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alimentary canal
the GI tract, a continuous muscular digestive tube
accessory digestive organs
teeth, tongue, gall bladder, salivary glands, liver, and pancreas
The tongue’s attachments
hyoid bone, the mandible, and the lingual frenulum
mastication
food being chewed by the teeth in the mouth
root of the tooth
largest portion, in the jaw bone
neck of the tooth
in the gums
crown of the tooth
visible portion above the gums
tooth pulp cavity
center, contains nerves and blood vessels
dentin
bone-like substance composing most of each tooth
enamel
surface of the tooth, hard connective tissue that protects the rest of the tooth
bolus
a compact mass of food
papillae
bumps on the tongue, circumvallate, fungiform, and filiform
circumvallate and fungiform
contain taste buds
mucosa
secretes mucus into the interior the gastrointestinal tract
submucosa
contains blood and lymph vessels, lymph nodes, nerves, and mucous glands
muscularis externa
two layers of muscle: the outer longitudinal fibers and inner circumferential fibers
serosa
cells that make serous fluid
Cardiac Sphincter
where food enters the stomach from the esophagus. (also called lower esophageal or gastrointestinal)
pyloric sphincter
where food exits the stomach to the small intestines
lesser omentum
attaches the lesser curvature of the stomach to the liver
greater omentum
attaches the greater curvature of the stomach to the posterior wall of the abdomen, covering the transverse colon and anterior surface of the small intestines
cardia
part of the stomach where the food enters from the esophagus
fungus
dome-shaped top of the stomach just under the diaphragm
body
wider midportion of the stomach
pyloric region
funnel-shaped end of the stomach
rugae
folds within the stomach wall, which allows the stomach to expand when it is full
purposes of the stomach
1) temporary food storage
2) mechanical food breakdown
oblique layer
third layer in the muscularis externa to allow mixing of food and juices easier
ulcer
an open sore in the wall caused by the gradual disintegration of tissues
chyme
stomach contents, thick soupy substance
ileocecal valve
controls the entrance to the large intestine
duodenum
first and shortest section of the small intestine, where enzymes from the pancreas and bile from the liver enter the small intestine
jejunum
second section of the small intestine
ileum
final section of the small intestine, slightly longest
circular folds
increase surface area of the wall's mucous membrane
villi
small finger-like projection, absorb a huge number of molecules.
microvilli
smaller projections off of the villi
lacteal
lymphatic vessels, transports molecules that are too large after reassembling
capillary beds
where sugars and amino acids are absorbed
intestinal enzymes
remain attached to the plasma membrane of microvilli, complete the digestion of peptides and sugars.
parts of the large intestine
cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal
cecum
entrance to the large intestine through the ileocecal valve
appendix
hangs from the cecum and is usually twisted
ascending colon
runs along the right side of the abdomen superiorly
transverse colon
runs across the abdomen, connected with the hepatic flexure
descending colon
runs along the left side of the abdomen superiorly, connected with the splenic flexure
sigmoid colon
travels through the pelvis connecting with the rectum
internal sphincter
involuntary smooth muscle
exernal sphincter
voluntary skeletal muscle
intestinal bacteria
produces vitamin K and certain B vitamins
feces
75% water, intestinal bacteria, undigested plant material, fats, waste products (such as bile pigments), inorganic material, mucus, and dead cells from the intestinal lining.
pancreas
lies deep in the abdominal wall, sends pancreatic juice into the duodenum by the pancreatic duct
pancreatic juice
contains sodium bicarbonate to neutralize chyme and make the pH of the small intestine slightly basic, travel to the duodenum
Pancreatic amylase
digests starch to maltose
trypsin and other enzymes
digest protein to peptides
lipase
digests fat droplets to glycerol and fatty acids
function of the liver
produce bile, stores glucose as glycogen, produces urea
bile
stored in the gallbladder, sent to small intestine to emulsify fats, looks green, contains bile salts, breaks down fat into smaller pieces and is needed for the absorption of fats
roles of the digestive system
ingestion, digestion, absorption, and defacation
mechanical digestion
occurs when food is physically broken down into smaller pieces. teeth chewing food, stomach mixing food, and food moving along the gastrointestinal tract
chemical digestion
chemical breakdown of food by enzymes into smaller nutrients
salivary amylase
in the saliva, begins the chemical breakdown of starches
peristalsis
rhythmic muscular contractions, to move food through the esophagus and to the small intestine
salivary glands
parotid, sublingual, and submandibular glands, release saliva
gastrin
stimulates the stomach to secrete gastric juices, which contain: pepsinogens, mucus, and hydrochloric acid
parietal cells
secrete hydrochloric acid to kill bacteria with high acidity.
pepsinogen
pro-enzyme, secreted by the chief cells, converted to pepsin by the HCl to breakdown proteins.
mucus
protects the stomach lining from the HCl and pepsinogens
peptides
result from the first step in protein digestion, are digested by peptidases to amino acids
maltose
results from the first step in starch digestion, is digested by maltase to glucose
cholecystokinin
causes the gallbladder to secrete bile, cause the pancreas to secrete juices
secretin
causes the liver to secrete bile, cause the pancreas to secrete juices
hypothalamus
region of the brain that plays a role in hunger, satiety, and the feeling of “being full”
feeding center
nutrients in the blood decline, which stimulates the hypothalamus and makes the body feel hungry
satiety center
when the nutrient level rises, the hypothalamus is activated, and the desire to eat declines
as the stomach expands and nutrients are absorbed…
…the stomach sends sends signals to the brain and the desire to eat declines
hunger increasing hormones
Ghrelin, Endorphins, Neuropeptide-Y
hunger decreasing hormones
Leptin, Serotonin, Cholecystokinin (CCK)
leptin
produced by fat cells, alerts the brain to turn off the hunger center in the brain and activate the satiety center
ghrelin
produced by the stomach, travels to the brain and stimulates the hunger center as it deactivates the satiety center
carbohydrates
starches and sugars including milk, fruits, and grains, main source of energy for most cells
lipids
contain saturated fat, unsaturated fat, and cholesterol,
incomplete proteins
food such as grains, legumes, seeds, and nuts
complete proteins
meat, poultry, eggs, milk, dairy products, and soybeans
essential amino acids
nine amino acids that the body is unable to make, complete proteins contain them all
vitamins
organic compounds that are not consumed in metabolic reaction but help enzymes carry out the metabolic reactions
water soluble vitamins
are not able to be stored in the body and are excreted in urine
fat soluble vitamins
are stored in body fat, excessive amounts can be problematic
minerals
inorganic compounds that are not used as fuel in metabolic reactions but are combined with other nutrients to form necessary body substances
minerals include
calcium, chloride, magnesium, phosphorus, potassium, sodium, and sulfur
anabolism
the set of reactions in which smaller molecules are combined to make larger, more complex molecules
catabolism
the set of reactions in which larger molecules are broken down to be used as energy sources for the body
cellular respiration
the process by which cells generate ATP
aerobic respiration
requires oxygen and a fuel and releases carbon dioxide, water, and ATP.
glucose metabolism
used primarily during high energy demands, used in ATP production, results in 38 ATP per molecule of glucose
glycolysis
first step in glucose metabolism, yields 2 atp, breaks down one glucose molecule into two pyruvate molecules
fermentation or respiration
2nd step in glucose metabolism, yields 2 ATP,
electron transport chain
final step in glucose metabolism, yields 34 ATP, can be aerobic or anaerobic (aerobic in humans) electrons transfers out of NADH/FADH2 to electron acceptors and energy is released
cellular respiration
aerobic process, inside and around the mitochondria, krebs cycle
fermentation
anaerobic process