Capsulated Lymphoid tissue

Question 1

1. Thymus produces what kinds of cells?

2. The thymus____ in size with age and is replaced by what?

Answer 1

1. T cells

2. decreases, replaced by fat and connective tissue but still continues to produce T cells in adults

Question 2

What are the two main types of Capsulated lymphoid tissue? What organs fall under each type?

Answer 2

Capsulated lymphoid tissue can either have lobules or no lobules
The Thymus has lobules, but the spleen and lymph nodes do not

Question 3

Thymus produces what types of cells?

What happens to size of thymus as we age?

Answer 3

T cells

Decreases in size and is replaced by fat and connective tissue but still continues to produce T lymphocytes in adults

Question 4

Thymus has how many lobes?
What kind of capsule?
Septa or trabeculae?

Answer 4

2 lobes
Connective tissue capsule
Septa made of connective tissue that penetrates to medulla and divides thymus into incomplete lobules

Question 5

Thymus lobules are darker where and lighter where?
Defining feature of thymus?
Lymph nodules?
Germinal centers?

Answer 5

Darker outer cortex, lighter inner medulla
Defining feature=Hassal’s corpuscle
NO lymph nodules!
NO germinal centers!!

Question 6

Where does T lymphocyte maturation specifically occur in thymus?
What are the order of the types of cells starting from outer cortex to inner medulla?

Answer 6

Maturation occurs in cortex
Order from outer to inner:
Subcapsular thymic epithelial cells (right by capsule)
Thymic cortical epithelial cells (cortex)
Maturing T cells (developing thymocytes)–inner cortex
** T cells in the cortex are not completely mature!! THey are in the process of maturation!

Question 7

Are macrophages in the cortex of the thymus or the medulla?

Answer 7

BOTH!

Question 8

Where are MATURE T lymphocytes found within thymus? What other cells are found here?

Answer 8

In the medulla

Hassal’s corpuscles, thymic medullary epithelial cells and dendritic cells are also found in medulla

Question 9

What is a Hassal’s corpuscle and what is its function?

Answer 9

Closely packed epithelial cells in thymic medulla only. It releases a factor that stimulates Thymic dendritic cells to complete maturation of T cells

Question 10

Where in the thymus is the thymus blood barrier? What is the purpose of this barrier? What kind of cells make up this barrier?

Answer 10

ONLY in cortex
Prevents most circulating antigens from reaching developing T cells
Epithelial reticular cells bound to capillaries

Question 11

Where is spleen located? What is a major function of the spleen? What other kinds of cells reside in spleen?

Answer 11

Left superior quadrant
Hematopoeisis takes place here and macrophages in spleen destroy old red blood cells; spleen also traps antigens
1/3 of platelets here

Question 12

1. Describe the capsule of the spleen

2. Does spleen have septa or trabeculae?

Answer 12

1. Connective tissue capsule: collagen, elastic fibers, smooth muscle
2. Trabeculae extend from capsule and divide spleen into incomplete compartments

Question 13

Describe the cortex and Medulla of spleen

Answer 13

Trick question! Spleen doesn’t have cortex and medulla!

Question 14

Describe the parenchyma of the spleen and its components

Answer 14

Parenchyma is made of reticular fibers supporting the red and white pulp

White pulp=rich in lymphoid tissue
Red pulp: rich in red blood cells

Question 15

What are the key features of the white pulp of the spleen?

Answer 15

Germinal center
Corona (B cells and APCs)
Central artery
Periarteriolar lymphoid sheaths (PALS)–T cells
Marginal Zone (where red and white pulp interact)

Question 16

Describe the organization of the Red pulp

Answer 16

Splenic cord formed by reticular cells
Splenic Sinusoid
Penicillar Arteries
Macrophage sheathed capillaries
Circulating blood cells

Question 17

Describe the blood flow into the spleen

Answer 17

Splenic artery (from celiac trunk)–>Trabecular arteries into parynchema of spleen–>central arteries–>white pulp surrounded by periarteriolar lymphoid sheaths

*central arteries produce radial arteries while in white pulp which feed into marginal zone sinuses–>Enter red pulp as penicillar arteries which either end in splenic sinusoids (closed) or red pulp (open circulation)

Question 18

How do are the damaged red blood cells removed once the central artery becomes penicillar arteries?

Answer 18

Penicillar arteries are sheathed by macrophages that reoved the damaged RBS from blood

Question 19

Do lymph nodes have lobules?

What is a lymph node and what does it do?

Answer 19

NO lobules
Smallest, most numerous encapsulated lymphoid organs
Filters lymph–removes Ags and cellular debris, produce lymphocytes and add antibodies

Question 20

Describe the capsule of lymph nodes
Do lymph nodes have septa or trabeculae?
Does it have cortex and medulla? What else does it have?

Answer 20

Connective tissue capsule
Trabeculae that extend into parenchyma between cortical nodules
Outer cortex, inner medulla=yes
Also has hilum where enters via arteries, leaves via veins and lymph leaves via efferent lymph vessels

Question 21

Describe the outer and inner cortex of lymph nodes

Answer 21

Outer cortex: B cell rich, lymphatic nodule with germinal center, mantle and subcapsular/cortical sinus
Inner cortex: T cell rich, lymphatic nodules

Question 22

Describe the medulla of lymph nodes

Answer 22

Has medullary cords composed of macrophages and plasma cells

Also has medullary sinuses which are spaces lined by endothelial cells surrounded by reticular cells and macrophages

Question 23

What do the lymph node sinuses do?

Answer 23

Filter lymph and direct flow
Made of mesh of reticular cells and fibers, macrophages and follicular dendritic cells
It slows flow of lymph which facilitates Ag removal
Lymph is cleared of 90% of Ags and cellular debris

Question 24

Which organs have a cortex and medulla?
Which organs have lymphoid nodules? Which ones do NOT?
Which organs have cords and sinuses?

Answer 24

Cortex and medulla: Thymus, lymph node
Lymph nodules: Lymph nodes, spleen and tonsils (Thymus does NOT!)
Cords and sinuses: Lymph nodes and spleen

Question 25

Diagnostic feature of:
Thymus:
Lymph nodes:
Spleen:
Tonsils:

Answer 25

Thymus: Hassal’s Corpuscles
Lymph nodes: Cortical nodules, subcapsular sinus
Spleen: Central arteries
Tonsils: Epithelial covering