GI7 Immune function &GI tract

Question 1

Several lines of defence:

Answer 1

• Taste and mouth feel ( that yacky chicken you spat out)
• Vomiting (that time you had food posiening at center parks)
• Gastric acid (very low pH in stomach GCSE)
• Hydrolytic enzymes
• Mucosal epithelial barrier (they stick together nothing can squeeze past)
• Gut-associated lymphoid tissue (GALT)- several types of lymphoid tissue that store immune cells such as T lymphocytes and B lymphocytes in the intestine.
• Intestinal bacteria- symbiotic relationship, in competition with pathogens

Question 2

1) What controls vomiting?

2) Describe vomiting from stimulus to response

Answer 2

1) emetic centre in the brain
2)  initiated by the chemoreceptor (detects something is not right)
 CNS (parasympathetic and sympathetic)
 Increase in HR and sweating- sympathetic NS
 Increased salivation (Parasympathetic NS; sight, smell and anticipation)
 Retroperistalsis (reverse peristalsis) starting from the middle of the SI (PNS)
 A lowering of intrathoracic pressure and an increase in abdominal pressure (abdominal muscles contract) propels stomach contents into the oesophagus

Question 3

____a_____ prevent proteins or glycolipids from entering by any way other than through the membrane. It keeps extracellular fluids surrounding apical and basolateral membranes ___b____

Answer 3

a) Tight junctions

b) seperate

Question 4

Gut Associated Lymphoid Tissue (GALT)
Protects against __1____ entering body across intestinal mucosal barrier
A component of _____2____ that sits bellow ___3____ cells. Consists of dispersed aggregates of ___4____ tissue including collections of lymph nodes e.g. in:
 Tonsils
 Appendix
5) Something in small intestine

Answer 4

1) antigens
2) MALT (Mucosa-Associated Lymphoid Tissue)
Lymphoid tissue
3) epithelial
4) lymphoid
5)Peyer’s patches

Question 5

Peyer’s patches
 Bump of lymphoid tissue in mucosa of ____1____
 Store ___2_____found in Peyer’s patches

Answer 5

1) GI tract

2) macrophages, DC, B & T lymphocytes

Question 6

What are M cells?

2) function?
3) What is on apical surface?

Answer 6

1) Specialised epithelial cells that overlie peyer’s patches
2) Provide information about the contents of lumen to immune cells of the GALTm preparing the GALT tissue.
3) clathrin-coated pits with embedded receptors

Question 7

How do M cells initiate immune responses?

Answer 7

1) Trancytosis and transport the pathogen to basolateral membrane
2) Released to interstitial fluid-macrophages, lymphocytes and cytokines
3) trigger inflammatory response
4) increase Cl- (possible to upset pathogen membrane potential), fluid and mucus

Question 8

1) Why do some molecules cause food poisoning?
2) what causes the diarrhoea and vomiting?
3) name 2 food poisoning bacteria:

Answer 8

1) evolved surface molecules that bind to M cell receptors.
M cells transport the bacteria across the epithelial barrier to inside body. They think they are transporting antigens.
2) the immune systems response
3)salmonella, shigella

Question 9

1) how does the large &small intestine allow the growth of intestinal bacteria?
2) Why do we want intestinal bacteria?

Answer 9

1) pH is neutral

2) They produce Biotin (B vitamins) and vitamin K, as well as intestinal flora, and antimicrobrial polypeptides

Question 10

What antimicrobial polypeptides do intestinal bacteria produce? + their benefit

Answer 10

 Lysozymes –effective against gram + species (streptococci)
 Lactoferrin –antiviral properties
 Defensins –antiviral properties