HeartHeart

Chapter 12Chapter 12

HeartHeartSystem of a pump and pathway for System of a pump and pathway for blood to travelblood to travel

ArteriesArteries- vessels that carry blood - vessels that carry blood aaway from the heartway from the heart

VeinsVeins- vessels that carry blood to - vessels that carry blood to the heartthe heart

CapillariesCapillaries are very small vessels are very small vessels that connect the two at the that connect the two at the microscopic levelmicroscopic level

- Exchange nutrients for wasteExchange nutrients for waste- Exchange O2 for CO2Exchange O2 for CO2

Heart lies in the Heart lies in the pericardial cavitypericardial cavity in the lower portion of the in the lower portion of the mediastinummediastinum resting on the resting on the diaphragm. diaphragm.

The inferior portion has a point or tip The inferior portion has a point or tip called the called the apexapex. .

Broad upper surface called the Broad upper surface called the basebase

The The pericardiumpericardium consists of two consists of two principle portions. principle portions.

1- 1- fibrous pericardiumfibrous pericardium

2- 2- serous pericardiumserous pericardium

Fibrous pericardium: Fibrous pericardium: tough and tough and inelasticinelastic

- rests on and attaches to - rests on and attaches to diaphragmdiaphragm. .

- provides protection- provides protection

Serous pericardium: Serous pericardium:

- thinner, delicate, double layered.- thinner, delicate, double layered.

- 1- Visceral pericardium1- Visceral pericardium: (epicardium): (epicardium)

contacts the surface of the heartcontacts the surface of the heart

- 2- Parietal pericardium2- Parietal pericardium: fused to the : fused to the fibrous pericardiumfibrous pericardium

- Pericardial cavityPericardial cavity: separates two layers : separates two layers with pericardial fluid (lubricates with pericardial fluid (lubricates membranes)membranes) - - cardiac cardiac tamponadetamponade

Heart consists of three layers:Heart consists of three layers:

1- 1- EndocardiumEndocardium: lines inside of heart: lines inside of heart

and heart valvesand heart valves

2- 2- MyocardiumMyocardium: thick heart muscle. : thick heart muscle. Blood supplied by coronary Blood supplied by coronary arteries.arteries.

involuntary, striated, involuntary, striated, intercalated disksintercalated disks

3- 3- EpicardiumEpicardium: smooth outer layer: smooth outer layer

Heart is a double pumpHeart is a double pump

Right side of the heart is the receiving Right side of the heart is the receiving side.side.

- - pulmonary circulationpulmonary circulation

Left side of the heart is the giving side.Left side of the heart is the giving side.

- - systemic circulation systemic circulation (the (the body)body)

Heart has four chambersHeart has four chambers

Two upper chambers are called Two upper chambers are called atriaatria (sing. atrium)(sing. atrium)

Right and leftRight and left

Two lower chambers called Two lower chambers called ventriclesventricles

Right and leftRight and left

Right and left ventricles are separated Right and left ventricles are separated by a thick walled structure called theby a thick walled structure called the

Interventricular septumInterventricular septum

Blood flow between chambers and Blood flow between chambers and larger arteries pass through larger arteries pass through valves.valves.

Valves that connect the upper atria to Valves that connect the upper atria to the lower ventricles are termed the lower ventricles are termed atrioventricular valves atrioventricular valves (AV)(AV). . There are twoThere are two

1- Tricuspid valve1- Tricuspid valve. This “3 flapped” . This “3 flapped” valve connects the right atria to the valve connects the right atria to the right ventricleright ventricle

2- 2- Bicuspid valve Bicuspid valve (mitral): This “2 (mitral): This “2 flapped” valve connect the left atria flapped” valve connect the left atria to the left ventricleto the left ventricle

AV ValvesAV Valves

Valves that connect the lower ventricles Valves that connect the lower ventricles to the larger arteries carrying blood to the larger arteries carrying blood away from the heart are called away from the heart are called semilunar valvessemilunar valves..

1- 1- Pulmonary semilunar valvePulmonary semilunar valve: Valve : Valve located between the right ventricle located between the right ventricle and the pulmonary arteryand the pulmonary artery

2- 2- Aortic semilunar valveAortic semilunar valve: Valve : Valve located between left ventricle and located between left ventricle and aorta.aorta.

Contraction of the heart is Contraction of the heart is systolesystoleRelaxation of the heart is called Relaxation of the heart is called

diastolediastole

When the heart beats the atria contract When the heart beats the atria contract first and together then the ventricles first and together then the ventricles contract second and together.contract second and together.

DeoxygenatedDeoxygenated blood drains into right blood drains into right atrium fromatrium from

- - superior vena cavasuperior vena cava- - inferior vena cavainferior vena cava- - coronary sinus coronary sinus (from heart)(from heart)

Blood is supplied to the heart by the first Blood is supplied to the heart by the first two branches of the aorta, right and left two branches of the aorta, right and left coronarycoronary arteries. These arteries arise arteries. These arteries arise from the base of the aorta and encircle the from the base of the aorta and encircle the heart in the heart in the atrioventricular grooveatrioventricular groove. .

Left coronary arteryLeft coronary artery:: anterior interventricular artery anterior interventricular artery - -

supplies blood to the interventricular supplies blood to the interventricular septum and anterior walls of both septum and anterior walls of both ventricles ventricles

circumflex artery circumflex artery - supplies blood to the - supplies blood to the left atrium and the posterior walls of the left atrium and the posterior walls of the left ventricle left ventricle

Right coronary arteryRight coronary artery:: Posterior interventricular artery Posterior interventricular artery - -

runs to the apex and supplies blood to runs to the apex and supplies blood to the posterior ventricular walls the posterior ventricular walls

Marginal artery Marginal artery - supplies blood to - supplies blood to the myocardium of the right side of the myocardium of the right side of the heart the heart

The myocardium needs a constant The myocardium needs a constant supply of oxygen in order for the heart supply of oxygen in order for the heart to continually pump. Myocardium to continually pump. Myocardium capillaries are branches of cardiac capillaries are branches of cardiac veins which join to form the coronary veins which join to form the coronary sinus, an enlarged vein which empties sinus, an enlarged vein which empties into the right atrium. into the right atrium.

Coronary veins:Coronary veins:

--Great cardiac veinGreat cardiac vein,,

--Middle cardiac veinMiddle cardiac vein, ,

--Small cardiac veinSmall cardiac vein… …

… … drains into cardiac sinus which drains into cardiac sinus which drains into right atrium.drains into right atrium.

Conduction and PacemakerConduction and Pacemaker Conductility- ability to conduct an Conductility- ability to conduct an

electrical impulseelectrical impulse

These impulses These impulses must bemust be coordinated. coordinated.

Intercalated disks are electrical Intercalated disks are electrical connectors that join the muscle connectors that join the muscle fibers.fibers.

Remember: Atria contract together Remember: Atria contract together then ventricles.then ventricles.

Intrinsic

1- Sinoatrial node (SA node) 1- Sinoatrial node (SA node) pacemaker of the heart.pacemaker of the heart.

2- Atrioventricular (AV node)2- Atrioventricular (AV node)

3- Bundle of His- interventricular 3- Bundle of His- interventricular septumseptum

- right and left bundle branches- right and left bundle branches

4- Purkinje fibers- ventricle walls4- Purkinje fibers- ventricle walls

Beating heart

Cardiovascular (CV) center is located in Cardiovascular (CV) center is located in the medulla of the brainstem.the medulla of the brainstem.

Sympathetic nervous system: cardiac Sympathetic nervous system: cardiac accelerator nerves coming off of thoracic accelerator nerves coming off of thoracic spinal cord segments. Increases heart spinal cord segments. Increases heart raterate

Parasympathetic nervous system: Vagus Parasympathetic nervous system: Vagus nerve (CNX) coming off of medulla nerve (CNX) coming off of medulla (brainstem). Decreases heart rate.(brainstem). Decreases heart rate.

Extrinsic

ELECTROCARDIOGRAELECTROCARDIOGRAM (ECG or EKG)M (ECG or EKG)

(Action Potential) (Action Potential) Conduction system can Conduction system can be measuredbe measured

P QRS TP QRS T

P wave: SA node firing and atria contract P wave: SA node firing and atria contract (depolarization)(depolarization)

QRS wave: atria relax (repolarization) and QRS wave: atria relax (repolarization) and ventricles contract (depolarization)ventricles contract (depolarization)

T wave: ventricle walls relax T wave: ventricle walls relax (repolarization)(repolarization)

Myocardial infarctionMyocardial infarction

Elevated ST segment

1- Enlarged P-wave: Atrial hypertrophy1- Enlarged P-wave: Atrial hypertrophy

2- Missing or inverted P-wave: SA node 2- Missing or inverted P-wave: SA node damage.damage.

3- Enlarged Q-wave: Myocardial infarct.3- Enlarged Q-wave: Myocardial infarct.

4- Enlarged R wave: Ventricular 4- Enlarged R wave: Ventricular hypertrophyhypertrophy

5- Abnormal T-wave: Hypoxia or 5- Abnormal T-wave: Hypoxia or hyperkalemia (K+) hyperkalemia (K+)

6- Inverted QRS: Premature Ventricular 6- Inverted QRS: Premature Ventricular Contractions (PVC’s)Contractions (PVC’s)

7- Elevated S-T segment: MI7- Elevated S-T segment: MI

Sinus bradycardiaSinus bradycardiaApart from fit, but otherwise normal Apart from fit, but otherwise normal

individuals, there's a long list of individuals, there's a long list of situations where sinus bradycardia situations where sinus bradycardia occurs, including: occurs, including:

hypothermia; hypothermia; increased vagal tone (due to vagal increased vagal tone (due to vagal

stimulation or e.g. drugs); stimulation or e.g. drugs); hypothyroidism; hypothyroidism; marked intracranial hypertension; marked intracranial hypertension; obstructive jaundice, and even in uremia; obstructive jaundice, and even in uremia; structural SA node disease, or ischemia. structural SA node disease, or ischemia.

Sinus tachycardiaSinus tachycardia Always consider pain as a possible cause Always consider pain as a possible cause

of tachycardia. of tachycardia. Any cause of adrenergic stimulation Any cause of adrenergic stimulation

(including pain); (including pain); thyrotoxicosis; thyrotoxicosis; hypovolemia; hypovolemia; vagolytic drugs (e.g. atropine) vagolytic drugs (e.g. atropine) anemia, pregnancy; anemia, pregnancy; fever fever myocarditis myocarditis

Cardiac cycle

Auscultation of the heartAuscultation of the heart ““Lubb – Dupp”Lubb – Dupp”

““Lubb”: AV valves closing. (S1) SystoleLubb”: AV valves closing. (S1) Systole““Dupp”: Semilunar valves closing. (S2) Dupp”: Semilunar valves closing. (S2)

-Diastole-Diastole

1- Pulmonary valve: ribs 2 & 3 on left1- Pulmonary valve: ribs 2 & 3 on left2- Aortic valve: ribs 2 & 3 on right2- Aortic valve: ribs 2 & 3 on right3- Biscuspid valve: ribs 5 & 6 on left3- Biscuspid valve: ribs 5 & 6 on left

mid line of claviclemid line of clavicle4- Tricuspid valve: ribs 5 & 6 on right 4- Tricuspid valve: ribs 5 & 6 on right

sternal marginsternal margin

Factors Affecting SVFactors Affecting SV

PreloadPreload ContractilityContractility AfterloadAfterload

Frank-Starling Frank-Starling LawLaw

Inotropic: ContractilityInotropic: Contractility-Positive Inotropic Agents-Positive Inotropic Agents

- Sympathetic NS- Sympathetic NS

- Digitalis- Digitalis

- Glucagon (pancreas)- Glucagon (pancreas)

- Epinephrine- Epinephrine

- Hypercalcemia- Hypercalcemia

- Negative Inotropic Agents- Negative Inotropic Agents

- Hyperkalemia- Hyperkalemia

- Hypocalcemia- Hypocalcemia

- Cardiac hypoxia- Cardiac hypoxia

- Cardiac hypercapnia- Cardiac hypercapnia

Chronotropic: Heart RateChronotropic: Heart Rate

- Postive Chronotropic Agents- Postive Chronotropic Agents

- Sympathetic stimulation- Sympathetic stimulation

- Epinephrine- Epinephrine

- Thyroid hormone- Thyroid hormone

- Hypocalcemia- Hypocalcemia

- Hypercapnia (acidosis)- Hypercapnia (acidosis)

- Digitalis- Digitalis

- Negative Chronotropic Agents- Negative Chronotropic Agents

- Parasympathetic NS- Parasympathetic NS

- Acetylcholine- Acetylcholine

- Hypokalemia- Hypokalemia

- Hypercalcemia- Hypercalcemia

- Hypoxia- Hypoxia

HomeostasisHomeostasis