Heart and Circulation

Question 1

Describe the location of the heart.

Answer 1

The heart is central to the chest, however the left hand side is bigger meaning it could be considered to be slightly to the left.

Question 2

Describe the structural arrangement of the walls of the heart and the pericardium.

Answer 2

The heart walls have three layers:

• Endocardium: inner layer, endothelium
• Myocardium: Middle layer, cardiac muscle
• Epicardium: Outer layer, visceral pericardium

The pericardium surrounds the heart and consists of:

• Fibrous pericardium: Inelastic sac of dense connective tissue that prevents overfilling
• Serous pericardium: two layers - parietal and visceral - separated by pericardial cavity which contains serous fluid. Prevents friction.

Question 3

Describe the internal and external anatomy of the heart chambers.

Answer 3

There is four chambers to the heart. Two atria and two ventricles. The heart has a fibrous skeleton that separates the atria and ventricles. This also encircles the pulmonary trunk, aorta and valves.

Question 4

Outline blood flow through the heart in both foetal and adult circulation.

Answer 4

Vena cava -> Right atrium -> Tricuspid valve -> Right ventricle -> Pulmonary trunk -> Pulmonary veins -> Left atrium -> Bicuspid valve -> Left ventricle -> Aorta.

Foetal circulation
Ductus venous that connects the umbilical vein to the inferior vena cava
Foramen ovale connects right and left atria
Ductus arteriosus connects pulmonary artery to arch of aorta

Question 5

Describe the structural and functional characteristics of cardiac muscle and the cardiac conducting system.

Answer 5

Cardiac muscle forms a branching network of cells that are interconnected by intercalated discs which contain gap junctions. Gap junctions allow ion transport between cells which promotes coordinated contraction.
Cardiac cells act as a functional syncytium
Cardiac muscle is autorhythmic due to the SA note constantly setting off contractions at a rate of 100bpm

Question 6

Relate the electrical activity of the cardiac conducting system to the cardiac cycle.

Answer 6

SA node -> AV node -> AV bundle (bundle of his) -> Right & left bundle branches -> Purkinje fibres.

Question 7

Draw a normal ECG and explain each of its components.

Answer 7

P wave - Arterial depolarisation/contraction
QRS complex - Atrial repolarisation/relaxation and ventricular depolarisation
T wave - Ventricular repolarisation

Question 8

Identify the major vessels of the coronary circulation.

Answer 8

The anterior intraventricular and and circumflex feed into the left coronary artery
The marginal artery and the posterior intraventricular feed into the right coronary artery

Question 9

Distinguish between the pulmonary and systemic circulations.

Answer 9

Pulmonary circulation - to the lungs

Systemic circulation - to the rest of the body

Question 10

Discuss how and why the foetal circulation differs from adult circulation.

Answer 10

Ductus venous that connects the umbilical vein to the inferior vena cava
Foramen ovale connects right and left atria
Ductus arteriosus connects pulmonary artery to arch of aorta

Question 11

Identify the major vessels of the circulatory systems

Answer 11

Vena cava (inferior and superior) feeding into right atria
Pulmonary trunk and pulmonary artery leading to the lungs from the right ventricle
Pulmonary vein leading to the left atria from the lungs
Aorta leading from the left ventricle to the rest of the body

Question 12

Compare and contrast the structure and functions of: arteries, arterioles, capillaries, venules and veins.

Answer 12

ARTERIES - Takes blood away from the heart, high pressure, connective tissue then muscle and elastic fibres with an inner lining of squamous epithelium. Narrow lumen size. Rich O2 blood usually.
ARTERIOLES - Same as artery but smaller, thinner tunica medulla (muscle layer)
CAPILLARIES - Sight of gaseous, nutrient and waste exchange. Only have a tunica interna (1 layer of squamous epithelium)
VENULES - Takes blood back to the heart. Low pressure, thin tunica externa, no tunica medulla or interna. Contains valves.
VEINS - Same as venues but bigger. Has a connective tissue tunica externa and muscle tunica medulla. Large lumen size.

Question 13

Risk factors for myocardial infarction.

Answer 13

Gender (Male)
Heart disease
Smoking
Increased blood pressure
Overweight
High cholesterol
Inactivity
Diet
Diabetes
Family history
Ethnicity (British asian)

Question 14

BLOOD PRESSURE

Answer 14

CARDIAC OUTPUT X TOTAL PERIPERAL RESISTANCE

Question 15

Distinguish between systolic, diastolic, mean arterial blood pressure.

Answer 15

SYSTOLIC - The blood pressure when the heart is contracting (highest)
DIASTOLIC - The blood pressure when the heart is relaxing (lowest)
MEAN ARTERIAL - The average blood pressure during a cardiac cycle

Question 16

Define: Stroke volume (SV), End diastolic volume (EDV), End systolic volume (ESV), Cardiac output (CO), Total peripheral resistance (TPR), Heart rate (HR)

Answer 16

STROKE VOLUME - Amount of blood ejected per beat
END DIASTOLIC VOLUME - Amount of blood in the ventricles before systole occurs
CARDIAC OUTPUT - Amount of blood ejected per min
TOTAL PERIPHERAL RESISTANCE - Total resistance opposing blood flow in systemic circulation
HEART RATE - Beats per minute

Question 17

Discuss the main factors which determine CO.

Answer 17

Degree of stretch in the myocytes (Preload)
Forcefulness of contraction
Pressure required to eject blood
Factors which effect TPR (Viscosity of blood, vessel length and vessel radius)

Question 18

Explain the events of the baroreceptor reflex.

Answer 18

Baroreceptors detect when blood pressure drops or rises and send signals causing the activation of mechanisms such as ADH, increase/decrease in heart rate.

Question 19

Discuss the short term mechanisms of blood pressure control.

Answer 19

Adjustments are made by alterations in Cardiac Output (CO) and total peripheral resistance, mediated by means of autonomic nervous system influences on the heart, veins and arterioles.

Question 20

Discuss fluid replacement following an operation.

Answer 20

Immediately after operations an increased amount of ADH is produced. Water can be replaced via IV drip of required.

Question 21

HYPERTENSION

Answer 21

High blood pressure, over 140/90mmHg

Question 22

Describe the major causes of hypertension and its associated risk factors.

Answer 22

Age
Family history
Being of african or Caribbean origin
Consuming high amounts of salt
Lack of exercise
Being overweight
Smoking
Alcohol

Causes damage to blood vessels, heart and other organs.