thymic and splenic disorders - Zaloga Flashcards
1
Q
thymus
A
- lymphepithelial organ
- cell mediated immunity
- cortex –> developing T cells, Macs
- medulla –> immunocompetent T cells, hassals, Macs, DCs
- hassals corpuscles –> form whirl bodies; desmosomes for thymus-blood barrier**
- myoid cells (in medulla) move lymphocytes through maturation –> associated with myasthenia gravis
2
Q
myasthenia gravis (graves disease)
A
-autoantibodies against ACh receptor
3
Q
DiGeorge syndrome
A
- thymic developmental disorder
- thymic hypoplasia –> defects in cell mediated immunity**
- 22q11 deletion syndrome
- ventricular septal defects
- cleft palate
- hypoparathyroidism –> low Ca2+ (tetany) and high phosphate
4
Q
thymic hyperplasia
A
- true hyperplasia
- increase size, weight
- increase lymphocyte #
- normal cortex, medulla - thymic follicular hyperplasia
- expansion of B cells in follicles (usually only small # of B cells)
- present with myasthenia gravis
5
Q
thymomas
A
- tumor of thymic epithelial cells –> impinge on mediastinal structures
- thymocytes are CD4+ and CD8+ T cells
- cortical thymomas with autoimmune disease
6
Q
types of thymomas
A
- noninvasive: usually medullary type, sparse thymocyte infiltrates
- mixed: 50% of thymomas, benign appearing medulla, polygonal cortical type, more likely invasive**, denser thymocyte infiltrates
- invasive: 25% of thymomas, benign appearing cortex, most invasive and aggressive
7
Q
thymic carcinoma
A
- 5% of thymomas
- show dysplasia and invasiveness
- sometimes metastasize to lung
- most squamous cell carcinoma
- some contain EBV genomes
8
Q
spleen
A
- mononuclear phagocyte system
- usually 10-11 cm
- site for immune response to blood-borne antigens and filter
- red pulp –> blood
- white pulp –> lymphocytes
- T cells in PALS, B cells in germinal centers
- sinusoids (filter and antigen detector) carry blood through splenic cords (cords of billroth) –> APCs and Macs phagocytize blood**
9
Q
spleen functions
A
- phagocytose senescent RBCs (trapped in cords)
- antibody production: DCs present antigen to T cells –> make plasma cells
- extra medullary hematopoiesis (in anemia or marrow dysfunction)
- sequestration of blood cells if enlarged –> cytopenias
10
Q
splenomegaly
A
- responds to systemic inflammation by increasing activity
- hypersplenism syndrome –> cytopenias
11
Q
splenic insufficiency/asplenia
A
- caused splenectomy or autoinfarction
- increased risk of sepsis and encapsulated organisms***
- sickle cell patients need vaccination**
12
Q
nonspecific acute splenitis
A
- due to blood-borne infection
- infiltration of neutrophils etc. into germinal centers causing inflammation –> necrosis or infarction of white pulp
13
Q
congestive splenomegaly
A
- Caused by chronic venous outflow obstruction with portal or splenic vein hypertension
- sequestering of cells (sinusoids filled with blood cells)
-obstruction causes: liver cirrhosis (most common), portal vein thrombosis, systemic venous congestion in right side of heart
14
Q
splenic rupture
A
- cause: trauma
- spontaneous ruptures due to infectious mono, typhoid fever, malaria, lymphoid neoplasm
- emergency due to internal bleeding –> splenectomy
- avoid contact sports with mono**
15
Q
splenic infarcts
A
- lesions due to occlusion of splenic artery and its branches
- usually due to noninfectious emboli from the heart** (common in enlarged spleens)
- forms depression, more pale (if older) or hemorrhagic (if recent)
