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how does digestion contribute to homeostasis?
- 1-break down food
- 2-absorbs vitamins, water,minerals fuel needed for the body
- 3-eliminates wastes
the process of breaking down large food molecules into smaller molecules that can be absorbed by the body
what are the four tunics of the GI tract
describe the mucosa layer
mucous membrane, surrounded by lumen in the contact with food.
how many layers does mucosa tunic have
what are is the name of the 3 mucosa layers
- 2-lamina propria
- 3-muscularis mucosae
what type of cells does the epithelium consist of in the mucosa tunic
simple columnar epithelium
what is the function of the epithelium in the GI tract
secretion and absorption
what is the function of the lamina propria?
to support the epithelium and bind it to the muscularis mucosae
What type of tissue makes up lamina propria
areolar connective tissue
what can you expect to find in the lamina propria
1-blood and lymphatic vessels-routes by which nutrients absorbed by the GI tract reaches other tissues
2-MALT-mucosa associated lymphatic tissue
what type of cells creates muscularis mucosae?
what is the function of muscularis mucosae?
it creates folds which increase the surface are for digestion and absorption. The movement of the muscularis mucosae ensures all absorptive cells have contact with intestinal content
what type of tissue makes up submucosa?
areolar connective tissue, covered by epithelium
what kind of vessels can you find in the submucosa?
1-blood and lymphatic vessels that receive absorbed food molecules
2-an extensive network of neurons known as submucosal plexus
what is the function of the submucosal plexus?
regulate the secretion and activity of the GI Track
What is the function of the submucosa?
binds mucosa to muscularis and supports the mucosa
what type of tissue makes up the muscularis tunic of the GI tract?
- -two layers of smooth muscle
- 1-circulatory muscles
- 2-longitudinal muscles
what is the function of muscularis tunic of the GI tract?
to help break down food, mix it with digestive secretions and propel food along the tract by creating involuntary contraction
what is the name of the neuron network found in muscularis?
what is the function of the myenteric plexus?
control motility (movement) in strength and frequency of the muscularis
is the serosa considered to be serous membrane?
yes, the serosa is considered to be serous membrane
what is serosa composed of?
areolar connective tissue line with a layer of simple squamous epithelium plus fibrous connective tissue
what is the function of the serosa?
creates lubrication fluid for the organs to glide. its used as a hanger for the digestive system
Describe the general anatomy of the digestive system
mouth, pharynx, esophagus, stomach, small intestine and large intestine
what are the two main group of organs or regions with the digestive system?
GI Tract and accessory organs
name the two organs that make up the alimentary canal or GI tract
GI track and accessory organs
name the accessory organs
teeth, tongue, salivary glands, liver pancreas and gullbladder
which areas of the digestive system uses stratified squamous epithelium?
the esophagus and the rectum
what is peritoneum?
its serous membrane
what is the function of the peritoneum
to reduce the friction between organs
where does the greater omentum attach to?
between the stomach and transverse colon
how many layers does the greater omentum have?
four in total. its composed of a double layer sheet that has two folds
what abundant tissue can you find in the greater omentum?
What is the function of the coronary ligament?
connect the liver to the diaphragm
what is the function of the lesser omentum?
suspend the stomach and duodenum from the liver
what is the function of the mesentery?
it bind the jejunum and ileum of the small intestine to the posterior abdominal wall
what is the function of the mesocolon?
bids the transverse colon and sigmoid colon to the posterior of the abdominal wall
what are the seven function of the digestive system?
- 3-mixing and propulsion
taking of food, driving by smell, taste and sight
production of fluid such as water, acid, buffers, enzymes and waste. about 9 liters a day
describe mixing and propulsion
propulsion is swallowing and peristalsis(progression of contractions meant to push bolus )
name the two types of digestion
mechanical and chemical
define chemical digestion
the breaking of molecular bonds through HYDROLYSIS and ENZYMES
describe absorption stage
the process which the takes in nutrients, vitamins and other materials the body needs.
name the two types of absorption process
active and passive
describe the defecation stage of digestion
the way which the body disposes of waste
describe the "also" stage of digestion
immune, sensory and water balance
what happens to proteins in chemical digestion?
proteins become amino acids
what happens to carbs in chemical digestion?
carbs are converted to simple sugars
what happens to lipid in chemical digestion?
lipids are converted into fatty acids and glycerol
what happens to nucleic acids in chemical digestion?
nucleic acids are converted to nucleotides
name the 4 glands found in the mouth?
- 1-parotid gland
- 2-sublingual gland
- 3-submandibular gland
- 4-buccal gland
what is the function of the 3 glands found in oral cavity?
to secrete saliva
how much do the salivary gland secrete
1 to 1.6 liters of saliva a day
what is saliva composed of?
99.5% water and .05% solutes
what is the function of saliva?
moisten food, bacteriolysis, begins digestion
what kind of solutes can one expect to find in saliva?
sodium, potassium, chloride, bicarbonate and phosphate
what kind of enzymes can you find in saliva?
- 1-salivary amylase
- 2-lingual lipase
- 3-immunoglobulin A
what is salivary amylase?
an enzyme that breaks-down starches in the mouth into maltose, maltoriose and alfa-dextrin
what is the function of lingual lipase
It breaks down dietary triglycerides (fats and oils) into fatty acids and diglycerides. Lingual lipase enzymes becomes activated in the acidic environment of the stomach.
what is the function of Immunoglobulin A?
to prevent attachment of microbes so they cannot penetrate the epithelium.
what is the function of the enzyme lysozyme?
what does the term BOLUS mean?
lump of food when its reduced to a soft, flexible and easy to swallow.
what is deglutition?
the process of swallowing
what are the 3 stages of deglutition?
- 1-voluntary stage-at oral cavity
- 2-pharyngeal stage-pharynx
- 3-esophageal stage-esophagus
describe the voluntary stage of deglutition
bolus moves into the mouth
describe the pharyngeal stage of deglutition
respiratory passages are closed off. Stimulated receptors send information to deglutition center in the medulla oblongata
describe the esophageal stage of deglutition
circular and longitudinal muscles contract and bolus moves forward by peristalsis
what are the four layers of the esophagus?
1-mucosa-non-keratinized stratified squamous epithelium
2-submucosa-areolar connective tissue
3-muscularis-contains 1/3 skeletal muscle, 1/3 mix of skeletal and smooth muscle and 1/3 of smooth muscle
4-adventitia-attached esophagus to surrounding structures
name the two sphincters associated to the esophagus
1-upper esophageal sphincter-related when larynx is elevated
2-lower esophageal sphincter-connected at the stomach
what type of cells can you find in the mucosa layer of the stomach?
- 1-surface mucus cells
- 2-mucus neck cells
- 3-parietal cells
- 4-chief cells
- 5-G cells
what does surface mucus cells produce?
secretes mucus at surface of mucosa
what does the mucous neck cell produce?
secretes mucous in the gastric pit
what is the function of parietal cells?
secretes hydrochloric acid and intrinsic factors.
what is the function of chief cells?
secrete pepsinogen and gastric lipase
what is the function of G cells?
secrete the hormone gastrin
what is the function intrinsic factor in the parietal cell?
needed for absorption of vitamin B12 for rbc formation
what is the function of HCL in the parietal cell?
- 1-kill microbes in food
- 2-denature proteins
- 3-convert pepsinogen into pepsin
what is the difference between pepsinogen and pepsin?
pepsinogen is not activated while pepsin is the activated form
what is the function of pepsin?
break down proteins into peptides
what are peptides?
two or more amino acids linked together
what is the function of gastric lipase?
splits triglycerides into fatty acids and monoglycerides
what is the function of gastrin?
1-stimulate parietal cells to secrete HCL and chief cells to secrete pepsinogen.
- 2-contracts lower esophageal sphincter
- 3-relaxes pyloric sphincter
- 4-increase stomach motility
what is the pancreas composed of?
small clusters of glandular epithelium cells
what are the cluster of the pancreas composed of?
1-99% of cluster is composed of Acini
2-1% of cluster is composed of pancreatic islets
What is pancreatic Acini?
the exocrine portion of the pancreas that creates pancreatic juice.
what does exocrine mean?
what is the function of pancreatic juice?
1-buffer acidic gastric juice in chyme
2-stops the action of pepsin in the stomach
3-creates proper pH for the action of digestive enzymes in the small intestine
what are pancreatic islets?
the endocrine portion of the pancreas that secrete glucagon, insulin, somatostatin and pancreatic polypeptide.
what is the function of the exocrine portion of the pancreas?
to create digestive enzymes
what is the function of the pancreatic islets?
what type of hormones does the pancreas produce?
- 3-pancreatic polypeptide
what is the function of insulin?
control blood sugar levels
what is the function of glucagon?
deals with low levels of glucose
what is the function of pancreatic polypeptide
stimulates secretion of ions and water by the intestines and inhibits gastric acid secretion
what is the function of somatostatin?
inhibits gastrin release
what are the 11 functions of the liver?
- 1-metabolises carbs, lipids and proteins
- 2-detoxifies blood
- 3-removes drugs and hormones
- 4-synthesis, store and break down glycogen
- 5-manufactures plasma membrane
- 8-storage of copper, iron and some vits
- 9-activates vitamin D
- 10-synthesises bile salt
- 11-secretion of bile
name the three parts the small intestine is divided into
what type of cells can one expect to find in the mucosa layer of small intestine?
- 1-absorptive cells with microvilli
- 2-goblet cells
- 3-enteroendocrine cells
- 4-paneth cells
what is the function of absorptive cells?
digestion and absorption
what is the function of goblet cells?
what is the function of the paneth cell?
what are the e hormones enteroendocrine cells produce?
produce 3 hormones,
- 3-Glucose-dependent insulinotropic peptide (GIP)
what are the four processes needed to digest food?
- 1-motility (movement)
what is the daily ingested or secreted fluid by the body?
- 1.0 liter of secreted saliva
- 2.3 liters of ingested fluid
- 2.0 liters of gastric juice
- 1.0 liter of secreted bile
- 2.0 liters of secreted pancreatic juice
- 1.0 liter of intestinal juice
total of 9.3 liters
what is the daily amount of fluid absorbed by the body?
- 8.3 liters absorbed by the small intestine
- 0.9 liter absorbed by the large intestine
total of 9.2 liters
how is the regulation of gastric secretion and motility controlled?
the nervous system or endocrine system
what are the e phases of digestion?
- 1-cephalic phase
- 2-gastric phase
- 3-intestinal phase
describe the physiology of the cephalic phase of digestion
sensory inputs sends signals to cerebral cortex and feeding center in the hypothalamus which in response sends signals to medulla oblongata to parasympathetic preganglionic fibers of the vagus nerve to postganglionic fibers that go the the myenteric and submucosal plexus.
what does the myenteric plexus stimulate?
what does the submucosal plexus stimulate?
secretion into the stomach
describe the physiology of the gastric phase
- food reaches stomach, receptors in the stomach will stimulate
- 1-hormonal reflex
- 2-neural reflex
what does neural reflex do?
- 1-motility and secretion
- 2-increase gastric juices
- 3-increase contraction of stomach which will force 10-15 ml of food into intestine
what does hormonal reflex do?
what is the function of gastrin?
- 1-gastric glands
- 2-strengthen contractions
- 3-tighten lower esophageal sphinceter
- 4-relax the pyloric sphincter
what releases gastrin?
- 1-distention of stomach
- 2-partially digested proteins
- 3-high pH of chyme
what is the function of secretin?
stimulates the flow of pancreatic juice that is rich in bicarbonate ions to buffer the acidic chyme that enters the duodenum
what is the function of Cholecystokinin (CCK)?
- stimulates secretion of pancreatic
- juice that is rich in digestive enzymes. It also causes contraction of gallbladder, which squeezes out stored bile
what digestive enzyme substrates (acts on) carbs?
lingual lipase and pancreatic amylase
what digestive enzyme substrates on protein?
what digestive enzyme substrates on triglycerides?
what digestive enzyme substrates on nucleic acid?
how is pancreatic secretion regulated?
pancreatic secretion is regulated by sphincter or oddi
true or false?
digestive enzymes in the pancreas are released in an active form?
pancreatic enzymes are released in an inactive form so they don't digest the pancreas
what are brush border enzymes?
brush border enzymes are digestive enzymes located at the surface of microvilli
what macromolecules do brush border border enzymes break down?
what are the 2 mixing and mechanical digestion that occurs in the small intestine?
- 2-migrating motility complexes
what is the stage of each of the 4 macromolecules when they are absorbed into the cells?
1-monosaccharides are simple sugars
2-amino acids stay amino acids
3-triglycerides are small/large chains of fatty acids
4-nucleotides are nucleic acids
what happens to lipids in the small intestine?
they are broken down to monoglycerides
what does your body in terms of carbs, proteins, triglycerides and nucleic acid absorpb?
- proteins=amino acids
- nucleic acids=nucleotides
which molecules are actively absorbed?
glucose, galactose, amino acids, di and tripeptides
which molecules are absorbed by diffusion?
fructose, short and long chain fatty acids
how is water absorbed?
what components of diet helps your body absorb water?
electrolytes, monosaccharides and amino acids
how are electrolytes and amino acids absorbed?
via active transport mechanisms?
what are the two types of movement in the large intestine?
- 1-gastroileal reflex
- 2-mass peritalsis
does the large intestine secrete any enzymes?
what type of chemical digestion takes place in the large intestine?
what important component of your diet is absorbed in the large intestine?
vitamin B and K
when does chyme become feces?
3-10 hours when chyme has become solid or semisolid
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