Lymphatics & Immune System

What is the primary function of the lymphatic system?

To return fluids that have leaked from blood vessels back to the blood.

What are the three main components of the lymphatic system?

Network of lymphatic vessels, lymph (fluid), and lymph nodes.

What is lymph?

Fluid that enters the lymphatic vessels after interstitial fluid is collected.

What types of vessels make up the lymphatic system?

Lymphatic capillaries, lymphatic collecting vessels, lymphatic trunks and ducts.

How much fluid does the lymphatic system return to the blood each day?

Approximately 3 liters.

What are lymphatic capillaries?

Tiny vessels that collect lymph fluid and are highly permeable.

What do the endothelial cells of lymphatic capillaries form?

One-way mini-valves.

What specialized lymphatic capillaries absorb fats in the intestinal mucosa?

Lacteals.

What is the role of collecting lymphatic vessels?

To transport lymph from capillaries to lymphatic trunks.

What are lymphatic trunks formed by?

The union of the largest collecting vessels.

What does the right lymphatic duct drain?

The right upper arm and the right side of the head and thorax.

What does the thoracic duct drain?

The rest of the body not covered by the right lymphatic duct.

What is the main component of lymph fluid?

Water, carbohydrates, fats, and proteins.

What are the three types of leukocytes found in lymph fluid?

Lymphocytes, macrophages, and dendritic cells.

What do B cells differentiate into upon activation?

Plasma cells or memory cells.

What is the function of plasma cells?

To secrete antibodies that target antigens.

What do T cells do?

Manage the immune response and destroy affected cells.

How do macrophages aid the immune response?

By engulfing pathogens and presenting antigens to T cells.

What is the role of dendritic cells?

To capture antigens and activate T cells in the lymph nodes.

What do reticular cells produce?

Reticular fiber stroma that supports other cells in lymphoid organs.

How is lymph transported through the lymphatic system?

By the milking action of skeletal muscles, pressure changes during breathing, arterial pulsations, and contractions of smooth muscle in lymphatic walls.

What are lymphoid tissues?

Collections of lymphocytes not organized into distinct organs.

What are the two main types of lymphoid tissue?

Diffuse lymphoid tissue and lymphoid follicles/nodules.

Where is diffuse lymphoid tissue commonly found?

In almost every body organ.

What is the function of lymphoid follicles/nodules?

To contain germinal centers where B cells proliferate and differentiate.

What are lymph nodes?

Principal lymphoid organs that filter lymph and activate the immune system.

What functions does the spleen perform?

Removing old RCBs, storing breakdown products, filtering pathogens, and serving as a site for lymphocyte proliferation.

Where is the thymus located?

In the inferior neck, extending into the mediastinum.

What is the unique function of the thymus?

It is important for T lymphocyte maturation and does not fight antigens directly.

What does MALT stand for?

Mucosa-Associated Lymphoid Tissue.

What is the role of tonsils?

To gather and remove pathogens in food or air.

What is the primary function of Peyer's patches?

To monitor intestinal bacteria and generate memory lymphocytes.

What is the appendix theorized to help with?

Providing a safe house for commensal bacteria.

What does the immune system provide?

Lines of defense against foreign material, bacteria, viruses, and cancer.

What is immunity?

The resistance to disease.

What constitutes the innate defense system?

The surface barriers and internal defenses that respond to pathogens immediately.

What makes up the first line of defense?

Surface barriers such as skin and mucous membranes.

What is the main function of enzymes in surface barriers?

To breakdown or kill microorganisms.

What are defensins?

Antimicrobial peptides that inhibit microorganism growth.

How do NK cells contribute to the immune response?

By destroying altered self-cells and inducing apoptosis in infected or cancerous cells.

What are the cardinal signs of inflammation?

Redness, heat, swelling, pain, and impairment of function.

What is the role of exudate in the inflammatory response?

To provide nutrients for healing, contain pathogens, and create a barrier to prevent spread.

What do interferons do?

Warn neighboring cells of viral infections and activate NK cells.

What triggers a fever?

The secretion of pyrogens by leukocytes and macrophages in response to foreign substances.

What is the role of the adaptive defense system?

To target particular foreign substances through specific responses initiated by lymphocytes.

What are antigens?

Substances that can mobilize adaptive defenses and provoke an immune response.

What do antibodies do?

Bind to antigens and can neutralize threats or mark them for destruction.

What is the function of antigen-presenting cells (APCs)?

To engulf antigens and present their fragments to T cells.

What types of immunity do B and T cells provide, respectively?

B cells provide humoral immunity; T cells provide cellular immunity.

What happens when a B cell is activated?

It divides into plasma cells and memory B cells.

What is the role of CD4 T cells?

To act as helper T cells that enhance the immune response.

What is the role of CD8 T cells?

To become cytotoxic T cells that directly kill infected cells.

What are the steps to adaptive defenses?

Origin, maturation, seeding secondary lymphoid organs, antigen encounter & activation, proliferation & differentiation.

How do memory cells contribute to the immune response?

By allowing a quicker response to previously encountered antigens.

What do B cells develop into upon activation?

Plasma cells and memory B cells.

What triggers the immune response in T lymphocytes?

Binding of their cell receptor to an antigen presented by an APC.

What cells can act as antigen-presenting cells?

Dendritic cells and macrophages.

What is the role of the spleen in the immune system?

To filter blood and house lymphocytes.

What mechanism do phagocytes use to destroy pathogens?

Phagocytosis.

How is lymph fluid ultimately returned to the bloodstream?

By being drained into the venous circulation through lymphatic ducts.

What is the distinguishing feature of lymphatic capillaries compared to blood capillaries?

Lymphatic capillaries are more permeable.