Introduction to circulation

Question 1

What are the functions of circulation?

Answer 1

–Carrying O2 glucose nutrients to the cells

–Removing waste: CO2 and heat

–Homeostasis of the extracellular fluid (via the kidneys)

–Distribution of hormones

–temperature regulation

–defence against infections

Question 2

What is the main function of the cardiovascular system?

Answer 2

–To maintain appropriate levels of perfusion to tissues

Question 3

What are the functional differences between the systemic circulation and the pulmonary circulation?

Answer 3

Pulmonary: Lungs, low pressure, high flow, low resistance.

Systemic: Multiple organs, high pressure, variable flow, variable resistance

Question 4

Name the four valves and the regions that they divide?

Answer 4

• Tricuspid – R atrium from R ventricle
• Pulmonary – R ventricle from pulmonary artery
• Aortic – L ventricle from aorta
• Mitral (sometimes called “the bicuspid valve”) – L atrium from R ventricle

Question 5

What are the two main normal valve sounds AND what causes them?

Answer 5

•S1, First heart sound – produced by the closing of the AV valves.

–Marks the end of ventricular diastole

–Occurs when ventricular pressure increases above atrial pressure

•S2, Second heart sound – produced by the closing of semilunar valves.

–Marks the end of ventricular system

–Occurs when ventricular pressure decreases below arterial (aortic/pulmonary) pressure

Question 6

What is the key blood pressure equation?

Answer 6

BP = cardiac output (flow) x peripheral resistance

BP = CO x PR

Question 7

How is blood pressure measured?

Answer 7

By listening for Korotkoff sounds made by the brachial artery as different pressures are applied to the upper arm.

Question 8

What is the main regulator for blood volume?

Answer 8

Blood volume is set by the kidneys (or its processes of filtration and reabsorption)

–Depends on water intake

–Can also say “GFR”

Question 9

What are the symptoms of heart murmurs?

Answer 9

Often asymptomatic, possibly pt has low energy

Question 10

What type of blood vessel is the reservoir for the majority of blood in the body?

Answer 10

veins

Question 11

What elements of the vascular system have the greatest influence on total peripheral resistance (TPR)?

Answer 11

Resistance arterioles. A generalised contraction in resistance arterioles greatly affects TPR and measured blood pressure.

Question 12

Name the layers of a large artery (from innermost to outermost) and the type of tissue found in each layer

Answer 12

•Intima

–Endothelium

–Basement membrane

–Lamina propria

• Internal elastic membrane
• Media (smooth muscle)
• Adventitia (connective tissue)

Question 13

Name some differences in structure and function between the right heart and the left heart

Answer 13

Right heart

• Thin walled
• Crescent X-section
• Sends blood toLungs only
• Low Pressure
• High flow
• Low resistance
• Deoxygenated blood

Left Heart

• Thick walled
• Circular cross section
• Sends blood to the body
• High pressure system
• Variable flow system
• High resistance system
• Oxygenated blood

Question 14

Name the large blood vessels, the heart chambers, and the valves that plasma must pass through as it goes from the vena cava to the aorta (in order).

Answer 14

•Superior & Inferior Vena cava

–Arrives Deoxygenated

• Right Atrium
• Tricuspid Valve
• Right Ventricle
• Pulmonary Valve
• Pulmonary Arteries
• Lungs

–Oxygenated

• Pulmonary Veins
• Left Atrium
• Mitral (bicuspid) Valve
• Left Ventricle
• Aortic Valve
• Systemic Circulation

Question 15

What are AV valves in the heart?

Answer 15

• AV valves control fluid movement (making it one-way) between the atria and their ventricles
• The 2 AV valves are the tricuspid valve (between the RA and the RV) and the bicuspid (or mitral) valve (between the LA and the LV)
• The tricuspid valve is made up of three leaflets and the bicuspid valve is made up of 2 leaflets
• Each leaflet is prevented from everting by chordae tendinae, which are connected to the papillary muscle in the appropriate ventricle
• When the AV valves close, they make the sound known as S1

Question 16

What are semilunar valves in the heart

Answer 16

• Semilunar valves control fluid movement (making it one-way) between ventricles and their output arteries
• They are made up of three flaps that look “moon-like”
• The 2 seminlunar valves are the pulmonary valve (between the RV and the pulmonary arteries) and the aortic valve (between the LV and the aorta)
• When the semilunar valves close, they make the sound known as S2

Question 17

Explain briefly how the kidneys contribute to setting blood volume.

Answer 17

• The kidneys filter the blood, sending toxins, waste products, water and electrolytes into the urine
• The filtration occurs by sending plasma to a nephron.
• Small molecules are filtered through the glomerulus of the nephron into the tubule system, and necessary molecules (eg water and electrolytes) are absorbed back into the blood, leaving behind other molecules to be excreted.
• The kidney can rapidly decrease blood volume by filtering more fluid and reabsorbing less water, and it can increase blood volume (after drinking) by decreasing filtration and increasing reabsorption

Question 18

Explain what a portal system is, in the context of the kidney

Answer 18

• A portal system is when a capillary bed pools into another capillary bed through veins, without first going back through the heart. The two capillary beds are IN SERIES with one another.
• Both capillary beds and the blood vessels that connect them are considered part of the portal system.
• Portal systems allow the contents of one capillary system to be “seen” by another capillary system without being diluted by being mixed with blood from the rest of the body
• At the nephron, the first set of capillaries (the glomerular capillaries) reformulate into the efferent arteriole
• Instead of sending blood straight back to the heart, the efferent arterioles rebranch into the peritubular capillaries, where they reabsorb molecules from the tubule system
• In the peritubular capillaries, the blood is osmotically concentrated, which allows it to absorb readily the water and electrolytes during reabsorption

Question 19

Define (for the nephron) filtration, reabsorption, secretion and excretion.

Answer 19

• Filtration is when a molecule leaves the glomerular capillaries and enters the Bowman’s capsule
• Reabsorption is when a molecule leaves the nephrons tubule system and enters the peritubular capillaries
• Secretion is when a molecule leaves (is sent from) the peritubular capillaries into the tubule system
• Excretion is when a molecule follows the course of the tubule system to its end and ends up in the urinary bladder

Question 20

Name the blood vessels (in order) that plasma going to a nephron would pass through if the blood was not filtered?

Answer 20

• Afferent arteriole
• Glomerular capillaries
• Efferent arteriole
• Peritubular capillaries
• Venous system back to the heart

Question 21

What is GFR?

Answer 21

• GFR = glomerular filtration rate
• It is the amount of fluid entering all Bowmans capsules
• In ml / min
• increased GFR leads to fluid loss to urine

Question 22

What is the difference between hypoxia and ischaemia?

Answer 22

• Hypoxia is when there is insufficient O2 supply to a region or to entire body
• Ischaemia is when there is insufficient blood flow to a region
• Ischemia always results in hypoxia; however, hypoxia can occur without ischaemia if, for example, the oxygen content of the arterial blood decreases

–as occurs with lung disease or anaemia.

Question 23

What is angina pectoris?

Answer 23

• A symptom
• Of chest pain (and referred chest pain)
• Due to over-exertion of heart muscle
• Typically in the context of ischaemia of heart tissue

–Due to coronary artery disease

Question 24

What is “reperfusion” in the context of an acute myocardial infarct?

Answer 24

• Reperfusion is the re-establishment of blood supply to an area that has been ischaemic or otherwise deprived of oxygen.
• Usually the initial insult is a plaque or thrombosis that is blocking a blood vessel (eg myocardial infarct), so that plaque or thrombosis must be moved or destroyed.
• The medical procedures used to move or remove the plaque are generally referred to as PCI (percutaneous coronary intervention) such as balloon angioplasty.
• There are also “plaque buster drugs” such as tissue plasminogen activator that can be used instead of PCI.

Question 25

There are a number of different types of shock. Give an example of shock, explaining how it manifests in the patient.

Answer 25

•Haemorrhagic shock is when the patient loses so much blood that blood pressure drops precipitously resulting in poor perfusion (esp of the brain and kidney) yhat the patient loses consciousness and stops producing urine – also called hypovolaemic shock

•

•Other examples of shock are cardiogenic shock (low cardiac output), distributive shock (caused by massive BV dilation, eg septic shock or neurogenic shock)

Question 26

What is syncope and what disorders typically might cause it?

Answer 26

• Syncope is loss of consciousness
• Due to insufficient perfusion of the brain
• Other causes of fainting (seizures, concussion) are NOT syncope
• It could be caused by arrhythmias
• It could be caused by shock

Question 27

What is the definition of heart failure? How is this different from chronic low output heart failure?

Answer 27

• When the amount of blood pumped out by the heart is insufficient to meet the needs of the tissues
• Assuming that there is enough blood returning to the heart

–Haemorrhage is NOT heart failure

• Heart failure is a general term
• Chronic low output heart failure is one type of heart failure

–There is high output heart failure, which includes anaemia and increased O2 demand by the tissues

• In chronic low output heart failure, it is chronic (long term) and the cause is specifically that the heart’s ability to pump blood is reduced — eg by accumulated damage, such as infarcts
• Symptoms of chronic low output heart failure are dyspnoea, peripheral oedema, and fatigue (exercise intolerance)

Question 28

What are Korotkoff sounds?

Answer 28

• Korotkoff sounds are the sounds that medical personnel listen for when they are taking blood pressure using a non-invasive procedure. The sounds heard during measurement of blood pressure are not the same as the heart sounds ‘lub’ and ‘dub’ that are due to the closing of the hearts valves. If a stethoscope is placed over the brachial artery in the antecubital fossa in a normal person (without arterial disease), no sound should be audible. As the heart beats, these pulses are transmitted smoothly via laminar (non-turbulent) blood flow throughout the arteries, and no sound is produced. Similarly, if the cuff of a sphygmomanometer is placed around a patient’s upper arm and inflated to a pressure above the patient’s systolic blood pressure, there will be no sound audible. This is because the pressure in the cuff is high enough such that it completely occludes the blood flow. This is similar to a flexible tube or pipe with fluid in it that is being pinched shut.
• If the pressure is dropped to a level equal to that of the patient’s systolic blood pressure, the first Korotkoff sound will be heard. As the pressure in the cuff is the same as the pressure produced by the heart, some blood will be able to pass through the upper arm when the pressure in the artery rises during systole. This blood flows in spurts as the pressure in the artery rises above the pressure in the cuff and then drops back down beyond the cuffed region, resulting in turbulence that produces an audible sound.
• As the pressure in the cuff is allowed to fall further, thumping sounds continue to be heard as long as the pressure in the cuff is between the systolic and diastolic pressures, as the arterial pressure keeps on rising above and dropping back below the pressure in the cuff.
• Eventually, as the pressure in the cuff drops further, the sounds change in quality, then become muted, and finally disappear altogether. This occurs because, as the pressure in the cuff drops below the diastolic blood pressure, the cuff no longer provides any restriction to blood flow allowing the blood flow to become smooth again with no turbulence and thus produce no further audible sound.