Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
403 Cards in this Set
- Front
- Back
|
The digestive system includes:
|
-the muscular digestive tract
-various accessory organs |
|
|
Organ: mechanical processing, moistening, mixing with salivary secretions
|
-oral cavity
-teeth -tongue |
|
|
Organ: storage and concentration of bile
|
Gallbladder
|
|
|
Organ: Dehydration and compaction of indigestible materials in preparation for elimination
|
large intestine
|
|
|
Organ:Muscular propulsion of materials into the esophagus
|
Pharynx
|
|
|
Organ: transport of materials into the stomach
|
Esophagus
|
|
|
Organ: Chemical breakdown of materials via acid and enzymes; mechanical processing through muscular contractions
|
Stomach
|
|
|
Organ: Enzymatic digestion and absorption of water, organic substrates, vitamins, and ions
|
Small Intestine
|
|
|
2 essential ingredients that catabolic reactions require
|
Oxygen & organic molecules such as carbohydrates, proteins, and fats
|
|
|
Functions of the GI
|
1. Ingestion
2. Mechanical processing 3. Digestion 4. Secretion 5. Absorption 6. Excretion |
|
|
Makes up the GI tract
|
1. oral cavity
2. pharynx 3. esophagus 4. stomach 5. small intestine 6. large intestine |
|
|
contain water, enzymes, buffers, and other components that assist in preparing organic and inorganic nutrients for absorption across the epithelium of the GI
|
Secretions of the glandular organs
|
|
|
glandular organs involved with the GI Tract
|
-liver
-pancreas -salivary glands -gallbladder |
|
|
an active process involving conscious choice and decision making
|
ingestion
|
|
|
occurs when materials enter the GI via the mouth
|
ingestion
|
|
|
crushing and shearing that makes materials easier to propel along the GI; increases surface area for better enzyme attack
|
mechanical processing
|
|
|
the chemical break down of food into small organic fragments suitable for absorption by the epithelium
|
digestion
|
|
|
the release of water, enzymes, acids, buffers, and salts by the epithelium of the GI and by glandular organs
|
secretions
|
|
|
the movement of organic substrates, electrolytes, vitamins, and water across the GI epithelium and into the interstitial fluid of the GI tract
|
absorption
|
|
|
removal of waste products from bodily fluids
|
excretion
|
|
|
the lining of the GI protects against:
|
1. corrosive affects of digestive acids & enzymes
2. mechanical stresses, such as abrasion 3. bacteria that are either swallowed with food or reside in the GI tract |
|
|
the abdominopelvic cavity contains: (cavity)
|
the peritoneal cavity
|
|
|
covers organs within the peritoneal cavity
|
visceral peritoneum (serosa)
|
|
|
lines the inner surfaces of the body wall within the peritoneal cavity
|
parietal peritoneum
|
|
|
continuously produce peritoneal fluid, which provides essential lubrication
|
serous membrane lining the peritoneal cavity
|
|
|
liver disease, heart failure, & kidney disease can cause:
|
an increase in the rate at which fluids move into the peritoneal cavity
|
|
|
the accumulation of fluid creates characteristic abdominal swelling
|
ascites
|
|
|
sheets of serous membranes that support portions of the digestive tract
|
mesenteries
|
|
|
lies anterior to the abdominal viscera & provides padding, protection, insulation, and energy reserves
|
greater omentum
|
|
|
the areolar tissue between the layers of the mesenteries provides:
|
access routes for the passage of blood vessels, nerves, and lymphatic vessels
|
|
|
stabilize the positions of the attached organs and prevent the intestines from becoming entangled during digestive movements or sudden changes in body position
|
mesenteries
|
|
|
stabilizes the position of the stomach and provides an access route for blood vessels and other structures entering or leaving the liver
|
lesser omentum
|
|
|
helps stabilize the position of the liver relative to the diaphragm and abdominal wall
|
falciform ligament
|
|
|
hangs like an apron from the lateral and inferior borders of the stomach
|
greater omentum
|
|
|
an inflammation of the peritoneal membrane that is painful and interferes with normal organ function
|
peritonitis
|
|
|
causes of peritonitis
|
-physical damage
-chemical irritation -bacterial invasion -untreated appendicitis (rupture) -surgeries in which the peritoneal cavity is opened -any disease or injury that perforates the walls of the stomach or intestines |
|
|
muscular tube of the GI
|
GI Tract or alimentary canal
|
|
|
contained in the GI tract
|
everything from oral cavity to anus
|
|
|
accessory organs
|
all other parts that are important to digestive processes
(liver, salivary glands, pancreas, gallbladder, hepatic portal system) |
|
|
tissue type: oral cavity & esophagus
|
stratified squamous epithelium
|
|
|
tissue type: stomach-rectum
|
simple columnar epithelium with microvilli to increase surface area
|
|
|
tissue type: rectum
|
stratified squamous
|
|
|
tissue types: end and beginning of tract
|
stratified squamous
|
|
|
tissue types: between
|
simple columnar epithelium with goblet cells
|
|
|
the major layers of the GI
|
1. mucosa
2. submucosa 3. muscularis externa 4. serosa |
|
|
mucous epithelium that lines the GI tract & is moistened by glandular secretions
|
mucosa
|
|
|
form mucosa
|
lamina propria & epithelium
|
|
|
cells that are scattered among the columnar cells & secrete hormones to coordinate the activities of the GI tract and accessory glands
|
enteroendocrine cells
|
|
|
Folds that increase surface area available for absorption
|
plicae circulares
|
|
|
the secretions of gland cells located in the mucosa and submucosa, or in accessory glandular organs are carried to the epithelia by:
|
ducts
|
|
|
Why radiation & anticancer drugs have a drastic effects on the digestive tract
|
the epithelial stem cells that usually continuously replace destroyed cells at the epithelial surface can no longer under go mitosis, which leads to cumulative damage to the epithelial lining. This causes problems with the absorption of nutrients and also exposure of the lamina propria to digestive enzymes, which can cause internal bleeding.
|
|
|
2 muscular layers of the endothelium:
|
1. visceral peritoneum
2. parietal peritoneum |
|
|
between the two layers of endothelium
|
serous fluid
|
|
|
propels food
|
peristalsis
|
|
|
ascites occurs:
|
in the greater omentum
|
|
|
type of dialysis that uses fluids from the greater omentum membrane
|
inter-peritoneal dialysis
|
|
|
layer of areolar tissue that also contains blood vessels, sensory nerve endings, lymphatic vessels, smooth muscle cells, and scattered areas of lymphoid tissue
|
lamina propria
|
|
|
In the lamina propria, narrow sheet of smooth muscle and elastic fibers
|
muscularis mucosae
|
|
|
layer of dense irregular connective tissue that surrounds the muscularis mucosae
|
submucosa
|
|
|
contains the submucosal plexus
|
submucosa
|
|
|
smooth muscle arranged in circular and longitudinal layers
|
muscularis externa
|
|
|
the cells of the muscularis externa are arranged in an inner circular layer and an outer longitudinal layer because:
|
the arrangement plays an essential role in mechanical processing and in the movement of materials along the GI
|
|
|
movements of materials along the GI tract are primarily coordinated by:
|
sensory neurons, interneurons, and motor neurons of the enteric nervous system
|
|
|
the enteric nervous system is primarily innervated by the:
|
parasympathetic division of the autonomic nervous system
|
|
|
most sympathetic postganglionic fibers innervate the:
|
mucosa and myenteric plexus
|
|
|
parasympathetic stimulation increases:
|
muscle tone and activity
|
|
|
sympathetic stimulation promotes:
|
muscular inhibition and relaxation
|
|
|
"rest and digest" division of the nervous system
|
parasympathetic nervous system
|
|
|
in most locations, the muscularis externa is covered by a serous membrane known as the:
|
serosa
|
|
|
there is no serosa covering the muscularis externa of the:
|
-oral cavity
-pharynx -esophagus -rectum |
|
|
fibrous sheath that is a dense network of collagen fibers that attaches the GI tract to adjacent structures (in place of the serosa)
|
adventitia
|
|
|
the visceral smooth muscle tissue of the GI has rhythmic cycles of activity due to the presence of:
|
pacesetter cells
|
|
|
how the pacesetter cells cause contraction of the GI's visceral smooth muscle
|
the cells undergo spontaneous depolarization, which triggers a wave of contraction that spreads through out the entire muscular sheet
|
|
|
pacesetter cells are found in the:
|
muscularis mucosae and the muscularis externa, which surround the lumen
|
|
|
waves that move a bolus
|
peristalsis
|
|
|
churn and fragment a bolus mixing it with intestinal secretions
|
segmentation
|
|
|
small oval mass of digestive contents
|
bolus
|
|
|
the activities of the digestive system are regulated by:
|
1. neural mechanisms
2. hormonal mechanisms 3. local mechanisms |
|
|
movement of materials along the digestive tract is controlled by:
|
neural mechanisms
|
|
|
in general, control relatively localized activities that involve small segments of the GI tract
|
short reflexes
|
|
|
involve interneurons and motor neurons of the CNS
|
long reflexes
|
|
|
provide a higher level of control over digestive and glandular activities, generally controlling large-scale peristaltic waves that move materials from one region of the GI tract to another
|
long reflexes
|
|
|
movement mechanism: parasympathetic and local reflexes
|
neural mechanisms
|
|
|
enhance or inhibit smooth muscle contraction
|
hormonal mechanisms
|
|
|
coordinate response to changes in pH or chemical stimuli
|
local mechanisms
|
|
|
reflexes that work mostly through the Vagus nerve (X)
|
long reflexes
|
|
|
A smell creates hunger and want for food. This is a reflexive response to food to the smell of food. What type of reflex is involved?
|
long reflex
|
|
|
involves the CNS, not local, goes to the brain and back
|
long reflex
|
|
|
The release of histamine in the lamina propria of the stomach stimulates the secretion of acid by cells in the adjacent epithelium. Which kind of control mechanism is this?
|
local
|
|
|
mechanism where chemicals such as prostaglandins or histamine that are released into the interstitial fluid which may affect adjacent cells within a small segment of the GI
|
local mechanism
|
|
|
mechanism important in coordinating a response to changing conditions, such as variations in the local pH or certain chemical or physical stimuli that affect only a portion of the tract
|
local mechanisms
|
|
|
reflex that involves one part of the GI signaling another without the signal going to the brain
|
short reflex
|
|
|
reflex that causes an increase in activity in the small intestine
|
gastroenteric reflex
|
|
|
reflex that signals that "food is on the way"
|
gastroenteric reflex
|
|
|
reflex that signals that food is coming in order to open the ileosecal valve and moves food into the colon
|
gastroileal reflex
|
|
|
reflex that occurs when chyme travels into the small intestine and signals the stomach to wait causing a decrease in stomach activity
|
interogastric reflex
|
|
|
the mouth opens into:
|
the oral/buccal cavity
|
|
|
functions of the mouth
|
-analysis of material before swallowing
-mechanical processing by teeth, tongue, and palatal surfaces -lubrication -limited digestion |
|
|
the oral cavity is lined by:
|
oral mucosa
|
|
|
make of the roof of the oral cavity
|
hard and soft palates
|
|
|
floor of the oral cavity
|
tongue
|
|
|
guards opening to the pharynx & helps prevent food from entering the pharynx prematurely
|
uvula
|
|
|
the limited digestion that the oral cavity does involves:
|
carbohydrates & lipids
|
|
|
oral mucosa tissue type
|
stratified squamous epithelium
|
|
|
Nutrients are not absorbed in the oral cavity with the exception that:
|
lipid soluble drugs, such as nitroglycerin administered for angina, can be absorbed underneath the tongue where the cells are thin enough and vascular enough to permit rapid absorption
|
|
|
manipulates materials inside the mouth and is occasionally used to bring foods (such as ice cream on a cone) into the oral cavity
|
the tongue
|
|
|
primary functions of the tongue
|
1. mechanical processing
2. assistance in chewing and swallowing 3. sensory analysis by touch, temperature, and taste receptors |
|
|
tongue movements involve:
|
1. extrinsic and intrinsic tongue muscles
2. innervation of the hypoglosal nerve |
|
|
performs all gross movements of the tongue
|
extrinsic tongue muscles
|
|
|
change the shape of the tongue and assist the during precise movements, as in speech
|
intrinsic tongue muscles
|
|
|
both intrinsic and extrinsic muscles are under control of:
|
the hypoglossal cranial nerves (N XII)
|
|
|
three pairs of salivary glands
|
1. parotid
2. sublingual 3. submandibular |
|
|
water solution of electrolytes, buffers, glycoproteins, antibodies, & enzymes
|
saliva
|
|
|
produce a serous secretion containing large amounts of salivary amylase
|
parotid glands
|
|
|
functions of saliva
|
1. lubrication
2. moistening 3. dissolving 4. initiation of digestion of complex carbohydrates |
|
|
glycoproteins of saliva that are primarily responsible for the lubricating action of saliva
|
mucins
|
|
|
parasympathetic stimulation of the salivary glands results in:
|
acceleration of salivary stimulation and large amounts of saliva production
|
|
|
increased saliva production in response to unpleasant stimuli is beneficial because...
|
it helps reduce the magnitude of the stimulus by dilution, by a rinsing action, or by buffering strong acids or bases
|
|
|
function in mastication of the bolus
|
teeth
|
|
|
number of teeth of secondary dentition
|
thirty-two
|
|
|
three layers of the teeth
|
1. enamel
2. dentin 3. root |
|
|
covers the crown of a tooth
|
enamel
|
|
|
forms the basic structure of a tooth
|
dentin
|
|
|
coated with cementum
|
root
|
|
|
hold teeth in the alveoli
|
periodontal ligaments
|
|
|
mineralized matrix similar to bone, but does not contain cells
|
dentin
|
|
|
a bony socket where the root of each tooth sits
|
alveolus
|
|
|
covers the dentin of the root, providing protection and firmly anchoring the periodontal ligament
|
cementum
|
|
|
number of primary/deciduous teeth
|
twenty
|
|
|
number of teeth of secondary dentition
|
thirty-two
|
|
|
when the periodontal ligaments and roots of the primary teeth erode until the deciduous teeth either fall out or are pushed aside
|
eruption
|
|
|
common passageway for food, liquids, and air
|
pharynx
|
|
|
lining of the pharynx
|
stratified squamous epithelium
|
|
|
muscles that assist the pharynx in swallowing
|
pharyngeal constrictor muscles & palatal muscles
|
|
|
the lamina propria of the pharynx contains:
|
scattered mucous glands and lymphoid tissue of the tonsils
|
|
|
carries solids and liquids from the pharynx to the stomach
|
esophagus
|
|
|
passes through esophageal hiatus in the diaphragm
|
esophagus
|
|
|
the wall of the esophagus contains:
|
mucosal, submucosal, and muscularis layers
|
|
|
where the esophagus enters the abdominopelvic cavity (an opening in the diaphragm)
|
esophageal hiatus
|
|
|
histology of the esophagus
|
nonkerantinized, stratified squamous epithelium
|
|
|
the mucosa and submucosa of the esophagus is...
|
folded
|
|
|
the esophagus contains a muscularis with:
|
both smooth and skeletal muscle portions
|
|
|
the esophagus lacks:
|
serosa
|
|
|
the esophagus is anchored by:
|
an adventitia
|
|
|
the folds of the esophageal mucosa and submucosa function to:
|
allow for expansion during the passage of a large bolus
|
|
|
esophageal layer mucosae that consists of an irregular layer of smooth muscle
|
muscularis mucosae
|
|
|
contains scattered esophageal glands, which produce a mucous secretion that reduces friction between the bolus and esophageal lining
|
submucosa
|
|
|
in the muscularis externa of the esophagus, the superior portion contains:
|
skeletal muscle fibers
|
|
|
in the muscularis externa of the esophagus, the middle third contains:
|
a mixture of skeletal and smooth muscle tissue
|
|
|
in the muscularis externa of the esophagus, the inferior third contains:
|
smooth muscle fibers only
|
|
|
swallowing
|
deglutition
|
|
|
phases of swallowing
|
1. buccal phase
2. pharyngeal phase 3. esophageal phase |
|
|
stomach functions
|
1. bulk storage of undigested food
2. mechanical breakdown of food 3. disruption of chemical bonds via acids and enzymes 4. production of intrinsic factor |
|
|
a glycoprotein whose presence in the digestive tract is require for the absorption of vitamin B12 in the small intestine
|
intrinsic factor
|
|
|
a viscous, highly acidic, soupy mixture of partially digested food
|
chyme
|
|
|
superior, medial portion of the stomach
|
Cardia
|
|
|
portion of the stomach superior to stomach-esophageal junction
|
Fundus
|
|
|
area between the fundus and the curve of the J
|
Body
|
|
|
antrum and pyloric canal adjacent to the duodenum
|
pylorus
|
|
|
regulates the release of chyme into the duodenum
|
pyloric sphincter
|
|
|
guards the exit from the stomach
|
pyloric sphincter
|
|
|
ridges and folds in a relaxed stomach
|
rugae
|
|
|
when the stomach is relaxed (empty), the mucosa...
|
is thrown into rugae
|
|
|
temporary features that let the gastric lumen expand
|
rugae
|
|
|
the muscularis externa of the stomach has an additional layer of smooth muscle
|
oblique layer
|
|
|
strengthen the stomach wall and assist in the mixing and churning activities essential to the formation of chyme
|
additional smooth muscle in the stomach's muscularis externa (oblique layer)
|
|
|
lines all portions of the stomach (histology)
|
a simple columnar epithelium
|
|
|
produces a carpet of mucus that covers the interior surfaces of the stomach
|
secretory sheet-epithelium of the stomach
|
|
|
protects epithelial cells against the acid and enzymes in the gastric lumen
|
secretory sheet in the stomach
|
|
|
open onto the gastric surface and replace the cells that are shed into chyme
|
gastric pits
|
|
|
each gastric pit in the stomach communicates with:
|
several gastric glands
|
|
|
extend deep into the underlying lamina propria and secrete gastric juice
|
gastric glands
|
|
|
gastric glands are dominated by two types of secretory cells
|
1. chief cells
2. parietal cells |
|
|
gastric gland cells of the stomach that secrete intrinsic factor to facilitate the absorption of vitamin B12 across the interstitial lining
|
parietal cells
|
|
|
vitamin essential for normal erythropoiesis
|
B12
|
|
|
secrete hydrochloric acid (HCl)
|
parietal cells
|
|
|
two important substances that parietal cells secrete
|
1. HCl
2. Intrinsic factor |
|
|
parietal cells do not produce HCl in the cytoplasm because...
|
HCl is such a strong acid that it would erode the secretory vesicle and destroy the cell. So, H+ and Cl- are transported independently.
|
|
|
when hydrogen ions are created within a parietal cell
|
as the enzyme carbonic anhydrase converts CO2 and water to carbonic acid (H2CO3), which then disassociates into hydrogen ions and bicarbonate ions
|
|
|
Hydrogen ions left as a result of H2CO3 disassociating are transported actively into...
|
the lumen of a gastric gland
|
|
|
the bicarbonate ions that are left as a result of carbonic acid disassociating (in a gastric gland) are...
|
ejected into the interstitial fluid through a counter-transport mechanism that exchanges intracellular bicarbonate ions for extracellular chloride ions.
|
|
|
how the chloride ions get into the lumen:
|
diffusion across the cell and through open chloride channels in the plasma membrane of the gastric gland's lumen
|
|
|
What happens to the bicarbonate ions released by parietal cells?
|
They diffuse through the interstitial fluid into the blood stream.
|
|
|
When a lot of secretion from gastric glands occurs, what occurs within the blood stream?
|
Enough bicarbonate ions enter the blood stream increasing the pH significantly.
|
|
|
the sudden influx of bicarbonate ions into the blood stream
|
alkaline tide
|
|
|
The secretory activities of the parietal cells keep the stomach contents at about what pH?
|
1.5-2.0
|
|
|
four functions of the stomach's acidic environment
|
1. the acidity of gastric juice kills most of the microorganisms ingested with food
2. acidity denatures proteins and inactivates most enzymes in food 3. acidity helps break down plant cell walls & connective tissues of meat 4. the acidic environment is essential for pepsin activation and function |
|
|
a protein-digesting enzyme secreted by chief cells
|
pepsin
|
|
|
cells most abundant near the base of a gastric gland
|
chief cells
|
|
|
gastric gland cells that secrete pepsinogen
|
chief cells
|
|
|
an inactive proenzyme secreted by chief cells
|
pepsinogen
|
|
|
acid in the gastric lumen converts...
|
pepsinogen to pepsin
|
|
|
an active proteolytic enzyme
|
pepsin
|
|
|
Pepsin functions best at what pH?
|
1.5-2.0
|
|
|
Enzymes that the stomach of infant's contain that aid in the digestion of milk.
|
rennin (chymosin) & gastric lipase
|
|
|
infant enzyme that coagulates milk proteins
|
rennin
|
|
|
infant enzyme that initiates the digestion of milk fats
|
gastric lipase
|
|
|
pyloric glands secrete:
|
a mucous secretion containing several hormones
|
|
|
gastrin is secreted by:
|
pyloric glands
|
|
|
gastrin is produced by:
|
G Cells
|
|
|
gastrin stimulates:
|
1. secretion by both parietal & chief cells
2. contractions of the gastric wall that mix and stir gastric contents |
|
|
hormone that inhibits the release of gastrin
|
somatostatin
|
|
|
superficial inflammation of the gastric mucosa that can develop after a person has swallowed drugs or alcohol, and is also associated with smoking, severe emotional or physical stress, bacterial infection, or ingestion of strongly acidic or alkaline chemicals.
|
gastritis
|
|
|
when gastritis leads to the erosion of the gastric lining
|
gastric/peptic ulcers can develop
|
|
|
enteroendocrine cells of the stomach
|
1. G cells (secrete gastrin)
2. D cells (secrete somatostatin) |
|
|
Electrical importance of H+ and Cl-
|
electrically neutral
|
|
|
hydrogen's affect on pH
|
goes down, more acidic
|
|
|
transient increase in blood, especially around the stomach
|
alkaline tide
|
|
|
during alkaline tide, oxygen delivery...
|
decreases, meaning it remains saturated on the hemoglobin-usually results in a sleepy feeling
|
|
|
what triggers binary fission?
pg 294? |
DNA replication in bacteria
|
|
|
phase that begins with the arrival of food in the stomach
|
gastric phase
|
|
|
phase that controls the rate of gastric emptying
|
intestinal phase
|
|
|
the gastric phase or gastric activity (production of acid and enzymes by the gastric mucosa) can be regulated by:
|
1. the CNS
2. short reflexes of the enteric nervous system 3. regulated by hormones of the digestive tract |
|
|
phase that begins when you see, smell, taste, or think about food
|
cephalic phase
|
|
|
the cephalic phase is directed by:
|
the CNS
|
|
|
The cephalic phase's neural output proceeds by way of the:
|
-parasympathetic division of the ANS
-vagus nerves (N X), which innervate the stomach -postganglionic parasympathetic fibers innervate the various gastric cells to increase rate of gastric juice production |
|
|
gastric contraction
|
motility
|
|
|
can exaggerate or inhibit the cephalic phase
|
emotional states:
- anger/hostility=excessive gastric secretion -anxiety/stress/fear=decreases gastric secretion and motility |
|
|
general overview of the cephalic phase
|
-long reflex & prep. for food
1. sensory input that stimulates secretion of stomach acid -increased stomach activity -increased muscular activity -increased hormone production (gastrin) 2. when food hits the stomach, it stretches and stimulates stretch receptors |
|
|
Phase that begins with arrival of food in the stomach and builds on the stimulation provided during the cephalic phase.
|
gastric phase
|
|
|
stimuli that initiate the gastric phase
|
1. distention of the stomach
2. an increase in the pH of the gastric contents 3. the presence of undigested materials in the stomach, especially proteins & peptides |
|
|
mechanisms of the gastric phase
|
1. neural response
2. hormonal response 3. local response |
|
|
overview of what occurs during the neural response of the gastric phase
|
-stretch receptors & chemoreceptors in the stomach wall are stimulated triggering short reflexes in the submucosal and myenteric plexuses
-postganglionic fibers leaving the plexuses innervate the parietal and chief cells & release of ACh stimulates their secretion - |
|
|
Enhance gastric secretion by stimulating chemoreceptors in the gastric lining
|
-proteins
-alcohol -caffeine |
|
|
the stimulation of the myenteric plexus causes:
|
mixing waves in the muscularis externa
|
|
|
stimulate the secretion of gastrin by G cells in the pyloric antrum
|
neural stimulation and the presence of peptides & amino acids in chyme
|
|
|
parietal and chief cells respond to the presence of gastrin by:
|
accelerating their rates of secretion
|
|
|
stimulates gastric secretions of the parietal and chief cells & stimulates gastric motility
|
gastrin (hormone)
|
|
|
the effect of gastrin on ____ cells is most pronounced, and the result is:
|
-parietal cells
-decline in the pH of gastric juices |
|
|
distention of the stomach wall stimulates the release of _____ in the ____
|
-histamine
-lamina propria |
|
|
optimal pH of pepsin
|
2.0
|
|
|
general overview of what is stimulated and secreted during the cephalic phase
|
1. sensory info to CNS
2. Vagus nerve to submucosal plexus 3. Mucosal cells: mucous Chief cells: pepsinogen Parietal cells: HCl (+partly digested peptides) G cells: gastrin |
|
|
distention activates which receptors?
|
stretch receptors
|
|
|
elevated pH activates which receptors?
|
chemoreceptors
|
|
|
the source of histamine released in response to stretch receptors is thought to come from...
|
mast cells in the connective tissue
|
|
|
how histamine stimulates acid secretion:
|
once released, histamine binds to receptors on the parietal cells
|
|
|
stimulates contractions in the muscularis externa of the stomach and intestinal tract
|
gastrin
|
|
|
when contractions of the GI begin, the pH of the gastric contents is:
|
high
|
|
|
As the pH of the stomach reaches 1.5-2.0 due to thorough mixing and dilution, what occurs?
|
-the amount of undigested protein decreases
-gastrin production declines with the rates of acid and enzyme secretion by parietal and chief cells |
|
|
begins when chyme first enters the small intestine
|
intestinal phase
|
|
|
the primary function of the intestinal phase
|
to control the rate of gastric emptying to ensure that the secretory, digestive, and absorptive functions of the small intestines can proceed with reasonable efficiency
|
|
|
responses involved in the intestinal phase
|
neural & hormonal
|
|
|
During the intestinal phase, a small amount of chyme is released into the duodenum. What does this do?
|
helps to relieve some distention in the stomach, which reduces the effect of the stretch receptors in the stomach wall & triggers stretch receptors of the small intestine
|
|
|
the small release of chyme into the duodenum triggers:
|
the enterogastric reflex
|
|
|
reflex that temporarily inhibits gastrin production and gastric contraction as well as stimulating the contraction of the pyloric sphincter
|
enterogastric reflex
|
|
|
arrival of chyme with triglycerides or fatty acids in the duodenum stimulates:
|
CCK & GIP which inhibit gastric secretions of acid and enzymes and decreases the force and rate of gastric contraction
|
|
|
What role will CCK play along with GIP if a person has eaten a meal high in fat
|
Stimulate more CCK & GIP release so the food will stay in the stomach longer, flow to the duodenum more leisurely, and there will be more time for digestion of lipids
|
|
|
gastric hormone that inhibits gastric secretion of acid and enzymes
|
Cholecystokinin (CCK)
|
|
|
a drop in pH below 4.5 stimulates
|
the secretion of the hormone secretin
|
|
|
cells that secrete secretin
|
enteroendocrine cells of the duodenum
|
|
|
inhibits parietal cell and chief cell activity in the stomach
|
secretin
|
|
|
two accessory organs that secretin targets & function
|
1. pancreas: stimulates production of bicarbonate
2. liver: stimulates the secretion of bile |
|
|
the arrival of partially digested proteins in the duodenum stimulates:
|
G cells in the duodenal wall
|
|
|
The G cells of the duodenum secrete ___ which functions to___
|
-gastrin
-accelerate acid and enzyme production in the stomach |
|
|
the release of gastrin by the G cells of the duodenum is a feedback mechanism that regulates:
|
the amount of gastric processing to meet the requirements of a specific meal.
|
|
|
in general, the rate of movement of chyme into the small intestine is highest when:
|
-the stomach is greatly distended
-the meal contains relatively little protein |
|
|
stimulate gastric secretion and motility (foods)
|
alcohol and caffeine
|
|
|
preliminary digestion of proteins in the stomach is done by
|
pepsin
|
|
|
the stomach permits, for a variable period, the digestion of carbohydrates and lipids by
|
-salivary amylase
-lingual lipase |
|
|
very little absorption of nutrients, but some drugs are absorbed here
|
stomach
|
|
|
salivary amylase and lingual lipase continue to digest carbohydrates and lipids until:
|
the pH of the contents throughout the stomach falls below 4.5
|
|
|
as stomach contents become more fluid, the pH approaches __ and ___ becomes more active causing protein disassembly to begin
|
-2.0
-pepsin |
|
|
reasons why contents are digested in the stomach, but not absorbed
|
1. the epithelial cells are covered by a blanket of alkaline mucus and are not directly exposed to the chyme
2. the epithelial cells lack the correct mechanisms for transport 3. the gastric lining is relatively impermeable to water 4. digestion has not been completed by the time chyme leaves the stomach |
|
|
why meals containing large amounts of fat help decrease amount of alcohol that diffuses in the stomach
|
because alcohol is lipid soluble, and some of it will be dissolved in the fat droplets of the chyme-slowing its absorption
|
|
|
two examples of lipid soluble drugs that are absorbed across the gastric mucosa
|
1. aspirin
2. alcohol |
|
|
why lipid soluble drugs such as aspirin and alcohol can potentially cause serious damage to the mucosa
|
when these substances are absorbed across the membranes, the membrane properties are altered, and the epithelia are exposed to gastric juices and enzymes
|
|
|
carbohydrate digestion begins:
|
in the mouth, before swallowing through salivary amylase and continues after substances arrive in the stomach
|
|
|
protein digestion begins:
|
with pepsin in the stomach
|
|
|
site that "gathers" al secretions
|
duodenum
|
|
|
secretions and buffers to the small intestine are provided by:
|
-pancreas
-liver -gallbladder |
|
|
three subdivisions of the small intestine
|
1. duodenum
2. jejunum 3. ileum |
|
|
transition between the small and large intestines
|
ileosecal sphincter
|
|
|
help neutralize chyme
|
buffers secreted by the pancreas
|
|
|
a solution secreted by the liver that is stored in the gallbladder for subsequent release into the small intestine
|
bile
|
|
|
contains buffers and bile salts
|
bile
|
|
|
compounds that facilitate the digestion and absorption of lipids
|
bile salts
|
|
|
the "mixing bowl" of the small intestine
|
duodenum
|
|
|
where the bulk of chemical digestion and nutrient absorption occurs
|
jejunum
|
|
|
the longest and final segment of the small intestine
|
ileum
|
|
|
a sphincter where the ileum ends that controls the flow of material from the ileum into the cecum of the large intestine
|
ileocecal valve
|
|
|
intestinal lining that is made up of a series of transverse folds that increase the surface area
|
plicae circulares
|
|
|
difference between the plicae circulares & rugae
|
the plicae circulares are permanent and do not disappear upon filling like the rugae do
|
|
|
finger-like projections of the intestinal mucosa
|
villi
|
|
|
the lamina propria of each villus contains an extensive capillary network that serves to:
|
carry absorbed nutrients to the hepatic portal circulation for delivery to the liver, which processes the nutrients before the blood enters general circulation
|
|
|
within each villus & contains a lymphatic capillary that transports materials that cannot enter blood capillaries
|
lacteals
|
|
|
lymph from the lacteals drains into the:
|
subclavian vein
|
|
|
the functions of villi movements
|
-exposes the epithelial surfaces to the liquefied intestinal contents
-improves efficiency of absorption by quickly eliminating local differences in nutrient concentration -squeeze the lacteals, which helps move the lymph out of the villi |
|
|
integral membrane proteins located on the surfaces of intestinal microvilli that perform the important digestive function of breaking down materials that come in contact with the brush border
|
brush border enzymes
|
|
|
once epithelial cells are shed in the small intestine, they...
|
disintegrate within the lumen, releasing intracellular and brush border enzymes
|
|
|
produce copious amounts of mucus when chyme arrives from the stomach, which protects the epithelium from the acidity of chyme and also help regulate pH with bicarbonate ions
|
duodenal glands
|
|
|
primary function of the duodenum
|
receive chyme from the stomach and neutralize the acids before it can do any damage
|
|
|
has few plicae circulares with small villi
|
duodenum (because it's primary job is not to absorb, but receive and neutralize)
|
|
|
most nutrient absorption occurs before...
|
the contents reach the ileum
|
|
|
most absorption takes place within the small intestine in the:
|
jejunum
|
|
|
aggregated lymphoid nodules in the ileum, especially near the entrance to the large intestine, that contain lymphocytes which protect the small intestine from the bacteria present in the large intestine
|
Peyer patches
|
|
|
3 primary functions of intestinal juices
|
1. moisten chyme
2. help buffer acids 3. maintain digestive material in solution |
|
|
intestinal juice volume usually arrives by:
|
osmosis & secreted by intestinal glands that are stimulated by the activation of receptors in the intestinal wall
|
|
|
duodenal glands which protect the epithelial surface increase their secretions in response to:
|
1. local reflexes
2. the release of the hormones (enterocrinin) 3.parasympathetic stimulation via the vagus nerve |
|
|
the duodenal glands begin secreting during the _____phase & why?
|
-cephalic phase
-because the vagus nerve triggers the activity |
|
|
inhibits the activation of the duodenal glands
|
sympathetic stimulation
|
|
|
why duodenal ulcers are most likely caused by chronic stress?
|
because factors that promote sympathetic activation, such as stress inhibits the activities of duodenal cells, which usually prepare the small intestine for the arrival of chyme in order to protect it. Without the mucus secretions for protection, the delicate surfaces are exposed to the acid and enzymes.
|
|
|
another name for Duodenal glands
|
Brunner's glands
|
|
|
intestinal glands that produce mucus, urogastrone, and buffers
|
duodenal glands
|
|
|
Peyer's patches are located in the:
|
ileum
|
|
|
hormone secreted by duodenal glands that inhibits gastric acid production and stimulates the division of epithelial stem cells along the GI
|
Urogastrone
|
|
|
stimulates motility and secretion along the entire small intestine
|
gastroenteric reflex
|
|
|
triggers the relaxation of the ileocecal valve
|
gastroileal reflex
|
|
|
the net result of the gastroenteric and gastroileal reflexes
|
materials pass from the small intestine to the large
|
|
|
reflex initiated by stretch receptors in the stomach
|
gastroenteric reflex
|
|
|
the degree of ileocecal valve relaxation is enhanced by:
|
gastrin
|
|
|
secreted in large quantities once food enters the stomach
|
gastrin
|
|
|
penetrates the duodenal wall
|
pancreatic duct
|
|
|
the endocrine cells (islets) of the pancreas secrete: (into the blood stream)
|
-insulin
-glucagon |
|
|
the exocrine cells of the pancreas (acinar and epithelial) secrete: (into the small intestine)
|
pancreatic juice
|
|
|
an alkaline mixture of digestive enzymes, water, and ions
|
pancreatic juice
|
|
|
secrete pancreatic enzymes, which do most of the digestive work in the small intestine
|
acinar cells
|
|
|
the majority of pancreatic secretions are _____functions
|
exocrine
|
|
|
the secretory activities of the pancreas are primarily controlled by:
|
hormones form the duodenum
|
|
|
pancreatic enzymes
|
1.lipase
2.nucleases 3.chymotrypsin & trypsin 4.amylase |
|
|
releases bicarbonate ions to neutralize the acid
|
pancreas
|
|
|
from duodenum, triggers watery buffer solution with a pH of 7.5-8.0 & bicarbonate
|
secretin
|
|
|
stimulates pancreatic enzymes
|
CCK
|
|
|
a long with hormones, stimulates pancreatic enzyme release (during cephalic phase)
|
vagus nerve (N X)
|
|
|
pancreatic enzyme that is like amylase & digests carbohydrates
|
carbohydrases
|
|
|
pancreatic enzyme for lipid digestion and the release of fatty acids
|
lipase
|
|
|
pancreatic enzyme to break down RNA or DNA
|
nucleases
|
|
|
pancreatic enzymes to break proteins into individual amino acids
|
proteolytic enzymes (proteases & peptidases)
|
|
|
why proenzymes are released instead of active enzymes
|
this release protects the secretory cells in the pancreas (or stomach) from the destructive effects of their own products
|
|
|
triggers the conversion of trypsinogen to trypsin, which then activates all other enzymes
|
enteropeptidase (on brush border)
|
|
|
an inflammation of the pancreas caused by a blockage of the excretory ducts, bacterial or viral infections, ischemia, and drug reactions (alcohol)
|
pancreatitis
|
|
|
if pancreatitis occurs, and the autolysis damages islet cells, this disorder may occur
|
diabetes mellitus
|
|
|
performs metabolic and hematological regulation and produces bile
|
the liver
|
|
|
the largest visceral organ
|
the liver
|
|
|
supplies the liver with venous blood and begins in the capillaries of the esophagus, stomach, small intestine, and most of the large intestine
|
hepatic portal vein
|
|
|
liver cells
|
hepatocytes
|
|
|
liver cells that adjust circulating levels of nutrients through selective absorption and secretion
|
hepatocytes
|
|
|
the basic functional units of the liver, which contain single cell thick plates of hepatocytes
|
liver lobules
|
|
|
liver lobules unite to form:
|
the common hepatic duct
|
|
|
the common hepatic duct meets the cystic duct to form:
|
the common bile duct
|
|
|
form irregular plates arranged in spoke-like fashion
|
hepatocytes
|
|
|
within a liver lobule, sinusoids between adjacent plates empty into the:
|
central vein
|
|
|
the importance of the liver sinusoids and the lack of a basal lamina
|
creates large openings between the endothelial cells, which allow solutes as large as plasma proteins to pass out of the blood stream and into the spaces surrounding the hepatocytes
|
|
|
liver sinusoidal lining contains ___cells, which are phagocytic & also store iron, some lipids, and heavy metals absorbed by the GI
|
Kupffer cells
|
|
|
blood enters the liver sinusoids from:
|
small branches of the hepatic portal vein and hepatic artery proper
|
|
|
areas at each corner of a liver lobule
|
portal areas/hepatic triads
|
|
|
three structures of hepatic triads
|
1. branch of the hepatic portal vein
2. a branch of the hepatic artery proper 3. a small branch of the bile duct |
|
|
causes constriction of the liver's circulatory supply
|
liver diseases, like hepatitis
|
|
|
pressure in the hepatic portal system is usually:
|
low
|
|
|
a rise in the pressure of the hepatic portal system is called:
|
portal hypertension
|
|
|
portal hypertension can result in:
|
-distention and possible rupture of capillaries and veins, which can lead to bleeding
-can force fluid into the peritoneal cavity across the serosal surfaces causing ascites |
|
|
carry bile to bile ductules
|
bile canaliculi
|
|
|
lead to portal areas in the liver
|
bile ductules
|
|
|
secreted by the liver into bile canaliculi
|
bile
|
|
|
network of narrow channels between the opposing membranes of adjacent liver cells that extend outward, away from the central vein and connect with bile ductules
|
bile canaliculi
|
|
|
carry bile to the bile ducts in the nearest portal area
|
bile ductules
|
|
|
collect bile from all the bile ducts of the liver lobes
|
the right and left hepatic ducts
|
|
|
duct that leaves the liver and is formed by the right and left hepatic ducts
|
common hepatic duct
|
|
|
the bile from the common hepatic duct goes to:
|
the common bile duct
|
|
|
the common bile duct empties into:
|
either the duodenal ampulla or the cystic duct
|
|
|
duct that leads to the gallbladder
|
cystic duct
|
|
|
formed by the union of the cystic duct and the common hepatic duct
|
common bile duct
|
|
|
three general functions of the liver
|
1. metabolic regulation
2. hematological regulation 3. bile production |
|
|
the hepatic portal vein and hepatic artery are important for:
|
adequate oxygen
|
|
|
liver cells for bile making
|
hepatocytes
|
|
|
drained into the central vein
|
hepatic portal vein and artery
|
|
|
If blood glucose levels drop, hepatocytes will:
|
break down glycogen reserves and release glucose into the blood stream
|
|
|
Hepatocytes can synthesize:
|
glucose from other carbohydrates or available amino acids
|
|
|
the synthesis of glucose from other compounds
|
gluconeogenesis
|
|
|
if blood glucose levels climb, hepatocytes will:
|
remove glucose from the blood stream and either store it as glycogen or use it to synthesize lipids to be stored
|
|
|
regulates circulating levels of triglycerides, fatty acids, and cholesterol
|
liver
|
|
|
when lipid levels are high, the liver...
|
removes the lipids for storage
|
|
|
if lipid levels decline, the liver..
|
breaks down its lipid reservers and releases the breakdown products into the blood stream
|
|
|
why lip regulation in the liver occurs only after lipid levels have risen with the general circulation?
|
because most lipids absorbed by the GI bypass the hepatic portal circulation
|
|
|
removes excess amino acids from the blood stream
|
the liver
|
|
|
amino acids removed by the liver can be used for:
|
-synthesizing new proteins
-can be converted to lipids or glucose for energy storage |
|
|
During amino acid breakdown for carbohydrates or lipid conversion to get energy, the liver strips off the amino groups. This process is called:
|
deamination
|
|
|
toxic waste product formed during deamination
|
ammonia
|
|
|
how the liver neutralizes ammonia
|
by converting it to urea to be excreted by the kidneys
|
|
|
stores the fat soluble vitamins-ADEK & B12 for possible future starvation
|
liver
|
|
|
mineral storage
|
liver
|
|
|
removes and breaks down circulating drugs, limiting the duration of their effects
|
liver
|
|
|
disorder characterized by the replacement of liver lobules with fibrous tisse
|
cirrhosis
|
|
|
bile is synthesized in the _____ & is secreted in the ______
|
-liver
-lumen of the duodenum |
|
|
bile secretion is regulated by:
|
hormonal and neural mechanisms
|
|
|
bile consists mostly of:
|
-water
-some ions -bilirubin -cholesterol -bile salts (lipids) |
|
|
assist in the dilution and buffering of acids in chyme as it enters the small intestine
|
the water and ions in bile
|
|
|
synthesized from cholesterol in the liver
|
bile salts
|
|
|
most dietary lipids are not:
|
water soluble
|
|
|
why pancreatic lipase can only react with lipids at the surface of the drops
|
because it is not lipid soluble
|
|
|
the break down of lipid droplets by bile salts, which helps to improve the surface area accessible to enzymatic attack
|
emulsification
|
|
|
emulsification creates:
|
emulsion droplets
|
|
|
after digestion, these promote the absorption of lipids by the epithelium
|
bile salts
|
|
|
the cycling of bile salts from the liver to the small intestine and back is called the:
|
enterohepatic circulation of bile
|
|
|
main functions of the large intestine
|
1. reabsorb water and compact material into feces
2. absorb vitamins produced by bacteria 3. store fecal matter prior to defecation |
|
|
four areas of the colon
|
1. ascending
2. transverse 3. descending 4. sigmoid |
|
|
permit the expansion and elongation of the colon
|
haustra
|
|
|
receives material from ileum through the ileocecal valve and collects it in order to begin the compaction process
|
cecum
|
|
|
empties into the rectum
|
sigmoid colon
|
|
|
expandable organ for the temporary storage of feces
|
rectum
|
|
|
where the simple columnar epithelium changes back to stratified squamous epithelium
|
in the rectum
|
|
|
exit of the GI
|
anus
|
|
|
guards the anus, is under voluntary control
|
external anal sphincter
|
|
|
occurs when venous pressures get too high, as in straining
|
hemorrhoids due to distended veins
|
