Lymph - Anatomy & Physiology

Introduction

Lymph, a fluid, is formed from interstitial fluid that is filtered into the lymph vessels. Lymph is transported through lymphatic vessels before eventually reentering the blood stream. Lymph transports lymphocytes and triacylglcerides.

Formation

Lymph is formed by the filtration of interstitial (tissue) fluid into lymphatic capillaries. As fluid enters the tissue space from the blood stream, pressure builds up in this space and as this hydrostatic pressure increases it causes the interstitial fluid to diffuse into the lymphatic capillaries once the interstitial fluid has entered the lymphatic capillaries it is called lymph.

Composition

Lymph has a similar composition to blood plasma and when initially formed lymph is a relatively colourless. Depending on where the lymph travels the lymph will contain different concentrations of lymphocytes, proteins and fats. The concentration of lymphocytes is highest in lymph after it has passed through lymph nodes, and lymph formed in the alimentary tract has a high concentration of fats.

Circulation

Lymph travels unidirectionally from tissue into the blood stream via lymphatic capillaries which join to form vessels and these then join to form ducts. As there is no central pump lymph is moved through the vessels via compression of the vessels by skeletal muscle contraction. All lymph passes through lymph nodes before it reenters the blood stream. Further details of the lymphatic vessels can be found here.

Originally funded by the RVC Jim Bee Award 2007