THE CARDIOVASCULAR SYSTEM Biology 2

CARDIOVASCULAR SYSTEM

https://www.youtube.com/watch?v=gVY04NQUpxk

How does this video relate to the heart?

What happens to the man in the video?

SCHEME OF BLOOD CIRCULATION

Pulmonary circulation Eliminates carbon dioxide via the lungs

and oxygenates the blood Contains deoxygenated blood

Systemic circulation Delivers oxygen to all body cells and

carries away wastes Contains oxygen-rich blood

CIRCULATION

Without circulation, tissues would lack a supply of oxygen and nutrients, and wastes would accumulate

Necrosis = death of body tissue that occurs when not enough blood is flowing to the tissue

HEART SIZE & LOCATION

Average adult heart size is 14 centimeters long and 9 centimeters wide (fist size)

Housed within the mediastinum – location behind the sternum Bordered laterally by the lungs The base of the heart lies beneath the 2nd rib The apex (distal point of the heart) extends

downward and to the left to the intercostal space between the 5th & 6th rib

HEART LOCATION

COVERINGS OF THE HEART

Pericardium- encloses the heart and the proximal ends of the large blood vessels to where it attaches Outer fibrous pericardium attaches heart to

surroundings Double-layered sac

Visceral pericardium = innermost layer of sac AKA epicardium

Parietal pericardium = inner lining of fibrous pericardium

Pericardial cavity- space between the visceral and parietal layers Contains fluid that reduces friction as heart contracts

PERICARDIUM

PERICARDITIS

Swelling and irritation of the pericardium

Pericarditis often causes chest pain and sometimes other symptoms. The sharp chest pain associated with pericarditis occurs when the irritated layers of the pericardium rub against each other.

3 LAYERS OF THE HEART’S WALLS Epicardium- outer layer

Also part of the visceral pericardium Made of connective & adipose tissue Protects heart by reducing friction

Myocardium- middle layer Thick cardiac muscle tissue Pumps blood out of the heart chambers

Endocardium- inner layer Epithelial and connective tissue layer Contains elastic fibers, blood vessels, &

Purkinje fibers

3 LAYERS OF HEART WALLS

3 LAYERS OF HEART WALLS

DOUBLE PUMP

The heart is divided into 4 hollow chambers Atria- upper chambers have thin walls and

receive blood returning to heart Ventricles- lower chambers that receive

blood from the atria and contract to force blood out of the heart into arteries

Septum- solid wall that separates the atrium and ventricle on the right from the atrium and ventricle on the left

CHAMBERS OF THE HEART

VALVES OF THE HEART Atrioventricular

valves (A-V valves)- ensure one way flow of blood between atria and ventricles Tricuspid valve-

located between the right AV

Bicuspid valve (AKA mitral valve)- located between the left AV

THE VENTRICLES

The right ventricle has thinner muscular walls as it only pumps blood a short distance to the lungs

The left ventricle is thick and must force the blood to all parts of the body against a greater resistance to flow

BLOOD FLOW The right atrium

receives blood from 2 large veins: superior vena cava and inferior vena cava Superior vena cava-

returns blood to heart from upper body

Inferior vena cava- returns blood to heart from lower body

BLOOD FLOW Muscular wall of RV

contracts, blood in chamber is under pressure, closing the tricuspid valve and forcing the blood out the pulmonary trunk, which divides into the pulmonary arteries

Pulmonary arteries- lead to lungs

BLOOD FLOW The LA receives

blood from 4 pulmonary veins (2 from each lung)

The LV contracts, closing the bicuspid valve and pushing blood through the aortic valve into the aorta Aorta – large artery

that delivers blood to the body

SEMILUNAR VALVES

The pulmonary and aortic valves are called semilunar valves due to their half moon shape of their cusps

MITRAL VALVE PROLAPSE (MVP)

One or both of the cusps of the mitral valve stretches and bulges into the left atrium during ventriclar contraction

Sometimes blood flows back into the left atrium

Chest pain, palpitations, fatigue, anxiety Sounds like a “click and a murmur” 6% of the population More susceptible to endocarditis, which can

be caused by Streptococcus

MITRAL VALVE PROLAPSE

https://www.youtube.com/watch?v=AHBzu5zhFuA

https://www.youtube.com/watch?v=KmhKufTS0wQ

BLOOD SUPPLY TO THE HEART

Right & Left Coronary Arteries- 1st two branches of the aorta that supply blood to heart tissue Feed the many capillaries of the

myocardium Cardiac veins- drain the blood that has

passed through the myocardial capillaries (deoxygenated blood) These veins join an enlarged vein on the

heart’s posterior surface called the coronary sinus- empties directly into the right atrium