Digestive system

Saliva function

Begins breakdown of food Salivary amylase: breakdown carbs Lingual lipase: inactive till enters acidic stomach which then helps digest fats Immune function against microorganisms IgA antibodies, lysozyme, defensins

Pepsin enzymatically digests __________ fat nucleic acids protein carbohydrate

Protein

appendicitis

inflammation of the appendix blockage (often by feces) that traps infectious bacteria in its lumen. Unable to empty its contents, the appendix swells, squeezing off venous drainage, which may lead to low blood flow and tissue death of the appendix.

Stellate macrophages are found in the liver and are responsible for removing bacteria and worn-out cells. True False

True

Peritonitis

inflammation of the peritoneum Imost commonly it results from a burst appendix that sprays bacteria-containing feces all over the peritoneum

Bacteria flora in the large intestine does NOT produce __________. B vitamins CO2 vitamin K intrinsic factor

intrinsic factor

only stomach function essential to life is secretion of?

intrinsic factor

The lamina propria is composed of ________. reticular connective tissue dense irregular connective tissue dense regular connective tissue loose connective tissue

loose connective tissue

Nervous control of gastric secretion is provided by ________. the reticulospinal and vestibulospinal tracts the vagus nerve and enteric plexus somatic neurons in the spinal cord the rubrospinal tracts

the vagus nerve and enteric plexus

serous membrane that covers the external surfaces of most digestive organs is called the __________. parietal peritoneum mesentery visceral peritoneum omentum

visceral peritoneum

appendix

-extension of cecum -contains masses of lymphoid tissue -part of MALT, plays an important role in body immunity -serves as a storehouse of bacteria and recolonizes the gut when needed.

mucosa layer

-innermost layer -Secrete mucus, digestive enzymes, and hormones -Absorption of nutrients mucosa consists of 3 sublayers: (1) epithelium (2) lamina propria: areolar connective tissue, blood capillaries, lymphoid follicles (3) muscularis mucosae: folds to increase surface area Except for that of the mouth, esophagus, and anus where it is stratified squamous, the epithelium of the mucosa is a simple columnar epithelium rich in mucus-secreting cells and absorption.

Regulation of Bile and Pancreatic Secretion

1) CCK released due to fats & protein in chyme Secretin secreted due to acid in chyme 2) In pancreas, CCK stimulates acinar cells to secrete pancreatic juice, while secretin stimulates duct cells to secrete bicarbonate rich pancreatic juice 3) bile salts returning from enterophepatic circulation stimulates bile secretion 4) CCK stimulates gallbladder contraction 5) CCK causes hepatopancreatic sphincter to relax and bile and pancreatic juice enter duodenum

defecation

1) Feces moves into rectum stimulating stretch receptors 2) Receptors transmit signals to spinal cord Spinal reflex initiates and parasympathetic motors fibers stimulate contraction of the rectum and sigmoid colon. Also leads to relaxation to the internal anal sphincter (smooth muscle and this involuntary PNS) Conscious awareness of distention is now present 3) External anal sphincter (skeletal muscle and this voluntary) relaxes and fevers passes through anus

Teeth

2 sets of teeth 1) primary/ permanent teeth: 32 teeth 2) deciduous teeth or baby teeth: 20 teeth

Modifications of the Small Intestine for Absorption

3 structural modifications that amplify its absorptive surface enormously: 1) plicae circularis: circular folds force chyme to spiral through the lumen, slowing its movement and allowing time for full nutrient absorption 2) villi: fingerlike projections that increase surface area. In the core of each villus is a dense capillary bed and a lymphatic capillary called a lacteal. Digested foodstuffs are absorbed through the enterocytes into both the capillary blood and the lacteal. 3) microvilli: (brush border) bear enzymes referred to as brush border enzymes, which complete the digestion of carbohydrates and proteins in the small intestine.

Absorption in the small intestine

90% absorption in villi, through enterocytes (tight junction prevent going between) and then blood capillaries which transport to liver via hepatic portal vein *The exception is some lipid digestion products, which enter the lacteal in the villus to be carried via lymphatic fluid to the blood.

Bile

A substance produced by the liver (hepatocytes) that breaks up fat particles. Once emulsified pancreatic lipases further digests it. COMPOSITION- alkaline Water Electrolytes Bilirubin pigment bile salts derived from cholesterol and help aid emulsification of fats. Bile salts are recycled in the enterohepatic circulation (ileum) and travel back to liver via hepatic portal vein

Control of HCl-secreting parietal cells is stimulated by 3 chemicals

ACh, gastrin, and histamine

Esophagus

As food moves through the laryngopharynx, the epiglottis closes off the larynx and incoming food is routed into the esophagus. esophagus is responsible for peristalsis of food takes a fairly straight course and pierces the diaphragm at the esophageal hiatus to enter the abdomen.

is/are NOT found in pancreatic secretions. Bicarbonate ions Chymotrypsinogen Cholecystokinin (CCK) Procarboxypeptidase

Cholecystokinin (CCK)

gastritis

Damage to the mucosal barrier causing inflammation of the stomach wall Erosion of the stomach wall can promote peptic ulcers

Serosa (visceral peritoneum)

Epithelium and connective tissue In the esophagus, the serosa is replaced by an adventitia

Stomach

Fundus: "storage tank" for ingested food Cardia is entrance pylorus is exit; pyloric sphincter (valve) which controls stomach emptying Mixing chamber Begins digestion of proteins Kill's microorganisms due to acidity Movement of chyme into small intestine

gastroesophageal reflux disease (GERD)

Heartburn first symptom, occurs when stomach acid regurgitates into the esophagus usually from a weak gastroesophageal or cardiac sphincter

of the following is NOT a characteristic of the liver? It stores glucose as glycogen. It has a role in detoxifying the blood. It has three lobes. It is highly regenerative.

It has 3 lobes It has 4 lobes

Large intestines

Its major digestive functions are: -absorb most of the remaining water -normal flora will ferment indigestible carbs and synesthesias vitamins -eliminate them from the body as semisolid feces No villi or enzymes but lots of goblet cells producing mucus

peristalsis vs segmentation

Peristalsis is primarily propulsive; some mixing of food may occur. Segmentation primarily mixes food and breaks it down mechanically; some propulsion may occur.

Which of the following functions is NOT correctly matched with its description? absorption: transport of chemically digested nutrients into the blood or lymph mechanical breakdown: churning movements in the GI tract ingestion: taking food into the digestive tract propulsion: physical breakdown of ingested food in the GI tract

Propulsion is the movement of ingested food through the GI tract.

Digestive Processes in the Stomach

Propulsion. stomach exhibits peristalsis. Mechanical breakdown. The churning action provided by the stomach's smooth muscle during peristalsis causes mechanical breakdown of stomach contents. Digestion. Protein digestion begins in the stomach and is the main type of enzymatic breakdown that occurs there. HCl produced by stomach glands denatures proteins. The most important protein-digesting enzyme produced by the gastric mucosa is pepsin. *Fat digestion occurs primarily in the small intestine Absorption. Not much is absorbed in the stomach, but 2 common substances—alcohol and aspirin—pass easily through the stomach mucosa into the blood.

Pancreas

Secretes pancreatic juice Acini: cells that produce the enzyme component of pancreatic juice. Ducts: transport the secretions of the acinar cells and secrete H2O and bicarbonate into secretion

muscularis externa

Skeletal muscle above esophagus & smooth muscle cells in stomach responsible for segmentation and peristalsis inner circular layer outer longitudinal layer

anal canal

The anal canal has 2 sphincters 1) involuntary internal anal sphincter composed of smooth muscle 2) voluntary external anal sphincter composed of skeletal muscle. The sphincters, which act rather like purse strings to open and close the anus, are ordinarily closed except during defecation.

Bile and Pancreatic Secretion into the Small Intestine

The bile duct, delivering bile from the liver, and the main pancreatic duct, carrying pancreatic juice from the pancreas, unite in the wall of the duodenum. They fuse together at the hepatopancreatic ampulla The ampulla opens into the duodenum via the major duodenal papilla. A smooth muscle valve called the hepatopancreatic sphincter controls the entry of bile and pancreatic juice.

epithelium of large intestine

The wall of the large intestine differs in several ways from that of the small intestine: There are no circular folds, villi, or brush border because most food is absorbed before reaching the large intestine. Its mucosa is thicker, its abundant crypts are deeper, and the crypts contain tremendous numbers of goblet cells. Mucus produced by goblet cells eases the passage of feces and protects the intestinal wall from irritation by acids and gases released by resident bacteria. Like the small intestine, the large intestine mucosa is simple columnar epithelium except in the anal canal. The mucosa of the anal canal, a stratified squamous epithelium

The major role of absorption in the ileum is to reclaim bile salts to be recycled back to the liver. True False

True

increased concentration of HCO3- in blood draining from the stomach is called __________. the enterogastric reflex the alkaline tide the gastric phase the chloride shift

alkaline tide

Submucosa

areolar connective tissue containing a rich supply of blood and lymphatic vessels, lymphoid follicles, and nerve fibers

Swallowing food

buccal phase- voluntary Food is swallowed in oral cavity and broken down and moved to pharynx pharyngeal-esophageal phase- involuntary Swallowing becomes a reflex when the bolus stimulates receptors in medulla epiglottis and uvula to cover larynx and Nasopharynx so it can enter esophagus this is primarily under control of vagus nerve. Upper Esophageal sphincter relaxes for bolus to travel down Peristalsis pushes bolus down Gastroesophageal sphincter relaxes to allow bolus to enter stomach and the closes so acid doesn't backflow

Chemical digestion reduces large complex molecules to simpler compounds by the process of ________. mastication anabolism catabolism excretion

catabolism

cephalic, gastric, and intestinal phases

cephalic -reflex, phase of gastric secretion occurs before food enters the stomach. This phase is triggered by the aroma, taste, sight, or thought of food -triggers act via the vagus nerve to stimulate gastric glands, getting the stomach ready for its digestive chore. gastric phase food reaches the stomach -Stomach distension activates stretch receptors and initiates both short and long reflexes -Chemical stimuli provided by partially digested proteins, and rising pH activate chemoreceptors to release gastrin and HCL intestinal phase Triggered by ph changed and stretching of duodenum begins with a brief stimulatory (as partially digested food fills the duodenum) component followed by inhibition (as intestines start to fill) Controls rate of stomach emptying

Which of the following is NOT a function of the stomach? mechanical breakdown of the bolus into chyme chemical digestion of carbohydrates absorption of a few fat-soluble substances temporary holding area for food until it can be moved to the duodenum

chemical digestion of carbohydrates The stomach does not produce enzymes to digest carbohydrates. Carbohydrates are chemically digested by salivary amylase in the mouth and by pancreatic amylase in the small intestine.

An obstruction by a gallstone is least likely to occur in the ______. common hepatic duct bile duct cystic duct lumen of the hepatopancreatic sphincter

common hepatic duct

The __________ circulation collects nutrient-rich venous blood draining from the digestive viscera. splanchnic pulmonary hepatic portal enterohepatic

hepatic portal

Which of the following is NOT a function of cholecystokinin (CCK)? open hepatopancreatic sphincter stimulate gallbladder to release bile increase production of stomach acid increase production of pancreatic juice

increase production of stomach acid

Hepatitus

inflammation of the liver

Digestion and absorption of which of the following would be affected the most if the liver were severely damaged? carbohydrates proteins lipids starches

lipids

Bile is secreted by the __________ under hormonal influence of __________. pancreas; secretin liver; secretin gallbladder; gastrin small intestine; CCK

liver; secretin Secretion of bile from the liver is stimulated hormonally by secretin. Bile salts themselves provide the major stimulus for enhanced bile secretion. After a fatty meal, when the enterohepatic circulation is returning large amounts of bile salts to the liver, its output of bile rises dramatically.

Peyer's patches

located in the lamina propria but occasionally protrude into the submucosa below Their increasing abundance toward the distal end of the small intestine reflects the fact that this region contains huge numbers of bacteria that must be prevented from entering the bloodstream

Carbohydrates are digested into __________. monosaccharides glycerol amino acids nucleotides

monosaccharides

esophagus wall has all 4 of the basic alimentary canal layers

mucosa Upper: nonkeratinized stratified squamous epithelium Lower: esophagus-stomach junction, simple columnar epithelium submucosa contains mucus-secreting esophageal glands aids food passage muscularis externa upper: skeletal muscle lower: smooth muscle adventitia Instead of a serosa, the esophagus has a adventitia composed entirely of connective tissue

From the esophagus to the anal canal, the walls of the alimentary canal have the same 4 basic layers

mucosa submucosa muscularis externa serosa

What is a major function of pancreatic juice?

neutralizing chyme entering the small intestine from the stomach Pancreatic juice contains bicarbonate that can neutralize the pH of acidic chyme coming from the stomach.

nucleic acids fatty acids and monoglycerides amino acids monosaccharides

nucleic acids-> nucleotides fatty acids and monoglycerides-> lipase fat amino acids-> proteins monosaccharides-> carbohydrates

salivary glands

parotid glands sublingual glands submandibular glands The salivary glands are composed of two types of secretory cells: 1) Serous cells produce watery secretion containing enzymes, ions, and a tiny bit of mucin 2) Mucous cells produce mucus

mucosal barrier

protective barrier that prevents acidic gastric juice (HCL) from destroying the stomach itself 3 factors create this barrier: -bicarbonate-rich mucus builds up on the stomach wall. -epithelial cells of the mucosa are joined together by tight junctions that prevent gastric juice from leaking into underlying tissue layers -Damaged epithelial mucosal cells are shed and quickly replaced every three to six days

The uvula is an extension of the __________.

soft palate

Gallbladder

stores bile Its muscular wall contracts to expel bile into the cystic duct. and then into bile duct

Which of the following is an essential role played by large intestine bacteria? synthesize vitamins C and D absorb bilirubin produce gas synthesis of vitamin K

synthesis of vitamin K

papillae

taste buds

accessory digestive organs

teeth, tongue, gallbladder, salivary glands, liver, and pancreas.

Which of the following enzymes would be most active in the presence of high concentrations of protein fragments? lipase trypsin amylase dextrinase

trypsin

Bile duct blockage

Bile is the major vehicle for excreting cholesterol from the body, and bile salts keep the cholesterol dissolved within bile. Too much cholesterol or too few bile salts allows the cholesterol to crystallize, forming gallstones. Gallstones can obstruct the flow of bile from the gallbladder, a condition called cholelithiasis Bile duct blockage prevents both bile salts and bile pigments from entering the intestine. As a result, yellow bile pigments accumulate in blood and eventually are deposited in the skin, causing it to become yellow, or jaundiced.

regulation of gastric secretion

Both neural and hormonal mechanisms control gastric secretion. Neural controls consist of both long (vagus nerve-mediated) and short (local enteric) nerve reflexes. In each case, acetylcholine (ACh) is released, stimulating the output of gastric juice. Hormonal control of gastric secretion is largely the province of gastrin.

Digestion

Breakdown of food substances into simpler forms that can be absorbed and used Most digestion is done in the small intestine. Pancreatic enzymes break large chemicals into smaller pieces that are, in turn, broken down into individual components by the intestinal brush border enzymes. Alkaline pancreatic juice neutralizes the acidic chyme that enters the small intestine from the stomach. This provides the proper environment for operation of the enzymes. Both pancreatic juice and bile are necessary for fat breakdown.

Neural Innervation of the GI Tract

ENTERIC- nerve supply of esophagus to anus composed of 2 major intrinsic/ enteric nerve plexuses: submucosal nerve plexuses- control of secretion in submucosal layer myenteric nerve plexuses- GI motility in between muscular layers of muscularis externa Short reflexes are mediated entirely by enteric nervous system plexuses in response to stimuli within the GI tract. Long reflexes extrinsic (autonomic nervous system) regulates enteric nerve plexus. It receives sympathetic and parasympathetic communications. Generally speaking, parasympathetic inputs enhance digestive activity and sympathetic inpulses inhibit them.

5 major types of cells are found in the villi and crypts

Enterocytes: simple columnar absorptive cells with microvilli primary responsibility for absorbing nutrients and electrolytes in the villi. In the crypts, enterocytes are primarily secretory cells that secrete intestinal juice Goblet cells Enteroendocrine cells: secretin and cholecystokinin Paneth cells: fortify the small intestine's defenses by releasing antimicrobial agents such as defensins and lysozyme which destroy certain bacteria Stem cells

The pharyngeal-esophageal phase of swallowing is involuntary and is controlled by the swallowing center in the thalamus and lower pons. True False

False, medulla

The submucosal nerve plexus provides the major nerve supply to the GI tract wall and controls GI motility. True False

False, myenteric nerve plexus Submucosa plexus provides secretion

mesentery

Folds of peritoneum, double layer of peritoneum—a sheet of two serous membranes fused back to back Mesenteries have the following functions: -They provide routes for blood vessels, lymphatics, and nerves to reach the digestive viscera. -They hold organs in place. -They store fat.

Cirrhosis

Last stage of progressive chronic inflammation of the liver. It typically results from severe chronic hepatitis. While damaged hepatocytes can regenerate, the liver's scar tissue regenerates faster. Liver activity is depressed and the liver becomes fibrous with scar tissue.

Activation of pancreatic proteases

Like pepsin of the stomach, pancreatic proteases are produced and released in inactive forms that are activated in the duodenum, where they do their work. This protects the pancreas from digesting itself. The pancreas secretes 3 inactive proteases into the small intestine. Brush border enteropeptidase activates and converts them: trypsinogen -> active trypsin trypsin -> procarboxypeptidase-> carboxypeptidase trypsin -> chymotrypsinogen-> chymotrypsin

Digestion in stomach

Like the esophagus, the stomach exhibits peristalsis which move from the fundus to the pylorus where it is most vigorous. The pyloric part of the stomach, acts as a dynamic filter that allows only small amounts of chyme to pass through the pyloric valve into small intestines Retropulsion pushes most of the food back into the stomach and closes pyloric valve A carbohydrate-rich meal moves through the duodenum rapidly, but fats are digested more slowly.

Small intestines

Major digestive organ (with the help of bile and pancreatic enzymes) virtually all nutrient absorption occurs here Segmentation and peristalsis: ensures chyme is thoroughly mixed with bile and pancreatic and intestinal juices

layers of the stomach wall

Mucosa rugae folds when empty which give it more surface area. When stomach is full the rugae is flat. Gastric pits are throughout the interior layer of the stomach, extend exteriorly and lined with mucous cells. The pits connect to the deeper gastric glands, which are lined with mucous neck cells, parietal cells, chief cells and enteroendocrine cells. Submucosa Muscularis externa: 3 layers instead of 2 oblique layer, circular layer, and longitudinal layer Serosa

alimentary canal

Organs of the alimentary canal are the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

Secretions of the small intestines- Intestinal juice

Slightly alkaline Secretin -hormone stimulates by acidic chyme -Inhibits gastric gland secretion and gastric motility -stimulates duct cell of pancreas to release bicarbonate ions and water into pancreatic juice -stimulates flow of bile from liver to gallbladder CCK -hormone stimulated by fatty chyme -Inhibits gastric glands -stimulates pancreas to release enzymes in pancreatic juice -Stimulates gallbladder to contract releasing bile -Relaxes hepatopancreatic sphincter Gastrin Stimulates stomach secretions Somatostatin Inhibits stomach secretion BRUSH BORDER ENZYMES Peptidase -breaks down proteins Intestinal lipase Breaks down fats Enterokinase Converts trypsinigen to trypsin

Most digestion occurs in the small intestine. True False

True

Someone on a fat-free diet would NOT efficiently absorb vitamin D from the diet. True False

True

anatomy of large intestine

cecum-> ascending colon-> transverse colon-> descending colon-> sigmoid colon-> rectum Ileocecal valve: regulates material entering cecum Band of smooth muscle called teniae coli which is shorter than large ins testing which causes pouches called haustra

pancreatic juice

consists mainly of water, enzymes and electrolytes and bicarbonate ions The alkaline (high pH) of pancreatic fluid helps neutralize acidic chyme entering the duodenum The pancreatic enzymes include: Proteases (for proteins) trypsinogen procarboxypeptidase chymotrypsinogen Amylase (for starch) Lipases (for fats) Nucleases (for nucleic acids)

gastric pits of stomach

produce gastric juice Mucus neck cells and goblets cells at cardia of stomach that protects lining parietal cells: secrete HCL and intrinsic factor (B12) Chief cells: secrete inactive pepsinogen. HCL converts it to pepsin Enteroendocrine cells: histamine: stimulates release of HCL serotonin: increases muscle contraction somatostatin: inhibits gastric secretions, bile release and contractions gastrin: stimulate the release of HCL in parietal cells and increase gastric emptying

liver

producing bile for export to the duodenum The liver consists of hexagonal lobules Each lobule consists of plates of hepatocytes that produce the bile, which is then sent to bile canaliculi between the hepatocytes and empties into bile duct The plates are separated by sinusoids, or channels, that lead from branches of the portal veins on the outside of the lobule to the central vein at the center of the lobule. They drain blood and contain stellate macrophages that remove debris from the blood. At each of the 6 corners of a lobule is a portal triad with 3 basic structures: 1) hepatic artery (supplying oxygen-rich arterial blood to the liver) 2) hepatic portal vein (carrying venous blood laden with nutrients from the digestive viscera) 3) bile duct

peritoneum

visceral peritoneum covers the external surfaces of most digestive organs parietal peritoneum that lines the body wall Between the two peritoneums is the peritoneal cavity, space containing a slippery fluid secreted by the serous membranes. The serous fluid allows the mobile digestive organs to glide easily across one another and along the body wall as they carry out their activities.

Peristaltic waves are ________.

waves of muscular contractions that propel contents from one point to another