GI 1 Flashcards
What type of cells lubricate, protect and digest?
epithelial
How many liters of water does the GI tract absorb each day?
9-10 L
Stomach acid is what pH? what is it in the jejunum?
1 and 7
What is the function of there large intestine?
absorption of water and electrolytes, host defense, dehydration and compaction of materials for elimination
Where do organic substances and victims, host defense occur?
small intestines
What section of the GI tract does not have a smooth muscle layer?
Esophagus
What are the 4 layers of the GI tract?
inside out: mucosa, submucusa, intramural plexus, muscularis, serosa “my sub in moscow sucks”
What layer are the glands and vessels located?
submucosa- secretion! (also has blood vessels)
What are the layers of the serosa?
connective tissue layer and the peritoneum
Layers of the Mucosa?
mucous epithelium, lamina propria, muscularis mucosae (lymph nodes)
Muscularis?
Circular layer,longitudinal layer and the stomach has an oblique layer
The mesentery is what? and it contains what?
it is the outer layer of the GI tract and contains the blood vessels, nerves and extends into the serosa and muscularis
Celiac, superior mesenteric artery, inferior mesenteric artery drain into where?
Portal vein
What are the three muscular layers of the stomach
longitudinal, circular, oblique
What are the layers of the GI tract at the cellular level
MUCOSA LAYER: Mucous neck cells, parietal cells, chief cells, endocrine cells, progenitor cells
What do parietal cells secrete?
HCL and IF
What do Chief cells secrete?
Pepsinogen and gastric lipase
Regulation of the GI tract 6 components:
- Enteric nervous system (myenteric plexus, submucosal plexus for secretions)
- Parasympathetic plexus (mainly vagal to transverse colon and nerves to anus)
- Sympathetic nervous systems (post ganglionic andrenergic fibers from celiac, super and inf. mesenteric and hypogastric plexus)
- Central nervous system
- Lumenal chemo-, mechano-, and osmoreceptors (act on enteric NS)
- Hormones
Starch gets broken down down in the mouth via what and to what?
salivary amylase breaks starch down to oligosaccharides and dextrins
What happens to starches in the small intestines?
Oligosaccharides get broken down by pancreatic amylase to lactose, maltose, sucrose.
What are the brush border enzymes for starch?
lactase, maltase, sucrase, they break down the galactose, glucose, fructose.
Lactase, Maltase and Sucrase do?
Lactase: lactose to galactose and glucose
Maltase: maltose to glucose and glucose
Sucrase: sucrose to glucose and fructose
At what level of carbs breakdown can the villa of the small intestine start absorbing?
monosaccharides: galactose, fructose, glucose
Where does protein digestion start?
in the STOMACH with pepsin in the presence of hydrochloric acid. Proteins break down to peptones and proteases
In the small intestines, what happens to peptones and proteases?
Pancreatic enzymes (trypsins, chemotrypsins, carboxypeptidases) break them into small polypeptides, dipeptides.
What do the brush border enzymes of the small intestine do regarding protein breakdown?
They break the dipeptides, and polypeptides down to amino acids!
Brush border enzymes are amino peptidases and dipeptidases
At what level of protein breakdown can the small intestine absorb proteins?
at the level of amino acids.
Where does fat digestion start?
Lingual lipase in the mouth
Where does most of the fat digestion occur?
small intestine. Bile acids, fatty acids, emulsify the fats.
In addition to the small intestines breaking down fats, what other organ helps break down fats?
Also, pancreatic lipase’s also work to break them to
1. monoglycerides and fatty acids
2. glycerol and fatty acids
FATS GO INTO THE LACTEAL
Component nutrients of sugars and amino acids get absorbed where?
In the bloodstream
What is receptive relaxation and where does it occur?
STOMACH: and it vagally mediated, via the release of the VIP, vasoactive intestinal peptide; its released from neurons and inhibits HCL and stimulates pancreas to release secretions, also causes relaxation downward.
What is responsible for keeping the stomach relaxed?
VAGUS nerve!
Characteristics of the MMC
works in a fasting state movement of undigested material and bacteria into colon 3-4 phases, 75-120 mins motilin characterized by motilin independent of vagal stimulation job is gastric emptying
What is the BER?
slow waves.
Depolarization characterized by stretch, Ach/parasympathetic system, gastrin, serotonin, substance P,
Hyperpolarization: NE, sympathetics, VIP, NO
* slow in the stomach, faster in the small intestine and the large intestine
Law of intestine?
*upper end contracts and lower end relaxes
Tachykinin, motor neuron, cholinergic motor neuron can cause constriction, then VIP or a neuron can cause relaxation downstream
Via what mechanisms does peristalsis occur?
receptive relaxation, MMC, propulsion via peristalsis and segmentation (but segmentation is primarily mixing), may be mostly under extrinsic/vagal control
Contraction of the gall bladder releases what and where?
bile into the duodenum
1. vagal stimulation relaxes the sphincter of oddi and 2. later CCK will stimulate gallbladder contraction.
Characteristics of the large intestine?
Segemental propulsion, teneia coli, last absorption of Na and H2O, fast mass movements, PNS and hormonal control: GASTRIN AND CCK. BER is in the large intestine! no microvili! we don’t need to absorb as much.
Reflexes from top to bottom?
Gastroileal-
Gastrocolic
Ileogastric- inhibits gastric motility when ileum becomes full.
Enteroenteric (intestinointestinal)- inhibits intestine movement when another part of intestine is full.
Colonocolonic
*Cecoileal- irritation in cecum tells ileum to stop sending
Rectosphincteric- defecation reflex
What do parotid glands secrete?
25% of total output, with amylase
Submandibular glands?
70%, mixed
Sublingual
5%, mucous fluid
Salivary formation: how much is made, by what cells?
1.5 L a day
Acinar cells: Primary secretion (present in all three glands)
Myoepithelial cells: alpha adreneric fiber innervation (contraction puts fluid in the ducts)
Striated ducts: secrete and absorb electrolytes
Acinar cells
- Control by autonomic (parasymp.-ACh, VIP; and sympath.- beta- and alpha-adrenergics (NE)) and central nervous systems.
- Control by hormones: ADH, aldosterone,
- PTH
Secrete saliva containing amylase, Na, K, Cl, HCO3 in levels similar to plasma
Saliva must always be what?
HYPOTONIC, HCO3 is primarily absorbed in the ducts, rate of flow makes the tonicity, as rate increases osmolality increases. Makes a large volume relative to gland size, low osmolality, high K concentration .
What does saliva do?
Coagulation factors, WBC, IGA, opsonins, protects, lingula lipase and salivary lipase, mucin= glycoproteins, oral hygiene, must keep flowing!
What nerves control the salivary flow?
PNS through the glossopharyngeal and facial
What decreases salivary flow?
sympathetics, ADH aldosterone (increases K in saliva, lowers NA), sleep, dehydration, aging, drugs.
What hormones constrict the pylorus?
GIP, CCK, Secretin, Gastrin?
Movement in the small intestine is characterized by?
segmentation and peristalsis (two types of propulsion)
Segmentation contracts in the middle of the bolus, where as peristalsis contracts behind it.
Law of intestines
simulations stimulation of excitatory and inhibitory neurons
CCK does what?
tells gallbladder to release bile and tells sphincter of iddi to relax to allow contents of the common bile duct to enter the duodenum
Large intestine does what types of propulsion?
segmental (hausfrau) helps to store chyme and dehydrate and mass movements
What sphincter regulates the amount of chyme entering the colon?
ileocecal
Which hormones initiate mass movements in the colon?
CCK and gastrin
