The Pulmonary Circuit

Carries blood to and from gas exchange surfaces of lungs

The Systemic Circuit

• Carries blood to and from the body
• Blood alternates between pulmonary circuit and systemic circuit

Three Types of Blood Vessels

• Arteries
• Veins
• Capillaries

Arteries

Carry blood away from heart

Veins

Carry blood to heart

Capillaries

• Networks between arteries and veins
• Exchange materials between blood and tissues
• Materials include dissolved gasses, nutrients, waste products

Four chambers of the heart

• Right atrium
• Right Ventricle
• Left Atrium
• Left Ventricle

Right Atrium

Collects blood from the systemic circuit

Right Ventricle

Pumps blood to pulmonary circuit

Left Atrium

Collects blood from pulmonary circuit

Left Ventricle

Pumps blood to systemic circuit

Coronary Sulcus

• Divides atria and ventricles
• Part of the external anatomy of the heart

Anterior Interventricular Sulcus and Posterior Interentricular Sulcus

• Seperates left and right ventricles
• Part of external anatomy of the heart
• Contain blood vessels of cardiac muscle

External Characteristics of the Atria

• Thin walled
• Expandable outer auricle (atrial appendage)
• Each has pectinate muscles (ridges) anteriorly
• left and right separated by interatrial septum

External Characteristics of Ventricles

• inferior, thick walls, lined with trabeculae carneae (muscle ridges)
• left and right separated by interventricular septum
• Left ventricle 3x thicker than right
• Left has same volume as right
• Left is round, right is crescent

Trabeculae Carneae

Line the ventricles and make the contraction of the heart as a whole.

Interatrial septum

Separates atria

Interventricular Septum

Seperates ventricles

Atrioventricular Valves

Between the atria and ventricles

Tricuspid Valve

• Atrioventricular valve on between the right atria and the right ventricle
• Has 3 cusps (flaps)

Bicuspid Valve

• Atrioventricular valve between the left atria and left ventricle
• Has 2 cusps (flaps)

Cusp Attachment

Attached to chordae tendineae from papillary muscles on ventricle wall

What prevents cusps from opening backward during ventricle contraction?

The contraction of papillary muscles

When ventricles are not contracting what happens to the cusps?

Cusps hang loose, allowing the ventricles to fill with blood

Semilunar Valves

• Between ventricles and arteries
• 3 cusps, no chordae tendineae or muscles
• forced open by blood from ventricular contraction
• snap closed to prevent backflow

What makes up the Heart Wall?

• Epicardium
• Myocardium
• Endocardium

Epicardium

• Outer Layer
• Covers the heart
• Visceral pericardium

Myocardium

• Middle Layer
• Muscular wall of the heart
• Concentric layers of cardiac muscle tissue
• Atrial myocardium wraps around great vessels
• Two divisions of ventricular myocardium

Endocardium

• Inner Layer
• Simple squamous epithelium

Valvular Heart Disease (VHD)

Valve function deteriorates to extent that heart cannot maintain adequate circulation

Heart Murmur

leaky valve

Mitral Valve Prolapse

• Murmur of the left AV valve
• Cusps don't close properly
• Blood regurgitates back into left atrium

Congestive Heart Failure

• Decreased pumping efficiency due to diseased valves or damaged muscle
• Blood backs up
• fluid leaks from vessels and collects in lungs and tissues

Cardiomyocytes

Heart muscle cells

Cardiac Muscle Tissue

• Uses actin and myosin sliding filaments to contract
• rich in mitochondria, resists fatigue but dependent on aerobic respiration
• cells connected by intercalated discs

Intercalated discs

• connect cells in Cardiac Muscle Tisse
• consists of desmosomes and gap juntions
• convey force of contraction
• propagate action potentials

Foramen Ovale

• Found in the fetal heart
• 25% of blood bypasses the lungs directly to the left atrium
• Closes at birth

Fossa Ovalis

Scar left after the foramen ovale closes at birth

Ductus arteriosus

• Found in fetal heart
• connects pulmonary trunk to aorta
• 90% of blood bypasses lungs
• Closes at birth

Ligamentum Arteriosum

Scar left after the Ductus arteriosus closes after virth

Blue Baby Syndrome

Failure of either the foramen ovale or the ductus arteriosus to close after birth. Causing poor oxygenation of blood.

Coronary Circulation

• Blood supply to the heart
• Supplies blood to muscle tissue of heart via coronary arteries or coronary veins

Coronary Arteries

• Originate at base of ascending aorta
• Branch to capillary beds for diffusion

Coronary Veins

Blood returns via cardiac veins that join to form coronary sinus whic empty into right atrium

Heart Beat

Single contraction of the heart

Automaticity

Cardiac muscle tissue contracts automatically

Two types of cardiac muscle cells

• Conducting system
• Contractile Cells

Conducting System

• Controls and coordinates heartbeat
• SA node
• AV node
• Conducting cells

Conducting Cells

• AV bundle
• Bundle Branches
• Purkinje fibers

Purkinje Fibers

Connect nodes and myocardium, run down interventricular septum and around apex

Contractile Cells

Produce contractions that propel blood

SA node location

Right atrium wall near superior vena cava

AV node location

Inferior portion of interatrial septum above tricuspid valvle

Conduction through the heart

1. SA node activity and atrial activation begin
2. Stimulus spreads across the atrial surfaces and reaches the AV node
3. There is a 100 msec delay at AV node then atrial contraction begins 150 msec
4. The impulse travels along the interventricular septum within the AV bundle and the bundle branches to the Purkinje fibers, and via the moderator band, to the papilary muscles of the right ventricle. 176 msec
5. The impulse is distributed by the Purkinje fibers and relayed throughout the ventricular myocardium. Atrial contraction is completed. Ventricular contraction begins 225 msec

P Wave

Atrial depolarization (contract)

QRS Wave

Ventricular depolarization (contract)

T Wave

Ventricular repolarization (relax)

The Cardiac Cycle

• The period between the start of one heartbeat and the beginning of the next
• Includes both contraction and relaxation

Two Phases of the Cardiac Cycle

1. Systole
2. Diastole

Phase of Cardiac Cycle

• Atrial systole
• Atrial diastole
• Ventricular systole
• Ventricular diastole

Ventricular Ejection

Ventricular pressure exceeds vessel pressure opening the semilunar valves and allows blood to leave the ventricle.

Stroke Volume

The amount of blood ejected is during ventricular ejection

SV= SYSTOLIC - DIASTOLIC

Cardiac Output

The volume pumped by left or right ventricle in one minute

CO= HR X SV