THE CARDIOVASCULAR

SYSTEM

Emily Todd

Michelle Rodrigues

Caileigh Allegrini

Jenny Alvarado

What does the human cardiovascular system consists of?

The cardiovascular system consists of the heart, blood vessels, veins and arteries.

Why is the heart important?

The heart is one of the most important organs in the entire human body.

It is one of the first organs to form. Why? Because it when the embryo first starts, it recieves the necessary nutrients from its surroundings, but as the embryo grows, it becomes hard for the nutrients to reach all the cells.

The heart functions as a pump and is composed of muscle.

The heart pumps blood, which carries all vital materials through our body.

Our entire body relies on the heart.

How does the heart begin?

The heart derives from Mesoderm.

Mesoderm is the middle layer of an embryo in early development.

The Primitive Heart The primitive heart tube is the earliest stage of

heart development. The primitive heart tube consists of the bulbus

cordis,

a ventricle, atrium, sinus venosus, and

vitelline veins. All five embryonic dilatations of the

primitive heart develop into the adult

structures of the heart. The primitive hearts begins beating

once it has formed

Embryonic Heart Looping: The linear tube begins to bend upward

to the right. Why does lopping occur?

Looping occurs because it’s the hearts way of transforming the single heart tube to a more complex structure with two atria and two ventricles.

Embryonic Heart Looping: The heart continues bending which causes

chamber structures to form. The heart forms two atriums and one large ventricle. As bending continues, the heart divides that one large ventricle in half, which ultimately leaves you with a left and a right ventricle are. The total of chambers formed in the heart during looping is 4.

Partitioning of the heart includes: Atrial Septation: Ventricular Septation: Atrioventricular Valve formation: Division of the outflow tract:

Atrial septation: This process occurs during week 5 of development. How? The septum primum grows from the ventral and

posterior walls of the atrium. The septum secundum forms a ridge on the dorsal

and posterior walls of the atria, but doesn’t not fuse with endocardial cushioning, allowing the foramen ovale to remain open, which allows maternal circulation until the baby is born.

EMBED VIDEO HERE http://www.youtube.com/watch?v=NCDdoSfdQBo

Ventricular Septation:

Ventricular septation is a complex process involving many surrounding structures to form dividing ridges positioned at various planes.

This eventually leads to a complete separation of the right and left ventricles.

Development of the outflow tract: What is the outflow tract?

The Outflow tract is a portion of the left ventricle of the heart through which blood passes in order to enter the greater arteries.

The first indication of a developing

septum is the appearance of two ridges

projecting into the outflow tract from

opposite sides. these ridges spiral in

counter-clockwise direction up the

developing outflow tract.

Stages of development the fetal heart resembles the structures of animals hearts

FISH VS EARLY STAGES OF HEART 

In the early stages when the heart looks like a tube, it is similar to a fish heart.

FROG VS TWO CHAMBER HEART

when the fetus heart begins to take shape and form two chambers, it resembles a frog’s heart

TURTLE VS THREE CHAMBER HEART:

After the fetal heart has developed two atriums and one large ventricle, it looks similar to a snake or turtle heart.

Does the heart continue changing? At birth you have a fully functional heart,

which does not under go any drastic changes as you get older.

As you grow and get bigger, your heart gets bigger too.

Invertebrates

Simple heart and vessels Open circulatory system Single circulation

Vertebrates

Heart, blood vessels (veins, arteries, capillaries), blood

Closed circulatory system Double circulation Increase in metabolic demand

Single vs. Double Circulation

Single: One atrium, one ventricle, the heart draws in deoxygenated blood in a single atrium and pumps it out to a ventricle. Includes a two chambered heart

Double: Pathway that enables the blood to flow from the heart to lungs and return back to the heart for systemic circulation. Includes a three or four chambered heart

Fish Single circulation Four chambers: sinus venosus, atrium,

ventricle, bulbus arteriosus One way valves including the sino atrial

valve and atrioventricular valve prevent the backflow of blood between chambers

Semilunar valve (located in bulbus arteriosus) to prevent reverse blood flow from the ventral aorta

Evolution

The transition from aquatic life to terrestrial life brought about many different accommodations to the new modes of life

Amphibians Three chambers: right atrium, left atrium, one

ventricle Right and left atrium divided by an interatrial

septum Has a sinus venosus and conus arteriosus Has two semilunar valves and an atrioventricular

valve Spiral valve within the conus arteriosus The ventricle of a frog heart lacks a septum but

has a trabeculae instead Double circulation

Reptiles Three chambers: two atria, one ventricle Ventricle divided into the cavum venosum,

cavum pulmonale, and cavum arteriosum Cardiac shunt cuts off blood supply to lungs One-way lunar valves at the conus

arteriosus and an atrioventricular valve Double circulation Conus arteriosus and a smaller sinus

venosus than amphibians and fish

Crocodile

Four chambers: two atria, two ventricles Ventricle has a complete septum Unique feature called foramen of

Panizza that cuts off blood supply to lungs while diving

pair of atrioventricular valves

Mammals & Birds Four chambers: two atria, two ventricles Double circulation Sinus venosus is minimized into a patch of Purkinje fibers

(AKA sinoatrial node) Birds have very small sinus venosus Conus arteriosus is transformed into pulmonary and aortic

trunk Considered the perfect heart due to complete internal heart

septa Oxygenated and deoxygenated blood can never mix The chance of backflow of blood becomes greater with

increase in heart chambers Valves developed in the heart to prevent backflow of blood

into the wrong chambers

Mammalian Heart Valves

The human heart has 4 heart valves: Bicuspid mitral valve Tricuspid valve (right atrioventricular

valve) Aortic valve Pulmonary valve (semilunar valve)

Heart Valves Bicuspid mitral valve: separates the left

atrium from the left ventricle Tricuspid valve: separates the right

atrium from the right ventricle Aortic valve: separates the base of the

left ventricle with the aorta Pulmonary valve: separates the base

of the right ventricle with the pulmonary artery

Anatomy & Function of Mitral Valve

Prevents the backflow of blood into the atrium 2 cusps 4-6 cm2 in size Opening surrounded by fibrous ring known as the mitral

valve annulus Valve cusps do not balloon into the left atrium because of

the chordae tendineae Chordae tendineae are attached to papillary muscles and

valve cusps The intraventricular pressure forces the valve to close

when the left ventricle contracts Tendons help the cusps fit together and prevent the valve

from opening in the wrong direction

Mitral Valve Prolapse (MVP)

Most common heart valve abnormality Effects mostly women between the ages

of 20-40 One or both of the flaps are too large Mitral valve does not close evenly with

each heartbeat Causes regurgitation (the backward

leaking of blood) – leads to heart murmur

Symptoms & Treatments Symptoms: chest pain, irregular heartbeat,

increased heart beat after exertion, other blood flow complications

In rare cases: formation of blood clots on the valve, puts patient at high risk for stroke

Treatment: medications, specifically beta-blocker, surgery to repair or replace the mitral valve

Severe mitral regurgitation often leads to an enlarged heart causing heart failure

Severe cases where the valve cannot be repaired, only replaced, the patient is subject to a lifetime of blood thinners to prevent blood clotting.

Physiology of the heart

Conduction system Transportation of the blood in the heart

Conduction system How the heart contracts!

heart contracts as a direct result of electrical potential that travels through the myocardium cells of the heart.

There are 5 components to the conduction system that aid in the contraction of the heart:

Sinatrial (SA)  node                                                                

Atrioventricular (AV) node                                                                                                                                 Bundle of His                                                                                                                                     Left/Right bundle branches

Conduction system The SA node ( the pacemaker) located at the top of the right atria is the

portion of this system that generates the impulse; providing the stimulus for contraction.

The impulse continues to the AV node. At the AV node which is located at the bottom portion of the right atria, the atria is contracted and the electrical impulse is paused, because the atria needs to complete its contraction.

Once the contraction is complete the electrical impulse is passed through the bundle of his, and then to the left/ right bundle branches that are located within the interventricular septum, and lastly to the Purkinje fibers.

The Purkinje fibers are located in the muscle walls of the ventricle. Since the ventricle of the heart is very large it is essential that the Purkinje fibers depolarize the contractile cells of both ventricles; causing them to contract.

http://www.youtube.com/watch?v=te_SY3MeWys

Transportation of the Blood in the Heart

Occurs in 2 phases: Diastole Phase ( relaxation of the atria and the ventricles)

                                  

Systole Phase ( Ventricles contract)

In the Diastole Phase, which occurs first in the heart represents the relaxation of the atria and ventricle as it refills with blood. During this time the atrioventricular valves are open.

Deoxygenated blood enters through the superior and inferior vena cava to the right atria. Since the atrioventricular valve (which separates the atria from the ventricle) is opened, the blood can continue through the atria into the right ventricle.

As the blood enters through the right ventricle an impulse from the SA node is created and allows the right atria to contract.  The right atrium empties out all its blood into the right ventricle, and the atrioventricular valve closes to prevent the back flow of blood.

At the right ventricle and electrical impulse from the Purkinje fibers allows the ventricle to contract, this is the beginning of the Systole phase which occurs when the ventricles are contracted. The blood pushes through the opened pulmonary valve (one of the semi lunar valves) to the pulmonary artery.

The deoxygenated blood then travels to the lungs where carbon dioxide is released and oxygen is absorbed.

Transportation of the Blood in the Heart

Once oxygenated the blood returns to the heart it enters in through the pulmonary veins and there is another Diastole phase. The pulmonary veins carrying oxygen rich blood continues flowing to the left atrium. The mitral valve (one of the atrioventricular valves) is opened, so blood can easily flow to the left ventricle. Once again the SA node triggers an impulse and contracts, so does the left atria. The blood is emptied in the left ventricle and the mitral valve closes.

From the left ventricle the Systole phase occurs. The Purkinje fibers contract and the left ventricle moves blood through the aortic valve (one of the semi lunar valves) to the aorta, where it is distributed to the rest of the body.

http://www.youtube.com/watch?v=JA0Wb3gc4mE

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What the Health Magazine. [Internet]. Published by What the Health Magazine. [cited 2012 Dec 10] Available from http://whatthehealthmag.files.wordpress.com/2011/02/818pills.jpg

Warkentin, D.S. 2012. Mitral Valve Prolapse [Internet]. Summit Medical Group; [cited 2012 Dec 10]. Published by RelayHealth. Available from http://www.summitmedicalgroup.com/library/adult_health/car_mitral_valve_prolapse/

Cardiac Conduction System [Internet]. 2009 Nov 21.):John Winters;.Available from:http://ecg-experts.blogspot.com/2009/11/cardiac-conduction-system.html

mdmedicine . 2011 April 11. Heart Conduction System [Internet] .Available from:http://mdmedicine.wordpress.com/2011/04/24/heart-conduction-system/

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