Lymphatic circulation, drained

By definition, chylomicrons are found in chyle formed only by the lymphatic system draining the intestine. They are responsible for the transport of all dietary lipids into the circulation. Small quantities of VLDL... 

The fluid in the lung tissues may drain either toward the pleura or toward the center of the thoracic cavity (Fig. 3.5). The pleural fluid returns through the lymphatics to the central thoracic cavity, where a duct opens into the venous circulation. Thus, the fluid transported from lung tissue is returned to the systemic blood circulation by the lymphatics. Alternatively, fluid can be transported directly by and into the central lymphatic system. 

A percentage of xenobiotics absorbed in the gastrointestinal cells may be biotransformed prior to entering the circulatory system the balance is transported as the parent compound. The absorbed compounds may enter the circulation either via the lymphatic system, which eventually drains into the bloodstream, or via the portal circulation, which carries them to the liver. 

Because the BBB prevents the effective accumulation of many of the antivirals, the CNS can act as a reservoir of virus. This reservoir could potentially reinfect the peripheral tissues. The CNS-to-blood movement of HTV-1 has not been investigated, but movement of two of its proteins has been. The coat glycoprotein gpl20 is cleared by non-saturable mechanisms (Cashion et al., 1999). However, it has a propensity to be reabsorbed predominately by nasal drainage. As a result, it drains by way of lymphatic vessels directly to the cervical lymphatic nodes. If whole virus also takes this route, then that means that lymph nodes could be directly reinfected without the virus having to enter the circulation where it could be exposed to antiviral agents. 

Lymphatic vessels are made up of single-cell epithelial layers that drain fluid away from tissue. Smooth muscles controlled by the autonomic nervous system direct the fluid away from tissues toward the lymph nodes and, eventually, the heart. The vessels contain one-way valves that close behind fluid traveling back to the heart so that lymphatic fluid cannot go backward. Lymphatic fluid is usually returned to the circulation within 24 hours. When the lymphatic vessels become clogged, stopped up, or blocked, severe edema (bloating due to water retention) can result in a condition known as lymphedema. 

As shown in Figure 4.2, each villus has both blood capillaries, which drain into the hepatic portal vein, and a lacteal, which drains into the lymphatic system. Water-soluble products of digestion (carbohydrates and amino acids) are absorbed into the blood capillaries, and the liver has a major role in controlling the availability of the products of carbohydrate and protein digestion to other tissues in the body. As discussed in section 4.3.3.2, lipids are absorbed into the lacteals the lymphatic system joins the bloodstream at the thoracic duct, and extrahepatic tissues are exposed to the products of lipid digestion uncontrolled by the liver, which functions to clear the remnants from the circulation. 

Lymphatic system The main function of the lymphatic system is to extract, transport, and metabolize lymph, which is the fluid found in between cells. It is a defense system for the body, filtering out organisms that cause disease, producing white blood cells, and generating disease-fighting antibodies. It also distributes fluids and nutrients in the body, and drains excess fluids and protein so that tissues do not swell. The lymphatic system is made up of a network of vessels that help circulate body fluids. These vessels carry excess fluid away from the spaces between tissues and organs and return it to the bloodstream. 

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