Lymphatic system Flashcards
What does the lymphatic system act as?
Secondary defense system
What are the 3 ways the lymphatic system acts as a defense system?
Humoral immune system
cell mediated immune system
Filtration of lymph & blood
What is the difference between humoral & cell mediated immune systems?
Humoral: B lymphocyte antibodies
Cell mediated: T lymphocytes
What are the 2 types of lymphatic tissue?
Diffuse
Dense
Where is diffuse lymphatic tissue often found?
Lamina propria of
G.I. tract
Where is dense lymphatic tissue often found?
submucosa of G.I. tract
Are lymph nodules made of dense or diffuse lymphatic tissue?
dense
What are peyer’s patches?
accumulation of nodules
In what tissue can lymphocytes be seen invading epithelium?
Tonsils
What are the structural components of a lymph node?
Capsule
Stroma
What is the stroma?
Trabeculae that arise from the capsule and divide the parenchyma
What is the cortex of a lymph node?
Outer region of parenchyma
Where are lymph nodules located?
In cortex
What is the difference between a primary and secondary nodule?
Primary has homogenous appearance and secondary have a germinal center due to previous antigenic exposure (active lymphocytes)
What does the paracortex contain?
T lymphocytes
Why is the paracortex considered a thymus dependent zone?
T lymphocytes are produced in the thymus
What are high endothelial venules?
Vessels that transport T lymphocytes from the thymus to the paracortex
What is different about pigs and elephants in regards to lymph nodes?
Medulla is on outside
Cortex is on inside
What are medullary cords?
Lymphocytes, plasma cells, macrophages and reticular cells located in the medulla
What is the subcapsular sinus?
Space between capsule and lymphatic nodule
What are the medullary sinuses?
Lymph sinuses between medullary cords
Describe lymph flow
Afferent vessels drain to subcapsular and trabecular sinuses (nodules)
Lymph travels from cortical sinuses to medullary sinuses
Efferent vessels transport lymph out
What happens to B cells after being presented with an antigen by a dendritic cell?
B cell becomes activated & divides
Some B cells become plasma cells & some move to medullary cords to secrete antibodies
What are hemal nodes?
Lymphatic organs that filter blood
Where are hemal nodes found?
Associated with visceral organs
What is the function of the spleen?
Removes old RBCs
Removes antigenic material
What are the components of the spleen?
Capsule
Dense connective tissue
Smooth muscle
Trabeculae
What are the big differences between spleen tissue and lymph nodes?
Spleen has more smooth muscle
Spleen does not have a distinct cortex & medulla
What is the white pulp of the parenchyma?
Any lymphatic tissue in the spleen
What is the PALS?
Periarteriolar lymphoid sheath that surrounds the central artery in the parenchyma
Aside from the artery what else is contained inside the PALS? How does that relate to the spleen?
T lymphocytes
PALS is thymus dependent zone of spleen
What is the red pulp of the spleen?
Venous sinuses and splenic cords
What is a sign that extramedllary hemopoiesis is occurring in the spleen?
Megakaryocytes
What is the area between the white and red pulp called?
Marginal zone
Why is the marginal zone important?
Immune response is initiated here
What are the types of spleens?
Defensive: little smooth muscle with lots of white pulp
Reserve: lots of smooth muscle with less white pulp
What type of spleens do ruminants have?
Between defensive and reserve
What is the only gland in the body with an epithelial stroma?
Thymus
How does the thymus act as an endocrine organ?
Produces thymopoietin which influences development of T lymphocytes
Does the thymus have nodules?
No
Describe the cortex of the thymus
Dense accumulation of developing T lymphocytes
Describe the medulla of the thymus
Thymic corpuscles
Less dense T lymphocytes
Does the thymus have any afferent lymphatics?
No
What is the Bursa of fabricius? Where is it located?
Location of hemopoiesis in birds
Located in dorsal wall of proctodeum
