Describe the lymphatic collecting vessels/lymphatics?
-have more internal valves
-same 3 tunis as veins (Tunica interna, tunica media, and tunica externa) but thinner walled and anastomose (connect) more
Describe lymphatic trunks?
-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)
Describe lymphatic ducts?
-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
What is cistern chyli?
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)
-main warriors of the immune system arises in red bone marrow
-mature into T-cells and B-cells that protect body against antigens
Function of Tcells?
manage immune response and also destroy infected cells
Function of Bcells?
-produce plasma cells which are clones and secrete antibodies
Function of macrophages?
Function of Dendritic cells?
capture antigen and bring back to lymph nodes
Function of reticular cells?
fibroblast like cells that produce reticular storm which is the network that supports the other cell types
Describe lymphoid tissue?
-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.
What are the different Lymphoid tissue "packages"?
-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
What occurs in germinal centers?
b cells proliferate here when they produce plasma cells
Describe lymph nodes?
-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
Function of lymph nodes?
-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
Structure of lymph nodes?
- 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
How does lymph circulate in the nodes?
- 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.
What is lymphoma?
cancer of lymphoid tissue
What would cause nodes to swell?
-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
Lymphoid Organ: Describe Spleen?
-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
Functions of the spleen?
-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
What is the spleen surrounded by?
fibrous capsule thathas traveculae that extend inward like nodes which contain both lymphocytes and macrophages and erythrocytes
What is the white pulp of the capsule?
(high density of lymphocytes) functions primarily in immunity
What is in the red pulp of the spleen capsule?
-RBC and blood borne pathogen disposal
-sites of venous sinuses
Why can spleen be easily injured?
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
How is ruptured spleen treated?
- 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
Lymphoid Organ: Describe Thymus?
-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
Function of Thymus?
-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)
What are thymocytes?
they are specialized epithelial cells that make up the thymus
What are thymic (Hassall's) corpuscles?
-involved in the development of regulatory T-cells
Lymphoid Organ: Describe Tonsils?
- found in ring around entrance to pharynx, appear as swellings of mucosa:
Describe the 4 types of tonsils?
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
What are the functions of tonsils?
-gather and remove pathogens in inhaled air or ingested material
- many infoldings, or crypts, which trap bacteria
- lymphocytes initiate response
What are tonsillar crypts?
-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
What is a tonsillectomy?
-removed (tonsillectomy) if severely infected (tonsillitis)
- "T&A"= tonsillectomy and adenoidectomy
What is MALT (mucosa-associated lymphatic tissue):
- includes tonsils, Peyer's patches, and appendix and lymphoid follicles in the bronchi
- protects body from invaders entering digestive and respiratory tracts
Describe Peyer's patches?
-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
How does the lymphatic system develop?
-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
CH 21: Describe Nonspecific (or innate) defense system (or resistance)?
-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.
Describe Specific (or adaptive) defense system (or resistance)?
- 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
Detail about first line of defense: skin and mucosa?
- 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
What are the protective secretions of the skin + mucosa?
- 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
Details about the second line of internal defense: cells and chemicals?
-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
What is phagocytosis?
-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
What does opsonization mean?
when complement proteins or antibodies coat foreign particles making it easier for phagocytes to adhere to and ingest them
Describe Natural Killer Cells?
- large, granular lymphocytes
- indiscriminately attack foreign, virus-infected, or cancer cells by opening holes in cell membrane
- enhance inflammatory response
What does inflammation occur?
- response to injury (blow, burn, irritating chemicals, infections)
- inflammation of organ, structure, or tissue designated by ending -itis
What is the function of inflammation?
-prevents the spread of damaging agents to nearby tissues
-disposes of cell debris and pathogens
-sets the stage for repair
What are the 4 signs of inflammation?
4 signs: redness, swelling, pain, heat
Describe the inflammatory response?
1) release of inflammatory mediators by damaged tissue and leukocytes:
- histamine (anti-histamines reduce inflammation)
- prostaglandins (aspirin + other analgesics counteract)
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