Exam 3 slides 4

Question 1

Be prepared to label the different regions and anatomical features of the stomach

Answer 1

o A J-shaped sac; temporary storage tank (2-6 hours) and site of demolition
o Starts chemical digestion – the breakdown of proteins
o Chyme: “juice”, liquified slurry of food
o Portions:
 Cardia
 Fundus
 Body
 Pyloric Portion: antrum, canal, pylorus, pyloric sphincter
o Lesser and Greater Curvatures
o Lesser and Greater Omenta
o Stomach volumes:
 Empty: ¼ cup; Full: 1 gallon
o Rugae: mucosal folds seen in an empty stomach

Question 2

What is the term for a bolus of food after it is undergoing digestion in the stomach?

Answer 2

o Chyme: “juice”, liquified slurry of food

Question 3

How are the tunics modified in the stomach? What is the physiological importance of these modifications?

Answer 3

o Modified Tunics
 Muscularis has an added internal, oblique layer to allow increased mixing and churning – more intense mechanical breakdown
 Mucosa contains simple columnar epithelium made entirely of mucous cells – produces a cloudy, protective double layer of alkaline mucus
* Dotted with millions of deep gastric pits
* Gastric pits lead into the gastric glands responsible for producing gastric juice

Question 4

Know the different secretory cells in the gastric glands. What are their functions?

Answer 4

o The glands of the fundus and body are substantially larger and produce the majority of the stomach’s secretions
o Secretory Cells
 Mucus Neck Cells: produce thin, soluble mucus
 Parietal Cells: produce HCl (pH 1.5-3.5, required to activate pepsin) and secrete intrinsic factor (required to absorb B12)
 Chief Cells: secrete pepsinogen (inactive pepsin) and lipases
 Enteroendocrine Cells: secrete chemical messengers into the lamina propria as well as gastrin

Question 5

Define mucosal barrier. How is it created? What causes most peptic/gastric ulcers?

Answer 5

o Gastric juice is a corrosive acid with the ability to digest the stomach itself
o Mucosal Barrier: produced to protect the stomach
 A thick coating of bicarbonate-rich mucus
 Tight junctions between epithelial cells
 Quick replacement of damaged mucosal cells by stem cells
o Peptic/Gastric Ulcers: erosions of the stomach wall – cause gnawing, epigastric pain
 Pain typically appears 1-3 hours after eating and resolves with eating again
 Ulcers are linked to peritonitis and H. pylori – a type of acid resistant bacteria

Question 6

Review the different functions completed in the stomach.

Answer 6

o Propulsion: peristalsis
o Mechanical Breakdown: churning
o Digestion: breakdown of proteins by HCl & pepsin
 Rennin in infants
o Absorption: only lipid-soluble substances - alcohol and aspirin
o Secretion of Intrinsic Factor: essential for B12 absorption and maturation of RBCs

Question 7

Which branch of the autonomic nervous system increases gastric secretions? Define gastrin.

Answer 7

o > 3L of gastric juice is secreted/day
o Neural Mechanisms of Regulation
 Stimulation by the vagus nerve increases secretion
 Stimulation by the sympathetic nervous system decreases secretion
o Hormonal Mechanisms of Regulation
 Gastrin stimulates secretion of HCl by the stomach
 Gastrin stimulates secretion of gastrin antagonists by the SI

Question 8

What are the 3 phases of gastric secretions? What is the trigger for each phase?

Answer 8

o There are 3 phases of gastric secretions – the phases can happen simultaneously
o Cephalic/Reflex Phase: triggered by smell, taste, and sight; act via the vagus nerve
o Gastric Phase: triggered by stretch receptors and/or chemical stimuli – partially digested protein, caffeine, rising pH
 Activates G Cells (enteroendocrine cells) to secrete gastrin
 Gastrin initiates release of HCl
 Low pH (between meals) or firing of the SNS will inhibit gastrin
o Intestinal Phase: partially digested food enters the SI and triggers the release of intestinal gastrin
 Distention of the SI and/or the presence of acidic, fatty, or hypertonic chyme will inhibit gastric secretions – protects the SI from excess acidity and being overwhelmed
 Enterogastric Reflex: short reflexes by the enteric nervous system and long reflexes by the sympathetic and vagus nerves inhibit acid secretion
 Enterogastrones: duodenal enteroendocrine cells release secretin or cholecystokinin (CCK) to inhibit gastric secretions

Question 9

What is cephalic/reflex phase?

Answer 9

o Cephalic/Reflex Phase: triggered by smell, taste, and sight; act via the vagus nerve

Question 10

What is gastric phase?

Answer 10

o Gastric Phase: triggered by stretch receptors and/or chemical stimuli – partially digested protein, caffeine, rising pH
 Activates G Cells (enteroendocrine cells) to secrete gastrin
 Gastrin initiates release of HCl
 Low pH (between meals) or firing of the SNS will inhibit gastrin

Question 11

What is intestinal phase?

Answer 11

o Intestinal Phase: partially digested food enters the SI and triggers the release of intestinal gastrin
 Distention of the SI and/or the presence of acidic, fatty, or hypertonic chyme will inhibit gastric secretions – protects the SI from excess acidity and being overwhelmed
 Enterogastric Reflex: short reflexes by the enteric nervous system and long reflexes by the sympathetic and vagus nerves inhibit acid secretion
 Enterogastrones: duodenal enteroendocrine cells release secretin or cholecystokinin (CCK) to inhibit gastric secretions

Question 12

Define enterogastric reflex and the role of enterogastrones.

Answer 12

o Pressure rises in the stomach after 1.5L of food has been ingested
o Liquids pass quickly through the stomach, but solids linger
o The stomach typically empties in ~4 hours
o The duodenum prevents overfilling by controlling how much chyme enters - stretch and chemical receptors trigger the enterogastric reflex and enterogastrones to inhibit gastric secretions and to reduce the force of pyloric contractions
o Carbohydrate-rich foods move quickly through the duodenum, but fats form an oil layer atop chyme and are digested more slowly
o Fatty chyme delays stomach emptying – may remain for ~6 hours

Question 13

What is the digestive function of the liver? What purpose does bile serve?

Answer 13

o Liver: many functions, but its digestive function is the production of bile
 Bile: fat emulsifier
 Produces about 900mL of bile/day
 Additional functions: processes bloodborne nutrients, stores fat-soluble vitamins, and performs detoxification

Question 14

Be prepared to label the lobes of the liver and two major ligaments.

Answer 14

o The body’s largest gland; weighs about 3lbs
o Lobes: right, left, caudate, and quadrate
o Falciform Ligament: separates the larger right lobe from the smaller left lobe and suspends the liver from the diaphragm and anterior abdominal wall
o Round Ligament/Ligamentum Teres: remnant of fetal umbilical vein; runs along the free edge of the falciform ligament

Question 15

What is the liver’s functional unit? What is a specialized liver cell? What is contained in a portal triad?

Answer 15

o Liver Lobules
 Hexagonal structural and functional units
 Composed of plates of hepatocytes (liver cells) that filter and process nutrient-rich blood
 Hepatocytes have increased numbers of rER, sER, Golgi complexes, peroxisomes, and mitochondria
 Central Vein: located in the longitudinal axis
o Portal Triad: located in each corner of the lobule
 Hepatic Artery: supplies Oxygen to the liver
 Hepatic Portal Vein: brings nutrient-rich blood from the intestines
 Bile Duct: receives bile from bile canaliculi

Question 16

Know what is being carried in each vessel of the portal triad.

Answer 16

o Portal Triad: located in each corner of the lobule
 Hepatic Artery: supplies Oxygen to the liver
 Hepatic Portal Vein: brings nutrient-rich blood from the intestines
 Bile Duct: receives bile from bile canaliculi

Question 17

What’s the function of hepatic macrophages?

Answer 17

o Stellate/Hepatic Macrophages: exist in liver sinusoids to remove debris and old RBCs

Question 18

What type of lipid makes up bile salts? What is bilirubin and how is it formed?

Answer 18

o Yellow-green, alkaline solution
o Contains:
 Cholesterol, triglycerides, phospholipids, electrolytes AND
 Bile Salts: cholesterol derivatives that function in fat emulsification/absorption
 Bilirubin: yellow pigment formed from heme during the breakdown of RBCs
* Metabolized by bacteria in the SI to stercobilin which gives feces a brown color
o Enterohepatic Circulation: recycling mechanism that conserves bile salts – salts are reabsorbed in the ileum and returned to the liver via hepatic portal blood
 95% of secreted bile is recycled, 5% newly synthesized

Question 19

What portion of the SI reabsorbs bile salts for recycling?

Answer 19

ileum

Question 20

What’s the pathway for bile moving out of the liver?

Answer 20

o Enterohepatic Circulation: recycling mechanism that conserves bile salts – salts are reabsorbed in the ileum and returned to the liver via hepatic portal blood

Question 21

Compare and contrast hepatitis and cirrhosis.

Answer 21

o Hepatitis: inflammation of the liver
 Typically, viral infection, but can be caused by alcohol, drug toxicity, or wild mushrooms
 Six Viruses: A-F; 2 transmitted through food, remainder via blood
o Cirrhosis: progressive, chronic inflammation from hepatitis or alcoholism
 Liver activity is depressed
 Liver becomes fatty and fibrous
 Portal Hypertension: flow of blood through the liver is obstructed
o Liver transplants are often successful
o After 80% removal, the liver can regenerate to its full size within 6-12 mos

Question 22

What’s the function of the gall bladder? Be prepared to label the cystic and bile ducts.

Answer 22

o Thin-walled, muscular sac on the inferior surface of the liver
o Appears green when filled with bile
o Functions to store and concentrate bile
o Contains many honeycomb folds that allow for expansion
o Muscular contractions release bile via the cystic duct – flows into the common bile duct

Question 23

Define a gallstone and state its relationship to jaundice.

Answer 23

o Causes: excess cholesterol or too few bile salts
o Cholesterol crystalizes into stones
o Gallstones can obstruct the flow of bile from the gallbladder
o Painful when the gallbladder contracts against sharp crystals
o Cholelithiasis: obstructed flow of bile from the gallbladder
o Obstructive Jaundice: blockage causes bile salts and pigments to build up in blood – results in jaundiced or yellowed skin
o Treatment: crystal-dissolving drugs, ultrasound vibrations (lithotripsy), laser vaporization, or surgery

Question 24

Define the digestive function of the pancreas. What is contained in pancreatic juice? Is it acidic or basic?

Answer 24

o Largely retroperitoneal, deep to the greater curvature of the stomach
 Head is encircled by the duodenum, tail abuts the spleen
o Exocrine Function: production of pancreatic juice – contains enzymes needed to break down all categories of foodstuffs
 Multiple ducts secrete into the duodenum via the main pancreatic duct
o Endocrine Function: secretion of insulin and glucagon by pancreatic islet cells

Question 25

• Be prepared to label the main pancreatic duct, the hepatopancreatic ampulla, and the major duodenal papilla.

Question 26

Make a list of the 4 macromolecules digested by the digestive tract. Next to each macromolecule, list the enzyme most responsible for its digestion.

Answer 26

o Proteases: for proteins; secreted in inactive form to prevent self-digestion
o Amylase: for carbohydrates
o Lipase: for lipids
o Nucleases: for nucleic acids