The Circulatory

System

Prepared by Mickelder Kercy, MD - Instructor

Anatomy of the Heart

Pericardium : The outer Layer

Myocardium : The middle layer/heart muscle

Endocardium : The innermost layer

Right Atrium : Right upper chamber

Left Atrium : Left upper chamber

Right Ventricle : Right lower chamber

Left Ventricle : Left lower chamber

Tricuspid Valve : Between the RA and the RV

Mitral Valve : Bicuspid valve located between the LA

and the LV

Pulmonary Semilunar Valve : Between the RV and the

Lungs

Aortic Semilunar Valve : Between the LV and the Aorta

Physiology of blood flow through the Heart

SVC : Drains blood from the head, upper extremities

and chest to the RA

IVC : Drains blood from the lower extremities and

pelvis and abdomen to the RA

PA : Brings blood from the RV to the Lungs

PV : Brings blood from the Lungs to the LA

Aorta : Largest artery bringing the blood from the LV

to the rest of the body

Coronary Arteries : Supply blood to the heart tissue

Coronary veins : Drain blood from the heart into the

coronary sinus which

drains into the right

atrium

Anatomy & Physiology of the Conduction System of the Heart

SA : Pacemaker in the upper wall of RA initiating the heartbeat

AV node : Under the endocardium of the RA sending impulses from the SA node to the Bundle of His

Bundle of His : AV bundle sending impulses from the AV node to the Purkinje fibers through the RBB and the LBB

RBB + LBB : In the septum

Purkinje Fibers : Within the walls of the ventricles causing the ventricles to contract

Cardiac cycle

During relaxation/diastole the chambers fill up with

blood

During contraction/systole the chambers forcefully

move the blood out

During diastole the RA receives blood from the SVC

+ the LA receives blood from the PV. At the same

time the Ventricles are in systole. The RV ejects the

blood into the PA and the LV ejects the blood into the

Aorta

Heart sounds

Closure of the A-V valves produces the 1st heart sound

Closure of the Semilunar valves produces the 2nd heart

sound

Anatomy of the Arteries

Elastic tubes that expand with pressure (during

contraction of the heart). Composed of the tunica

externa/adventitia, tunica media and the tunica intima

Arterioles - Capillaries - Venules

Arterioles : Tunica adventitia, media and intima

Capillaries : Endothelium

Venules : Tunica adventitia, media and intima

Veins

Thin-walled vessels with low pressure. Contain valves

preventing backflow of blood. Composed of tunica

externa/adventitia, tunica media and tunica intima

Venipuncture/phlebotomy : Incision of a vein to draw

blood for examination

Physiology of the blood vessels circulation

Arteries : Carry the blood away from the aorta

Arterioles : Smaller vessels carrying the blood away from the arteries to the capillaries

Capillaries : Smallest vessels where the nutrients and oxygen leave the blood and go into the cells. The waste products and carbon dioxide from the cells pass through the capillaries into the bloodstream

Venules : Larger than the capillaries but as small as the arterioles carrying the blood filled with waste products away. Also carry the blood filled with nutrients from the small intestine to the hepatic vein. Carry the blood filtered though the kidneys to the hepatic vein

Veins : Larger than the venules carrying the blood from the upper part of the body to the SVC and from the lower part of the body to the IVC

Obtaining a pulse

Radial Artery : Lateral wrist + proximal to the thumb

Apex of the heart : 5th intercostal space

Brachial Artery : Antecubital space of the elbow or

between the biceps and triceps muscle

Carotid artery : Lateral neck

Temporal Artery : Temple

Femoral Artery : Inguinal

Popliteal Artery : Posteromedial (knee)

Dorsalis Pedis Artery : Upper surface of the foot

Anterior Tibial Artery : Medial side of the ankle

Blood Pressure

Determined by the force exerted by the blood on the

walls of the arteries, the amount of blood pumped, the

size and the flexibility of the arteries

Measured in the arm (brachial artery) using the

sphygmomanometer

1st korotkoff sounds and last korotkoff sounds heard

through the stethoscope

N° BP : 120/80 mmHg

Pulmonary Circulation

Heart

Pulmonary Artery

Pulmonary arterioles

Pulmonary capillaries

Pulmonary venules

Pulmonary vein

Systemic Circulation Heart

Aorta

Arteries

Arterioles

Capillaries

Venules

veins

SVC + IVC

Blood

Composed of cells : -Erythrocytes/RBC

(45%) Male (4.3-5.9 million/mm³)

Female (3.5-5.5 million/mm³)

-Leukocytes/WBC

(4500-11,000/mm³)

-Thrombocytes/Platelets/clotting

cells (150,000-400,000/mm³)

and of plasma : -Fluid Portion

(55%)

Blood Cells Formation

Erythrocyte : Biconcave. No nuclei. Made up of

Hemoglobin (protein & iron). Hb Carries oxygen

from the lungs to the cells and carbon dioxide from

the cells to the lungs. Produced in the bone marrow

Leucocyte : Larger. Contains a nucleus. Has to be

stained to be seen. Fight infection. Categorized as

granulocyte or agranulocyte.

Granulocytes : Basophils, Eosinophils and

Neutrophils have granules in their cytoplasm

Basophils Eosinophils Neutrophils

Agranulocytes : Monocytes and Lymphocytes T and

B do not have granules in their cytoplasm

Monocytes Lymphocytes

Thrombocytes : Smaller than the RBC and WBC.

Control the loss of blood by congregating to form a

clot (coagulation) at the site of injury

Functions of the blood

Transportation : -Oxygen from the lungs to the cells

-Carbon dioxide from the cells to the lungs

-Nutrients from the digestive tract to the

cells

-Hormones from the endocrine glands

to the cells of each organ

-Waste materials from the cells to the liver

to be excreted in the feces through the bile and to the

kidney to be eliminated in the urine

Regulation : -Body Temperature

(vasodilation vs vasoconstriction)

-Water and salt balance

-pH balance

-Blood loss with coagulation

Defense : -Neutrophils and Monocytes phagocyte

(destroy the germ)

-Lymphocytes B secrete antibodies that

attach to the germ before it is phagocytized

-Lymphocytes T attack directly the germ

Blood Types

Type A : Type A antigen on the RBC and anti-B

antibody in the plasma

Type B : Type B antigen on the RBC and anti-A

antibody in the plasma

Type AB : Both A and B antigens on the RBC and no

anti-A or anti-B antibodies in the plasma

Type O : No A or B antigens on the RBC but anti-A

and anti-B antibody in the plasma

The Rhesus Factor/Rh+ : Antigen on the RBC.

Pregnant woman without the antigen(Rh-) whose

fetus’ RBC has the antigen(Rh+) will develop

antibodies against the antigen. During the next

pregnancy the antibodies will attack the RBC of the

fetus and the fetus will become anemic and may die

In general, Rh negative blood is given to Rh-negative

patients, and Rh positive blood or Rh negative blood

may be given to Rh positive patients.

The universal red cell donor has Type O negative

blood type

The universal plasma donor has Type AB positive

blood type.

The lymphatic System

Lymphatic vessels : Transport excess fluids away

from the interstitial space (in-between the cells) into

the bloodstream. Contain valves that prevent

backflow which leads to edema

Lymphatic nodes : Filter out and trap bacteria,

viruses, cancer cells, destroyed pathogens and

unwanted substances

Common disorders associated with the circulatory System

Iron-deficiency Anemia : Low iron level leading to

low hemoglobin production

Pernicious Anemia (Vit-deficiency Anemia) : Lack of

secretion of intrinsic factor from the stomach causing

vitamin B12 not to be absorbed. Leads to macrocytic

anemia and glossitis (swollen red tongue), neuropathy

etc..

Hemolytic Anemia : Premature destruction of RBCs

by antibodies produced by the immune system

Sickle cell Anemia : Hemoglobin S disease with a

sickle-shaped RBC in people of African origins

Aplastic Anemia : Failure of the bone marrow to

produce the blood cells. The bone marrow is replaced

with fat cells

Aneurysm : Abnormal widening of a portion of an

artery because of weakness in the vessel wall

Tachycardia : Fast heartbeat >100bpm

Bradycardia : Slow heartbeat <60bpm

Arteriosclerosis : Hardening of the arteries. Caused

by HTA, Atherosclerosis, Calcium deposits etc…

Atherosclerosis : Buildup of plaque(fatty acids) in the

wall of the artery. May lead to the narrowing of the

lumen and hardening (arteriosclerosis) of the vessel.

Leading cause of coronary artery disease(CAD)

Coronary artery disease : Narrowing of the coronary

arteries that supply blood to the heart.

Cerebrovascular accident : Stroke resulting from a

complete interruption of blood flow to the brain by a clot

(Thrombotic/Embolic Stroke) or a ruptured blood vessel

(Hemorrhagic Stroke)

Cardiac Tamponade : Congestion of the heart muscle

and restriction of heart movement caused by blood or

fluid trapped in the pericardial sac

Cardiogenic Shock : Collapse of the cardiovascular

system resulting from vasodilation and fluid shifting

away from the heart

Cardiomyopathy : Disease of the myocardium

Pericarditis : Inflammation of the pericardium

Myocarditis : Inflammation of the myocardium

Endocarditis : Inflammation of the endocardium

Congestive Heart Failure : Heart is unable to pump

sufficient blood to the rest of the body

Cor Pulmonale : Lung disease blocking the flow of

blood from the right ventricle to the lungs. Results in

an enlargement of the RV

Myocardial Infarction : Infarction/death of heart

tissue because of severe reduction or absence of

supply of blood to an area of the myocardium

Hemophilia : Hereditary deficiency of clotting factors

most frequently in male

Pre-Hypertension : BP from 120/80 – 139/89

Hypertension : BP>140/90

Hypotension : BP <90/60

Leukemia : Abnormal growth/Cancer of the

leukocytes

Thrombophlebitis : Blood clot causing inflammation

in the vein

Petechiae : Small red/purple eruptions on the body

caused by broken capillaries

Transfusion Reaction : When the blood type

transfused to a patient is incompatible with the

patient’s blood type causing an agglutination of the

patient’s RBC

Mitral Stenosis : Mitral valve disease/calcification

causing the valve to narrow not able to open up

sufficiently when blood enters the RV

Mitral Valve Prolapse : Mitral valve is above its

normal location between the atrium and the ventricle

causing the leaflets to go all the way into the atrium

rather than get close to each other horizontally at the

end of the ventricular contraction

Varicose veins : Enlarged and tortuous veins caused

by malfunctioning valves

The End