Overview of Digestive System Flashcards
Function of GI tract
Flow process
The GI tract adds water, ions, enzymes to a food/meal to create an aqueous solution of molecules suitable for absorption and transport round the body
- Ingestion
- Secretion
3.Digestion (mechanical & Chemical)
4.Absorption
5.Integration with metabolism - Elimination
Main structures and areas of of the GI
Foregut:
Oesophagus
Stomach
Liver
Gallbladder
Pancreas
1/2 Duodenum
Mid gut:
1/2 Duodenum
Jejenum
Ileum
Ascending colon
2/3 transverse colon
Hind gut:
1/3 transverse colon
Descending colon
Rectum
Anal Canal
Gut/Epithelial barrier (to bacteria) methods
- Physical
o Tight junctions
o mucus - Immune
o IgA(antibody)
o Intraepithelial lymphocytes
oMacrophages, dendritic cells
oPaneth cells release defensins
o M cells
o Peyer’s patch
o Lymph nodes
o Innate immune receptors - Others
o Hormones e.g.prostaglandins
o Cells that secrete anti bacterial `enzymes
Role of gastric acid (absence of acid called achlorhydria)
- Sterilize food
- Initial digestion
- Only bacteria known to survive in stomach is Helicobacter pylori.
Eneteric Nervous system:
Enteric-enteric connections in small/large bowel
- Sensory neurons
- Examples of this - Motor neurons
o Oesophagus: chemoreceptors
o Stomach- release of 5HT
o Duodenum- CCK–safety/fullness
o Jejunum -mechanoreceptors “stretch”
Motor Neurons:
– Entire GI tract:
control motility
Regulation of food intake - appetite and safety -…
Regulation of digestion meal requires ..
Regulation of food intake - appetite and safety - ghrelin, CCK, leptin
Regulation of digestion meal requires GI hormones, neural control
Hormone, Source and target tissue/action
Gastrin
Secretin
Cholecystokinin (CCK)
Ghrelin
Motilin
Glucagon-like peptide-1 (GLP-1)
Gastric inhibitory peptide (GIP) Somatostatin
Gastrin
Stomach (G cells)
- Stimulates gastric acid secretion and gastric motility
Secretin
Duodenum (S cells)
-Stimulaes pancreatic bicarbonate secretion
Cholecystokinin (CCK)
Duodenum (I cells)
- Stimulate pancreatic enxyme secretion and gallbladder contraction
Grehlin
Stomach (P/D1) cells
- Stimulates hunger and gastric acid secretion
Motilin
Duodenum and jejunum (M cells)
-Stimulates gastrointestinal motility during fasting
Glucagon like peptide 1 (GLP1)
Intestines (L cells)
- Stimulates insulin secretion, inhibits glucagon secretion, slows gastric emptying, and promotes satiety
Gastric inhibitory peptide (GIP)
Duodenum and jejunum (K cells)
-Stimulates insulin secretion in response to food intake
Somatostatin
- Pancreas (δ cells)
- Inhibits release of various hormones including insulin, glucagon, gastrin, and growth hormone
Central role of liver
o Detoxification role
o Central role in metabolism
o Lipid metabolism; glucose homeostasis
Central role of pancreas
o Endocrine function–Insulin,glucagon
o Exocrine function–digestive enzymes
o Bicarbonate production
Examples of bacteria in gut and their positive role
Firmicutes:
Inhib of production of pro inflam cytokines
Proteobacteria ( e coli)
Bacteriocin production
protect against pathogen colonisation
Actinobacteria
Improve inestianl barrier function
inhibts inflamm
Bacteriodetes
- Nutrient absorption
-Manturation and maintainenec of epithelial cells
draw the enteric nervous system diagram
Lecture Slide
Gut brain axis
Brain influence on gut:
Motility, secretion, nutrient delievery, Micorbail balance
Gut on brain:
Neurotransmitters
Stress/anxiety
mood
behaviour
Visceral hypersensitivity
– Lower threshold of stimulation to produce pain
Hypervigilance
– Heightened awareness of symptoms
Emotional State
What happens when we eat?
- regulation of digestion (draw diagram )
Grehlin INCREASE appetite
Leptin DECREASE apaetite
CCK and secretin - inhibit
everything else +
