Lymph System

lecture chapter 4/4

What are the three main functions of the lymphatic system?

1. Return leaked interstitial fluids back to the bloodstream

2. Lymphoid cells protect against infections

3. Transport fats from the digestive tract to the bloodstream

Lymphatic Vessels & Transport

What creates pressure for lymphatic transport?

1. Smooth muscle in the walls of lymphatic vessels

2. Skeletal muscle

3. Contraction of nearby arteries

What prevents backflow of lymph?

Valves

• What is the function of lymphatic capillaries?

• What type of cells make up lymphatic capillaries?

• They collect fluid (lymph) from the tissue

• Simple squamous cells

• What is the structure of lymphatic capillaries?

• What opens lymphatic capillaries?

• They are blind-ended tubes

• Interstitial fluid pressure

• How are lymphatic capillaries different from blood capillaries in terms of permeability?

• What can lymphatic capillaries potentially transport?

• Lymphatic capillaries are more porous than blood capillaries

• Cancer cells

1. How are collecting lymphatic vessels similar to veins?

2. How do collecting lymphatic vessels differ from veins?

1. They are similar to veins in structure

2. They have:

• Thinner walls

• More valves

• More branching

• What are lymphatic trunks?

• What is the function of lymphatic ducts?

• They are formed by the union of lymphatic collecting vessels.

• They deliver lymph into the venous circulation

Where do lymphatic ducts deliver lymph into the venous circulation?

At the junctions of the internal jugular and subclavian veins

Primary Lymphoid Organs

What are the two primary lymphoid organs?

• Red bone marrow

• thymus

What are the functions of red bone marrow?

• Produces all blood cells

• Site of B lymphocyte maturation

What is the function of the thymus?

T lymphocyte maturation

• When is the thymus most active?

• What happens to the thymus during adolescence and with age?

• During childhood

• It stops growing during adolescence and atrophies with age

Secondary Lymphoid Organs — Lymph Nodes

• Where are lymph nodes located?

  • Where are large clusters of lymph nodes located?

• Hundreds are located along lymphatic vessels

  • Inguinal

  • Axillary

  • Cervical

• What is one major function of lymph nodes?

  • How do lymph nodes cleanse the lymph?

• They cleanse the lymph

  • Macrophages phagocytize cells and particles

• Why does lymph flow slowly through lymph nodes?

  • What is another major function of lymph nodes?

• Multiple afferent vessels and few efferent vessels result in a slow flow

  • Immune system activation

• What do lymph nodes house that helps activate the immune system?

  • What are lymphoid follicles?

• Lymphocytes that respond to foreign agents in the lymph

  • Areas in lymph nodes that house lymphocytes

• What happens to a lymph node during an immune response?

  • What is a germinal center?

• Multiplication of immune cells causes the lymph node to swell

  • A site where immune cells multiply during an immune response

Secondary Lymphoid Organs — Spleen

What is the major cleansing function of the spleen?

It cleanses the blood, similar to lymph nodes

What does the spleen remove from the blood?

Defective red blood cells and platelets

How does the spleen participate in immune system activation?

Similar to lymph nodes, it contains lymphoid follicles and germinal centers.

MALT — Tonsils

• What does MALT stand for?

  • What are the tonsils?

• Mucosa-associated lymphoid tissue

  • A type of mucosa-associated lymphoid tissue (MALT)

• Where are the tonsils located?

  • What are the three types of tonsils listed in the lecture?

• They form a ring around the pharynx

  • Pharyngeal (adenoids)

  • Palatine

  • Lingual

• What is the function of the crypts in the tonsils?

  • What are the crypts lined with?

• They trap foreign particles

  • Lymphoid follicles

MALT — Peyer's Patches

• What are Peyer's patches?

  • Where are Peyer's patches located?

• A type of mucosa-associated lymphoid tissue (MALT)

  • At the distal end of the small intestine

• What are Peyer's patches similar to?

  • What structures are associated with Peyer's patches in the lecture?

• The tonsils

  • Crypts of Lieberkühn

MALT — Vermiform Appendix

• What is the vermiform appendix?

  • What is the vermiform appendix similar to?

• A type of mucosa-associated lymphoid tissue (MALT)

  • Peyer's patches

Where is the vermiform appendix located?

It is a pouch extending from the caecum