Lymphatic System Flashcards
Function of lymphatic system
Secondary defense system
Methods of defense
- Humoral immune system
- Cell-mediated immune system
- Filtration of lymph and blood
Primary method of defense
Epithelial cells
Primary defense aka?
Innate / non-specific
Secondary defense aka?
Immune / acquired / specific
2 types of secondary defense
- Humoral
2. Cell mediated
Cytokines are?
Chemical messengers
3 cells/molecules involved in humoral defense
- B lymphocytes
- Antibodies
- Plasma cels
2 cells/molecules involved in cell-mediated defense
- T lymphocytes
2. Cytokines
2 classifications of lymphatic tissue
- Diffuse
2. Dense
Diffuse lymphatic tissue is found in?
- Respiratory tract
2. Lamina propria of GI tract
Diffuse lymphatic tissue
Loosely scattered lymphocytes beneath epithelial layers
Dense lymphatic tissue
More compact, spherical structures (nodules/follicles)
Dense lyphatic tissue is found in?
Submucoa of GI tract
What are aggregated lymph nodules?
Accumulations of many nodules
Example of aggregated lymph nodules
Peyer’s patches
Peyer’s patches are found in?
Wall of intestines, especially ileum
What are tonsils?
Areas where lymphoid tissue is very closely associated with epithelium
How do you recognize a tonsil?
Lymphocytes invade epithelium
What are crypts?
Deep invaginations of epithelium
Crypts are found in what type of lymphatic tissue?
Tonsils
Crypts are found in the palatine tonsils of all species except?
Carnivores
Difference between lymphatic tissue and lymphatic organs?
Lymphatic organs have CT capsule, lymphatic tissue does not
Lymph nodes are usually shaped how?
Bean-shaped with hilus
Lymphocenter
Constant locations of lymph nodes
Lymph node structure
- Capsule
- Stroma
- Cortex
- Paracortex
- Medulla
- Lymph flow
Capsule of lymph node
Surrounds node
Parenchyma is the?
Functional part of an organ
Stroma of lymph nodes
Trabeculae from capsule divide parenchyma into smaller compartments
Stroma contains a network of?
Reticular fibers
Reticular fibers are type ___ collagen
Type III
Cortex is the?
Outer region of parenchyma
Species in which cortex is not the outer region of parenchyma
Swine and elephants
Cortex contains?
- Lymph nodules/follicles
2. Lymph sinuses
Appearance of primary lymph nodules
Homogenous
2 types of lymph nodules
- Primary
2. Secondary
Which type of lymph nodules contains a germinal center?
Secondary
What is a germinal center?
A lighter center of a lymph nodules which indicates previous antigenic exposure
Why do germinal centers have lighter center?
Presence of activated lymphocytes (which ave more vesicular nucleus and more cytoplasm → pale)
2 possible fates of activated lymphocytes in germinal center
- Become plasma cells and secrete antibodies
2. Become memory cells
2 types of lymph sinuses
- Subcapsular
2. Trabecular
Paracortex is?
Poorly defined zone in deep center next to medulla
Paracortex contains mostly?
T lymphocytes
Thymus dependent zone refers to?
Paracortex
T lymphocytes are produced in?
Thymus
How do T cells enter paracortex?
Via HEVs
HEV stands for?
High endothelial venules
What are HEVs?
Small vessels with unusually tall endothelium
Lymph arrives via what type of vessels?
Afferent vessels
Medulla is the?
Inner region of lymph node
Medulla contains?
- Medullary cords
- Medullary sinuses
- Trabeculae (from cortex)
Lymphatic tissue in medulla is in the form of?
Medullary cords
Medullary cords contain?
- Lymphocytes
- Plasma cells
- Macrophages
- Reticular cells
What are medullary sinuses?
Lymph sinuses along medullary cords
Afferent vessels enter capsule where?
Convex surface of node
Afferent vessels drain into?
Subscapular and trabecular sinuses
Lymph flow
Percolates through cortical sinuses into medullary sinuses
Where are lymphocytes added to lymph?
Medullary sinuses
How does lymph penetrate cortex and medulla?
Leaks from sinuses
Efferent vessels leave organ where?
Hilus
Blood vessels enter and depart where?
Hilus
