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MD2001 Week 4 > Gastrointestinal System > Flashcards

Gastrointestinal System Flashcards

(76 cards)

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1
Q

What is the primary function of the GI system?

A

Absorption of dietary nutrients

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2
Q

What is peristalsis?

A

Movement of a bolus through the GI system

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3
Q

How does peristalsis work?

A

Muscle proximal contracts and the muscle distal relaxes

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4
Q

What is the inner most layer of the GI tract?

A

Mucosa

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5
Q

What are the different layers of the mucosa?

A

Epithelium

Lamina propria

Muscularis mucosa

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6
Q

How often is the epithelium replaced in the GI tract?

A

Every 2-3 days

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7
Q

How does the body control the absorptive or motility features of the mucosa?

A

The extent of villi and crypts

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8
Q

What is the lamina propria in the mucosa layer?

A

Loose connective tissue made up of elastin and collagen fibres

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9
Q

What is contained in the lamina propria?

A

Contain sensory nerves, blood and lymph vessels and secretory glands

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10
Q

What is the function of the muscularis mucosa?

A

Increases surface area by creating ridges and folds

Made from a thin layers of smooth muscle

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11
Q

What is the second most inner layer of the GI tract?

A

Submucosa

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12
Q

What is the structure of the submucosa?

A

Similar composition to the lamina propria

Incorporates blood vessels and nerve bundles that form a submucosal plexus

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13
Q

What is the third layer of the GI tract?

A

Muscularis externa

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14
Q

What are the three layers of the muscularis externa?

A

Circular muscle

Myenteric plexus

Longitudinal muscle

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15
Q

What are sphincters and what is there function?

A

Circular muscle

Regulate flow from different compartments to the next

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16
Q

What is the submucosal plexus also known as?

A

Meissner plexus

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17
Q

What is the myenteric plexus also known as?

A

Auerbach plexus

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18
Q

What is the outermost layers of the GI tract?

A

Serosa

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19
Q

What is the structure of the serosa layer?

A

Connective tissue with a layer of squamous epithelial cells

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20
Q

An example of a structure that does not have a serosal layer?

A

Oesophagus

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21
Q

What three division of the ANS regulate the GI tract?

A

Parasympathetic

Sympathetic

Enteric

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22
Q

What is the innervation of the parasympathetic nervous system?

A

Vagus nerve- medullar oblongata

Pelvic-splanchnic nerves S2-S4

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23
Q

What does the PSNS respond to

A

Stretch, pressure, temperature and somolarity

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24
Q

What neurotransmitters are used in the PSNS?

A

ACh

Gastric-releasing peptide

Substance P

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25
What is the PSNS general function?
Rest and digest
26
Where do nerves originate in the SNS?
Thoracic and lumbar regions
27
Where do the SNS synapse?
Celiac Superior mesenteric Inferior mesenteric
28
What is the upper GI tract innervated by?
Nerves that synapse on the superior cervical ganglion
29
What is the SNS general function?
Flight or fight
30
What are the neurotransmitters in the SNS?
Noradrenaline Neuropeptide Y
31
What is the enteric nervous system organised into?
Myenteric and submucosal plexuses
32
What regulates the ENS?
PSNS and SNS Can operate autonomously as well
33
Describe the structure of the myenteric plexus
Dense parallel neuronal configuration
34
What is the function of the myenteric plexus?
Primary role is regulating intestinal smooth muscle Participates in tonic and rhythmic contractions
35
What is the main function of the submucosal plexus?
Regulates intestinal secretions and local absorptive environment
36
Where can the submucosal plexus synapse?
Blood vessels Circular and longitudinal muscle Muscularis mucosa
37
What are ENS neurons supported by?
Enteric glial cells which resemble brain astrocytes
38
Describe reflexes in the enteric nervous system
Mechanoreceptor or chemoreceptor stimulation in the mucosa transmit signals to the submucosal plexus These stimulate other neurons in the submucosal or myenteric plexus that regulate endocrine or secretory cells
39
What are the neurotransmitters in the ENS?
VIP Substance p Nitric oxide Serotonin Enkephalins
40
What is the function of enkephalins?
Constrict circular muscle around sphincters
41
What are some examples of hormones in the GI system?
CCK Gastrin Secretin
42
What is the function of gastrin?
Increase gastric acid secretion
43
What is the function of secretin?
Releases HCO2- and pepsin
44
What are secretin and gastrin released by?
S cells G cells
45
What is the function of CCK (Cholecystokinin)?
Increases enzyme secretion Contracts gallbladder Increases gastric emptying
46
What is CCK released by?
I cells
47
Example of paracrines
Histamine Prostaglandins Somatostatin
48
Describe the releasing cells and function of histamine
Enterhcromaffin-like cells Mast cells Increases gastric acid secretion
49
Describe the releasing cells and function of prostaglandins?
Cells lining GI tract Increase blood flow, mucus and HCO2- secretions
50
Describe the releasing cells and function of somatostatin
D cells Inhibits peptide hormones and gastric acid secretion
51
What are the three phases of digestion?
Cephalic Gastric Intestinal
52
Describe the cephalic phase
Triggered by thought of food, Stimulates secretion by salivary glands, stomach, pancreas and intestines Causes ACh and VIP release
53
Describe the gastric phase
Begins when food and oral secretions enter stomach Elicits neural, hormonal and paracrine GI responses
54
Describe the intestinal phase
Begins when stomach contents reach duodenum Initiates primarily hormonal, but also paracrine and neural responses
55
What makes up the upper GI tract?
Mouth Oesophagus Stomach
56
What is the function of the upper GI tract?
Transports and prepares food to be absorbed
57
What happens in the mouth?
Mechanical and chemical breakdown of food
58
What is mastication?
Chewing
59
What is saliva?
Watery fluid lubricates mouth, begins food digestion and is protective
60
What are the different salivary glands of the mouth?
Sublingual Submandibular Parotid
61
What are the different ganglions in the mouth?
Otic Submandibular
62
Describe the swallowing action
Tongue forces food backward and initiates swallowing reflex Soft palate is pulled upward to close off access to nasopharynx Larynx and hyoid bone move upward and the epiglottis close access to larynx Upper oesophageal sphincter relaxes allowing bolus to enter
63
How long does it take food to reach the stomach?
6-10s
64
What are the different functions of the stomach?
Accept and store food Mix food with secretions Digest food Deliver food to small intestine
65
What do pacemaker cells do in the stomach?
Initiates an action potential that drives waves of contraction through the stomach, mixing and grinding its contents
66
What are the two steps in controlling salivary secretions?
Chlorine, sodium and water are transported into the duct lumen Ductal cells modify the fluid by reabsorbing sodium, chlorine and secreting potassium and bicarbonate
67
What do parietal cells release?
Intrinsic factor and hydrogen ions
68
What do mucous neck cells release?
Mucus
69
What do chief cells release?
Pepsinogen
70
Function of pepsinogen
Break down of proteins in eggs and meat
71
What do G cells secrete?
Gastrin
72
What is the effect of histamine, ACh and gastrin?
Increase secretion
73
What is the effect of somatostatin and prostaglandin?
Decrease secretion
74
What are the different sections of the GI tract?
Duodenum- first 0.3m Jejunum- next 2.3m Ileum- final 3.4m
75
What are the different structures in the large intestines?
Caecum Ascending, transverse, descending and sigmoid colon Rectum Anus
76
What is the function of the ileocecal sphincter?
Regulates amount of chyme entering the large intestine

MD2001 Week 4 (10 decks)

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