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Y1S1 > GI > Flashcards

GI Flashcards

1
Q

Where does the GI tract extend to

A

From the mouth to the anus

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2
Q

Whats its primary function

A

absorption of dietary nutrients, this is maximised by sections that convert larger molecules to smaller molecules ie, digestion

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3
Q

What is motility

A

Contents, including secretions, mixed and moved along tube by coordinated contraction/relaxation of tube walls

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4
Q

What are the other functions of the GI

A

storage and excretion

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5
Q

What is mucosa composed of

A

epithelium + lamina propria + muscularis mucosa

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6
Q

tell me some facts about the GI epithelium

A

shed and replaced every 2-3 days

apical side faces GI lumen , basolateral side faces interstitum and vasculature

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7
Q

lamina propria

A 
loose CT  made up of:
elastin and collagen fibres 
Contains:
sensory nerves
blood and lymph vessels
secretary glands
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8
Q

Muscularis mucosa

A

thin layer of smooth muscle

further increases surface area by creating ridges and folds

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9
Q

Tell me about the submucosa

A

thick layer
blood vessels and nerve bindles that form a submucosal plexus (messier plexus)
this is an integral part of the nervous system

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10
Q

Tell me about the Muscularis externa

A

this is composed of circular muscle + myenteric plexus + longitudal muscle
this is known as the Auerbach plexus

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11
Q

What is the function of the ENS

A

coordinates contractions to mix and move contents between compartments

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12
Q

What do spinchters

A

regulate flow from compartment to next

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13
Q

Tell me about the serosa

A

outmost layer of the connective tissue
layer of squamous epithelial cells
Some GI tract sections do not have this and connect straight to adventitia (outer layer of the blood vessels) e.g. abdominal or pelvic wall

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14
Q

What are the 3 divisions of the autonomic system that regulate GI function

A

parasympathetic
sympathetic
enteric

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15
Q

Tell me about the parasympathetic systems role in the GI

A

PSNS signals stimulate GI secretions and motility facilitating digestion and absorption of nutrients

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16
Q

What does the Sympathetic nervous system do to the GI

A

decreases GI secretions and motility

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17
Q

Tell me about the functions of the ENS

A

The PSNS and the SNS usually synapse with ENS components and modulate the ENS
This can however operate autonomously via intrinsic regulation and sensory reflexes
ENS nerves are organised into myenteric and submucosal plexus

18
Q

Desribe to me the myenteric plexus

A

A dense parallel neuronal configuration
primary role in regulating intestinal smooth muscle
participates in tonic and rhythmic contractions

19
Q

describe the submucosal plexus

A

primary regulates intestinal secretions and local absorptive environment
can also synapse on blood vessels, circular and longitudinal muscle, muscularis mucosa

20
Q

What is the ENS supported by?

A

enteric glial cells which resemble brain astrocytes

21
Q

Tell me about the reflexes of the ENS

A

neural circuits involving mechanoreceptor or chemoreceptor stimulation in the mucosa regulate many GI reflex actions
signal transmitted back to neurons in submucosal plexus which stimulate other neurones in submucosal or myenteric plexus that regulate endocrine or secretory cells

22
Q

Tell me about the neurotransmitters of the ENS

A

Enkephalins: constrict circular muscle around sphincters

VIP, substance P, ACh, nitric oxide, serotonin (5-hydroxytryptamine)

23
Q

Non-neuronal signalling molecules: give me some examples of hormones

A

CCK, gastrin, secretin

24
Q

Paracrines

A

released and act locally

prostaglandis and somatostatin are more widespread in their release and actions than histamine

25
Q

What are the digestive phases

A

Cephalic
Gastric
Intestinal

26
Q

Tell me about the cephalic

A

triggered by thought of food, conditions suggestive of previous food intake
primarily neural and causes ACh and VIP release
-stimulates secretion by salivary glands, stomach, pancreas, intestines

27
Q

GASTRIC PHASE

A

Begins when food and oral secretions enter the stomach
coincides with distension
Elicits neural, hormonal, paracrine GI responses

28
Q

INTESTINAL PHASE

A

Begins when stomach contents reach duodenum

Initiates primary hormonal, but also paracrine and neural responses

29
Q

What are the GI hormones

A 
Cholecystokinin
Gastrin
Glucose-dependant insulinotrpoic peptide 
motion
secretin
30
Q

GI paracrines include

A

histamines
prostaglandis
Somatostatin

31
Q

What do the phases of digestion prepare for?

A

they allow for preparation and timing and regulation feedback, the cephalic is primary a feed forward regulation
the gastric and intestinal phases are feedback mechanisms

32
Q

What is the upper GI tracts role

A

transports and prepares food to be absorbed, breaking into smaller pieces, hydrating it to improve environment for enzymatic actions

33
Q

What is the mouths role in GI

A

mechanical and chemical breakdown
mastication = chewing

teeth = cut, tear and pierce, grind and crush
jaw muscles provide force and movement

tongue = repositions food, tastes

34
Q

What is the role of the salivary glands

A

watery fluid lubricates mouth, begins food digestions, is protective

hypotonic to plasma:
-composition determined by ductal modification of primary secretion

35
Q

what is the oesophagus in the GI

A

afferent feedback to the swallowing centre
efferent responses through other nuclei
-muscle contracted proximal to distal
-coordinates other functions like speech and breathing

36
Q

What is the oesophagus’s role in peristalsis

A

series of coordinated muscle contractions/relaxations causing waves
commences after upper oesophageal sphincter this takes 6-10 seconds

37
Q

what are the functions of the stomach

A

accept and store food
mix food with secretions
digest food
deliver food to small intestine

38
Q

tell me about the secretions of the stomach

A

derived from pits known as gastric invaginations

39
Q

What are the three sections of the small intestine

A
  • duodenum
  • jejunum
  • ileum
    This is where most macronutrient vitamin, mineral absorption occurs
40
Q

LARGE INTESTINE

A

Caecum
Asending, transverse, descending, sigmoid colon
rectum
anus
this is where significant water and ion absorption
mixing and propulsion (pushing forwards)

Y1S1 (71 decks)

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