The system which is responsible for the circulation of the lymph from the tissue
spaces (intercellular spaces) to the blood stream. The lymph is a clear colorless fluid,
rich in proteins, which circulates in the lymph vessels.
Lymphatic system consists of 3 parts:
a- Lymph vessels.
b- Lymphoid tissues as lymph nodes, spleen, tonsils and thymus.
c- Free cells (lymphocytes).
Lymph Vessels:
They are closed end fine vessels present in the tissue spaces uniting together to form
larger lymph vessels which join the lymph nodes. All the lymph vessels in the body
are collected into 2 large lymph ducts in the root of the neck, they are:
A- Thoracic duct drains the left side of head, neck and left upper limb, left half of
thorax and whole body below diaphragm.
B- Right lymphatic duct drains the right side of head and neck, right half of thorax
and right upper limb.
The 2 ducts open into 2 large veins present at the root of the neck.
Spleen
Position: Wedge-shaped organ lies in the upper left part of the abdominal cavity,
below the diaphragm deep to the 9th, 10th and 11th ribs.
Lymph Nodes
Lymph nodes are oval or kidney-shaped small bodies situated along the course of
lymph vessels. Lymph node consists of cortex and medulla.
They are present in groups in special and fixed sites, they are:
A- In the neck, on both its sides and at its junction with the head.
B- In the chest, close to trachea and bronchi.
C- At the root of upper limb (in axillary lymph nodes).
D- In the abdomen: Around abdominal aorta and close to abdominal organs.
E- In the pelvis: Around blood vessels of pelvis and close to pelvic organs.
F- Root of lower limb (inguinal lymph nodes).
Functions:
1- Filtration of lymph from bacteria and foreign bodies.
2- Formation and production of lymphocytes.
3- They are the sites of interaction between micro-organisms (antigens) and
phagocytes and lymphocytes (antibodies). So they play an important role in the
defense mechanism.