Lymphatic System Flashcards
Lymphatic system
Vast network of lymphatic vessels
Connected with lymph nodes (masses of lymphatic tissue)
Secondary circulatory system
Collects surplus tissue fluid (lymph)
Includes spleen, bone marrow, thymus, nodes, and vessels
Lymphatic system functions
Drainage of tissue fluid Collection of lymph from tissue spaces Transport of lymph to venous system Absorption and transport of fat Defence mechanism for body to transport antibodies and lymphocytes to fight pathogens
Lymph enters
Right lymphatic duct (right upper body)
Thoracic duct (rest of body)
Lymph re-enters venous circulatory system
Lymphatic vessels in brain
Located in dura mater
Extends the length of superior sagittal and transverse sinuses
Fluid to venous system
Lymphoid organs
Lymph node
Thymus
Spleen
Lymph nodes
Tonsils Dense CT throughout body Functions to filter lymph before reaching venous circulation Usually react first to pathogens Strategically positioned Fixed macrophages
Thymus
Posterior to sternum
Important role in growth and development of immune system
Continues to grow until puberty
Gradually replaced by fat after puberty
Continues to produce T-lymphocytes in adulthood
Spleen
Largest of lymphatic organs
Located in left upper quadrant
Protected by ribs 9-11
Large splenic artery due to large blood volume
Spleen functions
Blood is monitored by T-cells for any pathogens
Macrophages swallow and digest debris in blood
Immune responses
Innate = don’t need previous exposure to pathogen in order to attack it Acquired = learn to recognize a pathogen; mount a larger response on second exposure
Lymphocytes
3 types T-cells (thymus dependant) B-cells (bone marrow) NK cells (natural killer) 80% are T-cells (cytotoxic, helper, suppressor)
Defence mechanisms
Non-specific = does not distinguish between pathogens, fever/skin/phagocytes/inflammation, NK cells/mast cells/basophils/neutrophils/eosinophils/macrophages Specific = depends on activity of lymphocytes (T-cells manufactured for a specific bacteria)
Gastrointestinal (GI) tract
Represents 70% of entire immune system
Gut contains trillions of microorganisms
Development of immune system dependant upon exposure to microorganisms
Lymph in GI tract
Small intestine = 2.5cm in diameter, 3m long, 20-40 villi/sq mm
Gut-associated lymphoid tissue (GALT)
Mesenteric lymph nodes (MLN’s)
Non-specific defences in gut
Epithelial lining
Gut microbiota
Epithelial lining
First line of defence against pathogens
Depends on tight junction proteins (TJP’s) and intact mucosal layers
If compromised it may lead to disease or infection
Gut microbiota
Energy harvest Produce neurotransmitters Break down fibres Bacterial interference (opportunistic/“bad” bacteria can’t colonize) Defend against pathogens Repairs and maintains epithelial lining Maintains health of TJP’s
Factors influencing microbiome
Diet (probiotics/prebiotics) Stress Sickness Infection Mode of delivery (C-section/vaginal) Antibiotic use in pregnancy or early life
Germ free animals
Defects in their spleen and MLN’s
Imbalance of T-cells
Low immune, cellular, humoral activity
Altered metabolism, behaviour, brain development
Germ free studies
Study published in 2015 found that GF mice had disrupted neuroimmune process
Administering short-chain fatty acids (SCFA’s) reversed effects
Fecal microbiota transfer (FMT)
In humans used for C. difficile infections
Bacterial interference (non specific immunity)
Reduces risk of antibiotic resistance
85-90% effective in those who don’t respond to abx
Potential therapeutic benefit for = IBS or IBD, ulcerative colitis, C. difficile infection, and other GI disorders
Process for FMT
50-300g of feces collected from donor
Feces are dissolved in 50-100ml of normal saline
Fecal materials are filtered through a metal strainer
Fecal slurry is administered through colonoscopy
Hippocrates
Father of modern medicine
“All diseases begin in the gut”
“Let food be thy medicine and medicine be thy food”
