Red bone marrow, thymus, spleen, tonsils, lymph nodes, lymphocytes, lymph nodules, lymph and lymph vessels make up the human lymphatic system. Identifying and defending the body from foreign substances and microorganisms, maintaining fluid balance within body tissues and absorbing lipids, proteins and fat-soluble vitamins from the small intestines are some of the major functions of the lymphatic system. (Marieb)Lacking a pumping organ, the lymphatic system utilizes smooth muscles along lymphatic trunks wall and skeletal muscles contraction, pulsation of surrounding arteries and contraction of the thoracic cavity during breathing to move the lymph through the vessels. (Foeldi and Foeldi) This paper will discuss the how lymph originates from plasma and the pathway of lymph back to the venous system
Lymph is a clear fluid found in the lymphatic capillaries that originates from plasma mainly composed of proteins, water, fat, cells and waste products and foreign body. Large volumes of lymph is produced in the liver whose lymphatic system can be divided into three divisions: superficial, polar, sublobular vessels. Arterial blood that flows out of the heart moves slowly through a bed of capillaries thus allowing some plasma to slowly filter, by colloid osmotic and hydrostatic pressures, into the tissues through the arterioles hence becoming tissue fluid. (Foeldi and Foeldi)Delivering nutrients, hormones and oxygen to the cells the tissue fluid flows between the cells and about 90% of the fluid flows into venous circulation carrying protein cells and waste products and continues into the human circulatory system as plasma while the remaining fluid left in the lymph capillaries is referred to as lymph. Chyle, intestinal lymph, has a milky color due to the absorption of fat in the intestinal trunk hence giving the intestinal lymph vessels a cloudy appearance.
Lymph pathway is a one-way current to the base of the neck region from the intestinal area. Lymphatic capillaries surrounding most of the tissues cells and blood capillaries found in connective tissues allow lymph to flow into larger channels known as collecting lymphatic vessels that unite to form trunks. (Foeldi and Foeldi) These trunks include: single intestinal trunk, to the cisterna chyli from the small intestines, and paired broncomediastinal, lumbar, jugular and subclavian trunks. Left and right lumbar trunks to the cisterna chyli from the inguinal lymph nodes.
The filtered lymph forms part of the venous blood in the circulatory system when it enters the venous blood system through the thoracic or right lymphatic ducts found in the subclavian and internal jugular veins located at the base of the neck. (Marieb)Lymph from the right upper limb, thorax and right side of the head drains via right lymphatic duct while the thoracic duct, largest lymphatic vessel, drains lymph from the rest of the body. (Foeldi and Foeldi)Where else intestinal trunk drains lymph from the digestive organs and cisterna chyli, an enlarged sac that makes up the thoracic duct abdominal portion, collects lymph drained from the lower limbs via the two lumbar trunks.