lymphatic system anatomy and physiology pdf

Lymphatic System Anatomy And Physiology Pdf

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Last reviewed: June A system of vessels in the vertebrate body, beginning in a network of exceedingly thin-walled capillaries in almost all the organs and tissues, except the brain and bones. The lymphatic system is a one-way vascular network in vertebrates that works in parallel with the blood circulation Fig.

19.1A: Structure of the Lymphatic System

The immune system is the complex collection of cells and organs that destroys or neutralizes pathogens that would otherwise cause disease or death. The lymphatic system, for most people, is associated with the immune system to such a degree that the two systems are virtually indistinguishable.

The lymphatic system is the system of vessels, cells, and organs that carries excess fluids to the bloodstream and filters pathogens from the blood. The swelling of lymph nodes during an infection and the transport of lymphocytes via the lymphatic vessels are but two examples of the many connections between these critical organ systems.

A major function of the lymphatic system is to drain body fluids and return them to the bloodstream. Blood pressure causes leakage of fluid from the capillaries, resulting in the accumulation of fluid in the interstitial space—that is, spaces between individual cells in the tissues.

In humans, 20 liters of plasma is released into the interstitial space of the tissues each day due to capillary filtration. Once this filtrate is out of the bloodstream and in the tissue spaces, it is referred to as interstitial fluid. Of this, 17 liters is reabsorbed directly by the blood vessels.

But what happens to the remaining three liters? This is where the lymphatic system comes into play. It drains the excess fluid and empties it back into the bloodstream via a series of vessels, trunks, and ducts. Lymph is the term used to describe interstitial fluid once it has entered the lymphatic system. This inappropriate accumulation of fluid referred to as lymphedema may lead to serious medical consequences.

As the vertebrate immune system evolved, the network of lymphatic vessels became convenient avenues for transporting the cells of the immune system. Additionally, the transport of dietary lipids and fat-soluble vitamins absorbed in the gut uses this system. Cells of the immune system not only use lymphatic vessels to make their way from interstitial spaces back into the circulation, but they also use lymph nodes as major staging areas for the development of critical immune responses.

A lymph node is one of the small, bean-shaped organs located throughout the lymphatic system. Visit this website for an overview of the lymphatic system. What are the three main components of the lymphatic system?

The lymphatic vessels begin as open-ended capillaries, which feed into larger and larger lymphatic vessels, and eventually empty into the bloodstream by a series of ducts. Along the way, the lymph travels through the lymph nodes, which are commonly found near the groin, armpits, neck, chest, and abdomen. Humans have about — lymph nodes throughout the body. Figure 1. Lymphatic vessels in the arms and legs convey lymph to the larger lymphatic vessels in the torso.

A major distinction between the lymphatic and cardiovascular systems in humans is that lymph is not actively pumped by the heart, but is forced through the vessels by the movements of the body, the contraction of skeletal muscles during body movements, and breathing. One-way valves semi-lunar valves in lymphatic vessels keep the lymph moving toward the heart. Lymph flows from the lymphatic capillaries, through lymphatic vessels, and then is dumped into the circulatory system via the lymphatic ducts located at the junction of the jugular and subclavian veins in the neck.

Lymphatic capillaries , also called the terminal lymphatics, are vessels where interstitial fluid enters the lymphatic system to become lymph fluid. Located in almost every tissue in the body, these vessels are interlaced among the arterioles and venules of the circulatory system in the soft connective tissues of the body. Exceptions are the central nervous system, bone marrow, bones, teeth, and the cornea of the eye, which do not contain lymph vessels.

Figure 2. Lymphatic capillaries are interlaced with the arterioles and venules of the cardiovascular system. Collagen fibers anchor a lymphatic capillary in the tissue inset.

Interstitial fluid slips through spaces between the overlapping endothelial cells that compose the lymphatic capillary. Lymphatic capillaries are formed by a one cell-thick layer of endothelial cells and represent the open end of the system, allowing interstitial fluid to flow into them via overlapping cells. Entry of fluid into lymphatic capillaries is also enabled by the collagen filaments that anchor the capillaries to surrounding structures. As interstitial pressure increases, the filaments pull on the endothelial cell flaps, opening up them even further to allow easy entry of fluid.

In the small intestine, lymphatic capillaries called lacteals are critical for the transport of dietary lipids and lipid-soluble vitamins to the bloodstream. In the small intestine, dietary triglycerides combine with other lipids and proteins, and enter the lacteals to form a milky fluid called chyle.

The chyle then travels through the lymphatic system, eventually entering the liver and then the bloodstream. The lymphatic capillaries empty into larger lymphatic vessels, which are similar to veins in terms of their three-tunic structure and the presence of valves. These one-way valves are located fairly close to one another, and each one causes a bulge in the lymphatic vessel, giving the vessels a beaded appearance.

The superficial and deep lymphatics eventually merge to form larger lymphatic vessels known as lymphatic trunks. On the right side of the body, the right sides of the head, thorax, and right upper limb drain lymph fluid into the right subclavian vein via the right lymphatic duct.

On the left side of the body, the remaining portions of the body drain into the larger thoracic duct, which drains into the left subclavian vein. The thoracic duct itself begins just beneath the diaphragm in the cisterna chyli , a sac-like chamber that receives lymph from the lower abdomen, pelvis, and lower limbs by way of the left and right lumbar trunks and the intestinal trunk. Figure 3. The thoracic duct drains a much larger portion of the body than does the right lymphatic duct.

The overall drainage system of the body is asymmetrical. The right lymphatic duct receives lymph from only the upper right side of the body. The lymph from the rest of the body enters the bloodstream through the thoracic duct via all the remaining lymphatic trunks. In general, lymphatic vessels of the subcutaneous tissues of the skin, that is, the superficial lymphatics, follow the same routes as veins, whereas the deep lymphatic vessels of the viscera generally follow the paths of arteries.

The immune system is a collection of barriers, cells, and soluble proteins that interact and communicate with each other in extraordinarily complex ways. The modern model of immune function is organized into three phases based on the timing of their effects. The three temporal phases consist of the following:. The cells of the blood, including all those involved in the immune response, arise in the bone marrow via various differentiation pathways from hematopoietic stem cells.

In contrast with embryonic stem cells, hematopoietic stem cells are present throughout adulthood and allow for the continuous differentiation of blood cells to replace those lost to age or function. These cells can be divided into three classes based on function:. Figure 4. All the cells of the immune response as well as of the blood arise by differentiation from hematopoietic stem cells. Platelets are cell fragments involved in the clotting of blood.

As stated above, lymphocytes are the primary cells of adaptive immune responses see Table 1 for more details. The two basic types of lymphocytes, B cells and T cells, are identical morphologically with a large central nucleus surrounded by a thin layer of cytoplasm. They are distinguished from each other by their surface protein markers as well as by the molecules they secrete.

While B cells mature in red bone marrow and T cells mature in the thymus, they both initially develop from bone marrow. T cells migrate from bone marrow to the thymus gland where they further mature. B cells and T cells are found in many parts of the body, circulating in the bloodstream and lymph, and residing in secondary lymphoid organs, including the spleen and lymph nodes, which will be described later in this section.

The human body contains approximately 10 12 lymphocytes. B cells are immune cells that function primarily by producing antibodies. An antibody is any of the group of proteins that binds specifically to pathogen-associated molecules known as antigens. An antigen is a chemical structure on the surface of a pathogen that binds to T or B lymphocyte antigen receptors. Once activated by binding to antigen, B cells differentiate into cells that secrete a soluble form of their surface antibodies.

These activated B cells are known as plasma cells. The T cell , on the other hand, does not secrete antibody but performs a variety of functions in the adaptive immune response. Different T cell types have the ability to either secrete soluble factors that communicate with other cells of the adaptive immune response or destroy cells infected with intracellular pathogens.

The roles of T and B lymphocytes in the adaptive immune response will be discussed further in this chapter. Another type of lymphocyte of importance is the plasma cell. A plasma cell is a B cell that has differentiated in response to antigen binding, and has thereby gained the ability to secrete soluble antibodies. These cells differ in morphology from standard B and T cells in that they contain a large amount of cytoplasm packed with the protein-synthesizing machinery known as rough endoplasmic reticulum.

A fourth important lymphocyte is the natural killer cell, a participant in the innate immune response.

A natural killer cell NK is a circulating blood cell that contains cytotoxic cell-killing granules in its extensive cytoplasm. It shares this mechanism with the cytotoxic T cells of the adaptive immune response. Visit this website to learn about the many different cell types in the immune system and their very specialized jobs.

What is the role of the dendritic cell in an HIV infection? Understanding the differentiation and development of B and T cells is critical to the understanding of the adaptive immune response. The primary lymphoid organs are the bone marrow, spleen, and thymus gland. The lymphoid organs are where lymphocytes mature, proliferate, and are selected, which enables them to attack pathogens without harming the cells of the body.

Figure 5. Red bone marrow fills the head of the femur, and a spot of yellow bone marrow is visible in the center. The white reference bar is 1 cm. In the embryo, blood cells are made in the yolk sac. As development proceeds, this function is taken over by the spleen, lymph nodes, and liver. Later, the bone marrow takes over most hematopoietic functions, although the final stages of the differentiation of some cells may take place in other organs.

The red bone marrow is a loose collection of cells where hematopoiesis occurs, and the yellow bone marrow is a site of energy storage, which consists largely of fat cells. The B cell undergoes nearly all of its development in the red bone marrow, whereas the immature T cell, called a thymocyte , leaves the bone marrow and matures largely in the thymus gland.

The thymus gland is a bilobed organ found in the space between the sternum and the aorta of the heart. Connective tissue holds the lobes closely together but also separates them and forms a capsule. Fiugre 6.

Lymphatic system

The lymphatic system is a collection of structures and vessels that drains lymph from blood and has several other functions. It is a circulatory system for lymph fluid and the site of many key immune system functions. The lymphatic vessels are the lymphatic system equivalent of the blood vessels of the circulatory system and drain fluid from the circulatory system. The network of lymph vessels consists of the initial collectors of lymph fluid, which are small, valveless vessels, and goes on to form the precollector vessels, which have rudimentary valves that are not fully functional. These structures then form increasingly larger lymphatic vessels which form colaterals and have lymph-angions lymph hearts. The larger lymph vessels contain valves that prevent the backflow of lymph.

The immune system is the complex collection of cells and organs that destroys or neutralizes pathogens that would otherwise cause disease or death. The lymphatic system, for most people, is associated with the immune system to such a degree that the two systems are virtually indistinguishable. The lymphatic system is the system of vessels, cells, and organs that carries excess fluids to the bloodstream and filters pathogens from the blood. The swelling of lymph nodes during an infection and the transport of lymphocytes via the lymphatic vessels are but two examples of the many connections between these critical organ systems. A major function of the lymphatic system is to drain body fluids and return them to the bloodstream. Blood pressure causes leakage of fluid from the capillaries, resulting in the accumulation of fluid in the interstitial space—that is, spaces between individual cells in the tissues. In humans, 20 liters of plasma is released into the interstitial space of the tissues each day due to capillary filtration.

The lymphatic system , or lymphoid system , is an organ system in vertebrates that is part of the circulatory system and the immune system. It is made up of a large network of lymph, lymphatic vessels , lymph nodes, lymphatic or lymphoid organs, and lymphoid tissues. Unlike the cardiovascular system, the lymphatic system is not a closed system. The human circulatory system processes an average of 20 litres of blood per day through capillary filtration , which removes plasma from the blood. Roughly 17 litres of the filtered plasma is reabsorbed directly into the blood vessels , while the remaining three litres are left in the interstitial fluid. One of the main functions of the lymphatic system is to provide an accessory return route to the blood for the surplus three litres.

What does the lymphatic system do?

The lymphatic system consists of all lymphatic vessels and lymphoid organs. Hence, rather than representing a single organ, the lymphatic system comprises a circulatory network of vessels and lymphoid tissue and cells in every part of the body. It works together closely with the blood-producing haematopoietic system in the bone marrow, thereby playing a vital role in immune responses to protect the body from various pathogens. Also, the lymphatic vessel network helps transporting nutrients and waste products in the body.

The lymphatic system is part of the immune system. It also maintains fluid balance and plays a role in absorbing fats and fat-soluble nutrients. The lymphatic or lymph system involves an extensive network of vessels that passes through almost all our tissues to allow for the movement of a fluid called lymph.

Functions of the Lymphatic System

 Городская больница, - буркнула зачумленная секретарша. Беккер заговорил по-испански с сильным франко-американским акцентом: - Меня зовут Дэвид Беккер. Я из канадского посольства. Наш гражданин был сегодня доставлен в вашу больницу. Я хотел бы получить информацию о нем, с тем чтобы посольство могло оплатить его лечение.

Сьюзан высвободилась из рук обмякшего Хейла, не понимая, что произошло. Стратмор подхватил ее и слегка обнял, пытаясь успокоить. - Ш-ш-ш, - утешал он.  - Это. Теперь все в порядке.

Внезапно камера отъехала в сторону, под деревья. В кадре возник мужчина в очках в тонкой металлической оправе, в руке он держал большой портфель. Выйдя на открытое место и бросив взгляд на корчащегося на земле Танкадо, он задвигал пальцами, словно исполнял ими какой-то причудливый танец над коробочкой, которую держал в руке. - Он работает на Монокле, - пояснил Смит.  - Посылает сообщение о том, что Танкадо ликвидирован. Сьюзан повернулась к Беккеру и усмехнулась: - Похоже, у этого Халохота дурная привычка сообщать об убийстве, когда жертва еще дышит. Камера последовала за Халохотом, двинувшимся в направлении жертвы.

Lymphatic system

Нуматака чуть не расхохотался, но в голосе звонившего слышалась подозрительная решимость. - Если Танкадо перестанет быть фактором? - вслух размышлял Нуматака.  - Тогда мы с вами придем к соглашению.

Честь. Страна. Однако в списке было еще одно сообщение, которого он пока не видел и которое никогда не смог бы объяснить.

Сообщения поступали мгновенно, и их нельзя было отследить. Он торопливо повернул выключатель. Стекла очков блеснули, и его пальцы снова задвигались в воздухе. Он, как обычно, записал имена жертв.

 Да… и… - слова застревали у нее в горле. Он убил Дэвида. Бринкерхофф положил руку ей на плечо.

4 comments

Fredeswinda R.

Lymphatic system , a subsystem of the circulatory system in the vertebrate body that consists of a complex network of vessels, tissues , and organs.

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ZГіsimo M.

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Amabella J.

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Jason E.

network of tissues, organs and vessels that help to maintain the body's fluid balance & protect it from pathogens. • lymphatic vessels, lymph nodes, spleen.

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