Lymph is a fluid that travels through its own kind of circulatory system. The lymphatic system as a whole helps maintain distribution of fluids and maintain blood composition. Plasma from blood leaks out of capillaries and gets collected and redistributed by the lymph system. It also transports other molecules, like proteins, triglycerides, and white blood cells. You would not expect to find a red blood cells in this fluid, as they do not leak out of veins and capillaries.

The lymph is collected in the periphery from the fluid that is not reabsorbed by oncotic pressure in the capillary beds. Proteins (including the main blood component albumin), chylomicrons (collected from enterocytes in the liver), and water are all parts of lymph. These components can exit the capillary walls in areas of significant hydrostatic pressure, and enter the lymph to avoid being trapped in the interstitium.

Red blood cells are too large to pass through capillary walls, and thus would not be released into the interstitium or absorbed into the lymphatic system.

All of the following are parts of the lymphatic system, except the liver. The liver is considered to be primarily a part of the digestive system. 

In the lymph node, the B-cells are located in the cortex and the T-cells are located in the medulla. The stromal cells are structural cells that are not particular to an area of the lymph node. Dendritic cells will move through the lymph node to present antigens to the adaptive immune system cells.

Primary lymphoid tissues refer to the tissues where lymphoid cells are generated, while secondary lymphoid tissues are the functional organs of the lymphatic system.

Lymphocytes are generated and developed in the bone marrow and thymus only. The spleen and lymph nodes are examples of secondary lymphatic organs.

The spleen has two main functions. The first main function is immunological, while its second function is to filter unhealthy (senescent) red blood cells.

Most digestive enzymes are secreted by the pancreas into the small intestine. Systemic hormones come from a variety of glands throughout the body; the spleen does not have an endocrine function. White blood cells are synthesized in bone marrow and mature in the marrow and thymus. Serum proteins are synthesized in the liver.

The thymus is a lymphoid organ located in the mediastinal space. The thymus is the site of T-lymphocyte differentiation. The mature T-cells leave the thymus and migrate to the spleen, lymph nodes, and other lymphoid tissues where they control cell-mediated immune responses. The thymus grows from birth to puberty, at which point it begins to shrink. The reason for this involution may be that the organ has produced enough T-cells and is no longer necessary.

The spleen is another lymphocyte-producing organ. The spleen filters blood, exposing it to lymphocytes that destroy foreign particles. The size of the spleen remains constant, except in cases of infections such as mononucleosis. The tonsils are a patch of lymphoid tissue that contain lymphocytes located in the pharynx. The tonsils and adenoids form a ring of immunologically active tissue. These tissues remain at a constant size except when infected by bacteria. Lymph nodes receive lymph from a single organ or region of the body. An increase in size, known as lymphadenopathy, could result from combating infection or cancer. 

The spleen forms erythrocytes (red blood cells), and leukocytes (white blood cells, including lymphocytes) during the embryonic stage. After birth, only lymphocytes are produced.

The tonsils and adenoids are patches of lymphoid tissue located in the pharynx that filter pathogens that enter the body through the mouth and nose. Lymph nodes produce lymphocytes in response to infections by pathogens. The thymus is an organ that produces lymphocytes in infants and young children. 

The surface of each tonsil is covered with stratified squamous epithelium, which forms deep crypts that detect and respond to pathogens entering the body. The tonsils are located on either side of the throat at the back of the tongue.

Adenoids are lymphoid tissue located in the nasopharynx, in the midline at the back of the throat. The spleen is in the upper left quadrant of the abdomen. The spleen has a smooth surface, as it is covered by an outer capsule of connective tissue. The thymus is in the mediastinum between the lungs. The thymus is composed of two lobes containing multiple lobules divided into an outer cortex and an inner medulla. The thymus is the site of T-cell differentiation. Lymph nodes filter lymph and remove foreign particles. Lymph nodes are located throughout the body, and are concentrated in the neck, axilla, and groin. 

Lymph nodes function to drain lymph. As lymph carries interstitial fluid, it also carries pathogens and cancer cells. Malignant cells may spread through the lymphatic circulation.

Tonsils and adenoids are collections of lymphoid tissue in the pharynx that filter microbes that enter through the mouth and nose. They enlarge during infectious processes. The spleen filters blood, exposing it to macrophages and lymphocytes that destroy foreign particles and aged blood cells. The thymus is the primary site for T-cell differentiation. The mature T-cells leave the thymus and travel to the spleen, lymph nodes, and other lymphoid tissue where they control cell-mediated immune responses.