High Blood Pressure

High blood pressure or hypertension is a serious condition that can lead to coronary heart disease, heart failure, stroke, kidney failure, and other health problems. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. If this pressure rises and stays high over time, it can damage the body in many ways.

Blood pressure measurement is inexpensive and easily performed. Blood pressure is measured in two phases that correspond to the natural contractions of the heart. When the heart contracts (e.g., systole), the pressure of blood against arterial walls is known as systolic pressure. When it relaxes (diastole), the pressure of blood against arterial walls is known as diastolic pressure.

    

• 120/80 mm/Hg or lower is normal blood pressure
• 140/90 mm/Hg or higher is high blood pressure
• Between 120 and 139 for the top number, or between 80 and 89 for the bottom number is prehypertension

The symptoms ofhigh blood pressure may include chest pain, shortness of breath, fatigue and ringing or buzzing in ears. Life style changes are effective in managing hypertension like limit alcohol intake, exercise regularly, reduce intake of sodium and maintain recommended dietary intake of potassium, calcium and magnesium.

Video of High Blood Pressure

Source: http://www.nlm.nih.gov/medlineplus/highbloodpressure.html

Basic Structure of a Blood Vessel

Three tunics of blood vessel

The three structural layers of a generalized blood vessel from innermost to outermost are the tunica intima, tunica media and tunica adventitia. Modification of this basic design account for the five types of blood vessels and the structural and functional differences among the various vessel types. The tunica intima forms the inner lining of blood vessel and direct contact with the blood as it flows through the lumen of the vessel. Its innermost layer is endothelium which continuous with endocardial lining of the heart. The internal elastic lamina is the outermost part of tunica intima and facilitates diffusion of materials through the tunica intima to thicker tunica media. Besides that, tunica media is a muscular and connective tissue layer that displays the greatest variation among vessel types. The primary role of smooth muscle in tunica media is to regulate the diameter of lumen. Furthermore, tunica adventitia consists of elastic and collagen fibers. The tunica adventitia helps anchor the vessels to surrounding tissues. The small vessels that supply blood to tissues of the vessel are called vasa vasorum.  

Tunica Interna (Intima)

The tunica interna (intima) forms the inner lining of a blood vessel and is in direct contact with the blood as it flows through the lumen, or interior opening, of the vessel. Although this layer has multiple parts, these tissues components contribute minimally to the thickness of the vessel  wall. Its innermost layer is a simple squamous epithelium, called endothelium, which is continuous with the endocardial cells were regarded as little more than a passive barrier between the blood and the remainder of the vessel wall. it is now known that endothelial cells are active participants in a variety of vessel-related activities, including physically influencing blood flow, secreting locally acting chemical mediators that influence the contractile state of the vessel;s overlying smooth muscle, and  assisting with capillary permeability.

The second components of the tunica interna is a basement membrane deep to the endothelium. It provides a physical support base for the the epithelial layer. Its framework of collagen fibers affords the basal lamina significant tensile strength yet its properties also provide resilience fro stretching and recoil. The basal lamina anchors the endothelium to the underlying connective tissues while also regulating molecular movement. it appears to play an important role in guiding cell movements during tissues repair of blood vessel wall. The outermost part of the tunica interna, which forms the boundary between the tunica interna and tunica media,  is the internal elastic lamina. The internal elastic lamina is a thin sheet of elastic fibers with a variable number of window-like openings that give it the look of Swiss cheese. These openings facilitate diffusion of materials through the tunica interna to the thicker tunica media.

Tunica Media

The tunica media is a muscular and connective tissues layer that displays the greatest variation among the different vessel types. In most vessels, it is a relatively thick layer comprised mainly of smooth muscle cells and substantial amounts of elastic fibers. The primary role of the smooth muscle cells, which extend circularly around the lumen like a ring encirles your finger, is to regulate the diameter of the luman, As you will learn in more detail shortly, the rate of blood flow through different parts of the body is regulated by the vessels. Furthermore, the extents of smooth muscle contraction in particular vessel types is crucial in the regulation of blood pressure.

In addition to regulating blood flow and blood pressure, smooth muscle contract when vessels are damaged to help limit loss of blood through the injured vessel and smooth muscle cells help produce the elastic fibers within the tunica media that allow the vessels to stretch and recoil under the applied pressure of the blood.

The tunica media is the most variable of the tunics. 

Tunica Adventitia

The outer covering of a blood vessel, the tunica adventitia, consists of elastic and collagen fibers. Separating the tunica adventitia from the tunica media is a network of elastic fibers, the external adventitia contains numerous nerves and , especially in larger vessels, tiny blood vessels that supply the tissues of the vessel wall. These small vessels that supply blood to the tissues of the vessel is called vasa vasorum, or vessels to the vessels. They care easily seen on large vessels such as the aorta. In addition to the important role of supplying the vessel wall with nerves and self-vessels, the tunica adventitia helps anchor the vessels to surrounding tissues.

Source: http://www.cayuga-cc.edu/people/web_pages/greer/biol204/vessels1/vessels1.html

Blood Vessels

Comparative structure of blood vessels

There are five main types of blood vessels which are arteries, arterioles, capillaries, venules and veins. Arteries carry blood away from the heart to other part of body. Large and elastic arteries leave the heart and divide into small arteries called arterioles. When arterioles enter a tissue, they branch into numerous tiny vessels called capillaries. Capillaries have a thin cell wall and allow the substances exchange between the blood and body tissues. Group of capillaries within a tissue reunite to form small vein called venules. Venules in turn merge to form progressively larger blood vessels called veins. Veins are the blood vessels that convey blood from tissue back to the heart.

Arteries

Arteries were found empty at death, in ancient times they were thought to contain only air. The wall of an artery has the three layers of a typical blood vessel, but has a thick muscular-to-elastic tunica media. Due to their plentiful elastic fibers, arteries normally have hit compliance, which means that their walls stretch easilt or expand without tearing in response to a small increase in pressure

Arterioles 

Arterioles have a thin tunica interna with a thin, fenestrated internal elastic lamina that disappears at the terminal end. The tunica media consists of one to two layers of smooth muscle cells having a circular orientation in the vessel wall. The terminal end of the arteriole, the region called the metarteriole, tapers toward the capillary junction. At the metarteriole-capillary junction, the distal-most muscle cell forms the precapillary sphincter which monitors the blood flow into the capillary, the other muscle cells in the arteriole regulate the resistance to blood flow.

Capillaries

Capillaries , the smallest of blood vessels, that connect the arterial outflow to the venous return. Capillaries form an extensive network, approximately 20 billion in number, of short, branched, interconnecting vessels that course among the individual cells of the body. This network forms an enormous surface area to make contact with body's cells. The flow of blood from a matarteriole through capillaries and int o a postcapillary venule is called the microcirculation of the body. The primary function of capillaries is the exchange of substances between the blood and interstitial fluid. Because if this, these thin-walled vessels are referred to as exchange vessels.

Venules

Unlike their thick-walled arterial counteparts, venules and veins hava thin walls that do not readily maintain their shape. Venules drain the capillary blood and begin the return flow of blood back toward the heart.

Veins

While veins do show structural changes as they increase in size from small to medium to large, the structural changes are not as distinct as they are in arteries. Veins , in general, have very thin walls relative to their total diameter. They range in size from 0.5 mm in diameter for small veins to 3 cm in the large caval veins entering the heart. 

Source: http://www.youtube.com/watch?v=CjNKbL_-cwA

Sickle-Cell Disease

Video of Sickle-Cell Disease

Diagram of normal and sickle red blood cell

Sickle-cell disease (SCD) contains Hb-S, an abnormal kind of hemoglobin. When Hb-S gives up oxygen to the interstitial fluid, it forms long and rod-like structures that bend the erythrocyte into a sickle shape. This abnormality can result in painful episodes, serious infections, chronic anemia, and damage to body organs. The sickled cells can rupture easily. Even though erythropoiesis is stimulated by the loss of the cells, it cannot keep pace with hemolysis. Sickle-cell disease is inherited. People with two sickle-cell genes have severe anemia. The gene responsible for the tendency of the RBCs to sickle also alters the permeability of the plasma membranes of sickled cells, causing potassium ions to leak out. Low levels of potassium kill the malaria parasites that may infect sickled cells. Thus, a person with one normal gene and one sickle-cell gene has higher-than-average resistance to malaria. Sickle-cell disease is inherited. People with two sickle-cell genes have severe anemia; those with only one defective gene have minor problems.
Treatment of sickle-cell disease consists of administration of analgesics to relieve pain, fluid therapy to maintain hydration, oxygen to reduce the possibility of oxygen debt and blood transfusions. People who suffer from SCD have normal fetal predominates bin, a slightly different form of hemoglobin that predominates at birth and is present in small amounts thereafter. In some patients with sickle-cell disease, a drug called hydroxyurea promotes transcription of the normal Hb-F gene, elevates the level of Hb-F, and reduces the chance that the RBCs will sickle. Unfortunately, this drug also has toxic effects on the bone marrow. Thus, its safety for long term use is questionable. 

 Source: http://www.youtube.com/watch?v=9UpwV1tdxcs

Blood Cell Disorders: Anemia

Diagram of normal and anemic amount red blood cells

Anemia is a condition in which the oxygen-carrying capacity of blood is reduced.  All of the many types of anemia are characterized by reduced numbers of RBCs. The person feels fatigued and is intolerant of cold, both of which are related to lack of oxygen needed for ATP and heat production. Besides that, the skin of the person with anemia will appears pale due to the low content of red colored hemoglobin circulating in skin blood vessels. There are many types of anemia such as iron-deficiency anemia, megaloblastic anemia, pernicious anemia, hemorrhagic anemia, hemolytic anemia, thalassemia and aplastic anemia. In some cases of sickle cell anemia, thalassemia, and aplastic anemia, bone marrow transplantation may be used. In this procedure, bone marrow cells taken from a donor are injected into the child's vein. They then travel through the bloodstream to the bone marrow and begin producing new blood cells. Among the most important causes and types of  anemia are the following: 

• Inadequate absorption of iron, excessive loss of iron, increased iron requirement, or insufficient intake of iron causes iron-deficiency anemia, the most common type of anemia. Women are at greater risk for iron-deficiency anemia due to menstrual blood losses and increased iron demands of the growing fetus during pregnancy. Gastrointestinal losses, such as those that occur with malignancy or ulceration, also contribute to this type of anemia. 

• Inadequate intake of vitamin B or folic aced causes megaloblastic anemia  in which red bone marrow produces large, abnormal red blood cells. It may also be caused by drugs that alter gastric secretion or are used to treat cancer. 

• Insufficient hemopoiesis resulting from an inability of the stomach to produce intrinsic factor, which is needed from absorption of vitamin B in the small intestine,  causes pernicious anemia.

• Excessive loss of RBCs through bleeding resulting from large wounds, stomach ulcers, or especially heavy menstruation leads to hemorrhagic anemia. 

• RBC plasma membranes rupture prematurely in hemolytic anemia. The released hemoglobin pours into the plasma and may damage filtering units int he kidney. The condition may result from inherited defects such as abnormal red blood cell enzymes, or from outside agents such as parasites, toxins, or antibodies from incompatible transfused blood.

• Deficient synthesis of hemoglobin occurs in thalassemia.,a group of hereditary hemolytic anemia. The RBCs are small, pale, and short-lived. Thalassemia occurs in population from countries bordering the Mediterranean Sea.

• Destruction of red bone marrow results in aplastic anemia. It is caused by toxins, gamma radiation, and certain medications that inhibit enzymes needed for hemopoiesis. 

Symptoms of anemia 

Source: http://www.youtube.com/watch?v=_ZV5140OykE

Rh Blood Group

Many people also have a so called Rh factor on the red blood cell's surface. This is also an antigen and those who have it are called Rh⁺. Those who haven't are called Rh^-. A person with Rh^- blood does not have Rh antibodies naturally in the blood plasma. But a person with Rh^- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh⁺ blood, whose Rh antigens can trigger the production of Rh antibodies. A person with Rh⁺ blood can receive blood from a person with Rh^- blood without any problems.

                   Development of hemolytic disease of the newborn

The most common problem with Rh incompatibility, hemolytic disease of the newborn, may arise during pregnancy. Normally, no direct contact occurs between maternal and fetal blood while a women is pregnant. However, if a small quantity of Rh⁺ fetal blood leaks across the placenta into maternal bloodstream of an Rh^- mother. Upon exposure to Rh antigen, the mother will start to make anti-Rh antibodies. Usually, the first born baby is not affected. During a subsequent pregnancy the maternal antibodies cross the placenta into the fetal blood. If the second fetus is Rh⁺, the ensuing antigen-antibody reaction causes agglutination and hemolysis of fetal RBCs and result hemolytic disease of the newborn.

Source: http://www.umm.edu/pregnancy/000203.htm

Blood Groups and Blood Types

  Table of four blood group 

The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. 


The surfaces of erythrocytes contain a genetically determined lipids. These antigens, called agglutinogens, occur in characteristic combinations. Based on the presence or absence of various antigens, blood is categorized into different blood groups. Within a given blood group, there are at least 24 blood groups and more than 100 antigens that can be detected on the surface of red blood cells. Here we discuss two major blood groups. ABO and Rh. Other blood groups include the Lewis, Kell, Kidd, and Duffy systems. The incidence of ABO and Rh blood types varies among different population groups.


The antigens are located on the surface of the red blood cells and the antibodies are in the blood plasma. The ABO blood group is based on two antigens called A and B. People who are RBCs display only antigen A has type A blood. Those who have only antigen B are type B. Individuals who have both A and B antigens are type AB and those who have neither antigen A nor B are type O.  


Blood plasma usually contains antibodies called agglutinins. If your blood type is A, you have A antigens on your red blood cells and you have anti-B antibodies in your blood plasma. People with type AB blood do not have anti-A or anti-B antibodies in their blood plasma and they are called universal recipients and can receive blood from donors of all four blood types. On the other hand, people with type O blood have neither A or B antigens on their RBCs and called universal donors because they donate blood to all four ABO blood types. Type O persons can only receive type O blood.

Source: http://www.ncbi.nlm.nih.gov/books/NBK2267/

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