4.1 Digestive System part 2 (Submucosal secretions) Flashcards
Submucosal secretions into the GI tract are from the…
Glandular epithelium in (salivary glands, stomach, pancreas, liver, small intestine, large intestine…)
Are the glands that produce submucosal secretions considered exocrine or endocrine glands?
Exocrine
What two types of saliva do the salivary glands produce?
Serous and mucous
Serous saliva
Solubilizes food
Mucous saliva
Lubricates passage of food
What counteracts acidic foods? (Salivary gland secretions)
Buffers (sodium bicarbonate)
Salivary amylase
Initiates carbohydrate digestion by chemical digestion of food
-Breaks starch into disaccharides
4 layers of stomach lining
Mucosa
Submucosa
Muscularis
Serosa
Mucousal cells of the gastric pits
Mucous cells
Parietal cells
Chief cells
Endocrine (G) cells
Mucous cells
Secrete mucus on surface and in neck of glands, protect stomach wall from damage by acid and enzymes
Parietal cells
Secrete HCl
Chief cells
Produce pepsinogen enzyme, converted to active pepsin by stomach acidity (works best at pH less than 3)
Endocrine (G) cells
Produce hormones (Gastrin, histamine)
What enzyme takes carbon dioxide and water to make bicarbonate?
Carbonic anyhydrase
Net effect of HCl production by parietal cells
Stomach pH drops
Blood pH rises
Is the H+ going into the stomach active or passive transport?
Active
Is the HCO3 going into the blood active or passive transport?
Passive
Cells make up ____ but they themselves have _____
Villi, microvilli
Lacteal in small intestine
Lymph tissue, fat absorption
Enterocyte
Often called S cells because they are secreting
Where does the blood go after leaving the small intestine?
The liver! It gets first dibs on the nutrients absorbed from the intestine
What enzymes are bound to the plasma membrane of absorptive epithelial cells of the small intestine?
Disaccharides, peptidases and enteropeptidase
Enteropeptidase
Activates inactive pancreatic enzymes by proteolytic cleavage
Absorptive epithelial cells absorb chemically digested foodstuff, entry point for….
Glucose, amino acids, lipids…
Goblet cells in small intestine
In duodenal glands, secrete mucus
Enteroendocrine cells
Secrete hormones (Secretin, CCK)
Paneth cells
Activate pancreatic proteases, phagocytize larger food borne materials
Exocrine pancreas: Islet or Acinar cells?
Acinar
Which cells lead to pancreatic cancer?
Acinar cells, can digest the tissue around them
Acinar cells
Secrete digestive enzymes that target the four main biomolecules
Acinar cells: Protein
Secreate proteases (trypsin and chymotrypsin) secreted as proenzymes
What are the proenzymes secreted by acinar cells activated by?
Other enzymes residing on small intestine brush border
Acinar cells: Carbohydrates
Pancreatic amylase: digests starch
Acinar cells: Lipids
Pancreatic lipase: Digests lipids (triglycerides)
Acinar cells: nucleic acids
Pancreatic nucleases: Digest DNA and RNA
Intercalated duct cells
Aqueous component of pancreatic secretions
NaHCO3- neutralizes HCl in duodenum
Net effect of pancreatic secretions into intestine
Intestine pH rises
Blood pH drops
Hepatic portal vein
Carries deoxygenated, yet nutrient-rich blood from small intestine directly to the liver
Hepatic artery
Carries oxygenated blood from the heart to the liver
Hepatic duct
Carries bile secretions to small intestine
What are the cells actually doing the function in the liver called?
Hepatocytes
Liver functions
Bile Production
Detoxification
Nutrient storage, synthesis, delivery
What does the liver make?
Plasma proteins, albumen, fibrinogen, clotting factors
Function of bile
- Buffers stomach acid (NaHCO3)
- Emulsifies fats (bile salts)
Liver detoxification
- Amine acid metabolism creates ammonia, requires conversion to urea
- Metabolize alcohol, drugs, foreign food molecules
What does the liver do with vitamins and minerals?
Takes them in
What does the liver do with cholesterol?
Lipoproteins for lipid transport to tissues
What is the major secretion of the large intestine?
Mucus by goblet cells
What is the main role of the large intestine?
Reabsorption of salts and water
-Epithelial cells reabsorb salts, water follows by osmosis
Colorectal cancer
How deadly?
Precancerous…
Starts where?
Second deadliest
- Precancerous Polyps
- Starts in crypts
