Circulatory System Flashcards
What is the circulatory system?
The circulatory system is the link between the cells in teh body which have certain requirements, and the environment outside the body, which supplied those requirements.
What are the functions of blood?
- Transporting oxygen and nutrients to all cells of the body.
- Transport Carbon Dioxide and other waste products away from the cells.
- Transport hormones to the cells.
- Maintain pH of bodily fluids.
- Distribute heat, maintain temperature of body.
What is blood composed of?
- Plasma: Liquid part (55% of volume)
- Formed Elements: Non Liquid part, consists of erythrocytes, leucocytes, and thrombocytes (~45%)
What is Plasma and what is its function?
Plasma is a mixture of water with dissolved substances such as sugar and salts.
Function:
- Transport components of blood, including cells, nutrients, wastes, hormones proteins, and antibodies throughout the body.
Erythrocytes:
- Are the most abundant cells in teh blood, and account for approximately 40-45% of its volume. This percentage is known as the haematocrit.
- The Erythrocytes are biconcave shaped.
- They have no nucleus, increasing flexibility and hence the ability to move through blood vessels.
- However, having no nucleus limits its life span to 120 days on average.
- Transport oxygen from the lungs to the cells throughout the body.
Leucocytes:
- White blood cells.
- Protect the body from infection.
- Are larger than erythrocytes.
Thrombocytes:
Are small fragments of cells. When a blood vessel is injured, they adhere to the lining, and form a scaffold for the coagulation of blood to form a clot.
Transport of Oxygen:
- Only 3% carried in solution through plasma (oxygen is not very soluble in water).
- The other 97% is carried in haemoglobin, where they both combine to form the compound Oxyhemoglobin.
- The combination of oxygen and haemoglobin is said to be a weak one, because they can break down easily and release the oxygen to the cells of the body.
- Haemoglobin increases the oxygen carrying capacity of blood by 60 or 70 times.
- Oxygen and haemoglobin combine when oxygen concentration is high.
- This occurs in the capillaries in the lungs, surrounding the alveoli where oxygen diffuses into the blood.
- Oxygen and haemoglobin break down when oxygen concentration in the body is low. The red blood cells flowing in the capillaries between the body cells give up their oxygen to the cells which require oxygen.
- This oxygen diffuses into the tissue fluid, and then into the cells.
Transport of Carbon Dioxide:
- Approximately 7-8% is dissolved in the plasma and carried in solution.
- Another 22% or so combines with the globin part of haemoglobin molecule to form a compound called carbaminohaemoglobin.
- The remaining ~70% is carried in the plasma in the form of bicarbonate ions, HCO3-.
- Blood flow through capillaries between body cells, CO2 diffuses into plasma due to difference in CO2 concentration.
- Some dissolve in plasma, some combine with haemoglobin. But most react with water to form carbonic acid (H2CO3), which then ionises into hydrogen ions and bicarbonate ions.
CO2 + H2O -> <- H2CO3 -><- H+ + HCO3- - In air sacs of alveoli, CO2 diffuses out of blood into the air in the alveolus.
- Carbaminohaemoglobin breaks down and CO2 molecules releases also diffuse into the alveolus.
- Hydrogen ions and bicarbonate ions recombine to form carbonix acid which then breaks down under enzyme action into water and carbon dioxide. This carbon dioxide also diffuses into the alveolus.
Transport of Nutrients and Wastes
- Nutrients and wastes are dissolved and transported in the blood plasma.
~ Nutrients are essential molecules and elements that are obtained from the food we eat. They can be inorganic or organic.
-{ Inorganic nutrients are transported as ions. They include Potassium Ions, Calcium ions, Chloride ions, and sodium ions.
-{ Organic Nutrients are dissolved in the blood plasma. They include glucose, vitamins, amino acids, fatty acids, and glycerol.
~ Wastes or metabolic wastes are substances produced by the cells that cannot be used and would be harmful if the accumulate.
~ The most important organic wastes that are transported in solution in the blood plasma are urea, creatinine, and uric acid.
What are the atriums and ventricles?
The atrium receives blood from the body and the lungs, while the ventricles are the pumping chambers and pump blood to the rest of the body and the lungs.
Valves:
- Control the direction of blood flow.
- The atrioventricular valves are held in position by strong tendons, the chordae tendinae.
- The sounds are a result from the valves snapping shut.
Valves in the heart: - Pulmonic Semilunar valves.
- Tricuspid Atrioventricular Valve.
- Bicuspid Atrioventricular Valve.
- Artic Semilunar Valve.
Blood Vessels:
Arteries: Muscular blood vessels that carry blood away from the heart.
Arterioles: Smaller arteries that direct blood flow to various tissues.
Veins: Blood vessels that carry blood towards the heart.
Venules: Smaller veins.
Capillaries: Are microscopic blood vessels that connect venules and arterioles. They enable the exchange of substances between blood and surrounding tissues.
Structure of Blood Vessels
Veins and arteries are made up of three layers (tunicae):
Tunica Interna: Present in all blood vessels (arteries, capillaries, veins).
Tunica Media: Well developed in arteries, none in capillaries, and relatively thin in veins.
Tunica Externa: Relatively thin in arteries, none in capillaries, well developed in veins.
Arteries have a relatively thick muscular wall and a small lumen, however, veins have a thin wall but a large lumen.
Structure of Veins and Arteries:
Elastic Walls - Present in arteries, allow the contraction and expansion due to changes in blood pressure.
Muscular Walls - Present in arteries: Allows vasodilation and vasoconstriction to control blood flow.
Thickness of Walls - thick in arteries, thin in veins: Resist the chance of bursting under high pressure of blood.
Valves Present: Present in Veins: Prevent the back flow of blood in the veins.
Lumen Size: Small in arteries, large in veins: Narrow lumen size maintain the high blood pressure in the arteries.
