Flashcards in GI anatomy and physiology Deck (32):
Describe how the movement is done throughout the GI tract?
1. Peristalsis which occurs through smooth muscle that's electrically coupled to other cells
Describe the intrinsic innervation enteric nervous system?
1. Controls the motility of gastric relaxation and contraction
2. Integrates autonomic nervous system and local systems: 5-HT
3. Functions independently of any other signals (some may say part of autonomic nervous system)
What does the myenteric plexus mainly control?
Motility in GI tract
What does the submucosal plexus mainly control?
Formation of secretions and blood flow in GI tract
Describe how the intrinsic innervation autonomic innervation works in the parasympathetic and sympathetic?
1. Parasympathetic: Increases motility and secretion
- ACh acting on muscarinic to increase salivation, mucosa (lining of stomach of mucus) and constriction
2. Sympathetic reduces GI function
Noradrenaline relaxes the smooth muscle in GI
Give examples of endocrine hormones in the blood stream and what they work on?
1. Gastrin and Cholesystokinin (CCK)
2. Both work on motility and secretion
Give examples of paracrine hormones in the cell wall and what they work on?
1. Histamine and somatostatin
2. Modulate nerve action, affect secretion and motility
What is the purpose behind salvia?
1. Aids swallowing
2. Begins digestion
3. Kills bacteria
Describe how the parasympathetic and sympathetic nervous system work?
1. Parasympathetic produces watery salvia which increases secretion and blood flow
2. Sympathetic produces mixed salvia which increases secretion and decreases blood flow
Describe the process of swallowing with the last step being the stomach?
2. Peristalsis occurs through the autonomic nervous system which is aided by mucous
3. Enters stomach via oesophageal sphincter
What is the stomach lined with?
1. Rugae (epithelial cells) that contain deep gastric pits for producing acid to grind food in the stomach
2. Located in the mucosa layer
What do the parietal cells do in the stomach?
Produce gastric acid
What do the chief cells do in the stomach?
Produce pepsinogen and other digestive enzymes which break up the food in the stomach
What does the gastric fluid consist of?
3. Hydrochloric acid
4. Water and intrinsic factors
What is the importance of HCl?
1. Aids absorption of calcium and iron
2. Actives pepsinogen and optimises pepsin function
3. Aids breakdown of tissue
4. Eliminates pathogens, bacteria and viruses
Describe how stomach acid is formed in the stomach?
1. Pariental cell forms carbonic anhydrase which forms the H+ and HCO3-
2. Cl- enters which replaces the HCO3- so that it can be transported via the K+/Cl- symporter
3. Proton pump (H+/K+ ATPase) transports H+ into the stomach lumen
How is gastrin released and what is the role of it in acid secretion?
1. Released from cell from nerve, hormonal and food stimuli
2. Activates CCK2 receptors on ECL cells stimulating histamine release
What is the role of histamine in acid secretion?
Agonist on H2 receptor on pariental cells that stimulate acid secretion
What is the purpose of the gastric mucosa?
Protects stomach from acid and gastric enzyme by acting as a gel like alkaline bicarbonate
What promotes mucosal secretion?
Describe the three main gastric diseases (causes and symptoms)
1. GORD (Gastro oesophageal reflux disease)
- Symptoms: heartburn, acid reflux, indigestion or irritation to gastric mucosa
2. Gastric bleeding
- due to NSAID treatment
- caused by irritants and cancer
- Causes may be stress or certain foods
- Caused by H. pylori infection
What is the role of the stomach in gastric propulsion?
1. Stomach mixes and stores food for digestion in the intestine
2. Peristaltic waves propel food from the pyloric sphincter to the duodenum
3. Controls emptying of food depending on pH and content of food
How is drug action affected by the stomach?
Depends on the rate of emptying and the pH of the stomach
Describe how vomiting is, the symptoms and what occurs during it?
1. The sudden forceful evacuation of the contents in the stomach (and duodenum)
2. Symptoms: loss of appetite, nausea, vasoconstriction, sweating and dizziness
3. During vomiting:
- Respiratory is relaxed
- Stomach relaxes, duodenum contracts
- Diaphragm and abdominal muscles contract powerfully
What area of the brain controls the vomiting centre and what are the two main components?
1. Medulla of the brain stem
2. Chemoreceptor trigger zone (CTZ): senses enteric stimuli
3. Vomiting centre
What are the two roles played by the pancreas?
- insulin and glucagon into the blood stream
- Alkaline fluid reduces pH in the duodenum
- Digestive enzymes:
Proteolytic and Lipolytic: digestion protein and fats
3. ACh, CCK, Gastrin increases secretion and somatostatin decreases
What is the major role played by the small intestines?
The adsorption of nutrients and minerals as well as drug absorption
How are monosaccharide and amino acids absorbed?
Absorbed by the small intestine regulated by Na dependent transporters
How are fats and fat soluble vitamins absorbed ?
Micelles and bile salts
What is the role of the large intestine?
1. The storage of waste disposable/indigestible food residues before elimination by defection
2. Absorbs water and electrolytes
3. Resident bacteria form vitamins such as vitamin B12, vitamin K, Riboflavin
What is the role of mucous secretions in the large intestine?
Helps the movement of faeces easier throughout the defection period when the waste needs to be removed