The lymphatic system

The lymphatic system consists of a fluid (lymph), vessels that transport the lymph, and organs that contain lymphoid tissue. It is often called the secondary circulatory system. The lymphatic system has three primary functions:
• The removal of excess intresticial fluids from body tissues.
• The absorption of fats from the small intestine and transport of those fats to the cardiovascular system.
• The third and probably most well known function of the lymphatic system is defense against invading microorganisms and disease. Lymph nodes and other lymphatic organs filter the lymph to remove microorganisms and other foreign particles.
Lymph
Lymph originates as blood plasma that leaks from the capillaries of the cardiovascular system. This blood plasma fills the space between individual
cells of tissue where it becomes part of the interstitial fluid. Most of the interstitial fluid is returned to the capillaries. The excess interstitial fluid is collected by the lymphatic system into lymph capillaries, and is processed by lymph nodes before to being returned to the circulatory system. Once within the lymphatic system the fluid is called lymph, and has almost the same composition as the original interstitial fluid. Returning the fluid to the blood prevents edema and helps to maintain normal blood volume and pressure.
Lymphatic vessels
Lymphatic vessels, unlike blood vessels, only carry fluid away from the tissues. The smallest lymphatic vessels are the lymph capillaries, which begin in the tissue spaces as blind-ended sacs. There isn’t a central pump, lymph movement occurs slowly with low pressure due to the squeezing action of skeletal muscles. Lymph travels through lymp vessels that are similar to capillaries and veins. Lymph moves in one direction only, due to valves in lymph vessels that are similar to the valves found in veins, shown in Figure above. The lymph is transported to progressively larger lymphatic vessels that drain into the circulatory system at the right and left subclavian veins.
Lymphatic organs
Lymphatic organs are characterized by clusters of leukocyte. When the body is exposed to microorganisms and other foreign substances, the leukocytes proliferate within the lymphatic organs and are sent in the blood to the site of the invasion. This is part of the immune response that attempts to destroy the invading agent.
The four types of lymphatic organs :
.Lymph Nodes
Lymph nodes are small bean-shaped structures that are usually less than 2.5 cm in length. They are widely distributed throughout the body along the lymphatic vessels where they filter the lymph before it is returned to the blood.
Tonsils
Tonsils are clusters of lymphatic tissue just under the mucous membranes that line the nose, mouth, and throat (pharynx).
Spleen
The spleen is located in the upper left abdominal cavity, just beneath the diaphragm, and posterior to the stomach. The spleen filters blood in much the way that the lymph nodes filter lymph. The spleen, along with the liver, removes old and damaged erythrocytes from the circulating blood. Like other lymphatic tissue, it produces leukoocytes, especially in response to invading pathogens
Thymus
The thymus is located anterior to the ascending aorta and posterior to the sternum. It is relatively large in infants and children but after puberty it begins to decrease in size so that in older adults it is quite small. Thymus is where the lymphocytes are processed.
In this link you can complete the description of the lymphatic organs.

Vocabulary of circulatory system

Anemia: The condition of not having enough hemoglobin in the blood to carry oxygen to body cells.
Antibodies: Proteins that identify pathogens or other substances as being harmful; flow in blood; can destroy pathogens by attaching to the cell membrane of the pathogen.
Arteries: Blood vessels that carry blood away from the heart.
Atrioventricular (AV) valves: Valves that stop blood from moving from the ventricles back into the atria.
Atrium: One of the two small, thin-walled chambers on the top of the heart that blood first enters.
Blood: A body fluid that is a type of connective tissue; moves oxygen and other compounds throughout the body.
Blood clotting: The complex process by which blood forms solid clots.
Blood pressure: The force exerted by circulating blood on the walls of blood vessels.
Capillaries: The smallest and narrowest blood vessels in the body.
Cardiovascular system: The organ system that is made up of the heart, the blood vessels, and the blood.
Heart attack: Event that occurs when the blood supply to a part of the heart is blocked.
Hemophilia: A group of hereditary diseases that affect the body's ability to control blood clotting.
Hypertension: Also called high blood pressure; a condition in which a person’s blood pressure is always high;
Leukemia: Cancer of the blood or bone marrow; characterized by an abnormal production of blood cells, usually white blood cells.
Lymphatic system: A network of vessels and tissues that carry a clear fluid called lymph; includes lymph nodes, lymph ducts, and lymph vessels.
Plasma: The golden-yellow liquid part of the blood.
Platelets: Fragments of larger cells that are important in blood clotting.
Pulmonary circulation: The part of the cardiovascular system which carries oxygen-poor blood away from the heart to the lungs, and returns oxygen-rich blood back to the heart.
Red blood cells (RBCs) : Flattened disk-shaped cells that carry oxygen, the most common blood cell in the blood. Mature red blood cells do not have a nucleus.
Semilunar (SL) valves: Found in the arteries leaving the heart; prevents blood flowing back from the arteries into the ventricles.
Sickle cell disease: A blood disease that is caused by abnormally-shaped blood protein hemoglobin.
Stroke: A loss of brain function due to a blockage of the blood supply to the brain.
Systemic circulation: The portion of the cardiovascular system which carries oxygen-rich blood away from the heart to the body, and returns oxygen-poor blood back to the heart.
Veins: Blood vessels that carry blood back to the heart.
Ventricle: One of the two muscular V-shaped chambers that pump blood out of the heart.
White blood cells (WBCs): Nucleated blood cells that are usually larger than red blood cells; defend the body against infection by bacteria, viruses, and other pathogens.

Something different

Belen wants to help us to learn the circulatory system, so she sent me this video from youtube. Maybe, you will improve your understanding of it with a little bit of music.
As this post is a little different from the others, here you have two interesting posts, at least for me, related with music. I discovered them in the blog of music of Ciudad Real CPR
Eric Whitacre's Virtual Choir - 'Lux Aurumque'
World Science Festival 2009: Bobby McFerrin Demonstrates the Power of the Pentatonic Scale

The Composition of Blood

Blood is a fluid connective tissue. It circulates around the body through the blood vessels by the pumping action of the heart.
Blood accounts for about 7% of the human body weight. The average adult has a blood volume of roughly 5 liters, composed of:

1. A fluid called plasma where are the blood cells and other substances.
2. Several kinds of blood cells. Within the blood plasma, are:

• Erythrocytes (red blood cells)
  
• Leukocytes (white blood cells)
  
• Thrombocytes (platelets)

The cells that make up the blood can be seen in Figure

Plasma
Plasma is the golden-yellow liquid part of the blood. Plasma is 90% water and 10% dissolved materials including proteins, glucose, ions, hormones, and gases.
Red Blood Cells
Red blood cells, also known as erythrocytes, are flattened, doubly concave cells that carry oxygen. There are about 4 to 6 million cells per cubic millimeter of blood. Red blood cells are continuously made in the red bone marrow of long bones, ribs, skull, and vertebrae. Each red blood cell lives for only 120 days, after which they are destroyed in liver and spleen.
Mature red blood cells do not have a nucleus or other organelles. They contain the protein hemoglobin which iron and this protein gives blood its red color
White Blood Cells
White blood cells, also known as leukocytes, are generally larger than red blood cells,. They have a nucleus. White blood cells make up less than one percent of the blood's volume. They are made from stem cells in bone marrow. They take part in the immune response. There are five types of white blood cells but the most important are:
Monocytes enter the tissue fluid by squeezing through capillary walls and transform into Macrophages that phagocytose (swallow) cell debris and. bacteria or viruses
Neutrophils also swallow foreign bodies.
Lymphocytes fight infection. They produce antibodies, proteins that travel in blood to identify and neutralize foreign objects, such as bacteria and viruses
Macrophage showing cytoplasmic extensions that allow it to swallow particles or pathogens. In the image here, a mouse macrophage stretches its arms to engulf two particles at once.
Platelets
Platelets, also known as thrombocytes, are small, regularly-shaped clear cell fragments. They are important in blood clotting. Platelets carry chemicals essential to blood clotting. This clot stops more blood from leaving the body when damage to wall of blood vessels occurs

Cells of the blood. From left to right: Red blood cell, platelet, white blood cell.

The Components of Blood

Pulmonary and Systemic Circulations

The double circulatory system of blood flow refers to the separate systems of pulmonary circulation and the systemic circulation in amphibians, birds and mammals, including humans. Pulmonary Circulation
The pulmonary circulation is the portion of the cardiovascular system which carries oxygen-poor (deoxygenated) blood away from the heart, to the lungs, and returns oxygenated blood back to the heart. As shown in Figure, deoxygenated blood from the body leaves the right ventricle through the pulmonary arteries, which carry the blood to each lung. The pulmonary arteries are the only arteries that carry deoxygenated blood. In the lungs, red blood cells release carbon dioxide and pick up oxygen during respiration. The oxygenated blood then leaves the lungs through the pulmonary veins, which return it to the left side of the heart, and complete the pulmonary cycle. In the following scheme of the general body circulation, pulmonary circulation is in the right side and the systemic circulation is on the left side.

Systemic Circulation
The systemic circulation is the portion of the cardiovascular system which carries oxygenated blood away from the heart, to the body, and returns deoxygenated blood back to the heart. Oxygenated blood from the lungs leaves the left ventricle through the aorta, from where it is distributed to the body's organs and tissues, which absorb the oxygen, through a complex network of arteries and capillaries. The deoxygenated blood is then collected by veins and then into the inferior and superior venae cavae, which return it to the right heart, completing the systemic cycle. The blood is then re-oxygenated through the pulmonary circulation before returning again to the systemic circulation.

Pulmonary Circulation	Systemic Circulation
It is a shorter circulation. The circulation is between heart and lungs. Blood is pumped by right part of the heart and received by the left part. It pumps deoxygenated blood into lungs It brings back oxygenated blood to the heart.	It is a larger circulation. The circulation is between heart and remaining parts of the body except lungs. Blood is pumped by left part of the heart and received by the right part. It pumps oxygenated blood to different parts of the body. It brings back deoxygenated blood to the heart.

Just like every other organ in the body, the heart needs its own blood supply, which it gets through the coronary arteries that branch directly from the aorta, just above the heart. They deliver oxygen-rich blood to the heart

Blood Vessels

The blood vessels are part of the cardiovascular system and function to transport blood throughout the body. The two most important types are arteries and veins. Arteries carry blood away from the heart, while veins return blood to the heart. Capillaries are also importan.
Arteries are the large, muscular vessels that carry blood away from the heart toward the organs.. Arteries have thicker walls than veins. The elastic qualities of artery walls allow them to carry pressurized blood from the heart while maintaining blood pressure.
Arteries branch into smaller arteries and finally the capillaries that carry nutrients to the body’s cells and tissues.

Veins are vessels that carry blood from the organs toward the heart. The walls of veins have one-way valves that prevent blood from flowing backward and pooling in the legs, feet, arms or hands due to the pull of gravity. The location of veins can vary from person to person.
Capillaries are the smallest of the body's blood vessels, measuring 5-10 μm in diameter. They connect smoller arteries (arterioles) and smoller veins (venules), and they are important for the exchange of oxygen, carbon dioxide, and other substances between blood and body cells. The walls of capillaries are made of only a single layer of endothelial cells. This layer is so thin that molecules such as oxygen, water and lipids can pass through them by diffusion and enter the body tissues.
In general the term arterial blood is used to describe blood high in oxygen and venous blood to describe blood low in oxygen, although the pulmonary arteries carry deoxygenated blood and blood flowing in the pulmonary vein is rich in oxygen. (...)
Blood Vessels and Blood Pressure
Blood pressure refers to the force exerted by circulating blood on the walls of blood vessels. The pressure of the circulating blood gradually decreases as blood moves from the arteries, capillaries, and veins. The term "blood pressure" generally refers to arterial pressure, which is the pressure in the larger arteries that take blood away from the heart. Arterial pressure results from the force that is applied to blood by the contracting heart, where the blood “presses” against the walls of the arteries. During each heartbeat, BP varies between a maximum (systolic) and a minimum (diastolic) pressure.
The systolic arterial pressure is defined as the peak pressure in the arteries, which occurs systole( contraction); the diastolic arterial pressure is the lowest pressure when the heart is in diastole (relaxation).
the healthy ranges for arterial pressure are:
• Systolic: less than 120 mm Hg
• Diastolic: less than 80 mm Hg
Factors such as age, gender and race influence blood pressure values. Pressure also varies with exercise, emotional reactions, sleep, stress, nutritional factors, drugs, or disease. Hypertension is a condition in which a person’s blood pressure is chronically high.

This link to Discovery Health you have a video with a good explanation of blood pressure and this video is also interesting

The Heartbeat

1. As we saw in the last post, the heart is a four-chambered organ consisting of right and left halves. Two of the chambers, the left and right atria, are entry-points into the heart, while the other two chambers, the left and right ventricles, are responsible for contractions that send the blood through the circulation.
   The circulation is split into the pulmonary and systemic circulation. The right ventricle's role is to pump deoxygenated blood into the pulmonary circulation through the pulmonary artery. The left ventricle's role is to pump now oxygenated blood into the systemic circulation through the aorta.
   The average human heart, beating at 72 beats per minute, will beat approximately 2.5 billion times during an average 66 year lifespan. Sometime the heart can beat fast, this is called Tachycardia. It happen when you make exercise or are in danger.
   The heartbeat is made up of two parts;.
   Systole is the contraction of the heart chambers, which drives blood out of the chambers.
   Diastole is the period of time when the heart relaxes after contraction.
   In the figura you have the cardiac cycle :

• Atrial diastole. The atria were in diastole and blood from the superior and inferior vena cava (rigth side) and pulmonary veins (left side) flows into the atria slowly to fill them and begin the cycle.
• Atrial systole. This phase involves the contraction of the 2 atria, pushing the blood into the respective ventricles. There is no back flow of blood due to the presence of the atrioventricular (AV) valves ( bicuspid valve – left and tricuspid valve -right) . The bicuspid valve is supported by tendons which look rather like the strings of a parachute.
• Ventricular systole. The thick muscular walls of the ventricles contract.. This begins alongside the end of auricular diastole. The pressure on the blood in the ventricles increases. The atrioventricular valves close rapidly to prevent the backward flow of blood into the auricles.
  As the pressure in the ventricle increases, the semilunar valves are opened and blood enters the arteries. From the right ventricle, the deoxygenated blood enters the pulmonary artery. From the left ventricle, the oxygenated blood enters the aorta, to be taken to all body parts.
• Ventricular diastole.Ventricular systole is followed by ventricular diastole. The atria are already in diastole, so all the chambers of the heart are in diastole. As the pressure in the ventricles decreases to prevent the backward flow of blood, the semilunar valves close rapidly.

The sound of the heart valves shutting causes the heart sounds, or a heartbeat. The closing of the mitral and tricuspid valves (known together as the atrioventricular valves) at the beginning of ventricular systole cause the first part of the "lub-dub" sound made by the heart as it beats. The second part of the "lub-dub" is caused by the closure of the aortic and pulmonic valves at the end of ventricular systole. As the left ventricle empties, its pressure falls below the pressure in the aorta, and the aortic valve closes. Similarly, as the pressure in the right ventricle falls below the pressure in the pulmonary artery, the pulmonic valve closes.
Here you have some videos to get a better knowledge of the heartbeat.

The heart

The heart is usually found in the left to middle of the chest with the largest part of the heart slightly to the left. It is about the size of a fist. The heart is surrounded by the lungs.
It is divided into four chambers, the two upper atria and the two lower ventricles. Atria (singular, atrium) are the thin-walled blood collection chambers of the heart. Atria pump the blood into the ventricles. Ventricles are the heart chambers which collect blood from the atria and pump it out of the heart. The four chambers of the heart are shown in Figure. Each of the four chambers of the heart have a specific job, these are:
• The right atrium receives oxygen-poor (deoxygenated) blood from the body this blood enters from the superior vena cava and the inferior vena cava
• The right ventricle pumps oxygen-poor blood through the pulmonary arteries and toward the lungs. In the lungs, carbon dioxide is released from the blood and oxygen is picked up.
• The left atrium receives oxygen-rich (oxygenated) blood from the lungs through the pulmonary veins.
• The left ventricle pumps oxygen-rich blood out of the heart to the rest of the body through the aorta.
On both sides, the lower ventricles are thicker and stronger than the upper atria. The muscle wall surrounding the left ventricle is thicker and stronger than the wall surrounding the right ventricle because the left ventricle needs to exert enough force to pump the blood through the body. The right ventricle only needs to pump the blood as far as the lungs, which does not require as much contractile force.
Valves in the heart maintain the flow of blood by opening and closing in one direction only. Blood can move only forward through the heart, and is prevented from flowing backward by the valves. Such movement of the blood is called unidirectional flow. There are four valves of the heart:
• The two atrioventricular (AV) valves ensure blood flows from the atria to the ventricles, and not the other way. The AV valve on the right side of the heart is called the tricuspid valve, and the one on the left of the heart is called the mitral, or bicuspid valve.
• The two semilunar (SL) valves are present in the arteries leaving the heart, and they prevent blood flowing back from the arteries into the ventricles.

The circulatory system

After seeing digestive and respiratory system, the next one is the cardiovascular system. It has a pretty important function in the nutrition role. As you already know, every cell in your body depends on your cardiovascular system. It keeps all of your cells supplied with nutrients from the intestine (digestive system) and oxygen from the lungs (respiratory system). It also removes their waste products, carbon dioxide to the lungs and the nitrogenous wastes to the kidneys.

Actually the circulatory system has many jobs, but we can cosider three main functions:

• Transport of nutrients, oxygen, and hormones to cells throughout the body and removal of metabolic wastes (carbon dioxide, nitrogenous wastes, and heat).
• Protection of the body by white blood cells and antibodies that circulate in the blood and defend the body against foreign microbes and toxins. Clotting mechanisms are also present that protect the body from blood loss after injuries.
• Regulation of body temperature and fluid pH...

This video can be a good help to begin with the circulatory system.


The cardiovascular system shown in Figure is made up of: The heart
It pushes the blood around your body through the blood vessels. The heart is made of cardiac muscle. Blood is collected in the heart and pumped out to the lungs, where it releases carbon dioxide and picks up oxygen before it is pumped to the rest of the body.
The blood vessels
Their job is to channel the blood around the body. There are three main types of blood vessels in the body; arteries, veins, and capillaries
Arteries are blood vessels that carry blood away from the heart. Further from the heart, arteries form smaller arteries. These smaller arteries branch into smaller vessels. The smaller blood vessels help to bring nutrients and oxygen and take away waste from body tissues.
Capillaries are the tiniest blood vessels in the body located within the tissues of the body. They transport blood from the arteries to the veins. The walls of capillaries are only a single layer of cells thick. Oxygen, carbon dioxide, nutrients, and wastes are exchanged through their thin walls. Capillaries are so narrow that blood cells must move in single file through them.
Veins are blood vessels that carry back the blood from the different regions of the body to the heart.
The blood
Blood is a body fluid that is a type of connective tissue. Blood is made of blood cells, and a fluid called plasma. The main types of cells found in blood are red blood cells and white blood cells.
Finally remember you something you studied last course. The cardiovascular system of humans is closed. That means the blood never leaves the large loop of blood vessels in which it travels. Other animals such as invertebrates have open circulatory systems, in which their blood can leave the blood vessels.