Topic 3 Exchange Surfaces Flashcards
Nasal cavity
•large surface area with a good blood Supply
• hairy lining which secretes mucus which prevents dust and bucteria, Protecting delicate lung tissue from irritation and infection.
• moist surfaces which increases the humidity of incoming air reducing evaporation from the exchange surface.
Trachea
•lined with cilliated epithelial cells and goblet cells in between and below the epithelial cells.
•Goblet cells secrete mucus which beat/ waft mucus up to the throat were it a swallowed and broken down in to stomach.
•supported with at wide c shaped cartilage which is strong and flexible. C shape also allows food to travel through the oesophagus easily. Also allows it to expand and contract when needed.
Bronchus
•located where the trachea splits into a left and right bronchus
•similar structure to trachea
•contains smooth muscle which contracts airways when there is a problem with air quality.
•splits off into bronchioles
Bronchioles
•small bronchioles less than 1mm contain no cartilage
• walls contain smooth muscle
• lined with flattened epithelial cells for gas exchange
Alveoli
•tiny air filled sacs which act as the main source of gas exchange for the body
•contains a one cell thick flattened cell wall made of epithelial cells
•contains elastin fibres
-can stretch and allows alveolar tissue to expand to prevent bursting. The also undergo elastic recoil which helps exhalation.
Ventilation in humans
Inhaling
External intercostal muscle contracts which causes rib cage to move up and out.
• diaphragm contracts (flattens).
•The thorax increases in volume.
• This causes pressure to be drawn out which causes Fresh air to flow into the lungs.
Exhaling
•Intercostal muscle relax and the ribcage drops down and in
• The diaphragm relaxes and moves out
• results in an increase in pressure which pushes air out
• Thorax decreases In volume
Vital capacity
•the maximum volume an individual can inhale and exhale during a deep breath
Tidal volume
The volume of air that is inhaled and exhaled when at rest
Residual volume
•The volume of air always left in the lungs so they don’t collapse
Breathing rate
•The number of breaths taken per minute
-can be worked out by counting the number of breaths
Ventilation rate=tidal volume x breathing rate
Ventilation in fish
Fish swim with their mouth open so that water flows over the gills.
Fish lower their buccal cavity and open their mouth; this increases the volume of the buccal cavity and therefore decreases the pressure. This results in water flowing into the buccal cavity.
Simultaneously, the operculum valve will shut and the operculum cavity (where the gills are located) will expand.
This causes an increase in volume of the operculum cavity, and therefore a decrease in pressure. The fish will then raise the floor of the buccal cavity, forcing the water from the buccal cavity over the gills within the operculum cavity.
Gas exchange in fish
•large surface area-due to many gill filaments and lamelle
•short diffusion pathway-gill lamelle and filaments are very thin and contain capillary’s.
•good blood supply- helps maintain a steep concentration gradient
•gill filaments slow down the flow of water which allows more oxygen to be taken out of it.
Countercurrent exchange system
-Blood flows in opposite directions to water. This way a concentration gradient of oxygen in blood and water is always maintained so diffusion is always taking place
Gas exchange in insects
-insects open and close spiracles using contraction and relaxing of abdominal muscles(sphincters) to allow gas to come in and leave
-has many trachioles resulting in a large surface area for diffusion
-trachioles are one cell thick which allows for a short diffusion pathway.
-sphincters open when cells respire to maintain a steep concentration gradient
Tracheal fluid
-fluid found towards the end of the trachioles which limits the surface area for diffusion but can be withdrawn in times of high oxygen need.
How spirometers take measurements
-the person doing the test uses a mouth piece
-the mouthpiece has one way tube that goes into a container filled with water.
-as the person breathes in and out a trace is drawn on a revolving drum as the pen moves up and down. The tube then goes back around through a container of soda lime to remove the carbon dioxide.
Artery
-carry blood away from the heart
-carry oxygenated blood except for pulmonary artery.
-artery walls contain elastic fibres, smooth muscle and collagen.
-elastin vasoconstricts and dilates the artery
-arterioles link arteries and capillaries
-contain lots of elastin fibres and smooth muscle but not so much collagen.
Vein
-veins carry blood away from cells towards the heart.
-they carry deoxygenated blood apart from the pulmonary vein which carries oxygenated blood from the lungs to the heart.
-low blood pressure compared to arteries and wide lumen.
-walls contain lots of collagen and relatively little elastic fibres and smooth muscle. Contain a thin endothelium.
-venules link the capillaries with the veins.
-majority of veins contain one way valves at intervals which prevents backflow
-the breathing movements of the chest act as a pump which moves blood around,
Capillaries
-Capillaries are microscopic blood vessels that link arterioles with the venules.
-1cell wide so blood cells have to travel through one at a time.
-very wide sa for diffusion of substances into and out of the blood.
-The total cross-sectional area of the capillaries is always greater than the arteriole supplying them so the rate of blood flow falls.
The relatively slow movement of blood through capillaries gives more time for the exchange of materials by diffusion between the blood and the cells.
-The walls are a single endothelial cell thick, giving a very thin layer for diffusion.
