Chapter 8: Lymphatic System

Question 1

The lymphatic system and the vascular system form an important functional unit called the? It is a secondary defense system and the primary defense system being the skin and the mucous membranes.

Answer 1

hemic-lymphatic system

Question 2

What are circulating plasma glycoprotiens, also called immunoglobulins are specialized to react with the antigens, initiating a complex immune response that protects the body from damage by eventually destroying the foreign substance.

Answer 2

Antibodies

Question 3

The lymphoid system’s major functional components are the?

Answer 3

lymphocytes (T- and B-lymphocytes)

Question 4

What lymphatic tissue are subepithelial lymphatic tissue associated with somatic orifices and tracts of the respiratory, digestive and urogenital systems. These are accumulations of lymphocytes, plasma cells and monocytes (histiocytes and macrophages) that form recognizable aggregate structures. They are generally found in lamina propria and may occur more frequently to impart a hypercellular nature to this connective tissue. They function as a readily available second line of body defense.

Answer 4

Diffuse, unencapsulated lymphatic tissues

Question 5

What lymphatic tissue are subepithelial accumulations of lymphatic tissue associated the respiratory, digestive and urogenital tracts. This tissue consists of solitary lymph nodules with prominent germinal centers. They occur in the lamina propria, tunica submucosa and occasionally in the tunica adventitia.

Answer 5

Dense, unencapsulated lymphatic tissue

Question 6

What lymphatic tissue tissue scattered throughout the body which are lymph nodes, spleen, hemal node, hemolymph nodes, thymus, bursa of Fabricius.

Answer 6

Dense, encapsulated lymphatic tissue

Question 7

In what lymphoid organs, (lymph nodes, spleen and tonsils) and unencapsulated lymphatic aggregates, lymphocyte production is antigen-dependent and provides committed immunocompetent cells that respond tospecific antigen.

Answer 7

peripheral lymphoid organs

Question 8

In what lymphoid organs, (thymus, bone marrow, Bursa of Fabricius in birds) lymphocyte production is antigen-dependent and supplies uncommitted T- lymphocyte (thymus) or B-lymphocyte (bone marrow, bursa) precursors that latter move to peripheral organs and tissues. Mounting effective immune responses to new antigens requires ongoing production of uncommitted lymphocyte by the central lymphoid organs.

Answer 8

central lymphoid organs

Question 9

What immune response is the first type, in which the T-lymphocytes proliferate, attack and directly kill the invading antigens while others release lymphokines, substances that enhance various aspects of immune response. T-lymphocytes may also attack indirectly by activating B-lymphocytes or macrophages.

Answer 9

Cell-mediated immune response

Question 10

What immune response is the second type of response, in which the B-lymphocyte differentiates into plasma cells and secretes specific antibodies. These antibodies then bind to, inactivate, and/or destroy the particular antigen. The activation and proliferation of B-lymphocytes require the cooperation (help) of T-lymphocytes that respond to the same antigen.

Answer 10

Humoral immune response

Question 11

What cells are primarily responsible for cell-mediated immunity that carries antibody-like antigen receptors (but not Igs) on their surfaces. They arise from the lymphocytes that are carried from the bone marrow to the thymus gland. Here, they mature and acquire immunocompetence before migrating to other peripheral lymphoid tissues and organs

Answer 11

T-lymphocytes (T cells)

Question 12

What T cells kill foreign cells such as virus-infected cells, cancer cells and transplants?

Answer 12

Cytotoxic (killer) T cells

Question 13

What T cells help B or T-lymphocytes to respond to antigens and active macrophages?

Answer 13

Helper T cells

Question 14

What T cells suppress B- or T-lymphocytes. They moderate helper cell activity, thereby helping to regulate humoral immune responses.

Answer 14

Suppressor T cells

Question 15

are primarily responsible for humoral immunity. They mature and become immunocompetent in the bone marrow. After they mature, these cells are carried by the blood to the non-thymic lymphoid tissue, where they reside, primarily in the lymph nodes, spleen, and connective tissue.

Answer 15

B-lymphocytes (B cells)

Question 16

When the immonucompetent B-lymphocytes encounter a specific antigen they become activated, proliferate, and differentiate into what cell?

Answer 16

plasma cell

Question 17

B cells require assistance from helper T cells to respond to many antigens; these antigens are called?

Answer 17

T-dependent (thymus dependent) antigens

Question 18

What cells are able to attack and lyse invading cells through direct cell-to-cell contact. The killing activity of these cells appears to be innate or natural and independent of antigenic activation.

Answer 18

Natural killer (NK) cells

Question 19

These are common monocyte derivatives found lining the vascular sinuses, distributed among the lymphocytes of lymphoid organs and tissues, and dispersed in loose connective tissue. In both the cellular and humoral immunity, they phagocytose complex antigens and enhance their antigenicity by breaking them into a multitude of antigenic determinants for presentation to lymphocytes. They also phagocytose antigen-antibody complexes.

Answer 19

Macrophages

Question 20

These are differentiated B-lymphocyte effector cells that secrete the immunoglobulins primarily responsible for humoral immunity. They are found in all lymphoid tissues; they occur in high concentration in the medullary cords of lymph nodes, the red pulp cords in the spleen, and the lamina propria underlying mucosal and glandular epithelia.

Answer 20

Plasma Cells

Question 21

These are usually stellate cells having long processes that form a meshwork in which lymphocytes, plasma cells, and other tissue components are suspended.

Answer 21

Reticular Cells

Question 22

What are the mesoderm-derived reticular cells of the lymph nodes, spleen, tonsils and bone marrow?

Answer 22

Mesenchymal reticular cells

Question 23

What are the endoderm-derived reticular cells of the thymus?

Answer 23

Epithelial reticular cells

Question 24

In the thymic medulla, the epithelial reticular cells assume many shapes; some becomes flattened to form tight concentric bodies called?

Answer 24

Hassall’s corpuscles

Question 25

In the cortex, epithelial reticular cells are mainly stellate and help form the ? They do not secrete reticular fibers but form their reticular meshwork by attaching to one another at the tips of their long processes with desmosomes.

Answer 25

blood-thymus barrier

Question 26

Many of these cells are derived from the mesenchymal reticular cells. They bind antigen-antibody complexes on their surfaces for long periods without phagocytosing them. In this way, they collect and concentrate antigens for presentation to, and stimulation of, lymphocytes.

Answer 26

Antigen-Presenting Cells

Question 27

Antigen-Presenting Cells in the skin, are called?

Answer 27

Langerhan’s cells

Question 28

Antigen-Presenting Cells in the liver, they are called?

Answer 28

Kupffer’s cells

Question 29

What are spherical collections of lymphocytes that constitute the primary functional subunits of all encapsulated lymphoid aggregates except the thymus. They occur within the loose connective tissue of the body and in all secondary lymphatic organs.

Answer 29

Lymphatic nodules (follicles)

Question 30

What lymphatic nodules consist of a stromal network of reticular cells that have numerous processes and are associated with reticular fibers. They lack germinal centers and contain only small lymphocytes.

Answer 30

Primary lymphatic nodules

Question 31

What lymphatic nodules appear in response to the introduction of antigens into the organism. They have a central light-staining area called the germinal center, in which there is a marked lymphoblastic activity.

Answer 31

Secondary lymphatic nodules

Question 32

What originates as solid epithelial outgrowths from the epithelium of the third pharyngeal pouch. Spreading of the epithelial cells gives rise to thymic epithelial reticulum, which becomes invaded by blood vessels from the surrounding mesenchyme. Lymphoblasts, derived from bone marrow stem cells, invade the interstices, filling spaces between the epithelial cells. It has no afferent lymph vessels, only efferent lymph vessels.

Answer 32

thymus

Question 33

The thymic ? consists mainly of an epithelial reticulum and lymphocytes. This is a dark-staining periphery of each lobule. The stellate epithelial cells possess large, pale ovoid nuclei and long branching processes that contain numerous microfilaments and are connected by other desmosomes. It is the site of T-lymphocyte precursor proliferation and of the blood thymus barrier.

Answer 33

cortex

Question 34

The light-staining area of the thymus reflects the presence of more epithelial reticular cells and fewer lymphocytes than in the cortex. Its epithelial cells characteristically form Hassal’s corpuscles, which consist typically of one or several calcified or degenerated large cells in a concentric arrangement, containing many desmosomes and bundles of microfilaments. The cells in the meshes of the reticular network are predominantly small lymphocytes along with few macrophages.

Answer 34

medulla

Question 35

This is the primary function of the thymus

Answer 35

T-lymphocyte production

Question 36

T-lymphocyte precursors populate in the thymic?

Answer 36

cortex

Question 37

What are the smallest but most numerous encapsulated lymphoid organs. They are distributed throughout the body and along the paths of lymphatic vessels. They are the most organized of all the lymphatic organs and are the only one with both the efferent and afferent lymph vessels and sinuses.

Answer 37

Lymph nodes

Question 38

These organs usually have slight indentations, the ?, where the blood and lymph vessels enter or leave the lymph node.

Answer 38

hilus

Question 39

What structure of lymph nodes that composed primarily of dense irregular collagenous connective tissue, collagen and reticular capsule with a few scattered elastic fibers.

Answer 39

Capsule

Question 40

What structure of lymph nodes is composed of fine reticular cells and fibers that permeate the parenchyma in varying densities. Lymphocytes, macrophages and plasma cells are supported by this reticular meshwork

Answer 40

Stroma

Question 41

What structure of lymph nodes are lined by endothelial cells that form a continuous lining toward the capsule and trabeculae but often in a discontinuous one toward the parenchyma of the node. Lymph percolates into the parenchyma through gaps in the sinus walls. This gives the parenchymal cells access to lymph-borne antigens, cells and particulate matter.

Answer 41

Sinuses

Question 42

What structure of lymph nodes is a T-dependent region, lying between the cortical lymphoid nodules and the medulla. It contains mainly T-lymphocytes suspended in a reticular tissue network. This zone is characterized by the presence of high-endothelial post- capillary venules. T-lymphocytes leave the blood to enter the paracortical zone by passing between the cuboidal endothelial cells lining these vessels.

Answer 42

Paracortical zone

Question 43

What regions of lymph nodes is dark-staining owing to the presence of tightly packed lymphocytes. These are suspended in a reticular connective tissue network and arranged as a layer of typical secondary lymphoid nodules with germinal centers. This region also contains reticular cells, antigen-presenting follicular dendritic cells, macrophages, a few plasma cells and some T-helper cells.

Answer 43

Cortex

Question 44

What regions of lymph nodes is a lighter staining than the cortex. It is composed of cords of lymphoid tissue (medullary cords) separated by medullary sinuses. The lymphocytes are mainly small, less numerous than in the cortex, and concentrated in the cords. The cords are also rich in reticular cells and fibers and contain many plasma cells that have migrated from the cortex.

Answer 44

Medulla

Question 45

What is the largest lymphoid organs. Unlike other lymphoid organs, this organ lacks a definitive cortex and medulla. The parenchyma lacks true lobules; however, the dense connective tissue capsule, which contains a small amount of smooth muscle, gives rise to trabeculae that divide the splenic pulp into incomplete compartments.

Answer 45

spleen

Question 46

What zone forms a border between the red and the white pulps?

Answer 46

Marginal zone

Question 47

It is composed of many erythrocytes, leukocytes, and macrophages, as well as a variety of blood vessels, all suspended within a meshwork of mesenchymal reticular cells and fibers.

Answer 47

Splenic pulp

Question 48

What pulp consists of lymphoid tissue surrounding each of the many central arteries. It consists of dense lymphatic tissue called splenic corpuscles?

Answer 48

White pulp

Question 49

What component of white pulp that the lymphoid tissue immediately surrounding each central artery. This contains mainly T-lymphocytes and constitutes the T-dependent regions of the spleen.

Answer 49

Periarterial lymphatic sheaths (PALS) sleeve

Question 50

What component of white pulp that surrounds each Periarterial lymphatic sheaths (PALS) sleeve or appended to one side. It contains mainly B-lymphocytes and usually includes the typical secondary lymphoid nodule with a germinal center.

Answer 50

Peripheral white pulps (PWP)

Question 51

What pulp is in the form of cords (Billroth’s cords) separated by sinusoids. The pulp is supported by a framework of reticular fibers?

Answer 51

Red pulp

Question 52

What is a lymph node with blood in its sinuses. There is no lymphatic tissues and typical medulla. They are situated in the course of the blood rather than lymph vessels. It occurs in ruminants in retroperitoneal positions along the vertebral column, in the jugular furrow and in association with some visceral organs. The functional significance is unknown.

Answer 52

Hemal node

Question 53

This is also called hemorrhagic lymph node. It receives blood and lymph that intermix in the sinuses. It occurs in the perirenal region of the sheep and goat and in the lumbar area of the ox.

Answer 53

HEMOLYMPH NODE

Question 54

What are composed of solitary or aggregated nodules and diffuse lymphatic tissues. They form rings along the tract from the mouth to the pharynx in the lamina propria. They do not possess afferent lymphatic vessels. Instead, the material is either filtered into the organ or carried to it by cells from the surrounding connective tissue space. Efferent lymph vessels are present.

Answer 54

Tonsils

Question 55

The crypt is a blind and sometimes branched invagination of the surface epithelium.

Answer 55

Tonsil with crypts

Question 56

A single lamina of lymphatic tissue, which may be secondarily bulged outward or slightly, folded to increase the surface area.

Answer 56

Tonsil without crypts

Question 57

What avian lymphatic system major group is composed of the bursa of Fabricius and the thymus?

Answer 57

Primary lymphoid system

Question 58

What avian lymphatic system major group is composed of the spleen, Hardenian gland (located under the eyes of birds), caecal tonsils and diffuse encapsulated lymphatic nodules in the digestive tube particularly the small and the large intestine.

Answer 58

Secondary lymphoid system

Question 59

What is present only in birds. It is a blind sac which opens into the cloaca and is often referred to as “cloacal tonsil” or “cloacal thymus.” The wall is extensively folded and covered by a simple columnar or pseudostratified columnar epithelium. Lymphatic nodules are located between the folds and seem to produce follicle-like structures. Germinal centers are present and these are called medullary structures whereas the darker coronal regions are referred to as cortical areas. Although this organ resembles the tonsils and thymus, it functions in the production of B-lymphocytes. It reaches its maximum size at 4-5 months of age and involutes with onset of sexual maturity. By 10 months of age, the bursa is reduced to a tiny saccule and eventually disappears entirely.

Answer 59

bursa of Fabricius

Question 60

What lymph organ is similar in structure to that of mammals. It also involutes with age such that only traces of it are recognized in birds between 13-17 months old.

Answer 60

Avian thymus

Question 61

It is round, small and brownish red in color. It has the same histology as in the lymph organ of mammals.

Answer 61

SPLEEN