chapter 7 exchange surfaces and breathing Flashcards
what are the 2 main reasons why diffusion alone is enough to supply the needs of single celled organisms?
•metabolic activity of a single-celled organism is low so O2 demands and CO2 production of the cell are relatively low
•SA:V ratio of the organism is large
what are the effective features that exchange surfaces have?
•high SA
•thin layers
•good blood supply
•ventilation to maintain diffusion gradient
what does increased surface area do for exchange surfaces?
provides the area needed for exchange and to overcome the limitations of SA:V of larger organisms. e.g. villi and alveoli
what do thin layers do for exchange surfaces?
provide short diffusion distances making the process fast and efficient.
what does a good blood supply do for exchange surfaces?
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 maintaining steep conc gradient
what does ventilation do for exchange surfaces?
for gases, a ventilation system also helps maintain conc gradients and makes the process more efficient. e.g. gills in fish
why do mammals need to have a gaseous exchange system rather than just diffusion?
they have a small SA:V, they have a high metabolic rate because they’re active and need to maintain their body temperature. this means they need oxygen for respiration
what is the gas exchange area in mammals?
the alveoli in the lungs
what are 3 adaptations of the nasal cavity? and why do we have them?
•large SA with good blood supply to warm air to body temp
•hairy lining which secretes mucus to trap dust and bacteria protecting lung tissue
•moist surfaces to increase humidity of incoming air reducing evaporation from exchange surfaces
what is the trachea?
the main airway carrying air from the nose to the chest. it is a wide tube supported by cartilage to stop it from collapsing
what do goblet cells and ciliated epithelial cells do?
goblet cells produce mucus to trap pathogens and dust.
the cilia on the cillaited epithelium move this mucus away from lungs back to the mouth to be swallowed or spat out
what is the order of structure in the respiratory system?
mouth>trachea>bronchi>bronchioles>aleveoli
what specialised structures does the trachea have?
cartilage in c-shaped rings, cilliated epithelial cells and goblet cells, smooth muscle and elastic tissue
what specialised cells do the bronchi have?
cartilage in irregular blocks to give structural support. Same as trachea
what specialised cells do the bronchioles have?
smooth muscle, flattened epithelium, small amounts of cartilage
what specialised cells do alveoli have?
thin layer of squamous epithelial cells, some collagen, elastic fibres (to stretch as air is drawn in and squeeze air out when they return to original size)
what are the main adaptations of the alveoli for effective gaseous exchange?
•Large surface area- 300~500million alveoli per adult lung giving a combined SA of 50~75m^2.
what is ventilation?
mechanism of breathing which involves diaphragm and antagonistic interactions between intercoastal muscles bringing about pressure changes in thoracic cavity
why is ventilation important?
maintains steep concentration gradient for gas exchange
what is lung surfactant?
chemical mixture containing phospholipids and hydrophilic and phobic proteins which coats the surfaces of the alveoli and prevents them collapsing after every breath
what is the thorax?
the chest cavity
describe the process of inspiration (energy using process)
•diaphragm contacts, flattening and lowering.
•external intercostal muscles contract moving the ribs upwards and outwards.
•the volume of the thorax increases so pressure in the thorax is reduced to lower than atmospheric pressure.
•air is drawn in down the respiratory tract equalising the pressure inside and outside the lungs
describe the process of expiration (passive process)
•muscles of diaphragm relax so it’s moves upwards into a dome shape
•external intercostal muscles relax so ribs move downwards and inwards under gravity.
•elastic fibres in alveoli return to normal length
•volume of thorax decreases so pressure in thorax increases above atmospheric
•air moves out of the lungs until pressure is equal inside and outside
what are three common ways of measuring breathing?
•peak flow meter
•vitalographs
•spirometer
what is a peak flow meter?
simple device to measure the rate at which air can be expelled from the lungs
what is a vitalograph?
the patient breathes out as quickly as possible and the instrument produces a graph of the amount of air they breath out and how quickly it is breathed out
what is a spirometer?
measures different aspects of lung volume and investigates breathing patterns
what is the tidal volume?
volume of air that moves into and out of the lungs with each rating breath. it is around 500cm3 in most adults at rest (~15% vital capacity)
what is the vital capacity?
volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest intake of breath
what is inspiratory reserve volume?
maximum volume of air you can breathe in over and above normal inhalation
what is expiratory reserve volume?
extra amount of air you can force out of your lungs over and above the normal tidal volume
what is residual volume?
volume of air that is left in the lungs when you have exhaled as hard as possible
what is the total lung capacity?
sum of vital capacity and residual volume
what is the breathing rate?
number of breaths taken per minute
what is ventilation rate and how do you work it out?
•it is the volume of air inhaled in one minute
•ventilation rate = tidal volume x breathing rate
what are spiracles?
small openings along the thorax and abdomen of an insect that open and close to control the amount of air moving in and out of the gas exchange system and the level of water loss from the exchange surfaces.
what are the tracheae of insects?
largest tubes in insect respiratory system up to 1mm in diameter and they carry air into the body
what are insect tracheae lined with?why?
spirals of chitin which keep them open if they are bent or pressed, it is relatively impermeable to gases so gaseous exchange cannot occur here
what are the tracheoles in insects?
small tubes of 0.6-0.8 micrometres. each tracheole is a single greatly elongated cell with no chitin so they are freely permeable to gaseous exchange(it is the main site)
what is tracheal fluid?
fluid located towards the end of the tracheoles in insects that helps control the SA available for gas exchange and water loss.
what are some alternative methods of increasing gaseous exchange in insects that isn’t opening and closing of spiracles?
•mechanical ventilation of tracheal system- movements of the abdomen or thorax actively pumping air in out due to pressure changes
•collapsible enlarged tracheae or air sacs which act as reservoirs- increase the amount of air moved through the gaseous exchange system.
how much more dense and viscous is water than air?
water is 1000x more dense than air and 100x more viscous having a much lower oxygen content
how are bony fish adapted for gaseous exchange?
they cannot meet oxygen demands from diffusion alone due to SA:V.
they have gills to allow water to move in one direction only
how are gills adapted for gaseous exchange exchange?
•large SA
•good blood supply
•thin layers
what are gills?
gaseous exchange organs of fish comprised of gill plates, gill filaments and gill lamellae
what is the operculum?
bony flap covering the gills of bony fish. part of the mechanism that maintains a constant flow of water over the gas exchange surfaces
what are gill filaments?
they occur in large stacks and need a flow of water to keep them apart, exposing the surface area needed for gaseous exchange
what are gill lamellae?
have rich blood supply and large SA and they are the main site of gaseous exchange in fish
what is the biggest challenge of gills?
need a continuous flow of water for gas exchange
how do cartilaginous fish such as sharks ventilate the gills?
they rely on continuous movement known as ram ventilation.
how have bony fish evolved to not rely on movement to ventilate the gills?
pressure changes such as inhalation and exhalation of mammals
describe how bony fish intake water when stationary.
Intake of water- mouth is opened and floor of buccal cavity is lowered. this increases the volume and decreases the pressure so water moves in. at the same time the opercular valve is shut and the opercular cavity containing the gills expands. this lowers pressure and the floor of the buccal cavity moves up increasing the pressure there so water from the buccal cavity moves over the gills
describe how bony fish maintain a flow of water over the gills.
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 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.
what do the tips of adjacent gill filaments overlapping do?
increase resistance to the flow of water over the gill surfaces and slows down the movement of water to create more time for gas exchange to take place
what does countercurrent flow in the gils mean? and what does it do?
•blood and water flow in opposite directions
•this allows for steeper concentration gradients to be maintained and allows bony fish to remove around 80% of oxygen from water compared to about 50% in cartilaginous fish with parallel systems
