Anatomy of the Cardiovascular

System

Cardiovascular System• As Also circulatory system• Consists of:

1. the heart, 2. arteries, 3. veins, 4. capillaries

Heart• Four chamber muscular organ• Comparable to the size of a closed

fist• Located in the mediastinum

– Behind sternum– Between 2nd and 6th ribs– Between T5-T8

• Apex – base of heart – Located at the 5th intercostal space

Heart

Coverings of the Heart1. Pericardium – loose fitting sac

surrounding the heart– Fibrous pericardium – tough, loose-

fitting, inelastic– Serous pericardium

• Parietal layer: lines the inside of the fibrous pericardium

• Visceral layer: adheres to outside of the heart

– Pericardial space: between parietal and visceral layer• Filled with 10-15mL of pericardial fluid• Decreases friction

Walls of the Heart2. Epicardium – outer layer

– Epicardium = serous pericardium3. Myocardium – thick, contractile layer

composed of cardiac muscle cells– Intercalated disks contain many gap junctions– Allow cardiac muscle cells to function as a single

unit syncytium4. Endocaridium – interior of cardiac wall

– Endothelial tissue– Covers projections of myocardial tissue called

trabeculae

Walls of the Heart

Chambers of the Heart• Atria – two superior chambers

– “Receiving chambers”– Blood from veins enters atria

• Ventricles – two inferior chambers– “pumping chambers”– Thick muscular walls to increase force of

pumping action• Left > right

– Separated by interventricular septum

Valves of the Heart• Permit blood flow in one direction

during circulation• Atrioventricular valves (AV valves)

– Also cuspid valves– Between atria and ventricles

• Semilunar (SL valves)– Between R ventricle and pulmonary

arteries and L ventricle and aorta

Atrioventricular Valves• Tricuspid valve

– Btwn R atrium and ventricle– 3 flaps of endocardium– Connected to ventricular papillary

muscle via chordae tendinae• Bicuspid valve

– Btwn L atrium and ventricle– Also called mitral valve– Two flaps of endocardium

Semilunar Valves• Pulmonary semilunar valve

– Btwn R ventricle and pulmonary trunk• Aorta semilunar valve

– Btwn L ventricle and aorta

Chambers & Valves

Trace the blood flow through the heart

Blood Supply to the Heart• Right and left coronary arteries

– First branches off aorta – Right coronary artery right marginal

artery & posterior interventricular artery– Left coronary artery circumflex artery

& anterior interventricular artery– Most of the blood goes to the L ventricle– In 50% of the population, the R coronary

artery is dominant

Blood Supply to the Heart• Anastomosis: Connections between blood

vessels that allow for collateral circulation• Few exist between large branches of

coronary arteries• In presence of an obstruction in a large

artery ischemia will result to a large area of tissue– Myocardial infarction (MI) (aka heart attack)

• Anastomoses do exists between smaller branches of the R and L coronary arteries

Blood Supply to the Heart• After traveling through the capillaries

of the heart, blood empties into the R atrium via the coronary sinus

Warming Up I 1. The apex of the heart rests on the:2. True/False: The epicardium and the

fibrous pericardium are the same structure.

3. What is the correct order of the layers of the heart from outside to inside?

4. The ____________ connect the cuspid valves to the papillary muscles.

5. What is an anastomosis?6. What is also known as the pacemaker of

the heart?

Types of Blood Vessels• Artery – carries oxygenated blood

away from the heart– “distributors”– Arteriole: small artery– Precapillary sphincters: regulate the

blood flow into capillaries

Types of Blood Vessels• Vein – carries unoxygenated blood

towards the heart– Great ability to stretch (capacitance)– Function as reservoirs: blood pools in

the valves then is pushed forward from the pumping pressure

– Venules: small vein

Types of Blood Vessels

Types of Blood Vessels• Capillaries – arterial system switches

to venous system– “primary exchange vessels”– Transport materials to and from the cells– Speed of blood flow decreases to

increase contact time– Microcirculation: blood flow between

arterioles, capillaries and venules

Types of Blood Vessels

Structure of Blood Vessels• Tunica adventitia - outermost layer

– Fibrous connective tissue– Holds vessels open; prevents tearing of

vessels walls during body movements– Larger in veins than arteries

• Tunica media – middle layer– Smooth muscle and elastic CT– Helps vessels constrict and dilate– Larger in arteries

Structure of Blood Vessels• Tunica intima – innermost layer

– Composed of endothelium– Semilunar valves present in veins– One cell thick in capillaries

Circulatory Routes • Systemic Circulation – blood flow

from the L ventricle to the body & back to the R atrium

• Pulmonary Circulation – blood flow from the R ventricle to the lungs and back to the L atrium

Circulatory Routes

Aorta

Systemic Arteries• Arch of aorta• Subclavian (L and R)• Brachiocephalic• common carotid (L and R)• Axillary (L and R)• Brachial (L and R)• Radial• Ulnar

• Abdominal aorta• Common iliac• External iliac• Femoral• Popliteal• Posterior tibial• Anterior tibial• Dorsal pedis

Systemic Veins• Superior vena cava• Inferior vena cava• External jugular• Internal jugular• Brachiocephalic (L and R)• Subclavian (L and R)• Cephalic• axillary

• Basilic• Median basilic• Median cubital• Common iliac• External iliac• Femoral• Popliteal• Great saphenous• Small saphenous

Fetal Circulation• Two umbilical arteries carry blood to the

placenta• The placenta allows for exchange of

oxygen and nutrients from the mother. Maternal and fetal blood do NOT mix.

• Umbilical vein returns oxygenated blood and enters fetus via the umbilicus

• Foramen ovale – hole btwn the R and L atria– Allows for blood to bypass the R ventricle and

pulmonary circulation

Fetal Circulation• Ductus arteriosus – small vessel

connecting the pulmonary artery and the aorta– Allows for another bypass route from the

lungs

**Most of fetal blood is a mixture of oxygenated and deoxygenated

blood**

Fetal Circulation