1.2 Cardio-respiratory system Flashcards
Trachea
Windpipe that connects the mouth and the nose to the lungs, lined with goblet cells to produce mucus and ciliated epithelial cells which move the mucus up and down.
Bronchus
Large tubes branching of the trachea with one bronchus for each lung, also lined with goblet cells and ciliated epithelial cells.
Bronchioles
The bronchi split to form smaller tubes called bronchioles in the lungs connected to alveoli.
Alveoli
Tiny moist air sacs where gas exchange takes place, each alveoli is covered in capillaries.
Gas exchange
The term gas exchange refers to the exchange of gases between the air and the blood; this occurs in the alveoli of the lungs.
Oxygen enters the blood from the air.
Carbon dioxide leaves the blood and enters the air.
Gas exchange occurs by the process of diffusion.
Adaptations of the alveoli
Large surface area - There are many alveoli within the lungs, resulting in a large surface area across which diffusion can occur.
Short diffusion distance - Alveoli walls and capillary walls are one cell thick, reducing the diffusion pathway for gases.
The capillary vessels are located directly next to the alveoli to minimise the diffusion pathway.
Many capillaries - This means that the alveoli have a good blood supply, maintaining oxygen and carbon dioxide concentration gradients.
The blood arriving at the alveoli is high in carbon dioxide in comparison to the alveoli, so carbon dioxide diffuses out of the blood and into the alveoli.
The blood is low in oxygen in comparison to the alveoli, so oxygen diffuses into the blood from the alveoli.
High oxygen concentration - The process of ventilation ensures that the air in the alveoli always contains a higher concentration of oxygen than the blood; this means that oxygen diffuses into the blood.
Layer of moisture - Gases in the air dissolve in this layer on the surface of the alveoli, aiding diffusion.
Haemoglobin
After diffusing into the blood oxygen binds to haemoglobin within red blood cells to form oxyhaemoglobin:
oxygen + haemoglobin → oxyhaemoglobin
Haemoglobin can also bind to carbon dioxide, aiding the transport of carbon dioxide to the lungs.
Arteries
Arteries transport blood from the heart to the organs. They transport blood away from the heart.
Artery walls have thick layers of muscle. This makes them strong and able to cope with the high pressure at which blood is pumped out by the heart.
The walls have elastic fibres, allowing them to stretch and spring back (recoil).
Capillaries
Arteries branch into much smaller vessels, called capillaries. Capillaries have thin walls and pass very close to the body cells. Capillaries are the smallest blood vessel at around 7-10um (micrometres) in diameter. This means that red blood cells must pass through the capillaries 1 at a time. They are also 1 cell thick which means oxygen can diffuse into the system faster. Their function is gas exchange.
Veins
Veins form when capillaries join up after passing through the body. They transport blood back to the heart.
The walls are thinner than those found in the arteries as the blood is at a lower pressure.
Low pressure hinders blood flow. This means that veins have a wider cross-section through which blood can flow to counteract this.
Veins have valves to prevent the backflow of blood.
Blood flow around the body
Blood from the body contains very little oxygen and is transported to the right atrium via the veena cava. The blood passes through the tricuspid valve into the right ventricle. Blood is then pumped from the right ventricle to the lungs via the pulmonary artery to become oxygenated. Oxygenated blood from the lungs enters the heart at the left atrium via the pulmonary vein. It then passes through the bicuspid valve and enters the left ventricle where it is then pumped to the rest of the body via the aorta.
Heart
The heart is made of muscle. The heart muscle continually contracts and relaxes. It uses a lot of energy. The heart muscle receives oxygen and glucose for respiration from the blood brought by the coronary artery.
The heart has two pumps (a double circulation) that beat together about 70 times every minute of every day. a double circulatory system is one in which blood flows through the heart twice and is pumped twice, once through the lungs and again around the body.
Each pump has an upper chamber (atrium) that receives blood and a lower chamber (ventricle) that pumps out blood. Both atria fill and pump blood out at the same time, as do both ventricles. The natural resting heart rate is controlled by a group of cells located in the right atrium that act as a pacemaker. there are two ventricles so that oxygenated and deoxygenated blood don’t mix.
Cardiac cycle
The cardiac cycle is All of the events taking place within a single heartbeat.
Diastole - The heart muscle relaxes and the chambers fill with blood
Systole - The muscle walls of the heart chambers contract and blood is forced out.
Atrial systole forces blood out of the atria and into the ventricles
Ventricular systole forces blood out of the ventricles and into the arteries
Valves
Valves inside the heart prevent the backflow of blood between the ventricles and the atria, and between the arteries and the ventricles.
Valves open due to pressure differences between the different areas of the heart.
Cardiac output
The volume of blood that is pumped by the heart every minute.
Cardiac output (Q) = stroke volume (SV) x heart rate (HR)
Stroke volume is the volume of blood pumped by the heart with each beat
Heart rate is the number of beats per minute
Inhaling
When we inhale, the intercostal muscles between the ribs contract, this moves the ribs up and out, the diaphragm muscle contracts and moves down and the volume of air inside the chest increases. This decreases the pressure inside the chest and the air pressure outside the chest is higher so air enters the lungs.
Exhaling
When we exhale, the intercostal muscles between the ribs relax, this moves the ribs down and in , the diaphragm muscle relaxes and moves up and the volume of air inside the chest decreases. This increases the pressure inside the chest and the air pressure outside the chest is now lower so air leaves the lungs.
Exercise and breathing
During exercise the supply of oxygen to the body needs to increase; this is aided by changes to the ventilation process:
During inhalation, The volume of the chest cavity is increased further by the action of pectoral and sternocleidomastoid muscles; this allows more air to be drawn into the lungs.
During exhalation, The rib cage is pulled down and in more rapidly by the contraction of abdominal muscles; this forces more air out of the lungs
This differs from exhalation at rest, which is an entirely passive process
Spirometer
An individual’s breathing can be measured and analysed using a piece of equipment called a spirometer.
The individual breathes via a tube that is connected to a floating box of air.
The tube is also connected to a canister of a chemical called soda-lime which absorbs exhaled carbon dioxide; this allows the spirometer to record only the changing volumes of oxygen.
An inward breath removes air from the box, causing it to sink lower into the water.
Breathing outputs air into the box and causes it to rise up in the water.
A metal arm with a pen is attached to the side of the box, and this arm draws a trace on a rotating drum as the individual breathes, producing a spirometer trace.
Spirometer trace
Tidal volume - The volume of air breathed in and out with each normal breath
At rest, tidal volume is approximately 500ml.
Inspiratory reserve volume - The difference between the tidal volume and the total volume of air breathed in during a deep inhalation.
Expiratory reserve volume - The difference between the tidal volume and the total volume of air breathed out during an active exhalation.
Residual volume - The volume of air that remains in the lungs even after a maximal exhalation.
