00:00 The next lymphoid organ that we're going to discuss is the thymus. 00:04 The thymus is a bilobed lymphoid organ that is found in the inferior neck and extends into the mediastinum and partially overlies the heart. 00:16 This organ is going to function to mature our T cells. 00:21 So recall that T cells are formed in the bone marrow, but they mature in the thymus. 00:29 The thymus is most active and largest during childhood. 00:33 But as you grow, it starts to atrophy or gets smaller and eventually stops growing. 00:40 This growth stops during adolescence. 00:44 Even though it has atrophy and it's much smaller in an adult it is still able to produce immunocompetent cells. 00:52 It just produces them much more slowly than it did when you were a child. 00:59 The thymus is broken into lobules they contain both an outer cortex and an inner medulla. 01:07 The outer cortex contains rapidly dividing lymphocytes, which are the bulk of our thymic cells and also a few scattered macrophages. 01:18 The medulla region of the thymus is going to contain fewer lymphocytes and thymic corpuscles. 01:25 The thymic corpuscles are where the regulatory T cells are going to develop. 01:31 And this is the type of T cell that helps to prevent autoimmunity. 01:35 So while we talked about T cells that are attacking antigen, it's also important that we notice that there are also T cells that are regulatory, that are going to make sure that our T cells are attacking our own body cells. 01:50 This is where they are going to be located. 01:54 The thymus differs from other lymphoid organs in some important ways. 01:59 First of all, there are no lymphoid follicles in the thymus. 02:03 And because there are no lymphoid follicles, there are no B cells. 02:09 It also does not directly fight antigens. 02:13 So basically the thymus is only function is T-lymphocyte maturation. 02:20 Also in the thymus, we have something known as the blood-thymus barrier. 02:26 What this does is it keeps the immature lymphocytes that are being matured there, isolated away from antigens, because again, we're not fighting antigens here, we're just maturing these T lymphocytes. 02:39 So, we don't want any premature activation of T lymphocytes in this area. 02:47 The thymus also contains a stroma, which is made up of epithelial cells instead of the reticular fibers that we've seen in the other lymphoid organs. 02:58 These epithelial cells are going to provide an environment in which the T lymphocytes become immunocompetent.
The lecture Thymus – Primary Lymphoid Organs (Nursing) by Jasmine Clark is from the course Lymphatic System – Physiology (Nursing).
Which organ of the lymphatic system does not directly fight antigens?
Which functions are associated specifically with the cortex of the thymus? Select all that apply
5 Stars |
|
5 |
4 Stars |
|
0 |
3 Stars |
|
0 |
2 Stars |
|
0 |
1 Star |
|
0 |