Module 17: The Digestive System Flashcards
enzymes are used to
break down carbs into simple sugars, proteins into amino acids and lipids into glycerol and fatty acids
3 functions of digestive system
digestion
absorption
elimination
Process of digestive system
Ingestion propulsions (swallowing) Digestion (mechanical and chemical) Absorption Elimination (defecation)
Organs of digestive tract
aka alimentary canal or GI tracts
mouth pharynx esophagus stomach small and large intestine
accessory organs of digestive system
teeth tongue salivary glands liver gallbladder pancreas
serous Peritoneum
simple squamous epithelium that covers connective tissue
found in abdominopelvic cavity below the diaphragm
Above diaphragm = adventitia
Visceral peritoneum
covers external surfaces of digestive organs
Parietal peritoneum
lines walls of abdominal cavity
Extensions (folds) of peritoneum
mesentery (small intestine) mesocolon (colon) falciform ligament (Liver) greater omentum (fatty apron that hangs over stomach and covers colon and small intestine) lesser omentum (suspends the stomach and duodenum from liver)
Functions of peritoneum
holds organs in place
conducts nerves, blood and lymphatic vessels
some fatty parts protect organs
Location of peritoneal cavity
space between the visceral peritoneum and the parietal peritoneum
Function of peritoneal cavity
serous fluid provides lubrication for 2 layers
preventing friction
Layers of the alimentary canal
walls of alimentary canal from the esophagus to the anus
inner to outer layer: mucosa, submucosa, muscularis, serosa
Function of mucosa
direct contact with contents of tract protection secretion of enzymes, mucus and hormones absorption of nutrients pulls mucous membrane of small intestine into folds (plicae circularis)
function of Submucosa
connective tissue that binds the mucosa to the muscularis
contains blood and lymphatic vessels, lymph nodules and nerve fibers
Function of muscularis
consists of inner circular smooth muscle and outer longitudinal smooth muscle
Exception: stomach has extra layer of smooth muscle (oblique)
Mixes (segmentation) and propels (peristalsis) food and water through digestive tract
Circular layer of smooth muscle forms valves/sphincters
Function of serosa
visceral periotneum
Consists of areolar connective tissue covered with simple squamous epis
Protection
Oral cavity consists of
cheeks hard palate soft palate teeth tongue salivary glands
hard palate
roof of mouth
ridges called rugae
breaks down food
Soft palate
posterior roof of mouth
uvula hangs from it
assist in swallowing
uvula prevents food from flowing back into the nasal cavity
Tongue
lingual frenulum divides tongue in 2 halves
attached and supported by hyoid bone
Salivary glands
secrete saliva
Amylase for helps breakdown complex carbs
Lysozyme destroys bacteria
Pharynx
bolus of food is forced to back of mouth and onto oropharynx
respiratory/breathing temporarily stopped
Soft palate and uvula move upward and close off nasopharynx
Bolus passes through laryngopharynx and enters esophagus
Breathing resumes
main function of pharynx
begins the process of swallowing
esophagus
bolus passes through esophageal hiatus
joins the stomach at the cardiac sphincter (lower esophageal sphincter)
main function of the esophagus
transportation of food from pharynx to the stomach
Stomach
upper left quadrant of peritoneal cavity
divided into the cardiac, funds, body and pylorus
Curved
holds 4L of food
Collapses into longitudinal folds called rugae
stomach opens to the duodenum through the
pyloric sphincter
Gastric pits
leads to gastric glands in lining of stomach
Mucous neck cells secret mucous
Chief cells secrete pepsinogen and lipase
Parietal cells secret HCl and intrinsic factor
Enteroendocrine cells release gastrin
Function of stomach
mechanical and chemical digestion of food that form chyme that enters first part of small intestine (duodenum)
Small intestine
6 meters long first parts = duodenum (receives chyme from stomach) second part= jejunum third part = ileum Bile from liver digests fats Amylase helps to digest starch lipase digests fats proteases help digest proteins
Crypts of lieberkuhn secrete enzymes that chemically digest proteins and carbs
Absorption in walls of small intestine (surface area large due to plicae circulates, villi, microvilli)
Peyers patches are clumps of lymphoid follicles found in abundance towards the end of the small intestine
main function of small intestine
completion of digestion and the absorption of nutrients into the blood capillaries and lymphatic vessels
Large intestine
1.5m long
extends from ileum to anus
Ileocecal valve connects ileum to large intestine
regions include: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal, anus
Appendix is attached to cecum
Teniae Coli are bands of smooth muscle in walls of intestines (cause walls for form pouches called hausfrau)
Epiploic appendages are fat pilled pouches of visceral peritoneum that hang from large intestine
Functions of large intestine
absorption of water, electrolytes
synthesis of certain vitamins by intestinal bacteria
elimination of feces
Liver
reddish brown, 3lb largest organ other than skin divided into right and left lobes Lobes separated by falciform ligament Consist of lobules with hepatocytes (synthesize bile)
Function of liver regarding digestion
to manufacture bile for breakdown of lipids in duodenum
Breakdown is necessary before lipase can finish the job
Gallbladder
pear shaped
attached to liver by cystic duct
duct joints the hepatic ducts from liver to form the common bile duct
base of common bile duct forms hetaopancreatic ampulla (where main pancreatic duct joins the common bile duct)
Common bile duct empties bile into the duodenum
function of gallbladder
storage sac for bile
Pancreas
head and tail ends
Acinar cells secrete digestive enzymes into tiny ducts which merge into pancreatic duct (which empties into duodenum)
produces amylase, lipase, proteases
chemical digestion of carbs
into smaller monosaccharides
first broken down by salivary amylase
pancreatic amylase breaks down into disaccharides
broken down into monosaccharides by sucrase, maltase, lactase
End products are glucose, fructose, galactose
Chemical digestion of protein
pepsin and trypsin break proteins down into peptides
peptidase breaks down into amino acids (the end product)
chemical digestion of lipids
fats emulsified by bile
lipase acts on emulsified fats and breaks them down into monoglycerides and free fatty acids
End products are monoglycerides and fatty acid chains
Chemical digestion of nucleic acids
pancreatic nucleases enter duodenum and cause breakdown into nucleotides
Brush border enzymes break those down into pentose, phosphate, nitrogenous bases
