Unit 4 Lecture 27 Flashcards
What is the importance of the small intestine?
site of most digestion and absorption
What are the 3 sections of the small intestine?
duodenum, jejunum and ileum
What is the sphincter in the small intestine?
ileocecal sphincter
What is found on the mucosa layer of the small intestine that increases surface area for digestion and absorption??
- circular folds
- villi
- microvilli
What are the cells found in the small intestine and what do they secrete?
- absorptive cells - absorb nutrients
- goblet cells - secrete mucous
- enteroendocrine cells (S, CCK and K) - S secretes secretin, CCK secretes cholesystokinin, K secretes GIP
- Paneth cells - secretes lysozomes and can do phagocytosis
What is found on the surface of microvilli?
brush border enzymes
What do brush border enzymes do?
chemically breakdown of carbohydrates, proteins and nucleosides
What is found in the lumen of the small intestine?
pancreatic juices and chyme
What is chyme made of?
amylase, proteases, lipase and nucleases
Label the complete flow of bile
- hepatocytes in liver
- starts with a C
- bile duct
- right and left hepatic duct
- common hepatic duct
- common bile duct and pancreatic duct
- hepatopancreatic ampulla
- duodenum
Where does the liver, gallbladder and pancreas empty into?
duodenum of small intestine
What are the main categories of enzyme secreted by the pancreas?
- Amylase
- Proteases
- Lipase
- Nucleases
What amylase enzyme is secreted by the pancreas?
pancreatic amylase
What protease enzymes are secreted by the pancreas?
- Trypsin
- chymotrypsin
- carboxypeptidase
- elastase
What lipase enzyme is secreted by the pancreas?
pancreatic lipase
What nucleases enzymes are secreted by the pancreas?
ribonuclease and deocyribonuclease
What are proteases?
Secreted as inactive precursors (like pepsinogen in the stomach)
What activates trypsinogen to trypsin?
Enteropeptidase (on brush border cells)
What does trypsin activate?
Activates chymotrypsinogen, procarboxypeptidase and proelasease
Where are carbohydrates digested?
- Mouth
- Stomach
- Pancreas
- Small intestine
What digests carbohydrates in the mouth?
Salivary amylase
How are carbohydrates digested in the stomach?
Mechanical digestion (no chemical digestion)
What digests carbohydrates in the small intestine?
Brush border enzymes Maltase, Sucrase, and lactase
What do the brush border enzymes in the small intestine act on?
disaccharides (maltose, sucrose, and lactose)
What do the brush border enzymes in the small intestine produce?
monosaccharides (fructose, glucose and galactose)
What does sucrase produce?
glucose and fructose
What does lactase produce?
glucose and galactose
What does maltase produce?
glucose and glucose
Where are the monosaccharides absorbed into?
epithelial cells
How do glucose and galactose enter epithelial cells?
secondary active transport
How does fuctose enter epithelial cells?
facilitated diffusion
Where do the monosaccharides go when the leave epithelial cells?
bloodstream
How do all monosaccharides leave epithalial cells?
facilitated diffusion
Where are proteins digested in the body?
- Mouth
- Stomach
- Pancreas
- Small intestine
How are proteins digested in the mouth?
mechanical digestion ONLY
What chemicals digest proteins in the stomach?
HCl and pepsin
What enzymes digest proteins in the pancreas?
Pancreatic enzymes (proteases) in pancreatic juices
What enzymes digest proteins in the small intestine?
Brush border enzymes (aminopeptidase and dipeptidase)
Where are amino acids and dipeptides absorbed?
epithelial cells od duodenum and jejunum
How are amino acids and dipeptides absorbed into epithelial cells?
facilitated diffusion
Where are lipids digested?
- BEGINS in mouth
- stomach
- pancreas
- liver
What enzymes digest lipids in the mouth
lingual lipase in saliva
What enzymes digest lipids in the stomach?
gastric lipase
What enzymes digest lipids in the pancreas?
pancreatic lipase in pancreatic juice
What do pancreatic juices do in the stomach?
split triglycerides into fatty acids and monoglycerides
What digests lipids in the liver?
bile
Are lipids digested in the small intestine?
no
What are the two types of lipids?
short chain and long chain lipids
How are short chain lipids (fatty acids) absorbed?
simple diffusion
How are long chain lipids (fatty acids) and monoglycerides absorbed?
simple diffusion through cells
- bile salts are reabsorbed and later recycled (into bile) by liver
- fat-soluble vitamins (A,K,D3, E) enter cells with lipids
