Lymphoid Organs 2

Question 1

Spleen structure

Answer 1

Does not have afferent lymphatics
Has a thick CT capsule
White pulp - rich in lymphocytes (lymphoid nodules)…blue if stained…reacts immunologically to BBAs
Red pulp - rich in RBCs…removes old, dead, dying RBCs

NOT divided into a cortex and medulla but IS supported by reticular fibers

Question 2

Arterial flow of spleen

Answer 2

Trabecular artery and vein branch into central artery that travels through the MIDDLE of PALS…Central artery branches into follicular arteries that enter follicles (off center)…eventually branch into penicillar arteries that branch into arterioles and empty into dilated splenic sinusoids….there the macrophages will eat old RBCs

Question 3

Sheathed arteries vs follicular arteries

Answer 3

Sheathed tend to be centrally located in a dark T cell sheath
Follicular are eccentrically placed within splenic nodule of B cells

Question 4

Splenic sinusoids and structure

Answer 4

Very leaky so that RBCs can escape

Made of rod shaped endothelial cells with a basement membrane in anastomosing bands so that it can leak

Question 5

How does spleen differ from lymph nodes?

Answer 5

No sub scapular sinus

Spleen has random distribution of follicles

Question 6

Immune functions of spleen

Answer 6

Prolix of lymphocytes
Production of ABs
Removal of macromolecular antigens from blood

Question 7

Hemopoietic functions of spleen

Answer 7

Form blood cells during fetal life
Remove old
Retrieve iron

Question 8

Loss of the spleen

Answer 8

Lymph nodes recover immune function

Bone marrow and liver help destruction of old RBCs

Question 9

Thymus structure

Answer 9

Divided into lobules (separated by CT)
Each lobule has a cortex and medulla
Does not contain nodules
Secrete thyme hormones like htymosin

Question 10

Components of thymus

Answer 10

Epithelial reticular cells that form the framework (different than CT framework of lymph nodes and spleen)…have sub capsular ERCs but not sinus
Lymphatic component of T cells differentiating
Connective tissue component - capsule of organ plus the septa that dived into lobes and lobules

Also some macrophages present to destroy improperly formed T cells

Question 11

Cortex vs medulla of thymus

Answer 11

Cortex - packed with T cells

Medulla - fewer T cells

Question 12

ERCs

Answer 12

Form the framework for thyme lymphocytes and do NOT secrete reticular fibers
Secrete thymosin

Connected by desmosomes

Question 13

Blood thymic barrier

Answer 13

Consists of capillary endothelium, endothelial basal lamina, CT with a ring of macrophages, basal lamina of ERC, and the ERC sheath

Separated from lymphatic system because no afferent lymphatics

Question 14

Blood supply of thymus

Answer 14

Capillary loop supplies to cortex

Mature T cells leave cortex through aorticomedullar post capillary venules

Question 15

Thymus corpuscles

Answer 15

Concentric closely packed old ERCs…become larger and more numerous with age

ONLY in the medulla

Question 16

Light spots in cortex of the thymus and medulla

Answer 16

Cortex - ERCs

Medulla - corpuscles

Question 17

Thymus function

Answer 17

Site for programming, differentatioation, and proliferation of new T cells…most of lymphocytes formed die within a few days