The Lymphatic System

Diffuse lymphoid tissue

A loose arrangement of lymphoid cells and some reticular fibers-is found in virtually every body organ. Larger collections appear in the lamina propria of mucous membranes (digestive tract).

Pharyngeal tonsil

ADNEOIDS, is in the posterior wall of the nasopharynx.

Circulation in the Lymph Nodes

Afferent lymphatic vessels Subcapsular sinus Medullary sinuses Hilum Efferent lymphatic vessels

Lymph

Once interstitial fluid enters the lymphatic vessels

Palatine tonsils

Paired, located on either side at the posterior end of the oral cavity. Largest tonsils and most often infected.

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

Peyer's patches prevent bacteria from migrating through the wall of the intestine.

Tubal tonsils

Surround the openings of the auditory tubes into the pharynx.

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

T cells develop in the thymus.

What is the predominant cell type in the cortical regions other than germinal centers?

T lymphocytes

T cells

T lymphocytes Manage the immune response, and some of them directly attack and destroy infected cells.

Reticular cells

fibroblast-like cells that form the stroma or framework of the lymphoid organs

Reticular cells

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

Tonsils

form a ring of lymphoid tissue around the entrance to the pharynx where they appear as swellings of the mucosa.

When B lymphocytes are dividing rapidly, the __________ of the lymphoid tissue enlarge(s).

germinal centers When B lymphocytes are dividing rapidly, the germinal centers of the lymphoid tissue enlarge.

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.

T lymphocytes precursors mature to become

immunocomptent lymphocytes, the thymus is where T lymphocytes become able to defend us against specific pathogens in the immune reponse.

Where are plasma cells found in a lymph node?

in the medullary cords Plasma cells are found in the medullary cords of the lymph node.

Buboes

infected lymph nodes, pus-filled

After puberty

it 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.

When the pressure is greater inside the lymphatic capillary

it forces the endothelial minivalve flaps shut, preventing lymph from leaking back out as the pressure moves it along the vessel.

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.

What lymphatic structure absorbs lipids in the intestine?

lacteal

Lymphocytes

main warriors of the immune system

Which of the following cells would NOT be found in a germinal center in a lymph node?

monocytes Monocytes are not found in a germinal center in a lymph node.

When lymphoid tissue is tightly packed into spherical masses, the arrangement is said to be

nodular or follicular

Thymic lobules

outer cortex and inner medulla

What lymphatic structures trap bacteria in the posterior oral cavity?

palatine tonsils

Macrophages act as

phagocytes

Macrophages

play a crucial role in body protection and the immune response by phagocytizing foreign substances and by helping activate T cells.

How does the thymus differ from the secondary lymphoid organs? 3 IMPORTANT WAYS

1. Has no follicles because it lacks B cells. 2. Does not directly fight antigens. Functions as a maturation site for T lymphocyte precursors-must be kept isolated from foreign antigens to prevent their premature activation. Blood thymus barrier-keeps bloodborne antigens out of the thymus. 3. The stroma of the thymus consists of epithelial cells rather than reticular fibers. They provide the physical and chemical environment in which T lymphocytes mature.

Why is lymphoid tissue an important component of the immune system?

1. Houses and provides proliferation site for lymphocytes. 2. Furnishes an ideal surveillance vantage point for lymphocytes and macrophages.

Spleen functions

1. 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. 2. Stores blood platelets and monocytes for release into the blood when needed. 3. May be a site of erythrocyte production in the fetus.

Structural modifications of lymphatic capillaries

1. The endothelial cells forming the walls of lymphatic capillaries are not tightly joined. The edges of adjacent cells overlap each other loosely, forming easily opened, flaplike MINIVALVES. 2. Collagen filaments anchor endothelial cells to surrounding structures so that any increase in interstitial fluid volume opens the minivalves, rather than causing the lymphatic capillaries to collapse.

Primary lymphoid organs

B and T cells mature-red bone marrow and thymus.

Which cell is found in the greatest abundance in the germinal centers?

B lymphocytes

B cells

B lymphocytes Protect the body by producing plasma cells, daughter cells that secrete antibodies into the blood.

Lymph nodes size and shape

Bean shaped and less than 2.5 cm in length

Lymph sacs

By the 5th week of embryonic development, the beginnings of the lymphatic vessels and the main lymph node clusters are apparent. These arise as LYMPH SACS that bud from developing veins and from a branching system of lymphatic vessels throughout the thorax, upper extremities, and head.

The largest collection of lymph nodes are found in what three body regions?

Cervical Axillary Inguinal

Thymic corpuscles

Consisting of concentric whorls of keratinized epithelial cells, site of T cell destruction. Involved in the development of regulatory T cells-preventing autoimmune responses.

Lymphatic vessels or Lymphatics

Elaborate networks of drainage vessels that collect the excess protein-containing interstitial fluid and return it to the bloodstream.

Excess tissue fluid in the brain drains into the

Excess tissue fluid in the brain drains into the CSF.

Blood cleansing functions of the spleen

Extracting aged and defective blood cells and platelets from the blood, macrophages remove debris and foreign matter.

Cleansing the 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.

Thymus

Found in the inferior neck and extends into the superior thorax, partially overlies the heart deep to the sternum.

Where proliferating B cells predominate

Germinal centers, they enlarge when the B cells are dividing rapidly and producing plasma cells.

Mucosa-associated lymphoid tissues (MALT)

Helps protect us from the neverending onslaught of pathogens that seek into our bodies. Tonsils, Peyer's patches, appendix, mucosa of the respiratory, genitourinary organs, rest of the digestive tract.

Spleen

Is about the size of a fist and is the LARGEST lymphoid organ. In the left side of the abdominal cavity just beneath the diaphragm, curls around the anterior aspect of the stomach. Served by the large splenic artery and vein, which enters and exits the HILUM.

Which statement is true of the thoracic duct?

It drains the lymph from the entire left side of the body and the right abdomen and leg. The thoracic duct drains its lymph at the junction of the left internal jugular and subclavian veins.

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. Twenty years ago, it was common practice to remove the spleen if it was damaged. This is now contraindicated, because it has been shown that the spleen can heal itself.

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

It maintains blood volume and, hence, pressure. As much as 3 liters of lymph must be returned to the blood volume each day.

Peyer's patches or aggregated lymphoid nodules

Large clusters of lymphoid follicles, walls of the distal portion of the small intestine.

Major trunks

Lumbar Bronchomediastinal Subclavian Jugular trunks Intestinal trunk

Lingual tonsil

Lumpy collective term for a lumpy collection of lymphoid follicles at the base of the tongue.

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.

Lymphangitis

Lymphatic vessels are severely inflamed, the related vessels of the vasa vasorum become congested with blood. Superficial lymphatics becomes visible through the skin as red lines that are tender to the touch.

Lymphatic capillaries exhibit unique junctions between their endothelial cells, and they are anchored to surrounding tissues by fine filaments. How do these structural modifications aid in their function?

Lymphatic vessels pick up fluid leaked from the cardiovascular system. The overlapping edges of the endothelial cells form minivalves that allow fluid to enter, but not leave the lymph capillaries. When the interstitial pressure rises, gaps are exposed between the endothelial flaps, and fluid enters. Collapse of the vessel is prevented by fine filaments that anchor the lymph capillaries to surrounding tissues.

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

Lymphatics transport fluid that leaks from the vascular system back into the blood

Which of the following are located in the spleen's white pulp?

Lymphocytes are located in the white pulp.

Reticular connective tissue

Lymphoid tissue, dominates all the lymphoid organs except the thymus. Macrophages live on the fibers of the reticular connective tissue network.

Lymph nodes

MOST IMPORTANT secondary lymphoid organ. 100's of small organs, not visible because embedded in connective tissue.

Lymphoid organs and tissues

Provide the structural basis of the immune system. Play essential roles in the body's defense mechanisms and its resistance to disease. Spleen, thymus, tonsils, other lymphoid tissues, lymph nodes.

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.

Lymphatic trunks

The largest collecting vessels unite to form LYMPHATIC TRUNKS, which drain fairly large areas of the body.

Lymph transport

The milking action of active skeletal muscles, pressure changes in the thorax during breathing, and valves to prevent backflow. Lymphatic vessels are bundled together in connective tissue sheaths along with blood vessels, and pulsations of nearby arteries also promote lymph flow.

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

The spleen holds a reservoir of platelets; it also removes old and damaged red blood cells.

Cisterna chyli

The thoracic duct begins as an enlarged sac, located between the last thoracic and second lumbar vertebrae.

Lymphatic capillaries

The transport of lymph begins in microscopic blind-ended LYMPHATIC CAPILLARIES. They weave between the tissue cells and blood capillaries in the loose connective tissues of the body. Widespread but absent from bones and teeth, bone marrow, and the entire central nervous system.

What is the general function of lymph nodes?

They act to protect the body by removing bacteria or other debris from the lymphatic system.

Which statement is true about lymph nodes?

They have fewer efferent vessels than afferent vessels. They have fewer efferent vessels than afferent vessels. This slows the flow of the lymph through the node.

What is the function of their daughter cells, the plasma cells?

They produce and release antibodies.

This structure, attached to the cecum, is in an ideal location to destroy bacteria before they breach the intestinal wall.

This appendix extends from the cecum.

Of what importance is the fact that there are fewer efferent than afferent lymphatics associated with lymph nodes?

This slows the flow of lymph through the node, allowing time for immune cells and macrophages to respond to foreign substances present in the lymph.

Lacteals

Transports absorbed fat from the small intestine to the bloodstream. Milky white lymph that drains through them. CHYLE drains from the fingerlike villi of the intestinal mucosa.

Each node is surrounded by

a dense fibrous CAPSULE from which connective tissue stands called TRABECULAE extend inward to divide the node into a number of compartments.

Which of the following best describes the arrangement of lymphatic vessels?

a one-way system of vessels beginning with blind-ended lymphatic capillaries The lymphatic vessels form a one-way system in which lymph flows only toward the heart. It begins as blind-ended capillaries.

Lymphatics in the skin travel

along with superficial veins

Lymph sinuses

are large lymphatic capillaries spanned by crisscrossing reticular fibers. Macrophages reside on these reticular fibers and phagocytize foreign matter in the lymph as it flows by in the sinuses.

Medullary cords

are thin inward extensions from the cortical lymphoid tissue, and contain both types of lymphocytes.

Which sequence best describes the flow of lymph through the lymphatic system?

capillaries, vessels, trunks, ducts

Smooth muscle in the walls of all but the SMALLEST LYMPHATIC vessels

contacts RHYTHMICALLY helping to pump the lymph along

Cortex

contains densely packed follicles, many with germinal centers heavy with dividing B cells. The deeper part houses T cells in transit.

Lymphocytes

contains immunocompetent cells that are able to destroy or immobilize foreign substances in the body (antigens)

In newborns the thymus

continues to increase in size during the first year

When lymphoid tissue is loosely packed, it is called

diffuse

Right lymphatic duct

drains lymph from the right upper limb and the right side of the head and thorax

Which of the following are the principal lymphoid organs in the body?

lymph nodes The principal lymphoid organs in the body are the lymph nodes, which cluster along the lymphatic vessels of the body.

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

lymph sinuses Large lymph capillaries spanned by crisscrossing reticular fibers are known as lymph sinuses

What lymphatic structure absorbs excess tissue fluid?

lymphatic capillary

What cells cluster around the medullary sinuses?

macrophages

The lymphatic system is a specialized subdivision of the circulatory system. Although the cardiovascular system has a pump (the heart) and arteries, veins, and capillaries, the lymphatic system lacks two of these structures: the

pump and arteries

B cells mature in the

red bone marrow

Lymphoid tissue is specifically classified as a type of connective tissue called

reticular

What type of soft connective tissue forms the internal skeleton of the lymph nodes?

reticular

The lymphoid tissue's structural framework of is composed of

reticular connective tissue

A major function of the lymphatic system is

return of tissue fluid to the cardiovascular system. Approximately 3 liters of fluid are picked up each day.

Lymphatic system

returns fluids that have leaked from the vascular system back into the blood

Lymphoid follicles (lymphoid nodules)

solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers

Dendritic cells

spiny-looking, capture antigens and bring them back to the lymph nodes.

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

spleen The site of erythrocyte production in the fetus is the spleen.

Splenectomy

surgical removal of the ruptured spleen

Erroneously

swollen glands

A sentinel node is the first lymph node

that receives lymph drainage from a body area suspected of cancer A sentinel node is the first lymph node that receives lymph drainage from a body area suspected of cancer

When fluid pressure in the interstitial space is greater than the pressure in the lymphatic capillary

the minivalve flaps gage open, allowing fluid to enter the lymphatic capillary.

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 tonsils form a ring of lymphatic tissue around the entrance to the pharynx.

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.

Exhibits thymic corpuscles, lacks follicles

thymus

T cells mature in the

thymus

Which of the following features is NOT common to both lymphatic collecting ducts and veins?

transport of chyle Only lymphatic collecting ducts transport chyle, which is a term for fatty lymph.

Tonsillar crypts

trap bacteria and particulate matter, and the bacteria work their way through mucosal epithelium into the lymphoid tissue where most are destroyed.

Appendix

tubular offshoot of the first part of the large intestine and contains a high concentration of lymphoid follicles. Prevent bacteria from breaching the intestinal wall and to generate many memory lymphocytes for long-term immunity.

What structures ensure the one-way flow of lymph through the node?

valves in the afferent and efferent lymphatics

White pulp

where immune functions take place, lymphocytes-reticular fibers. Clusters or forms cuffs around central arteries. They look like islands in a sea of red pulp.

Secondary lymphoid organs

where mature lymphocytes first encounter their antigens and are activated. Lymph nodes, spleen, MALT-tonsils, Peyer's patches-small intestine, appendix.

Red pulp

where worn-out rbc's and bloodborne pathogens are destroyed, huge numbers of erythrocytes and the macrophages that engulf them. Splenic cords-reticular connective tissue spate blood-filled SLPENIC SINUSOIDS.

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

white pulp The white pulp is composed of areas of lymphocytes suspended by reticular fibers.

The deep lymphatic vessels of the trunk and digestive viscera travel

with the deep arteries