SPLEEN AND THYMUS Flashcards
Where is the spleen located?
The spleen is located in the left upper quadrant (LUQ) of the abdomen, anterolateral to the left kidney, and protected by the 9th-11th ribs.
What are the consequences of splenic dysfunction?
Splenic dysfunction (e.g., postsplenectomy, sickle cell disease autosplenectomy) leads to decreased IgM, decreased complement activation, decreased C3b opsonization, and increased susceptibility to encapsulated organisms.
What are common findings after splenectomy?
Common postsplenectomy findings include Howell-Jolly bodies (nuclear remnants), target cells, thrombocytosis (loss of sequestration and removal), and lymphocytosis (loss of sequestration).
Why should patients with splenic dysfunction be vaccinated?
Patients should be vaccinated against encapsulated organisms (pneumococci, Hib, meningococci) to prevent infections.
What does the periarteriolar lymphatic sheath contain?
It contains T cells and is located within the white pulp.
What does the follicle of the spleen contain?
It contains B cells and is located within the white pulp.
What is the function of the marginal zone in the spleen?
The marginal zone contains macrophages and specialized B cells. It is the site where antigen-presenting cells (APCs) capture blood-borne antigens for recognition by lymphocytes. It is located between the red pulp and white pulp.
Where is the thymus located?
The thymus is located in the anterosuperior mediastinum.
What is the function of the thymus?
The thymus is the site of T-cell differentiation and maturation.
What is the embryonic origin of the thymus?
The thymic epithelium is derived from the third pharyngeal pouch (endoderm), while thymic lymphocytes are of mesodermal origin.
What is the structure of the thymus?
The cortex is dense with immature T cells, while the medulla is pale with mature T cells and Hassall corpuscles containing epithelial reticular cells.
What does a normal neonatal thymus look like on CXR?
A normal neonatal thymus appears ‘sail-shaped’ on chest X-ray and involutes by age 3 years.
What are T cells associated with?
T cells are associated with the thymus.
What are B cells associated with?
B cells are associated with the bone marrow.
In which immunodeficiencies is an absent or hypoplastic thymic shadow seen?
An absent or hypoplastic thymic shadow is seen in some immunodeficiencies, such as SCID and DiGeorge syndrome.
What is a thymoma?
A thymoma is a neoplasm of the thymus.
What conditions are associated with thymoma?
Thymoma is associated with myasthenia gravis, superior vena cava syndrome, pure red cell aplasia, and Good syndrome.
