LYMPHATIC SYSTEM Flashcards
FUNCTIONS
-immune surveillance and defense against foreign substances
-Provides immune tolerance, distinguishing between “self” and “non-self”.
- Absorbs lipids into small lymphoid vessels (lacteals) in the intestinal villi for distribution of fatty lymph to the blood stream and liver.
* Maintains fluid balance by accumulating tissue fluid and white blood cells in lymph vessels and returning them to the blood.
PRIMARY LYMPHOID ORGANS
- SECONDARY LYMPHOID ORGANS
- PRIMARY LYMPHOID ORGANS- convert stem cells to the mature cells
- Bone marrow – lymphocyte stem cells
* T and B- lymphocytes originate; B- cells mature and go to secondary lymphoid organs ; T- cells move into the thymus. - Thymus - site of T-cell maturation.
- SECONDARY LYMPHOID ORGANS- activation and proliferation
- Tonsils – Lymphoid tissue with germinal centers that can produce lymphoid cells.
- Spleen – site where T & B lymphocytes interact with bloodborne antigens stimulation and cell division. cleanses the blood
Lymph nodes
Diffuse lymphoid tissues
– junction of major lymphatic vessels; sites where both T&B lymphocytes interact with blood-borne antigens – stimulation and & cell division.
- Diffuse lymphoid tissues
- MALTs – Mucosa associated
lymphocytic tissues. - GALTs – Gastrointestinal associated lymphocytic tissues
- BALTs – Bronchial associated
lymphocytic tissues.
MAJOR LYMPHOID CELLS TYPES:
- B-lymphocytes APC – differentiate into memory B cells and plasma
cells. - T-lymphocytes – differentiate into helper, memory, cytotoxic cells.
- Plasma cells - mount an immune response.
- Macrophages APC – phagocytose foreign matter.
- Dendritic cells APC – involved in initiation of immune response.
HIGH ENDOTHELIAL VENULES (HEVs):
- Location: Appendix, tonsils, Peyer’s patches and lymph nodes.
- Endothelium morphology: Simple cuboidal.
- transport of lymphocytes through the endothelium of the HEVs,
PARENCHYMA:
- STROMA:
- PARENCHYMA:
- The cells and tissues of an organ that perform the function of the organ.
- STROMA:
- The supporting framework of an organ, made of connective tissue.
- Free cells (mainly lymphocytes)
- Reticular cells – produce reticulin fibers
- Reticulin fibers –allows fluid (lymph) to pass through; also the CT support for the cells making up the parenchyma of the tissue.
what is LYMPH
- Lymph
- Clear, watery fluid in the lymphatic vessels.
- Interstitial fluid (IF)
- Fills the spaces between the cells.
Lymph vessel
Originate as lymphatic capillaries in the tissue.
* Carry lymphatic fluid to and from the lymph nodes, and towards the heart.
Accumulate tissue fluid, called lymph.
* Thin-walled vessels lined with endothelium
* Highly permeable
* Valves are present to ensure that the lymph will only flow one way – back to the bloodstream.
- Two main lymphatic trunks the empty into the subclavian vein
- Right lymphatic ducts
- Thoracic ducts
LYMPHATIC VESSEL AND VEIN
- Lymphatic and blood networks are close, but independent of each other
- Lymphatic vessels pickup fluid.
- The vein will have red blood cells in it
- Lymphatic vessels have more valves and lack pericytes.
LYMPHATIC PUMP
- Rate of flow 3L/day. travel at a slower speed
- Mechanisms that establish the pressure gradient for fluid flow:
- Breathing movements
- Skeletal muscle contractions.
CIRCULATION OF LYMPH
- Fluid exchange between capillaries and lymphatic vessels.
- Lymphatic vessels contain lymph nodes located at intervals
- Returns to venous circulation by way of subclavian veins.
THYMUS
- Flat, lymphoid organ in middle of upper chest up to neck
- composed of T-cells, reticular cells and some macrophages
- Produce hormones, thymosin that promotes maturation of T-lymphocytes.
- bigger when younger as you get older it is replaced by adipose.
- Presence of capsule
- Morphology: DICT
- Lobulated with CT septae
- Outer thymic cortex (C) basophilic:
- Nurse cells – support T-cell maturation (eosinophilic)
- Thymocytes, T-cells.
Inner thymic medulla (M) eosinophilic:
* Hassal’s corpuscles are keratinized dead epithelial cells migrating inwards from cortex.
* Self reactive T-cells are removed from here.
when youre young your thymus has * Lobules, cortex and medulla, septae
when you get old
* Fatty infiltration
* Lymphocyte depletion
LYMPH NODE
- Spherical or kidney-shaped lymphoid organ
- Aggregates along the lymphatic vessels.
- Location: Axilla, groin, neck, lung, hila, paraaortic area
- Main function: makes up a series of in-line filters
- Stimulate an immune response to antigens in the lymph.
- Defense against microorganisms.
- Prevent spread of tumour cells.
- STROMAL COMPARTMENT:
- Packed with lymphocytes and antigen presenting cells
(APCs). - LYMPHATIC OR SINUS COMPARTMENT:
- Act as a sieve/filter for antigens.
- VASCULAR COMPARTMENT:
- Sinusoids and blood vessels present.
- Delivers nutrients and lymphocytes to the nodes.
contains
* Capsule
* Cortex
* Medulla
* Hilum
* Afferent and efferent lymphatic vessels.
what is the path of the lymph flow through a lymph node
Afferent lymph carry lymph to peripheral tissues and penetrate lymph capsule
-Lymph sent to subcapsular space. Dendritic cells initiate immune system
-lymph flows to outer cortex that has B cells
-lymph flows through lymph sinus in deep cortex with T cells
-then to medullary sinus in lymph core with B cells and plasma cells
-efferent lymph leave the lymph at the hilum into venous circulation
what does the microanatomy of the lymph node look like
- has lymphocytes and reticulin CT.
- Follicles with germinal centers in the cortex.
- Capsule: Morphology: DICT
- Trabeculae:
- CT from the capsule extending into parenchyma.
- Afferent lymphatics.
- Subcapsular space.
- Hilum: Efferent lymphatics to the
lymphatic ducts. - the indentation of the node
