Histology Exam 2 - Lymphatic

Front 1

What is the function of the Lymphatic System?

Back 1

1. Concentrate antigens in certain lymphoid organs.

2. Circulate lymphocytes through organs to come in contact with antigens.

3. Convey the product of the immune response (effector T-lymphocytes, humoral antibodies) to tissues that need them.

Front 2

Antigen

Back 2

A soluble infectious, foreign organism.
Transformed tissue (cancerous cells)

Front 3

Humoral immune Response

Back 3

Antibodies bind and mark antigens for destruction by other immune cells.

Front 4

Cellular immune Response

Back 4

Targets transformed and virus infected cells for destruction by lymphocytes.

Front 5

Types of Lymphocytes

Back 5

T-lyphocytes (T cells)
B-lymphocytes (B cells)
NK cells (natural killers cells)

Front 6

T-lymphocytes (T cells)

Back 6

t=thymus - where they differentiate
-Involved in cell-mediated immunity
-60-80% of circulatory lymphocytes
-Express CD2, CD3, CD7 markers AND CD4 and CD8

Front 7

B-lymphocytes (B cells)

Back 7

b=bursa of birds - first noticed
-Involved in the production of antibodies (immunoglobulins)
-Associated with humoral immunity
-20-30% of circulating lymphocytes
-Express MHC II (major histocompatibility II)
-CD markers are CD9, CD19, CD20 and CD24

Front 8

NK (natural killer) cells

Back 8

-Programmed to recognize transformed cells (cells infected with viruses or tumor cells)
-After recognition, they release performs and fragmenting.
-Do not require antibodies!
-5-10% of circulating lymphocytes
-Specific markers include CD16, CD56, and CD94.

Front 9

Cluster of Differentiation (CD) Molecules

Back 9

-Unique cells surface molecules
-Are expressed in different cell types and/or different stages of differentiation
-Can identify with specific antibodies.

Front 10

Features of Lymphatic Tissue:

Back 10

-Diffuse lymphatic tissue
-Lymphatic nodules
-Lymph nodes
-Spleen
-Bone marrow
-Thymus

Front 11

Diffuse Lymphatic Tissue

Back 11

Found in the Lamina Propria of:
-Alimentary Canal
-Respiratory Passages
-Genitourinary Tract

Front 12

Lymphatic Nodules

Back 12

Localized concentrations of lymphocytes. aka follicles.

Sometimes found in specialized locations:
-appendix
-pharyngeal tonsils (adenoids)
-palatine tonsils (tonsils)
-lingunal tonsils
-in ileum - Peyer's patches

If homogenous
-primary nodule
-inactive

If nodule has a lighter staining center
-called germinal center
-active

Front 13

Lymph Nodes

Back 13

Smallest, but most numerous encapsulated lymphoid organs.
Scattered in groups along lymphatic vessels.

Front 14

Lymph Node Structure

Back 14

-Bean Shaped: concave portion called HILIUM
-Has a peripheral CORTEX and central MEDULLA.
-Connective tissue sheath sends TRABECULAE into and subdivides the cortex.
-Blood vessels enter and leave through the helium.
-Flow Direction=subcapsular sinus - trabecular sinus - medulary sinus.

Front 15

Lymph Node Function

Back 15

-Filtration of lymph
-Phagocytosis
-Production of lymphocytes
-Production of antibodies in response to antigens.

Front 16

Thymus

Back 16

-bilobed
-No lymphatic vessels or sinuses
-Lymphocytes are between epithelial cells.

Front 17

Lymphatic Epithelial Cells

Back 17

-Connected by desmosomes
-Have a stellate struction
-Are called epithelioreticular cells
-Form concentric, pigmented layers called HASSELL's CORPUSCLES.

Front 18

Hassell's Corpuscles

Back 18

Unclear function.

Structures found in the medulla of the human thymus, formed from eosinophilic epithelial reticular cells.

Front 19

Thymus Anatomy

Back 19

Outer connective tissue CAPSULE with trabeculae that extend into the cortex.
-Capsule contains blood vessels, efferent lymphatic vessels and nerves.

Outer cortex has higher proportion of lymphocytes, therefore more basophilic.

Medulla stains more lightly because lymphocytes more differentiated and more epithelioreticular cells.

Front 20

Role of Thymus

Back 20

-Site of lymphocyte proliferations
-Are T-lymphocytes

Front 21

Blood-Thymic Barrier

Back 21

Blood vessels enter thymus from trabeculae.
Epithelioreticular cells also wrap around vasculature, therefore the barrier consists of:
-Thin capillary epithelium
-It's basal lamina
-A thin connective tissue layer
-Basal lamina of epithelioreticular cells.
-Epithelioreticular cells.

Front 22

Spleen

Back 22

Largest lymphatic organ.
Contains:
-Large number of lymphocytes
-Specialized vascular spaces.
-Meshwork of reticular cells.
-Rich supply of macrophages.

Front 23

Spleen - Function

Back 23

-Lymphocyte and antibody production
-Destruction of damaged red blood cells
-Blood formation in fetus
-Storage of blood.

Front 24

Structure of the Speen

Back 24

-CAPSULE of dense connective tissue with trabeculae
-SPLENIC PULP (white or red)
-SPLENIC CORDS (Cords of Billroth): reticular fibers and reticular cells.

Front 25

Spleen - White Pulp

Back 25

-Is white in fresh tissue.
-Has a central artery
-Arteries surrounded by Periarterial Lymphatic Sheaths (PALS)

Front 26

Spleen - Red Pulp

Back 26

-Red b/c of many red blood cells.
-Has splenic sinuses that have unusual shaped endothelial cells.
-Allow blood cells to move in and out of vasculature.
-Macrophages put processes through holes in sinuses to monitor blood for phagocytosis.

Front 27

Splenic Circulation

Back 27

-Branches of splenic artery enter white pulp from trabeculae.
-In white pulp blood moves into venous circulation.

Front 28

How does blood in white pulp move into venous circulation? (2 ways)

Back 28

1. Directly (open route)
2. May go out and back in (closed route)