GI tract Flashcards
Name the 6 functions of the GI tract.
Ingestion, mechanical procession(chewing), digestion, secretion, absorption, excretion
What is the mouth made up of?
Tongue, three pairs of salivary glands
Name the 4 functions of chewing in the mouth
- Mechanical chewing - Saliva lubricates the mouth - Saliva moistens the food (helps us taste) - Enzymes begin breaking down the starch in our food
What is the name of the enzyme in our mouth?
Salivary amylase
Where do you want the food to pass when you swallow?
Mouth, pharynx, esophagus, stomach
Where don’t you want the food to pass?
Trachea, airway
Pharynx is…
Intersection of mouth, nose, 2 ears, tear ducts,trachea and esophagus
What is protecting the trachea from food when eating?
Epiglottis
After chewing, what do we call the food now?
Bolus
What is pH is the mouth?
Slightly acidic (6.5-7)
What is the small intestine composed of?
1) Duodenum 2) Jejunum 3) Illeum
Describe the structure of the walls of the stomach
Muscular, thick walls
Is trachea or esophagus opened all the time?
Trachea
What kind of gland is the pancreas?
Exocrine, secretes something through a tube It is an endocrine gland as well (directly into the bloodstream)
Name parts of the colon
Cecum,ascending colon,transverse colon,descending colon,sigmoid colon,rectum
Name 4 sphincters in the GI tract
Cardiac sphincter, Pyloric valve, ileocecal valve,anus
The length of the small intestine
6 meters
What does coordinate swallowing and breathing in the same time
Pharynx
Explain diaphragm structure, the function and diseases
Radial muscle structure that a has a hole in the center. The hole accommodates aorta,esophagus,vena cava
The diaphragm is a thin skeletal muscle that sits at the base of the chest and separates the abdomen from the chest. It contracts and flattens when you inhale. This creates a vacuum effect that pulls air into the lungs. When you exhale, the diaphragm relaxes and the air is pushed out of lungs.
Usually diaphragm helps cardiac sphincter to close the stomach from esophagus. It relaxes when food comes to the stomach. But it can become looser-> the stomach does not close properly->acid reflux-> if not treated , cancer of esophagus. Also through the loosen diaphragm , digestive organs can go into the chest cavity and cause difficulties in breathing.
Structure of esophagus and its function
Smooth epithelial layer inside, Smooth muscle in the wall( longitudinal and circular), which we do not control . The coordinated contraction of circular and longitudinal walls->propulsion of the food down to the stomach
How many muscle layers does stomach have?
3
What is the volume of the stomach
2 liters
The difference between cardiac sphincter and pyloric valve
Cardiac sphincter has two-way flow, that is why we vomit
When pyloric valve allows only one way flow
The difference between bolus and chyme
When bolus gets into the stomach and mixes with the gastric juices , it becomes a chyme
Major functions of the stomach
- Storage of ingested food for slow release into small intestine
- Mechanical breakdown of ingested food to peristalsis to chyme (intense peristalsis in the stomach to mix it well with the juices)
- Gastrin secretion 1.Increases peristalsis, 2.HCl secretion to activate pepsinogen(enzyme precursor that is synthesized in the stomach and stored in vesicles) to pepsin( starts to cleave peptide bonds and start protein digestion)
-Production of intrinsic factor ,a glycoprotein
Intrinsic factor is
A glycoprotein that helps the absorption of vitamin B12 in the small intestine. It bonds the vitamin and carries in the blood. Some elder people stop producing the intrinsic factor( second nutrient deficiency)
What is secondary nutrient deficiency
When the problem in the body prevents the absorption of the nutrient
How the stomach protects itself from the acid?
Mucus which is produced in goblet cells
The pH in the stomach
1.5-2
What does HCl do in the stomach
1) activates enzyme precursor (pepsinogen turns to pepsin)
2) denatures the protein, opening it for pepsin
3) Bactericidal
Explain the negative feedback, happening in the stomach
Food stimulates cells to secrete gastrin
Gastrin stimulates to secrete HCL
Stomach reaches 1.5 pH
Acidity in the stomach causes the cells in the stomach stop the secretion of the gastrin
What muscles are involved in peristalsis?
Circular and Longitudinal
What does the pyloric valve do?
Keeps the food in the stomach and GRADUALLY into the duodenum
Where is gastrin produced?
Stomach
What does gastrin signal the stomach cells to do?
increase peristalsis and secrete HCL
What stimulates gastrin?
Food in the stomach
Name the 4 roles of gastrin.
1) Signals cells to increase peristalsis 2) Tells cells to secrete HCl 3) Tells other cells to secrete mucus (protect) 4)stimulate production of intrinsic factor
We have a ___ blood flow in the GI tract
huge
How does the small intestine hold? Stomach? Colon?
Small intestine: ligaments and mesentery
Stomach: lesser omentum and greater omentum
Transverse colon is held by the mesentery tissue, greater omentum
Characterize mesentery tissue, omentum
It is made of web of blood vessels,connective tissue. Has a connection to the spine. Plays a supportive and n immune function. They give a huge blood flow and support the transverse colon and not let the small intestine to twist.
Mesentery is like a tutu
Small intestines has____
Folds or plika circulares
Each fold has a ____ projection
Fingerlike
What is a crypt?
Hole in between the villi
Where is the greatest concentration of goblet cells?
Colon
What do arteries/veins do in the villus?
Artery absorbs nutrients, veins bring them to the liver give away
How long do intestinal epithelial cells live?
3 days (short but active lives)
What does the lymphatic vessel in the villus do?
high fats(monoglycerides), non soluble in H2O(fat soluble vitamins), are transported back to the heart via the thoracic duct
Where do the last steps of digestion occur?
Microvilli (brush border)
The name of the layer where folds are
Mucosa
Name 3 layers how the surface area is increased
1) plika 2)villi 3) microvilli
What stimulates secretin?
The chyme hitting the walls of the duodenum
What is the role of secretin?
Signals the pancreas to release pancreatic juice
Where is secretin released from?
Duodenum
Describe lipases, amylases, and proteases.
They are all enzymes, parts of pancreotic juice
Lipases: digests lipids
Amylases: digests starch + carbs
Proteases: proteins -> peptides
What does CCK stand for?
Cholecystokinin
What is the hormone: gastrin,CCK,secretin?
All of them. So it influences the target through the bloodstream
What stimulates CCK?
Fatty chyme
What is the role of CCK?
Signals the gallbladder to contract and release bile
Name the 3 ways nutrients can be absorbed across a cell membrane.
1) Cell diffusion (simple diffusion) 2) Facilitated diffusion 3) Active Transport
What is the pH in the small intestine?
Slightly neutral 7.5
Does pepsin still work in the duodenum?
No, it is dis-activated in the slightly neutral pH
What does bile contain?
Cholesterol,bile acids,bile salts
Where does the bile produced?
In the liver, at a constant rate, stored in the gallbladder for later use
How does the bile get into the small intestine?
through the duct
Does the bile have enzymes?
No
Which ways to absorb nutrients don’t require energy? Which do?
Energy: Active transport No energy: cell diffusion, facilitated diffusion
Which sphincter can we control?
Rectum/anus
Two types of digestion are happening in….
The lumen and on the brushborder
What molecules are absorbed by simple diffusion
Water and small lipids
What molecules are absorbed by facilitated diffusion?
some nutrients, for example,water soluble vitamins,
What is absorbed by active transport?
Amino acids and glucose
Why the final stage of digestion is on the brush border?
To make absorption easier
Why diffusion is inefficient?
It can leave a lot of glucose and other nutrients behind, because simple diffusion goes from high to low concentration. As in blood we need high concentration, simple diffusion will not go
What is the name for ‘kind of compartments’ in the large intestine
Haustras
Name the 4 functions of the colon.
Reabsorption
Transforms intestinal content -> feces
Absorption of important vitamins
Storage of fecal matter
What are the roles of microbiota?
Can influence our mood, produce vit K,folate, biotine(B7), can ferment dietary CHOs(fiber) to short fatty acids that can be used by intestinal cells as a source of energy
Autoimmune diseases, obesity
What is microbiota
ecological community of commensal,symbiotic and pathogenic microorganisms
What does the colon “lack” compared to the small intestine?
No villi
Define probiotics.
microorganisms in foods and supplements that in sufficient quantities are beneficial to health
Define prebiotics.
Foods that are undigested in the small intestine, but used as food (oligosaccharides, monosaccharides, poliols-sugar alcohols) for bacteria in the colon, stimulating their growth and activity
The structure of the colon wall
Simple columnar epithelium,intestinal crypts,goblet cells,longitudinal and circular muscles
What is the pH of the blood and the diseases in its change
- 42
- 5-alkylosis
- 3 acidoses(ketodoses)
Gastric ulcers
The mucus is washed away and the gastric juice distracts the stomach wall or the early duodenum
Caused by Helicobacter pylori. Treated with short term antibiotics
Ulcerative colitis
The damage of the smooth epithelial layer in the colom
What happens during the stage of development of a nutrient deficiency resulting from inadequate intake?
Declining nutrient stores
Abnormal functions within the body
Overt signs
Polyp is
The beginning of the potential cancer
How much water is absorbed in the small intestine vs colon
7800 ml vs 1250 ml
Do we only secrete saliva, bile and enzymes
No, we reabsorb them for later use
Dysphagia is
Swallowing difficulties when the epiglottis does not close right
Surgery can be done on loosen diaphragm to treat
GERD: gastro-esophageal reflux disease
How much time does the food spends in the mouth,stomach,small intestine and colon. How does fiber influences that?
Less than a minute in the mouth, time in stomach 1-2 hours, time in the small intestine 7-8 hours, tome in the colon 12-14 hours
Dietary fiber slows down the emptying from the stomach, but speeds up time spent in the small intestine and overall time in the gut.
The stimulus to gastrin,secretin,CCK
Gastrin-presence of foof ( peptides, aa in the gastric lumen)
Secretin-in responce to chyme in the duodenum
CCK-presence of fat in the chyme in the duodenum
where secreted gastrin,secretin,CCK
Stomach
duodenum
duodenum
Target tissue of gastrin,secretin,CCK
G-parietal cells in the stomach that secrete HCl
S-pancreas cells
C-smooth muscles of the gall bladder
What happens after gastrin,secretin and CCK influences
G- HCl secreted,peristalsis increases
S-secretion of bicarbonate into the duodenum,production of bile in the liver
C-contraction of the gallbladder,secretion of pancreotic enzymes
The effect of gastrin,secretin and CCK
g- pH lowers from 6.5 to 1.5, peristalsis mixes the food with enzymes and juices
S-pH is raised to 7.5.Pepsin stops working. Pancreotic precursors start functioning, bile synthesize
C- emulsification of lipids to simplify their digestion
