Digestive System Ch. 23

hepatic portal system

*capillaries in stomach, intestines, pancreas and spleen* ----> inferior and superior mesenteric, splenic, and cystic veins ----> hepatic portal vein ----> *liver sinusoids* -----> hepatocytes ----> hepatic veins ----> IVC ---> Heart ----> body the thing about the ________ _________ ______ is that it has 2 capillary networks (in bold) and that the liver is a "detox organ" and everything that you orally ingest sees the liver first. When medicine companies make medicines they have to take this into account because the liver usually filters out a significant amount of what you ingest, so you're actually keeping less than you are taking in.

HCl

_____ has a pH of 2. Activates pepsinogen and converts it to active form pepsin. Also activates lingual and gastric lipase (which breaks down fat). converts Fe3+ to Fe 2+, which is important because we need iron to make hemoglobin.

gastrin

________ increases gastric motility and secretions.

absorption

absorbing what we take in into the blood; primarily into the small intestine.

ACh (PSNS)

acts with CCK and secretin to stimulate accessory organs

colon

aka large intestine; has four parts: ascending colon, transverse, descending, and sigmoid. there are about 800 bacterial species that reside here and help with the fermentation of food. at any given time, about 7-10 L of gas is located here.

enterogastric reflex

aka the intestinal phase of gastric function; this is when the duodenum releases CCK and secretin in response to chyme

emetic center

aka the vomiting center; located in the brainstem and monitors blood for things that shouldn't be there.

alimentary canal

also called the GI tract (gut); the continuous muscular tube that winds through the body from the mouth to the anus. the organs of this are the mouth, pharynx, esophagus, stomach, small and large intestines.

peristalsis

an involuntary process that involves alternating waves of contraction and relaxation of muscles in the organ walls. Its main effect is to squeeze food along the tract, but some mixing occurs as well.

cephalic trunk (3 branches) and superior/ inferior mesenteric arteries (and their branches)

arterial blood supply to digestive system

saliva

cleanses the mouth, dissolves food chemicals so they can be tasted, moistens food and helps compact it into a bolus, contains the enzyme *amylase* that begins the digestion of starchy foods and lingual lipase.

compaction

compacting the waste into smaller pieces

bile

contains bile acids which digest fats. made from cholesterol and about 80% of this is recycled and 20% is excreted

small intestine

duodenum, jejunum, ileum: very important for chemical digestion!! A main site for absorption. absorbs about 8 L of water a day! The lining of the ______ __________ is arranged in villi which increases surface area.

defecation

eliminates indigestible substances from the body via the anus in the form of feces.

amylase

enzyme in saliva that digests starchy foods

cephalic

first phase of gastric function; sensory

ingestion digestion absorption compaction defaction

five stages of the digestive system

oral cavity (mouth/ buccal cavity)

functions in chemical AND mechanical digestion. The salivary glands produce saliva. the only thing digested here is carbohydrates (because amylase digests starchy foods). pH of ______ is 7.0 (acidic).

gastric emptying time

how long it takes for your stomach to completely empty (usually about 4 hours-- less time if liquid and more time if fat)

stomach

important in mechanical digestion. Has gastric rugae (ridges) that allow the __________ to stretch out with food (gives it room to grow). The ________ wall has three layers of muscle instead of the typical 2 (inner oblique, circular, longitudinal)

LES

important sphincter open during peristalsis then closes once food is there so food doesn't come back up. This is what is wrong with people with acid reflux disease!!!

intrinsic factor

important to make B-12 (which is important for erythropoiesis)

pyloric sphincter

in the pyloric region of the stomach; closed when mechanical digestion of food is happening and then opens when food is to be moved to the small intestine.

pepsinogen

inactive until it hits the stomach HCl and then is converted to the active form pepsin.

swallowing (deglutition)

initially voluntary until the oropharynx, then it is involuntary.

mucosa

innermost layer of the alimentary canal; moist *epithelial* membrane that lines the alimentary canal from the mouth to anus. This is where good would be. This layer is the absorptive and secretory layer

long reflexes

involve CNS integration centers and autonomic nerves. The enteric nervous system sends information to the CNS via afferent visceral fibers. Generally speaking, PSNS inputs increase digestive activity and SNS impulses decrease it.

chyme

liquified food

stem cells

located at the very bottom of the epithelium. these are located here because our stomach lining only lasts 3-6 days.

body

main part of the stomach; has rugae (ridges)

parietal cells

make HCl and intrinsic factor

mucous cells (and goblet cells)

make mucus

chief cells

make pepsinogen and gastric lipase

G cells

make the hormone gastrin

pancreas (exocrine portion)

makes digestive enzymes to digest proteins, lipids, etc

NSAIDS

medicines such as ibuprofen, advil, motrin and aspirin (not the baby kind) that cause stomach ulcers

right and left hepatic ducts

merge to form one common hepatic duct

common hepatic duct and cystic duct

merge to form the bile duct, which squirts into the duodenum

ileocecal valve

opens due to the collection of chyme in the ileum (pressure)

pyloric region

part of the stomach closes to the small intestine (last part); contains the pyloric sphincter.

liver

produces BILE and secretes bilirubin

gastric

second phase of gastric function; as soon as the food hits the stomach . this is the most important phase for kicking off digestion

enteroendocrine cells

secrete the hormones gastrin and histamine. G cells are a type of these cells that make gastrin and 3 other cells are this type of cell as well that make histamine.

histamine

stimulates parietal cells to increase acid production.

bolus

swallowed food

ingestion

taking in food or water is also called what?

accessory organs

teeth, tongue, gallbladder, salivary glands, liver and pancreas

B K

the bacteria in our large intestines produce vitamins __ and __. Vitamin __ is needed for RBC formation and vitamin __ is needed for clotting.

short reflexes

the enteric nervous system has ________ ___________ that are mediated entirely by the plexuses in response to stimuli within the GI tract.

gastric pits

the epithelial lining of the stomach is arranged in ______ ____.

duodenum

the first part of the small intestine; when the pyloric sphincter opens, *3 ml* of chyme flows into this region and the _________ releases CCK and secretin in response to chyme

enteric nervous system

the in house nerve supply of the alimentary canal. Two major intrinsic nerve plexuses are located here: the Messenteric and Auerbachs plexuses (submucosal and myenteric). This system can act locally to cause muscle contraction. It has short and long reflexes and is self regulated.

muscularis externa

the layer of the alimentary canal that surrounds the submucosa; also simply called the muscularis. this layer is responsible for peristalsis and segmentation. it typically has an inner *circular layer* and an outer *longitudinal layer* of smooth muscle cells. this is helpful to contract in different ways . the *auerbach's plexus* is located here in between the circular and longitudinal muscle layers.

submucosa

the middle layer of the alimentary canal; the submucosal nerve plexus (*Meissner's plexus*) occupies this layer.

alimentary canal or accessory (digestive) organs

the organs of the digestive system fall into two main groups: those of the ____________ and the ______________

fundic region

the outer hump of the stomach.

cardiac region

the part of the stomach where the food hits first. (closest to the entry)

enterohepatic circulation

the point of this is to recycle about 80% of the bile we produce so we don't have to make more every day

CCK secretin

these hormones have these two effects: inhibiting gastric activity (telling stomach to slow down, only 3 ml at a time) and stimulating accessory organs (pancreas, liver and gallbladder)

valsalva membrane

this is what it is called when you have to go #2 and "have to strain". people often have heart attacks while doing this

inner oblique, circular and longitudinal

three layers of the stomach wall

cephalic gastric intestinal (enterogastric reflex)

three phases of gastric function

defecation

triggered by rectal stretch (stimulating of stretch receptors)

false

true or false: the stomach is the main site of absorption.

digestion

two types: mechanical (breaking down into small pieces) and chemical (breaking down chemical bonds)

500 ml

we typically lose _______ of gas a day as "flatus"

parietal cells

which cell type is affected when dealing with PPIs??

SNS

would decrease the activity of the accessory organs