Digestive System Flashcards
What are the organs in the gastrointestinal tract?
mouth, pharynx, esophagus, stomach, small and large intestines
What are the main accessory organs?
Teeth, tongue, pancreas, liver, gallbladder
What are the 6 functions of the digestive system?
Ingestion - food entering
Mechanical breakdown - making the pieces smaller
Propulsion - moving ingested food
Chemical digestion - converts ingested food into useful chemicals
Absorption - bringing chemicals into body for use
Defection- excreting good waste
Which layer of digestive tissue lines the lumen?
Mucosa
What are the four layers of digestive tissue (deep—> superficial)?
Mucosa, submucosa, muscularis externa, serosa
What are the characteristics of the mucosa?
-thin epithelial cells
-functions in secretion, absorption, and protection
-made of two layers… lamina propria and muscularis propria (made of smooth muscle to help with movement)
What are the characteristics of the submucosa layer?
-connective tissue
-contains capillaries (absorption), lymph vessels/nodes, sensory nerve fibers, and elastic fibers (expansion)
What are the characteristics of the muscularis externa?
-2 smooth muscle layers
-functions in propulsion and mixture
What are the characteristics of the serosa?
-made of CT and epithelial cells
-has some immune cells
What is the job of the enteric nervous system?
move food from one place to another (has lots of reflex arcs that are fast and automatic)
What is the difference between simple and parallel processing?
simple requires no brain involvement and is fast/predictable, parallel requires the brain and has more diverse outcomes
What is the path of a long reflex arc?
stimulus –> receptor –> sensory neuron –> spinal cord –> motor neuron –> effector –> response
Which part of the long reflex arc is not involved in a short reflex?
spinal cord
What accessory organ in the mouth performs mechanical breakdown?
teeth
Can the mouth help with the digestion of food?
yes but not a lot because its only there for a short period of time
What type of cells line the mouth and why are they beneficial?
stratified squamous epithelium (protection)
What is a bolus?
a single swallow of food
Why is saliva slightly acidic?
helps to fight off pathogens
What does amylase do?
breaks down starch
What does lipase do?
breaks down fat
What type of glands are salivary glands?
exocrine
What are the three divisions of the pharynx?
nasopharynx, oropharynx, laryngopharynx
What type of cell is the pharynx made out of?
stratified squamous epithelium
What do the mucous producing glands of the pharynx do?
helps keep the bolus moving
What is deglutition?
swallowing
What are the two phases of swallowing?
buccal and pharyngeal-esophageal phase
What happens during the buccal phase of swallowing?
tongue presses against hard palate and bolus transfer is initiated (voluntary process)
What happens during the pharyngeal-esophageal phase of swallowing?
nasopharynx closes off and epiglottis blocks trachea to prevent aspiration (involuntary process)
What is the job of the esophagus?
move bolus to stomach
What are the sphincters in the esophagus for?
performing peristalsis
What is peristalsis?
bolus causes stretching and that causes a contraction above it which pushes it down the esophagus
What sphincter opens to allow bolus to enter stomach?
gastroesophageal sphincter
Why does the lumen of the esophagus have folds?
allows for expansion
What type of muscle tissue is found in the esophagus?
upper 1/3 = skeletal
middle 1/3 = transition from skeletal to smooth
lower 1/3 = smooth
What is the stomach responsible for?
reservoir for food, slowly release food into small intestine, mechanical breakdown, some chemical digestion, produce appetite control hormones, absorption (alcohol)
What does the gastroesophageal sphincter do?
keeps acid in stomach and allows bolus from esophagus to enter
Where is the fundus and what does it do?
upper portion of stomach, release hormones for satiety
What is the rugae?
folds in the stomach that help with stretching
Where is the pyloric sphincter?
opening to the small intestine… bottom of stomach
Where are stomach contractions the highest?
pyloric antrum
What are the greater and lesser omentums for?
supplying and storing nutrients
What is GERD?
gastroesophageal reflex disorder, result of long term and repeated acid reflex
How does acid reflex occur?
stomach has pacemaker cells so its always contracting and if there is a problem with the lower gastroesophageal sphincter, the acid can get into the esophagus
What are the four gastric gland cells?
mucous neck cells, chief cells, parietal cells, enteroendocrine cells
What makes up gastric juice?
enzymes and acid
Where is gastric juice produced?
gastric pits
What type of cells is the stomach mucosa made of?
simple columnar
What does the basic slime do?
helps protect cells from acid
What is the job of microvilli?
increase surface area
What do parietal cells produce?
hydrochloric acid (HCl) and intrinsic factor
What are the three functions of HCl?
denature proteins, antimicrobial agent, activates enzymes
Why is intrinsic factor required to live?
its needed for erythropoiesis
Are digestion and denaturing the same thing?
no !!
What three things help protect your cells from stomach acid?
tight junctions, basic slime, underlying stem cells
How do you get stomach ulcers?
the bacteria H. pylori can dig through mucous cells and break open tight junctions which allows your stomach acid to get in and erode the cells
What do chief cells produce?
pepsinogen and lipase
How does pepsinogen get activated?
HCl + pepsinogen = pepsin
What does pepsin do?
breaks down proteins
What do enteroendocrine cells release/produce?
serotonin, gastrin, and histamine
Why do enteroendrocine cells have lots of blood vessels?
release hormones into blood
How do enteroendocrine cells play a role in producing HCl?
they produce gastrin and histamine which make HCl when they reach a parietal cell
Which hormones increase the production of gastric juices?
gastrin and histamine (technically not a hormone)
What hormone decreases production of gastric juices?
gastrin inhibitors
What are the three phases of gastric juice production?
cephalic, gastric, and intestinal
How is the cephalic phase activated?
starts before you eat when you see/smell/think about food
What happens when the cephalic phase is activated?
the P-ANS activates enterochromaffin-like cells (ECL) that produce histmine. histamine interacts with parietal cells to increase HCl and indirectly increase pepsin
How is the gastric phase activated?
starts when bolus enters stomach due to the stimuli: stomach distension, present of undigested proteins, and caffeine
What is a G cell?
a type of enteroendocrine cell that releases gastrin
What is the indirect effect of gastrin?
activates ECL cells to release histamine which interacts with parietal cells to release HCl
What hormones can be released during the intestinal phase?
secretin (more HCl)
gastrin inhibitors (less HCl)
What does the duodenum do during the intestinal phase?
tests chyme to check for acidity and release hormones accordingly
What three factors can cause gastric juice production to stop?
pH gets too low, gastrin inhibiting hormones released, or sympathetic nervous system activity increases
What is the product of broken down fats?
monoglycerides and fatty acids
How is protein broken down?
protein + HCl = polypeptide chain + pepsin = amino acids
What are the three layers the muscular externa?
Oblique, circular, longitudinal
What causes mechanical breakdown in the stomach?
contractions
How often does the stomach contract?
3x/minute
How does dissension affect contractions?
cause increased strength
Why are contractions strongest at pyloric antrum?
reduce how much food is released into small intestine
How much chyle does the small intestine receive (and return) per minute?
receives ~30mL and returns ~27mL
What two types of propulsion does the small intestine perform?
peristalsis and segmentation
What does a segmentation contraction do to chyle?
pushes it in both directions
What are the folds in the small intestine called?
plicae circulares
What makes up the brush border of SI?
enzymes and dense microvilli
What the five cells of the small intestine?
enterocyte, panted cells, goblet cells, enteroendocrine cells, stem cells
What do enterocytes do?
make enzymes and allow for absorption (simple columnar epithelium)
What do paneth cells do?
make antimicrobial compounds
What do goblet cells do?
produce mucous for lubrication
What do the stem cells in the small intestine do?
replace cells that are killed by the acidity of the chyme
What type of cells make up the mucosa of the small intestine?
simple columnar epithelium
What are Peyer’s patches?
lymphoid tissue found in distal small intestine
What are Peyer’s patches?
lymphoid tissue found in distal small intestine
What do duodenal glands produce?
alkaline mucous
Where is intestinal juice produced?
intestinal crypts
Is intestinal juice alkaline or acidic?
alkaline (made mostly of water)
What activates the intestinal crypts?
distension
Where can you find a high concentration of crypts and a low concentration of goblet cells?
duodenum
Where can you find a low concentration of crypts and a high concentration of goblet cells?
ileum
Why are more goblet cells found at the end of the small intestine?
they produce lubricant that helps because the chyle drys out as it moves
What does the pancreas produce to aid in digestion?
pancreatic juice that contains pancreatic enzymes
What three (kinda four) enzymes are found in pancreatic juice?
pancreatic amylase (starch)
pancreatic lipase (fats)
trypsin and chymotrypsin (protein)
When is more pancreatic juice released?
when you have a fatty meal or undigested proteins or secretin and CCK are present
What does the liver do?
stores nutrients, activates hormones and vitamins, and produces bile
What does the gallbladder do?
stores bile and releases it through the bile duct
What are bile salts?
found in bile and emulsify (break apart) fat to make it easier to be digested
Are emulsification and digestion the same thing?
no
How/where are carbs digested?
partially with saliva but mostly in the small intestine
How are carbs broken down?
carbs + amylase = disaccharides + brush border enzymes = monosaccharides (end result)
Where are proteins digested?
~10/15% in the stomach but primarily in the small intestine
How are proteins broken down?
protein + trypsin/chemotrypsin = smaller amino acid chains + brush border enzymes = free amino acids
Where are lipids digested?
small intestine
How are lipids broken down?
fat + bile salts = emulsified fat + lipase = free fatty acids + bile salts = micelles
What is a micelle?
a free fatty acid surrounded in bile salts that can be absorbed
What are the two processes of absorption for free amino acids and monosaccharides?
co-transport and facilitated diffusion
What cell absorbs free amino acids and monosaccharides?
enterocyte
What do amino acids and monosaccharides travel into enterocytes with?
sodium ions
How is fat absorbed?
micelle goes into enterocyte by simple diffusion and is then a triglyceride and then is excreted into lymphatic capillary
What does the small intestine absorb?
vitamins, electrolytes, and water
What is the large intestine primarily responsible for?
defacation
What structure moves feces through large intestine?
haustra
