Lymphatic Organs

Question 1

Tonsils

Answer 1

• covered with epith. infiltrated with lymphocytes, mostly B-lymphocytes
• epithelium called reticular epithelium
• contain lymphatic follicles:
  
  • primary: without germinal center
  • secondary: lighter stained germinal center, cell in center are lymphoblasts
  • lymphocyte corona: darker, surrounds center
• follicles mostly B-lymphocytes
• interfollicular area mostly T-lymphocytes
• tonsillar crypts

Question 2

47. Palatine tonsil (HE)

Answer 2

• epithelium: Stratified squamous non-keratinized
• crypts: Deep branching
• capsule: Connective tissue
• striated muscle + serous-mucous glands on periphery

Question 3

46. Lingual tonsil (HE)

Answer 3

• epithelium: Stratified squamous non-keratinized
• crypts: very short
• no capsule
• striated skeletal muscle
• mucous glands
• CT
• excretory ducts drain into base of crypts

Question 4

48. Pharyngeal tonsil (HE)

Answer 4

• epithelium: Pseudostratified ciliated columnar
• crypts: not so deep
• capsule: thin fibrous CT
• goblet cells

Question 5

42. Palatine tonsil (B-cell, Tcell immunocytochemistry)

Answer 5

• B-cells and T-cells have different membrane proteins
• B-cell ⇒ CD3
• T-cell ⇒ CD20
• reddish-brown chromogen⇒ positive

Question 6

43. Thymus (HE)

Answer 6

• no follicles
• capsule: thin CT
• capsule extends as trabeculae ⇒ lobules
• cytoreticulum: epithelial reticulum
• cortex: more basophilic ⇒contain THYMOCYTES
• medulla: more lightly stained ⇒ contains large lymphocytes
• Hassal’s bodies
• macrophages + small vessels

Question 7

Hassal’s bodies

Answer 7

• degenerating epithelial cells
• eosinophilic
• secrete: cytokine, thymic stromal lymphopoietin

Question 8

44. Thymus (involuted, fatty) (HE)

Answer 8

• contains mainly adipose tissue

- some lymphatic tissue islands + Hassal’s bodies

Question 9

15. Lymph node (HE)

Answer 9

• capsule: CT with trabeculae
• cortex ⇒ paracortex ⇒ medulla
• paracortex: T-cell rich region + interdigitating dendritic cells ⇒ present antigens
• cortex: lymphatic follicles + interfollicular area
• medulla: medullary sinuses + medullary cords
• medullary cords: plasma cells + reticular cells + macrophages + B-lymphocytes
• sinuses: subscapular + intermediate + terminal
• hilum: CT + nerves + blood vessels + efferent lymohatic vessels
• framework: reticular connective tissue
• HEV in paracortex
• basal membrane of medullary sinus is fenestrated⇒ allows communication between sinuses and cords

Question 10

HEV

Answer 10

• high endothelial venules
• postcapillary venules in paracortex
• homing: process where lymphocytes can leave blood circulation and enter lymphatic tissue through wall of these venules

Question 11

Lymph node (toluidine blue)

Answer 11

• Tingible body macrophages
• plasma cells ⇒ below fibrous capsule surrounding lymph node, prominent nucleus
• Reticular cells ⇒ in medulla, cytoplasmic processes, flat nuclei
• Mast cells ⇒ in loose CT surrounding node

Question 12

Tangible body macrophage

Answer 12

• in lymph nodes in germinal center
• larger than lymphocytes
• contain B-lymphocytesin cytoplasm
• eccentrically placed nuclei

Question 13

45. Spleen (HE)

Answer 13

• capsule: mesothelial cells and CT with trabeculae
• framework: reticular CT
• White pulp: lymphocyte rich area
• Red pulp: blood-rich area, cords of Billroth + splenic sinuses⇒ stave cells
• splenic artery ⇒ trabecular arteries ⇒ central arterioles ⇒ penicilliform arteriole ⇒ capillaries ⇒ splenic sinusoids ⇒ trabecular veins ⇒ splenic vein

Question 14

White pulp in spleen

Answer 14

• Periarteriolar lymphatic sheath (PALS)⇒ aggregation of lymphocytes surrounding central arteriole, T-dependent area
• Malphighian nodule ⇒ contains germinal center, surrounding PALS and central arteriole, B-dependent area
• Marginal zone⇒ loose lymphoid tissue, B-dependent area, marginal sinuses, macrophages

Question 15

Cords of Billroth

Answer 15

• in red pulp in spleen

- contain macrophages, plasma cells, cellular elements of blood