Lymphatic System

Description:	UCI Histo test 3
Category:	Histology
Created by:	droid on 2009-10-22

Question	Answer
3 purposes of lymphatic system	immune response, maintenance of body fluids, extramedullary heatopoiesis
lacteals	lymphatic capillaries
are lymphatic vessels fenestrated?	NO
flow of lymph	lymphatic capillaries to lymph vessels to lymph nodes to right lymphatic duct or thoracic duct
what is the largest lymph vessel in body	thoracic duct
where do the right lymphatic duct and thoracic duct drain	right and left subclavian veins respectively
structure of lymphatic cappillaries	single layer of attenuated endothelial cells with an incomplete basal lamina
what is lymphedema	elephantitis
causes of lymphadema	genetic or injury to lymphatic vessels (surgery, radiation therapy (breast cancer particularly); filariasis; cellulitis
filariasis	a parasitic infection causing lymphedema
treatment for lymphedema	decongestive therapy, compression, use of home sequential gradient pumps
lymphangitis	lymph vessel inflammation (usually streptococcus) from bacterial infection of lymphatic system; can lead to septicemia; can come from tumors, mastectomy, leg vein removal, or tinea pedis (foot fungus infection)
what do NK cells do	kill tumor cells, virally infected cells, bacteria, and parasites
which immune system is majorly affect by the lymphoid system	adaptive (innate is not)
IgD	activates B-cells
IgE	degranulates mast cells and basophils
IgG	opsonin, NK cytotoxicity
primary lymphoid organs	Thymus, prenatal/postnatal bone marrow, fetal liver
secondary lymphoid organs	lymph nodes, spleen, MALT, postnatal bone marrow
Encapsulated (dense) lymphatic organs	thymus, lymph nodes, spleen
unencapsulated (diffuse) lymphatic organs	MALT, BALT, GALT, tonsils
MALT, BALT, and GALT stand for what	mucosal associated lymphoid tissue, bronchial..., gut...
function of thymus	immunological competence of T cells, elimination of self-reactive T cells, and MHC (HLA) recognition
thymic lobes	2 lobes arising from endoderm and mesoderm
lobules	incomplete divisions of the lobes formed by septa (trabeculae)
trabeculae	septa
thymus capsule	dense collagenous connective tissue covering the thymus
cortex of thymus	T cell education, elimination of self-reactive T cells, MHC recognition; contains thymocytes, macrophages, and epithelial reticular cells; appears dark due to lots of T cells
thymocytes	immature T cells in the cortex to be educated
2 steps of cell instruction in the cortex of thymus	1)maturation stimulate by hormones produced by epithelial reticular cells 2)testing the ability to recognize self-MHC I/II and self epitopes (mediated by type II/III epithelial reticular cells and bone marrow dendritic APC's
function of macrophages in cortex	phagocytose apoptosed T cells
how many lymphocyte clones are formed during embryonic development	10 quadrillion
two ways to take out self-reacting t-cells	clonal deletion and anergy (inactivation)
TCR complex is composed of what	CD3 and either CD4 or CD8
medulla of thymus	lightly stained; full of Hassall's corpuscles and immunocompetent T cells
how do T cells leave medulla	via venules and efferent lymphatic vesseles; migrate to secondary lymphatic structures
hassall's corpuscles	composed of type VI epithelial reticular cells; increase with age; fxn unknown
reason for blood-thymus barrier	prevent developing T cells from contacting blood-borne macromolecules
how does the blood get to the thymus	vessels go through the trabeculae into the corticomedullary jxn, where they form capillary beds that penetrate the cortex
thymic cappilaries have what three features	a continuous endothelium, a thick basal lamina and adjacent epithelial reticular cells
what can cross the blood thymus barrier	self-macromolecules to participate in self-recognition of T-cells
Epithelial reticular cells in the Cortex (Types I-III	Isolate the Cortex of the thymus and prevent maturing T cells / Thymocytes from exposure to foreign antigens. Synthesize hormones (thymosin, serum thymic factor, and thymopoietin) that contribute to thymocyte maturation.
Epithelial reticular cells in the Medulla (Types IV-VI)	Assist in isolating the Cortex from Medulla (Type IV) to prevent maturing T cells / Thymocytes from exposure to foreign antigens. Type VI form Hassall’s corpuscles.
Thymic involution	atrophy of the thymus with age
lymph node size and contents of parenchyma	<3cm; T cells, B cells, APC's and macrophages
type of lymph vessel valves	semilunar
flow of lymph in lymph vessels	afferent lymphatic vessels, subcapsular sinuses, cortical sinuses (paratrabecular) which parallel the trabeculae, medullary sinuses, efferent lymphatic vessels
location and purpose of high endothelial venules in lymph node	in the paracortex; provide acces for lymphocytes to enter lymph node from vascular system
postcapillary venule location and purpose in lymph node	located in cortex; provide exit for lymphocytes from the lymph node into the vascular system
lymph node capsule	collagenous connective tissue surrounding lymph node; forms trabeculae upon vagination into lymph node
lymph node trabeculae	subdivide the outer lymph node cortex into incomplete compartments
cortex of lymph node	subdivided by trabeculae; houses B cell rich primary and secondary lymphoid nodules
primary cortical lymphoid nodules	spherical aggregates of virgin and memory B cells in the process of entering/leaving the lymph node
secondary cortical lymphoid nodules	pale staining and houses a germinal center; form from antigenic challenge, sites of memory B cell and plasma cell generation
lymph node corona	adjacent to a germinal center; composed of a dense accumulation of lymphocytes migrating away from their site of origin
dark zone in secondary cortical lymphoid nodules	site of intense B cell proliferation
light zone in secondary cortical lymphoid nodules	where proliferated B cells migrate, express Igs, do class switching, are exposed to antigen-bearing follicular dendritic cells, and are killed if they fail; survivors exit as memory B's or plasma cells
paracortex of lymph node	houses T cells (thymus dependent); location of adaptive immune response
steps of paracortex adaptive immune response	T cells migrate by the HEVs, Dcs/APCs migrate to paracortex to present their epitope-MHC complexes to T-helpers; T-helpers proliferate and expand the paracortex; T-h migrate to medullary sinuses, and exit the node
medulla of lymph node	large, convoluted lymph sinuses surrounded by lymphoid cells that are organized in clusters called medullary cords
medullary cords	located in lymph node medulla; contain lymphocytes, plasma cells and macrophages; lymphocytes must go through the medullary sinuses to exit the node via the efferent lymphatic vessels
fxns of spleen	filter blood, form lymphoid cells, eliminate blood-borne antigens, destroy old platelets and RBCs, fetal hematopoiesis, possible adult hematopoiesis
capsule, trabeculae, and hilum of spleen	just like the same in the lymph nodes
function of red pulp of spleen	filter the blood
components of red pulp of spleen	splenic sinuses and splenic cords of billroth
white pulp	PALS housing T cells and lymphoid nodules housing H cells
trabecular arteries in spleen	source of PALS
PALS	periarterial lymphatic sheath
trabecular arteries and PALS	trabecular arteries get smaller and smaller until they turn into PALS
PALS composed of	T cells to watch the blood
central artery	the vessel occupying the center of the PALS
penicillar artery	where the central artery terminates it loses its PALS and divides further into a series of short parallel branches, called penicillar arteries, which enter the red pulp
lymphoid nodules of spleen	found in white pulp; enclosed within the PALS, composed of B cells; displace the central artery to a peripheral position; may display germinal centers, indicating atigenic challenge
marginal zone in spleen	separates white pulp from red pulp composed of mainly B cells but also plasma cells, T cells, macrophages, and APC; this is the location where APC contact the blood
Splenic reticular fiber network	attached to the capsule and trabeculae; puts the right type of cells in contact with eachother
MALT	mucosal associated lymphatic tissue; nonencapsulated lymphoid nodules in the mucosa of th GI, respiratory, and urinary tracts; response to airborne/injected antigens; GALT, BALT, tonsils
GALT	gut associated lymphatic tissue; composed of B cells surrounded by T cells and APCs; no afferent lymph vessels, but efferent lymph drainage is present
peyer's patches	GALT in the ileum
M cells	microfold cells; found in ileum adjacent to peyer's patches; thought to capture antigens and transfer them to macrophages in peyer's patches
BALT	bronchial associated lymphoid tissues; similar to peyer's patches but in bronchi; no afferent vessels; efferent lymph drainage is present; mostly B cells; M cells are also present
tonsil	incompletely encapsulated aggregate of lymphoid nodules; mostly T and B lymphocytes
what are the three tonsils	palatine, pharyngeal, and lingual
palatine tonsils	composed of lymphoid nodules inside 10-12 crypts, which invaginate the tonsilar parenchyma
germinal centers are indicative of what and are found where?	indicative of B cell activation by antigen and proliferation; found in tonsil