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MD2001 Week 4 > Gastrointestinal System > Flashcards

Gastrointestinal System Flashcards

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
Q

What is the PSNS general function?

A

Rest and digest

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26
Q

Where do nerves originate in the SNS?

A

Thoracic and lumbar regions

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27
Q

Where do the SNS synapse?

A

Celiac

Superior mesenteric

Inferior mesenteric

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28
Q

What is the upper GI tract innervated by?

A

Nerves that synapse on the superior cervical ganglion

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29
Q

What is the SNS general function?

A

Flight or fight

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30
Q

What are the neurotransmitters in the SNS?

A

Noradrenaline

Neuropeptide Y

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31
Q

What is the enteric nervous system organised into?

A

Myenteric and submucosal plexuses

32
Q

What regulates the ENS?

A

PSNS and SNS

Can operate autonomously as well

33
Q

Describe the structure of the myenteric plexus

A

Dense parallel neuronal configuration

34
Q

What is the function of the myenteric plexus?

A

Primary role is regulating intestinal smooth muscle

Participates in tonic and rhythmic contractions

35
Q

What is the main function of the submucosal plexus?

A

Regulates intestinal secretions and local absorptive environment

36
Q

Where can the submucosal plexus synapse?

A

Blood vessels

Circular and longitudinal muscle

Muscularis mucosa

37
Q

What are ENS neurons supported by?

A

Enteric glial cells which resemble brain astrocytes

38
Q

Describe reflexes in the enteric nervous system

A

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
Q

What are the neurotransmitters in the ENS?

A

VIP

Substance p

Nitric oxide

Serotonin

Enkephalins

40
Q

What is the function of enkephalins?

A

Constrict circular muscle around sphincters

41
Q

What are some examples of hormones in the GI system?

A

CCK

Gastrin

Secretin

42
Q

What is the function of gastrin?

A

Increase gastric acid secretion

43
Q

What is the function of secretin?

A

Releases HCO2- and pepsin

44
Q

What are secretin and gastrin released by?

A

S cells

G cells

45
Q

What is the function of CCK (Cholecystokinin)?

A

Increases enzyme secretion

Contracts gallbladder

Increases gastric emptying

46
Q

What is CCK released by?

47
Q

Example of paracrines

A

Histamine

Prostaglandins

Somatostatin

48
Q

Describe the releasing cells and function of histamine

A

Enterhcromaffin-like cells

Mast cells

Increases gastric acid secretion

49
Q

Describe the releasing cells and function of prostaglandins?

A

Cells lining GI tract

Increase blood flow, mucus and HCO2- secretions

50
Q

Describe the releasing cells and function of somatostatin

A

D cells

Inhibits peptide hormones and gastric acid secretion

51
Q

What are the three phases of digestion?

A

Cephalic

Gastric

Intestinal

52
Q

Describe the cephalic phase

A

Triggered by thought of food,

Stimulates secretion by salivary glands, stomach, pancreas and intestines

Causes ACh and VIP release

53
Q

Describe the gastric phase

A

Begins when food and oral secretions enter stomach

Elicits neural, hormonal and paracrine GI responses

54
Q

Describe the intestinal phase

A

Begins when stomach contents reach duodenum

Initiates primarily hormonal, but also paracrine and neural responses

55
Q

What makes up the upper GI tract?

A

Mouth

Oesophagus

Stomach

56
Q

What is the function of the upper GI tract?

A

Transports and prepares food to be absorbed

57
Q

What happens in the mouth?

A

Mechanical and chemical breakdown of food

58
Q

What is mastication?

59
Q

What is saliva?

A

Watery fluid lubricates mouth, begins food digestion and is protective

60
Q

What are the different salivary glands of the mouth?

A

Sublingual

Submandibular

Parotid

61
Q

What are the different ganglions in the mouth?

A

Otic

Submandibular

62
Q

Describe the swallowing action

A

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
Q

How long does it take food to reach the stomach?

64
Q

What are the different functions of the stomach?

A

Accept and store food

Mix food with secretions

Digest food

Deliver food to small intestine

65
Q

What do pacemaker cells do in the stomach?

A

Initiates an action potential that drives waves of contraction through the stomach, mixing and grinding its contents

66
Q

What are the two steps in controlling salivary secretions?

A

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
Q

What do parietal cells release?

A

Intrinsic factor and hydrogen ions

68
Q

What do mucous neck cells release?

69
Q

What do chief cells release?

A

Pepsinogen

70
Q

Function of pepsinogen

A

Break down of proteins in eggs and meat

71
Q

What do G cells secrete?

72
Q

What is the effect of histamine, ACh and gastrin?

A

Increase secretion

73
Q

What is the effect of somatostatin and prostaglandin?

A

Decrease secretion

74
Q

What are the different sections of the GI tract?

A

Duodenum- first 0.3m

Jejunum- next 2.3m

Ileum- final 3.4m

75
Q

What are the different structures in the large intestines?

A

Caecum

Ascending, transverse, descending and sigmoid colon

Rectum

Anus

76
Q

What is the function of the ileocecal sphincter?

A

Regulates amount of chyme entering the large intestine

MD2001 Week 4 (10 decks)

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