Chapter 20: The Lymphatic System Flashcards
Functions of the Lymphatic System:
o Fluid recovery.
o Immunity.
o Lipid Absorption (lacteals)(chyle).
o Transportation.
Lymph:
o Clear, colorless (except in lacteals)
o Composition varies depending on location
o Originates as interstitial fluid surrounding capillaries—so similar to plasma
o Contains fluid, metastatic tumor cells, hm, pathogens, WBCs, lymphocytic highway!!!
Lymphatic Vessels:
Lymph Capillary
o Dead-end tubes.
o More permeable than capillaries.
o “shingle” arrangement of endothelial cells.
o Anchoring filaments that pull open cells when increase in fluid.
o Reabsorb approximately 2 to 4 liters of interstitial fluid.
o Present in all tissues except:
o CNS.
o Bone marrow, bones, teeth.
o Cartilage, epidermis, cornea.
o Superficial Lymph Vessels: Are located in the subcutaneous layer deep to the skin; in the areolar tissues of the mucous membranes lining the digestive, respiratory, urinary, and reproductive tracts; and in the areolar tissues of the serous membranes lining the pleural, pericardial, and peritoneal cavities.
o Deep Lymphatic Vessels: Accompany deep arteries and veins supplying skeletal muscles and other organs of the neck, limbs, and trunk, and the walls of visceral organs.
Lymph Pathway from Smallest to Largest:
o Lymph Capillaries drain into larger lymph vessels, then drain into lymph trunks, then into lymph ducts (right lymph duct, thoracic duct), then lastly into the subclavian veins.
Cisterna Chyli:
o Located in the superior-medial abdominal cavity.
o Drains the head, arm, and thorax.
Forces Driving Flow of Lymph:
o Rhythmic contractions of lymph vessels:
o Lymph fluid stretches lymph vessel.
o Automatic contraction of smooth muscle in lymphatic vessel wall.
o VALVES prevent backward flow!!!
o Skeletal muscle pump.
o Respiratory pump.
o Arterial pulsation.
o Rapidly flowing blood of subclavian veins.
Lymphatic Tissue:
o Lymphatic tissue = connective tissue that is dominated by lymphocytes
o Diffuse lymphatic tissue.
o Lymphatic follicles= lymphatic nodules.
o Diffuse Lymphatic Tissue
o Scattered lymphocytes (“sidewalk meeting”)
o MALT (mucous-associated lymphatic tissue)
o BALT (respiratory tract)
o GALT (digestive tract)
o Lymphatic Follicles (“town meeting”)
o Dense oval-shaped structures
o No capsule, lots of lymphocytes!
o Can stand alone, appear in clusters (Peyer’s patches), or appear inside other organs (e.g., lymph nodes, tonsils, spleen)
Specialized Cells:
o Lymphocytes:
o Natural Killer Cells (5%).
o T-lymphocytes = T-cells (80%).
o B-lymphocytes = B-cells (15%).
o Macrophages:
o Phagocytes derived from monocytes.
o Alert the specific immune system (APC).
o Other antigen presenting cells (APCs):
o Dendritic cells (e.g., Langerhan cells).
o Reticular cells:
o Build stroma (reticular fibers = EC fibers).
Lymphatic Organs:
o Primary lymphatic organs —where B and T lymphocytes become immunocompetent.
o Red Bone Marrow (maturation of B-cells).
o Thymus gland (maturation of T-cells).
o Secondary lymphatic organs: Tonsils.
o Lymph nodes: Filter LYMPH.
o Spleen: filters BLOOD.
Red Bone Marrow:
o Hemopoiesis for all blood cells.
o Red-marrow contains fat, reticular cells, developing blood cells and blood sinusoids.
o B-cells become immunocompetent.
Thymus:
o Bilobed gland in superior mediastinum between sternum and aortic arch
o Very large at birth, continues to grow until adolescence, undergoes involution (degeneration) and infiltration with fat during adulthood.
o Where T-lymphocytes develop immunocompetence.
o Also an endocrine gland.
o Thymosin, thymopoietin, thymulin.
Secondary Lymph Organs:
Tonsils
o Partially encapsulated, crypts are a distinguishing feature (“trap”).
o Located in mucous membranes protecting the pharynx (throat).
o Contain lymphatic follicles.
o Pharyngeal tonsil (1) (adenoid), Palatine tonsils (2), Lingual tonsils (several), Tubal tonsils (several—very tiny).
Secondary Lymph Organs:
Lymph Nodes
o Filter Lymph.
o Important role of activating the specific immune system.
o Structure:
o Several afferent lymphatic vessels leading in, but only 1-2 efferent vessels going out.
o Stroma = reticular fibers, cortex, medulla.
o Parenchyma = LYMPHOCYTES, macrophages, dendritic cells, etc.
o All lymph fluid passes thru lymph nodes!!!
o WBCs get in & out of blood vessels easily.
Lymphadenitis:
o Inflammation, swelling, and enlargement of lymph nodes. o Infected lymph nodes (buboes). o Tender. o Enlarged, swollen, but not firm. o Movable. o Cancerous lymph nodes (lymphomas). o Non-tender (usually painless). o Enlarged, swollen, but firm. o Appears firmly attached to underlying tissue.
Secondary Lymph Organs:
Spleen
o Large organ (1) in left upper quadrant
o Stroma
o Thin capsule containing smooth muscle
o Trabeculae and lots of reticular fibers
o Parenchyma
o White pulp: Lymphocytes and macrophages surrounding ingoing arteries like a “sleeve”.
o Red pulp: Leaky sinuses where blood flows slowly.
o Functions:
o FILTERS THE BLOOD:
o Removes dead/defective RBCs.
o Removes pathogens, toxins and debris.
o Blood reservoir:
o Smooth muscle in capsule contracts.
o Splenic volume decreases 40-50 percent in exercise.
o Platelet reservoir (1/3 of body supply).
o Produces RBCs in fetus (possibly later).
o Immune functions:
o Immune surveillance.
o Lymphocyte proliferation and activation.
