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Digestive system physiology mind map
Mind map about the physiology of the digestive system, a detailed combing of the physiological knowledge of the digestive system, including an overview of the digestive system, digestion and swallowing in the mouth, digestion in the stomach, digestive function of the liver and other physiological functions.
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Digestive system physiology mind map
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- Outline
digestive system physiology
Digestive System Overview
basic skills
Digestion
The process by which food is broken down into absorbable small molecules in the digestive tract
mechanical digestion
chemical digestion
absorb
The process by which digested nutrients pass through the mucous membrane of the digestive tract and enter the blood or lymph fluid.
excrete certain nutrients
Six major categories of substances that the human body needs to obtain from the outside world
protein
Fat
carbohydrate
vitamins
Inorganic salt
water
Innervation and functions of the digestive tract
external nerves
Sympathetic nerve
Release NA/NE and inhibit digestive tract smooth muscle
parasympathetic nerve
Submucosal nerve plexus (Mellow's)
Myenteric plexus (Euclidean)
Release ACh and VIP to excite the smooth muscles of the digestive tract
intrinsic nerves
secretion function of digestive system
alpha cells
islet
glucagon
beta cells
islet
insulin
delta cells
Pancreas, stomach, small intestine, large intestine
somatostatin
It is secreted by the delta cells of the gastrointestinal mucosa. After secretion, it acts on parietal cells, enterochromaffin-like (ECL) cells, and G cells in a paracrine manner, and has a strong inhibitory effect on gastric secretion and movement.
G cells
Gastric antrum, duodenum
gastrin
Promote the secretion of gastric acid and pepsin, contract the gastric antrum and pyloric sphincter, delay gastric emptying, and promote gastrointestinal motility and intestinal epithelial growth (gastrin can both promote gastric motility and pyloric sphincter contraction, but the latter has a more powerful effect Strong, so overall gastric emptying is delayed)
I cells
upper small intestine
Cholecystokinin (trypsin)
Stimulate pancreatic juice secretion and gallbladder contraction, enhance small and large intestine motility, inhibit gastric emptying, enhance pyloric sphincter contraction, relax ampullae sphincter, and promote the growth of the exocrine pancreas
K cells
upper small intestine
gastric inhibitory peptide
Stimulates insulin secretion, inhibits gastric acid and pepsin secretion, and inhibits gastric emptying
Mo cells
small intestine
Motilin
Stimulates gastric and small intestinal motility during digestion
N cells
ileum
neurotensin
PP cells
Pancreatic islets, exocrine pancreas, stomach, small intestine, large intestine
pancreatic polypeptide
S cells
upper small intestine
secretin
Stimulates HCO3- secretion in pancreatic juice and bile, inhibits gastric acid secretion and gastrointestinal motility, contracts pyloric sphincter, inhibits gastric emptying, and promotes the growth of the exocrine pancreas
Intraoral digestion and swallowing
secretion of saliva
Chewing (feedforward reflex)
swallow
digestion of stomach
gastric secretion
cardia gland
Mucous glands located at the gastroesophageal junction
oxyntic gland
It is a mixed gland located in most of the fundus of the stomach and the entire body of the stomach.
parietal cell
Secrete gastric acid, intrinsic factor
chief cell
secrete pepsinogen
cervical mucus cells
Secrete mucus and glycoproteins
Pyloric gland
Secretes alkaline mucus, located in the pylorus
Properties, components and functions of gastric juice
Pure gastric juice is a colorless acidic liquid with a pH of 0.9-1.5. Normal adults secrete 1.5-2.5L per day.
Hydrochloric acid (stomach acid)
The mechanism of gastric acid secretion
Relying on the proton pump in the secretory tubule membrane at the top of parietal cells
During the digestive period, due to the large amount of gastric acid secretion, a large amount of HCO3- enters the blood, temporarily alkalinizing the blood, forming the so-called postprandial alkaline flush.
The role of stomach acid
Activates pepsinogen and provides an acidic environment for pepsin to work
Denature the proteins in food and facilitate proteolysis
Deactivate bacteria that enter the stomach with food
After entering the small intestine, it promotes the secretion of secretin and cholecystokinin
An acidic environment aids the absorption of iron and calcium in the small intestine
pepsinogen
Mainly synthesized and secreted by the chief cells of the gastric oxyntic gland
Pepsin hydrolyzes protein in food
Pepsin only works in an acidic environment. The most suitable pH is 1.8-3.5. When pH >5, it is completely inactive.
intrinsic factor
Parietal cells secrete gastric acid as well as intrinsic factor and glycoproteins
Combines with VitB12 entering the stomach to protect VB12 from destruction by intestinal hydrolases
If it is deficient, it will lead to VitB12 malabsorption, affect red blood cell production, and lead to megapemia.
Mucus and bicarbonate
Formation of mucus-bicarbonate barrier to protect gastric mucosa
The pH on the gastric cavity side is about 2.0
The pH on the mucosal side is about 7.0
gastric secretions during digestion
first term
gastric stage
intestinal stage
Factors affecting gastric juice secretion
Promote
vagus nerve
Release ACh to promote secretion of gastric acid from parietal cells
Releases ACh, stimulates enterochromaffin-like cell paracrine stimulation of H2 receptors, and promotes parietal cells to secrete gastric acid
Releases gastrin-releasing peptide, activates the toadherin receptor of G cells, releases gastrin, and stimulates parietal cells to secrete gastric acid
somatostatin
histamine
Secreted by enterochromaffin-like cells, it acts on the H2 receptors of adjacent parietal cells in a paracrine manner, causing the parietal cells to secrete gastric acid.
gastrin
Calcium ions, hypoglycemia, caffeine, alcohol, etc. can also stimulate gastric acid secretion
inhibition
hydrochloric acid
negative feedback mechanism
Fat
After fat and its digestion products enter the small intestine, it stimulates the small intestine to release gastrointestinal hormones, including secretin, cholecystokinin, gastric inhibitory peptide, neurotensin, and glucagon.
hypertonic solution
entero-gastric reflex
stomach movements
forms of gastric motility
tonic contraction
receptive relaxation
squirm
gastric emptying
Gastric emptying begins 5 minutes after food enters the stomach
Empty speed of three major nutrients: sugar>protein>fat
Vomit
Vomiting can be induced when the receptors at the base of the tongue, pharynx, gastrointestinal tract, common bile duct, genitourinary organs, vision and vestibular organs are stimulated
Vomiting is often preceded by symptoms such as nausea, salivation, shortness of breath, and rapid and irregular heartbeat.
Digestion in the small intestine
secretion of pancreatic juice
Properties, components and functions of pancreatic juice
Pancreatic juice is a colorless and odorless alkaline liquid with a pH of 7.8-8.4. The osmotic pressure is roughly the same as that of plasma. The daily secretion volume of adults is 1-2L.
pancreatic amylase
The hydrolysis efficiency of raw and cooked starch is very high, and the products are dextrin and maltose. Suitable pH 6.7-7.0
pancrelipase
Breaks down triacylglycerol into fatty acids, monoacylglycerol and glycerol. Suitable pH 7.5-8.5
It only works in the presence of lipid coenzyme secreted by the pancreas.
Bile salts can remove proteins on the surface of emulsified lipid droplets, and lipid coenzyme has a strong affinity for bile salt micelles, which can prevent lipase from being removed by bile salts.
Cholesterase and phospholipase A2
Trypsin and chymotrypsin
Regulation of pancreatic juice secretion
neuromodulation
Vagus nerve: too much enzyme and too little fluid
body fluid regulation
Secretin: Less enzyme, more fluid
Cholecystokinin (trypsin)
Influencing factors: protein decomposition products > sodium fatty acid > hydrochloric acid > fat > sugar = 0
secretion and excretion of bile
Properties, components and functions of bile
Bile is a colored, bitter, thick liquid. Daily secretion volume for adults is 0.8-1.0L
Bile is the only digestive juice that does not contain digestive enzymes. The most important component is bile salts, which can promote the digestion and absorption of fat.
role of bile
Promote fat digestion
Promotes the absorption of fats and fat-soluble vitamins
Neutralizes gastric acid and promotes bile secretion
Regulation of bile secretion and excretion
neuromodulation
body fluid regulation
Gastrin: It can directly promote the secretion of liver bile from liver cells, and also stimulate the secretion of gastric acid. Gastric acid acts on the duodenal mucosa to promote the release of secretin.
Secretin: mainly stimulates bile duct epithelium and has no significant effect on liver cells
cholecystokinin
bile salts
gallbladder function
Store and concentrate bile
Regulate intra-biliary pressure and discharge bile
secretion of small intestine
Properties, components and functions of small intestinal juice
Small intestinal fluid is weakly alkaline with a pH of about 7.6. Its osmotic pressure is equivalent to that of plasma, and it secretes 1-3L per day.
It can dilute digestive products to reduce their osmotic pressure and facilitate absorption.
Regulation of intestinal juice secretion
Mechanical stimulation of chyme
Gastrin, secretin, cholecystokinin, vasoactive intestinal peptide, etc. all promote
small intestine movements
tonic contractions,
segmented movement
squirm
Digestive function and other physiological functions of the liver
Functional characteristics of the liver
liver blood supply
Equivalent to 14% of the total blood volume of the human body, and the adult liver blood flow reaches 1.5-2L per minute
dual blood supply
Portal vein 3/4
Collects blood from abdominal viscera, rich in nutrients
Hepatic artery 1/4
Rich in oxygen, nourishing the liver
Liver metabolism characteristics
The main function is to metabolize three major nutrients
Liver cells contain almost all enzymes in the body
Main physiological functions of the liver
secrete bile
Function in substance metabolism
Glucose metabolism
protein metabolism
fat metabolism
vitamin metabolism
Hormone metabolism
Detoxification function
defense and immune function
Other functions
function of large intestine
secretion of large intestinal juice
Rich in mucus and HCO3-, pH8.3-8.4
The main function lies in the mucus protein in it, which can protect the intestinal mucosa and lubricate feces
Large bowel movements and defecation
large intestine movement patterns
baggy reciprocating motion
Segmented propulsion and multi-bag propulsion movement
squirm
Defecation
Bacterial activity in the large intestine
Effects of fiber in food on intestinal function
Polysaccharide fiber can combine with water to form a gel, which limits water absorption, increases stool volume, and facilitates defecation.
Fiber stimulates intestinal movement and shortens stool retention time
Fiber can reduce the proportion of calories in food and reduce the intake of energy-containing substances
absorb
Paths and sites of absorption
oral cavity
Food is generally not absorbed in the mouth
Stomach
Food is also poorly absorbed in the stomach, only ethanol and a small amount of water can be absorbed
small intestine
The adult's small intestine is 4-5 meters long, and food generally stays in the small intestine for 3-8 hours.
The small intestine is an important site of absorption
duodenum and jejunum
Absorb three major nutrients
ileum
Actively absorb bile salts and vitamin B12
the large intestine
Absorbs water and salts, generally 80-90% of Na and Cl-