Human Circulatory System
Major Tissues And Organs:
- Blood
- Heart
- Blood Vessels
- Lymph Nodes
- Lymphatic Vessles
- Transport oxygen, nutrients, wastes; helps regulate body temperature; collects fluid lost from blood vessels and returns it to circulatory system.
Blood- Erythrocytes,LEUKOCYTES, and PLasma
- Functions of Blood
Delivering oxygen from the lungs and nutrients from the digestive tract to all body cells.
Transporting metabolic waste products from cells to elimination sites (to lungs to eliminate carbon dioxide, and to the kidneys to dispose of nitrogenous wastes in urine).
Transporting hormones from the endocrine organs to their target organs.
Regulation:
Maintaining appropriate body temperature by absorbing and distributing heat throughout the body and to the skin surface to encourage heat loss.
Maintaining normal pH in body tissues. Many blood proteins and other bloodborne solutes act as buffers to prevent excessive or abrupt changes in blood pH that could jeoperdize normal cell activities.
Maintaining adequate fluid volume in the circulatory system. Blood proteins prevent excessive fluid loss from the blood steam into the tissue spaces. Fluid volume in the blood vessels remains ample to support efficient circulation to all parts of the body.
Protection:
Preventing blood loss. When a blood vessel is damaged, platelets and plasma proteins initiate clot formation, halting blood loss.
Preventing infection. In blood are antibodies, complement proteins and white blood cells, help defend body.
Blood is made up of 45% blood cells and 55% plasma.
Structure and functions of plasma:
Plasma is mostly water about 90%. It has over 100 different dissolved solutes including nutrients, gases, hormones, wastes and products of cell activity, proteins, and inorganic ions (electrolytes). Plasma proteins are about 8% of plasma weight which serve a variety of functions but not to be used as fuels or metabolic nutrients.
Red blood cells/Erthrocytes:
Structure: Biconcave discs- discs with depressed centers, lighter in color at their thin center than at their edges. This provides a huge surface area relative to volume, no point within the cytoplsm is far from surface. Mature erthrocytes lack a nucelus and have essentially no organelles. Basically bags of hemoglobin. Discounting water content, rbc is over 97% hemoglobin.
Function: Transports respiratory gases (oxygen and carbon dioxide). Picks up oxygen in the capillaries of the lungs and releases it to tissue cells across other capillaries throughout the body. Hemoglobin which binds easily to oxygen makes up most of erythrocytes. Hemeglobin molecule can transport four molecules of oxygen because each iron atom can combine reversibly with one molecule of oxygen. Oxygen loading occurs in the lungs and the direction of transport is from lungs to tissue cells.
Production: Blood cell production is called hematopoiesis which occurs in the red bone marrow. As they mature they migrate through the thin walls to enter the blood stream. An ounce of new blood contains100 billions new cells everyday.
Destruction and recycling:
Erythrocytes last 100-120 days, unable to synthesize new proteins, grow or divide. They become incresingly rigid or fragile and hemoglobin begins to degenerate. Bilirubin is released in blood and binds to albumin for transport. Liver cells pick up the bilirubin and in turn secrete it (in bile) into the intestine where it is metabolized. The protein part of hemoglobin is metabolized or brokeen down to amino acids, which are released to the circulation.
White blood cells/ leukocytes, 5 types and functions of each:
Neutrophils: Accounts for 50-70% of the WBC population. Body’s bacteria slayers. Numbers increase explosively during acute bacterial infections such as menigitis. Chemically attracted to site ofs inflammation and are active phagocytes.
Eosinphils: 2-4% of all leukocytes. Is to lead the counter attack against parasitic worms, and round worms that are too large to be phagocytized. Important modulators of immune response.
Basophils: Rarest white blood cells, Contains histamine-containing granules. Histamine is an inflammatory chemical that acts as a vasodilator (dilates blood vessels) and attracts white blood cells to the inflamed site.
Lymphocytes: Accounting for 25% or more of the WBC population. They are closely assosciated with lymphoid tissues, ie lymph nodes and spleen, where they play a crucial role to immunity. T lymphocytes: function in the immune response by acting directly against virus-infected cells and tumor cells. B lymphocytes: give rise to plasma cells, which produce antibodies that are released to the blood.
Monocytes: account for 3-8% of WBC’s. When a monocyte leaves the blood stream and enter tissues they become a highly mobile macrophage and are crucial in the bodys defense against viruses, certain intracellular bacterial parasites,and chronic infections.
HEart and blood vessels
Diagram of the Human Heart
Heart: The heart has four chambers, two superior atria and two inferiror ventricles.
Atria are receiving chambers for bood returning to the heart from the circulation (atria-entryway). They need to contract only minimally to push blood “downstairs” into the ventricles through valves. The valve going from the right ventricle to the right atrium is called the tricuspid valve and the left atrium pushes blood to the ventricle through the mitral valve. These valves are flaps of tissues that prevent from back flowing into the atrium.
Right Atrium: Superior vena cava, returns blood from body regions superior to the diaphragm and Inferior vena cava, returns blood from body areas below the diaphragm into the right atrium.
Left Atrium: Four pulmonary veins transport oxygenated blood from the lungs back to the heart (left atrium).
Ventricles: When contracted, they propel blood out of the heart into the circulaton. The right ventricle pumps deoxygenated blood into pulmonary trunk which routes the blood to the lungs where gas exhange occurs. The left ventricle ejects oxygenated blood into the aorta, the largest artery in the body, and out to the rest of the body. When ejecting blood out of the ventricles, the left ventricle ejects through the pulmonary valve and the right ventricle ejects through the aortic valve which are both semilunar valves. THese valves prevent the backflow of blood into the ventricles.
Arteries bring oxygenated blood from the heart to the tissues and organs of the body.
Elastic arteries: Thick walled arteries near the heart, aorta and major branches. They have large lumens and low resistance. They contain more elastin than any other vessel. Although still have smooth muscle they are rather inactive in contraction. These arteries expand and recoil as the heart ejects blood.
Muscular arteries: Elastic arteries give way to the muscular arteries which deliver blood to specific body organs. Internal diameter ranges from that of a little finger to the tip of a lead pencil. These arteries are relatively more muscle tissue and less elastin than elastic arteries, more active in vasoconstriction and less capable of stretching.
Capillaries: Smallest blood vessels, consist of just a thin tunica intima. Red blood cells slip through in single file. The capillaries role is to exchange of materials (gases, nutrients, hormones and so on) between blood and interstitial fluid).
Veins: Veins bring deoxygenated blood from the tissues and organs of the body back to the heart. Veins have thin walls with large lumens. Very little smooth muscle or elastin but rather have a thick tunica made of collagen fibers and elastic networks. Veins accommodate a fairly large blood volume and they can hold up to 65% of the bodys blood supply at any time.
Atria are receiving chambers for bood returning to the heart from the circulation (atria-entryway). They need to contract only minimally to push blood “downstairs” into the ventricles through valves. The valve going from the right ventricle to the right atrium is called the tricuspid valve and the left atrium pushes blood to the ventricle through the mitral valve. These valves are flaps of tissues that prevent from back flowing into the atrium.
Right Atrium: Superior vena cava, returns blood from body regions superior to the diaphragm and Inferior vena cava, returns blood from body areas below the diaphragm into the right atrium.
Left Atrium: Four pulmonary veins transport oxygenated blood from the lungs back to the heart (left atrium).
Ventricles: When contracted, they propel blood out of the heart into the circulaton. The right ventricle pumps deoxygenated blood into pulmonary trunk which routes the blood to the lungs where gas exhange occurs. The left ventricle ejects oxygenated blood into the aorta, the largest artery in the body, and out to the rest of the body. When ejecting blood out of the ventricles, the left ventricle ejects through the pulmonary valve and the right ventricle ejects through the aortic valve which are both semilunar valves. THese valves prevent the backflow of blood into the ventricles.
Arteries bring oxygenated blood from the heart to the tissues and organs of the body.
Elastic arteries: Thick walled arteries near the heart, aorta and major branches. They have large lumens and low resistance. They contain more elastin than any other vessel. Although still have smooth muscle they are rather inactive in contraction. These arteries expand and recoil as the heart ejects blood.
Muscular arteries: Elastic arteries give way to the muscular arteries which deliver blood to specific body organs. Internal diameter ranges from that of a little finger to the tip of a lead pencil. These arteries are relatively more muscle tissue and less elastin than elastic arteries, more active in vasoconstriction and less capable of stretching.
Capillaries: Smallest blood vessels, consist of just a thin tunica intima. Red blood cells slip through in single file. The capillaries role is to exchange of materials (gases, nutrients, hormones and so on) between blood and interstitial fluid).
Veins: Veins bring deoxygenated blood from the tissues and organs of the body back to the heart. Veins have thin walls with large lumens. Very little smooth muscle or elastin but rather have a thick tunica made of collagen fibers and elastic networks. Veins accommodate a fairly large blood volume and they can hold up to 65% of the bodys blood supply at any time.
Lymphatic system
- Structure and Function of Lymphatic Vessels: Elaborate network of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream. A one way system in which lymph flows only toward the heart
- Lymph Capillaries: Weave between the tissue cells and blood capillaries and are very permeable. The edges of adjacent cells overlap each other loosely, forming easily opened, flap like minivalves. Collagen filaments anchor the endothelial cells to surrounding structures so that any increase in interstitial fluid vole opens the minivalves rather than causing the capillaries to collapse.
- Flow in cappillaries: When fluid pressure in the interstitial space is greater than the pressure in the lymphatic capillary, the minivalve flaps gape open allowing fluid to enter. Proteins in interstitial fluid can enter the lymph caps easily, also large particles such as cell disease and pathogens. Special capts, lacteals tansport absorbed fat from small intestine to blood stream.
Lymph Nodes: Have two basic functions, filtration and immune system activation. In nodes, macrophages remove and destroy microorganism, preventing them from being delivered to the blood and spreading to other parts of the body. Bacteria passes through several nodes before it is completely cleansed.
Lymphoid cells : Lymphocytes arrise in red bone marrow T or B lymphocytes. T cells directly attack and destroy infected cells (tumor cells). B cells protect the body by producing plasma cells, that secrete antibodies into the blood. Antibodies mark antigens for destruction by phagocytes or other means
Fun Fact: The average Human's heart beat's 3 billion times during their life