2.2 Cardiovascular and respiratory system Flashcards
Heart
The heart is an organ made of muscle which continually contracts and relaxes to pump blood and oxygen around the body and deliver waste products (carbon dioxide) back to the lungs to be removed. 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.
Arteries
Arteries transport blood away from the heart to the organs.
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 which are used for gas exchange. 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.
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.
Blood
Blood is a tissue made up of plasma, red blood cells, white blood cells and platelets.
Platelets
Platelets clot the blood, fragment of cells that can link together in meshes to stop escape of blood.
Less than 1% of the blood is made up of plasma.
Red blood cells
Function – transports oxygen (and carbon dioxide round the body)
No nucleus (creating a biconcave shape) to create more space for oxygen
Contains haemoglobin which binds to oxygen
Large surface area to maximise oxygen uptake
They travel through capillaries. Red blood cells are larger than the diameter of the capillary maximising contact between the red blood cells and the capillary. Therefore, lots of oxygen is dropped of at the cell.
Once oxygen has been dropped off it picks up carbon dioxide and transports it back to the lungs
45% of the blood is made up of RBC
White blood cells
Function - destroy pathogens
Can change shape to exit blood vessels and chase pathogens.
Large nucleus provides an immunological memory.
Lysosomes containing enzymes to digest engulfed pathogens.
less than 1% of the blood is made up of WBC
Plasma
Function - to transport solutes like glucose, minerals and amino acids
Has proteins in it that can help control the PH.
55% of the blood is plasma.
Adaptations for gas exchange
Large surface area to allow faster diffusion of gases across the surface.
Thin walls to ensure diffusion distances remain short.
Good ventilation with air so that diffusion gradients can be maintained.
Good blood supply (dense capillary network) to maintain a high
concentration gradient so diffusion occurs faster.
Ribs
Ribs are a bone structure that surround and protect the lungs, they also aid breathing moving up and out or down and in.
Intercostal muscles
Muscle between the ribs which control movement, causing inhalation and exhalation.
Diaphragm
Sheet of connective tissue and muscle at the bottom of the thorax that helps that helps to change the volume of the thorax to allow inhalation and exhalation.
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.
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.
Adaptations of the alveoli
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.
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.
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
