Digestive System Flashcards
What are the 6 basic functions of the digestive system?
- Ingestion
- Secretion
- Propulsion & mixing (deglutition & peristalsis)
- Digestion (mechanical & chemical)
- Absorption
- Defecation
What are the 4 layers of the alimentary canal?
1) Mucosa
2) Submucosa
3) Muscularis
4) Serosa/ Adventitia
What are the main functions of the mucosa?
Inner layer lined with epithelial tissue
What does the mucosa do?
Lubricates the food to ease passage through the intestines
What is the submucosa?
Supports the mucosa. Made of connective tissue
What is the muscularis externa?
Provides movement
What is the serosa?
Outmost, protective layer
What does the mesentery and mesocolon do?
Binds the small intestines to the wall
What is the lesser omentum?
2 folds around stomach and duodenum suspending them from the liver
What is the greater omentum?
It folds itself twice and thus is 4 layered. Attaches itself along the stomach and duodenum, passes downward over the small intestines and upwards to the transverse colon.
What do the lips and cheeks do?
Help to keep food between teeth when chewing
What is the hard palate in the mouth?
Lies anterior, made of bone
What is the soft palate in the mouth?
Lies posterior, made of muscle
What does the tongue do?
Forms floor of the mouth, repositions and mixes food, initiates swallowing
What do the teeth do?
Tear and grind food
What is salivary amylase?
Converts starch to simple sugars
What is lingual lipase?
Starts the digestion of fat
What does deglutition mean?
Swallowing
What are the 3 stages of swallowing?
- Voluntary stage
- The pharyngeal stage
- The oesophageal stage
What happens in the voluntary stage of swallowing?
The tongue moves the bolus up and back into the oropharynx
What happens in the pharyngeal stage of swallowing?
The bolus stimulates the receptors in the oropharynx, messages travel via 2 cranial nerves to the medulla and lower pons in the brain stem. Then instructions from the motor branches cause the soft palate and uvula to move upwards closing the nasopharynx.
What happens once food passes from the oropharynx into the laryngopharynx?
The larynx is pulled forward and upward under the tongue which results in the epiglottis and vocal cords being moved thus sealing off the respiratory tract
What happens in the oesophageal stage of swallowing?
Movement through the oesophagus is almost instantaneous for fluids and 4-8 seconds for semi solid foods.
What moves food through the muscular tube?
Penstalsis
Where is the stomach located?
Upper left quadrant directly under the diaphragm, nearly hidden by liver and diaphragm
What are the functions of the stomach?
- Reservoir for food
- Production of intrinsic factor, pepsinogen, mucus, HCL and gastric
- Absorption, only water, alcohol and some drugs
- Acts as a churn due to an extra 3rd layer of muscle
- Has the enzymes to digest protein and fat, fat takes much longer to process in the stomach
What are the regions of the stomach?
- Cardia
- Fundus
- Body
- Pylorus
What is the cardia region of the stomach?
Top near oesophagus surrounding the cardiac sphincter
What is the fundus region of the stomach?
Dome - shaped part tucked under the diaphragm
What is the body region of the stomach?
Main part
What is the pylorus region of the stomach?
Funnel - shaped. Ends in the pyloric sphincter
What is the duodenum?
First part of the small intestine
What is the pancreas?
Lies behind the stomach. It is both endocrine (produces glucagon and insulin) and exocrine glands ( produces pancreatic juice)
What does the pancreatic juice flow through?
Pancreatic ducts, hepatopancreatic duct and the sphincter of Oddi into the duodenum
What does the pancreatic juice contain?
HCO3- and enzymes
What enzymes are in the pancreatic juice?
- Pancreatic amylase (for carbohydrates)
- Trypsinogen, Chymotrypsinogen, Procarboxypeptidase, Proelastase (for proteins)
- Pancreatic lipase (for fats)
- Ribonuclease, Deoxyribonuclease (for nucleic acid)
What is the gall bladder?
It is a muscular sac lined with a mucus membrane and is located behind the liver. When empty the lining folds to form rugae. It has a fundus, body and neck
What are the 2 major functions of the gall bladder?
- Storage of bile
- Bile is concentrated and mucus is added to protect the gall bladder lining
What is bile?
- It is made by hepatocytes and mainly contains waste materials from excretion e.g. bilirubin
- Bile is an alkaline and is mad continuously but at varying rates according to need
- It is highly coloured due to the presence of bilirubin, biliverdin and various salts
What are bile salts?
They are important in the small intestine for the emulsification and absorption of dietary fats
What is the liver covered by?
It is covered by by though fibrous capsule and visceral peritoneum and is held in place by ligaments
What are the 4 lobes of the liver?
- Left
- Right
- Caudate
- Quadrate
What are lobules of the liver?
Each lobe contains many ‘hexagonal, lobules. Lobules are the functional units of the liver, they contain millions of hepatocytes
What 2 large blood vessels supply the liver?
Hepatic artery and hepatic portal veins
What are kupffer cells?
They are fixed phagocytes found in the sinusoids to destroy damaged blood cells and pathogens
What are the functions of the liver?
- Carbohydrate, protein and lipid metabolism
- Nutrient inter - conversion
- Detoxification of drugs and hormones
- Recycling of erythrocytes and excretion of bilirubin
- Storage of vitamins and some minerals
- Activation of vitamin D
- Produces bile
- Produces cholesterol
What are the stages of the small intestine?
Commences with the duodenum, then the jejunum, and finally the ileum
What is mechanical digestion?
Occurs due to segmentation in which localised areas alternately contract to mix chyme with alkaline digestive juices and to present it to the mucosa.
What are the methods of transport from the small intestine into the bloodstream?
- Secondary active transport
- Facilitated diffusion
- Simple diffusion
What are the main functions of the large intestine?
- Completion of absorption for remaining water, electrolytes and vitamins
- Production of vitamins, faeces and defecation
- Secretion of mucus
- Storage of indigestible food until elimination
What is the internal sphincter?
Involuntary
What is the external sphincter?
Voluntary
What is haustral churning?
Occurs by filling of a haustrum to its maximum, followed by a haustral contraction followed by filling of a succeeding haustrum. chyme moves forwards and backwards whilst water, ions and vitamins are absorbed
What is mass production?
Forcible peristaltic movements of short duration, occurring only 3 or 4 times a day, which moves the contents from the mid colon towards the anus. It is mediated by parasympathetic autonomic motor impulses; it is often stimulated by gastric filing
What are the 3 phases of digestion?
- The cephalic phase
- The gastric phase
- The intestinal phase
What is the cephalic phase of digestion?
Where thought, sight and smell of food stimulates production of saliva and gastric juice is prepared for eating
What is the gastric phase of digestion?
Begin as food enters the stomach. Gastric juice is secreted, cardiac sphincter then closes, pyloric sphincter opens slowly after gastric churning
What is the intestinal phase?
Begins as chyme enters the duodenum slowly (to prevent overloading duodenum) prolonging stomach emptying time this is controlled by nerves and hormone, GIP.
