The Digestive System Flashcards
What is the first stage involved in the digestive system?
Preparatory stage
What is the alimentary canal
Elongated tub extending from mouth to anus
The role of the mouth
Mechanical digestion with salivary amylase produced by salivary glands
Breakdown of starch into disaccharide molecules
What are the two phases in the preparatory stage?
Involuntary
Voluntary
Involuntary phase
The tongue rises against the palette and closes the nasopharynx
Voluntary phase
Swallowing occurs and the tongue moves to the hard palette pushing the food into orophynx
Peristalsis
Muscles wave like contraction moves food into different parts of digestive region
Occurs in the alimentary canal
Structure of alimentary canal
Contracting inner circular muscle sheet
Relaxing longitudinal muscle that pushes bolts in front of alimentary canal
What is the role of the oesophagus?
Transports bolus to the stomach in the abdomen
Role of the stomach
Stomach wall churns
Structure of the stomach
Two- layer coat & external muscular
Wall of the stomach made of columnar
Epithelial lining contains goblet cells: produces mucus that protects stomach lining from acid erosion
Role of gastric glands
- Produces gastric juice : contains gastric protease
- Parietal cells release HCl: denatures proteins
denatures pepsinogen to pepsin
production of gastric intrinsic factors
What is Gastric intrinsic factor
A glycoprotein produced by parietal cells
Stages of gastric intrinsic factor
- Protein acts as a buffer
- Increase of pH
- Gastrij cells altered
- HCl is too strong in the stomach + increased pepsinogen
- Protein digestion= increase in amino acids
- pH falls
What affects HCl production
Histamine
Role of histamine
Secreted by Enterochromaffin
Cimetidine & Ranitidine
H2 receptor that inhibits stomach acid production
What happens when food enters the stomach
Chyme emptied into the duodenum via pyloric sphincter
What happens during peristalsis
Pyloric sphincter opens and allows some chyme to pass into duodenum
chyme mixed with juices and moves towards large intestine
Role of duodenum
Protein digestion: Trypsin+ chymotrypsin broken down to small polypeptide and peptides
Synthesis and store fats: lipogenesis
Structure of duodenum
Duodenal wall contains success entericus
3 phases of gastric secretion
- Cephalic phase
- Gastric phase
- Intestinal phase
Intestinal phase
Enterogastric reflex: gastric motility inhibited by release of hormones such as secretin& CCK
Closes pyloric sphincter= blocks additional chyme entering duodenum
Duodenum: reduces rate of stomach emptying to small intestine
Function of liver
Produces bile which is manufactured by hepatocytes
Bile is temporarily stored in gallbladder
Role of pancreas
Releases digestive juices
Function of gallbladder
Stores bile needed for the digestion of fats in food
Function of bile
Contains bile salts, cholesterol, water and electrolytes
Structure of liver
Connected to portal vain: brings in nutrient rich blood from digestive system
Hepatic artery: carries oxygenates blood from heart
Digestion of disaccharides
Small intestinal brush border enzymes such as sucrase-isomaltase
Digestion of polysaccharides
In the mouth by salivary amylase
Digestion of fats
Small intestine by pancreatic lipase
Digestion of proteins
Stomach by pepsin and chymotrypsin secreted by the pancreas
What is the biliary tree
System of vessels that direct secretions from liver, gallbladder and pancreas into the duodenum
