Chapter 22: Heart

Heart

________ connects to blood vessels that transport blood between this and body tissues

Arteries

send blood away from heart

Veins

Bring blood back to heart

Capillaries

serve as the sites of exchange (between blood and alveoli, or between blood and systemic cells)

Great vessels

The arteries and veins entering and leaving the heart are called

unidirectional

Heart valves ensure its blood flow is

lungs; body tissues

• The heart is two side-by-side pumps that work at the same rate and pump the same volume of blood

  • One pump directs blood to the lungs

  • One pump directs blood to body tissues

blood pressure

• The heart generates ______________ through alternate cycles of contraction and relaxation

  • This is the force of the blood pushing against the inside walls of blood vessels

  • It is essential to circulate blood throughout the body

Pulmonary circulation

• Starts with right side of heart pumping deoxygenated blood through pulmonary arteries to capillaries in lungs

• After oxygen pickup and carbon dioxide release, pulmonary veins carry blood to left side of heart

Systemic circulation

• Left side of the heart pumps oxygenated blood through systemic arteries to systemic capillaries

• Nutrients, respiratory gases, and wastes are exchanged, and systemic veins carry the blood back to the right side of the heart

Cardiovascular system

Mediastinum

Heart located slightly left of midline, deep to the sternum, in space called the

Right; Left

Heart is slightly rotated so _______ border is located more anteriorly while the _______ border is located more posteriorly

Base

_____ of heart: its posterosuperior surface—mainly left atrium

Superior border

___________ of the heart is formed by the great arterial vessels and the superior vena cava

Apex

inferior conical end of the heart

Inferior border

formed by the right ventricle

Borders of the heart

Heart and lungs, anterior view

Serous membranes of the heart + cross-sectional view in CT scan

pericardium

• Heart is enclosed within a tough sac called the __________ (pericardial sac)

• Restricts heart movements so that it moves only slightly within the thorax; prevents heart from overfilling with blood

Fibrous pericardium

tough outer sac

Serous pericardium

composed of parietal and visceral layers

Pericardial cavity

thin potential space between layers of serous pericardium containing serous fluid

1. Epicardium

2. Myocardium

3. Endocardium

Three layers in heart wall (from superficial to deep):

Epicardium

visceral layer of serous pericardium and areolar connective tissue

Myocardium

cardiac muscle; thickest of the three layers

Endocardium

internal surface of heart chambers; simple squamous epithelium and areolar connective tissue

2 atria and 2 ventricles

Heart is composed of four chambers

Atria

Two superior, smaller chambers of the heart

Ventricles

two inferior, larger chambers of the heart

Auricle

Anterior part of each atrium forms a flaplike extension called an _______

Coronary sulcus

groove separating atria and ventricles

Anterior interventricular sulcus and inferior interventricular sulcus

Sulci located between the ventricles

External anatomy and features of the heart- Anterior

External anatomy and features of the heart- Posterior

Right atrium, right ventricle, left atrium, left ventricle

Name the 4 hollow chambers that make up the heart.

2 Atrioventricular (AV) Valves

Their closure causes the first heart sound “lubb”

semilunar valves

• Two ___________ at base of great arteries

• Their closure causes the second heart sound “dupp”

Internal anatomy of the heart

Fibrous skeleton of the heart

• Formed from dense regular connective tissue between the atria and ventricles

• Provides structural support at boundary between atria and ventricles

• Forms supportive fibrous rings to anchor heart valves

• Provides framework for attachment of cardiac muscle

• Acts as an electrical insulator to prevent action potentials in atria from passing to ventricles, so that ventricles don’t contract at the same time as the atria

Right atrium

receives venous blood from heart and systemic circulation through the superior vena cava, inferior vena cava, and coronary sinus

superior vena cava, inferior vena cava, and coronary sinus

Right atrium receives venous blood from heart and systemic circulation through the __________________

Interatrial septum

divides right atrium from left; fossa ovalis present in interatrial septum

Fossa ovalis

present in interatrial septum

Pectinate muscles

ridges on internal surface of atrial wall

Right Atrioventricular (AV) Valve

ensures one-way blood flow from right atrium to right ventricle through right atrioventricular opening

Right ventricle

receives deoxygenated blood from right atrium

Interventricular septum

thick wall between right and left ventricles

trabeculae carneae

Inner wall of each ventricle displays irregular muscular ridges called ____________

Papillary muscles

cone-shaped muscle projections anchoring chordae tendineae

chordae tendineae

attach muscle to atrioventricular valve and prevent cusps from flipping into atrium when ventricle contracts

Septomarginal trabecula

connects anterior papillary muscle of right ventricle to atrioventricular septum

Conus arteriosus

smooth funnel-shaped region at superior end of right ventricle leading to pulmonary semilunar valve

Semilunar valve

ensures one-way flow from ventricle to pulmonary trunk

pulmonary arteries

Pulmonary trunk divides into right and left _______________

Left atrium

Oxygenated blood from the lungs travels through the pulmonary veins to the

Left atrioventricular valve

• controls flow through opening between left atrium and ventricle

• Also referred to as the bicuspid valve (two cusps) or mitral valve

• Valve is forced shut when the left ventricle contracts

Left ventricle

pumps blood through entire systemic circulation, Generates very high pressure

Aortic semilunar valve

controls flow from left ventricle to aorta; located at superior end of left ventricle

Wall of left ventricle

• _______________________ is about three times thicker than right ventricle

• Must generate enough pressure to force blood through entire systemic circulation

• Right ventricle only needs to pump blood to the nearby lungs

Ventricular walls

Right and left coronary artery

travel within coronary sulcus and supply heart wall with oxygen and nutrients and branch off ascending aorta just superior to aortic valve

Right marginal artery and inferior interventricular artery

Right coronary artery branches into 2 branches, name them

Right marginal artery

supplies right border of heart

Inferior interventricular artery

supplies posterior surfaces of the left and right ventricles

Anterior interventricular artery, Circumflex artery

Left coronary artery branches into 2, name them

Anterior interventricular artery

also called left anterior descending artery; supplies anterior surface of both ventricles and most of the interventricular septum

Circumflex artery

supplies the left atrium and ventricle

Coronary arteries

coronary sinus

The three major cardiac veins drain into the ____________, which drains into the right atrium

Great cardiac vein, middle cardiac vein, small cardiac vein

Name the 3 major cardiac veins

Great cardiac vein

runs alongside anterior interventricular artery

Middle cardiac vein

runs alongside inferior interventricular artery

Small cardiac vein

travels close to the right marginal artery

Coronary veins

conduction system

• For the heart to be an effective pump, contraction of chambers needs to be coordinated

• This is possible due to the heart’s ____________

capillary networks

Cardiac muscle is striated with extensive ________________ (similar to skeletal muscle)

Characteristics of Cardiac Muscle Tissue

• Less SR quantity and organization

• No terminal cisternae

• Less contact between SR and T-tubules

Organization and Histology of Cardiac Muscle

Longitudinal view of cardiac muscle cell

Longitudinal section of cardiac muscle

gap junctions

Cardiac muscle fibers contract as a single unit because they are all connected with _______________

intercalated discs

Gap junctions are parts of _______________ between adjacent fibers

electrical impulse

Each _______________ is distributed immediately and spontaneously throughout the myocardium

Desmosomes

_____________ within intercalated discs prevent cardiac muscle cells from pulling apart

autorhythmicity

Heart exhibits _______________—it initiates its own heartbeats

Conducting system

consists of specialized cells that start and propagate electrical impulses to contractile cells

Sinoatrial node, Atrioventricular node, Atrioventricular bundle, Left and right bundle branches, Subendocardial branches (Purkinje fibers)

Passage of signals through the conducting system:

sinoatrial (SA) node

• Electrical impulse begins here (heart’s pacemaker)

• located on posterior wall of right atrium adjacent to the opening of the superior vena cava

atrioventricular (AV) node

• Impulse from SA node travels via gap junctions to left atrium and ________________ on the floor of right atrium

• Impulse is paused at AV node delaying activation of ventricles as they fill with blood

atrioventricular (AV) bundle (bundle of His)

Impulse leaves AV node, enters the ________________, extending into interventricular septum

left and right bundle branches

Once within the septum, the AV bundle divides into ______________________

subendocardial branches (Purkinje fibers)

• The left and right bundle branches pass the impulse to ___________________ that begin at the heart apex

• spread the impulse superiorly from the apex to all of the ventricular myocardium

Conducting system of the heart

Electrocardiogram (ECG)

a composite tracing of all electrical impulses in heart; can be used diagnostically

P wave

atrial depolarization

QRS Wave

ventricular depolarization (and atrial repolarization)

T wave

ventricular repolarization

Electrocardiogram example