Digestive System Flashcards
What does food become during the course of digestion?
Food->bolus->chyme
What is the basic structure of the gut wall?
Mucosa- epithelium, lamina propria, muscularis mucosae
Submucosa (ct with nerves, blood and glands)
Muscularis externa (smooth muscle)
Serosa membrane
What are the functions of the GI tract? (8)
Provide port of entry for food Mechanical disrupt food Temporarily store food Chemically digest food Kill pathogens in food Move food along tract Absorb nutrient from food Eliminate residual waste material
What does the mouth do? (3)
Produces saliva
Chemical digestion
Physical disruption
What is the structure of the oesophagus?
Mucosa- epithelium, lamina propria, muscularis mucosae
Submucosa (ct with nerves, blood and glands)
Muscularis externa (smooth muscle- perform peristalsis)
Adventitia
What cells make up the epithelium of the oesophagus?
Stratifies squamous non keratinised
How does the stomach physically and chemically disrupt the bolus?
Physical-churning
Chemical- acid and enzymes (eg. HCl + pepsin)
What are the main functions of the stomach? (3)
Storage
Disruption (churning)
Disinfection- acid kills bacteria
What is the mucosal rugae?
Folds of gastric mucosa which creates longitudinal ridges in empty stomach
What is the structure of the stomach?
Gastric mucosa (secrete acid, digestive enzymes and hormones) Submucosa Muscularis externa - 3 layers of smooth muscle (cause physical disruption)
What do the surface mucous cells secrete and why?
Mucus containing HCO3- ions which neutralises the stomach acid and protects the cells
What is the basic structure of a gastric pit?
Pit-mucus secreting cells
Isthmus-stem cells which repopulate the whole gland
Neck
Base
What are 3 cells that you find in gastric pits?
Parietal cells-secrete H+ and HCO3- (which is take in capillaries to surface mucus cells)
Chief cells-secrete pepsinogens=pepsin
Enteroendocrine cells-secrete gastrin - causes acid secretion in other cells
What are the 3 parts of the small intestine?
Duodenum,jejunum, ileum
What glands are found in the duodenum glands?
Brunner’s glands- secrete HCO3- mucus which neutralises chyme
What happens to the chyme as it enters the duodenum?
It is diluted by water (from ECF and bile) and enzymes complete digestion
What does absorption require? (3)
Energy
Good blood supply
Large SA and adequate contact time
What is the basic structure of the jejunum?
Mucosa- epithelium, lamina propria, muscularis mucosae
Submucosa (ct with nerves, blood and glands)
Muscularis externa (smooth muscle)
What is plicae circulares?
The circular projections into the lumen created by the folding of the mucosa and submucosa
What do the mucosa and submucosa create when they folding into circular folds and project into the lumen of the jejunum?
Plicae circulares
By the end of the ileum, what does the chyme consist primarily of?
Water
Name the 5 sections of the large intestine
Caecum, ascending colon, transfers colon, descending colon, sigmoid colon
What is the basic structure of colon?
Mucosa- epithelium (produce mucus and absorb water and electrolytes),lamina propria, muscularis mucosae
Submucosa (ct with nerves, blood and glands)
Muscularis externa (smooth muscle)
What are the numerous folding in the colon called?
Crypts of Lieberkuhn
Why is there so much bacteria in the colon?
It is involved in synthesis of things ie vitamin B12/K
Breaks things down ie primary to secondary bile acids
Converts things ie bilirubin to non-pigmented metabolites
What can a fluid imbalance lead to? (2)
Life threatening dehydration
Life threatening electrolyte imbalance
What 3 ways is the GI tract controlled?
Neural->
Paracrine -> Mechanisms
Endocrine ->
What are the two plexus called that neurally control the autonomic section of the GI tract?
Myenteric plexus (between muscle layers of gut wall) Submucosal plexus (between submucosa and muscularis externa)
What two substances control the GI tract in a paracrine way?
Histamine (controls acid production in stomach) Vasoactive substances (affect blood flow in gut)
What 3 hormones play a role in the GI tract control?
Secretin
CCK
Gastrin
