Digestive System Flashcards
Why is the digestive system referred to as a “disassemble line”?
break down nutrients & absorb them so they can be distributed to the tissues
What are the stages of digestion (know the sites) and what are the end products of mechanical
and chemical digestion in the oral cavity and in the stomach?
Stages of digestion
1. ingestion
2. digestion
3. absorption
4. compaction
5. defecation
end product of mechanical and chemical digestion= Chyme
What is peristalsis?
peristalsis= involuntary contraction, creates wavelength movements that push contents forward
Which organs constitute the primary and accessory organs of the digestive system?
primary organs= ones that are connected together, mouth, pharynx, esophagus, stomach, small intenstine, large intestine
accesory organs= teeth, tongue, salivary glands, liver, gallbladder, and pancreas
What is the role of enteric nervous system?
enteric nervous system is the nervous network of the digestive tract
composed of two networks of neurons
-submucoscal plexus= regulates glands and smooth muscle in the mucosa
-Myentric plexus= Major nerve supply that controls GI tract mobility.
How are secretions and motility regulated in the digestive system?
Secretions are regulated by the enteric nervous system
submucosal plexus= regulates glands and smooth muscle in mucosa
myentric plexus= controls Gi tract mobility, parasymphatic ganglion
What are the contents of saliva? What are the functions of saliva?
contents= Blood filtrate + salivary amylase, lipase, mucus, IgA,
lysozyme, electrolytes
Functions- cleans mouth, inhibits pathogens,
dissolves molecules, digestions of carbohydrates and
lipids, stimulates taste buds, ease of bolus formation
and swallowing
What is the effect of sympathetic and parasympathetic division on salivary secrtion?
Parasympathetic – Stimulate production of
abundant thin saliva rich in enzymes
Sympathetic – decreased salivation due to
vasoconstriction
What phases regulate swallowing?
oral phase= voluntary tongue forms a food bolus and pushes it down
pharyngeal phase= involuntary, oral and nasal cavities are blocked, pharyngeal constrictors push bolus to esophagus
esophageal phase= involuntary, peristalsis pushes bolus downward, relaxation of lower esophageal sphincter admits it into the stomach
What is the volume of the stomach when empty, after a typical meal, and after a very large
meal? What is chyme?
Food storage- empty (50 mL), after meal (1-
1.5 L), may hold up to 4L
chyme= partially digested food
How does the stomach differ from the basic structural plan of the digestive system?
Variation from basic structural plan
* Mucosa with simple glandular epithelium
* Mucosa and submucosa are flat when full but
forms rugae when empty
* Lamina propria is occupied by tubular glands
* Muscular externa has longitudinal, circular and
oblique muscles
What are the gastric pit’s cell types and what are their functions?
gastric pit cell= cells that line stomach
mucous cells= secrete mucous
parietal cells= secerte HCl and intrinsic factor called grhelin
chiefs cells= secrete gastri lipase and pepsinogen
enteroendocrine cells= secrete gastrinm histamine, serotonin, somatostatin into the lamina propria
What is the alkaline tide?
high pH blood, causesd when the production of hydrochloric acid is produced, while bicarbonate ions accumulate in the blood
What is a zymogen?
digestive enzymes that are secreted as inactive proteins that are converted to active enzymes by the removal of amino acids
What are the ANS innervation and the arterial and venous circulation of stomach?
Innervation & circulation
* Parasympathetic by vagus nerve
* sympathetic by celiac ganglion
* Arterial by celiac artery
* Venous by hepatic portal system
What protects the stomach from “self-digestion”?
To keep from digesting itself, the stomach has a
mucosal barrier with: coat of mucus on the stomach wall, epithelial cells joined by tight junctions, and gastric juices that are only released in presence of food
What are the three phases of gastric regulation? Understand the key events associated with
these phases.
Cephalic Phase: Sight or thought of food stimulates
secretions from parietal cells, Chief cells, and mucus
cells.
* Gastric Phase: Release of gastrin to the blood,
Stomach distension & increase in pH due to food.
* Intestinal Phase: Mostly inhibitory: small intestine
receptors are activated by influx of chyme –
enterogastric reflex.
What function of liver helps in the process of digestion? What are falciform and round
ligament? What are Kupffer cells
function= synthesis of bile salts, excretion of bile
falciform ligament= binds liver to diaphram and
the anterior abdominal wall
round ligament= the remnant of former
umbilical vein.
Kupffer cells= hepatic macrophages found in liver
sinusoids
what is bile? How much bile is produced by the liver each day? Where is it stored? How
much of the bile acid are “reabsorbed”?
bile= yellow, brownish, green fluid produced by liver, 500-1000mL/day
bile is stored in the gallbladder
80% of bile is reabsorbed by small intenstine and secreted by liver
What are the endocrine and exocrine functions of pancrease? What is the role of bicarbonate?
endocrine= release of insulin and glucagon
exocrine= secretes pancreatic juice, breaks down all categories of foodstuff
the pancreas secretes bicarbonate, it increases pH, buffers acidic chhyme, and stops pepsin action
What type of zymogens and enzymes are secreted by the pancreas? What is enterokinase and
what is its role?
pancreatic zymogens= trypsinogen, chymotrypsnogen, procarboxypeptidase
enteropeptidase (enterokinase)= enzyme on the brush border of the duodenum, converts trypsinogen to trypsin
What three stimuli regulate the pancreas and gall bladder?
acetylcholine
cholecystokinin
secretin
What are the three segments of the small intestines? How long is the small intestine?
dueodenum, jejunum, ileum
3-8 m long,
Absorption is a function of the surface area. What structures in the small intestine increase its
surface area?
circular folds, villi, microvilli
Where are the intestinal crypts located?
small intestine
What are Paneth cells?
phagocytic - produce lysozyme,
phospholipase and defensins
What two types of contractions are associated with the small intestine?
segmentation= Localized mixing motions, bring contents in
contact with mucosa and move contents towards
Large Intestine, regulated by pacemaker cells
peristalsis= begins after nutrients have been absorbed,
How are macromolecules (carbohydrates, proteins, and lipids) digested and absorbed into the
body?
carb digestion= salivary
amylase, pancreatic amylase, & brush border
enzymes dextrinase, glucoamylase, maltase, sucrase,
lactase help digest carbs
protein digestion = enzymes that digest proteins are proteases(peptidases)
lipid digestion= lipase
How much residue passes into the large intestine each day? How long is the large intestine?
500 ml of indigestible food residue per day
1.5 m long
How do bacteria of the large intestine benefit humans?
- Colonize the colon
- Ferment indigestible carbohydrates
- Release irritating acids and gases
(flatus) - Synthesize B complex vitamins and
vitamin K
How long does it take to process the chyme into feces? What occurs during this process?
What is flatus?
36 to 48 hours to reduce the residue of a meal to feces
flatus= intestinal gas
during this process water is reabsorbed and electrolytes
What are haustral contractions and mass movements?
haustral contractions= type of colonic motility (every 30 mins)
-Slow segmenting movements that move the
contents of the colon.
– Haustra sequentially contract as they are
stimulated by distension.
– Trigerred by gastrocolic and duodenocolic reflex.
– Initiates peristalsis that forces contents toward the
rectum.
mass movements= stronger contractions (1-3 times a day)
Describe the defecation reflex. Is it involuntary or voluntary?
initiated by rectal stretching, involuntary
intrinsic defecation reflex= mediated entirely by myenteric plexus
parasymphathetic reflex= spinal reflex
What is the importance of the anal sinuses?
as feces passes through them the sinuses cause extra mucus to be released which lubricates the canal during defecation
What causes peptic ulcer and Gall bladder stones
peptic ulcer= inflammation of stomach, caused by acid-resistant bacteria Helicobater pylori
gall bladder stones = cholelithiasis
