Blood and the Lymphatic and Immune System<br />Lorretha Members<br />
Blood capillaries allow fluid to leave and enter, the circulatory system.<br />
The lymphatic system works in close cooperation with other body systems to perform these important functions:<br /><ul><li>The lymphatic system aids the immune system in destroying pathogens and filtering waste so that the lymph can be safely returned to the circulatory system.
To remove excess fluid, waste, debris, dead blood cells, pathogens, cancer cells, and toxins from these cells and the tissue spaces between them.
The lymphatic system also works with the circulatory system to deliver nutrients, oxygen, and hormones from the blood to the cells that make up the tissues of the body.
Important protein molecules are created by cells in the tissues. Because these molecules are too large to enter the capillaries of the circulatory system, these protein molecules must be transported by the lymph to the bloodstream at the terminus.</li></li></ul><li>Lymph originates as plasma, which is the fluid portion of blood. The arterial blood that flows out of the heart slows as it moves through a capillary bed. This slowing allows some plasma to leave the arterioles and flow into the tissues where it becomes tissue fluid.<br />Also known as intercellular fluid, or interstitial fluid, this tissue fluid delivers nutrients, oxygen, and hormones to the cells. <br />As this fluid leaves the cells, it takes with it cellular waste products and protein cells. <br />Approximately 90 percent of this tissue fluid flows into the venules. Here it enters the venous circulation as plasma and continues in the circulatory system. <br />The remaining 10 percent of the fluid that is left behind is now known as lymph. <br />
The bloodstream is pumped by the heart. It circulates throughout the body and is cleansed by being filtered by the kidneys. The lymphatic system does not have a pump to aid in its flow, instead this system is designed so that lymph only flows upward through the body traveling from the extremities (feet and hands) and upward through the body toward the neck.<br />As it travels through the body, lymph passes through lymph nodes where it is filtered. At the base of the neck, the lymph enters the subclavian veins and once again becomes plasma in the bloodstream.<br />
The lymphatic capillaries gradually join together to form a mesh-like network of tubes that are located deeper in the body. As they become larger, these structures are known as lymphatic vessels. <br /><ul><li>Deeper within the body the lymphatic vessels become progressively larger and are located near major veins.
Like veins, lymphatic vessels, which are known as lymphangions have one-way valves to prevent any backward flow.
Each angions is a segment created by the space between two sets of valves.
Smooth muscles in the walls of the lymphatic vessels cause the angions to contract sequentially to aid the flow of lymph toward the thoracic region. Because of their shape, these vessels are previously referred to as a string of pearls.</li></li></ul><li>Drains lymph from the left side of the head and neck <br />The Left arm and the left upper quadrant <br />The lower trunk and both legs <br />The cisternachyli temporarily stores lymph as it moves upward from the lower areas of the body. <br />The thoracic duct transports lymph upward to the left lymphatic duct. <br />The left lymphatic duct empties the lymph into the left subclavian vein.<br />
<ul><li>Drains lymph from the right side of the head and neck
Lymph from this area flows into the right lymphatic duct.
This duct empties the lymph into the right subclavian vein. </li></li></ul><li>The leukocytes are further subdivided into granulocytes (containing large granules in the cytoplasm) and agranulocytes (without granules). The granulocytes consist of neutrophils (55–70%), eosinophils (1–3%), and basophils (0.5–1.0%). The agranulocytes are lymphocytes (consisting of B cells and T cells) and monocytes. Lymphocytes circulate in the blood and lymph systems, and make their home in the lymphoid organs. <br />
There are 5000–10,000 WBCs per mm3 and they live 5-9 days. About 2,400,000 RBCs are produced each second and each lives for about 120 days (They migrate to the spleen to die. Once there, that organ scavenges usable proteins from their carcasses). A healthy male has about 5 million RBCs per mm3, whereas females have a bit fewer than 5 million. <br />
The first and, arguably, most important barrier is the skin. The skin cannot be penetrated by most organisms unless it already has an opening, such as a nick, scratch, or cut. <br />Mechanically, pathogens are expelled from the lungs by ciliary action as the tiny hairs move in an upward motion; coughing and sneezing abruptly eject both living and nonliving things from the respiratory system; the flushing action of tears, saliva, and urine also force out pathogens, as does the sloughing off of skin. <br />Sticky mucus in respiratory and gastrointestinal tracts traps many microorganisms. <br />Acid pH (< 7.0) of skin secretions inhibits bacterial growth. Hair follicles secrete sebum that contains lactic acid and fatty acids both of which inhibit the growth of some pathogenic bacteria and fungi. Areas of the skin not covered with hair, such as the palms and soles of the feet, are most susceptible to fungal infections. Think athlete's foot. <br />Saliva, tears, nasal secretions, and perspiration containlysozyme.An enzyme that destroys Gram positive bacterial cell walls causing cell lysis. Vaginal secretions are also slightly acidic (after the onset of menses). Spermine and zinc in semen destroy some pathogens. Lactoperoxidase is a powerful enzyme found in mother's milk. <br />The stomach is a formidable obstacle insofar as its mucosa secrete hydrochloric acid (0.9 < pH < 3.0, very acidic) and protein-digesting enzymes that kill many pathogens. The stomach can even destroy drugs and other chemicals. <br /> <br />