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Introduction to physiology with pharmacology > Gastrointestinal tract > Flashcards

Gastrointestinal tract Flashcards

(57 cards)

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1
Q

What is the general structure of the GI tract wall?

A

Long muscular tube with variations on basic structure related to function

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2
Q

What is the mucosal layer made up of?

A

Epithelial cells
Lamina propria
Muscularis mucosae

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3
Q

What is the submucosal layer?

A

Collagen
Elastin
Glands
Blood vessels

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4
Q

What is the enteric nervous system?

A

Collection of nerve plexuses surrounding the GI tract including the pancreas and biliary system
Very complex and 1/3 of the divisions of the ANS

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5
Q

How is the GI tract intrinsically and extrinsically controlled by the nervous system?

A

Intrinsic- ENS primary mechansism of ganglia in submucosal and myenteric plexuses
Extrinsic- sympathetic and parasympathetic innervation

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6
Q

What is the structure of the contractile tissue of the GI system?

A

Unitary muscle- smooth muscle cells connected by gap junctions so there is a rapid spread of APs that allow coordinated contraction

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7
Q

What acts as the GI pacemaker?

A

Interstitial cells of cajal

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8
Q

How is food broken down in the mouth?

A

Teeth and tongue mechanically break down food to be ready for swallowing
Saliva lubricates and contains a-amylase which hydrolyses starch

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9
Q

What are slow waves in terms of the GI systems motility?

A

Subthreshold membrane depolarisation and then repolarisation

Produce weak/tonic contractions

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10
Q

What is the purpose of GI tract motility?

A

Regulation of antegrade and retrograde transport

Separation of low pressure organs by sphincters

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11
Q

What are mastication muscles innervated by?

A

Madibular nerve of cranial nerve V

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12
Q

What are the three phases of swallowing?

A

Oral
Pharygeal
Oesophageal

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13
Q

What is the function of the oesophagus in digestion?

A

Swallowing reflex- closes upper oesophageal sphincter and initiates primary peristaltic wave of coordinated sequential contractions
Continued distension stimulates secondary paristaltic wave by the ENS
Lower oesophageal sphincter opening mediated by the vagus nerve releasing VIP

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14
Q

What is the first phase of motility in the stomach?

A

Receptive relaxation in thin walled orad to receive food

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15
Q

What is the second stage of motility in the stomach?

A

3 muscular layers of the caudad region contract to mix food with gastric juice from mucosal glands through ANS control which forms chyme- HCl, pepsinogen, intrinsic factor and mucus

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16
Q

What is the third stage of motility in the stomach?

A

Gastric emptying through pyloric sphincter into the small intestine- fat content and H+ slow emptying

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17
Q

What is the function of the small intestine?

A

Digestion and absorption of nutrients- carbs, amino acids, fats, water and ions
Chyme is mixed with digestive enzymes and pancreatic solutions

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18
Q

What are the three parts of the small intestine?

A

Duodenum
Jejunum
Ileum

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19
Q

How is the surface area of the small intestine increased?

A

Plicae
Villi
microvilli

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20
Q

What is the function of the pancreas as an accessory organ?

A

1L of exocrine solution secreted every day which includes:
Solution rich in HCO3- secreted from centroacinar and ductal cells to neutralise H+ delivered from the stomach
Enzymes secreted from acinar cells

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21
Q

How does the ANS control the activity of the pancreas?

A

Parasympathetic NS stimulates secretion and sympathetic NS inhibits secretion

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22
Q

What are the three stages of pancreatic secretion?

A

Cephalic
Gastric
Intestinal

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23
Q

Where is bile produced and secreted?

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A

Hepatocytes of the liver

Gall bladder stores, concentrates and ejects bile and duct secretes water + ions into it

24
Q

What are amphipathic bile salts?

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A

Major constituent of bile used for emulsification and solubilisation of lipids into micelles to aid their digestion and absorption

25
What is the function of CCK?
Secreted when chyme reaches the small intestine Contracts gall bladder Relaxes sphincter of oddi so that bile flows into the duodenum
26
What are the different types of contraction in the small intestine?
Perstaltic contractions- propel the chyme Segmentation contractions- split and expose chyme to secretions through coordinated actions, opposing in circular and longitudinal layers
27
Where does material that isn't absorbed go?
Passes through ileocaecal sphincter into the caecum of the large intestine
28
What are the three main functions of the large intestine?
Absorbs water and electrolytes (aldosterone increases Na+ absorption) Makes and absorbs vitamins K and B Forming and propelling faeces by fermenting indigestible food and bacteria to be excreted
29
What is the structure of the large intestine?
Surface columnar epithelial cells which absorb interspersed with crypts which secrete Taenia coli- 3 bands of longitudinal muscle and haustra
30
What is secreted in the mouth?
a-amylase ligual lipase kallikrein mucus
31
What is secreted in the oesophagus?
mucus | HCO3-
32
What is secreted in the stomach?
HCl Pepsinogen Intrinsic factor mucus
33
What is secreted in the small intestine?
Mucus HCO3- Receives pancreatic juice + bile
34
What is secreted in the large intesine?
Mucus
35
What are the secretory cells in the body of the stomach and what do they secrete?
``` Oxyntic glands which are made up of: Epithelial cells- HCO3- Mucous neck cells- mucus Parietal cells- HCl and intrinsic factor Chief cells- pepsinogen ```
36
What are the secretory cells of the antrum of stomach and what do they secrete?
Pyloric glands which are similar but don't have any parietal cells G cells- gastrin D cells- somatostatin
37
How is the secretion of gastric acid regulated?
Stimulation- histamine, ACh, gastrin | Inhibition- low pH, somatostatin, prostaglandins
38
Proteases
Pepsin, trypsin, chymotrypsin, elastase, carboxypeptidases
39
Carbohydrases
a-amylase, a-dextrinase, maltase, sucrase, trehelase, lactase Products are absorbed into villus blood
40
Where are the products of carbohydrases, proteases and lipases/bile salts absorbed into?
Carbohydrases and proteases- villus blood | Lipases and bile salts- lacteals within villus
41
What lipases hydrolyse lipids in the jejunum and duodenum with the help of bile salts?
Pancreatic lipase, colipase, milk lipase and other esterases
42
What are the products of lipid digestion?
Cholesterol, lysophospholipids, monoglycerides and free fatty acids solubilised in mixed micelles
43
How are lipids absorbed?
Products are re-esterified with free fatty acids in the SER Packaged into chylomicrons Cross basolateral membrane and absorbed into lacteals so glycerol can enter the blood supply
44
What are the different cells of the endocrine pancreas and what proportions are they in?
Islets- 65% beta cells, 20% alpha cells and 10% delta cells
45
What do each of the cells in the endocrine pancrease secrete?
``` beta- insulin alpha - glucagon delta- somatostatin F (PP)- pancreatic polypeptide E- ghrelin Enterochromaffin cells- substance P ```
46
Cell to cell communication in the endocrine pancreas
Gap junctions between alpha and beta cells | Delta cells send dendrite like processes to beta cells
47
What types of neurons are islet cells innervated by?
Adrenergic Cholinergic Peptidergic
48
Sympathetic activation of beta cells
B-adrenergic stimulation increases secretion | a-adrenergic stimulation inhibits seretion
49
Parasympathetic activation of beta cells
Via vagus nerve, releases ACh | Increases insulin release
50
What humoral factors regulate the secretion of insulin?
GIP Amylin Somatostatin
51
What is the structure of insulin receptor?
Heterotetramer- 2 extracellular alpha chains and 2 membrane spanning beta chains Intracellular tyrosine kinase activity
52
Intracellular signalling by insulin receptors
Receptor activated by insulin binding, autophosphorylates and phosphorylates several other proteins to activate or inhibit: PKC, phosphatases, phospholipases, G proteins Also stimulates gene transcription
53
How does insulin decrease blood-glucose concentration?
Increased glucose uptake into muscle and fat cells by GLUT4 Glycogenesis- promotes conversion of glucose into glycogen in the liver/ muscle Lipogenesis- when glycogen stores are replenished glucose is converted into fat Inhibits gluconeogenesis and glycogenolysis
54
What are the actions of insulin in the muscles?
Decreases blood amino acid concentration Anabolic effect Increasing uptake of amino acids and proteins Stimulation of protein synthesis and inhibition of degradation
55
What are the actions of insulin in adipocytes?
Increase in GLUT4 expression for rapid glucose uptake Glucose converted into FA and stored as triglycerides Increase in lipoprotein lipase which liberates FA for triglyceride synthesis Inhibition of mobilisation and oxidation of fat stores
56
Diabetes Mellitis
High blood sugar over prolonged periods Type I- insulin dependent , pancreatic islet destruction Type II- non-insulin dependent, low insulin production, peripheral insulin resistance
57
Symptoms of type I diabetes
Hyperglycaemia, increased fatty acid, ketoacid, and amino acid concentration in the blood Osmotic diuresis Polyuria Hypotension Hyperkalaemia- increased movement of K+ out of cells

Introduction to physiology with pharmacology (10 decks)

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