Cardiovascular System Flashcards
Duty of blood
Transports everything that must be carried from one place to another, including
- Nutrients
- Oxygen
- Wastes
- Hormones
- Body heat
- Acid base and electrolyte balance
Components of blood
▪ Formed elements (living cells) – 45% known as hematocrit as Erythrocytes sink to the bottom
▪ Plasma (nonliving fluid matrix) – 55%
▪ Buffy Coat (less than 1%) contains leukocytes and platelets – thin, whitish layer between the erythrocytes and plasma
Physical characteristics of blood
- Sticky, opaque fluid
- Heavier and thicker than water (5 times)as blood contains solid components such as plasma proteins, electrolytes
- Color range: oxygen-rich blood is scarlet red, oxygen-poor blood is dull red or purple
- Metallic, salty taste
- Blood pH is slightly alkaline, 7.35 – 7.45 pH
- Temperature 38 degrees
- Blood viscosity contributes to blood flow resistance. Blood viscosity increases with high altitudes, decreased blood temperature and increased proportion of red blood cells
Composition of plasma
90% water , 8% plasma proteins
Straw-coloured fluid
Dissolved substances (2%): nutrients, salts (electrolytes), respiratory gases, hormones, plasma proteins, waste products
electrolytes such as sodium, potassium, chloride, magnesium and calcium, maintain fluid and electrolyte balance
Describe and name the plasma proteins
- Most abundant solutes in plasma
- Most are made by the liver
- 3 types – fibrinogen, albumin and globulin
- Albumin – an important blood buffer and contributes to osmotic pressure
- Fibrinogen - Clotting proteins – help to stem blood loss when a blood vessel is injured
- Globulin - Antibodies – help protect the body from pathogens
Describe components of the formed elements
Each element starts as haematopoietic stem cell which morphs into another type of morph cell which turns into a blast cell. Depending on which growth factors and hormones influence them, these cells turn into either:
Erythrocytes – red blood cells (RBCs)
Leukocytes – White blood cells (WBCs)
Platelets – Cell fragments
Explain Erythrocytes
Main function is to carry oxygen and carry C02 away
Difference to other blood cells –
- Anucleate (no nucleus)
- Contains few organelles, no mitochondria
- Shaped like biconcave discs – increases surface area, flexibility is increased, restricts the cell’s life span to 120 days
- 7-8 micro mm
What is haemoglobin
- Binds oxygen, each can bind 4 oxygen molecules
- Transports C02 back to lungs
- Each erythrocyte has 250million haemoglobin molecules
- Normal blood contains 12-18g of haemoglobin per 100ml of blood
Describe Leukocytes
- Crucial in body’s defence against disease
- Complete cells, with nucleus and organelles
- Able to move into and out of blood vessels (diapedesis)
- Respond to chemicals released by damaged tissues (known as positive chemotaxis)
- Move by amoeboid motion
- 4,800 to 10,800 WBCs per mm3 of blood, for 1 wbc there are 700 rbc
- Produce antibodies, play role in allergic reactions, inflammatory response, destroy parasites
What are platelets
▪ Fragments of megakaryocytes (multinucleate cells)
Small, irregularly shaped, non-nucleated
Important in haemostasis
▪ Needed for the clotting process
▪ Normal platelet count is 300,000 platelets per mm3 of blood
Positioning and size of heart
Size of a human fist, weighs less than a pound
Located in the thoracic cavity, in the inferior mediastinum
▪ Apex is directed toward left hip and rests on the diaphragm 5th rib ▪ Base points toward right shoulder
Coverings of the heart
Pericardium – a double walled sac
- Fibrous pericardium is loose and superficial
- Serous membrane is deep to the fibrous pericardium and contains two layers
- Serous fluid fills the space between the layers of pericardium called the pericardial cavity
What are the walls of the heart
- Epicardium ▪ Outside layer; the visceral pericardium, the coronary artery lies here
- Myocardium ▪ Middle layer ▪ Mostly cardiac muscle, 2/3 of the heart muscle, contracts
- Endocardium ▪ Inner layer known as endothelium
What are the chambers of the heart and explain their duties
Atria (right and left) – superior - Receiving chambers - Assist with filling the ventricles - Blood enters under low pressure Ventricles (right and left) - Discharging chambers - Thick walled pumps of the heart - During contraction, blood is propelled into circulation
Name the septum and their duties
Interatrial septum
- Separates the two atria longitudinally
Interventricular septum
- Separates the two ventricles longitudinally
Explain the double pump
- Arteries carry blood away from the heart
- Veins carry blood toward the heart
Double pump - Right side works as the pulmonary circuit pump
- Left side works as the systemic circuit pump
What is the pulmonary Circuit pump
▪ Blood flows from the right side of the heart to the lungs and back to the left side of the heart
▪ Blood is pumped out of right side through the pulmonary trunk, which splits into pulmonary arteries and takes oxygen-poor blood to lungs
▪ Oxygen-rich blood returns to the heart from the lungs via pulmonary veins
What is the Systemic Circulation pump
▪ Oxygen-rich blood returned to the left side of the heart is pumped out into the aorta
▪ Blood circulates to systemic arteries and to all body tissues
▪ Left ventricle has thicker walls because it pumps blood to the body through the systemic circuit
▪ Oxygen-poor blood returns to the right atrium via systemic veins, which empty blood into the superior or inferior vena cava
Explain the heart valves
Allow blood to flow in only one direction, to prevent backflow
▪ Atrioventricular (AV) valves—between atria and ventricles ▪ Left AV valve: bicuspid (mitral) valve ▪ Right AV valve: tricuspid valve
▪ Open during heart relaxation, when blood passively fills the chambers ▪ Closed during ventricular contraction
▪ Semilunar valves—between ventricle and artery ▪ Pulmonary semilunar valve ▪ Aortic semilunar valve
Closed during heart relaxation ▪ Open during ventricular contraction
Valves open and close in response to pressure changes in the heart
Components of blood supply to circulatory system
▪ Coronary arteries (right and left) —branch from the aorta to supply the heart muscle with oxygenated blood, filled when heart is relaxed
▪ Cardiac veins—drain the myocardium of blood
▪ Coronary sinus—a large vein on the posterior of the heart; receives blood from cardiac veins
Blood empties into the right atrium via the coronary sinus
Unifying regulatory systems are
- Autonomic nervous system – decrease or increase heart rate
- Intrinsic conduction system, or the nodal system
- Sets the heart rhythm ▪ Composed of special nervous tissue ▪ Ensures heart muscle depolarization in one direction only (atria to ventricles) ▪ Enforces a heart rate of 75 beats per minute
Components of the intrinsic conduction system
▪ Sinoatrial (SA) node - Located in the right atrium ▪ Serves as the heart’s pacemaker
▪ Atrioventricular (AV) node is at the junction of the atria and ventricles
▪ Atrioventricular (AV) bundle (bundle of His) and bundle branches are in the interventricular septum
▪ Purkinje fibers spread within the ventricle wall muscles
Steps of contraction coordination
- The sinoatrial node (SA node) starts each heartbeat
- Electrical impulses carried to left atrium
- Atria contract
- At the AV node, the impulse is delayed briefly
- Impulse travels through the AV bundle, bundle branches, and Purkinje fibers ▪ Ventricles contract; blood is ejected from the heart
Explain Tachycardia and Bradycardia
▪ Tachycardia—rapid heart rate, over 100 beats per minute ▪ Bradycardia—slow heart rate, less than 60 beats per minutes
Explain the ECG
▪ Recording of electrical activity of the heart
Three waves –
1. P wave – small, signal depolarization, firing of sinoatrial node
2. QRS complex – depolarization of ventricles, contraction of the ventricles
3. T wave – ventricle relax, repolarization
▪ Illustrates what is happening electrically in the atria and ventricles when the depolarize (contract) and relax (repolarize)
What are systole and diastole
- Systole = contraction (1/3 of the cycle)
- Diastole = relaxation (2/3 of the cycle)
What are the cardiac cycle steps
- Atrial Diastole – ventricular filling
- Atrial Systole
- Isovolumetric contraction
- Ventricular systole (ejection phase)
- Isometric relaxation
Explain the heart sounds
▪ Often described a “lub” and “dup” sounds - Correspond with closing of heart valves
Heart murmurs are abnormal or unusual heart sounds ▪ Reflect turbulent blood flow
▪ Lub—longer, louder heart sound caused by the closing of the AV valves
▪ Dup—short, sharp heart sound caused by the closing of the semilunar valves at the end of ventricular systole
What is cardiac output and Stroke volume
Cardiac Output (CO)
▪ Amount of blood pumped by each side (ventricle) of the heart in 1 minute
Stroke volume (SV)
▪ Volume of blood pumped by each ventricle in one contraction (each heartbeat) ▪ About 70 ml of blood is pumped out of the left ventricle with each heartbeat
What is heart rate and how is it calculated
▪ Cardiac output is the product of the heart rate (HR) and the stroke volume (SV) ▪ CO = HR × SV ▪ CO = HR (75 beats/min) × SV (70 ml/beat) ▪ CO = 5250 ml/min = 5.25 L/min
How is stroke volume regulated
how much cardiac muscle is stretched
▪ The more the cardiac muscle is stretched, the stronger the contraction
▪ Venous return is the important factor influencing the stretch of heart muscle