ch 20 ap

structure of a lymph node

-Bean shaped -External fibrous capsule -Two histologically distinct regions: -Cortex -Medulla

structure of a lymph node (cortex)

-Cortex contains follicles with germinal centers, many dividing B cells -Dendritic cells surround the follicles -Cortex houses T cells -T cells circulate continuously among the blood, lymph nodes, and lymphatic stream

spleen

-Largest lymphoid organ -Served by splenic artery and vein -Functions: -Site of lymphocyte proliferation, immune surveillance and response -Cleanses the blood of aged blood cells, platelets and debris -Stores breakdown products of RBCs (e.g., iron) for later reuse -Stores blood platelets -Site of fetal erythrocyte production (normally ceases after birth) -Contains lymphocytes, macrophages, and erythrocytes

circulation in the lymph nodes

-Lymph -Enters via afferent lymphatic vessels -Travels through sinuses -Exits the node at the hilus via efferent vessels -Fewer efferent vessels, causing flow of lymph to stagnate, allowing lymphocytes and macrophages time to carry out functions

structure of a lymph node (medulla)

-Medullary cords of medulla contain B cells, T cells, and plasma cells -Lymph sinuses contain macrophages

MALT

-Mucosa-associated lymphatic tissue, including -Peyer's patches, tonsils, and the appendix (digestive tract) -Lymphoid nodules in the walls of the bronchi (respiratory tract) -Protects the digestive and respiratory systems from foreign matter

Describe the source of lymph and mechanism(s) of lymph transport. What direction does lymph flow?

-One-way system, lymph flows toward the heart

aggregates of lymphoid follicles

-Peyer's patches -Clusters of lymphoid follicles -In the wall of the distal portion of the small intestine -Similar structures are also found in the appendix -Peyer's patches and the appendix -Destroy bacteria, preventing them from breaching the intestinal wall -Generate "memory" lymphocytes

lymph nodes

-Principal lymphoid organs of the body -Embedded in connective tissue, in clusters along lymphatic vessels -Near the body surface in inguinal, axillary, and cervical regions of the body -Functions: -Filter lymph—macrophages destroy microorganisms and debris -Immune system—lymphocytes are activated and mount an attack against antigens -Macrophages and lymphocytes are both found within the lymph nodes

lymphatic system functions

-Returns interstitial fluid and leaked plasma proteins back to the blood -Once interstitial fluid enters lymphatic vessels, it is called lymph -The organs, tissues and cells of the lymphatic system provide the structural basis of the immune system

tonsils

-Simplest lymphoid organs -Epithelial tissue overlying tonsils invaginates, forming tonsillar crypts -Crypts trap and destroy bacteria and particulate matter

lymphocytes

-Two types: -T cells (T lymphocytes) -B cells (B lymphocytes) -T cells -Manage the immune response -Attack and destroy foreign cells -B cells -Produce plasma cells, which secrete antibodies

thymus

-Varies in size with age -In infants, it is found in the inferior neck and extends into the mediastinum, where it partially overlies the heart -Increases in size and is most active during childhood -Stops growing during adolescence and then gradually atrophies -Thymus has an outer cortex and inner medulla -Cortex contains densely packed T lymphocytes and macrophages -Medulla contains thymic (Hassall's) corpuscles -Involved in destruction of T cells -Differs from other lymphoid organs in important ways -It functions strictly in T lymphocyte maturation -It does not directly fight antigens -The stroma of the thymus consists of epithelial cells (not reticular fibers) -These epithelial cells provide the environment in which T cells become immunocompetent

lymphatic capillaries

-act like drainpipes -Similar to blood capillaries, except: -Very permeable -Endothelial cells overlap to form one-way minivalves -Anchored by collagen filaments, preventing collapse of lymphatic capillaries

lymphatic collecting vessels

-collect lymph fluid draining from lymphatic capillaries -Similar to veins, except: -Have thinner walls, with more internal valves -Collecting vessels are found alongside arteries and veins -Lymph is propelled by -Pulsations of nearby arteries -Contractions of smooth muscle in the walls of the lymphatics

lymphatic trunks and ducts

-dump lymph back into blood -Lymph is delivered into one of two large ducts -Right lymphatic duct drains the right upper arm and the right side of the head and thorax -Thoracic duct arises from the cisterna chyli and drains the rest of the body -Each empties lymph into venous circulation at the junction of the internal jugular and subclavian veins on its own side of the body

hodgkins lymphoma

-giant malignant b cells Hodgkin's lymphoma is a malignancy of lymphoid tissue; symptoms include swollen, nonpainful lymph nodes, fatigue, and often intermittent fever and night sweats. Characterized by presence of giant malignantly transformed B cells called Reed-Sternberg cells.

macrophages

-phagocytize foreign substances and help activate T cells

dendritic cells

-process antigens and deliver them to immune cells

reticular cells

-produce stroma that supports other cells in lymphoid organs

3 parts of lymphatic system

1. Network of lymphatic vessels (lymphatics) 2. Lymph - fluid in vessels 3. Lymph cells, tissues, and organs

which of the following statements about the spleen is false

It is best to perform a splenectomy if the spleen is damaged in a car accident. -Because the spleen's capsule is relatively thin, a direct blow or severe infection may cause it to rupture, spilling blood into the peritoneal cavity. Once, splenectomy (surgical removal of the ruptured spleen) was the standard treatment and thought necessary to prevent life-threatening hemorrhage and shock. However, surgeons have discovered that, if left alone, the spleen can often repair itself and so the frequency of emergency splenectomies has decreased dramatically. If the spleen must be removed, the liver and bone marrow take over most of its functions. In children younger than 12, the spleen will regenerate if a small part of it is left in the body.

spleen

a filter and reservoir for the blood -The soft, blood-rich spleen is about the size of a fist and is the largest lymphoid organ. Located in the left side of the abdominal cavity just beneath the diaphragm, it curls around the anterior aspect of the stomach. It is served by the large splenic artery and vein, which enter and exit the hilum on its slightly concave anterior surface. The spleen provides a site for lymphocyte proliferation and immune surveillance and response. But perhaps even more important are its blood-cleansing functions. Besides extracting aged and defective blood cells and platelets from the blood, its macrophages remove debris and foreign matter. The spleen also performs three additional, and related, functions. The spleen: Recycles the breakdown products of red blood cells for later reuse. It releases the breakdown products to the blood for processing by the liver and stores some of the iron salvaged from hemoglobin. Stores blood platelets and monocytes for release into the blood when needed. May be a site of erythrocyte production in the fetus. The appendix is a tubular offshoot from the cecum. Lymph nodes are large collections of bean-shaped structures in the inguinal, axillary, and cervical regions. The thymus is where T cells become immunocompetent. The tonsils are lymphoid tissues that invite infection to promote immunity.

subcapsular sinus

a large, baglike structure leading into a number of small sinuses -Lymph enters the convex side of a lymph node through a number of afferent lymphatic vessels. It then moves through a large, baglike sinus, the subcapsular sinus, into a number of smaller sinuses that cut through the cortex and enter the medulla. The lymph meanders through these medullary sinuses and finally exits the node at its hilum, the indented region on the concave side, via efferent lymphatic vessels

which of the following best describes the arrangement of lymphatic vessels

a one-way system of vessels beginning with blind-ended lymphatic capillaries -The transport of lymph begins in microscopic blind-ended lymphatic capillaries. These capillaries weave between the tissue cells and blood capillaries in the loose connective tissues of the body. Lymphatic capillaries are widespread, but they are absent from bones and teeth, bone marrow, and most of the central nervous system (where the excess tissue fluid drains into the cerebrospinal fluid).

appendix

a tubular offshoot of the first part of the large intestine -The appendix is a tubular offshoot of the first part of the large intestine and contains a high concentration of lymphoid follicles. Like Peyer's patches, the appendix is in an ideal position (1) to prevent bacteria (present in large numbers in the intestine) from breaching the intestinal wall, and (2) to generate many "memory" lymphocytes for long-term immunity.

lymphoid tissue

a type of loose connective tissue called reticular connective tissue; dominates all lymphoid organs except the thymus -Lymphoid tissue is an important component of the immune system, mainly because it: Houses and provides a proliferation site for lymphocytes Furnishes an ideal surveillance vantage point for lymphocytes and macrophages Lymphoid tissue, largely composed of loose connective tissue called reticular connective tissue, dominates all the lymphoid organs except the thymus. Macrophages live on the fibers of the reticular connective tissue network. Huge numbers of lymphocytes squeeze through the walls of postcapillary venules coursing through this network. The lymphocytes temporarily occupy the spaces in the network before leaving to patrol the body again. The cycling of lymphocytes between the circulatory vessels, lymphoid tissues, and loose connective tissues of the body ensures that lymphocytes reach infected or damaged sites quickly.

which of the following lists the correct order of lymph flow through the lymph node

afferent vessels, subcapsular sinus, medullary sinuses, efferent vessels -Lymph enters the convex side of a lymph node through a number of afferent lymphatic vessels. It then moves through a large, baglike sinus, the subcapsular sinus, into a number of smaller sinuses that cut through the cortex and enter the medulla. The lymph meanders through these medullary sinuses and finally exits the node at its hilum, the indented region on the concave side, via efferent lymphatic vessels. There are fewer efferent vessels draining the node than afferent vessels feeding it, so the flow of lymph through the node stagnates somewhat, allowing time for the lymphocytes and macrophages to carry out their protective functions. Lymph passes through several nodes before it is completely cleansed.

lymphadenopathy

any disease of the lymph nodes

palatine tonsils

at posterior end of oral cavity

which of the following is the most abundant cell type found in the germinal center in a lymph node

b lymphocytes -Lymphoid follicles (lymphoid nodules) are solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers. Follicles often have lighter-staining germinal centers where proliferating B cells predominate. These centers enlarge dramatically when the B cells are dividing rapidly and producing plasma cells. In many cases, the follicles form part of larger lymphoid organs, such as lymph nodes.

lingual tonsils

base of tongue

which sequence best describes the flow of lymph through the lymphatic system

capillaries, vessels, trunks, ducts -The transport of lymph begins in microscopic blind-ended lymphatic capillaries. From the lymphatic capillaries, lymph flows through successively larger and thicker-walled channels—first collecting vessels, then trunks, and finally the largest of all, the ducts.

dendritic cell

captures antigens and brings them back to lymph nodes -Macrophages play a crucial role in body protection and the immune response by phagocytizing foreign substances and by helping to activate T cells. So, too, do the spiny-looking dendritic cells that capture antigens and bring them back to the lymph nodes. Reticular cells are fibroblast-like cells that produce reticular fibers that form the stroma of lymph nodes. Plasma cells (differentiated B cells) produce antibodies. Dendritic cells capture antigens and returns them to lymph nodes.

lymphatic vessels function

carry lymph from tissues back to the venous system

thymus

causes t cells to become immunocompetent -The bilobed thymus has important functions primarily during the early years of life. It is found in the inferior neck and extends into the superior thorax, where it partially overlies the heart deep to the sternum (see figures below). In the thymus, T lymphocyte precursors mature to become immunocompetent lymphocytes. In other words, the thymus is where T lymphocytes become able to defend us against specific pathogens in the immune response.

when is the thymus most active

childhood

in addition to providing a site for lymphocyte prolieration and immunne surveillance, the speen also functions to

cleanse the blood -The spleen provides a site for lymphocyte proliferation and immune surveillance and response. But perhaps even more important are its blood-cleansing functions. Besides extracting aged and defective blood cells and platelets from the blood, its macrophages remove debris and foreign matter. The spleen also performs three additional, and related, functions. The spleen: Recycles the breakdown products of red blood cells for later reuse. It releases the breakdown products to the blood for processing by the liver and stores some of the iron salvaged from hemoglobin. Stores blood platelets and monocytes for release into the blood when needed. May be a site of erythrocyte production in the fetus. T cells mature in the thymus, while B cells mature in the red bone marrow. Tonsils are lymphatic tissues that protect against pathogen invasion in the pharynx either in air or food.

lymphatic collecting vessels

collect lymph fluid draining from lymphatic capillaries -From the lymphatic capillaries, lymph flows through successively larger and thicker-walled channels—first collecting vessels, then trunks, and finally the largest of all, the ducts. The collecting lymphatic vessels have the same three tunics as veins, but the collecting vessels have thinner walls and more internal valves, and they anastomose more. In general, lymphatics in the skin travel along with superficial veins, while the deep lymphatic vessels of the trunk and digestive viscera travel with the deep arteries. The exact anatomical distribution of lymphatic vessels varies greatly between individuals, even more than it does for veins.

which of the following is not a function of lymphatic vessels

delivery of nutrients to tissues -As blood circulates through the body, nutrients, wastes, and gases are exchanged between the blood and the interstitial fluid. The hydrostatic and colloid osmotic pressures operating at capillary beds force fluid out of the blood at the arterial ends of the beds ("upstream") and cause most of it to be reabsorbed at the venous ends ("downstream"). The fluid that remains behind in the tissue spaces, as much as 3L daily, becomes part of the interstitial fluid. This leaked fluid, plus any plasma proteins that escape from the bloodstream, must somehow be returned to the blood to ensure that the cardiovascular system has sufficient blood volume. This problem of circulatory dynamics is resolved by the lymphatic vessels, or lymphatics, elaborate networks of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream. A special set of lymphatic capillaries called lacteals transports absorbed fat from the small intestine to the bloodstream. Lacteals are so called because of the milky white lymph that drains through them (lact = milk). This fatty lymph, called chyle ("juice"), drains from the fingerlike villi of the intestinal mucosa.

lymph nodes

distinct bean-shaped structures that "filter" lymph fluid as it is moved toward the circulatory system -The structure of a lymph node supports its defensive functions. Lymph nodes vary in shape and size, but most are bean shaped and less than 2.5 cm (1 inch) in length. Each node is surrounded by a dense fibrous capsule from which connective tissue strands called trabeculae extend inward to divide the node into a number of compartments. The node's internal framework, or stroma, of reticular fibers physically supports its ever-changing population of lymphocytes.

right lymphatic duct

drains right side of the head, upper limb, and neck region -Lymph is eventually delivered to one of two large ducts in the thoracic region. The right lymphatic duct drains lymph from the right upper limb and the right side of the head and thorax. The much larger thoracic duct receives lymph from the rest of the body. It collects lymph from the two large lumbar trunks that drain the lower limbs and from the intestinal trunk that drains the digestive organs. In about half of individuals, the thoracic duct begins as an enlarged sac, the cisterna chyli, located in the region between the last thoracic and second lumbar vertebrae. As the thoracic duct runs superiorly, it receives lymphatic drainage from the left side of the thorax, left upper limb, and the left side of the head. Each terminal duct empties its lymph into the venous circulation at the junction of the internal jugular vein and subclavian vein on its own side of the body.

reticular cell

fibroblast-like cell that produces the reticular fiber stroma -Reticular cells are fibroblast-like cells that produce the reticular fiber stroma, which is the network that supports the other cell types in lymphoid organs and tissues.

the main role of the tonsils is to

gather and remove pathogens entering through the pharynx -The lymphoid tissue of the tonsils contains follicles with obvious germinal centers surrounded by diffusely scattered lymphocytes. The tonsils are not fully encapsulated, and the epithelium overlying them invaginates deep into their interior, forming blind-ended tonsillar crypts. The crypts trap bacteria and particulate matter, and the bacteria work their way through the mucosal epithelium into the lymphoid tissue, where most are destroyed. It seems a bit dangerous to "invite" infection this way, but this strategy produces a wide variety of immune cells that have a "memory" for the trapped pathogens. In other words, the body takes a calculated risk early on (during childhood) for the benefits of heightened immunity and better health later.

what statement is true of the thoracic duct

it drains the lymph from the entire left side of the body and also the right abdomen and legs -Lymph is eventually delivered to one of two large ducts in the thoracic region. The right lymphatic duct drains lymph from the right upper limb and the right side of the head and thorax. The much larger thoracic duct receives lymph from the rest of the body. It collects lymph from the two large lumbar trunks that drain the lower limbs and from the intestinal trunk that drains the digestive organs. In about half of individuals, the thoracic duct begins as an enlarged sac, the cisterna chyli, located in the region between the last thoracic and second lumbar vertebrae. As the thoracic duct runs superiorly, it receives lymphatic drainage from the left side of the thorax, left upper limb, and the left side of the head. Each terminal duct empties its lymph into the venous circulation at the junction of the internal jugular vein and subclavian vein on its own side of the body.

which statement below describes the lymphatic system's role in relation to the cardiovascular system

it maintain's blood volume, and hence, pressure -As blood circulates through the body, nutrients, wastes, and gases are exchanged between the blood and the interstitial fluid. The hydrostatic and colloid osmotic pressures operating at capillary beds force fluid out of the blood at the arterial ends of the beds ("upstream") and cause most of it to be reabsorbed at the venous ends ("downstream"). The fluid that remains behind in the tissue spaces, as much as 3 L daily, becomes part of the interstitial fluid. This leaked fluid, plus any plasma proteins that escape from the bloodstream, must somehow be returned to the blood to ensure that the cardiovascular system has sufficient blood volume. This problem of circulatory dynamics is resolved by the lymphatic vessels, or lymphatics, elaborate networks of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream.

what lymphatic structure absorbs lipids in the intestine

lacteal -A special set of lymphatic capillaries called lacteals transports absorbed fat from the small intestine to the bloodstream. Lacteals are so called because of the milky white lymph that drains through them (lact = milk). This fatty lymph, called chyle ("juice"), drains from the fingerlike villi of the intestinal mucosa.

lymphatic ducts

largest vessels; carry lymph fluid to subclavian veins -Lymph is eventually delivered to one of two large ducts in the thoracic region. The right lymphatic duct drains lymph from the right upper limb and the right side of the head and thorax. The much larger thoracic duct receives lymph from the rest of the body. It collects lymph from the two large lumbar trunks that drain the lower limbs and from the intestinal trunk that drains the digestive organs. In about half of individuals, the thoracic duct begins as an enlarged sac, the cisterna chyli (sis-ter'nah ki'li), located in the region between the last thoracic and second lumbar vertebrae. As the thoracic duct runs superiorly, it receives lymphatic drainage from the left side of the thorax, left upper limb, and the left side of the head. Each terminal duct empties its lymph into the venous circulation at the junction of the internal jugular vein and subclavian vein on its own side of the body.

thymus gland

located in the inferior neck and extends into the superior thorax -The bilobed thymus has important functions primarily during the early years of life. It is found in the inferior neck and extends into the superior thorax, where it partially overlies the heart deep to the sternum (see figures below). In the thymus, T lymphocyte precursors mature to become immunocompetent lymphocytes. In other words, the thymus is where T lymphocytes become able to defend us against specific pathogens in the immune response.

select the lymphoid organ that cleanses the lymph

lymph nodes -Although all lymphoid organs help protect the body, only the lymph nodes cleanse the lymph. The other secondary lymphoid organs typically have efferent lymphatics draining them, but lack afferent lymphatics.

which of the following is not a characteristic of lymph nodes

lymph nodes produce lymph -Lymphatic vessels, or lymphatics, are elaborate networks of drainage vessels that collect excess protein-containing interstitial fluid and return it to the bloodstream. Once interstitial fluid enters the lymphatic vessels, it is called lymph (lymph = clear water). The most important of the secondary lymphoid organs in the body are the lymph nodes, which cluster along the lymphatic vessels of the body. There are hundreds of these small organs, but because they are usually embedded in connective tissue, they are not ordinarily visible. Large clusters of lymph nodes occur near the body surface in the inguinal, axillary, and cervical regions, places where the collecting lymphatic vessels converge to form trunks. Lymph nodes have two basic protective functions: Cleansing the lymph. As lymph is transported back to the bloodstream, the lymph nodes act as lymph "filters." Macrophages in the nodes remove and destroy microorganisms and other debris that enter the lymph from the loose connective tissues, preventing them from being delivered to the blood and spreading to other parts of the body. Immune system activation. Lymph nodes and other lymphoid organs are strategically located sites where lymphocytes encounter antigens and are activated to mount an attack against them.

large lymphatic capillaries in a lymph node spanned by crisscrossing reticular fibers are known as

lymph sinuses -Throughout the lymph node are lymph sinuses. These sinuses are large lymphatic capillaries spanned by crisscrossing reticular fibers. Numerous macrophages reside on these reticular fibers and phagocytize foreign matter in the lymph as it flows by in the sinuses. Additionally, some of the lymph-borne antigens in the percolating lymph leak into the surrounding lymphoid tissue, where they activate lymphocytes to mount an immune attack against them.

which part of the lymphatic system is most closely related to capillary beds

lymphatic capillaries -The transport of lymph begins in microscopic blind-ended lymphatic capillaries. From the lymphatic capillaries, lymph flows through successively larger and thicker-walled channels—first collecting vessels, then trunks, and finally the largest of all, the ducts. These capillaries weave between the tissue cells and blood capillaries in the loose connective tissues of the body. Lymphatic capillaries are widespread, but they are absent from bones and teeth, bone marrow, and most of the central nervous system (where the excess tissue fluid drains into the cerebrospinal fluid). Although similar to blood capillaries, lymphatic capillaries are so remarkably permeable that they were once thought to be open at one end like a straw.

how are lymphatic capillaries different from blood capillaries

lymphatic capillaries have endothelial flap valves, but blood capillaries do not -Although similar to blood capillaries, lymphatic capillaries are so remarkably permeable that they were once thought to be open at one end like a straw. We now know that they owe their permeability to two unique structural modifications: The endothelial cells forming the walls of lymphatic capillaries are not tightly joined. Instead, the edges of adjacent cells overlap each other loosely, forming easily opened, flaplike minivalves. Collagen filaments anchor the endothelial cells to surrounding structures so that any increase in interstitial fluid volume opens the minivalves, rather than causing the lymphatic capillaries to collapse.

which of the following vessels transport fluid back into the blood that leaks from the vascular system

lymphatics -As blood circulates through the body, nutrients, wastes, and gases are exchanged between the blood and the interstitial fluid. The hydrostatic and colloid osmotic pressures operating at capillary beds force fluid out of the blood at the arterial ends of the beds ("upstream") and cause most of it to be reabsorbed at the venous ends ("downstream"). The fluid that remains behind in the tissue spaces, as much as 3L daily, becomes part of the interstitial fluid. This leaked fluid, plus any plasma proteins that escape from the bloodstream, must somehow be returned to the blood to ensure that the cardiovascular system has sufficient blood volume. This problem of circulatory dynamics is resolved by the lymphatic vessels, or lymphatics, elaborate networks of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream.

tumors that block the lymphatics or lymphatics are removed during cancer surgery may result in what condition

lymphedema -Anything that prevents the normal return of lymph to the blood—such as when tumors block the lymphatics or lymphatics are removed during cancer surgery—results in shortterm but severe localized edema (lymphedema). In some cases, the lymphedema improves if some lymphatic pathways remain and can enlarge.

which of the following are located in the spleen's white pulp

lymphocytes -Like lymph nodes, the spleen is surrounded by a fibrous capsule and has trabeculae that extend inward. Histologically, the spleen consists of two components: white pulp and red pulp. White pulp is where immune functions take place, so it is composed mostly of lymphocytes suspended on reticular fibers. The white pulp clusters or forms "cuffs" around central arteries (small branches of the splenic artery). These clusters of white pulp look like islands in a sea of red pulp.

tonsils

lymphoid organs; found around the entrance to the pharynx -The lymphoid tissue of the tonsils contains follicles with obvious germinal centers surrounded by diffusely scattered lymphocytes. The tonsils are not fully encapsulated, and the epithelium overlying them invaginates deep into their interior, forming blind-ended tonsillar crypts. The crypts trap bacteria and particulate matter, and the bacteria work their way through the mucosal epithelium into the lymphoid tissue, where most are destroyed. It seems a bit dangerous to "invite" infection this way, but this strategy produces a wide variety of immune cells that have a "memory" for the trapped pathogens. In other words, the body takes a calculated risk early on (during childhood) for the benefits of heightened immunity and better health later.

MALT

mucosa-associated lymphoid tissue small lymphoid tissues found in digestive and respiratory tracts -Mucosa-associated lymphoid tissues (MALT) are a set of distributed lymphoid tissues strategically located in mucous membranes throughout the body. MALT helps protect us from the never-ending onslaught of pathogens that seek to enter our bodies. The largest collections of MALT are in the tonsils, Peyer's patches, and appendix. In addition to these large named collections, MALT also occurs in the mucosa of the respiratory and genitourinary organs as well as the rest of the digestive tract. The spleen is a soft, blood-rich organ about the size of a fist and is the largest lymphoid organ. They thymus is located in the inferior neck and extends into the superior thorax. Tonsils are lymphoid tissues found in the pharynx. Peyer's patches are isolated clusters of lymph follicles located mostly in the wall of the distal small intestine.

what lymphatic structures trap bacteria in the posterior oral cavity

palatine tonsils -The tonsils form a ring of lymphoid tissue around the entrance to the pharynx (throat), where they appear as swellings of the mucosa (figure below). The tonsils are named according to location. The paired palatine tonsils are located on either side at the posterior end of the oral cavity. These are the largest tonsils and the ones most often infected. The lingual tonsil is the collective term for a lumpy collection of lymphoid follicles at the base of the tongue. The pharyngeal tonsil (referred to as the adenoids if enlarged) is in the posterior wall of the nasopharynx. The tiny tubal tonsils surround the openings of the auditory tubes into the pharynx. The tonsils gather and remove many of the pathogens entering the pharynx in food or in inhaled air.

aggregates of lymphoid nodules located in the wall of the ileum of the small intestine are

peyers patches -Peyer's patches, or aggregated lymphoid nodules, are large clusters of lymphoid follicles, structurally similar to the tonsils. They are located in the wall of the distal portion of the small intestine.

pharyngeal tonsil

posterior wall of nasopharynx

thoracic duct

receives lymph from all but the right upper limb and right side of the head and thorax -Lymph is eventually delivered to one of two large ducts in the thoracic region. The right lymphatic duct drains lymph from the right upper limb and the right side of the head and thorax. The much larger thoracic duct receives lymph from the rest of the body. It collects lymph from the two large lumbar trunks that drain the lower limbs and from the intestinal trunk that drains the digestive organs. In about half of individuals, the thoracic duct begins as an enlarged sac, the cisterna chyli, located in the region between the last thoracic and second lumbar vertebrae. As the thoracic duct runs superiorly, it receives lymphatic drainage from the left side of the thorax, left upper limb, and the left side of the head. Each terminal duct empties its lymph into the venous circulation at the junction of the internal jugular vein and subclavian vein on its own side of the body.

lymphangitis presents itself as

red lines under the skin that are sensitive to touch -Like the larger blood vessels, the larger lymphatics receive their nutrient blood supply from a branching vasa vasorum. When lymphatic vessels are severely inflamed, the related vessels of the vasa vasorum become congested with blood. As a result, the pathway of the associated superficial lymphatics becomes visible through the skin as red lines that are tender to the touch. This unpleasant condition is called lymphangitis.

the lymphoid tissues structural framework is composed of

reticular connective tissue -Reticular cells are fibroblast-like cells that produce the reticular fiber stroma, which is the network that supports the other cell types in lymphoid organs and tissues.

a major function of the lymphatic system is

return of tissue fluid to the cardiovascular system -As blood circulates through the body, nutrients, wastes, and gases are exchanged between the blood and the interstitial fluid. The hydrostatic and colloid osmotic pressures operating at capillary beds force fluid out of the blood at the arterial ends of the beds ("upstream") and cause most of it to be reabsorbed at the venous ends ("downstream"). The fluid that remains behind in the tissue spaces, as much as 3L daily, becomes part of the interstitial fluid. This leaked fluid, plus any plasma proteins that escape from the bloodstream, must somehow be returned to the blood to ensure that the cardiovascular system has sufficient blood volume. This problem of circulatory dynamics is resolved by the lymphatic vessels, or lymphatics, elaborate networks of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream.

collecting lymphatic vessels

same three tunics as veins, the second smallest lymph vessels -From the lymphatic capillaries, lymph flows through successively larger and thicker-walled channels—first collecting vessels, then trunks, and finally the largest of all, the ducts. The collecting lymphatic vessels have the same three tunics as veins, but the collecting vessels have thinner walls and more internal valves, and they anastomose more. In general, lymphatics in the skin travel along with superficial veins, while the deep lymphatic vessels of the trunk and digestive viscera travel with the deep arteries. The exact anatomical distribution of lymphatic vessels varies greatly between individuals, even more than it does for veins.

which of the following is not a role of the spleen

serves as a site for t cell maturation -The primary lymphoid organs are where B and T cells mature—the red bone marrow and the thymus. While both B and T cells originate in the red bone marrow, B cells mature in the red bone marrow and T cells mature in the thymus. The spleen provides a site for lymphocyte proliferation and immune surveillance and response. But perhaps even more important are its blood-cleansing functions. Besides extracting aged and defective blood cells and platelets from the blood, its macrophages remove debris and foreign matter. The spleen also performs three additional, and related, functions. The spleen: Recycles the breakdown products of red blood cells for later reuse. It releases the breakdown products to the blood for processing by the liver and stores some of the iron salvaged from hemoglobin. Stores blood platelets and monocytes for release into the blood when needed. May be a site of erythrocyte production in the fetus.

lymphatic capillary

smallest lymphatic vessel that collects excess tissue fluid -The transport of lymph begins in microscopic blind-ended lymphatic capillaries. These capillaries weave between the tissue cells and blood capillaries in the loose connective tissues of the body. Lymphatic capillaries are widespread, but they are absent from bones and teeth, bone marrow, and most of the central nervous system (where the excess tissue fluid drains into the cerebrospinal fluid). As blood circulates through the body, nutrients, wastes, and gases are exchanged between the blood and the interstitial fluid. The hydrostatic and colloid osmotic pressures operating at capillary beds force fluid out of the blood at the arterial ends of the beds ("upstream") and cause most of it to be reabsorbed at the venous ends ("downstream"). The fluid that remains behind in the tissue spaces, as much as 3L daily, becomes part of the interstitial fluid. This leaked fluid, plus any plasma proteins that escape from the bloodstream, must somehow be returned to the blood to ensure that the cardiovascular system has sufficient blood volume. This problem of circulatory dynamics is resolved by the lymphatic vessels, or lymphatics, elaborate networks of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream.

in addition to its lymphoid function, this organ holds a reservoir of platelets

spleen

which lymphatic structure may also be a site of erythrocyte production in the fetus

spleen -The soft, blood-rich spleen is about the size of a fist and is the largest lymphoid organ. Located in the left side of the abdominal cavity just beneath the diaphragm, it curls around the anterior aspect of the stomach. It is served by the large splenic artery and vein, which enter and exit the hilum on its slightly concave anterior surface. The spleen provides a site for lymphocyte proliferation and immune surveillance and response. But perhaps even more important are its blood-cleansing functions. Besides extracting aged and defective blood cells and platelets from the blood, its macrophages remove debris and foreign matter. The spleen also performs three additional, and related, functions. The spleen: Recycles the breakdown products of red blood cells for later reuse. It releases the breakdown products to the blood for processing by the liver and stores some of the iron salvaged from hemoglobin. Stores blood platelets and monocytes for release into the blood when needed. May be a site of erythrocyte production in the fetus.

what blood vessels serve the spleen

splenic artery and vein -The splenic artery and vein enter and exit, respectively, the hilum of the spleen on the slightly concave anterior surface.

tubal tonsils

surround the openings of the auditory tubes into the pharynx

which of the following is a common way to distinguish an infection from cancerous growth in the lymph nodes

swelling due to cancer is often painless -Lymph nodes can also become secondary cancer sites, particularly when metastasizing cancer cells enter lymphatic vessels and become trapped there. Cancer-infiltrated lymph nodes are swollen but usually not painful, a fact that helps distinguish cancerous nodes from those infected by microorganisms.

the bubonic plague was named for what condition

swollen lymph nodes -Sometimes lymph nodes are overwhelmed by the agents they are trying to destroy. For example, when large numbers of bacteria are trapped in the nodes, the nodes become inflamed, swollen, and tender to the touch, a condition often referred to (erroneously) as swollen "glands." Such infected lymph nodes (often pus-filled) are called buboes. (The bubonic plague was named for these buboes.)

lymphocytes that develop immunocompetence in the thymus are

t lymphocytes -The bilobed thymus has important functions primarily during the early years of life. It is found in the inferior neck and extends into the superior thorax, where it partially overlies the heart deep to the sternum. In the thymus, T lymphocyte precursors mature to become immunocompetent lymphocytes. In other words, the thymus is where T lymphocytes become able to defend us against specific pathogens in the immune response.

a sentinel node is the first lymph node

that receives lymph drainage from a body area suspected of cancer -When examined for presence of cancer cells, sentinel lymph nodes give the best indication of whether metastasis of cancer cells through the lymphatic vessels has occurred.

hilum

the indented region on the concave side of the node leading into the efferent vessels -Lymph enters the convex side of a lymph node through a number of afferent lymphatic vessels. It then moves through a large, baglike sinus, the subcapsular sinus, into a number of smaller sinuses that cut through the cortex and enter the medulla. The lymph meanders through these medullary sinuses and finally exits the node at its hilum, the indented region on the concave side, via efferent lymphatic vessels.

which of the following is not a part of the mucosa-associated lymphoid tissue (MALT)

the spleen -Mucosa-associated lymphoid tissues (MALT) are a set of distributed lymphoid tissues strategically located in mucous membranes throughout the body. MALT helps protect us from the never-ending onslaught of pathogens that seek to enter our bodies. The largest collections of MALT are in the tonsils, Peyer's patches, and appendix.

the lymphoid organ(s) located in the throat that defend(s) against invading bacteria coming in through the mouth and nose is (are)

the tonsils -The lymphoid tissue of the tonsils contains follicles with obvious germinal centers surrounded by diffusely scattered lymphocytes. The tonsils are not fully encapsulated, and the epithelium overlying them invaginates deep into their interior, forming blind-ended tonsillar crypts. The crypts trap bacteria and particulate matter, and the bacteria work their way through the mucosal epithelium into the lymphoid tissue, where most are destroyed. It seems a bit dangerous to "invite" infection this way, but this strategy produces a wide variety of immune cells that have a "memory" for the trapped pathogens. In other words, the body takes a calculated risk early on (during childhood) for the benefits of heightened immunity and better health later.

which statement is true about lymph nodes

they have fewer efferent vessels than afferent vessels -There are fewer efferent vessels draining the node than afferent vessels feeding it, so the flow of lymph through the node stagnates somewhat, allowing time for the lymphocytes and macrophages to carry out their protective functions. Lymph passes through several nodes before it is completely cleansed.

collections of lymphoid tissue (MALT) that guard mucosal surfaces include all the following, except

thymus -Mucosa-associated lymphoid tissues (MALT) are a set of distributed lymphoid tissues strategically located in mucous membranes throughout the body. MALT helps protect us from the never-ending onslaught of pathogens that seek to enter our bodies. The largest collections of MALT are in the tonsils, Peyer's patches, and appendix. In addition to these large named collections, MALT also occurs in the mucosa of the respiratory and genitourinary organs as well as the rest of the digestive tract.

which organs of the lymphatic system might be difficult to identify on a cadaver image of an elderly individual

thymus -Prominent in newborns, the thymus continues to increase in size during the first year, when it is highly active. After puberty, it gradually atrophies and by old age it has been replaced almost entirely by fibrous and fatty tissue and is difficult to distinguish from surrounding connective tissue. Even though it atrophies, the thymus continues to produce immunocompetent cells as we age, although at a declining rate.

which of the following is the major lymphoid organ that "trains" T lymphocytes to become immunocompetent

thymus -The bilobed thymus has important functions primarily during the early years of life. It is found in the inferior neck and extends into the superior thorax, where it partially overlies the heart deep to the sternum. In the thymus, T lymphocyte precursors mature to become immunocompetent lymphocytes. In other words, the thymus is where T lymphocytes become able to defend us against specific pathogens in the immune response.

which of the following features is not common to both lymphatic vessels and veins

trasnport of chyle -A special set of lymphatic capillaries called lacteals transports absorbed fat from the small intestine to the bloodstream. Lacteals are so called because of the milky white lymph that drains through them (lact = milk). This fatty lymph, called chyle ("juice"), drains from the fingerlike villi of the intestinal mucosa.

elephantiasis

tropical disease in which the lymphatics become blocked -Elephantiasis is typically a tropical disease in which the lymphatics (particularly those of the lower limbs and scrotum) become clogged with parasitic roundworms, an infectious condition called filariasis. Swelling (due to edema) reaches enormous proportions.

splenomegaly

typically caused by septicemia, mononucleosis, malaria, or leukemia

non-hodgkins lymphoma

uncontrolled multiplication and metastasis of undifferentiated lymphocytes

afferent lymphatic vessels

vessels leading into lymph node -Lymph enters the convex side of a lymph node through a number of afferent lymphatic vessels. It then moves through a large, baglike sinus, the subcapsular sinus, into a number of smaller sinuses that cut through the cortex and enter the medulla. The lymph meanders through these medullary sinuses and finally exits the node at its hilum, the indented region on the concave side, via efferent lymphatic vessels. There are fewer efferent vessels draining the node than afferent vessels feeding it, so the flow of lymph through the node stagnates somewhat, allowing time for the lymphocytes and macrophages to carry out their protective functions. Lymph passes through several nodes before it is completely cleansed.

efferent lymphatic vessels

vessels leaving the lymph node -Lymph enters the convex side of a lymph node through a number of afferent lymphatic vessels. It then moves through a large, baglike sinus, the subcapsular sinus, into a number of smaller sinuses that cut through the cortex and enter the medulla. The lymph meanders through these medullary sinuses and finally exits the node at its hilum, the indented region on the concave side, via efferent lymphatic vessels. There are fewer efferent vessels draining the node than afferent vessels feeding it, so the flow of lymph through the node stagnates somewhat, allowing time for the lymphocytes and macrophages to carry out their protective functions. Lymph passes through several nodes before it is completely cleansed.

areas of lymphocytes suspended by reticular fibers in the spleen are known as

white pulp -White pulp is where immune functions take place, so it is composed mostly of lymphocytes suspended on reticular fibers. The white pulp clusters or forms "cuffs" around central arteries (small branches of the splenic artery). These clusters of white pulp look like islands in a sea of red pulp.