Lymphatic and Immune Systems

Question 1

List the functions of the lymphatic system.

Answer 1

The lymphatic system is responsible for:

1. Immunity - the lymphatic system helps in filtering fluids from the capillaries; thus, filtering pathogens for excretions.
2. Lipid Absorption - lymphatic capillaries in the intestines filter lipids ingested from the diet
3. Fluid recovery - the lymphatic system absorbs fluids and plasma proteins from the body’s tissues and places them back in the bloodstream.

Question 2

Describe the ways in which lymph travels through the body.

Answer 2

Lymph travels through the body via lymphatic ducts. It flows slowly and at low pressure; therefore, it relies on rhythmic contractions of the lymphatic vessels, skeletal muscle pump, and through assistance from the rapid flowing blood in the subclavian veins. Lymph also relies on exercise/activity and the assistance of valves in the lymphatic vessels.

Question 3

Name and describe the difference between the two types of lymphatic cells.

Answer 3

T Lymphocytes (aka, killer T cells) are immature leukocytes that are stored in the thymus until they are needed. Once released by the thymus, they attack pathogens directly. They account for approximately 80% of lymphocytes circulating in the blood.
B Lymphocytes become active when an infection in detected in the body. They differ from T Lymphocytes in that they produce antibodies that attack the pathogen. They account for approximately 15% of lymphocytes circulating in the blood.

Question 4

List the lymphatic organs and provide a function of each.

Answer 4

Lymph nodes are the only lymphatic organs that filter lymph. They are located in various well defined locations of the body. They slow the flow of lymph and release lymphocytes in response to antigens.
Tonsils are located in three main areas of the pharynx (palatine, lingual, and pharyngeal). Collectively tonsils act to trap pathogens as they pass over the mucous membrane. Tonsils then destroy the pathogen deeming it harmless and release it into the lymph for excretion. 
The thymus houses T lymphocytes for future deployment against pathogens. As we age, the thymus becomes less active.
The spleen (having two regions) functions to produce blood in the fetus, as a blood reservoir, disposal point for erythrocytes, and as an immune response for detecting antigens.

Question 5

Our body has two main defenses against pathogens, nonspecific and specific. Describe the differences and provide an example of how each acts as a defense against pathogens.

Answer 5

Nonspecific defenses respond to external factors and have no memory of prior exposure. They are more membrane like barriers such as the skin, mucous membranes, and areolar tissue.
Specific defenses are those defense mechanisms we have in our body as a result of previous exposure (e.g., the chicken pox virus). This defense system has the ability to “remember” an antigen it was previously exposed, attack it when exposed again, and render it harmless.

Question 6

Why is the inflammatory response needed when tissue is injured?

Answer 6

The inflammatory response is needed to decrease the amount of further tissue damage (i.e., healthy tissue being destroyed) from pathogens being spread. It also removes debris as well as initiates tissue repair.

Question 7

What are the cardinal signs of inflammation?

Answer 7

Redness (caused by rapid influx of blood from broken blood vessels), swelling (as a result of capillary permeability and filtration), heat (caused by the “warm” blood entering the tissue area), and pain (caused by inflammatory chemicals such as histamines).