The Circulatory System Flashcards
What is the composition of blood?
Plasma: the liquid part, making up approximately 55% of the blood volume.
Formed Elements: the non-liquid part, making up 45% of the blood volume and consisting of erythrocytes (red blood cells), leucocytes (white blood cells) and thrombocytes (platelets).
What is plasma?
A mixture of water with dissolved substances such as sugar and salts. Plasma transports the components of the blood, including nutrients, wastes, hormones, proteins and antibodies, throughout the body.
What are erythrocytes?
One of the formed elements of the blood containing haemoglobin-
- Account for 40-45% of the volume of blood, (haematocrit).
- Biconcave shape.
- Do not contain a nucleus which increases their flexibility and, hence, their ability to move blood through blood vessels.
- Life span of 120 days on average.
- Function is the transport oxygen from the lungs to the cells throughout the body.
What is the haematocrit?
The ratio of red blood cells to the total volume of blood.
What are leucocytes?
One of the blood cells; it contains a nucleus, but no haemoglobin. They play an important role in protecting the body from infection. They make up 1% of the blood and are larger than erythrocytes.
Neutrophils.
Contain enzymes to digest pathogens.
Monocytes.
Form other cells, including macrophages that engulf pathogens and aged or damaged cells by phagocytosis.
Lymphocytes
Are involved in the immune repose.
Basophils.
Are responsible for allergic reactions, producing heparin and histamine to defend the body against parasites and bacteria.
Eosinophils.
Also lead to inflammatory responses; they respond to larger parasites such as worms.
What are thrombocytes?
One of the formed elements of blood; a fragment of cytoplasm enclosed in a membrane but lacking a nucleus; also called a platelet. When a blood vessel is injured, the platelets adhere to the lining and form a scaffold for the coagulation of blood to form a clot.
How is oxygen carried in the blood (percentages)?
3% of oxygen is carried in the blood plasma.
97% is carried in combination with haemoglobin molecules, only found in red blood cells.
How is oxygen transported in the blood?
Oxygen combines with haemoglobin when the oxygen concentration is relatively high. This occurs in the capillaries in the lungs, where oxygen diffuses from the air in the alveoli. Oxyhaemoglobin breaks down to haemoglobin and oxygen when the concentration of oxygen is relatively low. As the cells of the body are continually using oxygen, tissue fluids around the cells have a relatively low oxygen concentration. Therefore, when the red blood cells flow through the capillaries between the body cells, they give up their oxygen, which diffuses into the tissue fluid and then into the cells.
Why are red blood cells well suited to their function of oxygen transport?
- Contain haemoglobin, which is able to combine with oxygen.
- Have no nucleus, so there is more room for haemoglobin molecules.
- Are shaped like biconcave discs- the biconcave centre increases the surface area for oxygen exchange and the thicker edges give a large volume that allows room for the haemoglobin molecules.
How is carbon dioxide carried in the blood (percentages)?
Approximately 7-8% is dissolved in the plasma and carried in solution.
Another 22% or so combines with the globin part of the haemoglobin molecule to form a compound called carbaminohaemoglobin.
The remainder, about 70%, is carried in the plasma as bicarbonate ions, HCO3-.
How is carbon dioxide transported in the blood?
As the blood is flowing through the capillaries between the body cells, carbon dioxide diffuses into the plasma due to the difference in carbon dioxide concentration. Some carbon dioxide dissolves in the plasma, some combines with haemoglobin, but most reacts with water to form carbonic acids (H2CO3). Carbonic acid then ionises into hydrogen ions and bicarbonate ions.
In the alveoli, the carbon dioxide dissolved in the plasma diffuses out of the blood into the air in the alveolus. The carbaminohaemoglobin breaks down, and the carbon dioxide molecules released also diffuse into the alveolus. Hydrogen ions and bicarbonate ions recombine to form carbonic acid, which then breaks down under enzyme action into water and carbon dioxide. This carbon dioxide also diffuses into the alveolus.
Explain how nutrients and wastes are transported in the blood.
Nutrients and wastes are dissolved and transported in the blood plasma.
Nutrients (the essential elements and molecules that are obtained from the food we eat) include:
- Inorganic nutrients (transported as ions)- sodium ions, calcium ions, potassium ion, chloride ions and iodide ions.
- Organic: glucose, vitamins, amino acids, fatty acids and glycerol.
Metabolic wastes are substances produced by the cells that cannot be used and that would be harmful if allowed to accumulate.
Organic wastes that are transported in solution in blood plasma- urea, creatinine and uric acid.
Blood clotting minimises blood loss from broken vessels and prevents the entry of micro-organisms. List the steps of blood clotting.
1- Vasoconstriction.
2- Platelet plug.
3- Coagulation.
Explain vasoconstriction.
The muscles in the walls of the small arteries that have been injured or broken constrict immediately to reduce blood flow and therefore, blood loss.
Explain the platelet plug.
Damage to internal walls of blood vessels create a rough surface to which platelets ‘stick’.
Sticking platelets attract others so a ‘plug’ is built at the injury site to prevent blood loss.
The platelets release substances that act as vasoconstrictors, which enhance and prolong the constriction of the damages vessels.
Explain coagulation.
For more serious injuries. Coagulation is the process of blood becoming gel-like, forming a blood clot.
This process involves a large number of clotting factors, that are present in blood plasma. The complex series of reactions results in the formation of threads and an insoluble protein called fibrin. The fibrin forms a mesh that traps blood cells, platelets, and plasma. This is the blood clot. The treads stick to the damaged blood vessel and hold the clot in position.
Explain clot retraction.
Clot retraction is the contraction of the fibrous threads of a blood clot. As this occurs, a fluid known as serum is squeezed out. The clot then dries, forming a scar over the wound that prevents the entry of infecting microorganisms.
What is the heart?
The pump that pushes blood around the body, located between the two lungs in the mediastinum, behind and slightly left of the sternum.
What is the name of the membrane which encloses the heart.
The pericardium is the membrane that encloses the heart. It holds the heart in place, but also allows the heart to move as it beats and prevents in from stretching.
What is the wall of the heart made up of?
Cardiac muscle.
What is the name of the wall that separates the left and right sides of the heart?
The septum.
Where does the blood come from that goes into each side of the heart?
The right side of the heart collects blood from the body and pumps it to the lungs.
The left side of the heart receives blood from the lungs and pumps it to the rest of the body.
List the four chambers of the heart.
The right atrium receives blood from the body and passes it to the right ventricle.
The right ventricle pumps blood to the lungs.
The left atrium receives blood from the lungs and passes it to the left ventricle.
The left ventricle pumps blood to the body.
What is the purpose of valves in the heart?
They ensure that blood can only flow in one direction, preventing the back flow of blood.
What are the atrioventricular valves?
Valves that ensure the blood flows through the heart in one direction only.
Location: Between the atria and the ventricles.
Structure: Flaps of thin tissue with the edges held by tendons (chordae tendineae), that attach to the heart on papillary muscles.
Function: When the ventricles contract, the blood catches behind the flaps and they billow out like a parachute, sealing off the opening between the atria and the ventricles. Blood must then leave the heart through the arteries and not flow back into the atria.
What are semilunar valves?
Vales preventing blood from flowing back into the ventricles.
Location: At the start of the aorta and pulmonary vein..
Structure: each valve has three cusps.
Function: When the blood flows into the artery, the cusps are pressed flat against the artery wall.
When the blood tries to flow back into the ventricle, the cusps fill out and seal off the artery, ensuring blood only flows in one direction.
What creates the ‘lub-dub’ sound of the heart?
It is the closing of the valves that gives the heartbeats their characteristic ‘lub-dub’ sound. The two sounds are due to the closing of the atrioventricular and then semilunar valve.
What is the name of the atrioventricular valve located between the right atrium and the right ventricle?
The tricuspid valve.
