Cardiovascular System And Blood
I. Cardiovascular System
The Heart
Blood Vessels
Cardiovascular Pathways
Disorders
II. Blood
Function and Composition
Red Blood Cells
White Blood Cells
Platelets
Sickle Cell
Blood Types
Blood Pressure and Pulse
The Cardiovascular System and Blood
The cardiovascular system distributes blood throughout the entire body. The heart works as a pump distributing blood through a network of blood vessels with which the blood flows. The blood carries the substances to be exchanged at the cellular level and is important to cell functioning.The circulation of the blood refreshes the cells in all parts of the body in several ways. When blood enters the lungs, oxygen enters and CO2 leaves. As the blood enters the kidneys the wastes are filtered, and nutrients are picked up in the intestines. Amino acids are absorbed in the blood and proteins and fats are returned. The lymphatic system collects excess tissue fluid and sends it to the cardiovascular system. Both blood and lymph are tissue fluid
The Heart
The heart is a muscular organ that sits behind the sternum in the chest area. It is acorn shaped with the apex tilted slightly to the left. There are four chambers, divided to the right and left by the sternum. The are two upper chambers. The right atrium receives oxygen depleted blood from throughout the by the inferior and superior vena cava. And the opposite is true for the left atrium which receives oxygen rich blood from the lung by the pulmonary veins. Blood is pumped from the lower chambers called ventricles. Because of this they are thicker and more muscular. The right ventricle sends oxygen depleted blood to the lungs by the pulmonary arteries. And the left ventricle sends oxygen rich blood throughout the body through the aorta. It is known as a double pump because the left ventricle sends blood throughout the body and the right ventricle sends blood to the lungs. Myocardium is the cardiac muscle lining the heart walls.
To keep the flow of blood in the right direction and to prevent backflow the heart has four valves. Two atrioventricular (AV) valves are between the atria and ventricle. The valve on the right is called the tricuspid valve and the valve on the left is the bicuspid. They are both held up by stringlike supports that attach to the walls of the heart. The other two valves called semilunar valves prevent backflow as blood is leaving the heart. The pulmonary semilunar valve on the right and the aortic semilunar valve on the left.
Heart contraction moves blood throughout the body with it's pumping action. This contraction is known as the heartbeat. There are two beats that make up the cardiac cycle. The first contraction of both atria and the second contraction of both ventricles making the sound "lupdup". The contraction or working phase is called systolic and at relaxation it is called diastolic. Intercalated disks lets cells of the atria and ventricle contract by conduction. Pericardium is the thick covering around the heart having two layers with the inner layer secreting a fluid that allows the heart to move when it beats.
An internal conduction system of nodal tissue is located in two areas of the atrium. This cardiac muscle tissue has nervous and muscular functions. The heartbeat is initiated in the upper right atrium by the sinoatrial node contracting the atria then as the signal reaches the atrioventicular node at the base of the right atrium the ventricles contract.
Working together with other parts of the body, the medulla oblongata controls parasympathetic and sympathetic responses of the heartbeat. Hormones from the Adrenal medulla can stimulate the heart to beat faster.
Blood Vessels
There are three types of blood vessels, arteries, capillaries, and veins. Each serve a different purpose. Arteries distribute blood throughout the body, capillaries facilitate exchange of substances and veins collect blood from the body.
Arteries carry oxygen rich blood going away from the heart. Made up of three layers, the endothelium is the thin inner layer. Muscle tissue and a thin layer of elastic form the middle layer and connective tissue form the outer layer. Arteries are thicker and under more pressure. Arterioles are smaller arteries that branch into capillaries. When they constrict or dilate it effects blood pressure. By placing the middle and index fingers against the blood vessels of the radial or carotid artery a pulse reading can be taken that equals the heart rate. Other areas where the pulse can be felt are in the arteries close to the skin. Other than the carotid and the radial there are five others: the brachial on the upper arm, aortic arch by the heart, abdominal aorta by the stomach, femoral arteries on the thigh , and the popliteal arteries near the knees. The average heart rate is between 60 to 80 beats per minute for adults.
Capillaries are microscopic vessels found throughout the body covering about 6,300 sq. meters. Made up of a single thin layer of endethelial cells the thin layer allows diffusion of oxygen, carbon dioxide, nutrients and wastes. Blood capillaries re-circulate blood and lymph capillaries help rid waste. Where exchange takes place is in the capillary bed, a web of vessels between an arteriole and a venule. Exchange is caused by blood pressure and osmotic pressure. Water leaves the capillary ends by difference in pressure at the arterial end and in reverse water moves into capillary ends by difference in pressure at the venule end. Wastes and carbon dioxide are diffused into capillaries. However, red blood cells and plasma proteins are too large to exit capillaries. Capillaries are also found surrounding the alveoli in the lungs. The thin tissue of alveoli lets oxygen cross through to red blood cells where hemoglobin holds oxygen.
Veins collect blood to return to the heart and are similar in structure to arteries. Also made of the same three layer as arteries but having a thinner middle and outer layer. This makes them thinner. Veins have one-way valves that prevent backflow. There is less pressure in veins and so the flow of blood is assisted by three factors. Veins have one-way valves to regulate flow going to the heart. The skeletal muscle pump contracts the muscles causing blood to move and the respiratory pump expands the thoracic cavity in an action that moves blood as well. Between a vein and a capillary there is a venule.
Cardiovascular Pathways
There are two pathways for the circulation of blood. Blood reaches the lungs by the path of the pulmonary circuit. The circuit loops from the body to the right atrium, pulmonary trunk, right and left pulmonary arteries and then to the lungs. From the arterioles blood is delivered to the capillaries where carbon dioxide is released and oxygen is absorbed. Then the pulmonary venules lead to the four veins and to the left atrium. Pulmonary arteries carry oxygen poor blood and pulmonary veins carry oxygen rich blood. Blood reaches body tissues by the systemic circuit. The left ventricle sends the blood to the aorta then throughout the body. It returns to the heart from the inferior and superior vena cava into the right atrium. The superior vena cava returns blood from the head, chest , and arms. And the inferior vena cava returns blood from the lower parts of the body. Coronary arteries supply blood to the heart and branch off the aorta. The hepatic portal system transports blood from the digestive tract to the liver.The hepatic portal vein carries oxygen depleted blood containing glucose and amino acids. The liver stores glucose and purifies the blood. Blood then leaves the liver by the hepatic vein.
Cardiovascular Disorders
The leading cause of death in the western world and on the rise in other countries. Cardiovascular diseases can cause heart attack, stroke or kidney failure. Hypertension is a condition of abnormally high blood pressure. It can be caused by stress diet and a number of other reasons. Damage can occur to the vascular system or heart and prolonged hypertension can create other complications and lead to stroke or heart attack. Normal blood pressure is considered to be 120/80 but in recent years it has been increased to 130/80. Atherosclerosis is caused by plaque lining the walls of the arteries and high cholesterol levels. The risks are blockages in the arteries that can lead to heart attack or stroke. Pain radiating in the left arm is a symptom of possible heart problems.
BLOOD
A liquid medium for transport, defense and regulating. It is composed of tissue cells
Function and Composition
Blood carries oxygen and nutrients to the tissues and carries away waste. It transports hormones to tissues for cell metabolism and contains blood cells that defend against pathogens. Some secrete antibodies that help to destroy pathogens and unwanted microbes. Blood also helps to regulate temperature and water-salt balance. Blood is a tissue fluid made up of cells, consisting of water and proteins. The liquid part is called plasma. Plasma proteins made by the liver help to maintain pH. Major plasma proteins include albumins which carry organic molecules to form osmotic pressure, fibrinogens form blood clots and three types of globulins. Alpha and beta transport hormones, cholesterol and iron, and gamma is made in white blood cells.
Red Blood Cells
Red blood cells (RBC) do not have a nucleus and lack most organelles. Through mitosis they replicate DNA rapidly and it's production is effected by oxygen. They contain plenty of hemoglobin which gives the cells it's red color pigment. They are produced in the bone marrow. The unique concave shape allows for more surface area for diffusion to occur and is used to hold oxygen. How much oxygen? Each cell can carry over a billion copies of oxygen. The cells destroy very rapidly and replicate very quickly in the liver and spleen. Anemia occurs if someone has an insufficient number of red blood cells or not enough hemoglobin. Sickle cell disease is is a blood disorder caused by the irregular shape of the cell which ruptures as it passes through the capillaries thus increasing red cell destruction. It is a chronic and lifelong disease that can shorten life span. And is an inherited condition.
White blood cells
Serving the function of immunity white blood cells ( leukocytes) fight pathogens and are larger than red blood cells. Produced in the bone marrow they can double within hours. They exist in tissue fluid and lymph because they are able to squeeze out of capillary walls. Some white blood cells are able to surround and destroy pathogens in a process called phagocytosis. Others secrete antibodies and mark unwanted invaders for removal. A protein called colony stimulating factor regulates the various types of white blood cells. There are two types of white blood cells. Granular leucocytes and Agranular leucocytes which do not have granules. Granular leucocytes consist of neutrophils, the most abundant, they are phagocytic and act as first response bacterial invasion. Basophils release a substance to trigger other cells and eosinophils multiply in response to allergy or infection. There are two types of agranular leucocytes, lymphocytes and monocytes. The second most abundant white cells lymphocytes consist of T cells and B cells. B cells make antibodies and T cells destroy pathogens. Monocytes are the largest and can become macrophages. They become dendritic cells in the skin and phagotize old cells, debris and pathogens.
Platelets
The process of blood clotting is assisted by platelets (thrombocytes). When a vessel is punctured or damaged clotting takes place to stop the bleeding. The platelets coagulate to form a clot. Platelets are also produced in the red bone marrow. Thrombocytopenia happens when platelet count is low resulting in nosebleeds, bruising, bleeding in the mouth, intestines and brain. Hemophilia is an inherited clotting disorder. Someone who has this condition bleeds easily.
Sickle Cell
This is a hereditary blood disorder that causes abnormal production of hemoglobin. The red blood cells become deformed, (shape of a sickle) as a result it cannot carry enough oxygen and easily break apart or create a condition of low or insufficient hemoglobin. Some will stick together causing blockages. The result of reduced oxygen will lead to tiredness, poor tissue development and malfunction of major organs leading to death. The cell mutation is a error in the DNA code that lets the body know how it should form hemoglobin. When sickle cell disease was recognized, clinicians saw that it ran more in families of African descent.The sickle cell gene is prevalent in Africa in areas with malaria. Researcher found that this trait benefited those in areas with malaria. It requires the individual to inherit both genes in order to acquire this disease.
Blood Types
Determining blood type is important in transfusions. Two distinctions the ABO group and Rh group make up blood type. There are four combinations to the ABO group. Type A, B, AB, and O. Type A carries the A antigens and anti-B antibodies, type B the B antigens and anti- A antibodies, type AB the A and B antigens, and type-O the anti- A &B antigens. The second distinction Rh blood group determines the Rh factor of antibodies.
Blood Pressure
Blood pressure moves blood in the arteries and is measured by a sphygmomanometer at the brachial artery. The greatest pressure is called systolic and the lowest pressure when the heart is at relaxation is called diastolic. Normal blood pressure is 120/80. Hypertension is the result of high blood pressure and hypotension is the result of low blood pressure.
References:
en.wikipedia.org/wiki/Heart
http://www.howstuffworks.com/heart.htm
http: // tutorials.com/09/0902/0902.asp
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