Digestive part two
What are the functional units of the liver?
hepatic lobules
What are the four main function of the large intestine?
-Absorbs water, bile salts, and electrolytes -absorbs vitamins such as B5,K and biotin -forms and stores feces -carries out defecation
Regulation of pancreatic secretions
-Acidic chyme stimulates release of secretin -secretin stimulates release of watery pancreatic juice with bicarbonate and phosphate - CCK and parasympathetic NS stimulates production and secretion of pancreatic enzymes and zymogens.
What stimulates the small intestine to increase its motility and secretion
-Mucus secretions, because of its presence of chime. -activation of the nerve plexuses -Gastroenteric reflex -Intestinal enzymes
Explain how pancreatic secretions are controlled
1 Acidic chyme enters the duodenum 2 interstitial mucosa releases secretin into bloodstream 3 secretin stimulates pancreas 4 pancreas release bicarbonate ion rich juices 5 bicarbonate ions neutralize, chyme
What are the parts of the large intestine? (You should be able to list these in order in which digested material passes starting from the cecum)
1. Cecum 2. ileocecal valve 3. Ascending colon 4. Transverse colon 5. Hepatic portal vein 6. Descending colon 7. Haustra 8. Sigmoid colon. 9. Rectum
What is the function of the pyloric sphincter?
A prevents food from entering into SI
Composition of bile
A yellow-green, continually secreted by hepatocytss
What are the four functions of CCK on the pancreas?
Act on gallbladder and contract it to release bile, act on pancreas and cause pancreas to contract and then release pancreatic juice, relaxes hepatopancreatic sphincter, and lastly contracts the pyloric sphincter that causes emptying of the stomach.
Describe the components of the portal triad?
At each of six corners of lobule, is a branch of hepatic artery, hepatic vein and bile duct.
What are gallstones
Bile contains calcium salts and cholesterol, both can precipitate and form hard lumps. These lumps are gallstones.
Portal venule
Blood vessel that carries blood from the gastrointestinal, track, gallbladder, pancreas, and spleen to the liver.
What stimulates the release of bile from the gallbladder
CCK
Small bile duct
Carries bile
Define and describe microvilli
Cellular membrane protrusions that increase the surface area for diffusion and minimalize any increase in volume
What is the main function of the small intestine?
Chemical digestion and absorption of nutrients
What is the purpose of proteolytic enzymes?
Continued breakdown of proteins that begin in the stomach
Through which ducts will bile from the pancreas on its way to the duodenum
Cystic duct, common hepatic duct, common bile duct and pancreatic duct.
What are the three segments of the small intestine and in which segment does most chemical digestion in nutrient absorption occur?
Duodenum, ileum and jejunum and the jenunum is where most absorption and chemical digestion occur
Between meals what stops pancreatic secretions from entering the small intestine, and destroying the intestinal wall.
Hepatopancreatic sphincter is closed it guards bile and pancreatic juice from entering the duodenum.
What prevents file from being released into the small intestine between meals?
Gallbladder
Where is bile produced?
Gallbladder
Paths of blood and bile in the hepatic lobule
Hepatic portal vein, sinusoids, central vein, hepatic vein, inferior vena cava
What is the enterogastric reflex?
Inhibits gastric activity and contracts pyloric sphincter.
What is rugae?
Interior of the stomach contains folds called rugae and it allows the stomach to expand considerably
The hepatic arterial
Is a short blood vessel, that supplies oxygenated blood to the liver, pylorus of the stomach, duodenum, pancreas and gallbladder
What is haustral churning and how often does it occur
It is mixing movements and it occurs every 30 min
What is the effect of CCK on hepatopancreatic sphincter and stomach emptying?
It relaxes the hepatopancreatic sphincter
What stimulates the movement of fecal matter into the anal canal
Mass movement.
Define the gastrocolic reflexes? Do they stimulate or inhibit motility through the alimentary canal?
Mass movements- usually follows meals, stimulate
Liver functions: three general categories of function
Metabolic regulation, hematological regulation, synthesis and secretion of bile (role in digestion)
What is the major movements of the large intestine? And what stimulates them
Mixing movements, Mass movements (stimulated by distension of stomach), and peristaltic wave from transverse colon.
List the functions of the stomach
Mixing reservoir, secretion of gastric juice, digestion, facilitates absorption of vitamin B, 12, secretion of gastrin and somatostatin.
Define and describe Villi
Mucosa folded into projections. It consists of a layer of enterocytes surrounding a central core of blood, capillaries and lymphatic vessel
What type of cells carry out digestion in the stomach and what are their respective secretions?
Mucus cells (goblet)- secrete mucus Chief cells (peptic)- secrete digestive enzymes, and Pepsinogen Parietal cells (oxyntic)- secrete HCI (parietal, pH) Endocrine cells- release histamine, serotonin, somastatin and gastrin
What action does the parasympathetic defecation reflects have on the internal and external anal sphincters ?
Note this reflex opens the internal sphincter and closes the external sphincter. Needs voluntary relaxation of the external sphincter for defecation.
What is the approximate PH at which pancreatic secretions function optimally? How is this pH achieved and why is it important?
PH of 8 high pH of pancreatic fluids helps neutralize acid chyme entering SI and provides optimal environment for intestinal and pancreatic enzymes
What is the pH of the empty stomach and what role does pH play in regulating activity of the stomach?
PH of an empty stomach is around 1.5 - 3.5. It activates activity of protein, pepsin, and as food enters the stomach dilutes the H C and the stomach becomes less acidic
Intrinsic Factor is from... and required for what vitamin absorbs
Parietal cells and vitamin B
What is the role of the stomach and vitamin B 12 absorption?
Parietal cells in the stomach secrete intrinsic factor, which is a glycoprotein required for B12 absorption in the SI.
Infants only have what gastric secretions
Rennin and gastric lipase
What stimulates the addition of bicarbonate ions in bile and pancreatic juice?
Secretin
What is chime?
Semi fluid pulp formed in the stomach made of partly digested food and the secretions of the gastrointestinal track
What type of epithelium lines the small intestine
Simple columnar epithelium
What type of muscle are the internal and external anal sphincter's?
Smooth muscle
Functions of secretin
Stimulates release of watery pancreatic juice with bicarbonate and phosphate. Causes the bile ducks to secrete bile rich in HCO3 .
What is the major blood vessel supplying arterial blood to the small intestine
Super mesenteric artery
What blood vessel supply the large intestine with arterial blood
Superior and inferior mesenteric arteries
What veins drain the large intestine into what vessel do these veins drain?
Superior and inferior mesenteric veins and they drain into the hepatic portal vein.
What problems will a person have if their gallbladder is removed
There is no place for bile to collect without a gallbladder, so bile releases directly into the small intestine.
What are chylomicrons and how are the absorbed into circulation
They are formed in the intestinal epithelia and they are surrounded by a shell made up of cholesterol, phospholipids and proteins. The function is the transport dietary triglycerides/ cholesterol
Define and describe the function of the plicae circulares
They are permanent, circular folds of mucosa, that further increase surface area for absorption, and they do not flatten out
Where do the veins of the small intestine drain?
This along with the splenic drain into the portal vein
pancreatic lipase
breaks down triglycerides
Three phases of stomach and what they do
cephalic- begin secretion and digestion gastric- enhances secretion and digestion intestinal- controls rate of gastric emptying and may slow emptying
Pepsinogen comes from
chief cells
Bile salts
derived from cholesterol, emulsify fats, absorption of fatty acids, cholesterol and vitamins.
pancreatic nucleases
digest nucleic acids
Bicarbonate ions
make pancreatic juice alkaline; buffer stomach acid, neutralize chyme
Hydrochloric acid is from
parietal cells
Gastric Secretions
pepsinogen, pepsin, hydrochloric acid, mucus, intrinsic factor
What is the livers role in digestion?
produce bile
Pancreatic Amylase
splits starch and glycogen into disaccharides, breakdown carbohydrates
Main function of the gallbladder
store and concentrate bile and release bile under CCK