Question

How does the lymph leave the body?

Answer 1

Hint: The lymphatic system comprises a colourless fluid tissue called lymph. We all know that lymph is a clear, transparent, sometimes faint yellow and slightly opalescent fluid that is formed from interstitial fluid. It plays a major role in conveying the material from the tissue cells into the blood.

Complete answer:
The lymph is tissue fluid that slowly drains into the lymphatic capillaries from the intercellular spaces present between the tissue cells. It consists of two parts: the fluid matrix, the plasma, in which it floods amoeboid cells, the white blood corpuscles, or leukocytes, but receives them as it passes through the lymphatic nodes.
About 99% of the corpuscles are lymphocytes and the remaining 1% include eosinophils and monocytes, and occasional erythrocytes. The lymph is rich in waste products, that from the intestine is milky and rich in fat globules and that from the liver is rich in proteins.
The lymph is slowly moved through the lymphatic vessels by several factors. Forcing out of fluid from the blood capillaries sets up some pressure in the tissue fluid. This establishes a pressure gradient in the lymphatics, causing flow of lymph into them. Movements of the viscera, contractions of the body muscles, and pulsations of the lymph heart help considerably in squeezing the lymph along. The valves present in the lymphatics prevent its backflow. Movement of the villi assists the flow of lymph in the lacteals.
Some vertebrates, namely amphibians and reptiles, have small, pulsatile lymphatic hearts which propel the lymph through the lymph vessels. The lymphatic system is closed as the blood vascular system but unlike the latter, it does not form a complete circuit in itself.

Note:
The lymphatic vessels develop in the embryo-like and close to the blood vessels. They first appear as fluid- filled spaces in mesenchyme. These cells of mesenchyme surrounding the spaces become flattened and differentiate into the endothelial cells that line these vessels. These vessels then fuse and branch, forming a continuous system of anastomosing vessels.