Terms in this set (95)
Through what structures does the food travel?
5. Small Intestine
6. Large Intestine
What is the function of the GI system?
To transfer organic nutrients, salts, and water from the external environment to the internal environment.
Review the organization of the wall of the GI tract.
Explain the two type of digestion.
Mechanical Digestion: breaks down food particles into smaller pieces
1. Breaks down food with the use of enxymes
2. Enzymes allow chemicals bonds to be broken
3. Proteins are broken down successively into
4.(Carbs) Polysaccharides-->Disaccharides--> monosaccharides
5. Lipid--> fatty acids and glycerol
What are the breakdown products of proteins?
What are the breakdown products of carbohydrates?
What are the breakdown products of lipids?
fatty acids and glycerol
What kind of digestion takes place in the mouth?
Mechanical digestion uses the teeth to break down the food into smaller pieces
What does the enzyme ptyalin do and from where is it secreted?
-Also called salivary amylase
-Starts chemical digestion in the mouth
-Initiates carb digestion
-Secreted by the parotid salivary gland
-Optimum pH for the salivary amylase is pH 6.9
What does the submandibular and sublingual glands secrete?
-Secrete a mucopolysaccharide called mucus and serous fluid
-Mucus solution moistens and lubricates the food particles
What is bolus?
The mass of food being swallowed is called a bolus
What is deglutition?
The act of swallowing the food is called deglutition
What is the function of the pharynx?
-Contains the Oropharynx and Laryngopharynx
-Contributes nothing to digestion
-Simple a passageway
What is the function of the esophagus?
-Doesn't contribute to digestion
-Is a passageway-transports food by peristalsis
The movement of food in the esophagus occurs by a process called what?
What are the 4 regions of the stomach?
1. Cardiac region
4. Pyloric region
What are the 2 functions of the stomach?
1. Chemical breakdown of proteins
2. Mechanical breakdown by the rugae (folds of stomach wall)
What are the 3 types of cells in the stomach and what do they secrete?
1. Chief cells produce two enzymes
2. Parietal cells
a. secrets HCl- hydrochloric acid
b. secrets intrinsic factor which is necessary for Vitamin B12 absorption by the small intestine
3. Mucous cells secretes mucus
What activates pepsinogen?
HCl- Hydrochloric acid to activate pepsin which is a protease enzyme that breaks down proteins and is most active at pH 1.5 to 2.5
What does rennin do?
-Is a protease which breaks down milk protein casein into paracasein
a. Milk proteins casein can't be digested by pepsin
b. Paracasein can be digested by pepsin so milk protein in casein has to be converted to paracasein by rennin in order to be digested
Where does protein digestion begin?
Explain how protein digestion takes place.
-Two enzymes that initiate the protein digestion are pepsin and rennin
-Entrance of food in the stomach stimulates the release of a hormone Gastrin from the stomach cells into the blood which causes the release of pepsinogen and rennin from the chief cells and the release of HCl from the parietal cells
What are the 3 functions of HCl?
a. activates inactive pepsinogen--> pepsin
b. maintains pH of stomach between pH 1.5-2.5 so that pepsin and rennin can function optimally
c. kills microorganisms which are ingested
Explain how HCl secretion takes place
What happens when a person frequently vomits?
-Low HCl in stomach causes high HCl secretion by parietal cells--> high HCO3 going into blood--> metabolic alkalosis
Why doesnt the HCl eat away the lining of the stomach?
Mucus secretion lines the epithelial lining to prevent the HCl from eating away the walls
What controls HCl secretion?
a. Cephalic stimulus
b. Gastric stimuli
c. Intestinal stimulu
What is the cephalic stimulus?
The sight, smell, and taste of food stimulates the vagus PSN and the release of gastrin which increases the secretion of HCl from the parietal cell
What is the gastric stimulus?
Distention of the stomach, a decrease in H+ or peptides in the stomach causes the stimulation of the vagus PSN and the release of gastrin both of which increases the secretion of HCl
What is the intestinal stimuli?
In the small intestine, an increase in osmolarity, an increase in H+, or distention of the small intestine inhibits the vagus PSN and causes the release of the hormone gastrin inhibitory peptide (GIP) both of which inhibit HCl secretion
What is absored in the stomach?
a. only a little water
What are the 3 regions of the small intestine?
What are the 2 functions of the small intestine?
1. Terminal digestion of food
2. Absorption if digested food
What are villus, where are they found, and what is their function?
-Inner wall of small intestine is thrown into folds called villi
-Inner layer of villus is composed of simple columnar epithelium
-Each villus has:
a. a lacteal duct (a lymphatic duct)
b. a rich supply of capillaries for proteins, monosaccharides, disaccharides
What are microvilli, where are they found, and what are their function?
-The call membrane of the columnar epithelial cell facing the lumen is thrown into folds called microvilli
a. Microvilli do not move, unlike cillia
b. Microvilli are extensions of the cell membrane which increases the surface area of the cell membrane, allowing for more absorption of digested food
What is a lacteal duct and what is its function?
-lymphatic capillary that absorbs dietary fats in the villi of the small intestine.
-Carbs, amino acids, lipids go through lymphatic duct
Where does terminal digestion of food occur?
Small intestine, mostly duodenum
What 3 fluids are involved in terminal digestion of food?
a. Pancreatic juice
c. intestinal juice
Of what is pancreatic juice composed off and what is the function of each component?
Pancreatic juice is composed of:
a. Proteinases or proteases which are enzymes that break protein
b. amylases-enzymes which break down carbs to maltose, maltriose, and short oligosaccharides
c. lipases are enzymes which break down lipids
d. bicarbonate ion- HCO3
Where is bile synthesized, where is it stored and what does it do?
-Synthesized in the liver
-Stored in the gallbladder
-Facilitates the digestion of lipids
-Lowers the surface tension around the lipid molecules (It emulsifies large lipid molecules so that lipase enzymes can be exposed to more surface area and thus break down lipids more rapidly)
What are the components of intestinal juice and what are the functions of each of the components?
a. contains enterokinase which converts trypsinogen to trypsin
b. contains peptidases which are enzymes that break down peptides into amino acids
c. contains disaccharidases which break down disaccharides to monosaccharides
1. Sucrase breaks down sucrose into glucose and fructose
2. Lactase breaks down lactose into galactose and glucose
3. Maltase breaks down lactose into 2 glucose molecules
d. Lipases break down lipids into fatty acids and glycerol or monoglycerides
What is the partially digested food called as it enters the small intestine?
What is the endocrine gland, the target tissues, and the actions of the hormone secretin?
Endocrine gland: Small intestine, duodenum
Target tissues: pancreas and liver
Action: 1. secretin goes to pancreas and stimulates bicarbonate ion secretion into the duodenum which neutralizes the acid from the stomach
2. Goes to the liver and stimulates the secretion of bile which emulsifies lipids aiding digestion
-Protein- Cyclic aMP
What is the endocrine gland, the target tissues, and the actions of the hormone cholecystokinin?
Endocrine gland: Small intestine, duodenum
Target tissues: pancreas and gallbladder
Action: 1. goes to the pancreas and causes the enzymes to be secreted into the duodenum
2. goes to the gallbladder and causes contraction of the gallbladder, releasing bile
-Protein- cyclic aMP
What does enterokinase do and where is it secreted from?
-Released from he small intenstine cells
What does trypsin do?
-Activates chymotrypsinogen into chymotrypsin
-Activates procarboxypeptidase into carboxypeptidase
What are the 3 inactive proteinases secreted from the pancreas?
Where doe carbohydrate digestions begin?
In the mouth by salivary amylase and breaks the starch into maltose, maltriose, and short oligosaccharides
Where does protein digestions begin?
Where does lipid digestion begin?
Begins and ends in the small intenstine
Where is folic acid absorbed?
Where is vitamin D absorbed?
Where is calcium absorbed?
Where is fat absorbed?
Where is Iron absorbed?
Where are amino acids absorbed?
Where is magnesium absorbed?
Where is vitamin B12 absorbed?
Where is glucose absorbed?
Where is vitamin D absorbed?
Where is thiamine absorbed?
Where is vitamin A absorbed?
Where is pyridoxine absorbed?
Where is vitamin K absorbed?
Where are bile salts absorbed?
Where is ascorbic acid absorbed?
Where is vitamin E absorbed?
What are the functions of the large intestine?
-absorption and concentration
-mainly the colon, absorbs water and sodium (aldoterone)
-concentrates the food which was indigestible and those substances which were not absorbed
What does the large intestine absrob?
water and sodium
What is the endocrine gland, the target tissues, and the actions of the hormone gastrin?
Stimulates acid secretion and enzyme secretion
What stimulates the release of gastrin?
stimuli for release are:
-peptides in the stomach
-distension of stomach
-Decrease in H+
What inhibits the release of gastrin?
Secretion is inhibited by and increase in gastric secretion
What is the endocrine gland, target tissues, and actions of the hormone gastrin inhibitory peptide?
Action: -Stimulus for release is fatyy acids or monosaccharides in small intestine
-Inhibits acid secretion in the stomach
What relaxes the smooth muscle of the cardiac region of the stomach in the reception of food?
When one swallows food, the vagus PS nerves are stimulted which relaxes the smooth muscle of the cardiac region of the stomach
What causes gastric motility?
When food reaches the stomach, perisaltic waves of contraction occur in the stomach musculature, via vagus PS nerve stimulation
Stimulus of gastric emptying is the distension of the stomach
What nerve is involved in gastric motility?
What inhibits gastric emptying?
1. There is distension of duodenum
2. There is the presence of fat, acid, or hypertonic solution in the duodenum (fat most potent inhibitor)
3. There is distension of ileum (ileogastric reflex)
What is segmentation?
1-4 cm section of small intestine contracts and relaxes and churns food in tube
What increases small intestine motility?
Hostility increases small intenstine motility
What decreases small intestine motility?
Fear decreases small intenstine motiliy
What is the stimulus for increased large intestine motility?
Eating via the gastroileal reflex-gastric emptying increases ileal motility which moves material into the large intestine
What is the stimulus for defecation?
Distension of rectum
How does the respiratory system play a role in defecation?
1. Deep inspiration
2. Contraction of ab and chest muscles
a. this increases intraabdominal pressure
b. which increaases pressure on the large intestine
c. Smooth muscle of the rectum contracts via the PS sacral nerves 2,3,4
What kind of muscle is the external anal sphincter composed of, what type of nerve innervates it, and what kind of receptors are found on the muscle and what is its function?
-made up of skeletal muscle
-under voluntary control
-During defecation the external anal sphincter is relaxed because the somatic efferent prudential nerve (part of sacral nerve 4) is inhibited
Name the water soluble vitamins?
What is the function of riboflavin?
Forms Flavin adenine dinucleotide (FAD)
-Krebs cycle donates electrons to electon transport chain to make ATP
What is the function of nicotinic acid?
-Forms Nicotineamide adenine dinucleotide (NAD)
-Functions in the electron transport chain
What is the function of folic acid?
1. Deficiency results in
-failure to grow, it is necessary for purine and pyrimidine synthesis and some A.A
-anemia (for RBC maturation and development)
2. Deficiency in pregnant woman can lead to
-neural tube defect such as spina bifida in the baby
What is the function of vitamin B12?
-Essential for normal maturation and development of RBC's (essential for DNA synthesis)
-requires intrinsic factor from the stomach which binds Vit B12 and carries it into the intestinal cells
-Deficiency results in pernicious anemia
What is the function of of vitamin A?
-Found in fish
-Formed from the cleavage of B carotene
-Can be obtained from green and yellow vegetable (lettuce, spinach, carrots)
-in adults, deficiency can lead to night blindness (Rhodopsin)
What is the function of of vitamin E?
-has antioxidant activity-which prevents the autooxidation of highly unsaturated fatty acids when they are exposed to oxygen
-May function to protect the highly unsaturated fatty acids in lipids of biological membranes against the deleterious effects of molecular oxygen
What is the function of vitamin D?
Vitamin D plays a role in the transport of Ca across the cell membrane
What is the function of vitamin K?
-Required for normal blood clotting (for formation of prothrombin)
-K stands for "Koagulation"
-Dicumarol is a drug used to prevent clotting. It blocks Vitamin K action
1. Vitamin K2-active form
2. Vitamin K3 or Menadione-synthetic product
Know the pathway for Vitamin D. Know what is needed at each step and where each step takes place
Pathyway on notes
Name the fat soluble vitamins?
Vitamin A, E, D, K
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