The Cardiovascular System: The HEART. Incredible HEART Facts! The body of an adult contains over 60,000 miles of blood vessels! Your heart beats about.

The Cardiovascular System: The HEART

Incredible HEART Facts!

• The body of an adult contains over 60,000 miles of blood vessels!

• Your heart beats about 100,000 times each day!

• Your heart beats some 30 million times a year!

• An adult's heart pumps nearly 4000 gallons of blood each day!

• A "heartbeat" is really the sound of the valves in the heart closing as they push blood through its chambers.

• Comprised of the following– Blood– Heart– Blood vessels

• Veins-smaller branches venules

• Arteries-smaller branches arterioles

• Capillaries-

(one cell thick, remember!!!)

What are the Three Main Functions of the Cardiovascular

System?• 1. Transport of nutrients, oxygen and hormones to cells

throughout the body and removal of metabolic wastes (carbon dioxide, nitrogenous wastes, and heat.)

• 2. Protection of the body by white blood cells, antibodies, and complement proteins that circulate in the blood and defend the body against foreign microbes and toxins. Clotting mechanisms are also present that protect the body from blood loss after injuries.

• 3. Regulation of body temperature, fluid pH, and water content of cells.

THE HEART• 4 chambers:

– Two superior atria and two inferior ventricles

• The arteries are the passageways through which the blood is delivered. (Arteries= Away)

• The largest artery is the aorta, which branches off the heart and then divides into many smaller arteries.

• Veins carry the deoxygenated blood back to the lungs to pick up more oxygen, and then back to the heart once again.

• Blood flows continuously through the circulatory system, and

the heart muscle is the pump which makes it all possible!

Heart Wall

• Consists of three muscles:

1. Epicardium- the viceral pericardium that covers the outer surface of the heart

2. Myocardium- muscular part of the heart

3. Endocardium- thin, smooth, endothelial, inner lining of the heart

The Conduction System

• Cardiac conduction is the rate at which the heart conducts electrical impulses

• Cardiac muscle cells contract spontaneously

• These contractions are coordinated by the sinoatrial (SA) node which is also referred to as the pacemaker of the heart.

SA Node

• The SA node – composed of nodular

tissue that has characteristics of both muscle and nervous tissue.

• The SA node is located in the upper wall of the right atrium. When the SA node contracts it generates nerve impulses that travel throughout the heart wall causing both atria to contract.

AV Node

• Another section of nodal tissue lies on the right side of the partition that divides the atria, near the bottom of the right atrium. – called the atrioventricular (AV) node. When the impulses

reach the AV node they are delayed for about a tenth of a second. This delay allows the atria to contract and empty their contents first.

• The impulses are then sent down the atrioventricular bundle. This bundle of fibers branches off into two bundles and the impulses are carried down the center of the heart to the left and right ventricles.

• At the base of the heart the atrioventricular bundles start to divide further into Purkinje fibers. When the impulses reach these fibers they trigger the muscle fibers in the ventricles to contract.

Coronary Circulation

Atria

Description: thin wall, holding chamber for blood until delivers blood to ventricles

• Right atria – Filled by deoxygenated

blood from 3 sources:

1. Superior vena cava

2. Inferior vena cava

3. Coronary sinus

• Left atria – Filled by oxygenated

blood from the lungs via 4 pulmonary veins

Heart Valves

• Atrioventricular valves (AV Valves)– - tricuspid and

bicuspid

• Semilunar valves– pulmonary and aortic

semilunar

• heart sounds: – “Lubb-Dupp”

• Lubb - closing of the AV valves (louder & longer)

• Dupp - closing of the semilunar valves

• Murmur - turbulent blood flow indicates a problem (backflow)

Ventricles

• Description: thick wall, work as two separate pumps

• Right ventricle – smaller workload, pumps

deoxygenated blood to lungs

– receives blood from right atria via tricuspid valve

– pumps blood to pulmonary trunk via pulmonary semilunar valve

• Left ventricle – larger workload, pumps

systemic (body) blood supply

– muscle wall is therefore thicker than right ventricle

– receives blood from left atria via bicuspid valve

– pumps blood to aorta via aortic semilunar valve

Bicuspid valveBicuspid valve

Inferior Vena Cava

Superior Vena CavaAorta

Pulmonary Artery

Pulmonary veins

The Cardiac Cycle

• Blood Circulation Circuits

1. Pulmonary Circuit - lungs

2. Systemic Circuit - whole body

Steps in a Contraction• As the heart relaxes, both atrium chambers fill with blood:

– Nonoxygenated blood comes into the right side from the body's main veins and oxygenated blood returns to the left side after a trip to the lungs.

• The heart valves open and the atria force the blood into the ventricles.

• The ventricles then contract to pump – Nonoxygenated blood through the pulmonary semilunar valve into

the lungs – Oxygenated blood through the aortic semilunar valve into the body's

main circulatory system.

• The atria relax to once more fill with blood to restart the cycle.

Steps in Contraction Simplified• Vena Cava• Right Atrium• Tricuspid valve• Right Ventricle• Pulmonary Semilunar

valve• Pulmonary artery• Pulmonary veins• Left Atrium• Bicuspid valve• Left Ventricle• Aortic Semilunar valve• Aorta

Bicuspid valve

Coronary Artery Disease• Is when one or more of the coronary arteries becomes narrowed or totally blocked by a gradual build-up of fat (cholesterol) within the artery wall– which reduces blood flow to the heart muscle. As a

result, the heart muscle does not get the oxygen-rich blood that it needs, and it begins to die.

• Leading cause of death in US!!! • TREATMENTS:

1. Atherosclerosis bypass surgery • blood vessel from another site • used to bypass a blockage

2. Coronary angioplasty • balloon catheter inserted and inflated to flatten plaque

3. Laser angioplasty - laser first, then balloon angioplasty

Coronary Artery Disease Treatments

Systemic Circulation

Systemic Circulation

• During systemic circulation:– Blood passes through the kidneys- the kidneys

filter much of the waste from the blood – Blood also passes through the small intestine

• the blood from the small intestine collects in the portal vein which passes through the liver.

– The liver filters sugars from the blood, storing them for later.

Arteries

• The muscular wall of the artery helps the heart pump the blood, able to sustain high pressure

• Blood pressure a measure of the force that blood exerts against a vessel wall~120/80

• Hypertension excessively high blood pressure, results in weakening of heart muscle b/c heart works to hard– When the heart beats, the artery expands as it fills with blood. – When the heart relaxes, the artery contracts, exerting a force that

it strong enough to push the blood along.

• Pulse: the artery keeps pace with the heart, we can measure heart rate by counting the contractions of the artery ~60-80 beats per minute

• The arteries deliver the oxygen-rich blood to the capillaries where the actual exchange of oxygen and carbon dioxide occurs.

ARTERIES

Veins

• The capillaries then deliver the waste-rich blood to the veins for transport back to the lungs and heart.

Veins

• Thin-walled veins can easily be stretched.

• The venous system also plays an important role in regulating body heat– Warm environment: the veins are dilated and

filled with blood, give off heat to the outside and thus keep body temperature constant

– Cool environment: veins contract and distribute a large amount of blood to the chest and stomach

Ulnar

Radial

VEINS

Prevention of Circulatory Conditions

• Exercise regularly• Eat sensibly• Watch one’s weight• Avoid smoking

– Nicotine cause narrowing of blood vessels

Bicuspid valve

Septum

SA node