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Phgy 210 > Digestive system Lecture 1 > Flashcards

Digestive system Lecture 1 Flashcards

1
Q

WHat is the alimentary canal?
What are the 4 accessory digestive organs?

A

-continuous tube from mouth to anus
accessory digestive organ:
Salivary Glands
Pancreas
Liver
Gallbladder

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2
Q

What is the definiton of GIT function?

A

-conveys food along GIT, allowing it to be broken down into
small molecules which can be absorbed into the circulation

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3
Q

What are the 6 activities of GIT function?

A
  1. INGESTION
  2. SECRETION
  3. MOTILITY
  4. DIGESTION
  5. ABSORPTION
  6. DEFECATION
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4
Q

What is secretion involved in?
What is motility involved in?
What is absorption involved in?

A

-SECRETION–>chemical breakdown
glandular activity - exocrine and endocrine
-motility–>propulsion and physical breakdown
ex. muscular activity
-absorption–>transfer to blood circulation

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5
Q

What are the 3 key functions of GIT?
What is homeostasis?

A

-they are secretion, motility and absorption
-At all levels of organization, body activities are directed at maintaining optimal and relatively constant INTERNAL CONDITIONS

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6
Q

What is the GIT’s role in the body to provide?
What is the GIT digestive and absorptive capacity for the various components?

A

-it is to provide nutrients to the body
-CARBOHYDRATE 99%
FAT 95%
PROTEIN 92%

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7
Q

What are the propulsive, secretory, and absorptive activities integrated for high efficiency by what 2 types of mechanisms?

A

-NEURAL and HORMONAL MECHANISMS

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8
Q

What is the structure of the GIT?

A

-it is a tube like structure connected to the external environment on both sides
-it is specialized to allow nutrients to come

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9
Q

How long is the GIT?
How long is it in a cadaver?

A

-4.5m
-in a cadaver it is 10m long since the muscles arent active

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10
Q

How much larger is the inner SA of the GIT vs the outer wall?
Why isthe inner wall so much larger in SA?

A

-internal is about 600x larger than external surface area 9about size of tennis court)
-gives us more room to absorb nutrients

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11
Q

What are the 4 main layers of the GI tract?
What is the description of each?

A

mucosa-3 layer structure that contains absorptve and secretory cells
submucosa-loost CT
-muscularis Externa
-Serosa-outer covering of GIT

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12
Q

What are the layers of the muscularis externa?
WHat is the serosa, what does is it continous with?
What muscle is mainly in the top and bottom portion of GIT, vs the middle/main area?

A

-longitudinal fiber and circular fiber
-serosa=thin, tough layer of CT
-it is continuous with lining of peritineum
-striated at the top near mouth/throat and at end of anus
-in the middle Smooth muscle makes up most of muscle

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13
Q

What do the longitudinal fibers do vs the circular fibers when muscle contracts?

A

-longitudinal fibers run along the length, and when the muscle contracts GIT gets shorter
-cricular fibers when contracted make the diamter smaller

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14
Q

What are the 3 layers of mucos and what they are composed of?
What is submucosa composed of, and containing what?

A

muscularis mucosa-smooth muscle
-lamina propria=loose CT
-epithelial layer=epithelial and glandular cells (in contact with the lumen)
-loose CT containing lymphatics and blood vessels

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15
Q

What is the structure of the serosa, and muscularis externa?
What is the muscle composition in when the muscularis externa is present?

A

1.serosa-thin, tough layer of CT (continuous in places with abdominal mesentery)
2. muscularis externa-outer layer longitudinal fibers (when it contracts GIT shortens), inner layer ciruclar fiber (lumen narrows when contracted)
-musculature in oral cavity, pharynx, upper 1/3 esophagus and external anal spincter is striated (rest is smooth)

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16
Q

What is composition of submucos and mucosa?
What is the epithelial layer responsible for?

A

-submucosa-loose CT, housing neuronal network, lymphatics, blood vessels
-mucosa-muscularis mucosa (smooth muscle)
-lamina propria (loose CT
-epithelial layer (secretory-exocrine and endocrine cells and absorptive cells

17
Q

What is the enteric nervous system (ENS)?
What are the properties of this nervous system?

A

-its neurons that reside within the wall of the GIT (also known as intramural system)
-it is independent (dont need CNS), and integrative (can send signals to GIT through gut wall

18
Q

What are the 4 characterisitcs of the ENS?

A

it initiates, programs, regulates and coordinates:
the activites of muscular and secretory and absorptive elements of the GIT

19
Q

What is the plexus?
What are the 2 plexus called?
What do the 2 plecuxes behave as?

A

-it is a collection of nerve cell bodies
-submucosal plexus and the mysenteric plexus
-they behave as one functional unit even though they are anatomically distinct

20
Q

What elements does the plexus contain, what are the elements?

A

-they contain all the elementes needed for reflex arc which include:
sensory neurons, motor/effector neurons, and interneurons

21
Q

What are the sensory neurons?
the motor/effector neurons (what do they activate)?
and the interneurons?

A

-Sensory Neurons with receptors in mucosa or muscle… stretch receptors, chemoreceptors osmoreceptors
-Motor/Effector Neurons activate the secretory and muscle cells
-Many Interneurons expand the responses to stimuli in the GIT

22
Q

what can the sensory fibers detect?
What is Ach, what is it blocked by?
What do enteric neurons synapse on?

A

-they can detect distension
-it is excitatory and is blocked by atropine
-they synapse on muscle or secretory cells

23
Q

What is NANC?
what is an example?
How is sum of ultimate activity calculated?

A

-NANC is an inhibtor, it is nonadrenergic and non cholinergic
ex. nitric oxide
-sum of activating-sum of inhibiting

24
Q

What are the short enteric reflexes

A

there is a stimulus that activates the sensory signals, chemoreceptors, osmoreceptor, mechanoreceptor and this leads to smooth muscle or gland cell response

25
Q

What plexus does the ENS consist of?
What do the 2 plexus behave as, what are the reflex arcs?

A

-The ENS consists of the myenteric plexus (between the longitudinal and circular muscle layers) and the submucosal plexus
-Though anatomically distinct, the two plexuses behave as a
functional unit, which includes all the elements required for reflex arcs: sensory neurons, motor/effector neurons, and
interneurons.

26
Q

What type of cells does the ENS consist of?

A

-The ENS consists of ganglion cells and their processes which
synapse with smooth muscle cells, endocrine and exocrine cells, and other ganglion cells

27
Q

What can enteric neurons be?
What do they release for each response?

A

-Enteric neurons may be excitatory (release ACh – acting on muscarinic receptors) or inhibitory (release NANC (Non Adrenergic, Non Cholinergic) transmitters, like NO)

28
Q

What do enteric sensory fibers have?
Where do they get info from?

A

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

29
Q

What type of activity do the para and sympathetic systems do?

A

Parasympathetic (preganglionic), Nicotinic Excitatory
-Sympathetic (postganglionic), Noradrenaline NA, Inhibitory

30
Q

What nerves innverate the para and sympathetic system?

A

-parasympathetic system, has vagus X nerve and pelvic nerve
-sympathetic system has:
celiac ganglion, superior mesenteric ganglion and inferior mesenteric ganglion

31
Q

How can the ANs influence the GIT?

A

-the autonomic nervous system can only effect GIT via the ENS by relaying parasympatheitc inputs onto the excitatory enteric neurons or inhibtory, and the inhibitory/excitatory sympathetic neurons onto the NANC enteric neurons

32
Q

What do para and sympathetic input cause for blood vessels on the GIT?

A

-Parasympathetic input → dilation of blood vessels
Sympathetic input → constriction of blood vessels

33
Q

How do parasympathetic neurons reach the wall of GIT as?
What do they synpase via, and exert?

A

-Parasympathetic neurons reach the wall of the GIT as
preganglionic fibers, synapsing (via nicotinic ACh receptors)
with enteric neurons (both excitatory and inhibitory) exerting
an excitatory effect

34
Q

How do sympathetic neurons reach the wall of GIT as?
What do they synapse via, and exert?

A

Sympathetic neurons reach the wall of the GIT as
postganglionic fibers, synapsing (via NA receptors) with
enteric neurons (both excitatory and inhibitory) exerting an
inhibitory effect

35
Q

What do sympathetic neurons also innervate,to cause what?
What do sensory neurons also allow for?

A

Sympathetic neurons also innervate smooth muscle in blood vessels, causing vasoconstriction
-Sensory neurons allow for “long reflexes”

36
Q

What does the human digestive system look like?

A

Phgy 210 (24 decks)

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