Immune and lymphatic system physiology

Immune and Lymphatic System Physiology

Lymph Circulation

One of the primary functions of the lymphatic system is the movement of interstitial fluid from the tissues to the circulatory system.
              

Like the veins of the circulatory system, lymphatic capillaries and vessels move lymph with very little pressure to help with circulation. 

Transport of Fatty Acids

Another major function of the lymphatic system is the transportation of fatty acids from the digestive system.

The digestive system breaks large macromolecules of carbohydrates, proteins, and lipids into smaller nutrients that can be absorbed through the villi of the intestinal wall.

In the villi of the small intestine are lymphatic capillaries called lacteals.

Lacteals are able to absorb fatty acids from the intestinal epithelium and transport them along with lymph. The fatty acids turn the lymph into a white, milky substance called chyle.




Types of Immunity

The body employs many different types of immunity to protect itself from infection from a seemingly endless supply of pathogens. These defenses may be external and prevent pathogens from entering the body.
Innate Immunity

The body has many innate ways to defend itself against a broad spectrum of pathogens. These defenses may be external or internal defenses.
External Defenses

The coverings and linings of the body constantly prevent infections before they begin by barring pathogens from entering the body.
Epidermal cells are constantly growing, dying, and shedding to provide a renewed physical barrier to pathogens.

Stomach acid acts as a chemical barrier to kill microbes found on food entering the body. 



Internal Defenses

Fever. In response to an infection, the body may start a fever by raising its internal temperature out of its normal homeostatic range.

Inflammation. The body may also start an inflammation in a region of the body to stop the spread of the infection.

Natural Killer Cells. Natural killer (NK) cells are special lymphocytes that are able to recognize and kill virus-infected cells and tumor cells.

Phagocytes. The term phagocyte means “eating cell” and refers to a group of cell types including neutrophils and macrophages.

Cell-mediated Specific Immunity. When a pathogen infects the body, it often encounters macrophages and dendritic cells of the innate immune system.

Antibody-mediated Specific Immunity. During an infection, the APCs that travel to the lymphatic system to stimulate T cells also stimulate B cells.

Plasma cells. Plasma cells become antibody factories producing thousands of antibodies.

Acquired Immunity. Under most circumstances, immunity is developed throughout a lifetime by the accumulation of memory T and B cells after an infection.