23) digestive system Flashcards
1-27 quiz, 28-68 lecture notes
the part of the large intestine that stores feces before exiting the body
rectum
part of the large intestine that is separated from the ilium via a sphincter
cecum
prevents food from moving up into the nasal cavity when swallowing
uvula
location where the majority of water reabsorption occurs
large intestine
tube that moves both air and food
pharynx
the organ that secretes intrinsic factor, which is necessary for Vitamin B absorption
stomach
organ that connects the mouth to the stomach
esophagus
prevents food from moving down into the airway and is attached to the larynx
epiglottis
lots of brush border microvilli for nutrient absorption
jejunum
location of the small intestine where pancreatic juice is released into the lumen and the majority of chemical digestion takes place
duodenum
responsible for producing bile
liver
the organ responsible for ingestion and mastication
mouth
organ that produces both bicarbonate ions and an assortment of enzymes
pancreas
secretes bile in response to CCK
gallbladder
another name for the regions of the large intestine
colon
digests carbohydrates in the mouth
salivary amylase
digests proteins
protease
secreted by the pancreas to neutralize chyme
bicarbonate ions
digests carbohydrates in the small intestine
pancreatic amylase
secreted by parietal cells of the gastric glands and is required for activation of pepsinogen
hydrochloric acid (HCl)
enzyme that digests proteins in the stomach
pepsin
the inactive form of carboxypeptidase
procarboxypeptidase
secreted by chief cells to digest proteins
pepsinogen
emulsifies fats and required for proper absorption of chylomicrons
bile
enzymes that digest DNA and RNA
nuclease
the inactive form of trypsin
trypsinogen
enzyme that digests fats, and is secreted by three organs
lipase
digestive system
place where complex foods are broken down into small molecules that can be absorbed and used by cells
phases of digestion
mechanical: food chewed and churned by muscular movmeent by alimentary canal wall
chemical: digestive enzymes, HCl breaks food down further
alimentary canal
*mouth, pharynx, esophagus, stomach, small and large intestine
*approx. 8 meters long
accessory organs
salivary glands, liver, gall bladder, pancreas
structures of alimentary canal wall
*mucosa (innermost)- absorption and secretion, may contain glands that secrete digestive enzymes and mucus
*submucosa- many blood vessels, lymphatic vessels, nerves
*muscularis- 2 smooth muscle layers: circular layer- inner coat, encircle tube, contract=diameter decreases// longitudinal layer- outer coat, contract=tubes shorten
*serosa (outermost)- visceral peritoneum, secretes serous fluid
movement in alimentary canal
*mixing movement- moves materials in many directions, segmentation-movement that aids in mixing by contraction & relaxation of smooth muscle
*propelling movement- moves materials in many directions, peristalsis- smooth muscles work together, producing wave like contraction to propel
mouth structures (pt 1)
*lips & cheeks- keeps food between teeth for chewing, lined with mucous glands
*hard palate- bony membrane covered roof of chewing area
*soft palate- membrane extends from hard to soft plate tonsils
*uvula- knob at end of soft palate (keeps food out of nasal cavity
*tongue- skeletal muscle, covered with mucous membrane, anchored to hyoid bone, mixes food with saliva, propels to pharynx
mouth structures (pt 2)
*teeth-deciduous (1st set) 20 total, 10 top, 10 bottom
*permanent- (2nd set) 32 total, 16 top, 16 bottom
*incisors- front, sharp edged (cut or nip food)
*canine (cuspids)- cone shaped (grasp and tear)
*premolars (bicuspids)- semi flat (slice and grind)
*molars- flattened (grind)
structure of teeth
*crown-covered in enamel
*dentin- living tissue that is similar to bone only harder
*pulp cavity- hollow cavity in middle of tooth, contains blood vessels, nerves and connective tissue
*root- holds tooth in sockets of jawbone by fibrous periodontal ligaments covered by cementum
salivary glands
*parotid gland- largest, front of ears, secrete saliva rich in amylase and serous fluid
*submandibular gland- in angles of lower jaw, serous fluid and mucus secreted
*sublingual gland- under tongue, mucus secreted
pharynx
*nasopharynx
*oropharynx
*laryngopharynx
*walls of pharynx contain fibers in circular and longitudinal groups
esophagus
*passes through mediastinum and penetrates the diaphragm
*provides passageway for food from pharynx to stomach
*circular muscle fivers at distal end of esophagus, known as the lower esophageal sphincter, prevents regurgitation of food from the stomach
swallowing mechanism (3 stages)
*food is mixed with saliva and forced into the pharynx
*involuntary reflex actions move food into esophagus
* peristalsis transports food to the stomach
**momentarily inhibits breathing
stomach
*located upper part of abdominal cavity, below diaphragm
*receives food from esophagus, mixes with gastric juices, initiates digestion of proteins
*carries on limited absorption, moves food into small intestine
*lining is thick, wrinkled membrane, holds gastric glands
stomach structures (4 regions)
*cardia- small region near the esophageal opening
*fundus- ballooned superior most area
*body- main part of the stomach
*pyloric- funnel shaped area that becomes pyloric canal before entering small intestine
gastric secretions
*mucous neck cells- secretes mucus
*chief cells- secrete digestive enzymes (e.g.pepsin)
*parietal cells- secret hydrochloric acid (HCl) and intrinsic factor (aids in absorption of vitamin B12)
**gastirc juice- combination of mucus, pepsin, lipase, HCl and intrinsic factor
gastric absorption
*stomach not well adapted to absorb digestive products
*stomach absorbs some water, certain salts, certain lipid-soluble drugs and alcohol
mixing and emptying action of stomach
*as stomach fills, walls stretch, mixes fluid, paste of food and gastric juice known as Chyme
*peristaltic wave move chyme into pyloric region
*muscle wall pyloric region regulates chyme movement into the small intestine
*rate of emptying depends on fluidity of chyme and food present >fats, proteins, carbohydrates
liver structures
**largest gland of body, below diaphragm RUQ
*right lobe- largest
*left lobe- smallest
*quadrate lobe- minor lobe near gallbladder
*caudate lobe- minor lobe near inferior vena cava
liver functions
*receives double supply of blood
*oxygen-poor blood from digestive trach>liver thru hepatic portal vein> mixes with oxygen-rich blood from hepatic artery>filters through hepatic sinusoids
*hepatocytes adjust nutrient concentrations, as nutrients from digestive trach flow
*bile produced by hepatocytes leaves liver> bile duct
*blood drains>central vein>primary hepatic vein>heart
role of liver
*carbohydrates: keep blood glucose concentration steady, high-converts glucose to glycogen, low- converts glycogen to glucose
*lipids: oxidizes fatty acids, synthesizes lipoproteins, phopholipids, cholesterol, converts excessive carbs to proteins and fats
*proteins: de-amination of amino acids, formation of urea, synthesizes blood proteins
*stores glycogen, vitamins A, D, B12, Iron
*phagocytosis of damaged red blood cells & foreign substances
*detoxification: alcohol converted into urea
*secretion: digestion is the secretion of bile
*bile: yellow-green, contains water, salts, pigment, cholesterol and electrolytes, bile salts emulsify fats.
gall bladder
*pear-shaped sac located in depression on inferior surface of liver, stores bile
*bile>liver thru> common hepatic duct>common bile duct>hepatopancreatic sphincter (which controls secretions)>back up to gallbladder
pancreas
*acts as an exocrine gland producing digestive enzymes called pancreatic juice
*acts as an endocrine gland producing hormones
structures of pancreas
*extends horizontally across posterior abdominal wall
*acinar cells- release pancreatic juices>ducts >pancreatic duct>bile duct>duodenum
*hepatopancreatic sphincter regulates pancreatic juice into the small intestine
pancreatic juices
*contains enzymes that split organic molecules
*amylase- splits glycogen into disaccharides
*lipase- break down triglycerides into fatty acids and monoglycerides
*proteolytic enzyme- trypsin, chymotrypsin, and carboxypeptidase break down proteins
*nuclease- break down of nucleic acids
*juices high in bicarbonate- neutralize acidic chyme from stomach
regulation of bile and pancreatic juice
*cholecystokinin (CCK) & secretin secreted by duodenal cells> bloodstream, stimulated by acidic chyme
*CCK & secretin enter circulation and cause 4 different events.
CCK and secretin cause:
*pancreatic secretions- CCK induces secretion of enzymes rich in pancreatic juices, secretin causes secretion of bicarb into pancreatic juice
*bile secretions by liver- bile salts returning from enterohepatic circulation stimulate bile secretion, secretin is a minor stimulus
*gallbladder contraction- CCK causes gallbladder contraction, vagus nerve also causes gallbladder contraction
*hepatopancreatic sphincter relaxation- CCK causes sphincter to relax, bile and pancreatic juice enter duodenum
small intestine
*most important absorbing organ in alimentary canal, between pyloric valve and ileocecal valve
*3 sections of small intestine: duodenum, jejunum, Ileum
duodenum
25cm long, C-shaped, posterior to parietal peritoneum
jejunum
*proximal two-fifths
*greater in diameter, thicker walls, and more vascular
*free from the peritoneal cavity
Ileum
*distal three-fifths
*has more lymph nodes and higher bacteria population
*free from the peritoneal cavity
small intestine structures
*intestinal Villi- tiny projections of mucous membrane, increase surface area greatly, numerous in duodenum and top of jejunum, absorb products of digestion
*intestinal glands- between villi, extend downward into mucous membrane
secretions of small intestine
*mucus, watery, neutral fluid from intestinal gland
*digestive enzymes- embedded in the membranes of epithelial cells, break down food for absorption
**peptidase split peptides, amylase split disaccharides, *lipase splits fatty acids and glycerol
absorption in the small intestine
*carbohydrates- digestion begins in mouth w/ salivary amylase, broke down to monosaccharides, absorbed by villi by active transport or facilitated diffusion
*proteins- begins in stomach with pepsin, broke into amino acids, absorbed by active transport
*fats- break down in small intestine to glycerol and fatty acids, diffuse into epithelial cells of villi
*absorbs water via osmosis and electrolytes via diffusion and active transport
movement of small intestine
*weak peristalsis moves chyme a short distance, segmentation, cuts chyme into small segments
*Ileocecal sphincter controls movement of intestinal contents from small intestine into the large intestine
large intestine
*begins lower right side of abdominal cavity, reabsorbs water, electrolytes from chyme, forms and stores feces
*7cm diameter, 1.5meters long
parts of large intestine
*cecum- pouch like structure that hangs below ileocecal joint
*appendix- projects downward, contains lymphatic tissue, promotes healthy bacteria
*colon- ascending-heads up from cecum, transverse, turns left, descending turns down, sigmoid-s shaped
*rectum- attach to sacrum
*anal canal- last 2.5-4cm of large intestine
large intestine structures
*similar to small intestine layers
*lacks villi
*longitudinal muscles, 3 distinct bands, length of colon
*creates series of pouches called haustra
* collection of fat in the serosa on its outer surface
function of large intestine
*little to no digestive functions
*absorbs water and electrolytes
*secrets mucus
*houses intestinal flora- bacteria that inhabits large intestine, break down some molecules that escape digestion
*forms feces & carries out defecation
movement of large intestine
*slower and less frequent than small intestine
*mixing and peristalsis movement
*mass movements usually follow meals
