Module 3: Exchange And Transport

Question 1

How is the structure of the trachea suited for its functions?

Answer 1

It’s lined with incomplete rings of cartilage for strength to stop it from collapsing. The rings are incomplete at the back to prevent rubbing with the oesophagus and to allow the trachea to slightly expand.
The walls have many goblet cells that produce mucus to catch dust and prevent it from damaging the lungs. They also have ciliated epithelial cells with many cilia that move in a rhythmic motion to keep the mucus away from the lungs.

Question 2

How does the structure of the bronchioles help their functions?

Answer 2

The walls have no cartilage(unlike the trachea) and instead are made of smooth muscle. The muscle can contract which allows the airways of the bronchiole to constrict and control the airflow to help with gas exchange.

Question 3

How is the structure of the alveoli suited for their functions?

Answer 3

The alveoli each have a large surface area because of their specific shape and are very plentiful. This allows more gas to diffuse into them to increase diffusion rate. The walls of the alveoli are only one cell thick so the gas only needs to diffuse through 2 cells(the wall of the alveolus and the wall of the capillary which is also one cell thick) to get into the red blood cell. The alveoli are made of elastic fibres which allow the alveoli to expand and increase their surface area further.

Question 4

What are the anatomical changes in the respiratory system during inhalation?

Answer 4

The diaphragm muscles contract-the diaphragm flattens and moves down
The external intercostal muscles contract-the rib cage moves up and out

Question 5

What are the volume changes in the respiratory system during inhalation?

Answer 5

The volume of the thorax/thoracic cavity increases because of the diaphragm flattening

Question 6

What are the pressure changes in the respiratory system during inhalation?

Answer 6

The pressure in the thorax/thoracic cavity decreases because the volume has increased but the amount of air hasn’t. This means the pressure of the thorax is below the pressure of the atmosphere

Question 7

What is tidal volume of air?

Answer 7

The volume of air that moves in and out of the lungs when breathing normally

Question 8

What is vital capacity?

Answer 8

The volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath

Question 9

What is the inspiratory reserve volume?

Answer 9

The volume of air you can breathe in after a normal inhalation

Question 10

What is expiratory reserve volume?

Answer 10

The extra amount of volume you can force out of your lungs after a normal exhalation

Question 11

What is residual volume?

Answer 11

The volume of air that is left even after exhaling your expiratory reserve volume

Question 12

How does air enter a locust’s body?

Answer 12

It enters through spiracles, which are openings in the locust. When the spiracles are open, gas can enter but water is also lost so the spiracles are closed by sphincter muscles

Question 13

How are tracheae in a locust suited for gas exchange?

Answer 13

They are lined with chitin. Chitin is impermeable which prevents gas loss in the tracheae and also strengthens the tracheae to stop them from collapsing.

Question 14

How does tracheal fluid help gas exchange in locusts and how does a locust get oxygen during high oxygen demands?

Answer 14

Tracheal fluid is found in the tracheoles. It is permeable and gives a large surface area to increase diffusion rate and therefore helps gas exchange. When the locust has high oxygen demands, the build up of carbon dioxide will produce lactic acid, which makes the tracheal fluid withdraw by osmosis and increase the surface area even more

Question 15

What is the process of gas exchange and water flow in a fish? Note whether each change is anatomical, volume, pressure or water flow

Answer 15

1. Mouth of fish opens, which causes buccal cavity floor to lower(A)
2. Volume inside buccal cavity increases(V)
3. Pressure inside buccal cavity decreases(P) and water rushes in(F)
4. Opercular valve shuts which expands opercular cavity which contains the gills(A)
5. Volume inside opercular cavity increases(V) which decreases pressure in the opercular cavity(P)
6. Buccal cavity moves up(A) which increases the pressure in the buccal cavity and water rushes over the gills, where gas is exchanged(F)

Question 16

What is a double closed circulatory system?

Answer 16

A system in which blood travels through and is pumped by the heart twice to complete a full circuit: once to the lungs(pulmonary circulation) and once to the rest of the body(systemic circulation)

Question 17

How is the structure of the arteries/arterioles linked to their function?

Answer 17

They have a narrow lumen to increase pressure
They have a thick tunica media of smooth muscle and elastic fibres. The muscle can contract to narrow the walls, and the elastic fibres can allow the vessel to withstand the blood pushing against the walls
They have a thick tunica externa made of collagen. This prevents the blood vessels from bursting

Question 18

How is the structure of the veins and venules suited towards their function?

Answer 18

They have a wide lumen to transport more blood
They have valves to prevent backflow
They have thinner layers of smooth muscle and collagen as the blood is at a lower pressure

Question 19

How is the structure of capillaries suited towards their function?

Answer 19

They are a single layer of endothelial cells, which provides a short diffusion distance. They are in very high numbers in capillary beds to reduce the pressure on each individual vessel to prevent bursting

Question 20

What are the main components of blood?

Answer 20

Plasma, platelets, red blood cells and white blood cells

Question 21

What is plasma’s function and structure?

Answer 21

It is a yellow liquid mainly made out of water. It is the part of the blood that carries most of the components, including mineral ions, hormones and heat energy

Question 22

What is the process of tissue fluid leaving and exiting the capilllaries

Answer 22

When oxygenated blood reaches the arterioles and capillaries, the hydrostatic pressure (caused by the heart contractions) pushing the fluid outwards is much greater than the oncotic pressure (caused by the plasma proteins) pushing the fluid inwards, this forces the liquid parts of the blood outside of the capillaries, which is how the substances leave the blood and enter the tissues. The liquid that leaves the capillaries is called tissue fluid. It has the same structure as blood but without any plasma proteins, red blood cells or platelets. Once the tissue fluid reaches the end of the capillaries the hydrostatic pressure decreases to the point where it’s lower than the oncotic pressure and 90% of the tissue fluid is absorbed back into the capillaries and blood. The 10% left becomes lymph and enters the lymph capillaries

Question 23

What is the process of the electrical control of the heart?

Answer 23

1. The sino-atrial node sends an electrical impulse across the atria to make them contract and push blood into the ventricles
2. To prevent those impulses from making the ventricles contract downwards and too early, there is a layer of non-conductive tissue
3. Right underneath the non-conductive tissue, the atrio-ventricular node sends impulses down the septum. These impulses are in the form of Purkyne fibres and are known as the bundle of His
4. When the bundle of His reach the apex of the heart, the Purkyne fibres split to surround the heart and cause the ventricles to contract
   This process is myogenic as the heart initiates it itself. The movement of impulses is known as a “wave of electrical excitation”

Question 24

What are the 5 waves of an ecg?

Answer 24

The P wave is where atrial depolarisation happens. The QRS complex is where ventricular depolarisation happens. The T wave is where ventricular repolarisation happens

Question 25

What are 4 abnormal ecg results that could affect a person’s health?

Answer 25

Tachycardia is when the heart beats too fast so the atria don’t have enough time to fill up with blood. Bradycardia is when the heart beats too slow so the blood doesn’t get pumped fast enough. Atrial fibrillation is when the atria don’t contract properly so blood doesn’t get pumped fast enough. Ectopic heartbeats are when there are extra heartbeats out of rhythm(these aren’t as serious unless they happen regularly)

Question 26

What is the process of cooperative binding between Hb and O2?

Answer 26

1. An O2 molecule combines with the first haem group
2. This causes a conformational change in the shape of the Haemoglobin molecule which “stabilises” the other subunits
3. The uptake of the O2 molecule is made easier
4. Further structural alteration after the uptake of each O2 molecule amplifies the effect more each time

Question 27

What is the structure and function of haemoglobin?

Answer 27

It is a globular protein with 4 subunits, each containing a polypeptide and a haem group. The haem group consists of an iron 2+ion which has an affinity with oxygen so it can reversibly bind to be transported

Question 28

What happens to the 95% of carbon dioxide that dissolves into the red blood cells?

Answer 28

10-20% of it binds to aminos in the Haemoglobin to make carboaminohaemoglobin. The other 75-85% firstly binds with water(using the help of a carbonic anhydrase enzyme) to form carbonic acid, which then dissociates into hydrogen ions and hydrogencarbonate ions. The positive hydrogen ions are removed by buffers such as the haemoglobin(which would form Haemoglobinic acid) and the hydrogencarbonate ions dissolve out of the cell down the concentration gradient(as there is a higher concentration of negative ions in the cell) and they are replaced by the chloride shift so the cell doesn’t become too positively charged

Question 29

What is the effect of carbon dioxide on oxygen transport?

Answer 29

Carbon dioxide in the red blood cells forms carbonic acid which dissociates to form hydrogen ions. This decreases the pH of the cell and when they are absorbed by the Hb, it changes the tertiary structure of the Hb which causes them to release oxygen