Cardiovascular System

CARDIOVASCULAR SYSTEM

is composed of the :HeartBlood Blood vesselsThe blood vessels of the body represent a closed delivery

system, which functions to transport blood around the body, circulating substances such as oxygen, carbon dioxide, nutrients, hormones and waste products.

THE HEART

Anatomy of the Heart

LOCATION: inferior mediastinum. MEDIASTINUM - the middle cavity of the thorax.

                    : flanked on each side by the lungs.                   

APEX - more pointed part and is directed toward the left hip and rests on the diaphragm, : approximately at  the level of the fifth intercostal

spaces.BASE - broader posterosuperior aspect

: points toward the right shoulder lie beneath the second rib.

SIZE: approximately a size of a person's fist. : weigh less than a pound. : cone-shaped : hollow

Location of the heart in the thorax

COVERINGS and WALL        

PERICARDIUM - a double sac of serous membrane.       

EPICARDIUM or VISCERAL PERICARDIUM - tightly hugs the external surface of the heart and is actually part of the heart wall.       

 PARIETAL PERICARDIUM - which is reinforced on its superficial face by dense connective tissue the FIBROUS PERICARDIUM, which helps protect the heart and anchors it to surrounding structures, such as the diaphragm and sternum.

        SEROUS PERICARDIAL MEMBRANE - produces a slippery lubricating fluid that allows the heart to beat easily in a relatively frictionless environment.

HOMEOSTATIC IMBALANCE:        

PERICARDITIS is an inflammation of pericardium. Often results in a

decrease in the amount of serous fluid.

THREE LAYERS OF HEART WALLS         

1. Epicardium- outermost layer  2. Myocardium-consists of thick bundles of cardiac muscle twisted and whorled into ring like arrangements.                              -reinforced internally by dense fibrous connective tissue network called "skeleton of the heart". 3. Endocardium- a thin glistening sheet of endothelium that lines the hearts chambers.

Chambers and Associated Great Vessels4 Hollow chambers or cavities:

2 atria - receiving chambers2 ventricles - discharging chambers or actual pump of the heart.

Interventricular/Interatrial Septum –divides the heart

longitudinally.

Pulmonary CirculationLeft side of the heart is the

pulmonary circuit pumplarge superior and inferior

vena cava pulmonary trunk right and left pulmonary arteries four pulmonary veins.

Systemic Circulationright side of the heart is the

systemic circuit pumpleft side of the heart aorta

systemic arteries body tissues systemic veins right atrium superior or inferior vena cava .

Valves4 Valves:1. First set of atrioventricular or AV Valves.

a. Biscupid/Mitral Valve -the left AV valve -consist of 2 flaps or cusps of endo cardium.

b. Triscupid Valve -the right AV valve -it has 3 flaps

-located between the atrial and ventricular chambers on each side. -it prevents the backflow of blood into the atria when the ventricles

contract. -open during heart relaxation and closed when ventricles are

contracting.

Chordae Tendineae“tendinous cords”

Tiny white cords that anchors the flaps to the walls of the ventricles

2. Second set of Semilunar Valves a. Pulmonary semilunar valveb. Aortic semilunar valve

-guards the bases of the two large arteries leaving the ventricular chambers.

-each has 3 leaflets that fit tightly together when the valves are closed.

-closed during heart relaxation and are forced open when the ventricles contract.

Homeostatic ImbalanceIncompetent valve – forces the heart to

pump and repump the same blood because the valve does not close properly and blood back flows.

Valvular Stenosis -a condition in which the valve flaps

becomes stiff, often because of repeated bacterial infection of the endocardium (endocarditis).

Cardiac CirculationCoronary Arteries – provides the blood

supply that nourishes the heart. Coronary Sulcus (atrioventricular groove)

- this contains the trunks of the nutrient vessels of the heart, and is deficient in front, where it is crossed by the root of the pulmonary artery.

Major Branches of Coronary Arteries

Left: anterior interventricular and circumflex arteriesRight: posterior interventricular and marginal arteries Coronary Sinus – an enlarge vessel at

the back side of the heart where cardiac veins empty.

Homeostatic Imbalance

Angina Pectoris -a crushing chest pain which is due to the

oxygen deprivation in the myocardium. -if it is prolonged, the schemic heart cells

may die forming an infarct (myocardial infarction/heart attack).

Physiology of the heart

6000 quarts of blood – the amount of blood the heart pumps everyday.

(6 quarts (6L) of blood pushed over 1000 times through the blood vessels)

Intrinsic Conduction System of the Heart: Setting the Basic Rhythm

Muscle cells contract involuntarilyMuscle cells in different areas of the heart

have different rhythms.Atrial cells – beat about 60 times / minuteVentricular cells – beat about 20 – 40 /

minute

2 Systems that Act to Regulate Heart Activity

1. Nerves of ANS that acts in increase and decrease of heart rate

2. Intrinsic Conduction Systems / Nodal System

Built into the heart tissue and sets its basic rhythm.Composed of special tissue found nowhere else in the body.Causes heart muscle depolarization in only one direction – from

atria to ventricles.Allows the heart to beat as a coordinated unit.

75 beats / minute – contraction rate enforced by the Nodal System

Parts of the Intrinsic Conduction System

1. Sinoatrial (SA) Node / pacemaker – crescent shaped node of tissue in right atrium

A tiny cell mass with the highest rate of depolarization in the whole system.

Starts each heartbeat and sets pace for the whole heart.2. Atriaventicular (AV) Node – located at the

junction of the atria and ventricles3. Atrioventicular (AV) bundle (bundle of his)4. Right and left Bundle Branches – located in the

interventicular septum5. Purkinje Fibers – spread within the muscle of the

ventricle wall

The Intrinsic Conduction System of the Heart

SA node → atria → AV node → atria contract → AV bundle →

bundle branches → Purkinje fibers → “wringing” contraction of ventricles (from apex to atria)

→ blood is ejected superiorly into large arteries

Capillaries

-are the smallest of a body's blood vessels and are parts of the microcirculation.

-They are only 1 cell thick. These microvessels,

-measuring 5-10 μm in diameter, connect arterioles and venules,

-and enable the exchange of water, oxygen, carbon dioxide, and many other nutrient and waste chemical substances between blood and surrounding tissues.

Veins

-serve to return blood from organs to the heart

-Veins are also called "capacitance vessels" because most of the blood volume (60%) is contained within veins

- In systemic circulation oxygenated blood is pumped by the left ventricle through the arteries to the muscles and organs of the body, where its nutrients and gases are exchanged at capillaries, the blood then enter veinules, then veins filled with cellular waste and carbon dioxide.

- The de-oxygenated blood is taken by veins to the right atrium of the heart, which transfers the blood to the right ventricle, where it is then pumped through the pulmonary arteries to the lungs.

- In pulmonary circulation the pulmonary veins return oxygenated blood from the lungs to the left atrium, which empties into the left ventricle, completing the cycle of blood circulation.

Arteries

- are blood vessels that carry blood away from the heart.

-This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries.

-The circulatory system is extremely important for sustaining life.

-Its proper functioning is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, maintenance of optimum pH, and the mobility of the elements, proteins and cells of the immune system.