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PHGY 210 > Gastro I > Flashcards

Gastro I Flashcards

1
Q

The gastrointestinal tract runs from the […] to the […]

A

Mouth, anus

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2
Q

Name the 4 accessory digestive organs.

A

Salivary glands, pancreas, liver, gallbladder

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3
Q

What are the 6 main activities of the GIT?

A

Ingestion, secretion, motility, digestion, absorption, defecation

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4
Q

Secretion is done by what types of cells?

A

Exocrine and endocrine glandular cells.

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5
Q

Motility is done by what type of cell?

A

Muscle cells.

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6
Q

What is the purpose of secretion, motility, and absorption in the GIT?

A

Secretion: chemical breakdown
Motility: propulsion and physical breakdown
Absorption: transfer of broken down molecules in the circulation

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7
Q

What is the main role of the GIT?

A

The role of the GIT is to break the food down into absorbable molecules that can go into the bloodstream to deliver energy and raw materials to the cells of the body.

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8
Q

For a given meal, the GIT can absorb […] of carbohydrates, […] of fat, and […] of protein. This makes the GIT highly […].

A

For a given meal, the GIT can absorb 99% of carbohydrates, 95% of fat, and 92% of protein. This makes the GIT highly efficient.

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9
Q

The control of propulsive, secretory, and absorptive activities are coordinated by what mechanisms?

A

Neural and hormonal

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10
Q

What are the two key features of the GIT structure?

A
  1. Tubular nature
  2. Communication with external environment at both ends
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11
Q

Describe the GIT structure of an earthworm.

A

It is a continuous tube with a central cavity with a lining that prevents bacteria from entering and allows for nutrient absorption. It is approximately the same length as their body.

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12
Q

How does the relative length of the GIT in humans compare to that of earthworms? Use specific numbers.

A

n the earthworm, it’s the same length as the body. In the human, it 3X longer than the human body (4.5 m length vs 1.5 m height). When all the muscle tone is lost from the GIT (in the case of a cadaver), the tract is actually even longer, around 10 m.

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13
Q

How does the internal surface area of the GIT compare to the external surface area in humans? Use specific numbers.

A

Adult: 200-250 m2
This is 600x bigger than the external surface

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14
Q

Why is the total internal surface area of the GIT so large in humans?

A

It gives us more room to be able to absorb nutrients into the body.

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15
Q

What are the 4 main layers of the GIT wall? Describe where they are relative to one another.

A

From inside to outside: mucosa, submucosa, muscularis externa, serosa

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16
Q

What is the purpose of the serosa?

A

It is a thin and tough layer of connective tissue that, in some parts of the GIT, is continuous with the peritoneum of the abdomen. This helps keep the GIT in place.

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17
Q

What is the muscularis externa composed of? Include relative locations.

A

On the inside, there are circular fibers. On the outside, there are longitudinal fibers.

18
Q

How does the muscularis externa vary throughout the GIT? Explain these variances and where they occur.

A

Smooth muscle makes up the majority of the muscularis externis (both longitudinal and circular). Striated muscle exists:
- From the mouth to the upper third of the esophagus
- In the anal sphincter

19
Q

What is the difference between smooth and striated muscle in the muscularis externa?

A

Smooth muscle is not under voluntary control, while striated muscle is.

20
Q

What is the function of the circular and longitudinal muscle in the GIT wall?

A

Longitudinal = running along the length of the tube. If it contracts, the GIT will get shorter.
The circular fibers, on the other hand, will make the diameter smaller if they contract.

21
Q

What is the submucosa comprised of in the GIT wall?

A

Loose, connective tissue that houses the neuronal network, lymphatics, and blood vessels

22
Q

What are the layers of the mucosal layer of the GIT wall? Include their relative positions and what they’re made of.

A

From outside to inside:
- Muscularis mucosae: smooth muscle
- Lamina propria: loose connective tissue
- Epithelial layer: epithelial and glandular (secretory) cells

23
Q

The enteric nervous system (ENS) can be describe as a(n) […] and […] nervous system. Explain why.

A

Independent and integrative.
Independent = It acts independently of the CNS.
Integrative = it has interneurons that can send signals through the gut wall to different parts.

24
Q

What are the 4 main functions of the ENS?

A

It initiates, programs, regulates, and coordinates the activities of muscular, secretory, and absorptive elements of the GIT.

25
Q

ENS nerve cell bodies are collected in structures called…

A

Plexi (singular plexus)

26
Q

How many plexi does the ENS have? Name and locate them.

A

2 plexi: submucosal plexus and myenteric plexus.
Submucosal: in submucosa
Myenteric: between the circular muscle and longitudinal muscle in the muscularis externa.

27
Q

What types of neurons are present in the ENS plexi? State their type and function.

A

Sensory neurons: have stretch receptors, chemoreceptors, and osmoreceptors in the mucosa or muscle
Motor/effector neurons: activate the secretory and muscle cells
Interneurons: expand responses to stimule in the GIT.

28
Q

Excitatory enteric neurons can synapse onto what types of cells?

A

Smooth muscle cells or secretory cells.

29
Q

Excitatory enteric neurons release […] on […] receptors on target cells, and can be blocked by […]

A

Excitatory enteric neurons release ACh on muscarinic receptors on target cells, and can be blocked by atropine

30
Q

Inhibitory enteric neurons release […], such as […] on target cells.

A

Inhibitory enteric neurons release NANCs, such as nitric oxide (NO) on target cells.

31
Q

How is the net activity of a smooth muscle cell or secretory cell due to the ENS determined? What is the advantage of this?

A

Its ultimate activity is the algebraic sum of activations (+) and inhibitions (-) from enteric neurons. This allows system activity to be fine-tuned and precise.

32
Q

Describe the progression of events in short, intramural reflexes.

A

The GIT feels a change via the chemoreceptors, osmoreceptors, and mechanoreceptors. These will activate the enteric nervous system.

This will then activate effector neurons in the nerve plexus. They go on to activate or inhibit muscle or secretory cells. This will create a response.

33
Q

What is the role of enteric sensory fibers?

A

Enteric sensory fibers have cell bodies in plexuses. They get information from gut chemoreceptors and mechanoreceptors.

34
Q

Input on the ENS from the CNS occurs on […]

A

Input on the ENS from the CNS occurs on the enteric neurons ONLY (not smooth muscle or glandular cells)

35
Q

The […] portion of the CNS can excite the ENS by releasing […] from its […] fiber.

A

The parasympathetic portion of the CNS can excite the ENS by releasing ACh from its pre-ganglionic fiber.

36
Q

The […] portion of the CNS can inhibit the ENS by releasing […] from its […] fiber.

A

The sympathetic portion of the CNS can inhibit the ENS by releasing Noradrenaline from its post-ganglionc fiber.

37
Q

What nerves are responsible for the parasympathetic effect on the GIT?

A
  • The vagus (X) nerve from the esophagus down to the bottom of the colon
  • The pelvic nerves from the bottom of the colon to the rectum.
38
Q

What ganglia are responsible for sympathetic effects on the GIT?

A

Esophagus and stomach: celiac ganglion
Small intestine and top of colon: superior mesenteric ganglion
Top of colon to rectum: interior mesenteric ganglion

39
Q

The ANS can influence the GIT via the […]

A

The ANS can influence the GIT via the ENS ONLY

40
Q

What effect do parasympathetic and sympathetic inputs from the CNS have on blood vessels in the GIT?

A

Parasympathetic input: dilation of blood vessels
Sympathetic input: constriction of blood vessels

41
Q

What are long reflexes?

A

These are reflexes in the ENS originating from the CNS.

42
Q

Can parasympathetic inputs from the CNS affect excitatory enteric neurons, inhibitory enteric neurons, or both? What about sympathetic?

A

Both can excited or inhibit either type.

PHGY 210 (36 decks)

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