Physiology and Pharmacology of the Stomach Flashcards

1
Q

What is the volume capacity of the stomach?

A

50 > 1000ml

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2
Q

What nerve relaxes the stomach in order to accommodate food from the oesophagus?

A

The vagus nerve.

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3
Q

What is the stomach the starting point for?

A

Digestion of proteins (by pepsin and HCl)

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4
Q

The stomach is the starting point for the digestion of proteins. What else is continued to be digested in the stomach.

A

Carbohydrates (by salivary amylase) .

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5
Q

Why is the stomach usually described as 2 organs and not 1 organ?

A

As the distal part has different roles to the other parts.

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6
Q

What is the entrance into the stomach guarded by?

A

Entrance into the stomach is guarded by the lower oesophageal sphincter. This relaxes during swallowing to allow food to empty into the stomach but also prevents the reverse movement from body into oesophagus then the pharynx then the mouth.

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7
Q

What substance does the stomach mix food with?

When mixed with the substance, what is produced?

A

Gastric secretions to produce semi-liquid chyme.

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8
Q

What does the stomach do before passing it into small intestine as chyme for further digestion and absorption?

A

It stores food.

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9
Q

Approximately how many litres per day of gastric juice is secreted by the gastric glands in the gastric mucosa ?

A

approx. 2 litre/day

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10
Q

What is the fundus?

Where is it located?

What is its role?

A

The fundus is a thin smooth muscle layer in the stomach.

It is found next to oesophagus.

The fundus receives food but there is little mixing and little storage of food here.

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11
Q

What is the body?

Where is it located?

What is its role?

A

The body is a thin smooth muscle layer in the stomach.

It makes up the middle section of the stomach.

There is little mixing here and food is also stored here.

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12
Q

What is the Antrum?

Where is it located?

What is its role?

A

The antrum is a thicker smooth muscle layer.

Found next to duodenum.

Highly contractile: a lot of mixing here.

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13
Q

Physiologically the stomach can be divided into 2 parts;

Name these two parts.

A
  1. Orad

2. Caudad.

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14
Q

What does the orad stomach consist of?

A

Fundus and proximal body

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15
Q

What does the caudad stomach consist of?

A

The distal body and antrum

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16
Q

What type of contractions does the orad stomach have?

Are these contractions maintained or intermittent?

A

Tonic contractions

Maintained

17
Q

What type of contractions does the caudad stomach have?

Are these contractions maintained or intermittent?

A

Phasic contractions

Intermittent

18
Q

Where is the orad stomach directed towards?

A

The mouth

19
Q

Where is the caudad stomach directed towards?

A

The intestine.

20
Q

What nerves drive the Orad region?

A

The parasympathetic nerves - cranial nerve or vagus nerve

21
Q

What do the tonic contractions in the orad region do to the size of the stomach?

A

Decrease the size of the stomach.

22
Q

Why are tonic contractions weak?

A

Weak due to relatively thin musculature.

23
Q

What does the hormone gastrin do to the orad region of the stomach?

A

Increases contractions and hence rate of stomach emptying

24
Q

What other important hormone is involved?

A

Peptide hormone.

25
Q

Where do the phasic peristaltic contractions progress from and where do they travel to?

What is the name of this wave?

A

They progress from midstomach to gastroduodenal junction

The antral wave.

26
Q

What does the antral wave do?

A

Propels contents towards pylorus through which a very small volume of chyme flows into the duodenum

27
Q

What is retropulsion?

A

A process in which muscular contractions push food that has entered the duodenum backward into the stomach. This helps to mix the chyme with gastric juices, and to break large lumps of food into smaller pieces to pass through the pylorus.

28
Q

What determines the escape of chyme through pyloric sphincter?

A

The strength of the antral wave.

29
Q

What 2 factors control rate of the emptying of chyme through pyloric sphincter?

A
  1. Gastric factors

2. Duodenal factors

30
Q

What are the 2 gastric factors that control rate of the emptying of chyme through pyloric sphincter?

A
  1. The rate of emptying is proportional to volume of chyme in stomach: the larger the volume, the faster the emptying rate.
  2. The consistency of chyme: the thinner the chyme liquid is, the faster the rate.
31
Q

Why is the emptying rate faster when the volume of chyme in the stomach is larger?

A

As distension increases motility due to:

  • stretch of smooth muscle
  • stimulation of intrinsic nerve plexuses
  • increased vagus nerve activity and gastrin release
32
Q

What are the 2 duodenal factors that control rate of the emptying of chyme through pyloric sphincter?

A
  1. Duodenum must be ready to receive chyme: emptying can be delayed by neuronal and hormonal responses.
  2. The stimuli that drive the neuronal and hormonal responses have an indirect impact on the rate of emptying.
33
Q

What is the neuronal response?

A

The enterogastric reflex – decreases antral activity by signals from intrinsic nerve plexuses and the autonomic nervous system; therefore reducing rate of emptying.

34
Q

What is the hormonal response?

A

The release of enterogastrones [e.g cholecystokinin CCK)] from duodenum inhibits stomach contraction; therefore reducing rate of emptying.