Lecture 15: Digestive system one Flashcards
what does GI stand for?
Gastrointestinal tract
How long is the GI tract?
Hollow tube that is 30 feet long
what is the Gi tract composed of?
mouth pharynx oesophagus stomach small intestines large intestines(colon) anus
what are the accessory organs to the GI tract?
teeth, tongue, salivary glands, liver, gallbladder, pancreas
what are the 3 main functions of the GI tract?
transportation, digestion, and absorption of food
what are the 6 main processes of the digestive system?
ingestion propulsion (motility) mechanical digestion chemical digestion absorption defecation
what is ingestion and where does it happen?
intake of food done by the mouth
what is population where does it take place?
moving food along the digestion tract, involves the entire tract
what plays a role in swallowing?
oropharynx
what is mechanical digestion and which parts of the GI tract are involved?
breaking food down to its simplest form, chewing from teeth in the mouth, churning of the stomach, segmentation in the small intestine
what is chemical digestion and which parts of the GI tract are involved?
when enzymes break down food, in the mouth there’s salivary amylase, the liver has bile, also happens in the pancreas and stomach
what happens during absorption?
nutrients absorbed via lymph vessels and blood vessels.
what is Peristalsis?
movement of food going forwards due to the GI tract wall containing muscles which contract.
what is segmentation and where does it usually take place?
The mixing of food via the muscles in the wall of the GI tract alternating contractions between intestinal segments. This takes place in the small intestines.
how many layers does the wall of the GI tract have?
4
what are the layers of the wall of the GI tract called?
mucosa
submucosa
musculares externa
serosa
whats the functions of the mucosa?
secretes muscus, digestive enzymes
immune response
creates folds
what is the mucosa made of?
surface epithelium
lamina propria
Muscularis mucosae
what does the mucosa line?
Lines the lumen, separates GI lumen from internal environment
what does the surface epithelium of the mucosa contain?
Simple columnar epithelium and mucus-secreting goblet cells. Enzyme -secreting cells and Hormone-secreting cells
what does the lamina propria of the mucosa contain?
connective tissue: Small blood vessels and lymphatic vessels; Nerves; Lymphoid tissues: Lymph nodules and Peyer’s patches
what is the Muscularis mucosae?
thin smooth muscle
what is the submucosa?
Thick layer of connective tissue that is dense and has
elasticity
what does the submucosa contain?
large blood vessels
Lymphatic vessels
nerves branching into the mucosa and muscularis mucosae
Submucosal plexus -part of enteric nervous system
what is the Muscularis externa responsible for?
for the motility of GI tract
what are the Two separate layers of smooth muscle that form the Muscularis externa?
Inner layer of circular muscle
Outer layer of longitudinal muscle
what NS is myenteric plexus apart of?
enteric nervous system
what does the myenteric plexus control?
GI tract motility
what is the Outermost Layer of GI wall?
serosa
How many layers does the serosa have?
2
what are the layers of the serosa ?
Inner layer of connective tissue
Outer layer is mesothelium
what is the serosa attached too?
the mesentery
what does the mesentery do?
maintains position of organs in the GI tract but also allows the to move
what’s the function of the serosa?
protective layer
what part of food is chemically broken down so it can be digested?
carbohydrates, lipids and poteins
what are carbohydrates?
polysaccharides
what enzyme breaks down polysaccharides?
amylase
what breaks down disacharides?
maltase
what happens to monosaccharides ?
absorbed by specialised cells in the SI
what are the two types of amylase?
salivary amylase and pancreatic amylase
where is pancreatic amylase used?
small intentine
name 3 types of disaccharides?
lactose, maltose, sucrose
name three monosaccharides?
galactose, glucose and fructose
what breaks down triglycerides?
lipase
what does triglyceride break down into ?
monosaccharides and fatty acids
what produces lipase?
pancreases produces pancreatic lipase
what has to happen before pancreatic lipase can break down the fats?
the fats need to be emulsified by the bile salts from the liver
what enzymes can break down protein into peptides?
pepsin
trypsin
chymotrypsin
what enzymes break peptides down into amino acids?
aminopeptidase and carboxypeptidase
where is pepsin produced and whats its site of action ?
produced and used in the stomach
what are the pancreatic enzymes?
trypsin, chymotrypsin,
carboxypeptidase
what do accessory glands do?
secrete products into the lumen of the GI tract
what do salivary glands, liver and the pancreas secrete?
saliva
bile
pancreatic juice
what are the three salivary glands?
parotid gland
sublingual gland
submandibular gland
what is saliva comprised of?
99.5% water and 0.5% solutes
what enzymes are in saliva?
salivary a amylase
salivary lipase
lysozyme
what components are in saliva?
sodium, potassium chloride phosphate bicarbonate and mucus
whats it called when you have low production of saliva?
Xerostomia
what are the key components of bile?
bile salts, bile pigments, cholesterol
what is bile secreted from?
hepatocytes
what synthesize bile?
liver
where is bile stored?
gallbladder
what does the common bile duct do?
transports bile from liver/gallbladder to the duodenum
what is the ampulla of vatar?
when the common bile duct joins the pancreatic duct
what does the sphincter of oddi do?
regulates flow from the pancreas and gallbladder to the duodenum
what do exocrine glands of the pancreas produce?
pancreatic juice
what is the endocrine portion of the pancreas known as and what des it do?
Islets of Langerhans
secretes hormones
what does pancreatic juice neutralise?
neutralisesacidic chyme as it enters the duodenum
what enzymes does pancreatic juice contain ?
pancreatic amylase
pancreatic lipase
proteases:trypsin chymotrypsin, carboxypeptidase
nucleases
what does the pancreatic acinar cell do?
synthesizes, stores, and secretes digestive enzymes.
what are zymogens?
Inactive forms of digestive enzymes
when and how do zymogen become active?
in the lumen of the intestinal tract by proteolytic enzymes
what are two types of zymogens?
trypsinogen and chymotrypsinogen
what’s the structure of the liver composed of?
hepatic duct and cystic duct
