10.11 Thymus Flashcards
Shortly after forming in the bone marrow, T cells migrate to _
Shortly after forming in the bone marrow, T cells migrate to thymus
The majority of T cells undergo _ in the thymus
The majority of T cells undergo apoptosis in the thymus
* The thymus is a site of rigorous testing and most T cells don’t meet the standards
* The T cells that pass then leave the thymus and participate in the body’s immune response
The thymus is a bilobed, encapsulated organ that is located in the _
The thymus is a bilobed, encapsulated organ that is located in the anterior part of the superior mediastinum
The thymus is (in front/ behind) the sternum and (in front/ behind) the heart
The thymus is behind the sternum and in front of the heart
The thymus changes colors from grayish-pink to yellow during maturation due to _
The thymus changes colors from grayish-pink to yellow during maturation due to infiltration of fat
Describe the structure/ appearance of the thymus
Thymus:
* bilobular
* pyramidal shape
* surrounded by capsule
Label the parts of the thymus
Cortex: thin, fibrous outer layer
Medulla: central region
Thymic corpuscles: keratinized epithelial reticular cells
Blood comes into the thymus via the _ which is a branch from the internal thoracic artery
Blood comes into the thymus via the thymic artery which is a branch from the internal thoracic artery
* The thymic arteries flow along the interlobular septa and branch off into arterioles and capillaries
The thymus is composed mostly of (T cells/ B cells)
The thymus is composed mostly of T cells
The (medulla/ cortex) of the thymus appears darker because the T cells are closely packed together
The cortex of the thymus appears darker because the T cells are closely packed together
* Dark-blue basophilic appearance
The medulla of the thymus is pale in appearance because it has fewer lymphocytes and more _ cells
The medulla of the thymus is pale in appearance because it has fewer lymphocytes and more epithelial cells
Thymic corpuscles are also called _
Thymic corpuscles are also called Hassall corpuscles
The _ is responsible for keeping antigens circulating in the bloodstream out of the thymus
The blood-thymus barrier is responsible for keeping antigens circulating in the bloodstream out of the thymus
* Keeps the antigens from disrupting normal T cell selection process in the thymus
The blood-thymus barrier consists of two different parts _ (cells) and _ (capillaries)
The blood-thymus barrier consists of two different parts epithelial-reticular cells and thymic cortical capillaries
The epithelial-reticular cells in the thymus are connected by _ which provide a net-like scaffolding for the thymus and prevent antigens from getting in
The epithelial-reticular cells in the thymus are connected by tight junctions which provide a net-like scaffolding for the thymus and prevent antigens from getting in
The thymic cortical capillaries are (fenestrated/ nonfenestrated)
The thymic cortical capillaries are nonfenestrated so that the capillaries in the blood-thymus barrier are not permeable to antigens
Naiive and immature T cells are produced in the _ –>
They then undergo positive and negative selection in the _ –> This makes them mature –>
They can then leave the thymus and bind antigen to become _ T cells or _ T cells
Naiive and immature T cells are produced in the bone marrow –>
They then undergo positive and negative selection in the thymus –> This makes them mature –>
They can then leave the thymus and bind antigen to become effector T cells or memory T cells
The thymus produces hormones that facilitates T cell maturation called _
The thymus produces hormones that facilitates T cell maturation called thymosins
_ and _ are thymosins that facilitate in T cell maturation in the thymus and play a role in promoting cell migration, angiogenesis, cell survival, stem cell differentiation, and modulation of cytokine production
Thymopoietin and serum thymic factor are thymosins that facilitate in T cell maturation in the thymus and play a role in promoting cell migration, angiogenesis, cell survival, stem cell differentiation, and modulation of cytokine production
Fast growing malignancies of the thymus are called _ ; slow growing malignancies of the thymus are called _
Fast growing malignancies of the thymus are called thymomas ; slow growing malignancies of the thymus are called thymic carcinoma
* Half of patients with thymomas have myasthenia gravis
_ is a consequence of normal loss of thymic cells that occurs throughout adulthood
Age-related thymic hypoplasia is a consequence of normal loss of thymic cells that occurs throughout adulthood
* We loss about 3% of our thymic cells each year
* Partially explains why older adults have reduced immune function
_ is a rare congenital disorder that causes decreased immune response in children; involves failure of thymic development, hypoplasia of the parathyroid glands, and congenital heart disease
DiGeorge syndrome is a rare congenital disorder that causes decreased immune response in children; involves failure of thymic development, hypoplasia of the parathyroid glands, and congenital heart disease
* Some children develop low T cell counts
* Severe recurrent lung and sinus infections
* Sometimes need stem cell transplantation/ thymic transplantation
