Unit 6: Digestive System Flashcards
2 major divisions
- digestive tract
- accessory glands and structures
digestie system length
15 ft but 30 when dissected
general functions
- motility
- secretion
- digestion
- absorption
- immunological
the digestive system is ?
unidirectional
volume absorbed by the small intestine per day
9000 mL
sources of volume absorbed by the small intestine per day
- ingested
- secreted from plasma
volume of food eaten per day
1250 g
volume of fluid drank per day
1250 mL
sources secreted from the plasma
- saliva
- gastric juice
- pancreatic juice
- bile
- intestinal juice
tissue types in the digestive tract wall
- epithelium
- lymphoid tissue
- connective tissue
- nerve plexuses
- smooth muscle
digestive tract wall
- mesentery
- serosa
- submucosa
- muscularis externa
- mucosa
- myenteric plexus
- submucosal plexus
digestive tract wall nerves
- myenteric plexus
- submucosal plexus
mesentery
serosa
submucosa
muscularis externa layers
- outer longitudinal muscle
- inner circular muscle
mucosa
myenteric plexus
submucosal plexus
outer longitudinal muscle
inner circular muscle
the serosa is continuous with the ?
mesentery
outer longitudinal muscle versus inner circular muscle
- outer muscle shortens lengthens
- inner circular muscle contracts
stomach anatomy
- abdominal esophagus
- cardia
- cardial notch
- fundus
- lesser curvature
- pyloric orifice
- duodenum
- pyloric constriction
- pyloric sphincter
- pyloric canal
- pyloric antrum
- body
- greater curvature
- fundus
stomach cardia
stomach fundus
stomach pyloric orifice
stomach pyloric constriction
stomach pyloric sphincter
stomach pyloric canal
stomach pyloric antrum
stomach body
stomach functions
- storage
- mixing
- digestion
where are interstitial cells of cajal located
fundus
interstitial cells of cajal
- pacemaker cells
- 3 per minute
in which region does major mixing in the stomach happen
pyloric
mucosal linings of the stomach
- oxyntic mucosa
- pyloric gland area
gastric gland definition
cells for gastric secretion
how much gastric juice is produced per day
2 liters
oxyntic mucosa
pyloric gland area
gastric pit
gastric glands
types of exocrine secretory cells
- exocrine cells
- mucous cells
- chief cells
- parietal cells
types of endocrine/paracrine secretory cells
- enterochromaffin-like (ECL) cells
- G cells
- D cells
mucous cell purpose
- produce alkaline mucus
- protects against enzymes
- neutralizes acidic content
chief cell purpose
- produce pepsinogen (enzyme precursor)
- protein digestion
parietal cell purpose
- hydrochloric acid
- activates pepsinogen for protein digestion
- produce intrinsic factor
- absorbs vitamins (mainly B12)
enterochromaffin-like (ECL) cell purpose
produce histamines that produce HCl for parietal cells
G cell purpose
- produce gastrin
- stimulate chief, parietal, and ECL cells
D cell purpose
- produce somatostatin
- inhibits parietal, ECL, and G cells
G cell location
pyloric gland area
D cell location
pyloric gland area
parietal cell location
oxyntic mucosa
chief cell location
oxyntic mucosa
mucous cell location
oxyntic mucosa
mucosal barrier function
protection of gastric mucosa
mucosal barrier
secretion of mucous and HCO3 by epithelial cells to form a barrier that protects stomach from low pH and digestion by pepsin
gastric mucosal barrier lines of defense to protect from self-injury
3 parts of the small intestine
- duodenum
- jejenum
- ileum
primary site of absorption
small intestine
villi definition and function
- tiny hair-like projections that line the inside of the small intestine
- increase surface area 10x to increase absorption
microvilli increase surface area by __x
20
duodenum
jejenum
ileum
types and function of membrane bound enzymes in villi
types:
- enteropeptidase
- disaccharidases
- aminopeptidases
function:
- carbohydrate and protein digestion
villi epithelial cell
villi central lacteal location and function
villi capillaries
large intestine parts
- appendix
- cecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
- rectum
(large intestine) appendix
(large intestine) cecum
(large intestine) ascending colon
(large intestine) transverse colon
(large intestine) descending colon
(large intestine) sigmoid colon
(large intestine) rectum
gastrointestinal accessory glands
- salivary glands
- submandibular glands
- sublingual glands
- pancreatic secretions
salivary glands
- parotid gland
- parotid duct pierces buccinator and secretes a serous secretion
- produce amylase
where does the parotid duct drain
into cheek opposite maxillary 2nd molar (parotid papilla)
amylase
digestive enzyme
submandibular glands
- hook shaped with superficial and deep arms
- submandibular duct
- merges from deep part to open on sublingual papilla
- runs over lingual nerve
lingual frenum
sublingual fold
sublingual papilla
submandibular duct
submandibular gland
sublingual glands
- almond-shaped glands lateral to the submandibular duct
- sublingual duct drains into oral cavity via several minor ducts
sublingual gland
small ducts of sublingual gland
type of secretion produced by submandibular glands
mixed mucous and serous secretion
type of secretion produced by sublingual glands
mixed mucous and serous secretion (predominantly mucous)
pancreatic gland types
- exocrine
- endocrine
exocrine pancreatic secretions
- enzymes (proteolytic enzymes, pancreatic amylase, pancreatic lipase)
- bicarbonate
endocrine pancreatic secretions
- insulin
- glucagon
- hormones
exocrine pancreatic cells
- duct cells
- acinar cells
pancreas duct cell purpose
neutralize acid
pancreas acinar cell purpose
enzymes assist in digestion
liver is the …
destination of absorbed materials
absorbed nutrient path
nutrients absorbed into blood –> hepatic portal vein –> liver
peristalsis definition
wave of contraction
basic electrical rhythm (peristalsis) definition
sets up a wave of contraction in the muscularis externa
segmentation
muscular activity that divides and mixes the chyme by alternating between backward and forward movement of the gastrointestinal tract (GI) contents
pacemaker cells of the stomach
interstitial cells of cajal
teniae coli
- 3 longitudinal bands of muscle
- scrunch to form haustra
haustra
pouches or sacs
what is mainly responsible for colonic motility
haustral contractions
haustral contraction characteristics
- slow
- nonpropulsive
what initiates haustral contractions
basic electrical rhythym
defecation reflex
- feces move into and distend rectum, stimulating stretch receptors. receptors transmit signals along afferent fibers to spinal cord neurons
- spinal reflex initiated (parasympathetic motor fibers stimulate contraction of the rectum and sigmoid colon and relaxation of the internal anal sphincter)
- voluntary motor neurons inhibited when it is convenient to defecate allowing external anal sphincter to relax for feces to pass
*voluntary raising intra-abdominal pressure and relaxing external sphincter permits defecation
continence
defecation delayed by contraction of external sphincter