function of digestive system: break down carbohydrates, lipids, and proteins (polymers) into small...
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Function of Digestive System:
Break down carbohydrates, lipids, and proteins (polymers) into small molecules. Allows absorption of nutrients (ions and molecules) into bloodstream.
Mouth
Mechanical digestion: teeth!
Chemical digestion: saliva
• amylase (salivary glands)
• mucin (mucins + H2O = mucous)
Saliva also regulates pH in mouth.
pH: 7.0
Stomach• Mechanical & chemical: reduce food to
uniform consistency and osmolarity.• Gastric juice = HCl (parietal cells) + pepsin
(chief cells)• Mucus (goblet cells) protects stomach from
HCl
pH: 2.0
Small intestineFunctions:
• Digestion of lipids and carbohydrates• Protein processing• Absorption of nutrients and water.
pH: 7.8
• Starts in oral cavity with salivary amylase (ptyalin).
• Continues in small intestine with pancreatic amylases.
• Polysaccharides / disaccharides >> monosaccharides.
• Types of carbs?Plants >> starch, celluloseAnimals >> glycogen
Carbohydrate digestion
• Starts in stomach:– Chief cells secrete pepsinogen– Pepsinogen + HCl = pepsin– Proteins denatured by HCl; broken down by pepsin
• Then small intestine:– digested by trypsin and other pancreatic enzymes
• Proteins >> peptide chains >> amino acids
Protein digestion
Lipid digestionSmall intestine:
– bile salts from gall bladder emulsify lipids.– pancreatic lipase digests smaller droplets.
– NaHCO3 from pancreas increases pH.
Lipids >> glycerol, fatty acids, & glycerides.
Hormones
Molecules (e.g. peptide or steroid) produced in one part of an organism that trigger a specific cellular reaction in target tissues.
Exocrine glands: secrete enzymes that are transported through ducts. (e.g. sweat glands, salivary glands)
Endocrine glands: secrete hormones into circulatory system (no ducts). (e.g. pituitary gland, adrenal gland)
Pancreas: “mixed” glandExocrine products: • sodium bicarbonate (NaHCO3)• digestive enzymes (acinar cells)
– lipase – lipids– trypsin – proteins– amylase – starches
Pancreas: “Islets of Langerhans”
Regulate carbohydrate metabolism (glucose levels in blood).
vascularized clusters of endocrine cells.
Glucagon:
• Promotes the release of glucose from glycogen stores.
• This causes blood glucose levels to increase (hyperglycemia).
• Typically released during fasting.
Insulin:
• Glucose is stored in liver (hepatic tissue) and fat (adipose tissue) as glycogen.
• When insulin is released, these tissues uptake glucose from the bloodstream.
• This causes blood glucose levels to decrease (hypoglycemia).
• Typically released after feeding.
Type I Diabetes
• Insulin deficiency
• Autoimmune disorder
• Islet cells destroyed by immune system
• Treat by injection
• Not hereditary
• Insulin resistance• “adult-onset” diabetes • Over 90% of diabetes • Gradual onset• Hereditary• Associated with age, obesity, physical , ethnic
background and inactivity• Treated by diet
Type II Diabetes
Carbohydrates Lipids Proteins
MouthEsophagus
Amylase Lipase
Stomach Pepsin(Polypeptides)
Lumen
of small
intestine
Amylase(Monosaccharides)
(Disaccharides, Trisaccharides)
Bile salts & lipase
(Monoglycerides& Fatty acids)
Trypsin, et al.!(Short peptides& amino acids)
EpitheliumMonoglycerides
& Fatty Acids
of small Monosaccharides Triglycerides Amino acids
intestine Chylomicrons
Carbohydrates Lipids Proteins
MouthEsophagus
Amylase Lipase
Stomach Pepsin(Polypeptides)
Lumen
of small
intestine
Amylase(Monosaccharides)
(Disaccharides, Trisaccharides)
Bile salts & lipase
(Monoglycerides& Fatty acids)
Trypsin, et al.!(Short peptides& amino acids)
EpitheliumMonoglycerides
& Fatty Acids
of small Monosaccharides Triglycerides Amino acids
intestine Chylomicrons
Carbohydrates Lipids Proteins
MouthEsophagus
Amylase Lipase
Stomach Pepsin(Polypeptides)
Lumen
of small
intestine
Amylase(Monosaccharides)
(Disaccharides, Trisaccharides)
Bile salts & lipase
(Monoglycerides& Fatty acids)
Trypsin, et al.!(Short peptides& amino acids)
EpitheliumMonoglycerides
& Fatty Acids
of small Monosaccharides Triglycerides Amino acids
intestine Chylomicrons
Carbohydrates Lipids Proteins
FACILITATED DIFFUSION & TRANSPORT
MouthEsophagus
Amylase Lipase
Stomach Pepsin(Polypeptides)
Lumen
of small
intestine
Amylase(Monosaccharides)
(Disaccharides, Trisaccharides)
Bile salts & lipase
(Monoglycerides& Fatty acids)
Trypsin, et al.!(Short peptides& amino acids)
EpitheliumMonoglycerides
& Fatty Acids
of small Monosaccharides Triglycerides Amino acids
intestine Chylomicrons
Carbohydrates Lipids Proteins
MouthEsophagus
Amylase Lipase
Stomach Pepsin(Polypeptides)
Lumen
of small
intestine
Amylase(Monosaccharides)
(Disaccharides, Trisaccharides)
Bile salts & lipase
(Monoglycerides& Fatty acids)
Trypsin, et al.!(Short peptides& amino acids)
EpitheliumMonoglycerides
& Fatty Acids
of small Monosaccharides Triglycerides Amino acids
intestine Chylomicrons
Carbohydrates Lipids Proteins
BLOODSTREAM
MouthEsophagus
Amylase Lipase
Stomach Pepsin(Polypeptides)
Lumen
of small
intestine
Amylase(Monosaccharides)
(Disaccharides, Trisaccharides)
Bile salts & lipase
(Monoglycerides& Fatty acids)
Trypsin, et al.!(Short peptides& amino acids)
EpitheliumMonoglycerides
& Fatty Acids
of small Monosaccharides Triglycerides Amino acids
intestine Chylomicrons
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