Lymph System Histo Flashcards
fnctns of lymphatic system
- drain excess interstitial fluid
- provide alt transport routes for hormones, nutrients, and waste
- immune respone
components of lymphatic system
- lymphatic vessels
- lymphocytes and variety of supporting cells
- diffuse lymphatic tissue
- lymphatic nodules
- lymph nodes
- spleen
- bone marrow
- thymus
lymphatic vessels
- begin as networks of blind ended capillaries in microcap beds
- lymphatic caps form network with loose CT
lymphatic capillaries
- endothelial tubes lack continuous basal lamina, is highly permeable
- collect excess protein rich ECF from EC spaces->lymph once it enters lymphatic vessels
do lymphatic vessels have valves?
yes
lymphatic vessels un
ite to form two main channels
- thoracic duct: largest lymph vessel, drains majority of body
- R lymphatic duct: drains UR limb, R thorax, R neck, R head
*both drain to venous angle
cells of the lymphatic system
lymphocytes
-effector cells, 3 types
3 types of lymphocytes
- B lymphocytes
- T lymphocytes
- NK cells
B lymphocytes
- 20-30% of circulating lymphocytes
- membrane bound B cell receptor: immunoglobulin
- activated B cells (plasma cells) secrete non membrane bound form of Ig= antibodies
- involved in humoral immunity
T lymphocytes
- mature in thymus
- 60-80% of circulating lymphocytes
- cell mediated immunity: release cytokines against intracellular pathogens
NK cells
- 5-10% of circulating lymphocytes
- potent killers of certain types of cells: virally infected and malignant cells
- innate immunity
supporting cells
- interact with lymphocytes, antigen presentation and regulation of immune responses
- monocytes, neutrophils, basophils, eosinophils, dendritic cells, follicular dendritic cells, langerhans cells, reticular cells, epithelioreticular cells
where is diffuse lymphatic tissue found
- alimentary canal
- respiratory assages
- genitourinary tract
diffuse lymphatic tissue
- not surrounded by a CT capsule
- lymphocytes, plasma cells,fibroblasts, and eosinophils found in lamina propria at these sites
- lymphocytes most abundant
lymphatic nodules/follicules
- discrete concentrations of lymphocytes contained in meshwork of reticular cells
- sharply defined but not surrounded by CT capsule
- primary and secondary nodules
primary vs secondary nodules
- primary: resting lymphocytes, small
- secondary: 1. germinal center: response to antigen, develops when lymphocyte binds to antigen, returns to primary nodule and proliferates, light staining bc euchromatin, contain follicular dendritic cells
2. mantle zone: encircle germinal center
where are aggregations of lymphatic nodules specifically found
- tonsils: form ring of lymph tissue at entrance of oropharynx and nasopharynx -> waldeyers ring
- peyers aptches: in ileum of SI, numerous aggregations of lymphatic nodules and T and B lymphocytes
- veriform appendix: from cecum of LI
lymph nodes
- small, bean shaped encapsulated lymphatic organs
- along pathway of lymphatic vessels
- filter lymph priot to its return to blood circ
afferent lymphatic vessels
convey lymph toward the node, enter at the convex surface
efferent lymphatic vessels
convey lymph away from node, leave at hilum
lymph node stroma
- capsule: DCT
- trabeculae: DCT extending from capsule
- reticular tissue: reticular cells and fibers form fine supporting network
cells of reticular meshwork
- reticular cells: synth and secrete reticular fibers and ground substance (supporting role and produce substances that attract T and B cells and dendritic cells
- dendritic cells: bone marrow derived APCs (presentantigen to T cells)
- macrophages: act as phagocytes and APCs
- FDCs: thin. hairlike branching of cytoplasmic processes
parenchyma of lymph node is divided into
- cortex: outer portion, (superficial cortex: outer part, just deep to capsule, contains germ centrs, deep cortex: btwn sup and medulla, contains majority of T cells in lymph nodes
- medulla: medulla cords (contain B cells, macros, dendritic cells, plasma cells) separated by medullary sinuses (conerge near hilum and drain into efferent lymph vessels
lymph node filtration
occurs through interconnected channels
- subcapsular (cortical) sinus
- trabecular sinuses
- medullary sinuses
* high endothelial vessels (lymphocytes civered in blood enter node via HVE in deep cortex
flow from blood thru node
HVE-deep cortex-superficial cortex-medulla-eff lymph vess
flow from lymph thru node
aff lymph vess-subcapsular sinus-trabecular sinuses-medullary sinus-eff lymph vess
thymus
- in sup mediastinum, ant to heart
- at puberty: T cell differentiation and proliferation reduced, organ mainly replaced with adipose tissue
structure of thymus
- capsule: thin CT
- trabeculae: extends from cap into parenchyma, forms thymic lobules
- thymid lobules: 1. cortex: basophilic, contain thymocytes and macrophages, 2. medulla: inner portion, lighter staining, type VI epithelioreticular cells (form hassals corpuscles
thymic hassalls cells
have keratohyalin granules so eosinophilic, center is fully keratinized cells
spleen
- largest lymphatic organ
- rich blood supply-filters blood (lymphnode for blood)
- enclosed in DCT capsule which trabeculae extend from into parnchyma
- contains 1. red pulp (blood filtration and splenic sinuses separated by splenic cords) 2. white pulp (lymphatic tissue, mostly lymphocytes, basophilic w/ H&E, central a (br of splenic a) surrounded by PALS
