Flashcards in digestive system Deck (149):
the function of the digestive system?
to transfer nutrients, water, and electrolytes from the food we eat into the bodies internal environment
What percentage of injected food is available for the bodies use?
What is motility?
refers to the motility of muscular contractions that mix and move forward the contents of the digestive tract
-includes propulsive movements and mixing movements
-propel or push contents forward
-moves food forward in a given segment at the appropriate velocity to allow that segment to perform its functions
ex. protein rich foods move more slowly through the stomach
-mix food with digestive juices (promotes digestion)
-facilitates absorbing, exposes all portions of the food contents to the absorbing surface of the digestive tract
What is secretion?
-digestive juices that are secreted into the digestive tract lumen by exocrine glands
-secretions consist of water, electrolyses, and specific organic constituents that are used for synthesis of enzymes ,bile sates, and mucus.
-requires neural or hormonal stimulation to release the secretion from plasma into digestive tract
What 3 different biochemical categories does digestion include?
what is digestion?
refers to the biochemical breakdown of structurally complex foodstuff into smaller, absorbable units by enzymes produced in the tract
The most injected form of carbohydrates are in the form of
types of carbohydrates and thier sources
starch: from plants
cellulose: found in plant walls
glycogen- body muscles (meat)
Proteins are degraded primarily into..
thier constitutes amino acids as well as few small polypeptides
-found in dairy products
Most dietary fats are in the form of
triglycerides, which consist of glycerol and 3 fatty acids
Process of fat digestion and end products?
during digestion, two fatty acid molecules split off, leaving a monoglycerdies and free fatty acids
-the end products of fat digestion are monoglycerides and free fatty acids, which are absorbable units of fat
Where does complete digestion and absorption take place?
in the small intestine
-small absorbable units along with water, electrolytes, and vitamins from the digestive tract are absorbed into the blood and lymph
what are the accessory digestive organs?
-biliary system (gall bladder and liver)
what are the digestive organs?
From inner to outer layer, what is the order of the digestive tract structure?
1) mucosa - inner layer
3) mascularis externa
4) serosa- outer layer
What layers are the in mucosa?
1) Mucosa membrane
2) Lamina propria
3) Muscularis mucosa
-serves as a protective surface
-contains exocrine gland cells for secretion of juices
-contains endocrine glands for secretion of blood-borne GI hormones
-epithelial cells- for absorbing digested nutrients
-thin layer of connective tissue
-houses GALT, which is important against the defence of disease-causing intestinal bacteria
layer of smooth muscle
outermost layer in innermost layer, lol
contains larger blood and lymph vessels
-major smooth muscle coat of digestive tube
-has two layers:
1) circular layer- contraction decreases the diameter of the lumen
2) longitudinal layer- contraction shorters tube
-together, contractile activity of these smooth muscles produces the propulsive and mixing movements
outer connective tissue
-secretes serous fluid that lubricates and prevents friction between digestive organs
0.5% electrolytes and proteins (amylase, mucus, and lysozyme)
Salivary amylase does what
it's an enzyme that breaks down carbohydrates
what does the antibacterial portion of saliva do?
contains antibacterial action by lysozymes which destroy bacteria by breaking their cell wall
What does pancreatic amylase in GHO digestion do?
Parasympathetic influences on salivary secretion?
stimulates a prompt and abundant flow of water saliva rich enzymes
sympathetic influence on salivary secretion?
stimulates elicit smaller volume of saliva, the mouth is drier than usual (during stress)
When is swallowing initiated?
-When bolus is voluntarily forced by tongue rear of mouth into the pharynx, it cannot be stopped once it has begun since that portion is involuntary "all or none response"
What are the two stages of swallowing?
1) oropharyngeal stage -voluntary
2) esophageal stage- involuntary
Openings sealed off during swallowing:
-The position of the tongue against hard plate keeps food from re-entering the mouth
-uvula is elevated against the back of the throat, which seals off the nasal passage
-epiglottis folds over closed glottis
-elevation of larynx and closure of vocal cords prevents food from entering trachea - the respiratory passage is sealed off
The esophagus contains:
contains two sphincters at each end
1) pharyngoesophageal sphincter:
-keeps entrance closed to prevent large volumes of air from entering esophagus and stomach during breathing
2) gastroesophageal sphincter:
-prevents reflux of gastic contents
What is the stomach?
A j-shaped chamber lying between the esophagus and small intestine that is divided into 3 sections
What are the three sections of the stomach and what they do?
2) body: middle/main part of stomach
3) antrum: lower part of stomach
what are the three main functions of the stomach?
1) storage of food
2) secretes HCL and enzymes that begin protein digestion
3) mixing movements that convert pulverized food into chyme
What is the Plylonic sphincter?
serves as a barrier between the stomach and upper parrt of the small intestine
What are the four aspects of gastric motility?
What does "filling" in gastric motility involve?
-involves receptive relaxation which enhances the stomachs ability to accommodate the extra volume of food with little rise in stomach pressure
-triggers act of eating
-mediated by vagus nerve
what happens when too much food is consumed?
The stomach becomes overdistended and intragastric pressure rises along with discomfort
Where does storage in the stomach take place?
in the body
where does mixing in the stomach take place?
in the antrum
What is empyting largely controlled by?
factors in the duodenum
Factors in the stomach that regulate gastric emptying
- the amount of chyme in the stomach influences the strength of contractions
factors in the duodenum that regulates gastic emptying
where does digestion and absorption of fat take place?
within the lumen of the small intestine
is fat digestest faster or slower than other nutrients?
When fat is already in the duodenum, what happens?
Further gastric emptying of additional fatty stomach contents id prevented until the small intestine has processed the fat that already exists there
what acid does the stomach secrete?
HCL, a highly acidic chyme
what does unneutralized acid int he duodenum do?
inhibits further emptying of acidic gastic contents until neutralization can be accomplished in the small intestine
How does hypotonicity (more water) influence gastic emptying?
-large amounts of water entering the intestine leads to disturbance
When osmolarity (more content) is high, gastric emptying is inhibited so that the content being digested can catch up
How does distention regulate gastric emptying?
- is too much chyme is in the duodenum, it inhibits emptying of further gastric contents so the duodenum can cope with the excess volume of chyme it already contains before it gets anymore
where in brain is vomiting controlled?
medulla of the brain stem
What is vomiting caused by?
1) deep inspiration
2) closure of glottis
what happens in body for vomiting to occur?
-contracting of diaphragm downwards on the stomach which squeezes it
-contraction of the abdominal cavity, which increases the intraabdominal pressure, the abdominal cavity is compressed from below
-Gastric contents are forced upward through relaxed sphincters and esophagus through the mouth
causes of vomiting
-tactile stimulation of back of throat (finger)
-distention or irritation of stomach
-rotation of acceleration of head
-elevated intracranial pressure
Effects of vomiting:
-loss of fluid and acid
-reduction in plasma volume
-dehydration and circulatory problem
Advantages of vomiting
-removes toxic materials from stomach
-removes affending substances from body
three factors that trigger gastric motility
1) neural response
2) hormonal response
How does the hormonal response trigger gastric motility
releases hormones such as secretion or CCK
how does sadness/fear affect gastric motility?
how does anger or aggression affect gastric motility?
how does intense pain affect gastric motility?
three types of gastric exocrine glands:
1) mucous cells
2) cheif cells
3) parietal (oxyntic) cells
what does mucous cells secrete?
thin, watery mucus
what do cheif cells secrete?
enzyme precursor: pepsinogen
what do parietal cells secrete?
HCL and intrinsic factor
what are the three phases gastric secretions?
1) cephalic phase
2) gastric phase
3) intestinal phase
What is the cephalic phase?
-refers to the increased secretion of HCL and pepsinogen that occurs in response to stimuli acting in the head before food reaches the stomach
-thinking, chewing, seeing food
What is the gastric phase?
begins when food reaches stomach
-presence of protein increases gastric secretions
what is the intestinal phase?
when the other phases are excitatory, the intestinal phase is inhibitory
helps shut off flow of gastric juices as chyme beings to empty into the small intestine
What is the pancreas and what are its endocrine and exocrine functions
- its a mixed gland that is located behind and below the stomach
Endocrine function is to secrete insulin and glucagon
Exocrine function is to secrete pancreatic juices that contain pancreatic enzymes
What are the three proteolytic enzymes?
What is pancreatic endocrine secretion regulated by?
secretin and CCK
what is trypsinogen converted to
active form of trypsin
what is chymotrypsiogen converted to
active form of chymotrysin
what is procarboxpeptidase converted to
active form of caboxpeptidase
what does pancreatic amylase do?
converts polysaccrides into the disacchoride
what is pancreatic lipase?
fat digesting enzyme secreted through entire digestive system
are the functions of the liver related to digestion?
what does the liver do?
-metabolically processes the major categories of nutrients
-detoxify body wastes, hormones, drugs, or foreign compounds
-synthesizes plasma proteins
-stores glycogen, fats, and vitamins
-removes bacteria and worn out RBCs
-Excretes cholesterol and bilirubin
What is bile actively secreted by?
the liver and is diverted to the gallbladder between meals
where is bile stored?
Where does bile go after a meal?
it enters the duodenum
What is bile made up of?
What is bile salt important for?
the digestion and absorption of fats
where to bile salts go after participation in fat digestion/
the are reabsorbed back into the blood view active transport
what is enterhepatic ciriculation?
the recycling of bile salts
What is hepatisis?
the inflammation of the liver that can result in viral infections
what is cirrhosis?
Prolonged heptatic inflammation in association with chronic alcoholism
what does the submusca and myetric plexus complete?
regulation of gut activity
What happens to fat when to stomach contents are emptied into the duodenum?
the ingested fat is collected into a large oily triglyceride droplets that float in chyme
-in the small intenstine, these droplets are dispersed into small droplets so they are exposed to a greater surface area for digestion by pancreatic lipase
productions of lipid digestion?
monoglycerides and free fatty acids
What component can facilitate absorption of fatty end products?
what are micelles?
water soluable particles that can carry end products of fat digestion within their lipid soluable interiror
What facilitales fat digestion?
Is Na absorbed passivley or acitvely?
Na passively enters the epithelial cells across the luminal border through Na+ channals or in the company of glucose or amino acids by using co-transport molecules
What does Na absportion depend on?
its electrochemical gradient from the lumen of the blood through the intestinal epitheal cells
how is water absorbed?
it is absorbed from the lumen into the villus according to the hydrostatic pressure and picked up by capillary networks
What is iron essential for?
what are the two processed of iron absorption?
1) absorption of iron from the lumen into the small intestine
2) absorption of iron from the epithieal cells into the blood
where does excess iron go?
its dumped into the ferritin pool, unused iron is lost in feces.
what are the three segments of the small intestine
motility of the small intestine includes:
2) migrating motility complex
what is the mirgrating motility complex?
weak, repetative peristaltic waves that move a short distance down the intestine that sweeps intestines clean between meals
what is segmentation?
the primary method of motility in the small intestines
refers to mixing and propelling the chyme
consists of ringlike contractions that mix chyme
what is segmentation initiated by?
a pacemaker cell in the small intestine which produces basic eletrical rhythms (BER)
frequency of segmentation follows frequency of BER
What happens when the small intestine becomes stretched with chyme?
it initiates the intestine to begin localized contractions
what is circular smooth muscle responsivness influenced by?
distention of intestine and extensic nerve activity
what are the functions of segmentation?
1) mixing chyme with digestive juices secreted into small intestine lumen
2) exposing all chyme to absoptive surfaces of small intestine mucosa
small intestine secretion contains three enzymes:
how is digestion in the small intestine accomplished?
its accomplsihed by pancreatic enzymes with fat digestion being enhanced by bile secretion
does juice secreted in small intestine contain any digestive enzymes
what are the membrane bound enzymes along the luminal surface?
they are brush -border membrane cells of the epitheal cells
what do the brush border enzymes do?
they continue carbohydrate and protein digestion
what are the adaptions that increase small intestines surface area?
-inner surface har circular folds
-microscopic finger like projections called villi
what does the large intestine consist of?
colon, cecum, appendix, booty hole
what is haustra?
pouches /sacs that actively change the location as result f contraction of circular smooth muscle
the contractions of the haustra are the main motility
what do mass movements do?
happen 3-4 times a day after each meal
moves colonic contents to distal end of the large intestine
what is the gastrocolic reflex?
mediated from stomach to colon by gastric and autonomic nerves
-most evident after first meal of the day, followed by urge to poo
What is the defecation reflex?
when a mass movement of the colon moves feces to the rectum, distention of rectum stimulates stretch receptors in the rectal wall
what pressures lead to defecation?
intra-abdominal pressure plus forcible expiration against a closed glottis
what causes constipation?
-feces that has stays in the colon for a longer period of time
-more h20 is absorbed
-causes by delayed pooping- longer than normal
symptoms of constipation?
loss of appetite
what causes the appendix to become inflammed?
hardened feces in the appendix, results in pus and tissue will start to die
what are the four factors that affects the regulation of the digestive system?
1) autonomic smooth muscle function
2) intrisnic nerve plexus
3) extrisic nerve
4) gastrointestineal homrones
What does the exteric nerve plexus consist of?
1) myenteric plexus
2) submucus plexus
what does the myenteric plexus consist of?
contains many neurons that aid digestion and self regulation
contains both sensory and local neurons that are connected with interneurons
what three sensory receptors does the digestive system include
3) osmoreceptors- sensitive to osmolarity
What does the long reflex involve?
involves pathways between CNS and digestive system
- all elements of the reflex are located within the wall of the GI tract
-coordinated by secretion in response to specific local stimulation
What does the neural and hormonal control of cephalic phase of the GI tract refer to?
refers to the increase of secretion of HCO and pepsiongen in response in head before food reaches the stomach
Food increases gastric secretion by stimuation of vagal nerve activity in two ways:
1) intrisic plexus
What does the intrisic plexus do?
promotes increases ach secretion
stimulates secretion cells to secret more HCL and pepsionogen
What do G-cells do
secretes HCL and pepsiogen
what are the hormones that control gastrointestinal activites
what causes gastrin release?
presence of proteinous foods in the stomach
what does gastrin do
-increases HCL and pepsinogen secretion, which promotes protein digestion
-enhances gastric motility
-induces mass movements in the colon
what causes secretin release?
presence of acid in the duodenum
what does secretin do
inhibits emptying to prevent acid from entering duodenum
stimulates pancreatic duct to produce a basic solution to neutralize acid
what causes CCK release?
presence of fat in duodenal muscosa
what does CCK do?
inhibits gastric motility, allowing more time for the nutrients to be digested and absorbed
-stimulates pancreatic enzmyes to be secreted
causes contraction of gall bladder and relaxation of sphichters of oddi to empty the bile into the duodenum
what does GIP do?
promotes metabolic processing of nutrients after their absorption
-stimulates insulin release by the pancreas
-promotes use and storage of newly arrived nutrients
what hormones act on the small intestine?
secretin and CCK
what does the pyloric gland area of the stomach antrum secrete?
What does secretin stimulate?
the secretion of bicarbonate
what do micelles do?
aid fat digestion through micelle formation