AP 3 Lymphatic System.txt

• -lymphatic vessels
• -lymph, the fluid
• -lymph nodes, cleanse fluid as it passes through
• -lymph organs: spleen, thymus, tonsils

the almost 3L of fluid that is forced out of the blood at the arterial ends of the capillary beds and remains behind in the surrounding tissue spaces. It also contains plasma proteins in it.

hydrostatic and colloid osmotic pressure

to transport leaked plasma proteins and fluids back to the cardiovascular system to ensure sufficient blood volume

drainage vessels that collect that protein containing interstitial fluid (Lymph) to return it to the bloodstream

when interstitial fluid enters the lymphatic vessels/lymphatics

• -milking action of skeletal muscle contraction
• -thoracic pressure changes due to breathing
• - rhythmic, pumping contraction of smooth muscle in vessel wall
• - one-way valves in vessels
• -3L of lymph enters bloodstream every 24 hrs

only to the heart

• -lymphatic capillaries
• -lymphatic collection vessels
• -lymphatic trunks
• -lymphatic ducts

• -beginning of the lymphatic vessels.
• -microscopic and blind-ended
• -weave all through the body except in avascular tissue (cornea, epithelial tissue layers of the skin), CNA, teeth, bone and bone marrow
• -permeable: easily allow limp, proteins, cell debris, pathogens and cancer cells in

• -they have collagen filaments that anchor it to connective tissues
• -they are made of endothelial cells that are loose and overlap each other
• -they have flaplike minivalves that allow fluid in when pressure outside of the capillaries is greater than that on the inside. when pressure inside is greater than outside, the valves close

• -specialized lymphatic capillaries in the villi of the intestinal mucosa
• -asborb the milky white digested fats from the intestine

the fatty lymph in lacteals which is also delivered to the blood via lymphatic system

• flows through larger, thicker-walled channels.
• capilaries > lymphatic collection vessels > lymphatic trunks > lymphatic ducts
• CVTD - Come Visit The Dog

• -have more internal valves
• -same 3 tunis as veins (Tunica interna, tunica media, and tunica externa) but thinner walled and anastomose (connect) more

• -formed by the union of the largest collecting vessels and drain large areas of the body
• -they are the paired (right and left) lumbar, bronchomediastinal (upper branches of the superior vena cave), subclavian and jugular and the singular intestinal trunk (inferior to the lumbar)

• -found in thoracic region
• -right lymphatic duct drains lymph from right arm and right side of head and thorax
• -larger thoracic duct drains lymph from rest of body: left side of thorax, left upper limb and head
• -both ducts drain lymph into venous circulation by entering subclavian veins on their respective side of the body
• -subclavians merge with jugulars to form brachiocephalic veins
• - left and right brachiocephalics merge to form superior vena cava which empties into heart

sac at lower end of thoracic duct which collects the lymph from the 2 large lumbar trunks that drain the lower limbs and from the intestinal trunk that drains the digestive organs

When lymph is blocked from returning to the venous circulation, localized swelling occurs but is eventually drained by regrowth of vessels that are not blocked

tropical parasitic worms clog lymph vessels, cause edema (swelling), sometimes extreme (example: legs or scrotum)

• -lymphoid cells
• -main warriors of the immune system arises in red bone marrow
• -mature into T-cells and B-cells that protect body against antigens

manage immune response and also destroy infected cells

-produce plasma cells which are clones and secrete antibodies

phagocytizing pathogens

capture antigen and bring back to lymph nodes

fibroblast like cells that produce reticular storm which is the network that supports the other cell types

• -net-like framework of reticular connective tissue
• -houses and provides a proliferation site for lymphocytes
• -has an ideal surveillance vantage point for lymphocytes and macrophages
• -they occupy the spaces of this tissue to monitor activities before they leave to patrol the blood.

• -Diffuse lymphatic tissue of a few scattered reticular tissue elements found everywhere but specifically in the mucous membranes and in lymphoid organs
• -lymphoid follicles (nodules) contain tightly packed reticular tissue called germinal centers. they form larger lymphoid organs like lymph nodes but are also found alone in the peyer's patches of the intestinal wall and in the appendix

b cells proliferate here when they produce plasma cells

• -main lymphoid organ
• -hundereds cluster along the lymphatic vessels of the body,
• -protecting the trunk of the body and concentrated along the right and left cervical nodes (neck), axillary nodes(armpit),and inguinal nodes (groin) where lymphatic vessels merge into trunks

• -filter lymph before it heads back to bloodstream: macrophages in the nodes remove debris and pathogens
• -help activate the immune system: if lymphocytes see antigens here, an immune response is activated

• - small (~1 inch length), bean-shaped (hilus = indentation)
• - surrounded by dense, fibrous capsule with extensions, trabeculae, that compartmentalize node interior
• - cortex (outer region) with areas of densely packed cells (follicles/germinal centers) + medulla (inner region)
• -Dendritic cells cover follicles and house Tcells
• -contain medullary cords: thin inward exenstion of cortical lymphoid tissue in nodes that contain both lymphocytes and plasma cells
• -and lymph sinuses: large capillaries crisscrossed with reticular fibers where numerous macrophages reside

• - lymph enters convex surface of node via afferent lymphatic vessels
• -then through the various subcapsular sinus
• - and exits concave (hilus) surface via efferent lymphatic vessels (valves prevent back-flow)
• -more afferent vessels than efferent to stagnate the flow in order to filter the lymph.

cancer of lymphoid tissue

• -when they are infected, buboes, by microorganisms. become tender to touch
• -cancer cells can become trapped there and infiltrate they nodes. swollen but not tender to touch

• -largest lymphoid organ, rich in blood (houses great number of leukocytes and erythrocytes)
• -located on left side of abdomen, just below diaphragm, curling around stomach
• -splenic artery and vein enter/exit spleen from concave (hilus) side

• -provides site for lymphocyte proliferation and immune surveillance and response
• -blood cleansing and filtering functions: old or defective RBC's and platelets phagocytized (RBC graveyard), removes debris, pathogens, and toxins from blood
• -salvages iron for making new hemoglobin
• -stores blood platelets
• -site of erythrocyte production in fetus

fibrous capsule thathas traveculae that extend inward like nodes which contain both lymphocytes and macrophages and erythrocytes

(high density of lymphocytes) functions primarily in immunity

• -RBC and blood borne pathogen disposal
• -sites of venous sinuses

because it's capsule is thing and can be injured by direct abdominal blow or infection causing it to rupture spilling blood in peritoneal cavity

• - rupture requires immediate splenectomy to avoid internal hemorrhage and hypovolemic shock
• - liver and bone marrow compensate for loss or it can regenerate from small part left intact in children

• -located in mediastinum posterior to sternum and anterior to aortic arch
• - or inferior to neck and extends into superior thorax
• - important in childhood, from puberty on it gradually atrophies becoming fibrous and fatty
• -like cauliflower, thymus composed of many lobules, each with outer cortex and inner medulla
• -composed not of reticular connective tissue but of specialized epithelial cells called thymocytes
• -only t-cells here, especially in cortex, no b-cells. and some macrophages

-secretes hormones which cause T cells (T for thymus) to mature and become immunocompetent (T cells produced in bone marrow, mature in thymus, and go to lymph nodes)

they are specialized epithelial cells that make up the thymus

-involved in the development of regulatory T-cells

- found in ring around entrance to pharynx, appear as swellings of mucosa:

• 1) palatine tonsils (largest) - at posterior of oral cavity- upper posterior part of throat, most often infected
• 2) pharyngeal tonsils (adenoids) on posterior wall of nasopharynx - up by the ear
• 3) lingual tonsil at base of tongue
• 4) tubal tonsils at openings of auditory tubes into pharynx

• -gather and remove pathogens in inhaled air or ingested material
• - many infoldings, or crypts, which trap bacteria
• - lymphocytes initiate response

• -deep crevices in tonsil's epithelium cells that invite bacteria and pathogens to get trapped, work their way into lymphoid tissue and then get destroyed
• -strategy to produce a wide variety of immune cells that have a memory for the trapped pathogens

• -removed (tonsillectomy) if severely infected (tonsillitis)
• - "T&A"= tonsillectomy and adenoidectomy

• - includes tonsils, Peyer's patches, and appendix and lymphoid follicles in the bronchi
• - protects body from invaders entering digestive and respiratory tracts

• -large clusters of lymphoid follicles located in the wall of the distal oration of the small intestine (ileum)
• -also found in the appendix
• -function like tonsils
• -destroy bacteria before they breach intestinal wall and create memory lymphocytes

• -begins with vessels and then clusters of nodes which arise from lymph sacs forming on veins
• -the thymus is the first lymphoid organ to appear, grows from lining of pharynx

• -first line of defense = external body membranes (skin + mucous membranes) prevent entry of microbes
• - second line of defense = phagocytes, antimicrobrial proteins and other cells to inhibit spread of pathogen. hallmark is of inflammation called into action if first line penetrated.

• - third line of defense
• - works against particular invaders
• - functional, rather than anatomical, system many organs (particularly of the lymphatic system) involved in processes
• - composed of trillions of immune cells (lymphocytes) found throughout body, and other substances

• - cover outside of body and line all cavities open to exterior (digestive, respiratory, urinary, and reproductive tracts)
• - closely packed, often heavily keratinized epithelial cells form barrier to pathogens and harmful substances
• - outer cells of stratified squamous epithelium in skin are dead (viruses can't use) and continually desquamate (pathogens must swim against current)
• - protective secretions

• - sweat and sebum are acidic and bactericidal
• - stomach acid kills pathogens (taking medications to reduce stomach acid increases chance of food poisoning)
• - saliva and lacrimal fluid (tears) contain lysozyme (enzyme that kills bacteria)
• - mucus traps microbes and other particles (often combined with ciliated cells that sweep along mucus + trapped material)
• - urine is acidic, flushes out tract

• -phagocytes arrive on the scene
• -different types are neutrophils, eoisinophils and macrophages
• - Natural killer cells involved
• -inflammation and involved
• -antimicrobial proteins involved

• - most common and abundant leukocyte and first to respond to infection
• - granulocytes with nuclei of 3-5 lobes
• - phagocytize pathogens and release bleach
• - elevated neutrophil count suggests acute bacterial infection, such as appendicitis
• -produce defensins that pierce pathogens membrane

• - less common leukocyte
• - granulocyte with nuclei of 2 lobes
• - somewhat phagocytic, more important in combating parasitic worms by release of noxious compounds

• - called monocytes until leave the bloodstream for interstitial spaces
• - big, agranular leukocytes that respond later to infection
• - wander throughout tissues phagocytizing pathogens and debris (garbage collecting)
• - elevated monocyte count suggests chronic bacterial infection, such as tuberculosis
• -can be fixed to the liver or brain for example or roam freely like those in the lungs

• -phagocytes engulf debris after first lassoing it with it's cytoplasmic extensions
• -need to be able to adhere to it before ingesting it with lysosomal enzymes
• -if called upon by helper t-cells then additional free radicals are at their disposal to kill the foreign particle: called respiratory burst

when complement proteins or antibodies coat foreign particles making it easier for phagocytes to adhere to and ingest them

• - large, granular lymphocytes
• - indiscriminately attack foreign, virus-infected, or cancer cells by opening holes in cell membrane
• - enhance inflammatory response

• - response to injury (blow, burn, irritating chemicals, infections)
• - inflammation of organ, structure, or tissue designated by ending -itis

• -prevents the spread of damaging agents to nearby tissues
• -disposes of cell debris and pathogens
• -sets the stage for repair

4 signs: redness, swelling, pain, heat

• 1) release of inflammatory mediators by damaged tissue and leukocytes:
• - histamine (anti-histamines reduce inflammation)
• - prostaglandins (aspirin + other analgesics counteract)
• - others
• 2) mediators cause vasodilation and consequent local accumulation of blood (including antibodies, leukocytes, and clotting factors) causes redness and heat
• 3) mediators also increase permeability of capillaries fluid containing antibodies and clotting factors flows into tissue spaces and causes swelling, or edema (pressure on nerves, as well as bacterial toxins, result in pain) also dilutes toxins, brings in O2 and nutrients, and initiates clotting
• 4) mediators attract phagocytic leukocytes (neutrophils and macrophages) by
• chemotaxis