 Welcome back to our meds smarter lecture series where we're taking a smarter approach to preparing future physician Before we get started if you'll take just a quick minute and click that like button and also Subscribe and turn the bell on so that you'll be notified when we post new videos Let's continue on with our discussions of immunology and discuss the thymus The thymus is another portion of the lymphoid structures that is located in the antero Superior medial stynum so as you can see in this picture your medial stynum is what I'm circling right now in The antero superior so it's going to be as close to the front of the chest wall as possible And towards the top of the medial stynum so right where that arrow for the thymus gland is pointing to is where we will Usually see that it is immediately Postier to the sternum and it is usually around the the heart area and the aortic arch It is where t-cells will differentiate and mature in the body You'll see here in just a minute that I will show you a picture of the thymus kind of a drawing here And you're gonna see that it is encapsulated That is another point of the thymus that's important to know specifically here on its embryology the thymus Epithelium is derived from that third pharyngeal pouch, which makes it endoderm Now compare and contrast this to the thymic lymphocytes the thymic lymphocytes here are mesoderm of origin Now take a look at this picture over here You can see kind of the Origination there of the thymus between the lungs and the medial stynum and as you can see here We do have a capsule that is going to be out on the outer edge of the thymus Directly below that capsule is our cortex the cortex is where we have dense packing of immature t-cells So the t-cells that are not matured enough to be able to be released to the body are going to be found in the cortex Below that is our medulla. That is where we have our mature t-cells. It's a pale color Not as dense and packed as the cortex is we also see Hussal corpuscles that contain epithelial reticular cells within that particular structure Normal neonatal thymus has a sail shape on chest x-ray. I don't have a picture of that you can kind of see that a little bit here in this drawing and you will often see the Thymus involute by the age of three years of age Something to help you remember t-cells and b-cells our t-cells are from the thymus So remember the thymus makes t-cells and the bone marrow makes the b-cells Continue on discussing a thymus the thymus will often be absent. You won't have that thymic shadow Or you may have a hypoplastic thymus in some immunodeficiencies the ones that come to mind right off the top of your head should be SCID and a George syndrome for a absent thymus or absent thymic shadow a Pathology that can be associated with the thymus is a thymoma and that is a neoplasm of the thymus As you can see here in this CT scan you're seeing that thymus that is Extremely enlarged. It's starting to take up space around it Typically, we're usually seeing this in the middle section and it is actually growing Towards the posterior portion of the body here Thymomas are associated with several different disease processes specifically myostinia gravis superior vena cava syndrome pure red cell aphasia and then good syndrome If you found this material helpful for your studying Please like and consider subscribing to the channel also share this video so that more people can benefit from it like you have