Chapter 20: The Heart

The heart serves as the primarily pump for the human body. It pumps blood through a closed system of…

blood vessels

The heart is a hollow, four chambered, muscular pump located between the…

lungs in the mediastinum of the thoracic cavity.

Size of the heart

a fist (weighs less than 1 pound)

about ____ of the heart is to the left of the midsternal line. The base of the heart is located at the top of the heart.

2/3

The apex

of the heart points towards the left hip

The heart is enclosed and held in place by a double walled sac known as the

pericardium

The pericardium is composed of 2 layers

the fibrous pericardium and serous pericardium

The fibrous pericardium

composed of dense connective tissue. This is a bag that encloses and anchors the heart in place

The serous pericardium

inner membrane that is composed of a parietal layer and visceral later (epicardium)

parietal layer

lines the internal surface of the fibrous pericardium

visceral layer (epicardium)

this layer attaches to the heart muscle (myocardium)

pericardial cavity

space between the parietal and visceral layers. this cavity is filled with serous fluid which prevents friction between the layers as the heart moves

cardiac tamponade

conditions in which excess fluid accumulates in the pericardial cavity. this puts great pressure on the heart limits the heart form fully contracting, therefore, blood flow is reduced to the human body.

pericarditis

inflammation of the pericardium. this is caused by bacteria, viruses.

In pericarditis, serous fluid production is _____; therefore the layers of the pericardium stick together. this restricts heart movements

reduced

Layers of the heart wall

• the epicardium

• the myocardium

• the endocardium

the epicardium

also known as the visceral layer of the serous pericardium. thin, outer, protective layer around the heart

the myocardium

middle layer; composed of cardiac muscle tissue. this layer forms the bulk of the heart wall.

the endocardium

lines the inside of the heart (including the chambers) and it covers the heart vales. this layer is composed of epithelial and connective tissue. Internally, this layer is covered by an epithelial membrane known as endothelium

The heart is composed of 4 chambers

1. 2 superior atria (which are separated by the intertribal septum)

2. 2 inferior ventricles (which are separated by the interventricular septum)

The atria

singular: atrium. these are the small, thin walled upper chambers

what is the atria primary function

is to receive incoming blood from the body. this blood is pumped into the ventricles.

Auricles

small earlobe extensions of the atria that increase the surface area of these chambers

The atria are separated from each other by an

interatrial septum

the inner wall of the atria is covered by a layer of protective muscle known as

pectinate muscle

The Fossa Ovails

is a scar the remains in the adult heart from the Foramen Ovale

The Foramen ovale allows blood to bypass the pulmonary circulation of the fetal heart. Why is this important?

it allows oxygenated blood from the placenta to by pass the non-functional, high pressure, fluid filled lungs, moving directly from the right atrium to the left atrium. This ensure that oxygen rich blood is immediately sent to the left heart and pumped to the developing brain and body.

The Coronary Sulcus

an extreme groove on the heart that separates the atria from the ventricles

Ventricles

• lower heart chambers; these make up most of the mass of the heart.

• 2 of these; right and left. these are the lower chambers

• pump blood to the body; therefore they are much more muscular than the atria

• are separated from each other by a wall known as the inter ventricular septum

Trabeculae Camae

ridges on the internal surface of each ventricles. these prevent the walls of the ventricles from sticking together.

The anterior and posterior interventricular sulci

separates the ventricles on the external surface of the heart

the ductus arterious

is a bypass between the pulmonary artery and the aorta

There are how many valves in the heart?

4

What do heart valves ensure?

that blood flows in one direction through the heart (from atria to ventricles and out of the arteries that attach to the heart)

How do heart valves work?

the valves open and close in response to differences in blood pressure on their 2 side. Once blood passes a valve, the pressure associated with the blood pushes the valve closed, thus preventing back flow of blood within the heart.

How many atrioventricular valves and semilunar valves in the heart?

2 of each

Atrioventricular valves

2 of these; 1 located between each atrium and ventricles. These prevent blood back flow into the atria when the ventricles contact

2 AV valves

the tricuspid valve and biscuspid valve

the tricuspid valve

consist of 3 flaps or cusps and is located between the right atrium and right ventricle. the flaps are primarily connective tissue.

The bicuspid valve

consists of the only 2 flaps and it is located between the left atrium and right atrium. It is also known as the mitral valve

The flaps of the valve are attached to cordlike _____ that attach to the ______ that line the inside of the ventricles. The chordae teninae and papillary muscles together control the AV valves

chordae tendinae; papillary muscles

When the heart is relaxed the AV valves hang down into the _____

ventricular chamber

During contraction what happens?

pressure rises in the ventricles; thus, forcing the valves to close (the cusps are forced together) the chordae tendinae and papillary muscles anchor the valves in the closed position, which prevents the upward movement of blood.

semilunar SL valves

2 of these, located. between the ventricles and the major arteries attached to the heart. These prevent blood from back flowing into the ventricles.

Each semilunar valve is compose of _____

3 half moon shaped cusps

When the ventricles contract, the blood pushes the SL valves open against the

wall of the arteries. When the ventricles relax, blood in the arteries pushes the valves closed, thus preventing blood from flowing backwards.

The pulmonary semilunar Valve and the aortic semilunar valve are the

2 SL valves

valve related disorders

• incompetent valve

• valvular stenosis

• mitral valve prolapse

incompetent valve

the valve does not open and close. due to this, the heart has to pump the same blood over and over again. this is very inefficient

Valvular Stenosis

valve flaps become stiff and constrict the opening. the heart work harder in this case.

Mitral valve Prolaspe

in about 1% of the population. most common in young women. In this situation, the flaps become incompetent. the position can be genetic. Again, this causes great inefficiency in the heart. in most cases, the faulty valves are replaced with synthetic valve or pig heart valves.

Pulmonary circulation

carried out the by the right side of the heart. in this circulation, blood is pumped to the lungs and back to the left side of the heart.

systemic circulation

carried out by the carried out by the left side of the heart. In this circulation pattern, blood is pumped to and form the body.

coronary circulation

blood flow to and from the heart muscle

the left coronary artery

carried blood to the wall of the heart. this artery branches to form the anterior interventricular branch (which carries blood to the apex of the heart) and the circumflex branch (which carries blood to then atrium and the posterior portion of the heart wall)

the right coronary artery

supplies blood to the wall of the right atrium and to the SA node

Blood enters the right atrium via the _____ and ______. this deoxygenated blood

superior; interior vena cava

The right atrium contracts. This pushes blood past the ____ to the right ventricle. Once blood fills the right ventricle, then the tricuspid valve closes to prevent the back flow of blood.

tricuspid valve

The right ventricle contacts to push blood past the pulmonary _____ through the ______ into the lungs

semilunar valve; pulmonary truck (artery)

In the capillaries of the lungs, the blood gives up_____ and picks up

carbon dioxide; oxygen

This oxygenated blood returns to the left atrium via the _____. this ends ______

pulmonary veins, pulmonary circulation

Next the _____ contacts to force blood past the _____ valve into the left ventricle. Once the left ventricle is filled with blood, the mitral valve closes to prevent the back flow of blood.

left atrium; mitral (bicuspid)

The ______ contracts to force blood past the aortic _______ into the ______ and on to all parts of the body. this is _____

left ventricle, semilunar valve, systemic circulation

coronary arteries

carry oxygenated blood to the myocardium. The left anterior descending artery branches into the arteries inter ventricular artery and the circumflex artery.

The circumflex artery

supplies the external portions of the left atrium and left ventricles with oxygen. The left anterior descending artery is often referred to as the “widow maker”

Coronary Circulation

Deoxygenated blood form the myocardium empties into cardiac veins which empty into the coronary sinus of the right atrium.

Angina Pectoris

inadequate blood supply to the myocardium. This leads to pain and tightness in the chest and arm.

what does angina pectoris lead to and how is it treated

• pain and tightness in the chest and arm.

• with nitrates which dilate blood vessels.

• Stress/increased physical demands on the heart can cause this.

Ischemia

reduced oxygen supply to the heart

Myocardial infarction

heart attack or coronary

Infarction

death of tissue due to interrupted blood supply.

What does infarction often caused

a blockage in one of the coronary arteries. The blockage can be caused by a blood clot, fat, etc.

What can a infarction be treated with

streptokinase (thru a catheter) which dissolves clots. Surgery may also be an option

Cardiac muscle is _____ and ______. It contracts via the _____

striated, involuntary, and sliding filament.

Intercalated disc

only in cardiac muscle fibers. These provide support and strength to contracting muscle fibers.

Cardiac fibers exhibit _____, that’s it the fibers contract in a coordinate fashion.

autrorhythmicity

cardiac muscle fibers contain numerous mitochondria which are involved in

ATP (by aerobic cellular respiration)

cardiac muscle has a very limited ability for

repair and regeneration

the cardiac conduction system

ensures that heart contractions (beat) are well coordinated

In a normal heartbeat:

the 2 atria contract (while the 2 ventricles relax), then the 2 ventricles contracts (while the 2 atria relax)

Autorhythmic cells

make up the cardiac conduction system. these are specialized neurons.

What are Autorhythmic cells made up of

• sinoratrial node

• atrioventricular node

• atrioventricular bundle (bundle of his)

• right and left bundle branches

• purkinje fibers

Impulses (electrical signals) produce contractions of heart muscle also known as

the heartbeat

the sinoatrial node

located in the right atrial wall. This structure produces impulses that begin heart muscle contraction.

The SA node is the ______ of the heart. It generates about _____ impulses per min in a resting individual.

pacemaker, 75

the impulses in the SA node produced here speed to both _____

atria

The SA node also sets the rhythm for the entire heart. It can _____

speed up or speed down heartbeat in response to body activity.

SA node (sinoatrial node) The pacemaker

• starts the heartbeat

• sends the first electrical signal

• located in the right atrium

Atria contract

• the signal spreads across the atria

• atria squeeze and push blood into the ventricles

AV node (Atrioventricular node) the pause bottom

• slows the signal for a split second

• this gives ventricles time to fill with blood

bundle of his -→ bundle branches → prukinje fibers

• carries the signal down into the ventricles

• spreads the signal quickly

ventricles contract

• blood is pumped out to the lungs and body

SA → AV→bundle → branches → purkinje → pump (cardia conduction simplified)

Ways to remember: “top starts, middle pauses, bottom pumps”

The AV bundle

is the only connection between the atria and ventricles.

The AV bundle impulses then move into and through the ______ via the _________

interventricular septum, right and left bundle branches

Purkinje fibers

carry impulses completely through the interventricular septum and to the apex of the heart

Problem/Disorders associated with the cardiac conduction system

Arrythmias, Fibrillation, Ectopic Focus

Arrythmias

irregular heart rhythm.

The arrythmias includes

tachycardia and badycardia

tachycardia

abnormally fast heart rate; greater than 100 beats/minute.