mechanical digestion
the physical breaking up of food into smaller pieces
ex: chewing
chemical digestion
uses of digestive enzymes to break down food into simpler molecules that the body can utilize
carbohydrates
digested into monosaccharides (glucose, fructose and galactose)
proteins
break down into amino acids
fats
are digested to fatty acids and glycerol
pulp cavity
are "alive"; innermost part of the tooth
has vessels and nerve endings that link with the trigeminal nerve (gives them the ability to feel or sense)
deciduous teeth
errupt at about 6 months
a set of 20 teeth; usually complete by 2 years of age
permanent teeth
first molars emerge around 6 years
a complete set consists of 32 teeth
types: incisors, canines, premolars and molars
tongue
part of mechanical digestion
papillae on upper surface of tongue linked with sensory nerves for taste
the facial and glossopharyngeal nerves allow us the sense of taste and secretion of saliva which aids in digestion
glossopharyngeal (9th) and facial nerves (7th)
allows us the sense of taste and the secretion of saliva which aids in digestion
allows us to enjoy the food
salivary glands
has ducts
found below the floor of the mouth
will secrete as a result of a parasympathetic response generated by the facial and glossopharyngeal nerves
moistens foods and dissolves it for digestion and aids in swallowing
salivary amylase
digestive enzyme in saliva
breaks down starch molecules to shorter chains of glucose molecules, or to maltose, a disaccharide
lysozyme
inhibits the growth of many kinds of bacteria
does not kill them; but slows the bacterial reproduction
esophagus
a muscular tube that takes food from the pharynx to the stomach
no digestion takes place here
food is propelled via peristalsis
lower esophageal sphincter
at the junction with the stomach
surrounds the lumen of the esophagus
a circular smooth muscle
relaxes to permit food to enter the stomach , then contracts to prevent back flow of stomach contents
if it does not close completely, gastric juices may splash up into the esophagus (i.e. GERD, heartburn)
stomach
a sac that extends from the esophagus to the small intestines
is a reservoir for food
*both mechanical and chemical digestion take place here
an endocrine organ as it secretes as well as is part of the digestive system
first site of protein digestion
*parietal cells secrete intrinsic factor
located in the ULQ of the abdominal cavity; to the left of the liver and in front of the spleen
small intestine
20 feet long; 1 inch in diameter
extends from the stomach to the cecum of the large intestine
digestion is completed here
end products of digestion are absorbed into the blood and lymph
goblet cells; make mucous to avoid irritation and allow ease of passage of digested food; work by using microvilli that expand to increase surface areas and absorb glucose into the capillary networks by active transport
contain Peyers Patches; lymph nodules; assist in destroying and absorbing pathogens
secretion of epithelium of the intestinal glands or crypts of Leiberkuhn is stimulated by the presence of food in the duodenum
contain peptidase and sucrose, maltase and lactase; intestial enzymes
parts:
duodenum
jejunum
ileum
goblet cells
make mucous to avoid irritation and allow ease of passage of digested food; work by using microvilli that expand to increase surface areas and absorb glucose into the capillary networks by active transport
peyers patches
lymph nodules in the small intestine
assist in destroying and absorbing pathogens that were not removed in the nasopharynx, etc.
Liver
has 2 large lobes, right and left
*located in the upper right and center of the abdominal cavity; just below the diaphragm
have capillaries called sinusoids
*the cells produce bile that will eventually be stored in the gallbladder
bile enters small bile ducts called bile canaliculi
*help regulate blood-glucose levels
excess glucose is converted to glycogen (glycogenesis) occurs with HYPERglycemia
-when the blood sugar is high, insulin and cortisol facilitate glucose conversion to glycogen
-when the glucose is low, needed glycogen is converted back to glucose for quick energy; both epinephrine and glucagon assist in this process
*synthesize albumin
*produce clotting factors: prothrombin, fibrinogen and factor 8 (circulate in the blood until needed)
*contain fixed macrophages that phagocytize old RBC's
bile canaliculi
small ducts; merge into the hepatic duct
carry bile out of the liver
parasympathetic impulses
increase peristalsis or secretions
sympathetic impulses
decrease peristalsis or secretions
serous fluid
prevents friction between the periotenum and mesentery
central veins
of all lobules
unite to form the hepatic veins
hepatic veins
take blood out of the liver to the inferior vena cava
unites wtih the cystic duct of the gallbladder
common bile duct
formed by the unity of the hepatic duct and cystic duct of the gallbladder
crucial to remain open and patent
takes bile and pancreatic juices to the duodenum
parietal cells
secrete HCl and intrinsic factor
have enzymes called proton pumps; secrete H+ into the stomach cavity
gallbladder
located under the right lobe of the liver
stores bile
when fatty foods enter the duodenum, enteroendocrine cells of the duodenal mucosa secrete choleycystokinin which is a hormone that stimulates the contraction of the gallbladder and forces biles into the cystic duct --> then goes into the common bile duct and then the duodenum
bile enters and leaves via the cystic duct
hepatic duct takes bile from the liver to here
vagus nerve
innervates the stomach (and intestines)
enteroendocrine cells
in the duodenal mucosa
secrete choleycystokinin
choleycystokinin
secreted by the enteroendocrine cells
a hormone that stimulates the contraction of the gallbladder and forces bile into the cystic duct
pancreas
produces a bicarbonate juice which is alkaline
neutralizes the acidic juices that enter the duodenum to prevent damage to the duodenal mucosa
neutralizes the HCl of the stomach
peptidase
intestinal enzyme
allows for completion of digestion and absorption
complete the total digestion of protein into amino acids
sucrose, maltase and lactase
intestinal enzymes
allow for completion of digestion and absorption
digest the dissacharides into monosaccharides
complete the digestion of sugars
epithelium of the small intestine
simple columnar epithelium
secretes mucus, which lubricates the passage of food
secretes digestive enzymes of the stomach and small intestine
microvilli
allow an increase surface area to allow for digestion
have a capillary network and a lacteal (a dead-end lymph capillary)
absorb water-soluble nutrients via capillary networks
absorption
The process by which nutrient molecules pass through the wall of the digestive system into the blood
lacteal
a dead-end lymph capillary and water-soluble nutrients are absorbed into the blood via capillary networks
normal flora
produce: vitamin K, riboflavin, thiamin, biotin and folic acid
bile
emulsifies fats
hepatic circulation
central veins of all lobules --> hepatic vein (takes blood out of the liver) --> inferior vena cava --> hepatic duct --> cystic duct of the gallbladder --> the common bile duct (crucial to remain open and patent) --> takes bile and pancreatic juices to the duodenum
albumin
synthesized by the liver
prothrombin, fibrinogen and factor 8
clotting factors produced by the liver
circulate in blood until needed in the hemostatic person
digestive flow
bile enters and leaves the gallbladder by way of the cystic duct
the hepatic duct takes the bile from the liver to the gallbladder
the gallbladder is located on the under surface of the right lobe of the liver
bilirubin
formed from the heme of hemoglobin
also removed from formed in the spleen and red bone marrow and is excreted into bile and eliminated in the feces
makes feces a brown color
liver lobule
functional unit of the liver
sinuoids
capillaries of the liver
receive blood from both the hepatic artery and portal vein
secretin
stimulates the production of bicarbonate juices by the pancreas
cholecystokinin
stimulates the secretion of the pancreatic enzymes
amylase
pancreatic enzyme
digests starch to maltase
lipase
pancreatic enzyme
converts emulsified fats to fatty acids and glycerol
trypsin
pancreatic enzyme
changed into the active form from an inactive enzyme called Trypsinogen in the duodenum
digests polypeptides to shorter chains of amino acids
characteristics of the stomach
produces a hormone to increase its own secretions
permits digestion to take place gradually
first place in digestive system where the digestion of proteins begins
Kupffer cells
fixed macrophages of the liver
destroy old RBCs
phagocytize pathogens or other foreign material that circulate through the liver
removing theses substance from the blood before the blood returns to the heart and is pumped to the lungs
defecation reflex
accomplishes elimination of feces
a spinal cord reflex that may be controlled voluntarily
stretch receptors that generate sensory impulses that travel to the sacral spinal cord
hypoglycemia (reaction)
needed glycogen is converted back to glucose for quick energy
assisted by epinephrine and glucagon
hyperglycemia (reaction)
insulin and cortisol facilitate glucose conversion to glycogen