Lymphoid System- Lecture 9/30/21 Flashcards
Primary lymphoid organs
Thymus and bone marrow
Secondary lymphoid organs (3)
MALT, lymph nodes, spleen
Bone marrow
Provide a protective environment for the development of immune competent B cells
Thymus
Provides a protective environment for the development of immunocompetent T-cells
Epitheliaoreticular cells
Supports the thymocytes, contribute to the blood thymus barrier
Hassall’s Corpsucles
Whorls of specialized epithelioreticular cells that reside in thymic medulla, poorly understood but appears to regulate T-cell development
Uncapsulated lymphoid organs (3)
- Tonsils
- Peyer’s patch
- appendix
Encapsulated lymphoid organs (2)
- Lymph nodes
- Spleen
Germinal center
Part of lymphoid nodule where the B-cells live/proliferate
Diffuse zone
Part of lymphoid that houses T-cells
MALT
Mucosa associated lymphoid tissue
Mucosa
Epithelia, surrounding connective tissue (lamina propria), muscle layer just deep to it
Submucosa
Layers underneath muscularis mucosa
Tonsil types
- Pharyngeal
- Palatine
- Lingual
Characteristics of palatine (lingual) tonsils
SSNKE epithelium, deep crypts, palatine and lingual histologically indistinguishable
Characteristics of pharyngeal tonsil
- Pseudostratified epithelia with no crypts
Peyer’s patch
Lives in the mucosa/submucosa of small intestine epithelium , simple columnar epithelium
M (microfold) cell
Specialized epithelia with basal invaginations and active pinocytosis to allow for maximal contact between immune cells and possible antigens
Appendix
Nodules line in the mucosa
Septa
In the thymus, separates the lobes of the thymus
Blood thymus barrier
Any cell in thymus that recognizes and antigen is killed, so if any pathogen were to get in the cell that recognizes it would be killed
Involuting thymus
Adult thymus, largely CT and Fat because inactive
Appendix functions (4)
- Immune surveillance
- Vestigal
- Endocrine organ
- Reserve of gut flora
Lymph node
- Range from 1mm -several CM
- Concentrated in neck, axilla and groin
- Filter lymph and expose antigen
Medullary cord
Loose CT, with highly cellular content
Medullary sinus
Venous channel running between cords, discontinuous endothelium, traversed by reticular fibers
Splenic cords and sinuses
Similar to lymph node, have blood cells in both, sinuses are not traversed by reticular fibers
Subcapsular sinus
Sinus that runs just under the capsule
Trebeculum
CT that supports the lymph node
High endothelial venules
Lymphocyte entry only, becomes leaky during cortical reaction
Spleen functions (6)
- immune response
- destroys damaged, senescent blood cells
- Sequesters monocytes
- Hematopoiesis
- Storage of platelets
- Recycling iron
Red pulp
Where the splenic cords and splenic sinuses are
White pulp
Contains the lymphatic double and the periarterial lymphatic sheath
PALS
Periarterial lymphatic sheath, surrounds the central artery
Trebecular artery
Surrounded by CT
Red pulp cords
- Loose CT and reticular fibers, blood enters cords first
Red pulp sinuses
- Venous channels lined by elongated discontinuous endothelial cells
Marginal zone
First place that RBCs encounter WBCs of the red pulp cord
