Heme 06: Lab - Spleen And Lymph Nodes

Front 1

What is the function of lymph nodes?

Back 1

- Filters foreign antigens from LYMPH
- Mounts an immune response to protect the organism

Front 2

What is the function of the spleen?

Back 2

- Filters foreign antigens from BLOOD
- Mounts an immune response to protect the organism
- Removes particulate matter, senescent RBCs, and platelets from circulation

Front 3

What is labeled by A?

Back 3

Capsule of spleen

Front 4

What is labeled by B?

Back 4

Trabeculae of spleen

Front 5

What is labeled by C?

Back 5

Red Pulp of spleen (red staining area)

Front 6

What is labeled by D?

Back 6

White Pulp of spleen (blue/purple staining area)

Front 7

What is the organization of the cells in the spleen?

Back 7

- Cords of cells separated by sinusoids (stained red = Red Pulp)
- Cords of densely packed lymphocytes in between sinusoids (stained blue = White Pulp)

Front 8

Where do the RBCs flow through the spleen? How does this change during an RBCs life?

Back 8

- RBCs percolate through sinusoids and other spaces within the spleen
- RBCs must squeeze through narrow spaces
- Older RBCs have less flexible plasma membranes and may lyse during this passage
- RBC fragments are then phagocytosed by macrophages positioned along these passageways

Front 9

What is the approximate age of the RBCs that are removed from circulation by the macrophages in spleen?

Back 9

120 days

Front 10

What is prominent in the PB smear of a post-splenectomy patient? Why?

Back 10

- Acanthocytes - RBCs w/ irregular membrane / cytoplasmic projections and hyperchromasia d/t excessive membrane lipid
- Scattered Howell Jolly bodies

*These RBCs should be removed and destroyed in BM, but when spleen is absent or hypofunctioning, these cells persist*

Front 11

What is the name of RBCs w/ irregular membrane / cytoplasmic projections and hyperchromasia d/t excessive membrane lipid?

Back 11

Acanthocytes

Front 12

How does the structure of the spleen facilitate its function of filtering the blood and mounting an immune response if foreign antigens are present?

Back 12

- Splenic artery branches repeatedly upon entering hilum of spleen
- When small branches enter substance of spleen they are surrounded by accumulation of T cells called Periarterial Lymphatic Sheath (PALS)
- PALS contain lymphoid follicles composed of B cells
- Vessels surrounded by PALS are called central arterioles

Front 13

What happens to splenic arteries?

Back 13

- Branches repeatedly upon entering hilum of spleen
- When the branches enter substance of spleen they are surrounded by accumulation of T cells called Periarterial Lymphatic Sheath (PALS)

Front 14

Where are T cells found in the spleen?

Back 14

Periarterial Lymphatic Sheath (PALS)

Front 15

Where are B cells found in the spleen?

Back 15

Periarterial Lymphatic Sheath (PALS) contains lymphoid follicles composed of B cells

Front 16

What are the components of the white pulp of the spleen?

Back 16

- Central Arterioles
- Surrounding Periarterial Lymphatic Sheath (PALS)

Front 17

What happens to foreign antigens as blood flows through the spleen?

Back 17

- May become trapped by antigen-present cells
- Present to appropriate lymphoid cells which can mount an immune response

Front 18

What is abundant in the splenic capsule, trabeculae, and blood vessel tunics?

Back 18

Reticular fibers

Front 19

What solid organs have a stroma composed of reticular fibers?

Back 19

- Lymph nodes
- Spleen
- Liver

Front 20

Splenectomy can be performed with minimal long-term effects to the patient. Why would this be necessary?

Back 20

- Controls bleeding after traumatic splenic rupture / injury
- Some patients w/ pathologically enlarged spleens have abdominal discomfort and early satiety and may need splenectomy
- May be removed for tumors too

Front 21

Splenectomy can be performed with minimal long-term effects to the patient. What are the clinical consequences?

Back 21

Increased susceptibility to:
- Bacterial infections, specifically encapsulated bacteria like Strep pneumo
- Parasitic disease Babesia (via ticks)

Front 22

Splenectomy can be performed with minimal long-term effects to the patient. What are the PB smear changes?

Back 22

RBC inclusions:
- Pappenheimer bodies
- Howell Jolly bodies

(no clinical consequences)

Front 23

What splenic function increases in response to early sickle cell anemia?

Back 23

Removal of RBCs

Front 24

What splenic function increases in response to infectious mononucleosis?

Back 24

Immune Response

Front 25

What splenic function increases in response to AIDS?

Back 25

Immune Response

Front 26

What splenic function increases in response to bacterial endocarditis?

Back 26

Immune Response

Front 27

What splenic function increases in response to BM tumor replacing normal hematopoiesis?

Back 27

Hematopoiesis

Front 28

What splenic function increases in response to hereditary spherocytosis?

Back 28

Removal of RBCs

Front 29

What is the function of lymphocytes?

Back 29

Detect and eliminate foreign antigens

Front 30

What are the primary lymphatic organs?

Back 30

Bone marrow and thymus - maturation of B and T cells occurs here

Front 31

Where do lymphocytes mount an immune response?

Back 31

Secondary lymphatic organs

Front 32

What happens in secondary lymphatic organs?

Back 32

- B cells differentiate into plasma cells
- T cells further mature into effector or memory T cells

Front 33

What is the stroma of the lymph nodes made of?

Back 33

Reticular fibers

Front 34

What is the stroma of the spleen made of?

Back 34

Reticular fibers and smooth muscle

Front 35

What is being filtered in the lymph node?

Back 35

- B cells
- T cells
- Macrophages

Front 36

What is the location of B cells and T cells/macrophages in the lymph nodes?

Back 36

- B cells in follicles of cortex
- T cells and macrophages in paracortex and medulla

Front 37

What is the organization of the lymphatic system? Functions?

Back 37

- Small, blind-ended capillary-like structures drain the extracellular fluid from the tissue spaces
- Lymphatic capillaries merge, forming a circulatory system that ultimately returns lymph to the venous system

Front 38

What is located along the lymphatic system? Function?

Back 38

Lymph nodes - filteres the lymph, if foreign antigens happen to penetrate the body's defenses and access these tissues, these antigens may be carried away from tissues by lymphatic system

Front 39

In what tissues are there lymphatic channels?

Back 39

All tissues, except:
- CNS
- Orbit
- Inner ear
- Epidermis
- Cartilage and bone

Front 40

What is the order of circulation through a lymph node?

Back 40

1) Lymph enters node via afferent lymphatic vessels that penetrate the CT capsule surrounding the node along the convex surface
2) Lymph is released from afferent vessels into the subscapular sinus and flows through lymphatic channels toward the hilus
3) Lymph is carried away from the node by efferent lymphatic vessels that leave the convex hilus

Front 41

What slows the flow of lymph through the lymph node? Why is this important?

Back 41

- Network of fibroblasts and reticular fibers that make up the stroma of the lymph node
- Allows lymph to come in contact w/ lymphocytes and macrophages which are attached to stromal fibers

Front 42

What are the structures labeled A and B?

Back 42

A = Cortex
B = Subscapular Sinus

Front 43

What are the structures labeled A and B?

Back 43

- A = Secondary Lymphoid Follicle
- B = Primary Lymphoid Follicle

Front 44

What kind of follicle is uniform in staining intensity? What does it consist of?

Back 44

Primary Lymphoid Follicles
- Contains mostly naive B cells

Front 45

What kind of follicle has a lightly staining center surrounded by a darker staining periphery? What are these regions called?

Back 45

Secondary Lymphoid Follicles
- Germinal center = lightly staining center
- Mantle zone = darker staining periphery

Front 46

What makes a follicle transition from a primary follicle to a secondary follicle?

Back 46

Indicates that B cells have been activated by the presence of a foreign antigen in the lymph node

Front 47

What is happening within a secondary follicle of a lymph node?

Back 47

- B cells with a high affinity for foreign antigen are undergoing clonal expansion and mutation to increase their affinity for the antigen
- Rapidly expanding activated B cells compress the surrounding non-reactive B cells to form the peripheral mantle zone

Front 48

What is in the mantle zone in a secondary lymph node?

Back 48

Non-reactive B cells that are pushed away from germinal center by rapidly expanding activated B cells

Front 49

What happens to activated B cells after proliferating?

Back 49

Migrate from secondary follicles to medulla of the node, forming strands of cellular tissue (medullary cords) separated by lymph-filled sinuses

Front 50

What happens to activated B cells once they get to the medulla?

Back 50

Release their antibodies into lymph which is carried by efferent lymphatic vessels to general circulation

Front 51

What area is in between the cortex and medulla in the lymph node? What is in this location?

Back 51

Paracortex
- Dominated by T cells
- Macrophages and APCs (eg, Langerhans cells and dendritic cells
- High endothelial venules

Front 52

What is found in the endothelium that lines the high endothelial venules found in the paracortex?

Back 52

Endothelium expresses lymphocyte-homing receptors which facilitate the transfer of lymphocytes from the blood into the nodes

Front 53

What is the functional significance of a germinal center in a lymph follicle?

Back 53

Germinal center indicates that new B cells are being produced in response to an antigenic stimulus

Front 54

What is the functional significance of high endothelial venules in the lymph node?

Back 54

High endothelial venules are the "conduit" by which lymphocytes ENTER and are sequestered within lymph nodes

Front 55

When you palpate a patient's cervical region, noting the presence of swollen glands, what is it that you re really palpating and what is happening in these structures at the cellular level?

Back 55

- You are palpating lymph nodes that are enlarged and have triggered a pain response
- Nodes are enlarged d/t reactive changes, including B cell proliferation forming germinal centers (follicular hyperplasia), T cell proliferation in paracortex (paracortical hyperplasia), and/or expanded sinuses w/ histiocytes (sinus histiocytosis)

Front 56

What causes Follicular Hyperplasia?

Back 56

B cell proliferation forming germinal centers

Front 57

What causes Paracortical Hyperplasia?

Back 57

T cell proliferation in paracortex

Front 58

What causes Sinus Histiocytosis?

Back 58

Expanded sinuses w/ histiocytes

Front 59

What do these circled images represent?

Back 59

Mitotic figures

Front 60

What does the black represent?

Back 60

- Animal was injected w/ carbon prior to preparing the tissues for histological examination
- Macrophages located in paracortex and medulla of lymph nodes sequestered the carbon particles which are readily visible