?
small openings along the thorax and abdomen of most insects
what enters and leaves through the spiracles of an insect?
air enters and leaves and water leaves
how are spiracles opened and closed?
by sphincters
are sphincters usually open or closed and why?
usually kept closed as much as possible to minimise water loss
when are most spiracles open in an insect?
when the oxygen demand is raised or the carbon dioxide levels build up
what leads away from the spiracles inside an insect?
tracheae
what do tracheae carry in an insect?
air into the body
what are tracheae lined with in insects and what is its purpose?
chitin which keep them open if they are being bent or pressed
why does little gas exchange take place in the tracheae of insects?
chitin is relatively impermeable to gases
what do tracheae branch into in insects?
tracheoles
how are tracheoles in insects freely permeable to gas?
they do not have a chitin lining
how does oxygen diffuse into surrounding cells in an insect?
oxygen dissolves in moisture on the walls of the tracheoles and diffuse into the surrounding cells
where is tracheal fluid located in an insect?
towards the end of the tracheoles
what does tracheal fluid do inside insects?
limits the penetration of air for diffusion
what happens inside an insect when oxygen demands build up?
a lactic acid build up in the tissues result in water moving out the tracheoles by osmosis, which exposes more surface area for gaseous exchange
what are some examples of alternative methods of gaseous exchange in larger insects?
- mechanical ventilation of the tracheal system
- collapsible enlarged tracheae or air sacs which act as air reservoirs
how does mechanical ventilation work as gaseous exchange in larger insects?
- air is actively pumped into the system by muscular pumping movements of the thorax and/or abdomen
- these movements change the volume of the body which changes the pressure in the tracheae and tracheoles
- air is drawn down into the tracheae and tracheoles, or forced out, as the pressure changes
how do collapsible enlarged tracheae work as gaseous exchange in larger insects?
- they used to increase the amount of air moved through the gas exchange system
- they are usually inflated and deflated by the ventilating air movements of the thorax and abdomen
water is _______ times denser than air, ______ times thicker and has a much ________ oxygen content?
- 1000
- 100
- lower
what does viscous mean?
thickness
why have fish developed a different type of respiratory system?
it would use up far too much energy to move dense, viscous water in and out of their lung-like respiratory organs
why is diffusion not enough to supply bony fishes inner cells with oxygen?
- they are large animals so have a low SA:V ratio, which means diffusion would be slow
- their scaly outer covering does not allow gaseous exchange
what have bony fish evolved?
a ventilatory system adapted to take oxygen from the water and get rid of carbon dioxide into the water
what are some factors of gills that make them good for gaseous exchange?
- have a large surface area
- good blood supply
- thin layers
what is the operculum?
a hard, plate-like, bony flap that covers the gills of a bony fish
what are the two categories of fish?
- bony fish
- cartilaginous fish
what are some adaptations of gills?
- the tips of adjacent gill filaments overlap which increases the resistance to the flow of water over the gill surfaces and slows down the movement of water, which means there is more time for gaseous exchange to take place
- the water moving over the gills and the blood in the gill filaments flow in different directions which ensures a steeper concentration gradient
