Exchange Surfaces Flashcards
Organism with a high metabolic rate tend to be:
Larger organisms
More active organisms
Organisms that need to stay warm
What is metabolic rate?
The amount of energy transferred by that organism within a given period of times.
What are the features of effective exchange surfaces?
Thin barrier: short diffusion distance, barrier must be permeable
Large SA: provides more space for molecules to pass through
Steep conc. gradient: good blood supply and ventilation required
What are the alveolar walls made of?
The alveolar walls are made of squamous epithelium and high consists of flattened cells, one cell thick.
This reduces the diffusion distance
Why are alveoli coated in lung surfactant?
Lung surfactant reduces cohesion between water molecules, preventing the alveoli from collapsing and increasing SA.
Why do alveoli contain elastin fibres?
The elastin fibres allows them to:
Stretch - increasing SA
Recoil - helping to force air out, maintaining concentration gradient
Why are alveoli ventilated?
They are ventilated to constantly supply oxygen and remove carbon dioxide.
This maintains the concentration gradient.
What is the route of an oxygen molecule from the air outside the body into the blood?
Nose/mouth
Trachea
Bronchi
Bronchioles
Alveoli
Capillary
What type of membrane are each of the lungs enclosed in?
Each of the lungs are enclosed in a double membrane.
What is the double membrane enclosing the lungs called?
The pleural membrane
This is the membrane that encloses each lung
What is the space between the two membranes called?
The pleural cavity is the space between the two membranes
What is the pleural cavity filled with?
The pleural cavity is filled with pleural fluid
What is the role of pleural fluid?
Pleural fluid lubricates the lungs.
It also adheres to the outer walls of the lungs to help the thoracic (chest) cavity by water cohesion so that the lungs expand with the chest while breathing.
What are the three main features of the nasal cavity?
Large surface area and good blood supply
Hairy lining
Moist surfaces
Why does the nasal cavity need a large surface area and blood supply?
It needs a large surface area and good blood supply in order to warm the air as it passes into the body
Why does the nasal cavity need a hairy lining?
The hairs in the hair lining trap dust and bacteria in mucus preventing them from reaching the lungs which could cause infection
Why does the nasal cavity need to have moist surfaces?
Moist surfaces in the nasal cavity increase the humidity of the incoming air, this reduces the evaporation of water in the lungs.
What is the function of ciliated epithelial cells?
These cells line the trachea to the bronchi.
Each cells has tiny cilia which sweep mucus,dust and bacteria up and away from the lungs to the mouth where they are swallowed and digested.
What is the function of goblet cells?
Embedded throughout ciliated epithelium and are mucus-producing cells
The mucus they produce traps dust and microorganisms
What is the function of mucous glands?
The mucous glands work with goblet cells in the trachea and bronchi to produce mucus
What is the role of cartilage?
Rings of cartilage line the trachea
and windpipe.
Cartilage is a strong and flexible tissue and is essential in keeping the trachea open. Cartilage is able to move and flex as we breathe.
What is the function of smooth muscle?
Smooth muscle is a muscle that isn’t under conscious control found in the walls of the bronchi and bronchioles
It helps regulate the flow of air into and out of the lungs by dilating when air is needed.
What is the function of elastic fibres?
Elastic fibres are found in the squamous epithelium of the alveolar walls
They allow the tiny alveoli to stretch as they fill with air and recoil to force it out
These elastic abilities of the alveoli are what gives them a large surface area.
What is the function of squamous epithelium?
The squamous epithelium consists of flat, thin cells in the walls of the alveoli
Their thinness means that oxygen and carbon dioxide have a short diffusion pathway during gas exchange.
Where is the heart located?
In between the lungs in the centre of the thorax (chest)
What tissue is the heart mainly made up of?
The heart mainly consists of cardiac muscle tissue which like smooth muscle contracts involuntarily
What is cardiac muscle made up of?
Cardiac muscle is made up of cells that are connected by cytoplasmic bridges. This enable electrical impulses to pass through the tissue.
Explain how the alveoli create a surface for efficient gas exchange.
(5 marks)
Alveolar wall is one cell thick for shorter diffusion pathway
Large number of alveoli increase SA
squamous epithelial cells create short diffusion distance
Elastic to expel air - helps ventilation
(Cells) secrete surfactant to maintain SA
What happens when we breathe in?
Diaphragm contracts and flattens
External intercostal muscles contract, moving the ribcage up and out
Thoracic (chest) volume increases whilst thoracic pressure decreases
Air flows into lungs to equalise pressure difference
What happens when we breathe out?
Diaphragm relaxes and curves up
External intercostal muscles relax moving the ribcage down and in
Thoracic (chest) volume decreases whilst pressure increases
Air flows out of lungs to equalise pressure difference
What is tidal volume?
The volume of air that moves into and out of the lungs with each resting breath
15% of the vital capacity
What is vital lung capacity?
The largest volume of air that can be breathed out
(When strongest inhale is followed by strongest exhale)
What is inspiratory reserve volume?
The inspiratory reserve volume is the maximum volume of air you can inhale.
Whereas the expiratory reserve volume is the maximum volume of air you can force out of your lungs.
What are the adaptations of erythrocytes?
Biconcave shape to increase SA
Large amount of haemoglobin to transport oxygen
No nucleus or organelles to maximise space for haemoglobin
How is oxygen transferred into the blood at the gills of a fish?
Blood and water flow in a countercurrent system with a greater concentration gradient between them at the start of the gill lamellae
What happens during exhalation in mammals?
Ribcage moves down and inwards
External intercostal muscles and the diaphragm relax
Rank the affinity for oxygen out of adult haemoglobin, myoglobin and fetal haemoglobin
1) myoglobin - highest affinity
2) fetal haemoglobin - 2nd highest
3) adult haemoglobin - lowest
Why don’t large multicellular plants need a transport system for carbon dioxide and oxygen?
Plant cells have a low metabolic rate
What creates the ‘lub’ sound in the heart?
The atrioventricular valves closing and blood leaving the ventricles during the start of ventricular systole.
What is the chloride shift?
Hydrogen carbonate ions moving out of red blood cells and chloride ions moving into red blood cells
Why does diastole follow systole in the mammalian heart?
Cardiac muscle takes a short time to repolarise after being stimulated
How are blood vessels adapted to their function?
The walls of the arteries contain a lot of elastic fibres so they can stretch and recoil to maintain blood pressure
The walls of the venules consist of little muscle
Why do small organisms such as amoeba not need a specialised exchange surface?
They have a relatively low metabolic rates
Large S.A : volume ratio
Short diffusion distance so simple diffusion is enough to meet their needs
Why do larger organisms need specialised exchange systems?
They have a high metabolic rate
Small surface area : volume ratio
Larger diffusion distance
What makes up the trachea?
C-shaped rings of cartilage for support
Ciliated epithelium with goblet cells
Smooth muscle so lumen in trachea can contract and dilate
What are the bronchi?
The trachea splits into 2 tubes called bronchi
These split into many smaller tubes called bronchioles
Both bronchi and bronchioles have cartilage within their walls for support
