Lymphatic System

Question 1

Lymphatic system

Answer 1

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

Question 2

Lymphatic system functions

Answer 2

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

Question 3

Lymph enters

Answer 3

Right lymphatic duct (right upper body)
Thoracic duct (rest of body)
Lymph re-enters venous circulatory system

Question 4

Lymphatic vessels in brain

Answer 4

Located in dura mater
Extends the length of superior sagittal and transverse sinuses
Fluid to venous system

Question 5

Lymphoid organs

Answer 5

Lymph node
Thymus
Spleen

Question 6

Lymph nodes

Answer 6

Tonsils
Dense CT throughout body 
Functions to filter lymph before reaching venous circulation 
Usually react first to pathogens 
Strategically positioned 
Fixed macrophages

Question 7

Thymus

Answer 7

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

Question 8

Spleen

Answer 8

Largest of lymphatic organs
Located in left upper quadrant
Protected by ribs 9-11
Large splenic artery due to large blood volume

Question 9

Spleen functions

Answer 9

Blood is monitored by T-cells for any pathogens

Macrophages swallow and digest debris in blood

Question 10

Immune responses

Answer 10

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

Question 11

Lymphocytes

Answer 11

3 types 
T-cells (thymus dependant)
B-cells (bone marrow)
NK cells (natural killer) 
80% are T-cells (cytotoxic, helper, suppressor)

Question 12

Defence mechanisms

Answer 12

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)

Question 13

Gastrointestinal (GI) tract

Answer 13

Represents 70% of entire immune system
Gut contains trillions of microorganisms
Development of immune system dependant upon exposure to microorganisms

Question 14

Lymph in GI tract

Answer 14

Small intestine = 2.5cm in diameter, 3m long, 20-40 villi/sq mm
Gut-associated lymphoid tissue (GALT)
Mesenteric lymph nodes (MLN’s)

Question 15

Non-specific defences in gut

Answer 15

Epithelial lining

Gut microbiota

Question 16

Epithelial lining

Answer 16

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

Question 17

Gut microbiota

Answer 17

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

Question 18

Factors influencing microbiome

Answer 18

Diet (probiotics/prebiotics)
Stress
Sickness
Infection 
Mode of delivery (C-section/vaginal)
Antibiotic use in pregnancy or early life

Question 19

Germ free animals

Answer 19

Defects in their spleen and MLN’s
Imbalance of T-cells
Low immune, cellular, humoral activity
Altered metabolism, behaviour, brain development

Question 20

Germ free studies

Answer 20

Study published in 2015 found that GF mice had disrupted neuroimmune process
Administering short-chain fatty acids (SCFA’s) reversed effects

Question 21

Fecal microbiota transfer (FMT)

Answer 21

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

Question 22

Process for FMT

Answer 22

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

Question 23

Hippocrates

Answer 23

Father of modern medicine
“All diseases begin in the gut”
“Let food be thy medicine and medicine be thy food”