The immune and lymphatic systems are two closely related organ systems that share several organs and physiological functions. The immune system is our body’s defense system against infectious pathogenic viruses, bacteria, and fungi as well as parasitic animals and protists. The immune system works to keep these harmful agents out of the body and attacks those that manage to enter.

The lymphatic system is a system of capillaries, vessels, nodes and other organs that transport a fluid called lymph from the tissues as it returns to the bloodstream. The lymphatic tissue of these organs filters and cleans the lymph of any debris, abnormal cells, or pathogens. The lymphatic system also transports fatty acids from the intestines to the circulatory system.

A femur cross-section, along with other living bones, consists of three layers: the periosteum, or outside skin of the bone; the hard compact bone; and the bone marrow. The femur is the thigh bone, the longest bone in the body.

The primary structures of the lymphatic and immune systems in the lower extremities are the lymph vessels. The large bones of the leg are also important, as these contain bone marrow that produces a large number of lymphocytes.

The primary structures of the lymphatic and immune systems in the upper extremities are the axillary nodes, which are located just under the armpit (some extend into the chest cavity as well) and the lymph vessels of the arm and hands, which move lymph throughout this region.

Peyer’s patches are small masses of lymphatic tissue found throughout the ileum region of the small intestine. Also known as aggregated lymphoid nodules, they form an important part of the immune system by monitoring intestinal bacteria populations and preventing the growth of pathogenic bacteria in the intestines.

The immune and lymphatic systems of the lower torso provides many vital functions to the body, including protection of the body from pathogens and the filtration and transportation of lymph, blood, and lipids. Many different structures, from red bone marrow in bones to the spleen, contribute to these processes.

A wide network of dozens of lymph nodes and countless lymphatic vessels spreads throughout the lower torso. This lymphatic network fulfills the important task of returning the interstitial fluid surrounding the tissues of the legs and lower torso to the blood supply. Interstitial fluid is absorbed by tiny lymphatic capillaries in the tissues, forming the fluid known as lymph. Many lymph nodes in the inguinal and iliac regions connect the lymphatic vessels of these regions and filter lymph as it is carried toward the upper torso. Pathogenic components (such as bacteria or viruses), cellular debris, dead cells, and even cancerous tumor cells are trapped by the lymph nodes and prevented from spreading through the body.

The mediastinal nodes are a group of lymph nodes located in the thoracic cavity of the body. These nodes play an important role in the filtration of lymph before it is returned to circulatory system.

The axillary nodes are a group of lymph nodes located in the axillary (or armpit) region of the body. They perform the vital function of filtration and conduction of lymph from the upper limbs, pectoral region, and upper back.

The axillary lymph nodes are a group of twenty to thirty large lymph nodes located in the deep tissues in and around the armpit. These nodes are arranged into five distinct groups: pectoral (anterior), lateral, subscapular (posterior), central (intermediate), and subclavicular (medial). Each group of lymph nodes receives lymph from a specific region of the body or from another group of lymph nodes.

The upper torso contains many important structures of the lymphatic and immune systems including many lymph nodes, the lymphatic ducts, thymus gland, and red bone marrow. These structures work together to perform the vital functions of producing immune responses to deadly pathogens; producing blood cells; transporting lymph and lipids; and filtering contaminants from lymph.

A vast network of lymph nodes and lymphatic vessels spreads throughout the diverse tissues of the upper torso. This lymphatic network performs the vital task of draining interstitial fluid from the tissues of the thorax and returning it to the blood supply. Many lymphatic vessels also carry lymph to the upper torso from the limbs, abdomen, head and neck.

The palatine tonsils are located at the back of the throat. One tonsil is located on the left side of the throat and the other is located on the right side. The tonsils play a role in protecting the body against respiratory and gastrointestinal infections.