BIO113 - Lymphatic System

What three factors influence speed of lymph flow?

1) "Milking" action of muscles on lymph vessels 2) Presence of valves which prevent backflow 3) Effect of negative pressure on thoracic duct during inspiration *The amount of lymph produced can also be a factor - when blood flow in veins is slow, more lymph is produced.

In what two ways is the lymphatic system related to the circulatory system?

1) Anatomically 2) Functionally

What are the three primary functions of the lymphatic system?

1) Destruction of bacteria and removal of foreign substances from lymph 2) Specific Immune Responses 3) Return of the tissue fluid and plasma proteins to blood (which prevents edema)

What are the three types of tonsils and where are they located?

1) Palatine (located on either side of the throat) 2) Pharyngeal (adenoids on wall of nasopharynx) 3) Lingual (dorsal surface of tongue near base)

What are the three main functions of the spleen?

1) Primarily functions as a lymph gland and filters old RBC's out of circulation 2) Serves as a reservoir of blood (red pulp contains 350 ml and after hemorrhage about 200 ml can be forced into circulation) 3) In embryo, forms RBC's (this function is lost unless a person suffers from severe hemolysis)

What are the other three lymphoid organs of the body?

1) Spleen 2) Thymus Gland 3) Tonsils

What are the two large lymph ducts in the body?

1) Thoracic Duct (this drains for most of the body) 2) Right Lymphatic Duct (this drains for right head shoulder, chest and arm)

How much lymph is emptied into the heart in 24 hrs?

2 to 4 liters.

Describe the lifespan of the thymus gland...

At birth it is the main producer of lymphocytes. It increases in size in early childhood and atrophies after puberty (and is eventually replaced by fatty tissue).

What is lymph?

Blood plasma, less formed elements. It is termed "lymph" the moment it enters the lymphatic system.

What are lymph capillaries?

Fluid enters the lymphatic system through these vessels. They are permeable to plasma proteins, and are located near vascular capillaries.

What are the specific immune responses of the lymph nodes?

In the presence of an antigen (i.e. bacteria), B cells within the lymph nodes become plasma B cells which make antibodies to destroy that antigen.

Where is the Thoracic Duct located?

It arises from an enlargement known as the cysterna chyli and empties into the left subclavian vein.

Where does the Right Lymphatic Duct drain?

It empties into the right subclavian vein.

What are the physical characteristics of the thymus gland?

It is located behind the sternum and is internally constructed like a lymph node. It contains tightly-packed lymphocytes.

What are the physical characteristics of the spleen?

It is located next to the stomach and the size and weight varies. It is constructed like a large lymph node.

What happens to most of the interstitial fluid?

It re-enters the bloodstream (but the plasma proteins are too large to re-enter and more fluid leaves than re-enters).

What are afferent lymph vessels?

Lymph enters the nodes through these vessels.

What are efferent lymph vessels?

Lymph leaves the nodes through these vessels.

Lymphatic capillaries join to form what?

Lymphatic vessels - these run alongside veins and pass through one or more lymph nodes before emptying into one of two main lymph ducts. The vessel walls are similar to veins, and contain valves to prevent backflow.

Why might lymph nodes be removed as a treatment for cancer?

Metastasizing cells tumor cells may be caught by the phagocitic cells in the lymph nodes.

What direction does the lymphatic system flow?

One-way - from tissues to heart.

What are the two types of splenic pulp?

Red splenic pulp and white splenic pulp

What are lymph nodes?

Small round/bean-shaped masses of lymph tissue distributed throughout the lymphatic system.

Why is lymph flow slower than blood flow?

There is no pump for the lymphatic system.

What are lymph nodes composed of?

They are enclosed in a fibrous capsule, and inward extensions (trabiculae) divide the interior into sections. There are reticular fibers inside containing lymphocytes and macrophages, which remove foreign substances fro lymph and prevent them from re-entering the bloodstream.

What is red splenic pulp?

This is the most abundant within the spleen and contains lymphocytes, macrophages, and red blood cells.

What is white splenic pulp?

This surrounds the arterioles - it has the same make-up as red splenic pulp, but lacks RBC's.

What is interstitial fluid?

Tissue fluid - this is blood plasma which has left the bloodstream at the capillaries.