1. Chapter 8 Lymphoid organs

2. General organization of lymphoid organ:
largely consist of lymphoid tissue
Reticular tissue: stellate-shaped with processes to form network
Diffuse lymphoid tissue
Lymphoid nodules
Cells:
Lymphocyte (chiefly)
Plasma cell
antigen presenting cell
other cells

3. a. Diffuse lymphoid tissue:
no clear boundary
mainly consists of T-lymphocyte
postcapillary venules:
-high endothelial venules, lining of tall cuboidal cells
-opening for lymphocyte enter lymphoid tissue from blood
Lymphoid
nodule
Diffuse LT

4. b. Lymphoid nodule: spherical or ovoid have clear boundaries
mainly composed of B-lymphocyte
germinal center: lighter-stained central zone, these cells produce antibody-synthesizing plasma cells

5. Cells of lymphatic tissue

6. 1) Lymphocyte: a. T-lymphocytes:
cytotoxic T cell: Tc C- kill the tumor cell, virus infective cell and foreign cell
helper T cell: Th C- stimulate the B-lymphocyte differentiate into plasma cell
suppressor T cell: Ts C – regulate the function of B-lymphocyte and T-lymphocyte
b. B-lymphocytes: become into plasma cell
c. NK cell: attack virus infective cell and tumor cell without previous stimulation

7. 3) Antigen presenting cell: a. dendritic cell b.macrophage
2) Plasma cell
3) Antigen presenting cell:
a. dendritic cell
b.macrophage
Antigen processing is a necessary preliminary step for activation of T cell.

8. 4) other cells:
granulated cell
mast cell
blood platelet
blood-bone stem cell
Function:
i.      immunologic defense
ii.     immune surveillance
iii.    immune homeostasis

9. Lymphatic organs: central lymphatic organs: produce the lymphocyte antigen-independent proliferation contain: thymus---T-lymphocyte bone marrow---B-lymphocyte peripheral lymphatic organs: receive the lymphocyte and perform the immune response antigen-dependent proliferation contain: lymph node spleen tonsils

10. The immune system: Immune response:
consists of the lymphatic organs, lymphocytes of the blood and lymph, and collections of different types of lymphocytes dispersed throughout the connective tissue.
is essential to the body’s immunological defense against bacteria, viruses and other foreign bodies.
Immune response:
Cellular immunity: involving mainly T-lymphocytes
Humoral immunity: involving mainly B-lymphocytes
Mast cells, macrophages and other white blood cells are also involved in the immune response.

11. thymus
A flattened, bi-lobed structure lying in the superior mediastinum
In the new-born child it is at its greatest size relative to body size
Thymus continue to grow until puberty when it is replaced by fibrofatty tissue

12. Structure: Capsule ( C.T.) interlobular septa (trabecula)
Endothelial reticular cell (ERC)
Lymphocyte: thymocyte
Macrophage: secrete IL-1
Cortex:
ERC
Lymphocyte: few
Macrophage: secrete IL-1
Thymic corpuscles
Medulla:

13. Thymus

14. Cortex medulla

15. The cortex of thymus A very active site of lymphocyte production
More than 90% of the thymocyte degenerate in this area, only less than 10% of thymocyte will mature and leave the thymus as T-lymphocytes through the postcapillary venules.
Endothelial reticular cell (ERC)

17. The medulla of thymus Hassall’s ( thymic) corpuscles
a characteristic feature of the thymus
their significance is as yet unknown

18. Hassall’s ( thymic) corpuscles
spherical or ovoid body, um in diameter, composed of concentrically-arranged epithelial reticular cells, the central cells often show degeneration

19. Blood-thymus barrier:
provide a stable environment for lymphocytes developing in the cortex---prevents circular antigens from reaching the thymic cortex where T cells are being formed
Consists of :
endothelial cell of continuous capillary
very thick basement membrane
perivascular space with macrophage in it
basement membrane of ERC
ERC or their processes with desmosome

20. Thymus function:
the thymic epithelial reticular cells can secrete thymic hormones (thymosin, thymolin, thymopoietin)
induce the stem cell to differentiate into
T-lymphocyte

21. Adult thymus has high infiltration of adipose tissue (A)

22. Older adult thymus has large amounts of adipose tissue

23. Lymph node
A mass of lymphatic tissue enclosed in a capsule of connective tissue
Widely scattered along the course of lymph vessels
Concentrated in area in neck, axilla (arm pits), and groin.

24. ---capsule: CT, trabeculae or septa
Structure
---capsule: CT, trabeculae or septa
---cortex: outer densely-stained part
---medulla: inner paler-stained part
hilum

25. Structure: capsule trabecula cortex several afferent lymph vessels,
lymphoid nodule (B-LC)
internodule zone
out cortex: (superficial cortex)
inner cortex: diffuse lymphoid tissue (T-LC) (paracortical zone)
subcapsular sinus:
peritrabecular sinus
macrophage
cortical lymphatic sinuses

26. capsule
outer cortex
inner cortex

27. SS: subcapsular sinus
T: trabecular

28. Capsule
Subcapsular sinuses
Trabeculae

29. Afferent lymph vesselsGC

30. Postcapillary venules in inner cortex

31. Medulla ---medullary cord: LT cord:
B-lymphocyte, plasma cell, macrophage, mast cell
---medullary sinus:
similar to cortical sinus and connect with them
more macrophage

32. capsule
outer cortex
inner cortex

33. Passage of lymph in lymph node
Afferent lymph vessels
Subcapsular sinus
Cortical sinuses
Medullary sinuses
Efferent lymph vessels

34. Lymph enters afferent lymph vessels passes through subcapsular sinuses and down through trabecular sinuses around trabeculae.

35. Efferent lymph vessels in hilum

36. Recirculation of lymphocytes:
Lymphoid tissue
Efferent lymphatic vessel
Postcapillary venules
Blood circulation

37. Functions of lymph node
Filter the lymph
Place to perform the immune response
Involve in the recirculation of lymphocyte

38. Spleen located in the passages of blood capsule white pulp structure
red pulp
marginal zone
structure
parenchyma

39. Structure:
capsule:
D.C.T. containing smooth muscle----trabecular; capsule is covered by mesothelium
The splenic artery branch into trabecular arteries

40. White pulp: gray-white spots periarterial lymphatic sheath:
- diffuse lymphoid tissue : T-lymphocyte, macrophage
- central artery
splenic corpuscle:
-lymphoid nodules: B-lymphocyte, macrophage

41. Marginal zone: between White pulp and Red pulp
splenic corpuscle
Marginal zone:
between White pulp and Red pulp
T-, B-lymphocyte, macrophage, less erythrocyte
marginal sinus: central artery’s branch- channel for antigen and lymphocyte enter lymphoid tissue
function: first capture, recognize antigen and induce immune reaction

42. Red pulp: splenic cord: Lymph tissue cord
B-,T-lymphocyte, macrophage, erythrocytes
function: filter blood
splenic cord
splenic sinus

43. splenic sinus: Blood sinus; 12-14um endothelial cell: rod-liked, gap
Reticular fiber
basal lamina: incomplete
Abundant macrophage
splenic sinus
splenic cord
endothelial cell

45. splenic A→trabecular A→central A branches → marginal sinuses →
Blood supply of spleen
Study by yourself
splenic A→trabecular A→central A branches → marginal sinuses →
penicillar arterioles (including: pulp arteriole→ sheathed capillary→ arterial capillary) → splenic sinus→ pulp venule→ trabecular vein→ splenic vein

47. Function: a. filter the blood b. immunological defence
c. production of blood cells in fetus
d. blood storage: 40 ml

48. Tonsil (Study by yourself)
---palatine tonsil
---pharyngeal tonsil
---lingual tonsil

49. structure Mucosa stratified squamous epithelium Capsule: C.T.
form crypts
lymphocyte infiltration
lymphatic nodules
diffuse lymphatic tissue
Lamina propria
Capsule: C.T.

50. Tonsil

51. Mononuclear phagocyte system (Study by yourself)
monocyte
young monocyte
Bone marrow
Blood
CT: macrophage
Liver: Kuffer cell
Lung: dust cell
Nerve tissue: microglia
Osseous tissue: osteoclast
Skin: Langerhans cell
Tissues or organs

52. Function of MPS: phagocytosis participate in immune reaction
secrete bioactive substances