ANSWERS

1. What is another name for the circulatory system?
   The blood-vascular or cardiovascular system.
2. Name 2 other systems that are a part of the circulatory system?
   • Immune system.
   • Lymphatic system.
     NB. These systems each have their own module later in the chapter.
3. What is meant by the pulmonary circulation?
   The system that takes deoxygenated blood from the heart through the lungs, where it is oxygenated, and then returns it to the heart.
4. What is meant by the systemic circulation?
   This system takes oxygenated blood from the heart to the rest of the body enabling the oxygen to be used by the tissues. It then returns the deoxygenated blood to the heart.
5. What is the collective name of the large vessels that carry blood away from the heart?
   Arteries.
6. What is the collective name of the very small, thin-walled blood vessels that lie within the tissues and allow oxygen exchange?
   Capillaries.
7. What is the correct name for capillary bleeding?
   Petechial haemorrhage.
8. What is the difference between an artery and an arteriole?
   Arteries are larger than arterioles and carry blood away from the heart. Arterioles are located within the organs to which they supply blood.
9. What is the difference between a vein and a venule?
   Veins are large, thin-walled blood vessels that carry blood towards the heart, whilst a venule is a small vein within an organ receiving blood from the capillary bed.
10. What structures are present in veins but not in arteries?
    Valves. These prevent a back flow of blood from the heart.
11. List the 3 arteries that possess "end arteries" rather than a capillary bed.
    • Brain.
    • Heart.
    • Kidneys.
12. Give 1 advantage and 1 disadvantage of end arteries over a capillary bed.
    • Advantage - protection against sudden drops in blood pressure.
    • Disadvantage - obstruction of a vessel (e.g. a blood clot) will cause the death of the tissue supplied by that vessel.
13. List 8 functions of the blood.
    • Transport of oxygen to the tissues.
    • Transport of carbon dioxide away from the tissues.
    • Transport of waste from the tissues to the kidneys for excretion.
    • Regulation of body temperature via the distribution of heat throughout the body.
    • Control of haemorrhage via the clotting mechanism.
    • Transport of chemical messengers (hormones) & catalysts (enzymes).
    • Prevention of infection via the transport of antibodies and antitoxins.
    • Maintenance of the correct pH of the body tissues.
14. What is the pH of blood?
    7.35.
15. What percentage of the body weight is comprised of blood?
    Approximately 7%.
16. State 2 ways in which arterial blood differs from venous blood.
    • Arterial blood is a brighter red colour than venous blood due to the greater percentage of oxygen present.
    • The pH of arterial blood is higher than in venous blood due to the fact that venous blood contains more carbon dioxide and is thus more acidic.
17. What is the name of the straw coloured fluid in which the blood cells (corpuscles) are suspended?
    Plasma.
18. List the 6 components of plasma.
    • Water.
    • Mineral salts (sodium, chloride, potassium, calcium, phosphate & carbonate).
    • Plasma proteins (albumin, globulin, fibrinogen & prothrombin).
    • Foodstuffs (end products of digestion i.e. amino acids, fatty acids & glucose).
    • Gases (in solution).
    • Waste products (urea & creatinine).
19. List the 3 main types of blood cell.
    • Erythrocytes (red blood cells).
    • Leucocytes (white blood cells).
    • Platelets (fragments of white blood cells).
20. What is the main function of the erythrocytes?
    The transport of oxygen via an iron-containing protein called haemoglobin.
21. List 3 immature forms of red blood cell.
    • Erythroblast.
    • Normoblast.
    • Reticulocyte.
22. List 4 properties of adult red blood cells.
    • Do not possess a nucleus.
    • Approx 7 micrometers in diameter.
    • Biconcave disc shape.
    • Live for approx 120 days.
23. What is the name of the substance secreted by the kidney in response to low oxygen levels within the kidneys?
    Erythropoietin factor (erythrogenin). This converts an inactive plasma protein to erythropoietin, which stimulates the bone marrow to produce more erythrocytes.
24. In adult animals, erythrocytes are only produced by the bone marrow. In the foetus however, they are also produced elsewhere. State the locations.
    • Liver.
    • Spleen.
25. Where in the body are spent erythrocytes broken down?
    • Spleen.
    • Lymph nodes.
26. What is another name for the granulocytes?
    Polymorphonuclear leucocytes.
27. What are the 2 main groups of white cells?
    • Granulocytes - neutrophils, basophils & eosinophils.
    • Agranulocytes - lymphocytes & monocytes.
28. What is the name of the tissue from which all the granulocytes and monocytes are produced?
    Myeloid tissue.
29. Briefly state the function of the following cell types: neutrophils, basophils and eosinophils.
    • Neutrophils - phagocytosis.
    • Basophils - heparin and histamine production.
    • Eosinophils - fighting parasitic infestation.
30. Briefly describe the function of the following cell types: lymphocytes and monocytes.
    • Lymphocytes - concerned with immunity.
    • Monocytes - phagocytosis.
31. What is another name for the platelets?
    Thrombocytes.
32. What is the name of the type of cell from which platelets are derived?
    Megakayocytes.
33. Briefly describe the 4 main stages involved in the formation of a blood clot.
    • Platelets stick to the damaged walls of the blood vessel.
    • Broken platelets release thromboplastin.
    • The plasma protein prothrombin reacts with thromboplastin and calcium to form thrombin.
    • Thrombin acts on another plasma protein called fibrinogen to produce insoluble fibrin fibres.
    • The fibrin fibres stick to the platelets forming a firm clot.
34. What is the difference between serum and plasma?
    Serum is simply plasma from which the clotting agents have been removed.
35. Which of the fat-soluble vitamins is required for the manufacture of prothrombin?
    Vitamin K.
36. What is an anticoagulant?
    A substance that prevents blood from clotting. Heparin is naturally present in the blood, but can also be found in the heparinised blood tubes used for the preservation of samples for biochemistry.
37. How many chambers does the heart possess?
    4; the right and left atrium, and the right and left ventricles.
38. Define the following: pericardium and myocardium.
    • Pericardium - the double layer of membrane covering the heart (the inner layer is called the serous pericardium, whilst the outer layer is the fibrous pericardium).
    • Myocardium - the heart muscle.
39. The valves of the heart prevent the back-flow of blood and consist of fibrous flaps called cusps. Can you name the valves of the heart and state the amount of cusps possessed by each?
    • Triscupid valve (R atrio-ventricular) - 3 cusps; as its name implies, this valve is located between the right atrium and right ventricle.
    • Mitral valve (L atrio-ventricular) - 2 cusps; as its name implies, this valve is located between the left atrium and left ventricle.
    • Aortic valve - 3 cusps; this valve is located between the left ventricle and the aorta.
    • Pulmonary valve - 3 cusps; this valve is located between the right ventricle and the pulmonary artery.
40. Name the structures responsible for the restriction of the movement of the atrio-ventricular valves.
    Chordae tendinae.
41. List the 5 structures that contribute to the conduction mechanism of the heart (this allows rhythmic contraction without a constant nerve supply).
    • Sinu-atrial node (SA node) - this is an area of specialised heart muscle from where the impulse for a wave of muscle contraction starts and spreads across the atria.
    • Atrio-ventricular node (AV node) - the AV node is activated by the impulse from the SA node and passes the impulse down the bundle of His.
    • Atrio-ventricular bundle (bundle of His) - this transports the impulse to the apex of the heart.
    • Fibrous plate - this separates the muscle of the atria and ventricles so that there is only one electrical connection between them (at the top of the inter-ventricular septum).
    • Purkinje fibres - these transmit the impulse via a network of fibres spread out over the ventricles.
42. Define systole and diastole.
    • Systole - the period of contraction within the cardiac cycle.
    • Diastole - the period of relaxation within the cardiac cycle.
43. What is meant by the pulse?
    The pulse is the local rhythmic expansion of an artery, which corresponds to each contraction of the left ventricle. When taking the pulse, the rate, strength, rhythm and character should all be noted. The femoral artery is an ideal pulse point in the dog.
44. What is the name given to the strong, jerky pulse often associated with valvular insufficiency or congenital heart defects such as ductus arteriosus?
    Water hammer pulse.
45. What is mediate auscultation?
    Listening to the sounds made by internal organs using a stethoscope. The heart is often examined by means of mediate auscultation.
46. Clinical examination of a patient with a suspected heart problem often begins with mediate auscultation. What other instruments or equipment might be useful in aiding the diagnosis?
    • Scales - weight is important since obesity often makes heart conditions worse.
    • ECG (electrocardiogram machine) - this records the electrical potential of the heart.
    • X-Ray machine - radiographs may prove diagnostic.
    • Blood pressure monitor - a measure of the force at which blood is transported through the arteries.
47. When listening to the heart, you will hear a "lub-dup" sound. What is responsible for this?
    • The "lub" sound is made by the contraction of the ventricles and closure of the atrioventricular valves.
    • The "dup" sound is made by the closure of the aortic and pulmonary valves.
48. State the normal heart rate for the cat and dog.
    • Cat - 110 to 180 bpm.
    • Dog - 60 to 180 bpm (the smaller the dog, the faster the heart rate tends to be).
      Remember that nervous or stressed animals may have a higher than usual heart rate.
49. What is the term used to describe a higher than normal heart rate?
    Tachycardia.
50. What is the term used to describe a lower than normal heart rate?
    Bradycardia.
51. What is an arrhythmia?
    A variation from the normal rhythm of the heart.
52. What is sinus arrhythmia?
    A quickening of the heart during inspiration and a slowing on expiration due to a disturbance of the SA node. This is considered normal in cats and dogs.