Lymphatic System (ch.20)

What is the main function of the lymphatic system?

The lymphatic system returns fluids leaked from blood vessels back to the blood.

What are the primary lymphoid organs of the immune system?

Red bone marrow and thymus.

What structures make up the lymphatic system?

Spleen, thymus, tonsils, lymph nodes, and other lymphoid tissues.

What type of vessels do lymphatic capillaries resemble but are more permeable?

Blood capillaries.

What are minivalves in lymphatic capillaries?

Specialized structures that allow for increased permeability and the flow of lymph toward the heart.

What specialized lymph capillaries are found in the intestinal mucosa?

Lacteals.

What do lacteals absorb?

Digested fat and deliver fatty lymph (chyle) to the blood.

What is the role of collecting lymphatic vessels?

They drain lymph capillaries into increasingly larger vessels.

What are lymphatic trunks?

Large lymphatic vessels formed by the union of collecting lymphatic vessels.

What areas do the lumbar trunks drain?

Lower back.

What lymphatic duct drains the right side of the head and thorax?

Right lymphatic duct.

Which lymphatic duct drains the rest of the body?

Thoracic duct.

How is lymph transported through the lymphatic system?

Lymph is moved by milking action of skeletal muscles, pressure changes in thorax during breathing, valves to prevent backflow, pulsations of nearby arteries, and contractions of smooth muscle in walls of lymphatics.

What is lymphedema?

Severe localized edema caused by anything that prevents normal return of lymph to blood.

What are the two main types of lymphocytes?

T cells (T lymphocytes) and B cells (B lymphocytes).

What is the function of T cells?

Manage immune response and attack and destroy infected cells.

What do B cells produce?

Plasma cells that secrete antibodies.

What role do macrophages play in the lymphatic system?

Phagocytize foreign substances and help activate T cells.

What is the primary function of lymphoid tissue?

Houses and provides proliferation sites for lymphocytes.

What is the structure that supports immune cells in lymphoid organs?

Stroma (reticular fibers).

What are the principal secondary lymphoid organs?

Lymph nodes.

What happens in the lymph nodes?

Lymph is cleansed and lymphocytes are activated to mount an immune response.

Where do afferent lymphatic vessels carry lymph?

Into the convex side of the lymph node.

What type of cells capture antigens in lymph nodes?

Dendritic cells.

What is the main function of the spleen?

Site of lymphocyte proliferation and immune surveillance, cleanses blood of aged cells and platelets.

What are the two components of the spleen?

White pulp (immune function) and red pulp (destruction of old blood cells).

What is MALT?

Mucosa-associated lymphoid tissue.

Where are the tonsils located?

Around the pharynx.

What do Peyer's patches do?

Destroy bacteria and generate memory lymphocytes in the small intestine.

What is the thymus responsible for?

Maturation of T cells.

What keeps immature T lymphocytes isolated in the thymus?

Blood-thymus barrier.

What do reticular cells produce in lymphoid organs?

Reticular fibers that form the stroma.

What happens to the thymus after adolescence?

It stops growing and gradually atrophies.

Where in the lymph node do the T cells first encounter antigens presented by dendritic cells?

deep in the cortex

What is the name of the enlarged sac to which the lumbar trunks and the intestinal trunk return lymph?

Cisterna Chyli

Where are the three large clusters of superficial lymph nodes?

cervical, axillary, inguinal regions