Upper GI tract Flashcards

1
Q

What does the circular muscle do and what does the longitudinal muscle do in the stomach?

A

CIRCULAR:

-SEGMENTATION (weaker contractions
)

  • keeps the food in thestomach for some time so it can be properly broken down
  • 80% of contractions

LONGITUDINAL:

-PERISTALSIS

20% of contractions

-propels CHYME towards the colon

-more powerful contractions as moves food from the Lower Oesophageal sphinter to the Pyloric sphincter

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2
Q

What are the 5 parts that make up the foregut?

A
  • Oesophagus
  • Stomach
  • Liver
  • Pancreasa
  • Bilary system( liver, gall bladder and bile ducts work together to secrete bile)
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3
Q

What 2 things make up the midgut?

A
  • Small intesine
  • Part of the large intestine
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4
Q

What 2 things make-up the Hind gut?

A
  • Colum
  • Rectum
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5
Q

What are the 4 layers of the GI tract?

A

MUCOSA-mainly epithelium(secretary and absorpative)

SUBMUCOSA-connective tissue and capillaries

MUSCULARIS(2 layers of muscle):

-CIRCULAR MUSCLE LAYER(constricts the bowel=divides it into segments =food passes between segments and stays for a while in each segmwent allowing absorption happening)

-LONGITUDINAL OUTER MUSCLE LAYER -propagates food through the intestinal tract

SEROSA/ADVENTITIA-connective tissue and epithelium(protective layer/lining)

There are subtle differences as you go from the Oesophagus down towards the rectum

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6
Q

How many teeth do we have and what is the makeup?

A

32:

  • 8 incisors
  • 4 canines
  • 8 premolars
  • 12 molars
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7
Q

Which muscles in the oral cavity are part of the GI tract?

A

MASSETOR MUSCLES -largest Jaw muscle responsible for biting

-several muscles that control the position of the mandible

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8
Q

What does the tongue do as part of GI tract?

A

propogates food into the pharynx

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9
Q

What is the function of the Oesophagus?

A

Porpagates food from the Pharyunx to the stomach

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10
Q

What is the structure and function of the Epithelium lining the Oesophagus?

A

SQUAMOS CELLS(non-keratinising)

PROTECTIVE LINING- e.g, against hot temperatures

MUCUS SECRETUNG GLANDs-lubricate food as it goes down

MUSCLES-Upper and Lower Sphincter

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11
Q

What happens to the lining of the Oesophagus on prolonged exposure to Acid?

A

Squamos epithelium cells change to columnar epothelium cells as these can secrete mucus to protect against the acid

METAPLASIA -change in cell type

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12
Q

What is the eosophical hiatus?

A

opening in the diaphragm through which the esophagus and the vagus nerve pass.

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13
Q

How is acid reflux prevented by the gastro-eosophagel junction?

A
  • diaphragm pinches at the bottom of the Eosophagus preventing acid from going up
  • acute angle between the oesophagus and stomach
  • mucosal fold(rugae) in this area that prevents acid going up
  • Oesophagus is 2 cm in the abdomen(+ve pressure) and goes through the thorax(-ve pressure) the differential betweent he different pressure means the lower end of the oesophagus in the abdomen is kept in a collapsed state which prevents the acid from going up
  • Eosophageal ligaments suspend the juction at a certian angle
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14
Q

What is a Hiatus Hernia?

A

The Eosophageal Hiatus becomes enlarged=some of the stomach migrates into the chest = Gastro-Oesophageal junction is kept open=Acid reflux

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15
Q

What are the stages of swallowing?

A

STAGE 0: ORAL PHASE

  • chewing and saliva prepare Bolus
  • Both Sphincters CONSTRICTED

STAGE 1: PHARYNGEAL PHASE

  • Pharyngeal musculature guides Bolus towards the oesophagus
  • Both Sphincters OPEN

STAGE 2: UPPER OESOPHAGEAL PHASE

  • upper sphincter contracts
  • Superior muscle rings contract
  • inferior muscle rings dialates
  • sequential contraction of longitudinal muscle

STAGE 3: LOWER OESOPHAGEAL PHASE

  • Lower sphincter closes as food passes through
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16
Q

What are the parts of the stomach?

A

CARDIA and PYLORIC REGION-secretes mucus

BODY and FUNDUS-Mucus, HCL, Pepsinogen

ANTRUM-has gastrin(secrets gastric acid)

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17
Q

What are the functions of the stomach?

A
  • Breaks food into smaller particles by secreting acid and enzymes
  • Holds food and releases it at a slow and steady rate into the Duodenum
  • Kills parasites and certain bacteria
18
Q

What are the functions of the Circular and Longitudinal muscles in the stomach?

A

Circular:

-SEGMETATION

  • holds food and churns it in different parts of the stomach so it can be broken down properly
  • 80% of contractions
  • weaker contractions

Longitudinal:

-PERISTALSIS

-propels chyme towards the colon

  • pushes food from the lower eosophageal sphincter to the pyloric sphincter and therefore the muscle contractions are stronger
  • 20% of contractions
19
Q

What are the main cells that are present in the stomach?

A
  • Chief cells
  • Parietal cells
20
Q

What are the function of chief cells?

A
  • secretes PEPSINOGEN which is converted (by HCL) to pepsin(an enzyme) that can break down proteins
  • rich in RER and Golgi
  • rich in apical sectertion granuales that secrete the protein into the lumen
21
Q

What do Parietal cells do?

A
  • involved in creating HCL
  • has the H+/K+ ATPase Pump (
  • needs lots of mitochondria so theres enough ATP for the pump to function
  • series of Tubulovesicles and Canaliculi That alllow the HCL to be secreted
22
Q

Describe how HCL is made in the stomach?

A
  1. CO2 enters the parietal cell and mixes with water, this reaction is catalysed by CARBONIC ANHYDRASE to form H2CO3
  2. K+ comes into the cell from the capillaries and gets secreted into the gastic lumen, it is exchanged for Na+ which then leaves the cell and goes in to the capillaries
  3. The H2C03 dissociates into H+ and HCO3-, the HCO3- is exchanged for Cl- via an antiporter
  4. The pump then brings K+ into the parietal cell in exchange for H+ which it pumps out into the gastric lumen
  5. The Cl- naturall diffuses out of the parietal cell into the gastric lumen and combines with the Cl- to form HCL
23
Q

What does gastrin do and where is it secreted from?

A
  • secreted from G-CELLS in the antrum of the stomach
  • hormone that stimulates parietal cells to secrete HCL
  • stimulate hisamine release chromaffin cells(adrenal glands)
24
Q

What are the 3 main Stimuli in the Gastric Phase for the secretion of HCL and Enzymes?

A
  • Neurostimulation from the vagus nerve in response to thought, sight, smell and taste of food=HCL secretion
  • Local hormone stimulus-Gastrin-secreted by PANCREAS entering the blood stream and then stimulating the Parietsal cells

Local relexes-stomach DISTENDS with food triggering local responses through the nerves in the stomach wall(myenteric plexus and Submucous plexus) causing more HCL and enzymes to be secreted

25
Q
A
26
Q

What happens tot he stomach if the vagus nerve is cut?

A
  • Lose muscle movement of the stomach
  • and secretion of HCL
27
Q

What stimulates/inhibits the secretion of HCL in the Intestinal Phase?

A
  • Food enters the intestine and this sends signals to the brain which then sends signal to the stomach via the VAGUS NERVE to produce HCL
  • the small bowel will secrete ENTERGASTRONE hormones( Gastric Inhibitory Peptides, Cholecystokinin, Secretin) which play a role in the ENTEROGASTORONE REFLEX which either stimulates or inhibites HCL secretion
28
Q

What does bacteria H.Pylori do?

A

The stomach has a thick layer of mucosa to protect it form HCL Bacteria H.Pylori breaks down this mucus lining

Allows the HCL to destroy stomach cells and give rise to PEPTIC ULSERS

29
Q

How can you produce a drug to decrease HCL secretion?

A

Drugs to block GASTRIN, HISTAMINE OR ACh binding to there corresponding receptors on Parietal cells as all these hormone stimulate the sectetion of HCL

30
Q

Why would Chyme fatty acid secretion decrease HCL secretion in the stomach?

A

Chyme is digested food and stuff so once it enters the Small Bowel the stomach wont need to do anymore so HCL secretion will decrease