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MRCEM Primary Exam > Lífeðlisfræði meltingarkerfisins > Flashcards

Lífeðlisfræði meltingarkerfisins Flashcards

1
Q

5 atriði sem hraða magatæmingu:

A
  • Increased food volume in the stomach
  • Gastrin
  • Motilin
  • Parasympathetic innervation (via the vagus nerve)
  • Prokinetics such as metoclopramide and erythromycin
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2
Q

8 atriði sem seinka magatæmingu:

A
  • Duodenal distension
  • Cholecystokinin
  • Secretin
  • Somatostatin
  • Vasoactive intestinal peptide (VIP)
  • Gastric inhibitory peptide (GIP)
  • Sympathetic innervation (via the coeliac plexus)
  • Pregnancy (via increased progesterone levels)
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3
Q

Hvað er gastrín og hvar er það framleitt?

A
  • Gastrin is a peptide hormone that stimulates the secretion of gastric acid from the gastric parietal cells of the stomach and aids in gastric motility.
  • It is released by G-cells in the pyloric antrum of the stomach, the duodenum and the pancreas.
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4
Q

8 hlutverk gastrins:

A
  • Stimulation of gastric parietal cells to secrete hydrochloric acid
  • Stimulation of ECL cells to release histamine
  • Stimulation of gastric parietal cell maturation and fundal growth
  • Causes gastric chief cells to secrete pepsinogen
  • Increases antral muscle mobility and promotes stomach contractions
  • Increases the rate of gastric emptying
  • Induces panceatc secretions
  • Induces emptying of the gallbladder
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5
Q

4 atriði sem stimulera losun gastrins:

A
  • Distension of the gastic antrum
  • Vagal stimulation
  • Presence of partially digested proteins in the
    stomach (most notably amino acids)
  • Hypercalcaemia (via calcium-sensing receptors)
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6
Q

7 atriði sem hamla losun gastrins:

A
  • The presence of acid (primarily HCl)
  • Somatastatin
  • Secretin
  • Gastroinhibitory peptide (GIP)
  • Vasoactive intestinal peptide (VIP)
  • Glucagon
  • Calcitonin
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7
Q

Hvar eru D frumur, hverju seyta þær og hvað gerir efnið sem þær seyta?

A
  • D-cells, or delta-cells, are somatostatin-producing cells that are found in the pyloric antrum, the duodenum, and the pancreatic islets.
  • In the stomach, somatostatin acts directly on the acid-producing parietal cells via a G-protein coupled to inhibit gastric acid secretion.
  • Somatostatin can also indirectly decrease gastric acid secretion by inhibiting the release of other hormones, including gastrin, secretin and histamine, thereby slowing the digestive process.
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8
Q

Hvað gerir somatostatin?

A
  • In the stomach, somatostatin acts directly on the acid-producing parietal cells via a G-protein coupled to inhibit gastric acid secretion.
  • Somatostatin can also indirectly decrease gastric acid secretion by inhibiting the release of other hormones, including gastrin, secretin and histamine, thereby slowing the digestive process.
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9
Q

Hverju seyta parietal frumur og hvað gerir það?

A
  • Hydrochloric acid: Kills microbes and activates pepsinogen

- Intrinsic factor: Binds to vitamin B12 and facilitates it’s absorption

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10
Q

Hverju seyta chief cells og hvað gera þau efni?

A
  • Pepsinogen: Protein digestion

- Gastric lipase: Fat digestion

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11
Q

Hverju seyta G frumur og hvað gerir það?

A

Gastrin: Stimulates gastric acid secretion

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12
Q

Hverju seyta enterochromaffin-like frumur (ECL) og hvað gerir það?

A

Histamine: Stimulates gastric acid secretion

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13
Q

Hverju seyta mucuous neck cells og hvað gera þau efni:

A

Mucous and bicarbonate: Protects stomach epithelium from acid

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14
Q

Hverju seyta D-frumur og hvað gerir það:

A

Somatostatin: Inhibits gastric acid secretion

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15
Q

4 lög gastrointestinal wall að utan og inn:

A

The gut wall that surrounds the lumen of the gastrointestinal tract is composed of four layers. Each of these layers has different tissues and functions. Moving from the outside in, these layers are:

  • Serosa (næst matnum)
  • The muscular layer
  • Submucosa
  • Mucosa
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16
Q

Hvaða lög eru í serosunni í GI og hvaða hlutverki gegna þau?

A

The serosa is the outermost layer of the gut wall. It consists of an epithelial layer that secretes serous fluid (the mesothelium) and a thin layer of connective tissue layer that reduces frictional forces generated during digestive movements.

The connective tissue layer also supplies the blood vessels and nerves for the overlying secretory cells, and acts as a binding layer that allows the whole serous membrane to adhere to organs and other structures.

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17
Q

Hvaða lag kemur í staðinn fyrir “connective tisue layer” í retroperitoneal hlutum meltingarkerfisins?

A

In the retroperitoneal regions of the gastrointestinal tract this layer is replaced by adventitia, a connective tissue layer that binds together structures rather than reduces friction between them.

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18
Q

Hvað er gastrin og hvar er því seytt, hvað gerir það?

A

Gastrin is a peptide hormone that stimulates the production of gastric acid by the parietal cells of the stomach and aids in gastric motility. It is released by G-cells in the pyloric antrum of the stomach, the duodenum, and the pancreas.

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19
Q

4 atriði sem örva losun gastrins:

A
  • Vagal stimulation (mediated by gastrin-releasing peptide)
  • Distension of the stomach
  • Presence of partially digested proteins (particularly amino acids)
  • Hypercalcaemia
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20
Q

2 atriði sem hamla losun gastrins:

A

The presence of acid (low antral pH)

Somatostatin.

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21
Q

5 aðalhlutverk gastrins:

A
  • Increases HCl secretion
  • Increases pepsinogen secretion
  • Increases intrinsic factor secretion
  • Increases gastric motility
  • Stimulates parietal cell maturation
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22
Q

Hvers vegna þurfa einstaklingar sem hafa undirgengist gastrectomiu að taka B12?

A

Intrinsic factor is essential for the absorption of the small amounts of vitamin B12 normally present in the diet from the terminal ileum. The parietal cells of the stomach produce intrinsic factor, and following a gastrectomy, the absorption of vitamin B12 will be markedly reduced, and a deficiency state will exist.

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23
Q

Hvað er secretory villous adenoma? Hvers konar elektrolyta truflunum valda þau? (2 týpur)

A

Secretory villous adenoma is a type of polyp that is mainly found in the colon but can occur anywhere within the gastrointestinal tract.

These villous adenomas can cause a depletion syndrome that is characterised by rapid dehydration, hypokalaemia, hyponatraemia, metabolic acidosis, and in severe cases, death.

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24
Q

Hvað er Auerbach´s plexus?

A

Auerbach’s plexus, which is also known as the myenteric plexus, is a group of ganglia lying in the gut wall that is responsible for the control of peristalsis.

25
Q

Hvar liggur Auerbach´s plexus sem stjórnar peristalsis í gut?

A

It lies between the circular and longitudinal muscle layers in the muscular layer of the wall. It extends throughout the entire length of the gastrointestinal tract as a linear chain of interconnected neurons. Upon stimulation, the myenteric plexus causes an increase in gut wall tone and intensity of rhythmical contractions.

26
Q

Hvað er infantile hypertrophic pyloric stenosis, hvað veldur því og hvert er algengið?

A

Infantile hypertrophic pyloric stenosis is caused by diffuse hypertrophy and hyperplasia of the smooth muscle of the antrum of the stomach. This results in narrowing of the pyloric canal, which can then easily become obstructed.

It occurs in approximately 1 in 500 live births and is more common in males than females (M:F ratio = 4:1). First-born male children are believed to have the highest risk. It can also occur in adults, albeit very rarely.

27
Q

5 aðaleinkenni infantile hypertrophic pyloric stenosis:

A
  • Onset of vomiting at 2-8 weeks of age
  • Vomiting is non-bilious and typically projectile
  • Vomiting usually occurs 30-60 minutes post feeding
  • The baby usually remains hungry after the vomiting
  • Occasionally haematemesis occurs
28
Q

Klassiskar sýrubasatruflanir í infantile hypertrophic pyloric stenosis:

A

The typical acid-base disturbance is a hypochloraemic metabolic alkalosis.

This occurs due to loss of hydrogen and chloride ions in the vomitus, decreased secretion of pancreatic bicarbonate. The increased bicarbonate ions presented to the distal tubule of the kidney results in the production of alkaline urine. Hyponatraemia and hypokalaemia are also usually present.

29
Q

Greining infantile hypertrophic pyloric stenosis:

A

The investigation of choice is ultrasound scanning, which is both reliable and easy to perform. This has now replaced barium studies as the investigation of choice.

30
Q

Meðferð infantile hypertrophic pyloric stenosis:

A

Initial management is with fluid resuscitation. This should be guided by the weight and degree of dehydration. Any electrolyte imbalance should also be corrected.

The definitive management is surgical, with the procedure of choice usually being a Ramstedt pyloromyotomy. Laparoscopic pyloromyotomy is also performed and is an effective alternative where suitable facilities are available. The prognosis is excellent unless there is a delay in diagnosis and initiation of treatment.

31
Q

Hvernig er kalk bundið í plasma? (3)

A

Approximately 50% unbound in its ionized form
Approximately 40% bound to albumin
Approximately 10% bound to other plasma proteins

32
Q

Hversu mikið af heildarkalki líkamans er geymt í beinum hverju sinni og hver er meðalinntaka fullorðinnar manneskju?

A

Approximately 99% of the body’s calcium is stored in bones, but it is also present in some cells (most notably muscle cells) and in the blood. The normal adult diet contains about 25 mmol of calcium per day, of which only about 5 mmol is absorbed by the body.

33
Q

Hvert er aðalhlutverk ileum í næringarupptöku?

A

The principal function of the ileum is to absorb vitamin B12 and bile salts. Products of digestion not absorbed by the jejenum will also be absorbed by the ileum.

34
Q

Hvað er Meissner´s plexus?

A

Meissner’s plexus is an enteric nervous plexus that acts as the main control for gastrointestinal secretion and local blood flow within the gut.

35
Q

Hvar er Meissner´s plexus staðsettur?

A

It is situated in the submucosal layer on the inner surface of the muscularis externa. The nerves of this plexus are derived from the myenteric plexus. Within the submucosal plexus, preganglionic parasympathetic neurones create synapses with the postganglionic nerve fibres that supply the muscularis mucosa.

36
Q

Hvaða áhrif hefur parasympatisk ítaugun á seyti í görnum?

A

Parasympathetic innervation promotes net secretion from the intestines

37
Q

Hvaða áhrif hefur sympatisk ítaugun á upptöku í görnum?

A

Sympathetic innervation promotes net absorption from the intestines

38
Q

Hvaða áhrif hefur aldósterón á upptöku vatns og elektrolyta og hvernig?

A

Aldosterone increases the net absorption of water and electrolytes by stimulating the basolateral sodium-potassium ATPases

39
Q

Hvaða áhrif hafa sykursterkar og somatostatin á vatns og elektolyta upptöku í görn og hvernig?

A

Glucocorticoids and somatostatin increase water and electrolyte absorption by increasing the action of the basolateral sodium-potassium ATPases.

40
Q

Hvernig er upptöku sodium jóna (Na) stjórnað í görn?

A

Sodium ions – these are actively absorbed in a process mainly driven by sodium-potassium ATPases located in the basolateral and lateral membranes of the epithelial cells that line the gut walls.

41
Q

Hvernig er upptöku klór og bíkarbónat jóna háttað í görninni?

A

Chloride and bicarbonate ions – the movement of sodium into the plasma produces an electrochemical gradient that allows the absorption of chloride ions. Chloride ions are exchanged for bicarbonate ions, resulting in the net secretion of bicarbonate ions

42
Q

Hvernig er upptöku vatns háttað í görninni?

A

Water – the absorption of these electrolytes results in the generation of an osmotic gradient that allows further absorption of water.

43
Q

Hvernig er upptöku kalíums háttað í görninni?

A

Potassium ions – the absorption of water along the length of the colon results in the concentration of potassium in the lumen. This provides an electrochemical gradient that allows the movement of potassium ions into the plasma.

44
Q

Hvernig er upptöku vítamína og fitu háttað í görninni?

A

Vitamins and fats – short-chain fatty acids, crucial B vitamins (B6 and B12) and vitamin K are produced by the digestion of chyme by the commensal microbial flora of the colon.

45
Q

Hvar eru fitusýrur meltar og teknar upp í görninni og hvaða ensím er aðal þar?

A

Lipid digestion into fatty acids and glycerol occurs almost entirely in the small intestine.

The main enzyme involved in lipid digestion is pancreatic lipase, which breaks down triglycerides into free fatty acids and monoglycerides.

46
Q

Hvernig virkar lípasi á fitusýrur?

A

Pancreatic lipase works with the help of emulsifying agents secreted by the liver and the gallbladder.

The main emulsifying agents are the bile acids, cholic acid and chenodeoxycholic acid. These are conjugated with the amino acids, glycine and taurine to form bile salts. Bile salts are more soluble than bile acids and act as detergents to emulsify lipids.

The free fatty acids and monoglycerides form tiny particles with these bile salts called micelles. The outer region of the micelle is water-attracting (hydrophilic), whereas the inner core is water-repelling (hydrophobic).

This arrangement allows the micelles to enter the aqueous layers surrounding the microvilli and free fatty acids and monoglycerides to diffuse passively into the small intestinal cells.

47
Q

Hvernig eru fituleysanlegu vítamínin tekin upp? (ADEK)

A

The fat-soluble vitamins (vitamins A, D, E and K) follow the same pathway for fat absorption and are absorbed along with the free fatty acids and monoglycerides. The remaining water-soluble vitamins are mainly absorbed by diffusion or mediated transport (apart from vitamin B12, which is absorbed via the intrinsic factor binding process).

48
Q

Hvað er achlorhydria og hverju veldur hún?

A

Achlorhydria is an autoimmune disease of the gastric parietal cells, which results in inadequate production of gastric acid. The damaged parietal cells are unable to produce the required amount of gastric acid. This leads to an increase in gastric pH, impaired food digestion and an increased risk of gastroenteritis.

49
Q

Gastric parietal frumur seyta hydrochloric sýru sem afleiðingu af þrenns konar stimuli:

A

The gastric parietal cells secrete hydrochloric acid in response to the following three stimuli:

  • Histamine stimulating H2 histamine receptors (most significant contribution)
  • Acetylcholine via parasympathetic activity stimulating M3 receptors
  • Gastrin stimulating CCK2 receptors

The gastric parietal cells also produce intrinsic factor, which is required for the absorption of vitamin B12.

50
Q

Hvaða frumur seyta intrinsic factor sem þarf til að taka upp B12?

A

Parietal frumur í maga.

51
Q

Hvaða áhrif hefur Ach á seyti magasýru?

A

Eykur seyti magasýru.

52
Q

Hvaða frumur í brisi sjá um exocrine seyti þess?

A

The pancreatic juice is composed of a number of enzymes that are secreted by the acini, water and bicarbonate ions. The enzymes are produced by digestive enzymes on the rough endoplasmic reticulum within the acinar cells.

53
Q

7 ensím sem eru brisvökvanum:

A
  • Chymotrypsinogen and trypsinogen – proteases that digest proteins and peptides to single amino acids
  • Pancreatic lipase – which digests triglycerides, monoglycerides and free fatty acids
  • Amylase – which digests disaccharides
  • Proelastase
  • Procarboxypeptidase
  • Phospholipase A2
  • Cholesterol esterase
54
Q

Hvaða frumur framleiða cholecystokinin og hvað gerir það?

A

Cholecystokinin is a peptide hormone produced and released by the I-cells in the duodenum. It stimulates the delivery of digestive enzymes from the pancreas and bile from the gallbladder into the small intestine.

55
Q

Í hvaða tvo flokka má skipta galli?

A

The liver is responsible for producing between 0.25 and 1 litre of bile per day.

The constituents of hepatic bile can be divided into two groups; a bile acid-dependent component and a bile acid-independent component.

56
Q

Bile pigments: 2 dæmi, hvernig verða þau til og hvernig eru þau útskilin?

A

The bile pigments are excretory products of the liver and include biliverdin and bilirubin. Bilirubin is a breakdown product of haemoglobin and is conjugated in the liver and secreted into bile. Bile pigments are normally excreted in the faeces, which gives the faeces its brown appearance. Problems in the liver or biliary tree can result in the accumulation of bilirubin in the blood, which results in the yellow appearance of the skin and sclerae seen in jaundice.

57
Q

Hvað er í bile acid-independent hlutanum af galli? Hvaða hormón örvarar framleiðsluna á því? Hvert er það skilið út?

A
  • The bile acid-independent component is an alkaline solution that is made by the ductal cells that line the bile ducts.
  • Production of this solution is stimulated by the hormone secretin.
  • Both the bile acid-dependent and bile acid-independent components enter into the intrahepatic bile ducts, which drain into the biliary tree, a series of ducts which transport bile from the liver to the gallbladder and duodenum.
58
Q

Bile acid dependent hlutinn af galli: úr hverju er hann og hvar er það framleitt? Hverjar eru aðal tvær gallsýrurnar?

A

The bile acid dependent component is made up of the bile acids, bile pigments and cholesterol. These are produced by the hepatocytes and then secreted into the canaliculi, which transport the bile acid-dependent portion towards the bile ducts.

There are two main bile acids; cholic acid and chenodeoxycholic acid. These are conjugated with the amino acids glycine and taurine to form bile salts. Bile salts are more soluble than bile acids and act as detergents to emulsify lipids. (link to small intestine tutorial)

MRCEM Primary Exam (21 decks)

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