Lymphoid Structures III Flashcards
Where are macrophages found in the spleen?
Nearby to the sinusoids (p.193)
What are the 5 layers of a splenic sinusoid from outside to inside?
Red pulp; Marginal zone; Germinal Centres; PALS; Central arteriole (p.193)
In what layer of the splenic sinusoid does venous drainage occur?
In the red pulp (p.193)
What is housed in the red pulp of the spleen?
RBCs (p.193)
What is housed in PALS of the spleen?
T cells (p.193)
What is housed in the marginal zone of the spleen?
APCs (p.193)
What are housed in germinal centres of the spleen?
B cells (p.193)
In what general area of the spleen are both T cells and B cells found?
In the white pulp (p.193)
Where are T cells found in the spleen?
In the periarterial lymphatic sheath (PALS) (p.193)
Where are B cells found in the spleen?
In follicles (p.193)
What is the function of splenic macrophages?
To remove encapsulated bacteria (p.193)
Describe the mechanism by which splenic dysfunction leads to increased susceptibility to encapsulated organisms.
Splenic dysfunction –> Decreased IgM –> Decreased compliment activation –> Decreased C3b opsonization –> Increased susceptability to encapsulated organisms (p.193)
Name the six encapsulated organisms.
Streptococcus pneumoniae, Haemophilus influenzae type B, Neisseria meningitidis, Salmonella, Klebsiella pneumoniae, Group B Streptococci (pneumonic: SHiN SKiS) (p.193)
Name three pathological findings associated with splenectomy.
Howell-Jolly bodies (nuclear remnants), target cells, thrombocytosis (p.193)
What is the primary function of the thymus?
Site of T cell differentiation and maturation (p.193)
Describe the structure of the thymus.
Encapsulated organ with a dense cortex filled with immature T cells. Contains a medulla and epithelial retirular cells (p.193)
What is the embryological origin of the thymus?
From the epithelium of the 3rd branchial pouch (p.193)
What is the origin of thymus lymphocytes?
Mesenchymal origin (p.193)
What is contained in the cortex of the thymus?
Densely packed with immature T cells (p.193)
What is contained in the medulla of the thymus?
Medulla is pale with mature T cells and epithelial reticular cells containing Hassall’s corpuscles (p.193)
Where do positive and negative selection of T cells occur in the thymus?
Positive selection (MHC restriction) occurs in the cortex; negative selection (nonreactive to self) occurs in the medulla (p.193)
