Chapter 24 [ EXAM #4 ] Flashcards
what is catabolism
Larger molecules broken down into smaller
what anabolism
Smaller molecules used to make larger essential molecules
what is peristalsis
involuntary, ADJACENT alternating STRONG waves of contraction and relaxation of smooth muscle to move food along
what is secretion
release of enzymes, acids, buffers, bile into GI tract
what is mastication
breaking up food into smaller pieces with teeth
incisors bite into
canines tear into
premolars chew and grind
molars chew and grind
what is absorption
passive movement of nutrients to blood or lymph
what is excretion/defection
waste, indigestible
what parts consist of the GI tract
Mouth
Pharynx
Esophagus
Stomach
Small intestines
Large intestines
what is the submucousal plexus
sensory and motor neurons, regulates activity of glands and smooth muscle in mucosa and submucosa
what is the myenteric nerve plexus
controls GI tract motility
what is the enteric nerve plexus
submucosal and myenteric nerve plexus
what are the accessory organs in the digestive system
Teeth and tongue, gallbladder
salivary glands, liver, pancreas
how does motility work in the muscularis externa
through peristalsis and segmentation
what is segmentation
NON-ADJACENT
mixes food back and forth with digestive juices / enzymes
what’s the diff between serosa and adventitia
serosa is serous membrane in peritoneal cavity
adventitia is fibrous attachment in oral cavity, pharynx, esophagus, and rectum
what are the two kinds of sensory receptors in digestive system
mechanoreceptors: stretch and pressure
chemoreceptors: chemical content, osmolarity, pH
what nervous system will enhance secretory activity and GI motility
parasympathetic NS
what’s the diff between mechanical digestion and chem digestion
mechanical = physical change through mastication and tongue movement
chemical = chemical bonds broken in mouth, stomach, and small intestines
where is MALT located and what does it do
lamina propria and protects
what is the submucousal plexus
vs.
what is the myenteric nerve plexus
submucousal plexus = regulates activity of glands and smooth muscle in mucosa and submucosa
myenteric nerve plexus = controls GI tract motility
what dat sphincter do
forward movement, prevents backflow
what do enteroendocrine cells do
produce 3 hormones
Gastrin: stomach
Secretin: small intestines
CCK: small intestines
what are the three main hormones of digestive system
where are they from and what do they do
gastrin from G cells
↑ gastric juice (pepsinogen, HCl ) and stomach motility
secretin and CCK from enteroendocrine cells
Inhibit gastrin release, ↓ gastric secretion and motility, ↑ bile pancreas
what is the function of salivary amylase
starts carb/strach breakdown
where is lingual lipase released and activated
what is its function
lingual lipase released in mouth but activated in stomach
lipid breakdown
define bolus
a solid rounded mass of food
define mucus
lubricating and protecting substance
what NS controls salivation
explain the process of salivation
parasympathetic control
stimulation of salivary nuclei
• machano- and chemo- receptors ↑ PNS activity and gland secretion
what would happen to salivation if a strong sympathetic activation occurred
dry mouth or viscous saliva
what is the composition of saliva
99.4% water
0.6% dissolved solute=
• ions, buffers, Abs, mucins, enzymes
function of saliva
lubricates mouth
moistens food
dissolves food chems to stim taste buds
start carb digestion
contain lingual lipase for lipid digestion (used in stomach)
** describe the events that take place within the three phases of deglutition (swallowing) and how they are controlled
- Voluntary (buccal) phase
• VOLUNTARY
• controlled by cerebral cortex
• bolus formed and moved toward oropharynx
- Pharyngeal phase
• INVOLUNTARY
• bolus arrives at oropharynx and stims swallowing reflex (tactile receptors)
• bolus moves towards esophagus
- Esophageal phase
• INVOLUNTARY
• peristalsis pushes bolus down esophagus
• gastroesophageal sphincter relaxes, food enters stomach
what prevents food from entering into the respiratory passages during swallowing
during pharyngeal stage
swallowing reflex as bolus contacts oropharyngeal tactile receptors
uvula closes off nasopharynx
larynx elevates and epiglottis closes
breathing temporarily inhibited
define rugae
storage of ingested food
2 - 4 hours, fats stay longer
define chyme
partially digested food mixed with gland secretions (gastric mixing)
role of pyloric sphincter
gastric emptying,
empties chyme from stomach to small intestines
what are the 5 cells in the stomach wall, their function, and location
SURFACE MUCOUS CELLS =
• alkaline mucus layer
• protection from acid and gastric enzymes
• MUCOUS NECK CELLS: produce acidic mucus
PARIETAL CELLS (exocrine) = • Secrete intrinsic factor and hydrochloric acid • Activation of pepsinogen into active pepsin (protein digestion)
CHIEF CELLS (exocrine) = • Secrete inactive pepsinogen and gastric lipase
G CELLS (endocrine) • Secrete gastrin hormone into blood
why is there little absorption in the stomach
Mucus coating
Lack of transport
Digestion not complete
Some drugs and alcohol absorbed
what’s the diff between the gastric pit and gastric glands
gastric pit = indented epithelium
gastric glands = at base of gastric pit containing parietal, chief, and G cells
what do parietal cells secrete and what’s their function
parietal cells secrete…
INTRINSIC FACTOR
• B12 absorption for maturing RBCs
HCl
• denatures proteins
• activation of pepsinogen into pepsin
what do surface mucous cells secrete and what’s their function
alkaline mucous layer
protection from acid and gastric enzymes
what do chief cells secrete and what’s their function
secrete pepsinogen to later be activated by HCl into pepsin (protein digesting enzyme)
** what two things make pepsin and what cells secrete them
HCl activates pepsinogen into active pepsin
parietal cells secrete HCl
chief cells secrete pepsinogen
what makes gastrin and what does gastrin do
g cells make gastrin
gastrin stimulates chief and parietal cells to make pepsinogen and HCl respectively
what might cause stomach (peptic) ulcers
gastritis = due to high acid / low mucous
pylori bacteria = burrows through mucous
what is gastric mixing
mix bolus with gastric juice to form chyme
what is gastric emptying
empty chyme from stomach through the pyloric sphincter
** three phases of gastric secretion
CEPHALIC
- parasympathetic NS reflex via vagus nerve
- ↑ saliva
- ↑ in gastric juice production
- ↑ contractile force (growl)
GASTRIC
- when bolus reaches stomach
- ~2/3 gastric juice secretion and ↑ mixing
- forms chyme and empties into small intestines
INTESTINAL
- Begins when chyme enters small intestines
- enterogastric reflex: protect small intestines from overload
describe enterogastric reflex
Duodenal stretch receptors and chemoreceptors
↓ PNS: ↓ gastric secretion and mixing
↑ symp. NS: contraction of pyloric sphincter
Protect sm. Intestines from overload
** importance of circular folds, villi, microvilli in small intestines
Circular folds : slows chyme down, more SA:V
Villi: velvety surface
• Absorptive and goblet cells
Microvilli: fuzzy brush-border full of enzymes for final digestion
role of CCK and secretin
account for most digestion in small intestines
what are paneth cells
enzyme defense against bacteria in small intestines
what are goblet cells
mucus cells
what happens as you move along the small intestines
fewer intestinal crypts
more goblet cells
more Peyer’s patches
what are intestinal crypts
pits between villi that contain stem cells for rapid replacement
what are brush boarder enzymes
final breakdown in digestion of proteins lipids and carbs
what is gastroileal reflex
stomach distention causes movement in sm. intestine
function of pancreas
Secrete pancreatic juice: controlled by duodenal hormones CCK and secretin and PNS
Break down all foodstuffs!
function of gallbladder
Stores and concentrates bile from liver released into cystic duct when stimulated by CCK
function of liver
Produce and excretes bile
receives nutrient rich blood coming from sm. intestines
pancreatic juice contents
Starch digestion:
Pancreatic amylase
Fat digestion:
Pancreatic lipase
Nucleic-acid digestion:
Nucleases
