READ ME / 1: Structure of the GI tract and motility

Question 1

Thanks for using my flashcards, hope you find them useful!

If you spot any errors or have suggestions, please let me know by clicking the speech bubble or sending me a message. It’s really helpful.

Question 2

The questions are written using the official Dundee lectures, so you might find it useful to have them open in the background in case you get stuck.

Question 3

I write the questions based on what I think the important facts are, but not everything is relevant. Don’t waste your time learning tiny details.

Question 4

On the other hand, this isn’t everything you need to know - back it up with stuff from tutorials, other people’s questions, Youtube videos, Oxford handbooks etc.

Question 5

There’s a good chance that older decks will be inaccurate (lectures and guidelines change year to year) so I’ll try to update them in the future.

Break a leg 👍

Question 6

What is the purpose of the GI system?

Answer 6

Absorb nutrients from food ingested from the external environment

Question 7

What is ingested food called once it passes into the stomach and is partially digested?

Answer 7

Chyme

Question 8

The small intestine absorbs basic nutrients.

What does the large intestine absorb?

Answer 8

Fluids (water) and electrolytes

Question 9

What is a hormone, apart from insulin and glucagon, produced by the pancreas?

Answer 9

Somatostatin

Question 10

What does the exocrine liver produce?

Answer 10

Bile

Question 11

What is stored within the gall bladder?

Answer 11

Bile

Question 12

What is bile’s function?

Answer 12

Fat digestion

Question 13

What is motility (in terms of the GI tract)?

Answer 13

The movement of food down the tract

Question 14

Which kind of muscle is most involved in motility?

Answer 14

Smooth muscle

Question 15

Where in the GI tract is skeletal muscle found?

Answer 15

Mouth

Pharynx

Upper oesophagus

…

External anal sphincter

Question 16

By which process do enzymes digest complex molecules into smaller, absorbable units?

Answer 16

Hydrolysis

Question 17

How many layers of muscle are found in the muscularis externa?

Answer 17

Two

Question 18

What are the two layers of muscle found within the GI tract wall?

Answer 18

Muscularis mucosae (on the inside)

Muscularis externa (on the outside)

Question 19

What are the two types of muscle found within the muscularis externa?

Answer 19

Circular muscle

Longitudinal muscle

Question 20

How does circular muscle contraction affect the dimensions of the GI tract?

Answer 20

Narrower and longer

Question 21

How does longitudinal muscle contraction affect the dimensions of the GI tract?

Answer 21

Shorter and wider

Question 22

What are the special properties of the muscularis externa in

a) the colon
b) the stomach?

Answer 22

a) Longitudinal layer has three bands (teniae coli)

b) Muscularis external has circular, longitudinal AND oblique layers

Question 23

Which kind of junction connects GI smooth muscle cells?

Answer 23

Gap junctions (allows passing of ions –> electrical currents) between each cell

Question 24

Similar to that of the heart, which kind of smooth muscle cells trigger contractions in the GI tract?

Answer 24

Pacemaker cells

Question 25

In the GI tract, spontaneous electrical activity occurs as **(slow / fast)** waves.

Answer 25

**slow**

Question 26

What are the GI tract's pacemaker cells called?

Answer 26

Interstitial cells of Cajal (**ICCs**)

Question 27

ICCs are found in both muscle layers of the muscularis externa - what are these muscle layers called?

Answer 27

**Circular layer** **Longitudinal layer**

Question 28

Uptake of ions through which channel triggers smooth muscle contraction in the GI tract?

Answer 28

Ca²⁺ channels

Question 29

Efflux of ions through which channel triggers the downstroke of a smooth muscle repolarisation?

Answer 29

K⁺ channels

Question 30

Force of contraction in the digestive tract is related to the **(intensity / number)** of action potentials.

Answer 30

**number**

Question 31

Some molecules inhibit the contraction of smooth muscle by __ the downstroke, i.e causing **hyperpolarisation**.

Answer 31

**abolishing**

Question 32

Do all slow waves trigger a contraction of smooth muscle?

Answer 32

**No** - dependent on other stimuli

Question 33

What name is given to the collection of nervous tissue found within the GI tract?

Answer 33

**Enteric nervous system**

Question 34

Nerves of the enteric nervous system tend to join together and form \_\_\_.

Answer 34

**plexuses**

Question 35

The enteric nervous system is (**extrinsic / intrinsic**).

Answer 35

**intrinsic**

Question 36

Which arm of the autonomic nervous system is responsible for regulating GI function?

Answer 36

**Parasympathetic**

Question 37

What does parasympathetic stimulation of the GI tract cause?

Answer 37

**Increased secretion** **Increased blood flow** **Increased smooth muscle contraction** to aid in the digestion of food

Question 38

What does parasympathetic stimulation cause in the GI tract?

Answer 38

**Relaxation of smooth muscle**

Question 39

What is the neurotransmitter for parasympathetic **preganglionic nerve fibres**?

Answer 39

Acetylcholine

Question 40

What does **sympathetic stimulation** cause in GI tract sphincters?

Answer 40

**Increased tone** i.e holds them shut

Question 41

What is **peristalsis**?

Answer 41

Sequential contraction and relaxation of smooth muscle moving food aborrally

Question 42

What **stimulus** triggers peristalsis?

Answer 42

**Distension** of the gut wall by a bolus

Question 43

What molecules trigger **relaxation** of smooth muscle?

Answer 43

**VIP** **Nitric oxide**

Question 44

What is the name given to the mixing, churning movements of the GI tract which mix lumenal contents together?

Answer 44

**Segmentation**

Question 45

In the muscularis externa, which muscle layer contraction causes **segmentation**?

Answer 45

**Circular layer contraction** (narrower and longer)

Question 46

Which large contraction, occuring a few times a day, sweeps faeces into the rectum?

Answer 46

**Colonic mass movement**

Question 47

Which sphincter opens to allow swallowing?

Answer 47

**Upper oesophageal sphincter**

Question 48

Which sphincter relaxes to allow food to enter the stomach?

Answer 48

**Lower oesophageal sphincter**

Question 49

Which sphincter opens to allow the passage of chyme from the stomach to the duodenum?

Answer 49

**Pyloric sphincter**

Question 50

Which sphincter regulates flow from the **ileum** of the small intestine to the **caecum** of the large intestine?

Answer 50

**Ileocaecal valve**

Question 51

There are two anal sphincters - what are they called? What is the main difference between them?

Answer 51

**Internal** and **external anal sphincters** The external anal sphincter is **skeletal** - voluntary.

Question 52

The GI tract has **6 sphincters.** Divide them into two categories: **voluntary** and **involuntary**.

Answer 52

**Voluntary**: Upper oesophageal sphincter, External anal sphincter **Involuntary**: Lower oesophageal sphincter, Pyloric sphincter, Ileocaecal valve, Internal anal sphincter

Question 53

Can swallowing be voluntarily stopped once it has started?

Answer 53

**No -** all or nothing reflex

Question 54

Which type of receptor triggers the swallowing reflex?

Answer 54

**Mechanoreceptors**

Question 55

Which structure prevents food from entering the trachea?

Answer 55

**Epiglottis**

Question 56

Which cranial nerve supplies smooth muscle in the oesophagus?

Answer 56

**Vagus nerve** CN X