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/