Lymphatic Tissues and Organs- Sum 6 Flashcards
lymphatic system
consists of: cells + tissues + organs
collectively form part of the immune/defense system to monitor and protect body from harm (microorganisms, foreign substances, tumor cells, transplanted cells, virus)
lymphatic tissue
very cellular with large numbers of lymphocytes
either primary or secondary
primary lymphatic tissues
donors to secondary
site of development and maturation
bone marrow
thymus
secondary lymphatic tissues
recipients from primary
site of immunological surveillance and formation of defense vs antigens/pathogens CONFRONTATION
MALT
mucosa-associated lymphatic tissue
- GALT (gut associated lymphatic tissues, in mucosa of GI tract)
- BALT (bronchus associated lymphatic tissue. in mucosa of respir tract)
- GU tract (mucosa tract)
- tonsils
secondary
examples of secondary
diffuse lymphatic tissue (MALT)
lymphatic nodules (MALT)
tonsils
lymph nodes (filter lymph)
spleen (filters blood)
diffuse lymphatic tissue
infiltrate
infiltrate lamina propria of
1. GI tract as GALT
2. respiratory tract as BALT
3. GU tract
diffuse lymphatics function
waiting to confront antigens or pathogens passing thru epithelium
is location of initial immune response
diffuse lymphatics structure
simplest, loose
reticular fibers
cells: B and T lymphocytes, monocytes, macrophages, plasma cells
primary lymphatic nodules
homogenous appearance
small lymphocytes
secondary lymphatic nodules
structure
mantle zone (MZ)= dark, small mature lymphocytes
germinal center = inner lighter zone, larger immature lymphocytes
-will swell and stimulate lymphocyte proliferatoin + plasma cell differentiate + antibody secretion
solitary lymphatic nodules
temporary
aggregates of lymphatic nodules
permanent
@ tonsils, lymph nodes, spleen, BALT, appendix, ileum
tonsils
aggregates of lymphatic nodules w/ B and T lymphocytes
@nasopharynx = pharyngeal tonsil/adenoid
@fauces = palatine
@dorsal surface of poster 1/3 tongue = lingual
pharyngeal tonsil
appearance
pseudostratified columnar with cilia
pleats, NO crypts
palatine tonsil
appearance
stratified squamous nonkeritanized
have crypts
lingual tonsils
stratified squamous nonkeritanized
have crypts
lymph nodes function
filter lymph before it passes into blood vascular system
lymph node structure
- capsule- dense irregular collagenous CT, trabeculae carry blood vessels and nerves into lymph nodes
- hilum- concave, where blood vessels and efferent lymphatic vessels leave node
- sinuses- lined by simple squamous endothelial-like cells to permit exit/entrance of sinus
parts of a sinus
lymph node
subcapular- deep to CT capsule
paratrabecular- surround trabeculae
medullary- wide and tortuous
lymph node framework
reticular tissue w/
- stellate reticular cells: like fibroblasts so syn/secrete coll III, processes wrap around bundles of reticular fibers to seal/isolate them from tissue parenchyma
- dendritic cells- antigen presenting cells monitor foreign substances
- macrophages- phagocytic, antigen presenting
- follicular dendritic cells- bind ag-ab complexes for long periods of time
lymph node parenchyma
cortex + paracortex + medulla
cortex contents
lymph nodes
B lymphocytes
dendritic cells
follicular dendritic cells
macrophage
plasma cells
paracortex contents
lymph node
T lymphocytes
postcapillary venules aka high endothelial venules (HEV)
B and T exit bloodstream via HEVs to para
B migrates to cortex
medulla contents
lymph node
-stellate reticular cells
-reticular fibers
-B lymphocytes (leave cortex > migrate to medullary sinuses > exit via efferent vessels)
-plasma cells
-dendritic cells
-macrophages
medullary sinuses contents
lymph node
- reticular fibers made by and covered by stellate reticular cell processes
- macrophages- piggy back stellate cells to phagocytose particulate matter
- lymphocytes
- plasma cells
- dendritic cells
thymus
where T lymphocytes mature
originate in bone marrow as immature > migrate to thymus to become immunocompetent in thymic cortex > migrate to thymic medulla > leave
thymus structure
2 lobes
- capsule - dense irregular CT
- trabeculae- partition thymus to form lobules
- lobules- has cortex and medulla (continuous w/ lobules of surrounding lobules)
thymus- has/has nots
- no afferent lymphatic vessles aka does not filter lymph
- no stellate reticular cells- has epithelial reticular cells
- no 3D reticular fiber framework- has epithelial reticular cell framework
- no lymphatic nodules- has cortex and medulla
- no B lymphs- has T lymphs
- no sinuses or sinusoids
type I epithelial reticular cells
thymus
form seal via occluden junctions around cortex
form sleeve around tunica adventitia of vessels
create antigen proof compartment for T lymphs in cortex
blood thymus barrier
cortical capillary endothelium + basal lamina + macrophages + type I epithelial reticular cells
to isolate developing T lymphs from macromolecules in blood
type II epithelial reticular cells
@mid cortex
branching, stellate shaped cells form meshwork/cytoreticulum
type III epithelial reticular cells
form seal b/t cortex and medulla
type IV epithelial reticular cells
establish barrier @ corticomedullary junction
type V epithelial reticular cell
form meshwork/cytoreticulum aka framework of medulla
type IV epithelial reticuluar cells
form thymic corpuscles (Hassall)
concentric, eosinophilic whorls @medulla
exhibit keratinization
reticular cells of thymus cortex
function
protect/guard
create an antigen free environment for maturing lymphocytes in the cortex
immuno-competent T Lymph
pathway
medulla
thymus
residence in:
1. deep cortex (paracortex) of nodes
2. PALS of spleen
3. GALT (Peyer’s patches) but mostly B
4. BALT mostly B some T
DiGeorge’s Syndrome
developmental disorder (thymic hypoplasia or aplasia)
so can’t produce T lymphocytes = death from infection
spleen
function
filters blood
site of B and T proliferation
site of blood cell elimination
spleen structure
- capsule
- trabeculae
- hilum
- CT Stroma
- parenchyma (white and red pulp)
white pulp
has PALS (T lymphs)
+ splenic nodules (B lymphs)
red pulp
splenic cords (of Billroth)
-stellate reticular cells, platelets, RBCs, WBCs, macrophages, plasma cells, dendritic
+
splenic sinuses/sinusoids
-blood cells
vascular supply to spleen
- trabecular arteries
- central artery w/ PALS
- splenic nodule
- penicillar arteriole
- pulp arteriole
- sheathed arterioles
- splenic sinuses
splenic circulation
blood filtered in splenic cords
old blood cells and particulates phagocytosed by macrophages in cords
