A&P II Ch. 23 Digestive System

From prof Curtis Moon -Test 3 review

Know what the alimentary canal consists of.

Mouth, pharynx, esophagus, stomach, small and large intestine.

Know what the accessory organs covered are and what their function is

 Teeth, tongue, gallbladder, salivary glands, pancreas, and liver. Teeth equals mastication, Tongue mixes food with saliva and forms bolus. Gallbladder stores bile. Salivary glands secrete saliva that cleanse the mouth, moisten, dissolves food chemicals. Salivary amylase breaks down starch. The liver produces bile, Bile salts emulsify fat, facilitate fat and cholesterol absorption and help solubilize cholesterol. The pancreas exocrine function secrets pancreatic juice, breaking down all categories of food. The endocrine function is the release of insulin and Glucagon. The pancreatic juice is a water solution of enzymes and electrolytes that neutralizes acid chyme.

Understand when something is “internal”.

something is internal when it has crossed the membrane and into the body. It won't have any access to the outside.  

Know the six essential activities of the digestive process

Indigestion, propulsion, mechanical digestion, chemical digestion, absorption, defecation.

Understand what peristalsis is doing and how it is different from segmentation

Peristalsis is smooth muscle of your GI tract will contract and relax alternatively to move food along the tract.

Segmentation is food mixing and slow propulsion. Segments of food move forward and backward, get the digested segment by segment.

Be able to detail mechanical and chemical digestion

Mechanical digestion is chewing(mouth), mixing, churning(stomach), and segmentation(small/large intestine). Chemical digestion is on molecular level, using chemicals and enzymes to breakdown food. Big to small.

Understand the intrinsic and extrinsic controls of the GI tract (CNS vs. Local “gut brain”)

Extrinsic (autonomic, long reflexes) means outside digestive system and is your CNS via spinal cord. Smell, thought of food triggers CNS.

Intrinsic means inside digestive system and doesn't need CNS There is little local centres, gut brain, short reflexes. Example reaction in body like blood sugar. Chemoreceptors, osmoreceptors, mechanoreceptors are involved with local enteric nerve plexus (short reflexes)

Know what mechanoreceptors and chemoreceptors are doing

Activate or inhibit digestive glands by physically chewing, mechanoreceptors. When start chewing, chemo receptors start activating salivary gland.

Know how the peritoneum is covering the organs in the abdominal cavity and how the \n mesenteries are formed from this

Quite large, visceral side covers organs, parietal side hugs body wall. Breaking through peritoneum, you get fistulas. Mesentery is double layer peritoneum. Vascular and nerve supply to viscera. Hold organs and store fat.

Know the basic difference between intraperitoneal organs and retroperitoneal organs.  No need \n to go deeper than what we did in lecture!

Intraperitoneal organs are surrounded by peritoneum. Retroperitoneal organs outside of peritoneum, get absorbed and flows thru.

Know the basics on the splanchnic circulation and know the specific words we covered for \n locations (hepatic, coli, renal, etc.).

Hepatic, liver. Splenic, spleen. Left gastric artery, stomach. These arteries are from the celiac truck. Hepatic portal circulation is when nutrient rich venous blood from viscera goes to liver for metabolic processing and storage.

Know the four tunics of the GI tract (esophagus to anal canal).

Mucosa, submucosa, muscularis externa, serosa.

Mucosa= secrete mucus, absorption of end product of digestion, protect against infection(malt). Submucosa= dense irregular connective tissue with elastic fibers, blood and lymphatic vessels, lymph nodes and nerves. Muscularis externa does peristalsis and segmentation. Serosa has visceral peritoneum, fibrous adventitia in esophagus.

Know what the word enteric means.

Intestines

Understand the two nerve plexuses that  control the GI tract

Submucosal nerve plexus regulates glands and smooth muscle and mucosa, ANS. myenteric nerve plexus control GI track mobility in muscularis externa.

Understand the roles of the structures of the mouth we covered

Mouth has stratified squamous epithelium to withstand roughness, those layers of squamous epithelium let your mouth eat captain crunch. Gums, hard palate, and dorsum of tongue is little bit keratinized for same reason.

Hard palate helps tongue with chewing period. Soft palate closes nasopharynx during swallowing. Tanga grips food when chewing, mixes food with saliva and make bolus.

Understand what the salivary glands are doing for chemical digestion and the general locations \n of these glands

Parotid, submandibular, sublingual clean mouth, moisten/ dissolve food chemicals, makes bolus, salivary amylase breakdown starch.

composition of saliva

Mostly water, hypoosmotic, slightly acidic solution with electrolytes, salivary amylase, proteins: mucin, lysozyme, defensins, IgA.

Metabolic wastes: urea , uric acid

Know the 3 parts of the larynx and where they are located

. Naso, oro, laryngopharynx Allow food to esophagus and air to trachea.

function of the esophagus

Secrete mucus when bolus moves through esophagus

skeletal muscle and smooth muscle are on the esophagus

Superior= skeletal, inferior= smooth.

bolus

Chewed food with saliva after ingested

layers of the esophagus

mucosa, submucosa, muscularis externa, adventitia

phases of swallowing (deglutition

Buccal phase(Bolus goes into oropharynx), pharyngeal esophageal phase (only digestive track opens up), Peristalsis.

Know your sphincters/valves as we travel down the GI tract.

Esophagus to stomach= cardiac sphincter. Stomach to duodenum in small intestine= pyloric sphincter. Small intestine is from pyloric sphincter to ileocecal valve(between ileum & cecum of colon). Bile goes through the cystic duct that fuses with common hepatic duct of liver, this makes the bile duct and splinter which leads to hepatopancreatic splinter.

Know where the mesenteries are connecting to the stomach (greater/lesser omentum).

Lesser omentum= from kidney to lesser curvature. greater omentum= inferior from greater curvature to small intestine.

Know what goblet cells are doing in the stomach

Goblet cells produce alkaline mucus that traps bicarbonate rich fluid beneath it. It neutralizes acid so it doesn't eat away stomach lining. When this is messed up we get ulcers.

Know what pepsinogen is and how its activated (and what its activated to).

Parietal cells secrete HCL and intrinsic factor. chief cells produce pepsinogen. Pepsinogen will react with HCL and make pepsin, a protein degrading enzyme. Pepsinogen is activated by HCL then turned into pepsin. Pepsin is then active and start digesting proteins with HCL.

Know which cell types in the stomach are making what products (pepsinogen, HCl, mucous, \n etc.).

Enteroendocrine cells are under hormonal control. Enteroendocrine cells secrete gastrin, histamine, endorphins, serotonin, cholecystokinin (CCK), and somatostatin into the lamina propria.

Mucus neck cells secrete acid mucus.

Know the glands of the fundus and body of the stomach (slide 20)

Gastric glands of the fundus and body have a variety of secretory cells

Mucous neck cells – secrete acid mucus

Parietal cells – secrete HCl and intrinsic factor

Chief cells – produce pepsinogen

Pepsinogen is activated to pepsin by HCl in the stomach

Enteroendocrine cells – secrete gastrin, histamine, endorphins, serotonin, cholecystokinin (CCK), and somatostatin into the lamina propria

chyme

Partially digested food going through stomach to small intestine through pyloric sphincter.

Know the stimulatory and inhibitory events of digestion

cephalic phase: Smell and thought of food /loss of appetite        

\
gastric phase: food enter stomach. Physical and chemical triggers start this.   Stomach distension activate stretch receptors. Food chemicals (caffeine) and rising pH activate chemoreceptors./ excessive acidity pH

Know what gastritis is and some common things that could cause it (disease, drugs, etc.).

Anything breaches mucosal barrier. Peptic or gastric ulcers erode stomach wall caused by >>*Helicobacter pylori* bacteria cause overall gastritis. If you are susceptible, you're more likely to get it. World is not sterile.

Be able to discuss how ulcers happen and why stress is no longer believed to be a cause of ulcers.

stress is not cause of ulcers but make it worse when excrete HCL. ulcers happen from bacterial infections like *Helicobacter pylori* bacteria, it lives in high acid environment. in the 80s we didn't think anything lived there, treatable with antibiotics.

3 regions of the small intestine

duodenum, jejunum, ileum

Know the valves entering the small intestine and leaving.

Small intestine is from pyloric sphincter to ileocecal valve(between ileum & cecum of colon)

Know how bile and other digestive enzymes from the pancreas enter the duodenum.

The bile duct and main pancreatic duct join the duodenum at the hepatopancreatic ampulla

Be able to distinguish villi, microvilli (brush border) and what they are for in digestion

All increase surface area: Plicae circulares: deep circular folds of the mucosa and submucosa.

Villi – fingerlike extensions of the mucosa      Microvilli – tiny projections of absorptive mucosal cells’ plasma membranes

Be very familiar with the vasculature and lymphatic system in the villus. (slide 34 is good for \n this).

Capillary beds in the villi for absorption. Highly innervated. Lacteal right in the middle of the villi.

Know what intestinal crypts secrete, brunners glands, and what peyers patches do in the small \n intestine (slide 36)

intestinal crypts secrete intestinal juice in response to distension or irritation of the mucosa

Brunner’s glands in the duodenum secrete alkaline mucus to protect. Peyer’s patches are found in the submucosa (MALT)

Know how the liver and gallbladder work together for digestion.

The liver produces bile, a solution that helps you digest fats. Gallbladder. The gallbladder stores bile. As fatty food enter (the duodenum), the gallbladder squeezes bile into the small intestine through the bile ducts.

Know how the liver and pancreas are linked to the duodenum (slide 42)

bile goes through the cystic duct that fuses with common hepatic duct of liver, this makes the bile duct and splinter which leads to hepatopancreatic splinter.

Know the functions of a hepatocyte (they are busy cells...)

Produce bile, process bloodborne nutrients, store fat soluble vitamins, detoxification. The secreted bile goes from hepatocytes to bile ducts in the portal triads.

Know the link between bile and cholesterol

Bile has bile salts that are cholesterol derivatives, they emulsify and facilitate fat, solubilize and absorb cholesterol.

Know what cholecystokinin (CCK) and secretin are doing for digestion (slide 50):

Acidic, fatty chyme causes the duodenum to release: Cholecystokinin (CCK) and secretin into the bloodstream. CCK make gallbladder contract and hepatopancreatic splinter to relax. Then bile enters duodenum.

Know the basics on bile release, don’t go deeper than we did.

Acidic, fatty chime enter duodenum > release of CCK and secretin, they go into bloodstream> bile salts and secretion go through bloodstream and stimulate liver to produce bile> vagal stimulation make weak contraction of gallbladder> CK cause gallbladder to contract and hepatopancreatic splinter to relax, finally bile enter duodenum.

Know how the pancreas has exocrine function and endocrine function

The pancreas exocrine function secrets pancreatic juice, breaking down all categories of food. The endocrine function is the release of insulin and Glucagon.

Know what the pancreatic juices are doing for digestion and what it contains (slide 6)

The pancreatic juice is a water solution of enzymes and electrolytes that neutralizes acid chyme. Has pancreatic enzymes: pancreatic alpha amylase, pancreatic lipase, proteases/peptidase, nucleases.

Understand what causes secretin and CCK to be released

When fatty acidic chime entered duodenum

Understand that the small intestine does the majority of digestion/absorption and how the \n pancreas aids this.

Great absorber, all nutrient absorption. Pancreatic juice starts it off.

Know the basic anatomy of the colon and where the small intestine enters (slide 12)

ileocecal valve(between ileum & cecum of colon)

Know the three unique features of colon listed on slide 13

Teniae coli – long line smooth muscle in its muscularis

Haustra – pocketlike sacs caused by the tone of the teniae coli > give poop shape

Epiploic appendages – fat-filled pouches of visceral peritoneum > fat droplets along line line

Know how the mesentery fits around the colon

Lesser omentum between liver and stomach. Transverse mesocolon under transverse colon. Mesentery attached to small intestine. Sigmoid mesocolon attached to sigmoid colon. stomach to large intestine is greater omentum.

Know the sphincter/valve locations between and after the colon.

Internal anal sphincter has smooth muscle, external has skeletal muscle.

Know the order going from the mouth to the anus

Mouth, esophagus, stomach, small intestine, large intestine, rectum, anus.

Know where hemorrhoids come from (varicosities)

inflammation of superficial venous plexuses in anal canal

Know the basics we covered on bacterial flora (normal flora/human microbiome)

ferment indigestible carbs, release irritating gases and acids (flatus).

what is absorbed/reclaimed by the colon and what nutrients the bacteria can give us:

Vitamins, water, and electrolytes are reclaimed. ). Synthesize B complex vit and K vit.(RENT)

Understand how haustral contractions happen (slide 25):

slow segmenting movements of poop

Understand how defecation happens

distension of rectal walls from feces stimulate contraction of rectal walls and relaxes internal anal splinter. Relaxing external animal splinter is voluntary then poop