Gastrointestinal System Flashcards
Ingestion
The intake of food into the GI tract via the mouth
Mechanical Processing
Physical breakdown of food by the teeth, stomach and intestines
Increases the surface area of food, allowing enzymes to work more efficiently
Chemical Processing
Breakdown of complex molecules (polymers) into monomers using enzymes and other substances
Secretion and Absorption and Egestion
Secretion: release of water, acid, enzymes, buffers and salts which aid in chemical digestion and absorption
Absorption: uptake of useful molecules across the epithelium of the GI tract and into interstitial fluid
Egestion: removal of waste products
Breaking down of polymers
we cannot absorb polymers such as proteins, lipids and carbohydrates so they must be broken down by chemical and physical digestion
Proteins are broken down into amino acids
Lipids are broken down into fatty acids and glycerol
Carbohydrates are broken down into monosaccharides
What is someone lacking if they are lactose intolerant
lactase enzyme
Layers of the GI tract wall
Serous: fibrous connective tissue - structure and support
Muscularis: two layers of smooth muscle. Antagonist pair. Lognitudinal muscle (down GI tract) and circular (around circumference of GI tract). creates peristalsis
Submucosa: connective tissue layer which contains blood vessels, lymph vessels and nerves
Mucosa: inner lining, cells get replaced every 5-7 days
Lumen
Chemical and Physical processing in the mouth
Chemical: amylase breaks down starch into maltose, saliva makes food softer and helps form a bolus. Taste sensation increases to prepare the rest of the digestive system = stimulation of gastric juices
Mechanical: teeth. Food is broken down into smaller pieces creating a larger surface area for enzymes to act on. helps mix food with saliva
Voluntary phase of swallowing (deglutition)
tongue pushes bolus into the pharynx whilst oesophagus is kept closed. Bolus travels down the oesophagus via peristalsis
Involuntary phase of swallowing (deglutition)
soft palate rises to close the passage to the nasal cavity and the epiglottis decompresses over the trachea
How does peristalsis occur?
circular muscle contracts behind bolus and longitudinal muscle contracts in front of bolus
Where are these 4 sphincters
Oesophageal
Pyloric
ileo-caecal
Odi
oesophageal = Between the oesophagus and cardia part of the stomach
pyloric = connects the stomach to the duodenum
ileo-caecal = small intestine to caecum
Odi = bile duct
What is food mixed with in the stomach?
hydrochloric acid and gastric juices to create chyme
How many muscle types in the stomach & name them
3
circular, longitudinal and oblique
4 parts of the stomach
cardia, fundus, body and pylorus
Functions of the stomach
storage area
mechanical and physical processing
Protective - hydrochloric acid kills bacteria
Mechanical and chemical processing in the stomach
Mechanical: 3 layers of muscle. stomach folded into rugae to expand as it fills
Chemical: gastric juices (hydrochloric acid, lipases, intrinsic factor and mucus
What is intrinsic factor?
helps with the absorption of vitamin B12
Vitamin B12 is a water soluble vitamin with an important role in the functioning of the brain, nervous system and blood
What would happen if insulin was taken as a tablet?
Would have less of an affect because it would get broken down in the stomach by pepsin since it is a hormone and hormones are proteins
What reflex regulates stomach emptying?
Enterogastric reflex
Why does chyme need to be neutralised in the small intestine?
because the stomach has a pH of 2 and the small intestine has a pH of 7-8
What are the 3 parts of the small intestine
Duodenum, jejunum and ileum
Mechanical and chemical processing in the small intestine
Mechanical: peristalsis, segmentation
Chemical: microvilli secrete enzymes such as maltase, sucrase and peptidases. Other secretions from accessory organs also help break down complex molecules
Villi and Microvilli
on the walls of the small intestine - majority of nutrients are absorbed
Create a larger surface area for absorption
highly vascular to maintain a diffusion gradient