Video Transcript
All the following flow in the lymphatic system and have an immunity function
except. (A) Leukocytes, (B) antibodies, (C) fatty acids, or (D) none of the answers are
correct.
This question asks us about the immune function of the lymphatic system. So let’s review the key facts about this system to help us answer the question
correctly.
The lymphatic system is very important for circulation, absorption of certain
nutrients, and immunity. To carry out its roles, it is made up of a series of specialized organs, tissues,
vessels, and nodes. The lymphatic system helps the circulatory system because it retrieves excess fluid
that has been deposited by the blood capillaries in the space around the body cells,
called the interstitial space. The capillaries have a wall which is only one cell thick. So, fluid can leak out and deliver important nutrients and oxygen to the body
cells. This is called interstitial fluid, and about 90 percent of it is reabsorbed by the
capillaries. The other 10 percent is taken up by the lymphatic capillaries, and it is now called
lymph.
The lymph moves up from the lymphatic capillaries to the lymphatic vessels, and then
it is transported around the body to various lymph nodes. These are small bean-shaped organs which filter the blood for damaged and cancerous
cells. They also contain the important immune cells — white blood cells, or leukocytes. Leuko- means white and -cytes means cells. These include B lymphocytes, which produce antibodies to bind to antigens to try to
prevent harm to the body. Pathogens in the body will be trapped and taken to lymph nodes, which will activate
the lymphocytes and cause them to enter the circulatory system to attack
pathogens.
There are about 600 lymph nodes in the body. You may notice the ones in your neck or armpit when you are sick as they often become
sore. This is because there is a lot of activity during an infection and the glands
swell. After the lymph has traveled throughout the body, the lymphatic vessels return their
contents into the circulatory system at the subclavian vein, just below the
collarbone.
The lymphatic system is also involved in the absorption of fats and fat-soluble
vitamins. In the villi of the small intestine, there are blood capillaries and special lymph
capillaries called lacteals. Most digested nutrients are absorbed by the blood, but the fats and fat-soluble
vitamins are taken up by the lacteals.
Once the fatty acids have been absorbed by the epithelial cells of the villi, they
are converted back into triglycerides. They then combine with other molecules, such as phospholipids and cholesterol, to
form particles called chylomicrons. Any fat-soluble vitamins absorbed also form part of these. The chylomicrons are then transported through the lymphatic system and delivered into
the circulatory system to be used by the body.
Having reviewed the key facts about the lymphatic system, let’s have a look at our
question again. We did see that leukocytes are found in lymph nodes, and B lymphocytes, a type of
leukocyte, produce antibodies to fight infection. So they have a function in immunity. Fats do pass into the lymph at the small intestine, but they do not have a role in
immunity, and they are not carried as free fatty acids.
Therefore, the correct answer to our question is (C). The option that does not have an immunity function in the lymphatic system is fatty
acids.
