lymph

What is the second most abundant WBC in circulation?

Lymphocytes

What is the most abundant WBC in circulation?

Neutrophils

What percentage of WBCs in circulation are neutrophils?

55-65%

What percentage of WBCs in circulation are lymphocytes?

20-50%

What is the shape of a lymphocyte’s nucleus?

Round to ovoid

Why does the nucleus of a lymphocyte appear large?

It occupies 90% of the cell

What is the size range of small lymphocytes?

6-9 μm

What is the approximate size of a small lymphocyte?

7.5 μm

What is the size range of large lymphocytes?

10-15 μm

What is the percentage of large lymphocytes in circulation?

3%

Where are lymphocytes initially formed?

Primary lymphoid organs (Thymus and Bone Marrow)

Where does most lymphocyte activation and proliferation occur?

Secondary lymphoid organs (Lymph nodes, Spleen, Peyer patches, Appendix)

What is the appearance of small lymphocytes?

Dark nucleus with a thin rim of cytoplasm

What type of granules do lymphocytes contain?

Azurophilic granules

Why are lymphocytes not classified as granulocytes?

They lack specific granules like neutrophils, eosinophils, and basophils

Where are B and T cells indistinguishable based on morphology?

Under standard light microscopy

What happens to lymphocytes after antigenic stimulation?

They become memory cells

What happens when a person is exposed to chickenpox?

Memory B and T cells form, leading to lifelong immunity

What are CD markers?

Surface proteins that help differentiate B and T cells

What is the function of T-cell receptors (TCRs)?

Recognize antigenic epitopes

What are the major subpopulations of T cells?

Helper T cells, Cytotoxic T cells, Regulatory T cells, γδ T cells

What CD marker do Helper T cells express?

CD4

What CD marker do Cytotoxic T cells express?

CD8

What is the function of Helper T cells?

Bind MHC Class II molecules and help in immune response

What is the function of Cytotoxic T cells?

Kill virus-infected and foreign cells by binding MHC Class I molecules

What CD markers do Regulatory T cells express?

CD4+CD25+

What is the function of Regulatory T cells?

Inhibit specific immune responses

What type of chains do γδ T lymphocytes have in their receptors?

γ (gamma) and δ (delta) chains

What are the major surface receptors of B cells?

Immunoglobulins (IgM or IgD)

What are the five types of immunoglobulins?

IgG, IgA, IgM, IgD, IgE

What is the function of plasma cells?

Produce immunoglobulins (antibodies)

What type of immunity do B cells provide?

Humoral immunity

What is the percentage of T and B cells in the thymus?

100% T cells, 0% B cells

What is the percentage of T and B cells in the bone marrow?

10% T cells, 90% B cells

What is the percentage of T and B cells in the spleen?

45% T cells, 55% B cells

What is the percentage of T and B cells in lymph nodes?

60% T cells, 40% B cells

What is the percentage of T and B cells in the blood?

70% T cells, 30% B cells

What are the three classifications of lymphoid tissue?

Loose lymphoid tissue, Dense lymphoid tissue, Nodular lymphoid tissue

Where is loose lymphoid tissue found?

Lamina propria of trachea, esophagus, internodular regions of tonsils and Peyer patches

Where is dense lymphoid tissue found?

Lamina propria of ileum, colon, and appendix

What are nodular lymphoid tissues?

Compact aggregates of B cells

What are the two types of lymphoid nodules?

Primary and secondary

What is a characteristic of primary lymphoid nodules?

Uniform cell density and staining

What happens to secondary lymphoid nodules after antigenic stimulation?

They form a germinal center

Where are solitary lymphatic nodules found?

Lamina propria of the digestive, respiratory, and urinary tracts

What are examples of aggregated lymphatic nodules?

Peyer patches in the ileum, tonsils, appendix

What are the primary lymphoid organs?

Thymus and Bone Marrow

What are the secondary lymphoid organs?

Tonsils, Lymph Nodes, Spleen, MALT

What is the function of the thymus?

Maturation of T lymphocytes and removal of self-reactive T cells

What happens to the thymus after puberty?

Undergoes involution, decreasing in size and filling with adipose tissue

What are the two regions of the thymus?

Cortex and Medulla

What is found in the thymic cortex?

Immature T-lymphocytes (thymocytes)

What is found in the thymic medulla?

Fewer lymphocytes and Hassall corpuscles

What are Hassall corpuscles?

Aggregates of epithelial cells in the thymic medulla

What is MALT?

Mucosa-associated lymphoid tissue

What are the types of tonsils?

Palatine, Lingual, and Pharyngeal

What is the function of the spleen?

Filters blood, destroys old erythrocytes, produces antibodies

What are the two main regions of the spleen?

White pulp and red pulp

What is found in the white pulp of the spleen?

Lymphoid nodules with a central arteriole

What is found in the red pulp of the spleen?

Splenic cords of Billroth and splenic sinusoids

What is the function of splenic sinusoids?

Filter blood and separate healthy from effete RBCs

What happens to old red blood cells in the spleen?

They are engulfed by macrophages in the Billroth cords

What type of cells line splenic sinusoids?

Stave cells

What is the function of stave cells?

Separate healthy RBCs from effete RBCs

What is the main function of the spleen?

Defense against blood-borne antigens and destruction of old erythrocytes

What type of blood vessel is associated with the white pulp?

Central arteriole

What type of immune response is associated with B cells?

Humoral immunity

What type of immune response is associated with T cells?

Cell-mediated immunity

What are Peyer patches?

Aggregates of lymphoid nodules in the ileum

What type of tissue forms the stroma of lymphoid organs?

Reticular connective tissue

What system is the lymphatic system a part of?

Immune system

What is the main function of the immune system?

Provides defense or immunity against infectious agents

What are some examples of infectious agents the immune system protects against?

Viruses, bacterial infections, fungal infections, and multicellular parasites

What type of cells make up the immune system?

Leukocytes (White Blood Cells)

Where are leukocytes found in the body?

In every tissue and specifically in lymphoid organs

Why is the study of the lymphatic system medically important?

It is crucial in understanding autoimmune diseases

What happens in autoimmune diseases?

The immune system attacks the body's own organs and defenses

What is the parenchyma of lymphatic tissue composed of?

Lymphocytes

What is the stroma of lymphatic tissue composed of?

Reticular tissue

What are the other cells found in lymphatic tissue?

Plasma cells, macrophages, neutrophils, eosinophils

What type of fibers support the cells in lymphoid tissues and organs?

Reticular fibers (Collagen Type III)

What special stain is needed to visualize reticular fibers under a microscope?

Silver impregnation stain

What is the function of reticular fibers in lymphoid tissue?

Support cells and allow mobility in some areas