Chapter 23 Flashcards
Function of Digestive System
the digestive system takes in food
breaks it into nutrient molecules
absorbs molecules into the bloodstream
eliminates waste
2 main groups of digestive system organs
Alimentary Canal (gastrointestinal tract) and accessary digestive organs
Alimentary Canal
muscular digestive tube that winds through the body
organs include mouth, pharynx, esophagus, stomach, small intestine, and large intestine
Accessary digestive organs
organs include teeth, tongue, gallbladder, salivary glands, liver, and pancreas
digestive processes
ingestion: the taking in of food in the mouth
propulsion: movement of food through the alimentary canal
-includes swallowing and peristalsis
mechanical digestion: (starts in the mouth) physically prepares food for chemical digestion
-includes chewing, churning of food in stomach, and segmentation (constrictions of the intestine)
chemical digestion: series of steps in which complex food molecules are broken down into their chemical building blocks
-carried out by enzymes
absorption: the transport of digested end products from the alimentary canal to blood and lymph capillaries
defecation: the elimination of indigestible substances from the body
peritoneum and peritoneal cavity
the serous membrane of the abdominopelvic cavity
- consists of the parietal peritoneum and the visceral peritoneum
- contains serous fluid in the peritoneal cavity
mesentery
a double layer of peritoneum that extends from the body wall to the digestive organs
functions: holds the organs in place, sites of fat storage, and provides a route for circulatory vessels and nerves
intraperitoneal cavity:
-digestive organs that have a mesentery
secondarily retroperitoneal cavity:
-digestive organs with no mesentery (develop out mesentery but are still in the cavity)
layers of the alimentary canal wall
mucosa -innermost layer submucosa -just external to the mucosa -layer of CT muscularis externa -external to the submucosa -smooth muscle layer responsible for peristalsis serosa -the visceral peritoneum
the mouth
the oral cavity
entrance to the alimentary canal
lined by stratified squamous epithelia
contains the:
-lips and cheeks
-palate
-tongue
-teeth
-salivary glandssalivary glands
produce saliva ( a mixture of water, ions, mucus, and enzymes)
functions of saliva:
-moistens the mouth
-dissolves food chemicals
-wets and binds food together (bolus)
-enzymes begin digestion of starches
-has antibacterial and antiviral properties
the pharynx
continuation of the mouth
lined by stratified squamous epithelia
contains pharyngeal constrictor muscles that are used for swallowing
esophagus
a muscular tube that propels food to the stomach
joins the stomach at the cardiac orifice
the cardiac sphincter works to prevent the regurgitation of stomach acid into the esophagus
stomach
food is churned and turned into a paste called chime
-Pepsin (an enzyme) begins to break down proteins
hydrochloric acid also helps to break down food and kills bacteria
-some substances ( water, electrolytes, and some drugs) are absorbed
gross anatomy of the stomach
regions:
-cardiac
-fundus (the dome)
-body
-pyloric regions ( consists of the pyloric antrum and pyloric canal)
-pylorus (contains the pyloric sphincter)
Rugae
-internal folds of the mucosa which flatten as stomach fills (start to flatten out and cause expansion)
microscopic anatomy of the stomach
has all layers of the alimentary canal with a unique muscularis externa that works to churn food
-simple columnar epithelium contains gastric glands (with cells) that secrete a specialized mucus
-other gastric glands cells:
~mucous neck cells
~parietal (oxyntic cell) -produce HCl
~chief (zymogenic) cells- produce pepsinogen, which become pepsin
small intestine
the longest part of the alimentary canal
- the site of the most enzymatic digestion and almost all absorption of nutrients
- runs from the pyloric sphincter to the large intestine
gross anatomy of the small intestine
3 subdivisions:
Duodenum (5%)
-receives digestive enzymes from the pancreas and bile from the liver and gallbladder
Jejunum (40%)
Ileum (60%)microscopic anatomy of the small intestine
modifications of absorption:
-circular folds (increase surface area)
-villi (contain lacteals and absorptive cells)
-microvilli
cell types:
-absorptive cells
-goblet cells (produce mucus)
-enteroendrocrine cells (secretes hormones that act on the pancreas and gallbladder)
large intestine
receives mainly digested residue that contains a few nutrients
- absorbs the remaining nutrients
- main function is to absorb water and electrolytes from the digested mass, forming semisolid feces
gross anatomy of the large intestine
composed of the following subdivisions:
- cecum (flat structure)
- vermiform appendix (collect potential pathogens)
- colon (3 parts: semi, transverse, descending)
- rectum (terminal portion)
- anal canal (end)
Teniae coli
-thickenings of the muscularis external that causes the large intestine to pucker into a haustra
ileocecal valve
-surrounds the opening of the ileum into the cecum
vermiform appendix
-contains lymphoid tissue
internal anal sphincter
-smooth muscle (involuntary)
external anal sphincter
-skeletal muscle (voluntary)
microscopic anatomy of the large intestine
similar to the small intestine with a greater abundance of goblet cells
the liver
the largest gland in the body
-digestive function is the production of bile (emulsifies fats in the small intestine)
gross anatomy of the liver
made up of 4 lobes:
-right, left, quadrate, and caudate
Porta hepatis
-site where most of the major vessels and nerves enter and leave the liver
Hepatic ducts
-right and left hepatic ducts forms from the fusion of the right and left ducts
microscopic anatomy of the liver
hepatocytes (liver cells)
-carry out almost all of the functional aspects of the liver
the gallbladder
muscular sac on the right lobe of the liver
- functions to store and concentrate bile produced by the liver
- cystic duct joins the common hepatic duct from the liver to form the common bile duct which empties into the dudenum
the pancreas
digestive gland
-produces:
~enzymes used to digest food in the small intestine
-hormones that regulate blood sugar levels
gross anatomy of the pancreas
3 regions:
- head
- body
- tail
microscopic anatomy of the pancreas
Acinar cells
-produce 22 kinds of digestive enzymes
Pancreatic islets (islets of Langerhans)
-produce insulin and glucagon
