digestive system Chp 24 Flashcards
function of the digestive system and how many stages its accomplished by?
process food, extracts its nutrients, elimate the residue
- in 5 stages
what are the 5 stages the digestive systems function is accomplished by?
- ingestion
- digestion
- absoprtion
- compaction
- defecation
mechanical digestion
physical breakdown of food into smaller pieces
- cutting and grinding action of teeth
- churning of stomach and SI
chemical digestion
hydrolysis reactions that break diet macromolecules into usable forms
- uses digestive enzymes of salivary glands, stomach, pancreas + SI
where does mechanical and chemical digestion take place
mouth, stomach, small intestine
what are the 2 anatomical subdivisions of the digestive system
- digestive tract (alimentary canal)
musuclar tube from mouth to anus - accessory organs
- teeth, tongue,salivary glands, liver, gall bladder, pancreas
what accessory organs of the digestive system has ducts that release enzymes into the digestive tract
liver, gall bladder, pancreas
different type of epithelium located throughout digestive tract
oral cavity + distal anal cavity = stratified squamos
everything else= simple columnar
peristalsis
waves of contraction of circular muscle moving digested food forward the digestive track
segmentation
cycles of smooth muscle contraction that break up food bolus into smaller parts
what type of digestion begins in the mouth
carbohydrate (starch) digestion via salivary amylase and fat digestion via lingual lipase
what is and does saliva do
binds food into soft lubricated mass (bolus)
- is 97-99.5% water with a acidic pH of 6.8-7.0
- has antibacterial antibodies and enzymes
- mucous, salivary amylase, lingual lipase
what are the 3 salivary glands in the oral cavity and what do they secrete
- parotid glands in the cheek produce 25% of saliva
- submandibular glands produce 70% of saliva
- sublingual glands produce 5% of saliva (below the tongue)
salivary glands are
small glands among the oral tissue that constantly secrete saliva in small amounts
what is the muscular funnel connecting oral cavity to esophagus
the pharynx which has pharygeal constrictors that force food down during swallowing by contracting
what sphincter prevents regurgitation of stomach contents
lower esophageal sphincter (end of the esophagus)
what are the 3 tissue layers of the digestive tract
- mucosa (deepest)
- submucosa
- muscularis externa (most superficial)
the components of all 3 tissue layers of the digestive tract
- mucosa - stratified squamous epithelium (oral and distal anus)
- submucosa- esophageal glands secreting lubricant mucus into lumen
- muscularis externa- skeletal muscles in upper part and smooth muscle in lower
deglutition is also known as
swallowing
what are the 3 phases of deglutition/swallowing
- buccal phase
- pharyngeal phase
- esophageal phase
buccal phase of deglutition
compression of bolus against hard palate
- retraction of tongue forces bolus into oropharynx
- strictly voluntary
food in mouth between tongue and hard palate
pharyngeal phase of deglutition
involuntary, starts with stimulation of receptors on uvula, elevation of larynx to epiglottis, food moved to esophagus
esophageal phase of deglutition
involuntary, peristalsis moves food towards stomach
what are the cells of the gastric glands?
mucous cells, regenerative cells, parietal cells, chief cells, enteroendocrine cells
regenerative cells
new epithelial cells to replace old/damaged ones
parietal cells
produce intrinsic factors and HCL
what does HCL that parietal cells produce do
contribute to acid pH, breaks down connective tissue + plant cell wall, activates gastric lipase and pepsinogen
instrinstic factor is essential for
vitamin B-12 absorption
- required for Hg synthesis
chief cells
produce pepsinogen and gastric lipase (breaks down lipids)
pepsinogen
breaks down proteins when activated to pepsin
enteroendocrince cells / G cells
produce hormones such as gastrin which increases motility + secretion of stomach
gastric lipase
breaksdown lipids
- enzyme that dogests 10-15% of dietary fat along with lingual lipase
what are the 3 ways the stomach is protected of the harsh acidic environment
- mucous coat (its thick + highly alkaline)
- tight junctions between epithelial cells so no acid leaves
- epithelial cell replacement
- high rate of cell division where the cell lives 3-6 days long
what are the 3 main regions of the small intestine ( closest to farthest away)
- duodenum ( closest)
- jejunum
- ileum
3 structures of the small intestine’s mucosa that helps increase surface area
Circular folds, villi, microvilli
what are the 5 main hormones that regulate digestion
- gastrin
- secretin
- gastric inhibitory peptide (GIP)
- cholecystokinin (CCK)
- vasoactive intestinal peptide (VIP)
gastrin
made in the stomach and its secreted by g cells.
promotes increased stomach motility and increases secretion of gastric acids + enzymes
secretin
made in the SI and released when chyme arrives in the duodenum
increases secretion of bile (by the liver) + buffers (pancreas)
reduces gastric motility and secretory rates
gastric inhibitory peptide (GIP)
made in the SI, secreted when fats + carbohydrates enter SI
inhibits gastric / stomach activity and stimulates pancreas to release insulin
- turns off stomach
cholecystokinin (CCK)
made in the SI and secreted when chyme arrives at duodenum esp if it has lipids
- increases secretions of pancreatic enzymes + pushes pancreatic secretions and bile into the duodenum
- too much of this turns off sstomach
vasoactive intestinal peptide (VIP)
- stimulates secretions of intestinal gllands
- dilates regional capillaries
- inhibits acid production in stomach
what are the 2 stages of gastric activity/secretion
- cephalic stage
- gastric phase
- intestinal phase
cephalic stage
controlled by the brain
starts when you see, smell. taste or think of food
- prepares stomach to receive food
gastric phase
controlled by the stomach itself
- begins with the arrival of food in the stomach and builds on the stimulation provided
- increased secretion of gastric juice and churning of stomach after the 1st hour
intestinal phase
controlled by SI and starts when food arrives in the SI
- controls rate of gastric (stomach) emptying to ensure the secretory, digestive, adsoprtive functions of the SI can continue
primary function of the large intestine
