Lymphatic system Flashcards by KEITH ANNE ABARRATIGUE

Responsible for the immunological defense of the body.
Comprised of cells, tissues, and organs

LYMPHATIC SYSTEM

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Cells of the immune system are distributed in the body as: (4)

 Single cells
 Isolated accumulations of cells
 Distinct nonencapsulated lymphatic nodules in the loose connective tissue
 Encapsulated individual lymphoid organs

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Provides the second and the third lines of defense

IMMUNE SYSTEM

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IMMUNE SYSTEM 2 components

 Innate immune system
 Adaptive immune system

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 aka natural immune system
Non-specific

INNATE IMMUNE SYSTEM

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 Innate immune system is Composed of: (3)

 Complement system (series of blood-borne proteins)
 Macrophages and neutrophils (phagocytic cells)
Natural killer (NK) cells

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 aka acquired immune system
 Responsible for eliminating threats from specific invaders

ADAPTIVE IMMUNE SYSTEM

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 4 primary characteristics of Adaptive immune system

 Immunological memory
 Immunological specificity
 Immunological diversity
 Self/non-self recognition

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2 types of Adaptive immune system

 Humoral immune response
 Cell-mediated immune response

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 Depends on the formation of antibodies

Humoral immune response (adaptive immune system)

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 Cytotoxic response

Cell-mediated immune response (adaptive immune system)

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KEY CELLS OF THE INNATE AND ADAPTIVE
IMMUNE SYSTEMS (5)

T lymphocytes
B lymphocytes
Macrophages
Antigen-presenting cells (APCs)
Natural killer (NK) cells

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 Originate in the bone marrow → migrate to the thymus to become immunocompetent
 Cell-mediated immunity

T lymphocytes

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 Originate and become immunocompetent in the bone marrow
 In birds, _____ ___ ______
 Humoral immunity

B lymphocytes
bursa of Fabricius

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 Phagocytose foreign substances, breaking them down into _____

Macrophages
epitopes

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 Vital for the activation of lymphocytes to produce an adaptive immune response
 Macrophages, dendritic cells and B lymphocytes

Antigen-presenting cells (APCs)

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 Recognise and kill virus-infected and tumor cells

Natural killer (NK) cells

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A type of connective tissue characterized by a rich supply of lymphocytes

LYMPHOID TISSUE

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May exist as:
- Free within the regular connective tissue
- Surrounded by capsules, forming the lymphoid organs

LYMPHOID TISSUE

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Scattered throughout loose connective tissues of the gut, respiratory tract, urogenital
system, and skin and in extranodular areas of lymphatic organs

Diffuse lymphoid tissue

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Lymphoid tissue types (2)

Diffuse lymphoid tissue
Lymphoid nodules

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Lymphoid nodule types (2)

Primary lymphoid nodules
Secondary lymphoid nodules

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Do not contain germinal centers

Primary lymphoid nodules

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 Characterized by a light-staining germinal center within the nodule and an outer
mantle zone or corona

Secondary lymphoid nodules

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Types of lymphoid organs based on location (2)

Primary (central) lymphoid organs Secondary (peripheral) lymphoid organs

Responsible for the development and maturation of lymphocytes into mature, immunocompetent cells

Primary (central) lymphoid organs

Primary (central) lymphoid organs included organs and in which species: (4)

 Bone marrow (mammals)  Thymus (mammals and birds)  Bursa of Fabricius (birds)  Aggregated lymphatic nodules of the ileum (sheep, cattle)

Lymphocytes migrate into these organs after becoming immunocompetent  Responsible for the proper environment in which immunocompetent cells can react

Secondary (peripheral) lymphoid organs

Secondary (peripheral) lymphoid organs includes these organs (4). mention example organs on the first one

 Mucosa-Associated Lymphatic Tissue (MALT) - Tonsils, BALT, GALT Lymph nodes  Spleen  Hemal nodes

Located in the mediastinum Derived from: endoderm  As a solid outgrowth from the epithelium of the _____ pharyngeal pouch  Epithelial cells gives rise to a _____ ______ _____

THYMUS 3rd thymic epithelial reticulum

“Lymphoepithelial organ”

THYMUS

Bilobed; surrounded by a CT capsule → penetrates the parenchyma as septa → divides it into incomplete lobules

“Lymphoepithelial organ” or the thymus

Thymus parts (2)

THYMIC CORTEX THYMIC MEDULLA

Composed of an extensive population of:  Small T lymphocytes (thymocytes)  Epithelial reticular cells (large, stellate cells with light-staining oval nuclei)  Type I, II, and III  Macrophages

THYMIC CORTEX

Composed of:  Large T lymphocytes  Epithelial reticular cells  Type IV, V, VI  _____ corpuscles (thymic corpuscles)

THYMIC MEDULLA Hassall’s

THYMUS (EPITHELIAL RETICULAR CELLS) (6)

Types (I, II, III, IV, V, VI)

Separate the thymic parenchyma from the CT (capsule, septa) of the organ Surrounds blood vessels. which type of thymus reticular cells and what is its location?

Type I Cortex

Form desmosomal junctions with each other Compartmentalize the cortex into isolated areas for the developing T cells Present MHC I, MHC II, and self-antigen to thymocytes. which type of thymus reticular cells and what is its location?

Type II Midcortex

Form occluding junctions with each other & epithelial reticular cells of the medulla Isolates the cortex from the medulla. Also present MHC I, MHC II, and self-antigen to thymocytes. which type of thymus reticular cells and what is its location?

Type III Corticomedullary junction (deep cortex)

Assist in the formation of the corticomedullary junction. which type of thymus reticular cells and what is its location?

Type IV Corticomedullary junction (medulla)

Form cellular scaffolding of the medulla. which type of thymus reticular cells and what is its location?

Type V Medulla

Form Hassall’s corpuscles Release cytokine thymic stromal lymphopoietin. which type of thymus reticular cells and what is its location?

Type VI Medulla

Blind opening located in the dorsal wall of the cloaca Has extensively folded wall Lined by: Simple columnar or pseudostratified epithelium  Subdivided by connective tissue trabeculae into numerous distinct lobules called _____ Regresses after peak development until nearly disappearing ~___weeks onwards

BURSA OF FABRICIUS follicles 9

Parts of follicles (2)

 Outer = corona  Medulla = germinal center

Resembles the  Tonsil: associated with a lining epithelium  Thymus: having nodules (follicles) with cortex and medulla

BURSA OF FABRICIUS

Composed of a nonencapsulated, localized lymphocyte infiltration and lymphoid nodules in the mucosa of the gastrointestinal, respiratory, and urinary tracts

MUCOSA-ASSOCIATED LYMPHOID TISSUE (MALT)

Examples of MALT (3)

 Gut-associated lymphoid tissue (GALT)  Bronchus-associated lymphoid tissue (BALT)  Tonsils

 Most of the lymphoid follicles are isolated from each other

Gut-associated lymphoid tissue (GALT)

GALT consists of (2)

 Peyer’s patches  M cells

GALT  Most prominent accumulation Located in the ileum

Peyer’s patches

GALT  Squamous-like cells lining the regions immediately adjacent to lymphoid follicles

M cells

Located in the walls of bronchi and bronchioles  Development of _____ is antigen-dependent  Presence widely varies among species

Bronchus-associated lymphoid tissue (BALT

Examples of tonsils (3)

 Palatine  Pharyngeal Lingual

types of tonsils (2)

With crypts Without crypts

 Bilateral  In lateral walls of the oropharynx Lined with a non-keratinized squamous stratified epithelium  Deep aspect of each tonsil is isolated from the surrounding CT by a dense fibrous CT  Has epithelial invaginations that penetrate tonsil deeply (____)

Palatine Tonsils crypt

 Single  In the roof of nasopharynx Lined by pseudostratified ciliated columnar epithelium  Has a thin underlying capsule  Instead of crypts, has shallow, longitudinal infoldings (______)

Pharyngeal Tonsil pleats

 Smaller but more numerous in number  At the base of the tongue Lined by non-keratinized stratified squamous epithelium  Deep aspect has a flimsy capsule  Has numerous crypts - Bases receive the ducts of mucous minor salivary gland

Lingual Tonsils

Small, encapsulated, oval structures  Capsule composed primarily of dense irregular connective tissue  In ruminants: smooth muscle cells are also present

LYMPH NODE

Interposed in the path of lymph vessels Filter antigens from the lymph before returning it to the bloodstream The only lymphatic organ with both afferent and efferent lymph vessels

LYMPH NODE

 Penetrate the capsule at several different sites and open into ______ _____  ______ sinuses arise from the subcapsular sinus to accompany the connective tissue trabeculae and continue into medullary sinuses

Afferent lymph vessels subcapsular sinus Cortical

3 regions of afferent lymph vessels

 Cortex  Paracortex  Medulla

 Composed mainly of B cells, APCs, macrophages, and reticular cells  Has primary and secondary lymphatic nodules separated by diffuse lymphatic tissue

Lymph node cortex

 Region of the lymph node between the cortex and the medulla  Houses mostly T cells and is the thymus-dependent zone of the lymph node

Paracortex

Lymph node medulla parts (2)

 Medullary cords  Medullary sinusoids

 Mainly T cells, B cells, plasma cells of lymph node medulla

 Medullary cords

 Continuous with the capsular and cortical sinuses  T cells and B cells enter the sinusoids and leave the lymph node via efferent lymph vessels

Medullary sinusoids

 Arrangement of cortex and medulla are reversed  Arteries enter the _____ lymph node with the afferent lymph vessels Which species has this lymph node?

porcine

 Cortex and medulla also reversed but medullary component is greater. which species has this lymph node?

Equine

Very large lymphoid nodules. which species has this lymph node?

Bovine

which species has a GENERALLY ABSENT lymph node.

Avian

Largest lymphoid organ of the body Covered by a thick irregular dense connective tissue capsule with occasional smooth muscle cells  Trabeculae extend from the capsule and the hilus into the parenchyma

SPLEEN

Functions of spleen (4)

 Hematopoiesis  Filter blood  Mount immune response  Destruction of old erythrocytes

The parenchyma of the spleen is divided into: (2)

 Red pulp White pulp

Both red and white pulp are supported by _____ ______ that form a supporting framework of the spleen

reticular fibers

Lymphoid nodules (splenic corpuscles)  _____ _____ _____ (PALs)

White pulp Periarteriolar lymphoid sheaths

Parts of white pulp (2)

Marginal zone Marginal sinus

Separates the white pulp from the red pulp

Marginal zone

 A series of anastomosing channels in the marginal zone Not equally apparent in all species

Marginal sinus

Red pulp parts (2)

 Splenic sinuses  Splenic cords (cords of Billroth)

Lined by unusual elongated endothelial cells called ____ _____

Splenic sinuses stave cells

 Contain a network of reticular cells and fibers  Filled with T and B lymphocytes, macrophages, other leukocytes, and red blood cells

Splenic cords (cords of Billroth)

The splenic cords of these species (2) contain numerous smooth muscles

Ruminants and porcine:

the splenic cords of these species (2) has myofibroblast

Horses and dogs

Two types of spleen:

a. Defensive type b. Storage type

 Few trabeculae and muscle fibers, abundant white pulp  Present in ____

Defensive type spleen man

 Many trabeculae and muscle fibers, few but large white pulp  e.g. horse, dog, cat

Storage type spleen

(between the defensive and storage) type of spleen. which species have this? (2)

Intermediate Ruminants and swine

Found in ruminants Prevalent in the sublumbar area along the vena cava and abdominal aorta

HEMAL NODE

Sinuses are filled with ______ Less lymphoid nodules Trabeculae of connective tissue are not apparent

HEMAL NODE blood

Similar to the lymph node except:  Sinuses contain both blood and lymph Also found in ruminants

HEMOLYMPH NODE