Digestive System Flashcards
Define Digestion, alimentary and gastrointestinal track
- Mechanical & physical breakdown of food, followed by its absorption.
- Alimentary = GI tract = all of the organs in the tube mouth to anus, about 30 feet
Briefly describe the overall 5 steps of the digestion process
-Ingestion, movement, digestion, absorption, defecation
List the organs of the GI track
- Oral cavity
- pharynx
- esophagus
- stomach
- small intestine
- large intestine
List the digestive accessory organs
- Salivary glands
- teeth
- tongue
- pancreas
- liver
- gall bladder
Describe the 4 layers of the GI track microstructure (in lumen)
- Mucosa- villi (surface area)
- Submucosa- very vascular
- Muscularis - mixes and mores food
- Serosa- visceral peritoneum-Surface connective tissue (watery)
Define parietal and visceral peritoneum and peritoneal cavity.
- Parietal Peritoneum- (Shiny) lines abdominal wall
- visceral peritoneum- covers organs
- peritoneal cavity- space in between
List and describe the location of the 5 peritoneal folds
Binds organs together, anchors them to body wall and suspends blood/lymph
- Mesentery proper- small intestine to posterior body wall
- mesocolon- large intestine to posterior body wall
- Falciform ligament - liver to anterior body wall
- lesser omentum (apron)- lesser curvature of stomach, duodenum to liver
- greater omentum- greater curve of stomach to posterior body wall
Describe the boundaries of the oral cavity
- hard palate ( palatine process of maxilla/ palatine)
- Soft Palate (uvula)
- tongue
- cheeks
Describe the labial frenulum, lingual frenulum, bolus, and papillae.
- Labial frenulum from inner lips to gums
- lingual frenulum from lower tongue to floor of mouth
- bolus is ball of food ready to swallow
- papillae are bumps on tongue including taste buds
Describe the tissue that comprises the tongue
-Skeletal muscle and mucos membrane
-Describe the location of the 4 main taste zones
- sweet- tip
- salt- behind sweet
- bitter- back
- sour-side
Name the 3 pairs of salivary glands
- Parotid
- submandibular
- sublingual
Describe the function, composition, and secretion control of the saliva
- Lubricate & moisten food
- kill bacteria,
- mostly water plus lysozyme, amylase & mucins
- PNS & food & mouth irritation increase salivation
- SNS & fear & dehydration decrease salivation ( dentist will give a shot of atropine to stop digestive juices)
Define gingiva
- gum of the root of the aveoli
Describe the general structure of the tooth
- cementum- bone like covering root of tooth
- enamel-covers dentin on crown (hardest substance in body
- pulp cavity- BV, Nerve, Lymp in cavity in dentin
- dentin- bone like substance (bulk of tooth)
- crown-above
- root- below
- neck-at gum
- apical foramen- end of root canal for nerve and bv to enter/exit
- periodontal ligament- anchors tooth to socket
Name the hardest substance of the tooth
-enamel
Define the directional terms labial buccal lingual palatal occlusal
- labial- lips
- buccal- cheek
- lingual- tongue
- palatal- closest to palate
- occlusal- chewing surface
How many temporary and how many adult teeth in a normal person
temp-20
adult- 32
Describe ingestion, mastication, and deglutition
- Ingestion is eating
- mastication is chewing
- deglutition is swallowing
Define Phayunx, esophageal hiatus, peristalsis, and esophageal sphincters
- Pharynx is throat
- esophageal hiatus is hole in diaphragm for esophagus to pass into abdominal cavity
- peristalsis is wavelike rippling contraction (do not rely on gravity for swallowing)
- esophagus has circular muscles at superior & inferior ends.
describe the function of the esophagus
- transport food
Describe the 4 areas and 2 curves of the stomach (J shaped)
- Cardiac region is where esophagus enters into stomach
- Fundus is storage pouch to the left of cardia
- body is majority of stomach,
- pylorus is inferior end of stomach
- Convex border is greater curvature
- concave border is lesser curvature
Describe the location of the pyloric sphincter
-connects to duodenum (s. Intestine)
Name the substances that comprise gastric juices; name the cells that produce them
- zymogenic cells make pepsinogen ( so we don’t break down our own stomach)
- activates pepsin and breaks down protein
- parietal cells make HCL (alkaline tide following a meal, only stomach can deal with such strong acid)
- protein breakdown, anti-microbial
- Mucus cells make mucus (protects stomach wall)
Name the hormone made by gastric cells
- gastrin
- increases secretions
- caffeine increases gastrin
- increases motility
Define chyme
-liquified food
Describe the mechanism of gastric motility
- Pacemaker cells cause waves of peristalsis from cardia to pylorus.
- If sphincter is closed, the chyme is pushed back towards the cardia and the process starts again.
Describe the stimulation controls of gastric motility
- Presence of food (eating, thinking about) stimulates motility.
- Gastrin, made by pylorus, stimulates motility.
- Certain foods can stimulate motility more than others. Caffeine stimulates gastrin release.
Describe the inhibitory controls of gastric motility
- Enterogastric reflex inhibits motility.
- A distended duodenum causes the release of
- GIP, cholecystokinin & secretin which inhibit gastric motility.
Describe the function of gastric mucus, hydrochloric acid and pepsinogen
- Mucus is so important because it protects the stomach lining from the powerful acid.
- HCl serves to inhibit microorganism growth & breakdown proteins.
- Pepsinogen is converted to an active pepsin in the acid environment which breaks down proteins.
Describe the stimulation mechanisms of gastric secretions
- Presence of food (eating, thinking about) stimulates gastric secretions.
- Gastrin, made by pylorus, stimulates motility.
- Certain foods can stimulate motility more than others. Caffeine stimulates gastrin release.
Describe inhibitory controls of gastric secretions
- -Enterogastric reflex inhibits gastric secretions.
- A distended duodenum causes the release of
- GIP, cholecystokinin & secretin which inhibit gastric motility.
Describe any absorption that occurs from the stomach
- very little
Describe the function of gastrin, secretin, cholecystokinin, and gastric inhibitory peptide
- Gastrin stimulates gastric motility & secretions & is released by stomach (pylorus) cells in response to distention.
- Secretin, cholecystokinin and gastric inhibitory peptide are released by the duodenum in response to distention & inhibit gastric motility & secretions.
Describe the location of the pancreas and pancreatic duct
-Pancreas is inferior to stomach and the duct travels from pancreas to the beginning of the duodenum
Describe the substances made by the pancreatic islet cells
- islets are the hormonal part of the pancreas
- substances include insulin & glucagon
name the cell that makes pancreatic juice
-Acinar cells
Describe the composition of pancreatic juice
- Water
- Bicarbonate
- Amylase
- Lipase
- Proteases (carboxypolypeptidase, trypsin, chymotrypsin)
describe the function of trypin, chymotrypsin, carboxypeptidase, pancretic amylase, and pancreatic lipase
- Trypsin, chymotrypsin, and carboxypeptidase are proteins
- amylase breaks down carbohydrates (starch)
- lipase breaks down fat
Describe the neural and hormonal controls of pancreatic secretions
- Vagus nerve
- (PNS) stimulates secretions
- SNS inhibits it.
- Secretin, Cholecystokinin stimulates pancreatic secretions.
Define hepatocyte
-Liver cell
Describe the course of the common bile duct
-Liver has hepatic duct & gall bladder has cystic duct that join together forming the common bile duct which dumps into the beginning of the duodenum
Name the cells that make bile
-Hepatocyte
Describe the function of the gall bladder
-Stores bile
Describe the composition of bile
-Water, bile salts, bilirubin
Describe the purpose of bile salts and explain what is meant by enterohepatic circulation
- Bile salts Emulsify fat into smaller pieces so that they can be worked on by the lipases.
- The bile salts are recycled by being reabsorbed from the ileum, and returned to the liver to make more bile
describe some mechanisms to stimulate the rate of bile secretion
- Enterohepatic circulation stimulates bile secretion
- vagus nerve
- secretin & cholecystokinin
Breifly, list some function of the liver
- Make bile
- detoxify
- store nutrients, vitamins & poisons
- metabolic hub
- get rid of old blood cells
- makes blood proteins and clotting factors
name the 3 segments of the small intestine
-Duodenum, jejunum, ileum
Define Villi, microvilli and duodenal gland
- Villi are finger-like extensions of the intestinal mucosa which increase surface area available for absorption.
- Microvilli are small ones.
- Brunner’s gland secrete mucus.
Define lacteal
- Intestinal lymph vessel to absorb large particles that cannot fit into blood capillaries,
- fats & proteins.
Describe segmentation and peristalsis
- Segmentation is the sedentary mixing of food in the small intestine
- Peristalsis is the ripple like movement of the small intestine
Define absorbtion, where does 90% of the absorbtion occure
- Broken-down food passes from intestinal lumen into lymph or blood vessels.
- Most occurs in small intestine.
Describe the absorbtion of carbohydrates in the intestine
-Carbohydrates are broken down from saliva & again in duodenum from pancreatic amylase. It absorbs by active transport into blood capillaries.
Define micelle and chylomicron
- Micelle- fat and bile salts
- Chylomicron- break down with in epithelial cells
Describe the various anatomical regions of the large intestine
- Cecum & with appendix are closest to ileum. They are lower right abdomen.
- Then the colon ascends, transverses, descends and has a sigmoid (S shaped) turn before entering…
- the pelvic cavity at which point it becomes the rectum.
- The rectum opens at the anus which is a series of two sphincters.
Define haustra and taeniae coili
- Haustra are the pouches- that divide feces
- Taeniae coli is the the muscle that runs along the large colon that forms the haustra
Describe the gastroileal reflex, haustral churning, mass peristalsis, and the defecation reflex.
- gastroileal reflex when the stomach is full of food, the ileum releases its contents into the LI.
- This causes mass peristalsis of the LI. A couple of times per day, a huge peristalsis occurs in LI forcing contents into rectum.
- stretching the wall of the rectum leading to the defecation reflex in which case the internal anal sphincter relaxes and the person has the urge to defecate.
- Haustral churning is contraction of the colon resulting in mixing & more importantly dividing the contents into smaller pieces in the haustra.
Explain why defecation can be voluntarily controlled
-External anal sphincter is voluntary skeletal muscle
Define Feces
-Solid waste
Describe the basic functions of the large intestine
- Form & store feces.
- Lubricate feces due to numerous goblet cell secretions.
- A speck of water absorption
- Vit B/K synthesis
Describe the products of goblet cells
-Mucus
Describe the breakdown of protein
-Proteins are broken down in stomach
-(HCl & Pepsin)
-pancreatic proteases(enzymes) in S. Intestine
-Trypsin & Chymotrypsin & Carboxypeptidase
Amino acids are absorbed into blood vessels.
Describe the breakdown of Lipids
- Lipids are
- emulsified by bile salts
- broken down by lipases forming a micelle. -Micelle passes through intestinal wall & further broken down & bile salts released for recycling forming a chylomicron which is absorbed into lacteal.
Describe the breakdown of Vitamines
-Vitamins ADEK are absorbed with lipids & Bs and C are absorbed with the water.
Describe the breakdown of water and electrolytes
-A tremendous amount of water is absorbed (9l/day) and electrolytes are absorbed too. Calcium ions require vitamin D for absorption. An electrolyte is a chemical that ionizes when in solution.
What are the hormones of digestion
- Gastrin
- made by the pylorus cells
- Increases gastric motility
- Increases gastric secretions
- Secretin
- Made by distended duodenal cells
- Decreases gastric motility and secretions
- Increases pancreatic juices release
- Increase bile secretion
- Cholecystokinin-
- Made by distended duodenal cells
- Decreases gastric motility and secretions
- Increases pancreatic juices release
- Increase bile secretion
- Increases gall bladder contractions
- GIP (Gastric inhibitory peptide)
- Made by distended duodenal cells
- decreases gastric motility and secretions
- promotes insulin release
Describe the breakdown of carbohydrates
- Salivary amylase (mouth)
- Pancreatic amylase (s Intestine)
- enzymes-lactoase, maltase… (S intestine)
