Gastro Pharmacology Flashcards
What does the skeletal muscle help with?
Chewing, swallowing and defecation
What does smooth muscle do within the digestive system?
Contractions that mx and move forward contents of the gut
What is phasic smooth muscle?
Action potential induced bursts of contractions, propulsive movements and mixing movements
What is tonic smooth muscle?
Constant low level contraction, tone maintains a steady pressure on contents of gut and prevents the wall from being permanently stretched, this maintains a steady pressure to move food.
What digestive juices are secreted by exocrine glands?
Water, electrolytes, mucus, enzymes and bile salts
Does secretion require energy?
Yes to actively transport raw materials into the cell
Secretion is normally reabsorbed into the blood, True or False?
True
What are the stages in protein digestion?
1) Stomach; pepsinogen is converted to pepsin
2) Pepsin breaks down proteins to peptides,
3) Small intestine, trypsinogen in pancreatic juice is converted to trypsin at basic pH
4) Trypsin breaks down proteins to peptides
5) Peptidases are produced by the small intestine
Peptides broken down to amino acids
6) Active transport of amino acids into epithelial cells in villi,
–> to the blood and liver
What happens to fat absorbed from our diet?
Triglycerides combine with bile salts in the duodenum, fat droplets are formed and large globules are broken, lipids are broken down and absorbed.
What does lipase from the pancreas digest?
Triglycerides which are converted to monoglycerides and fatty acids
What do monoglycerides and fatty acids do?
Diffuse into epithelial cells, recombine and join proteins forming lipoproteins called chylomicrons, they then enter lacteal, and travel to the liver and other areas.
What is starch broken down to?
Pancreatic amylase to maltose
What is glycogen broken down to?
Glucose
What is cellulose broken down to in the gut?
It is NOT broken down by gut enzymes
What is the intrinsic nerve plexuses?
Enteric nervous system, which primarily coordinates local activity in the GI tract.
What types of neurons are associated with the intrinsic nerve plexuses?
*Input neurons (sensory)
*Excitatory and inhibitory output neurons, which modulate motility or secretion of hormones or enzymes
Such as
*Acetylcholine which promotes smooth muscle contraction
*NO and vasoactive intestinal peptide which act together to relax smooth muscle.
What are the extrinsic nerves?
Sympathetic and parasympathetic nerves which influence motility and secretion by modifying activity of intrinsic nerve plexus.
*Sympathetic system slows digestion
*Coordinates activity between different regions of GI tract
How do extrinsic nerves modify activity of the intrinsic nerve plexus?
*Altering secretion of GI hormones
*Directly acting on smooth muscle and glands
What does the Vagus nerve do in the parasympathetic nervous system? *Extrinsic nerves
*Increases smooth muscle motility
*Promotes GI hormone and enzyme secretion
What receptors are their in the GI tract?
*Chemoreceptors
*Mechanoreceptors
*Osmoreceptors
What are the functions of Saliva?
*Digestion - amylase
*Swallowing - moistens food
*Lubrication -mucus
*Antibacterial -lysozymes
*Solvent - stimulate taste buds
*Aids speech - lips and tongue
*Cleanliness of mouth
*Rich in bicarbonate buffers
What pushes food down the oesophagus?
Peristaltic wave
What are the three main functions of the stomach?
1) Storage
2) Secretion - HCl and enzymes that begin protein digestion
3) Mixing - food to chyme
What is the name of the barrier between the stomach and upper part of the small intestine?
Pyloric Sphincter
What factors affect gastric emptying in the stomach?
*Amount of Chyme in the stomach as it accounts for strength of contraction
What factors in the Duodenum affect gastric emptying?
*Fat - digestion only happens in small intestine, if fat is in the duodenum, there is further gastric emptying of additional fatty stomach contents is prevented
*Acid - Un-neutralised acid in the duodenum inhibits further emptying of acidic gastric contents until neutralisation can be accomplished
*Hypertonicity - inhibited when osmolarity of duodenal contents starts to rise
*Distension - too much chyme inhibits emptying of even more gastric contents = negative feedback to digest and absorb
What responses can be triggered by the factors which affect gastric emptying?
*Neural response, tells the stomach to stop pushing food through - Enterogastric reflex
*Hormonal response; release hormones into the blood stream - Enterogastrones inhibit gastric emptying
What are the TWO distinct areas of gastric mucosa that secrete gastric juice?
-Oxyntic mucosa (body and fundus lining)
-Pyloric gland area (Lines the antrum)
What are the three types of gastric exocrine secretory cells?
1) Mucous cells
-Line gastric pits and entrance glands
-Secrete thin, watery mucus
2) Chief cells
-Secrete enzyme precurser, pepsinogen
3) Parietal (Oxyntic) cells
-Secrete HCl and intrinsic factor
What are the functions of HCl?
-Activate pepsinogen to active enzyme pepsin and provide acid medium for optimal pepsin activity
-Aids in breakdown of connective tissue and muscle fibres
-Denatures protein by uncoiling
-Kills most of microorganisms ingested with food
What is the function of the gastric mucosal barrier?
Enables the stomach to contain acid without injuring itself
What do G cells secrete and what is the consequence of this?
Gastrin, this stimulates parietal, chief and ECL cells
What do ECL cells secrete and what is the consequence of this?
Histamine and this stimulates parietal cells
What do D cells release and what is the consequence of this?
Somatostatin and this inhibits parietal, G and ECL cells
What is the Cephalic phase?
Increased secretion of HCl and pepsinogen that occurs in response to stimuli acting in the head before food reaches the stomach
What is the Gastric phase?
Begins when food actually reaches the stomach.
-The presence of protein increases gastric secretions
-Presence of caffeine or alcohol can cause issues
What is the intestinal phase?
Inhibitory phase - acid, fat, hypertonicity, distension.
-helps to shut off flow of gastric juices as chyme begins to empty into the small intestine
Why is the liver important?
Bodies major biochemical factory, it is important to digestion and secretes bile salts.
What are the functions of the liver?
*Metabolic processing of carbs, proteins and lipids after absorption
*Detoxifying - drugs, waste and hormones
*Synthesises plasma proteins
*Stores glycogen, fats, iron, copper and many vitamins
*Activates vitamin D alongside the kidneys
*Removes bacteria and worn out RBC
*Produces acute phase proteins and hormones, (IGF-1)
*Excretes cholesterol and bilirubin - excretes waste products
*Produces BILE
What does bile contain?
-Bile salts
-Cholesterol
-Lecithin
-Bilirubin - breakdown from RBC
Where does bile go after eating?
Into the duodenum
What do bile salts do?
Emulsify fat into micelles
What are bile salts?
Derivatives of cholesterol, which convert large fat globules into a liquid emulsion, after participation in fat digestion and absorption most are reabsorbed into the blood.
What happens in the small intestine?
Digestion and absorption occurs
-Duodenum
-Jejunum
-Illeum
What is segmentation?
-Type of peristalsis
-Motility of the small intestine
-Ringlike contractions along length of small intestine
-Mix and Propel chyme throughout small intestine lumen
-Circular smooth muscle, influenced by distention of intestine, gastrin, extrinsic nerve activity
What aids digestion in the small intestine?
-Pancreatic enzymes
-Brush border enzymes - complete digestion of carbs and protein
-Fat is digested entirely within small intestine lumen by pancreatic lipase
Where does most absorption occur in the small intestine?
-Duodenum and Jejunum
*Absorbs everything presented to it
How is the small intestine adapted to absorption?
*Inner surface has permanent circular folds
*Villi
*Brush border - microvilli
*lining replaced about every three days
*Fat digestion undergoes transformations that enable them to be passively absorbed - eventually enter the lymph system
What is the function of the large intestine?
*Drying and storage
via
-Mass movements
-Gastrocolic reflex (gastrin, and autonomic nerves)
-Defecation reflex (Stretch receptors in rectal wall stimulated by distension - Sphincter relaxes
What is in the large intestine?
Colon, Cecum, Appendix, Rectum
Where is water extracted in the large intestine?
The colon - the remainder is eliminated via faeces
What is secreted in the large intestine?
Alkaline mucus to protect and lubricate, this helps poo to move through final stages of gut
What is absorbed here?
*Salt and water
*Vitamin K is synthesised by bacteria to break insoluble factor to small fatty acids
What is the function of the Gut Microbiome?
1) Fat storage
2) Angiogenesis
3) Training of the immune system
4) Biosynthesis of vitamins and amino acids
5) Metabolism of therapeutics
6) Modification of the nervous sytsem
7) Breaking down food compounds
8) resistance to pathogens
9) Protection against epithelial injury
10) Modulization of bone-mass density
What is excreted?
*2/3 is water
*Undigested cellulose, bilirubin, bacteria and salt
What is the myelene plexus?
Nerve fibre in the musclanis mucosa
