Lymphatic Objectives

• Identify the structures of the Lymphatic System
• Describe the roles the Lymphatic System plays in the body
• Identify the locations of the lymphatic system in the body

Lymphatic Anatomy

Major Roles:

The lymphatic system has three major roles it plays in the human body, they are:

• Returns excess interstitial fluid to the blood. Only 90 percent is returned to the blood. The other 10 percent that doesn't return then becomes part of the interstitial fluid that surrounds the tissue cells.
  • Small protein molecules can seep through the capillary walls and increase the osmotic pressure of the interstitial fluid. If this does occur it will further inhibit the return of the flood into the capillaries and fluid will tend to accumulate in tissue spaces. If this continues to occur the blood volume and pressure will decrease significantly and the volume of tissue fluid increases resulting in edema.
    

• Absorption of fats and fat-soluble vitamins from the digestive system and the subsequent transport of these substances to the venous circulation.
  • Mucosa that lines the small intestine is covered with small finger like projections called villi. There are blood capillaries and special lymph capillaries in each of these villi called lacteals. The blood capillaries absorb most of the nutrients except for the fats and fat-soluble vitamins which are absorbed by the lacteals. The lymph in lacteals are a milky white color due to the high fat content and are called chyle.
    

• Most well known part the defense against microorganisms and diseases.T and B Lymphocytes and White Blood Cells and Antibodies are some of the defense team in our body. These cells are pdocuded in our red bone marrow and mature in the Thymus, which is an accessory organ in our defence system.
  
• The Importance of the Lymphatic System
• The study of lymphatic drainage of various organs is important in diagnosis and treatment of cancer. The lymphatic system, because of its physical proximity to many tissues of the body, is responsible for carrying cancerous cells between the various parts of the body in a process called metastasis. The intervening lymph nodes can trap the cancer cells. If they are not successful in destroying the cancer cells the nodes may become sites of secondary tumors.

Anatomy and Structures:

• The Lymphatic system consists of ducts, organs and nodes.
• Lymph is a fluid similar to the composition of blood plasma. When interstitial fluid enters the lymph capillaries that is when it is called "Lymph".
• Lymph distributes immune cells such as lymphocytes throughout the body.
  
• Lymphatic vessels only carry fluid away from tissue unlike regular blood vessels.
• Fluid will run through the system several times successively to cleanse it and to check for foreign cells.
  
• Lymphatic organs are characterized by clusters of lymphocytes and other cells enmeshed in a framework of short branching connecting tissues. There are lymph nodes and lymph ducts in the connecting tissues.
  

Lymphocytes:

• Originate in the red blood marrow with other types of cells and are carried from the bone to the lymphatic organs.
  
• Lymphocytes proliferate within the lymphatic organ when the body is exposed to microorganisms and other foreign substances and are sent in the blood to the site of the invasion.
  • This is part of the immune system response to destroy any harmful invading microorganisms; protects the body against antigens.
    
  

Lymph Nodes

A lymph node is an organized collection of lymphoid tissue, through which the lymph passes before passing through the lymph duct on its way to returning to blood. Lymph nodes are located at intervals along the lymphatic system. Several afferent lymph vessels bring in lymph, which percolates through the substance of the lymph node, and is drained out by an efferent lymph vessel.


Lymphatic Capillaries
In order to leave the tissues, the lymph must enter the lymphatic system through specialized lymphatic capillaries which are located just under the skin. These begin as blind-ended tubes that are only a single cell in thickness. These cells are arranged in a slightly overlapping pattern, much like the shingles on a roof. As shown in this animation, pressure from the fluid surrounding the capillary forces these cells to separate for a moment to allow lymph to enter the capillary. Then the cells of the wall close together. This does not allow the lymph to leave the capillary but forces it to move forward.

Spleen

The spleen is the largest organ of the lymphatic system that cleans and stores blood. It is a deep red colored organ and can vary considerably in size and weight. It is Located in the left upper abdominal quadrant, inferior to the diaphragm and adjacent to ribs 9 through 11 and lies lateral to the left kidney and posterolateral to the stomach. The posterolateral aspect of the spleen (called the diaphragmatic surface) is convex and rounded. While the visceral surface contains hilum, where blood vessels and nerves enter and leave the spleen.

Glossary

Lacteals- fats and vitamins pass through here in the small intestines and drain into larger lymphatic vessels and eventually the bloodstream.
Antigens- are any substances perceived as abnormal to the body such as bacteria, viruses, and even cancer cells.
Antibodies-proteins that bind to and immobilize the foreign or abnormal agent thus damaging it or identifying it to other elements of the immune system.
Lymph- liquid mixture of solutes, interstitial fluid and foreign material similar to blood plasma.
Tonsils- are large clusters of lymphatic cells and extracellular matrix that are not completely surrounded by a connective tissue capsule. Tonsils are found in the pharynx. "Pharyngeal tonsils" are known as adenoids are in the posterior wall of the pharynx. Adnoids usually shrink as you age but if not, they may reduce the flow of air while you sleep. "Palatine tonsils" are in the posterolateral of the oral cavity. These are the two in the back of the throat that you can see. With infection or irritation they can become red and full of pus. "Lingual tonsils" which are along the posterior one-third of the tongue.

Connections to other body systems

The lymph helps filter the blood and aids in the immune system of the body.

• This system collects excess tissue fluid and plays a role in absorbing fats and transporting lymph to cardiovascular veins.
  
• It also purifies lymph and stores lymphocytes, the white blood cells that produce antibodies. Lymph vessels are closely associated with the circulatory system vessels. Larger lymph vessels are similar to veins. Lymph capillaries are scattered throughout the body.
• Contraction of skeletal muscle causes movement of the lymph fluid through valves.

Tonsils are located in the oral cavity which where the first process of the digestive system occurs.
Lymph movement: The pressure gradients of the lymph through vessels comes from the skeletal muscle action, respiratory movement and contraction of the smooth muscle in vessels wall

Lymphatic Review

1. What is the largest lymphatic organ in the body?
a. pancreas
b. gall bladder
c. *spleen
d. liver

2. What are the primary functions of the Lymphatic System?
a. transport nutrients
b. develop lymphocytes
c. cause an immune response
*d. all the above

3. What does B-lymphocytes produce?
a. antibodies
b. antigens
c. cancer cells
d. T-cells

4. What are the special types of lymphatic capillaries in the small intestine called?
a. Lacteals
b. Rugae
c. Fundus
d. Pylorus

5. We know that B and T lymphocytes are produced in the bone marrow, where do the T cells actual mature?
a. In Bone
b. In Blood
c. In the Lymph nodes
*d. In the Thymus

6. The Lymphatic System transports what?
a. blood
b. waste from cell metabolism
c. plasma back to blood
*d. interstitial fluid back to the blood

7. Obstruction in the lymphnodes can cause
a. edema
b. the lymph nodes to become enlarged
c. lymphedema
d. all the above

8. Lymph in the Lacteals have a milky white appearance due to the high fat content and are called ______?
*a. Chyle
b. Chime
c. Sanies
d. Serum

9. Of the fluid that leaves the capillaries, about ___ percent is returned. The other __ percent that doesn't return becomes part of the interstitial fluid that surrounds the lymph.
a. 80, 20
b. 70, 30
*c. 90, 10
d. 75, 25

10.
a.
b.
c.
d.