Circulatory System Overview

Study Notes

Circulatory System

Another name for the circulatory system is the cardiovascular system
Two other systems part of the circulatory system are the lymphatic system and the respiratory system
Pulmonary circulation is the flow of blood between the heart and the lungs
Systemic circulation is the flow of blood between the heart and the rest of the body
Arteries carry blood away from the heart
Capillaries are thin-walled blood vessels for oxygen exchange
Bleeding from capillaries is called capillary bleeding
Arteries have thicker walls than arterioles
Veins have thinner walls and valves than venules
Veins have valves that prevent backflow of blood; arterioles do not
End arteries have no capillary bed
Advantages of end arteries are increased pressure and more precise control of blood flow; disadvantages are less flexibility to adjust blood flow
Functions of blood: transport, regulation, protection
Blood's pH is slightly alkaline (approximately 7.4)
Blood accounts for ~8% of body weight
Arterial blood is oxygen-rich and carries nutrients
Venous blood is oxygen-poor and carries waste
Plasma is the straw-colored fluid in blood, suspends blood cells
Six components of plasma: water, proteins, nutrients, electrolytes, waste products, and hormones
Three main types of blood cells: erythrocytes (red blood cells), leukocytes (white blood cells), thrombocytes (platelets)
Main function of erythrocytes: transport oxygen
Three immature forms of red blood cells: proerythroblasts, basophilic erythroblasts, and polychromatophilic erythroblasts
Four properties of adult red blood cells: biconcave shape, flexible cell membrane, lack of nucleus, contain hemoglobin
Erythropoietin is a substance secreted by the kidneys in response to low oxygen levels
Red blood cell production in adults primarily occurs in bone marrow, and in foetuses, also in the liver and spleen
Spent erythrocytes are broken down in the liver and spleen
Granulocytes are also known as polymorphonuclear leukocytes
Two main groups of white blood cells: granulocytes and agranulocytes
Granulocytes and monocytes are produced in bone marrow
Neutrophils, basophils, and eosinophils are granulocytes
Neutrophils engulf and destroy pathogens
Basophils release histamine, which promotes inflammation
Eosinophils fight parasitic infections
Lymphocytes and monocytes are agranulocytes; they play a role in adaptive immunity
Platelets are fragments of megakaryocytes
Four main stages of blood clotting: vascular spasm, platelet plug formation, coagulation, and clot retraction
Serum is blood plasma without clotting factors; plasma is the liquid component of blood
Vitamin K is required for the manufacture of prothrombin
Anticoagulants prevent blood clotting
Four chambers of the heart: two atria and two ventricles
Pericardium is the membrane surrounding the heart
Myocardium is the muscular tissue of the heart

Heart Structure and Function

Heart valves prevent backflow of blood
Valves of the heart: mitral, tricuspid, pulmonary, and aortic valves
Number of cusps per valve varies by the valve
Structures that limit atrio-ventricular valve movement: papillary muscles and chordae tendinae
Conduction mechanism of the heart contains: sinoatrial node (SA node), atrioventricular node (AV node), bundle of His, bundle branches, and Purkinje fibers
Systole (contraction) and diastole (relaxation) are involved in the cardiac cycle
Pulse is the rhythmic expansion and contraction of arteries due to blood flow
A jerky, strong pulse is sometimes associated with valvular insufficiency or congenital heart defects
Auscultation is the act of listening to sounds within the body
Other instruments used for auscultation in heart diagnostics include stethoscopes (and other specialized listening devices)
Heart sounds (lub-dub) originate from valve closure
Normal heart rates for cats and dogs vary
Tachycardia is a faster-than-normal heart rate
Bradycardia is a slower-than-normal heart rate
Arrhythmia is an irregular heartbeat pattern
Sinus arrhythmia is a normal variation in heart rate with breathing