bm1022 cardiovascular system

(1)

BM1022

CARDIOVASCULAR SYSTEM

Overview

Roles of the cardiovascular system:

 Homeostasis

 Delivery and dispersal of oxygen and nutrients

 Removal of carbon dioxide and waste

 Carriage of chemical signals for cells Contains 3 components:

 Heart – 4 chambered double pump

 Systematic circuit

o High pressured circuit

o Arteries carry oxygenated blood from the left side of the heart to all tissues around the body

o Veins carry deoxygenated blood and waste away from the tissues of the body to the right side of the heart

 Pulmonary circuit

o Low pressure circuit (lungs are a part

of this system)

o Arteries carry deoxygenated blood away from the right side of the heart to the lungs

ARTERIES AND VEINS SWAP ROLES IN THE

SYSTEMATIC AND

PERIPHERAL

SYSTEMS

(2)

o Veins carry oxygenated blood back to the left side of the heart ready for distribution throughout the body

Heart anatomy

Heart wall has 3 layers:

 Epicardium – protective layer, positions major arteries and veins

 Myocardium – muscle layer, properties of contractility and electrical excitability

 Endocardium – Endothelial layer, internal layer of heart

Heart chambers and associated great vessels

The heart has 4 chambers, which consist of a left and right atria and left and right ventricle.

Atria

 Receiving chambers

 Thin walled muscle layer. This is due to contractile muscle not required

in the artias Right Atrium

 Receives deoxygenated blood from the systematic system via the vena

cava Left Atrium

 Receives oxygenated blood from the pulmonary circuit via the pulmonary veins

Ventricles

 Pumping chambers

 Walls have thick muscle layers due to need to contract and pump muscle around the heart

(3)

Left Ventricle

 Pumps oxygenated blood into the aorta and aortic branches which sends blood to the brain, organs and peripheral tissues

 Also pumps blood into the

coronary circuit Right Ventricle

 Pumps deoxygenated blood

through the pulmonary circuit via the pulmonary artery to become oxygenated

Heart Valves

Valves ensure that the blood doesn’t go the wrong way.

Atrioventricular valve (AV)

 Separate the atrial and ventricular chambers

 Prevent backflow

 No contraction = valves open

 Contraction = valves closed

 Right AV valve is the tricuspid valves

 Left AV valves is the bicuspid or mitral valves

Aortic and Pulmonary Valves

 Separate ventricles from arteries

 Prevent backflow

(4)

 Aortic valve separates the junction of the left ventricle and the aorta

 Pulmonary valve separates the junction of the right ventricle and the pulmonary arteries

Blood supply of the heart – Coronary Circulation

 Contraction requires a lot of energy that is gain via nutrients in the blood

 Cells of the cell wall (myocardial cells) don’t receive oxygen directly from the chambers of the heart – Coronary circulation provides this

 Specific arteries and veins are required for the flow of oxygen and

removal of carbon dioxide Coronary circulation consists of:

 Coronary arteries – left and right coronary arteries; carry blood from the aorta to the myocardium

 Coronary veins – great, middle and small cardiac veins and coronary sinus, carry blood from the myocardium to the right atrium

Properties of myocardial cells

 Myocardial cells are interconnected by specialised plasma membrane

structure termed the intercalated discs

 An important component of these discs are the gap junctions which

allow neighbouring cells to share (functional syncytium is what the cells are called once sharing everything)

There are 2 different types of myocardial cells in the heart, which are vital in the function of the heart:

 Contractile myocardial cells – cells which provide the contraction

(5)

 Conductile myocardial cells – Autorhythmic myocardial cells – Provide signal for the contractile cells

These myocardial cells both have different action potentials.