exchange surfaces Flashcards
(24 cards)
why do we need specialised exchange surfaces
its surface
area to volume ratio decreases so there is less nutrients
for single celled organisms the distance needed to be crossed over is short but not for multicelled organism
Features of an efficient exchange surface
large surface area
thin to ensure that the distance that needs to be crossed by the
substance is short.
good blood supply/ventilation to maintain a steep gradient,
The lungs
The lungs are a pair of structures with a large surface area located in the chest cavity with the ability to inflate.
the lungs structures
The lungs are surrounded by the rib cage which serves to protect
them. . External and internal intercostal muscles between the ribs which contract to raise and lower the ribcage respectively. A structure called the diaphragm separates the lungs from abdomen area.
how does air enter the body
The air enters through the nose, along the trachea, bronchi and bronchioles which are
structures well adapted to their role in enabling passage of air into the lungs. The gaseous exchange takes place in the walls of alveoli, which are tiny sacs filled with air
how do the trachea bronchi and bronchioles help the flow of air
The trachea, bronchi and bronchioles enable the flow of air into and out of the lungs. The airways are held open with the help of rings of cartilage, incomplete in the trachea to allow
passage of food down the oesophagus behind the trachea.
Cartilage
involved in supporting the trachea and bronchi, plays an important
role in preventing the lungs from collapsing in the event of pressure drop during exhalation
shape for flexibility to allow movement of food to pass though
large lumen so air can flow in and out easily
alveoli
-large conc of O2 in the alveoli and low conc of O2 in the blood
O2 diffuses down the gradient from the alveloi to the blood
-large conc of co2 in the blood and low conc of co2 in the alveoli
co2 diffuses up into the alvelous from the blood
features of the alveoli
large surface area due to large number of alveloli
walls are one cell thick for a short diffusion distance
giid blood suply as surrounded by a capilary network
small alveloi so large surface to volume ratio
Ciliated epithelium
present in bronchi, bronchioles and trachea, involved in
moving mucus along to prevent lung infection by moving it towards the throat
Goblet cells
cells present in the trachea, bronchi and bronchioles involved in mucus secretion to trap bacteria and dust to reduce the risk of infection with the help of lysozyme which digests bacteria
Smooth muscle
their ability to contract enables them to play a role in constricting
the airway, thus controlling its diameter as a result and thus controlling the flow of air to and from alveoli
Elastic fibres
– stretch when we inhale and recoil when we exhale thus controlling
the flow of air
inspiration
During inspiration, the external intercostal muscles contract whereas the internal ones relax, as a result cause the ribs to raise upwards. The diaphragm contracts and flattens this causes the volume inside the thorax to increase, thus lowering the pressure.
the atmospheric pressure creates a gradient, thus causing the air to enter the lungs
expiration
During expiration, the internal intercostal muscles contract whereas the external ones relax therefore lowering the rig cage. The diaphragm relaxes and rises upwards. These actions in
combination decrease the volume inside the thorax, therefore increasing the pressure, forcing the air out of the lungs.
spirometer
A spirometer is a device used to measure lung volume. A person using a spirometer breathes in and out of the airtight chamber, thus causing it to move up and down, leaving a trace on a graph which can then be interpreted.
Vital capacity
the maximum volume of air that can be inhaled or exhaled in a single breath. Varies depending on gender, age, size as well as height
Tidal volume
the volume of air we breathe in and out at each breath at rest
Breathing rate
the number of breaths per minute, can be calculated from the spirometer trace by counting the number of peaks or troughs in a minute
residual volume.
The volume of air which is always present in the lungs
fishes gas exchange
Fish have a small surface area to volume ratio for gas exchange, apart from this they have an impermeable membrane so gases can’t diffuse through their skin therefore fish need a specialised exchange surface
Fishes gills
Bony fish have four pairs of gills, each gill supported by an
arch. Along each arch there are multiple projections called gill filaments, with lamellae on them which participate in gas exchange. Blood and water flow across the lamellae in a counter current direction meaning they flow in opposite direction. The projections are held apart by water flow. Therefore, in the absence of water they stick together, thus meaning fish cannot survive very long out of water.
fishes ventilation
fishes have a continuous unidirectional flow.
Ventilation begins with the fish opening its mouth followed by lowering the floor of buccal cavity, thus enabling water to flow into it. Afterwards, fish closes its mouth, causing the buccal cavity
floor to raise, thus increasing the pressure. The water is forced over the gill filaments by the difference in pressure between the mouth cavity and opercular cavity. The operculum acts as a valve and pump and lets water out and pumps it in.
what do insects have instead of a specialised exchange system
oxygen needs to be transported directly to tissues undergoing respiration. This is achieved with the help of spiracles, small
openings of tubes, either bigger trachea or smaller tracheoles, which run into the body of an insect and supply it with the required gases. At the end of each tracheole is a small amount of tracheal fluid which allows gasses to dissolve and then diffuse into the cells.
Spiracles can be opened and closed to avoid excessive water loss
