CH 23 Digestive System Physiology Questions

being overweight or obese sitting upright after a meal * snacking near bedtime eating fatty or spicy foods

dysphagia hiatal hernia* dyspepsia esophageal varices

the thought of food fear* nausea a lemon

fear,sleep, fatigue, and dehydration

parietal G cells paracrine (also known as enteroendocrine cells) chief*

islet of Langerhans cells acinar cells* duct cells -in response to a high fat and protein meal, CCK would be stimulated and in turn would stimulate an enzyme-rich secretion from the pancreas.

secretin* GIP (gastric inhibitory peptide) gastrin CCK (cholecystokinin) - secretin stimulates the duct cells in the pancreas and liver to secrete a bicarbonate-rich solution that will bind hydrogen ions and increase the pH.

digestive enzymes such as CCK and secretin intrinsic factor bicarbonate- and potassium-rich mucus* bile -an alkaline mucus secretion of bicarbonate and potassium protects the large intestinal wall from acids produced by resident bacteria.

intestinal phase* gastric phase cephalic phase -food in the intestines initiates a reflex that stimulates secretions of bicarbonate, digestive enzymes, and bile.

sympathetic & parasympathetic preganglionic fibers parasympathetic postganglionic fibers interneurons of the enteric nervous system sympathetic postganglionic fibers*

substance P ACh (acetylcholine) norepinephrine VIP (vasoactive intestinal peptide)* -both VIP and NO (nitric oxide) are inhibitory to smooth muscle.

motilin CCK (cholecystokinin)* gastrin GIP (gastric inhibitory peptide)

GIP (gastric inhibitory peptide) motilin gastrin secretin*

ingestion digestion segmentation* mechanical breakdown

detection of nutrients in the esophagus constriction of the upper esophageal sphincter pH changes in the esophagus peristalsis in the esophagus*

emulsifying fats by breaking them into smaller pieces acidifying the contents of the stomach acidifying the contents of the small intestine *neutralizing chyme entering the small intestine from the stomach -Pancreatic juice contains bicarbonate (as baking soda does) that can neutralize the pH of acidic chyme coming from the stomach.

*liver; secretin pancreas; secretin gallbladder; CCK small intestine; CCK

nutrient enzymes insulin *bile bicarbonate - bile is secreted by the liver

absorptive cells Paneth cells *goblet cells enteroendocrine cells

*a lymphatic vessel designed to help introduce fats to the blood a deep pocket in the intestinal wall where endocrine and antimicrobial cells are located special capillaries in the villi designed for absorbing food effectively a projection of the small intestine wall designed to increase surface area -Lacteals are lymphatic vessels located in the intestinal villi. Their ability to accept large materials makes them helpful in transporting large fat particles (called chylomicrons) into the lymph and eventually the bloodstream.

stomach *jejunum large intestine duodenum

mechanical breakdown of food nutrient absorption primary digestion of food *water absorption and feces elimination

sinusoidal *fenestrated continuous lacteals

*production of intrinsic factor production of VIP production of hydrochloric acid production of chyme

large intestine stomach *small intestine liver

*mechanical digestion deglutition defecation absorption

mouth large intestine pancreas *stomach

*amylases trypsin nuclease proteases

in the form of micelles * in the form of fatty acids and glycerol in the form of chylomicrons in the form of glycerol

*B complex and D vitamins vitamins A and E vitamins C and D B complex and C vitamins

reflux gastric phase *intestinal cephalic

*duodenum ileum colon jejunum

absorption of water absorption of electrolytes production of intrinsic factor *absorption of vitamins

mechanical breakdown: churning movements in the GI tracts absorption: intake of chemically processed nutrients ingestion: intake of food nutrients *propulsion: physical breakdown of ingested food in the GI tract

*The stomach releases enzymes to digest carbohydrates. The stomach mucosa is folded into rugae. The stomach has three layers of muscle in the muscularis tunic. The stomach produces a double-layered coat of alkaline mucus

True Either distention of the pylorus or partially digested nutrients in the pylorus triggers the intestinal phase of stomach digestion.

*protease: lipid digestion nuclease: DNA and RNA digestion amylase: carbohydrate digestion lipase: fat digestion

nucleotides *monosaccharides amino acids glycerol

submucosa mucosa serosa muscularis

false -Bacteria that reside in the large intestine make B complex vitamins and vitamin K. Enteric bacteria also form gases such as CO2, methane, H2, and N2 as byproducts of metabolizing nondigested starches such as cellulose.

segmentation mastication *peristalsis churning - Peristalsis is a physical process used for propulsion, or movement, through the GI tract.

T Chief cells do secrete pepsinogen, but the result is unrelated to acidity. When pepsinogen is activated by HCl secreted by the parietal cells, it is converted into pepsin, which is an enzyme that acts on proteins.

*rugae circular folds villi microvilli -Rugae are a structural modification that allow expansion of the stomach wall.

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Irritable bowel syndrome *Constipation Colitis Diarrhea

secretin cholecystokinin (CCK) *procarboxypeptidase bile

*conscious neural control Digestive effectors are smooth muscle and glands. Short reflexes act locally in the GI tract. pH, stretch, and osmolarity are some of the inputs that can initiate digestive responses.

constriction of the upper esophageal sphincter detection of nutrients in the esophagus pH changes in the esophagus *peristalsis in the esophagus

Failure to digest fat

Duodenum

secretin

in order to prevent it from digesting the cells that produce it

the highly acidic conditions of the stomach created from the release of hydrochloric acid

ingestion and defecation

mucus and pepsinogen

gastrin, mucus , pepsinogen (mucus cells, chief cells, g cells)

secretin

digestion and protection

bicarbonate enzymes

hepatopancreatic sphincter

digestive enzymes

primarily by lipase in small intestine

failure to digest fat

acid, intrinsic factor (parietal cells) histamine (paracrine cells) pepsinogen (chief cells)

neutralize acidic chyme in duodenum

production of bile

the bile is redirected to the gallbladder to be stored and concentrated

bicarbonate organic compounds

digestion and absorption of fat

digestion from acid and proteases

protection

cephalic gastric intestinal

cephalic phase

gastric phase

intestinal phase

digest and absorb

ACh serotonin vasoactive intestinal peptide (VIP) nitric oxide (NO) somatostatin (SST)

bile salts emulsify fats

secretin

GI hormone,

single cells in gastrointestinal mucosa

gastrin CCK secretin

portal blood , are transported to the liver before the heart

inhibits salivation and results in dry mouth

Excess food/drink Extreme obesity Pregnancy Running

esophageal ulcers cancer

Buccal Pharyngeal esophageal phase

pernicious anemia

in stomach

Protects from harsh digestive conditions Thick layer of bicarbonate rich mucus Tight junctions between epithelial cells Prevent digestive juice form seeping under tissue Damaged epithelial cells quickly replaced by division of stem cells Surface cells replaced every 3-6 days

reflex phase, Triggered by aroma, taste, sight, thought of food

food is already inside body stimulated by : dissensions,peptides, low acidity and gastrin

stimulatory, partially digested food enters the small intestine

antacids H2 receptor antagonist Proton pump inhibitors PPI's

Ingestion Mechanical breakdown Propulsion Digestion salivary amylase lingual lipase No absorption, except few drugs

T also: when sympathetic activity goes down contractile force and rate of stomach emptying increase

Steps: 1. Buccal phase o upper esophageal sphincter is contracted o tongue presses against hard plate and pushes bolus into oropharynx 2. Pharyngeal- esophageal phase o Uvula and larynx rise to prevent food from entering respiratory passageways o Tongue blocks off mouth o Upper esophageal sphincter relaxes, food enters esophagus 3. Pharynx constrictor muscles o Contract forcing food into esophagus o Upper esophageal sphincter contracts (closes) after food enters 4. Peristalsis o Moves food through esophagus to stomach 5. Gastro esophageal Sphincter o Gastroesophageal sphincter surrounding cardial orifice opens o Food enters stomach

vomiting

Caused by extreme stretching, intestinal irritants, bacterial toxins, excessive alcohol, spicy food, certain drugs Medulla oblongata receptors have trigger zones when trigger zones are activated vomiting is induced

Major organ of digestion and absorption

Duodenum Jejunum Ileum

bile production

Bile

Facilitated diffusion of Cl- 1. CO2 + H2O = H2CO3 carbonic acid 2. Carbonic acid dissociates into a. H+ b. HCO3- (bicarbonate) 3. H+ is pumped back into the stomach a. By primary active transport 4. K+ is pumped into parietal cells

chemical stimuli from partially digested proteins, caffeine, and rising pH

1. Propulsion: peristaltic waves move from fundus toward pylorus 2. Grinding: most vigorous peristalsis and mixing action occur close to pylorus 3. Retropulsion: pylorus end of stomach= pump that delivers small amounts of chyme into duodenum. At the same time forcing most of its contents backward into stomach

If pyloric valve doesn't function properly a lot of acidic chyme can be dumped in duodenum resulting in duodenal ulcers

parietal cells

negative feedback mechanism, somatostatin release from H+

highly acidic lower pH than 2

T

in parietal cells 1. CO2 +H2O combine and form H2CO3 (carbonic acid) 2. carbonic acid dissociates into H+ and HCO3- (bicarbonate) 3. H= is pumped back into the stomach via primary active transport 4.K+ is pumped into parietal cells

causes gallbladder to contract hepatopancreatic sphincter to relax allowing bile to enter duodenum

to produce bicarbonate

Chyme from stomach contains: o Partially digested carbs and proteins o Undigested fats 3-6 hours in small intestine o Most water is absorbed o All nutrients absorbed No role in ingestion or defecation

peristalsis

passively

when normal intestinal water absorption's disrupted the water remains in lumen

in the small intestine

duodenum

1. food or cephalic reflexes initiate gastric secretion how? receptors in the gastric mucosa trigger G cells to produce gastrin 2. gastrin in turn stimulates acid secretion by direct action on parietal cells to secrete HCl or indirectly through histamine 3. Acid secretion stimulates short reflex secretion of pepsinogen from chief cells 4. when H+ increases somatostatin is released = negative feedback mechanism to inhibit G cells and parietal cells from producing gastric acid, gastrin and pepsinogen

regulated by vitamin D and PTH

by active transport

diffuses in response to osmotic gradients