Blood

Components of Blood

Blood is a liquid connective tissue that consists of cells surrounded by extracellular matrix. Blood is denser and more viscous than water. The temperature of blood is about 38 ˚C. Its pH is slightly alkaline, ranging from 7.35-7.45. Blood constitutes about 8% of the total body weight. The blood volume is 5 to 6 liters in an average-sizes adult male and 4 to 5 liters in an average-sized adult female. The difference in volume is due to differences in body sizes. Blood is about 45% formed elements and 55% blood plasma. Blood is a mixture of two components which are blood plasma and formed elements. 


Blood plasma is a liquid extracellular matrix that contains dissolved substances. Plasma is about 91.5% water, 7% proteins and 1.5% solutes other than proteins. The plasma protein, are albumins, globulins and fibrinogen which are synthesized mainly by the liver. The solutes dissolved in plasma include electrolytes, nutrients, gases, regulatory substances such as enzymes and hormones, vitamins and waste products. The formed elements of blood contain red blood cells (RBCs), white blood cells (WBCs) and platelets. 


Normally, more than 99% of the formed elements are cells named  of their red color. Colorless white blood cells and platelets occupy less than 1% of the formed elements. Because they are less dense than red blood cell but more dense than blood plasma, they form a very thin buffy coat layer. RBCs carry oxygen from the lungs, the WBCs help to fight infection and platelets are parts of cells that the body uses for clotting. All blood cells are produced in the bone marrow.

Source: www.biologycorner.com/anatomy/bl...ood.htm

Pericarditis

 Diagram of Pericarditis

Pericarditis is inflammation of any of the layers of the pericardium.. The most common type is acute pericarditis and caused by viral infection, after a heart attack, trauma and radiation. As a result of irritation to the pericardium, there is a chest pain this pain is different from angina and that may extend to the left shoulder and down to left arm. It is made worse when lying down, coughing or swallowing and is relieved by sitting forward. Moreover, the symptoms of pericarditis included low-grade fever, increase in heart-rate and pericardial friction rub. Acute pericarditis usually lasts for about one week and is treated with drugs that reduce inflammation and pain such as ibuprofen.


Chronic pericarditis begins gradually and is long-lasting. In one form of this condition, there is a buildup of pericardial fluid. If a great deal of fluids accumulates, there is a life-threatening condition because the fluid compresses the heart, a condition called cardiac tamponade. As a result of the compression, ventricular filling is decreased, cardiac output is reduced, venous return to the heart is diminished, blood pressure falls and breathing is difficult. Most causes of chronic pericarditis involving cardiac tamponade are unknown and sometimes caused by cancer and tuberculosis. Treatment consists by condition of draining the excess fluid through a needle passed into the pericardial cavity.

Source: http://www.metrohealth.org/body.cfm?id=1487

Electrocardiogram



Diagram of electrocardiogram



P wave- represents atrial depolarization which spreads from the SA node through contractile fibers in both atria.

QRS complex- represents rapid ventricular depolarization, as the action potential spreads through ventricular contractile fibers.

T wave- indicates ventricular repolarization as the ventricles are starting to relax.

Video of Normal electrocardiogram

An electrocardiogram is a composite record of action potentials produced by all the heart muscle fibers during each heartbeat. The instrument used to record the changes is an electrocardiograph.In reading an ECG, the size of the waves can provide clues to abnormalities. Larger P waves indicate enlargement of an atrium; an enlarged Q waves indicates a myocardial infarction; an enlarged R wave indicates enlarged ventricles. The T waves is elevated in hyperkalemia.


Analysis of an ECG also involve measuring the time spans between waves which are called intervals. The P-Q interval is the time from the beginning of the P wave to the beginning of the QRS complex. It represents the conduction time from the beginnning of atrial excitation to the beginning of ventricular excitation. Put another way, the P-Q interval is the time required for the action potential to travel through the atria, atrioventricular node and the remaining fibers of the conduction system. As the action potential is forced to detour around scar tissue caused by disorders like coronary artery disease and rheumatic fever. the P-Q interval lengthens.


The S-T segment which begin at the end of the S wave and end at the beginning of the T wave, represent the time when the ventricular contractile fibers are depolarized during the plateau phase of the action potential. The S-T segment is elevated in acute myocardial infarction and depressed when the heart muscle receive insufficient oxygen.


The Q-T interval extends from the start of the QRS complex to the end of  the T wave. I t is the time from the beginning of ventricular depolarization to the end of ventricular repolarization. The Q-T interval may be lengthened by myocardial damage and myocardial ischemia.

Source: http://www.youtube.com/watch?v=nK0_28q6WoM&feature=related

Chambers of the heart

 

Human Circulatory System

The heart has four chambers. The upper or superior chambers are called the left and right atria, and the lower or inferior chambers are called the left and right ventricles. On the anterior surface of atrium is wrinkled pouchlike structure called an auricle, so named because of its resemblance to a dog’s ear and its functions is to increase the capacity of an atrium. A wall of muscle called the septum separates the left and right atria and the left and right ventricles. The surface of the heart is also a series of grooves, called sulci which contain coronary blood vessels and variable amount of fat. The two atria are thin-walled chambers that receive blood from the veins. The right atrium is about 2-3mm in average thickness and receive deoxygenated blood from three veins are superior vena cave, inferior vena cava and coronary sinus. Whereas, left atrium is about same thickness as the right atrium and it receive oxygenated blood from the pulmonary veins. The two ventricles are thick-walled chambers that forcefully pump blood out of the heart. The right ventricle is about 4-5mm in average thickness. Inside the right ventricle contain a series of ridges formed by raised bundles of cardiac muscle fiber called trabeculae carneae. Some of the trabeculae carneae convey part of the conduction system of the heart. Blood passes from the right ventricle through the pulmonary valve into a large artery called pulmonary trunk. The left ventricle is the thickest chamber of the heart, averaging 10-15 mm and forms the apex of the heart. Blood passes from the left ventricle through the aortic valve into ascending aorta.

In postnatal circulation, the heart pumps blood into two closed circuits with each beat, systemic circulation and pulmonary circulation. The two circuits are arranged in series. The output of one becomes the input of the other, as would happen if you attached two garden hoses. The left side of the heart is the pump for systemic circulation, it receives bright red, oxygen-rich blood from the lungs. The left ventricle ejects blood into the aorta. From the aorta, the blood divides into separates streams, entering progressively smaller systemic arteries that carry it to all organs throughout the body except for the air sacs of the lungs, which are supplied by pulmonary circulation. In systemic tissues, arteries give rise to smaller diameter arterioles, which finally lead into extensive beds of systemic capillaries. Exchange of nutrients and gases occurs across the thin capillary walls. Blood unloads oxygen and picks up carbon dioxide. In most cases, blood flows through only one capillary and then enters a systemic venule. Venules carry deoxygenated blood away from tissues and merge to form larger systemic veins. Ultimately the blood flows back to the right atrium.


The right side of the heart is the pump for pulmonary circulation. It receives all the dark red, deoxygenated blood returning from systemic circulation. Blood ejected from the right ventricle flows into the pulmonary truck, which branches into pulmonary arteries that carry blood to the right and left lungs. In pulmonary capillaries, blood unloads carbon dioxide, which is exhaled, and picks up inhaled oxygen. The freshly oxygenated blood then flows into pulmonary monary veins and returns to the left atrium.

In conclusion, differences in thickness of the heart chamber walls are due to variations in the amount of myocardium present, which reflects the amount of force each chamber is required to generate.

Source: http://www.youtube.com/watch?v=D3ZDJgFDdk0

Location of the heart

Anatomy of the heart

The heart is about 12cm long, 9 cm wide at its broadest point and 6cm thick which has an average mass of 250g in adult female and 300g in adult male. The heart rests on the diaphragm, near the midline of the thoracic cavity and lies in the mediastinum. Mediastinum is an anatomical region from sternum to the vertebral column. The heart is also located between the lungs in the middle of the chest, behind and slightly to the left of the sternum and in front of the spine. Because the heart is not central, but lies to the left of the center line, the heart beat is best felt on the left side of the chest. To make room for it, the left lung is rather smaller than the left.

The pointed apex is formed by the tip of the left ventricle and rests on the diaphragm. It is directed anteriorly, inferiorly, and to the left. The base of the heart is its posterior surface. It is formed by the atria of the heart, mostly the left atrium. 

In addition to the apex and base, the heart has several distinct surfaces and borders. The anterior surface is deep to the sternum and ribs. The inferior surface is the part of the heart between the apex and right border and rest mostly on the diaphragm. The right border faces the right lung and extends from the inferior surface to the base. The left border, also called the pulmonary border, faces the left lung and extends from the base to the apex.

Pericardium of the Heart

The membrane that surrounds and protects the heart is the pericardium. It confines the heart to its position in the mediastinum, while allowing sufficient freedom of movement for vigorous and rapid contraction. The pericardium consists of two part, the fibrous pericardium and the serous pericardium. The superficial fibrous pericardium is composed of tough, inelastic, dense irregular connective tissue. It resembles a bag that rests on the attaches of the diaphragm, its open end is fused to the connective tissues of the blood vessels entering and leaving the heart. The fibrous pericardium prevents overstretching of the heart, provides protection, and anchors the heart in the mediastinum. 

The deeper serous pericardium is a thinner, more, delicate membrane that forms a double layer around the heart. The outer parietal layer of the serous pericardium is fused to the fibrous pericardium. The inner visceral layer of the serous pericardium, also called the epicardium, is one of the layers of the heart wall and adheres tightly to the surface of the heart. Between the parietal and visceral layers of the serous pericardium is a thin film of lubricating serous pericardial fluid, reduces friction between the layers of the serous pericardium as the heart moves. The space that contains the few milliliters of the pericardial fluid is called the pericardial cavity.

Source: http://www.cvtsa.com/si55550728HeartAnatomyAnterior_frontview/M-441-202.html

The Cardiovascular System

The Cardiovascular System is one of the most important systems in human body. It is made up of blood, blood vessels and the heart. In normal human body, the heart beats is about 100,000 times every day, which adds up to 35 million beats in a year and about 2.5 billion times in an average lifetime. Even when human are sleeping, their heart pumps 30 times its own weight (5L or 5.3qt) each minute, which amounts to more than 14,000 liters of blood in a day and 10 million liters in a year.

Our bodies actually have two circulatory systems: The pulmonary circulation is a short loop from the heart to the lungs and back again, and the systemic circulation (the system we usually think of as our circulatory system) sends blood from the heart to all the other parts of our bodies and back again.

  
Source: http://www.drstandley.com/bodysystems_cardiovascular.shtml