Lymphoid System Histology I

Question 1

Consists of tissues-organs with cells involved in host defense and lymph transport

Answer 1

Lymphoid System

Question 2

What are the two primary lymphoid organs?

Answer 2

Bone marrow and Thymus

Question 3

B-lymphocytes become immunocompetent in

Answer 3

Bone marrow

Question 4

Migrate to the thymus for maturation

Answer 4

T-lymphocytes

Question 5

Immunocompetent lymphocytes migrate from primary to secondary lymphoid organs to participate in host

Answer 5

Host defense

Question 6

Diffuse or nodular lymphoid tissue for host defense in mucosa

Answer 6

MALT

Question 7

Key parenchymal cells include lymphocytes and

Answer 7

APCs

Question 8

Other leukocytes, such as granulocytes are also important in host defense. What are two examples?

Answer 8

1. ) Neutrophils (anti-bacterial)

2. ) Eosinophils (anti-parasitic)

Question 9

Supports immune cells of lymphoid tissues-organs

Answer 9

Connective tissue stroma

Question 10

May be supported within mucosal loose connective (lamina propria underlying epithelium) and may be diffuse or organized in nodules/ follicles

Answer 10

Lymphoid cells

Question 11

Covered by an eosinophilic dense connective tissue capsule with extensions of trabeculae that subdivide parenchyma

Answer 11

Encapsulated lymphoid organs (including thymus, lymph node, spleen)

Question 12

Within some encapsulated organs, lymphoid cells are supported by

Answer 12

Reticular connective tissue

Question 13

Made up of an intricate framework of fine, branching, silver-staining reticular fibers (type III collagen) secreted by fibroblast-type reticular cells

Answer 13

Reticular connective tissue

Question 14

The predominant fiber in regions with loose and dense connective tissues and may be continuous with reticular fibers made of type III collagen in regions with reticular CT

Answer 14

Type I collagen

Question 15

Lymphatic and cardiovascular systems are interconnected with lymphocytes entering-exiting tissues after traveling in

Answer 15

Lymph and blood

Question 16

In mucous and cutaneous membranes, antigens that penetrate epithelium and enter the underlying loose CT, encounter lymphoid cells that can initiate

Answer 16

Immune responses

Question 17

Carry lymph into lymph nodes for filtration

Answer 17

Afferent lymph vessels

Question 18

Carry filtered lymph (fortified with additional immune cells to antigen) out to various regions

Answer 18

Efferent lymph vessels

Question 19

Not present in cornea, cartilage, nervous tissue, thymus, bone marrow

Answer 19

Lymphatics

Question 20

At the 7th month of fetal life, the primary site of hematopoiesis throughout life is the

Answer 20

Bone marrow

Question 21

Bone marrow histological sections demonstrate architecture with hematopoietic cords of developing

Answer 21

Blood cells

Question 22

Hematopoietic stem cells (HPSCs) generate

Answer 22

Blood cells

Question 23

Form and mature (gene rearrangement and selection) within bone marrow

Answer 23

B-lymphocytes

Question 24

A general term for lymphoid system cells found in the loose connective tissues of mucosa lining the gastrointestinal, respiratory, urogenital systems

Answer 24

Mucosa-Associated Lymphoid Tissue (MALT)

Question 25

The epithelium covering lymphoid nodules in GALT contains -appears to serve as APCs that present intraluminal antigen to GALT cells

Answer 25

M cells

Question 26

May be organized diffusely or in nodules/follicles to guard the body as initial sites of host defense with immune response to antigens penetrating the mucosa

Answer 26

MALT cells

Question 27

Mainly consist of B-lymphocytes with T-lymphocytes in nearby, surrounding areas

Answer 27

Lymphoid Nodules

Question 28

After initial contact in MALT, immune cells and antigen travel to regional lymph nodes for a more elaborate immune response leading to proliferation and differentiation with progeny that return to infiltrate the mucosa as

Answer 28

Effector B- and T-lymphocytes

Question 29

While MALT may have isolated, transient/temporary follicles that disappear after threat has been neutralized, permanent aggregations of follicles/nodules can be seen in the

Answer 29

Tonsils, ileum, and appendix

Question 30

Appear as dark, uniform masses of mostly small B-lymphocytes (naive and memory) that are entering and leaving the follicle

Answer 30

Primary lymphoid nodules

Question 31

Arise from primary nodules with B-lymphocytes activated by appropriate antigen or by APC-activated Th cells to form an outer mantle zone/corona (containing inactive B-lymphocytes) and a large, pale germinal center

Answer 31

Secondary Lymphoid Nodules

Question 32

Contain activated B-lymphocytes that proliferate (mitotic figures visible) and form lymphoblasts with large, pale staining cytoplasm

Answer 32

Germinal Centers

Question 33

Select lymphoblasts that have high affinity to the antigen and the remaining aberrant lymphoblasts undergo apoptosis and phagocytosis by macrophages

Answer 33

Follicular Dendritic Cells (FDCs)

Question 34

Surviving lymphoblasts differentiate into memory cells and antibody-secreting

Answer 34

Plasma cells

Question 35

A collection of lymphoid tissue in the pharynx that encounters antigens entering through the oral and nasal cavities

Answer 35

Waldeyer’s tonsillar ring

Question 36

There are tonsils in the

Answer 36

Naropharynx (adenoids) and oropharynx

Question 37

Exhibit a stratified squamous epithelium that lines the surface and deep mucosal folds known as crypts

Answer 37

Palatine tonsils

Question 38

The epithelium that lines the deep crypts is thin and often obscured by penetrating lymphocytes emptying into the

Answer 38

Oral cavity

Question 39

Lymph nodes filter lymph taken up from tissues in order to activate lymphocytes in response to

Answer 39

Antigen

Question 40

The stroma of the lymph node includes the dense connective tissue capsule and its extensions of

Answer 40

Trabeculae

Question 41

Parenchymal cells of the lymph node are supported along an intricate and extensive framework of fine, branching

Answer 41

Reticular fibers

Question 42

The parenchyma of the lymph node includes an outer connective tissue capsule surrounding cells forming an outer darker cortex with nodules/follicles containing many

Answer 42

B-cells

Question 43

The parenchyma also has a paracortex containing many

Answer 43

T-cells

Question 44

The parenchyma also contains an inner, lighter medulla with

Answer 44

Plasma cells, lymphocytes, and macrophages

Question 45

Reticular CT in sinuses allows lymph to percolate slowly as macrophages within sinuses survey lymph for

Answer 45

Antigens

Question 46

Immune responses rely on close interaction of B-lymphocytes in nodules and T-lymphocytes in

Answer 46

Internodular and paracortical regions

Question 47

Activated in immune responses and are transient (in constant flux), as they enter-exit through porous endothelium along sinuses and move within and outside the lymph node

Answer 47

Lymphocytes

Question 48

Like MALT, antigen/APCs activate lymphocytes (Th and B) to form secondary follicles with

Answer 48

Germinal centers

Question 49

Activated lymphocytes and plasma cells migrate from the cortex to form cords of cells in the

Answer 49

Medulla

Question 50

From their positions in cords, plasma cells secrete antibodies into lymph passing through medullary sinuses and some activated lymphocytes pass into sinuses and leave the lymph node to remote sites to respond to

Answer 50

Antigen

Question 51

Vasculature enters and exits at the hilum, located at the concave surface of the

Answer 51

Lymph node

Question 52

Just distal to capillary beds, postcapillary high endothelial venules (HEVs) in the paracortex (and medulla) are lined by a specialized simple cuboidal epithelium that allows

Answer 52

Lymphocyte extraversion

Question 53

From the paracortex, cytokines recruit lymphocytes for distribution to regions in the

Answer 53

Cortex and paracortex

Question 54

Thus, lymphocytes can reach the lymph node via blood through

Answer 54

HEVs

Question 55

Thus, lymphocytes can reach the lymph node via lymph through

Answer 55

Afferent Lymph vessels

Question 56

Lymph node sinuses allow for lymph to slowly percolate and interact with

Answer 56

Immune cells

Question 57

Filtration through lymph nodes occurs as the lymph flows through

Answer 57

Sinuses

Question 58

Contain reticular fibers for support and to slow flow so that APCs can interact with lymph

Answer 58

Sinuses

Question 59

Pierce the capsule at the lymph node’s convex surface to bring lymph and immune cells into sinuses

Answer 59

Afferent lymph vessels

Question 60

Often difficult to identify and can be seen as containing valves, leukocytes (lymphocytes, macrophages, no RBCs), and sometimes metastatic cancer cells

Answer 60

Afferent Lymph Vessels

Question 61

Lymph flows from afferent lymph vessels to

Answer 61

Subcapsular/marginal sinuses

Question 62

Then from the subcapsular/marginal sinuses to the

Answer 62

(Para)trabecular sinuses

Question 63

Then from the (para)trabecular sinuses (along trabeculae) to the irregular medullary sinuses (weaving among medullary cords) to the

Answer 63

Efferent lymph vessels at concave hilum

Question 64

The lymph leaving the lymph node in efferent lymph vessels contains

Answer 64

Lymphocytes and antibodies

Question 65

Inflammation of lymph nodes-lymph vessels from severe bacterial infections, sometimes seen as red streaks under skin in areas with lymph drainage from infected area

Answer 65

Lymphadenitis-lymphangitis

Question 66

In contrast to lymph filtration by lymph nodes, the spleen filters blood in adult humans to remove

Answer 66

Senescent RBCs

Question 67

The spleen also mounts immune reactions to

Answer 67

Blood-born antigens

Question 68

In the adult, the spleen may contribute to extramedullary hematopoiesis when marrow function is

Answer 68

Insufficient

Question 69

Consists of a capsule, trabeculae, and reticular fibers

Answer 69

Stroma of the spleen

Question 70

Deep to the visceral peritoneum (mesothelium), the dense collagenous connective tissue capsule of spleen also contains

Answer 70

Elastic and smooth muscle fibers

Question 71

Extend from the capsule and carry branches/tributaries of splenic vessels entering/exiting at the hilum

Answer 71

Trabeculae

Question 72

Made up of two types of pulp that are based on the red and white coloring of fresh, gross tissue

Answer 72

Spleen parenchyma

Question 73

Macrophages in red pulp remove aged/damaged

Answer 73

RBCs

Question 74

Mounts immune responses to blood-borne antigens and is similar to lymph nodes, which mount immune responses to lymph-borne antigens

Answer 74

White Pulp

Question 75

Borders between the white and red pulps and contains many macrophages and lymphocytes

Answer 75

Marginal Zone

Question 76

Branches of trabecular arteries enter the white pulp as central arteries/arterioles whose tunica adventitia are infiltrated by -Forms pariarterial lymphoid sheath (PALS)

Answer 76

T-lymphocytes

Question 77

Branches of the central artery/arteriole in white pulp shed PALS and travel through the marginal zone as penicillar arteries and capillaries surrounded by

Answer 77

Macrophages

Question 78

In the spleen’s closed circulation, capillaries empty directly into

Answer 78

Red pulp sinuses

Question 79

Allows for blood to percolate among macrophages and lymphocytes in the cords and marginal zone, resulting in more effective exposure of RBCs and antigens leading to removal of old RBCs and immune responses

Answer 79

Humans open circulation in spleen

Question 80

Formed by a central artery/arteriole invested in a periarterial lymphoid sheath (PALS), an arterial cuff of mostly T-lymphocytes, and occasional, adjacent primary or secondary lymphoid nodules/ follicles mainly made up of B-lymphocytes that push the central arteriole to appear eccentric

Answer 80

White pulp

Question 81

The marginal zone borders the white pulp and red pulp and contains many macrophages and lymphocytes for

Answer 81

Antigen presentation

Question 82

Made up of splenic cords (of Billroth) and splenic sinuses/sinusoids

Answer 82

Red pulp

Question 83

Contain macrophages, erythrocytes, and other cells that are supported by reticular CT

Answer 83

Splenic cords

Question 84

From the splenic cords, macrophage processes and antibodies secreted by plasma cells encounter blood-borne pathogens by passing through the

Answer 84

Interendothelial slits

Question 85

Epithelial reticular cells (ERCs) in the thymus are unlike the reticular fiber-secreting reticular cells in the

Answer 85

Lymph node and spleen

Question 86

Rather than an extensive mesh of reticular fibers, thymocytes are intimately supported by a network of large, pale, stellar-shaped, euchromatic

Answer 86

ERCs

Question 87

The processes of these ERCs are linked by

Answer 87

Desmosomes

Question 88

Involved in thymocyte selection-deletion, contribution to blood-thymus barrier, secretion of hormones and cytokines, and degeneration into thymic corpuscles

Answer 88

Epithelial reticular cells (ERCs)