The interconnected system of spaces and vessels between cells in the body's connective tissues and the specialized organs (bone marrow, thymus, spleen, lymph nodes, tonsils, and diffuse nodular lyphatic tissues) through which lymph circulates throughout the body.
functions of the lymphatic system
Its functions include transport of absorbed lipids from meals, the return of excess extracellular/interstitial fluid to the cardiovascular system, and a variety of immune defense functions.
The specific name given to the clear, yellowish protein-poor fluid located between cells in all tissues except blood after it has been collected into the vessels of the lymphatic drainage system
Its functions include transport of lipids from the meals, the return of excess extracellular/interstitial fluid to the cardiovascular system, and a variety of immune defense functions
lymph flow regulation
Lymph flow is regulated by Interstitial Fluid Hydorstatic Pressure, the muscular pump in the limbs, the thoracic pump in the chest, and valves which prevent backflow.
The smallest lymph vessels which are open at the distal end to admit lymph (interstitial/extracellular fluid/tissue fluid)from the tissue spaces
walls of lymph capillaries
The walls consist of a simple squamous endothelium with a poorly developed basement membrane
Any of the delicate thin-walled vascular tubes, lined with endothelium and a very thin outer areolar connective tissue wrapping, which transport lymph from the tissue spaces back to systemic circulation; some of the larger vessels have valves to preven backflow; these vessels anastamose freely with one another; these vessels are interrupted in various locations by lymph nodes. AKA--lymphatic vessels, lymphatics
Collagen fiber which attach the endothelial cells of lymph capillaries to the surrounding tissue structures ao that any increase in interstitial fluid volume opens the miinivalves (loose connections between endothelial cells), rather than causing the lymph capillaries to collapse
Any of the numerous minute lymph capillaries, located in the intestinal villi, which convey chyle (lymph containing lipids absorbed from the meal and packaged in chylomicrons) from the intestines to the lymphatic circulation and therby to the thoracic duct and then to the system blood circulation
A milky fluid consisting of lymph and emulsified fat packaged in chylomicrons, extracted from chyme (the liquid contents of the small intestines) by the lacteals during digestion, and passed to the bloodstream through the lymphatic system to the thoracic duct and then to the systemic blood circulation
The next-to-largest lymphatic vessels which collect lymph fluid form the various regional lymphatic collecting ducts and units to form the two largest lymphatic vessels, the right lymphatic duct and the thoracic duct (left lymphatic duct)
walls of lymph trunks
These vessels are delicate thin-walled vascular tubes, lined with endothelium and a thin outer areolar connective tissue wrapping
thoracic duct/left lymphatic duct
The main lymphatic channel of the body which drains lymph back to the systemic circulation from the entire body except for the right arm, thorax, head and neck; it begins as a continuation of the cisterna chyli at the level of T12 and runs parallel to the aorta for much of its length until it turns to merge with the left subclavian vein
walls of the thoracic duct/left lymphatic duct
This vessel is a delicate thin-walled vascular tube, lined with endothelium and a thin outer areolar connective tissue wrapping
The distal (inferior) portion of the thoracic duct, sometimes slightly larger in diameter, which collects lymph fluid from the various lymph trunks of the lower legs and lower abdominal cavity
cisterna chyli location
It is located ot the level of L2
right lymphatic duct
The minor lymphatic channel of the body which drains lymph back to the systemic circulation from only the right arm, thorax, head and neck; it is quite short, forming several nearby lymphatic trunks, and usually merges with the right jugular vein.
walls of te right lymphatic duct
This vessle is a delicat thin-walled vascular tube, lined with endothelium and a thin outer areolar connective tissue wrapping
resistance (to disease)/nonspecific resistance
The general term for all body defenses against injury and disease which are non-specific in the sense of not being generated in response to a specific foreign antigen(s)
examples of nonspecific resistance
examples include surface barriers (skin and mucous membranes), and their protective secreations (sweat, sebum, cerumen, saliva, the acidity of urine, vaginal, and gastric secretions), the process of vomiting (to expel toxins), inflammation and fever, various antimicrobial proteins (lysozymes, complement, transferrins, interferons) and mediators of inflammation and fever (histamine, kinins, protaglandins, leukotrienes, etc) and the actions of the Natural Killer (NK) lymphocytes
susceptability (to disease)
The property of an individual, an organ system, organ or tissue to be affected by disease; it is affected by environmental factors as well as genetics, developmental, and nutrition factors which lower one's resistance
the functions of the lymphatic system
1. to return excess interstital fluid (lymph) and its dissolved solutes (electrolytes, nutrients, wastes, regulatory substances, immune system molecules) to systemic circulation
2.to transport dietary fats/lipids (in form of chylomicrons) absorbed from meals at the intestines to the adipocytes via the systemic circulation
3. to contribute to specific immune defenses by a.serving as a route for leukocyte movements, b.filtering lymph at the lymph nodes, c.filtering blood in the spleen, d.providing the location and opportunity for specific leukocytes, especially lymphocytes, to encounter and respond to foreign and tumor antigens
3 means/mechanisms by which lymph flow (return to the circulartory system) is facilitated
1. valves in lymphatic vessels which prevent backflow within the lymphatic drainage system
2.skeletal muscle pump- the contraction of skeletal muscles in the limbs to assist with lymph return from the limbs; the skeletal muscle action provides an extracellular compression on these lymph vessels which moves the lymph foward back toward the systemic circulation
3.respiratory pump- the contraction of the diaphragm and the intercostal muscles in the thoracic cavity assists with lymph return to systemic circulation because each time a person inhales, there is a slight but significant drop in internal thoracic pressure which creates a pressure gradient which assists in the flow of lymph
How are lymph vessels similar to blood vessels?
they are both 1. lined with a simple squamous endothelium, 2. have varying amounts of fibrous connective tissue adventitia wrapping their outer surfaces, 3. transmit a fluid in a single direction with little or no backflow permitted
How are lymph vessels different from blood vessels?
1. lymph vessels are delicate and thin-walled and lack a tunica media with smooth muscle, while blood vessels are thicker walled and always have some amount of smooth muscle in their walls
2. lymph vessels transmit lymph, while blood vessels transmit blood
3. all lymph vessels have valves while only some veins and no arteries have valves
4. lymph vessels form a functionally open system in that tissue fluid can be passed directly from the tissue apsce into the interior of te lymph vessels, while blood in blood vessels form a functionally closed system and tissue fluid never enters the interior of the blood vessel unless an injury has occured
Describe the basic components of lymphatic tissue.
1.capsule- a dense irregular fibrous connective tissue sheath external to the lymphatic tissue; present in the htymus, the lymph nodes, and the spleen, but absent in the red bone marrow, and in MALT (mucosa-associated lymphatic tissue)
2.stroma- a meshwork of fine reticular fibers embedded in a gelatinous tissue ground substance
3.parenchyma- a dense collection of leukacytes (WBC's) primarily T and B lymphocytes but also significant minority of monocyte-derived macrophages, and insignificant numbers of granulocytes; certain immunologically regions will be organized into follicles with pale germinal centers
4.vessels- the delicate thin-walled vascular tubes, lined with endo thelium and a very thin outer areolar connective tissue wrapping, which transport lymph from the tissue spaces back to the systemic circulation; some of the larger vessels have valves to prevent backflow; these vessels anastomose freely with one another; these vessels are inerrupted in various locations by lymph nodes
Explain how the lymphatic system functions to restore lost fluid from the circulatory system.
More fluid exits blood capillaries by diffusion than returns by reabsorption (Starling's Law of the Capillaries); approximately 3L of lymph is gerated per day. The lymphatic vessel drainage system recaptures this fluid and returns it to the systemic circulation along with its diddolved soolutes. The return is assisted by valves in many vessels preventing backflow; and by the muscular pump in the limbs and the respiratory pump in the thoracic cavity.
primary lymphatic organ
these organs in which lymphocytes are produced or in which they mature; in the human body, they are the red bone marrow and the thymus gland
red bone marrow
the type of marrow found in spongy bone and in the marrow cavities where the various blood stem cells reside and whre new red blood cells, white blood cells, and platelets are produced for release into the circulation
a lobed endocrine organ located in the mediastinum, deep to the sternum, which is responsible for the maturation of T lymphocytes; it produces a number of local hormones including thymosin to contribute to T lymphocyte maturation; the thymus is at its largest at birth and shinks over time, being replaced by fibrous connective tissue, adn is usually absent by the end of the second decade of life.
secondary lymphatic organ
those organs in which mature lymphocytes are found and where they play active roles in immune defense reactions; in human they include the red bone marrow, the lymph nodes, the spleen, the tonsils, and the various isolated microscopic lymphatic nodules, especially those found in the lamina propia of the mucous membranes of the GI tract, respiratory tract, urinary tract, and reproductive tract, ex. MALT
any of the small, discrete, encapsulated bodies (secondary lymphatic organs) locted along the lymphatic vessels, particularly at the neck, armpit, and groin, and in the thoracic and abdominal cavities, which receive lymph from the lymphatic circulation through afferent lymphatic vessels; they consist of a capsule, an outer cortex and inner medulla; they filter microorganisms and foreign particles from lymph fluid; they are also a frequent site of antigen-presentation and lymphocyte activation and proliferation; during infection, they may became swollen with activated lymphocytes. AKA-lymph glands
a large, dark-red, oval, highly vascular, fragile secondary lymphatic organ, located in the human body to the left of the stomach below the diaphragm, organized into areas of red pulp and white pulp;
functions of the spleen
it's functions include acting as a blood reservoir, phagocytizing old, worn, or damaged blood cells, filtering foreign substances from the blood, participating in immune defense and housing mature lymphocytes and macrophages
red pulp (of speen)
those portions of the spleen acting as a blood reservoir, organized into splenic cords (containing a meshwork of loose reticular connective tissue housing macrophages, lymphocytes, plasma cells, erythrocytes, platlets, and granulocytes) separated by endothelium lined capillary sinues(containing primarily macrophages and erythrocytes); the presence of large numbers of erythrocytes gives these portions of the spleen their distinctive red color; blood flow through these portions of the spleen in sluggish, but in hemorrhagic emergencies, smooth muscle in the splenic capsule can contract to expel this blood from this reservoir
white pulp (of the spleen)
Those portions of the spleen localized around the many small central arteries of the spleen; each central artery is surrounded by a thin layer of T lymphocytes while the surrounding reticular connective tissue is rich in lymphatic modules containing B and T lymphocytes; these lymphocytes are involved in immune defense; the absence of erythrocytes outside of the central arteries gives these portions of the spleen their distinctive white color
microscopic collections of unencapsulated, relatively sperical masses of dense aggregates of small B lymphocytes in an outer core and a central mass of antigen presenting macrophages and larger, more metabolically active, proleferating
B lymphocytes and plasma cells termed the germinal center; this is a site of proliferation and differentiation of lymphocytes in active immune responses; these structures are located in the walls of various organs, especially tubular organs lined by mucosal membranes
MALT (mucosa-associated lymphatic tissue)
the general term used for the various aggregations of lymphois tissue found associated with the mucous membranes of respiratory and digestive tracts; they consist of lymphatic nodules within the connective tissue walls of these tubular organs; these lymphocytes are involved in immune defenses
a secodary cancerous growth formed by transmission of cancerous cells from a primary growth(original site)to one or more sites elsewhere in the body, usually by way of blood vessels or lymphatics; the potential for metastasis is a characteristic of almost all malignant cancers
a malignant cancer; a progressive, sometimes fatal lymphoma of unknown cause, marked by progressive (but painless) enlargement of the lymph nodes, followed by enlargement of the spleen, and liver; bone marrow transplantation may be useful for selected patients who have relapsed following treatment with radiation and chemotherapy
list the forms of lymphatic tissue in the body 1. structural and 2. developmental and give examples
1. a.discrete, encapsulated lymphatic organs: thymus, lymph nodes, spleen
b. diffuse, unencapsulated lymphatic tissues: red bone marrow, MALT, isolated lymph nodules
2. a. primary lymphatic organs: those in which lymphocytes are produced or mature: red bone marrow, thymus gland
b. secondary lymphatic organs: those in which mature lymphocytes play active roles in immune defense reactions: red bone marroe, lymph nodes, spleen, tonsils, and various isolated microscopic lymphatic nodules, especially those found in the lamina propria of the mucous membranes of the GI tract, respiratory tract, urinary tract, and reproductive tract, EX. MALT
list the organs of the lymphatic sytem and the functions of each
1. red bone marrow-site of production of leukocytes, site of anti-self screening and maturation of B lymphocytes
2. lymph nodes-physical filtration of lymph, site of antigen-presentation between macrophages and lymphocytes, site of activation of specific clones of B and T lymphocytes
3. spleen-physical filtration of blood, site of removal and phagocytosis of aged and damaged blood cells, site of antigen-presentation between macrophages and lymphocytes, site of activation of specific clones of B and T lymphocytes
4. tonsils-site of antigen-presentation between macrophages and lymphocytes, site of activation of specific clones of B and T lymphocytes
5.MALT-site of antigen-presentation between macrophages and lymphocytes, site of activation of specific clones of B and T lymphocytes
6. thymus-site of anti-self screening and maturation of T lymphocytes
Name the sites where MALT lymphatic tissue is found
in the lamina propria of the mucous membranes of conjunctival sacs, GI tract, respiratory tract, urinary tract, and reproductive tract
Name the five tissues that do NOT contain lymph capillaries
1.any epithelial tissue
4.red bone marrow
How does lymphatic tissue vary in its distribution in various parts of the body?
Lymphatic tissue varies in distribution by being localized and concentrated in regions near potential invasion sites for microorganisms (in the lamin propria of the mucous membranes, and in lymph nodes along the lymphatic vessel drainage channels. There is also more lymphatic tissue in the head and trunk and less in the limbs.
How does lymphatic tissue vary in its organization in the body?
lymphatic tissue varies in its organization by either being 1.discrete, encapsulated lymphatic organs (thymus, lymph nodes, spleen) or 2.by being diffuse, unencapsulated lymphatic tissues (red bone marrow, MALT, isolated lymph nodules)