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Year 1 Week 13 - Nutrition and Digestion > Introduction to the GI Tract > Flashcards

Introduction to the GI Tract Flashcards

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1
Q

terms used to describe the GI tract

A

gut
alimentary canal
digestive tract

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2
Q

in simple terms, what is the GI tract

A

double ended tube that allows digestion and absorption of food

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3
Q

organs of the GI tract

A
  1. oesophagus
  2. stomach
  3. liver
  4. gallbladder
  5. pancreas
  6. small intestine
  7. ileum
  8. large intestine/colon
  9. rectum
  10. anus
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4
Q

length of the GI tract

A

up to 10m

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5
Q

body cavities of the GI tract

A

oesophagus in thoracic cavity, all else in abdominal

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6
Q

layers of the GI tract

A

mucosa
submucosa
muscularis
serosa
some parts of GI tract have modification to standard layers

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7
Q

mucosa

A

lining of the GI tract. itself comprises of 3 layers, including a thin layer of muscle

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8
Q

submucosa

A

connective tissue, where blood vessels and nerves lie

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9
Q

muscularis

A

layers of smooth muscle and enteric nervous system

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10
Q

serosa

A

visceral layer of the peritoneum

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11
Q

the mouth

A

aka oral/buccal cavity
key for mastication, speech, start of digestion, some absorption

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12
Q

what does the mouth comprise of

A

lips, cheeks, soft and hard palates
tongue (skeletal muscle) with taste buds on papillae
salivary glands - submandibular, parotid and sublingual - secrete salivary amylase
teeth

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13
Q

the pharynx

A

divided into 3 sections - nasopharynx, oropharynx, and laryngopharynx

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14
Q

what does swallowing involve

A

moving a food bolus from the buccal cavity to the oesophagus through the pharynx

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15
Q

process of peristalsis

A

muscles contract above food bolus, constricting passageway and pushing bolus down
muscles relax around bolus, allowing passageway to open

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16
Q

anatomy of the oesophagus

A

first segment of the true digestive tract
about 25cm
extends from pharynx to stomach, traverses the diaphragm
posterior to heart and trachea

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17
Q

sections of the oesophagus

A

cervical
thoracic
abdominal

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18
Q

cell types of the oesophagus

A

lined with stratifies squamous epithelium - thick, robust
last 1cm is columnar epithelium

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19
Q

muscle type of oesophagus

A

voluntary, striated in upper third
involuntary, smooth in lower third
mixed in middle

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20
Q

sphincters of the oesophagus

A

upper oesophageal sphincter - muscular. primarily cricopharyngeus. stops air getting into gut
lower oesophageal sphincter - comprises a thickened muscular layer in the lower oesophagus and cardia of the stomach (intrinsic) and the diaphragm (extrinsis). prevents acid/food reflux

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21
Q

features of the stomach

A

variable size - can hold up to 1.5L, usually collapsed
lies under diaphragm in central/left midline
divides into cardia, fundus, body, antram
oesophagus enters in the cardia, exit to the small intestine (duodenum) at the pylorus (pyloric sphincter)
stomach wall - 4 layers, adapted
mucosa folded into RUGAE - within these are gastric pits

22
Q

muscles of the stomach

A

lie in oblique layers, very strong and effective

23
Q

features of the gastric mucosa

A

glands
chief cells
parietal cells
endocrine cells

24
Q

glands of the gastric mucosa

A

secrete mucous which protects mucosa from acid environment of the stomach

25
chief cells of the gastric mucosa
secret enzymes of gastric juice (pepsin)
26
parietal cells of the gastric mucosa
secrete hydrochloric acid and intrinsic factor (imp for B12 absorption)
27
endocrine cells of the gastric mucosa
secrete grelin - hormone which promotes appetite) and gastrin - digestive hormone
28
functions of the stomach
food reservoir - holds food until ready to be digested digestion - started by gastric acids and juices and physically broken down by churning secretes intrinsic factor - allows B12 absorption some absorption - water, alcohol, some drugs endocrine - grelin and gastrin secretion
29
where does the upper GI tract end
pylorus (where stomach moves to small intestine)
30
features of the small intestine
tube approx 2.5cm wide 6-8m long sits concertinad and coiled in central abdomen divided into 3
31
duodenum
shortest of 3 sections of small intestine 25cm long split into 4 sections where biliary tract enters GI tract transitions into jejunum at the duedenojejunal flexure
32
jejenum
approx 2.5m long transitions seamlessly into ileum
33
ileum
3.5m long ends at ileo-caecal valve in RIF
34
smal intestinal mucosa
folded into villi increased surface area for absorption millions of villi when healthy gives a carpet like appearance each vilius contains blood and lymph vessels surface cells - enterocytes - have microvilli known as the 'brush border' digestive enzymes found here other cells include mucus secreting goblet cells, enteroendocrine cells, and stem cells found in deep crypts adjacent to villi
35
colon/large intestine
diameter approx 6cm length 1.5m 4 sections - caecum, colon, rectum and anal canal colon divided into ascending, transverse, descending and sigmoid sections
36
rectum
last 15-20cm of large intestine repository for stool ends at the anal canal where there is a transition to squamous mucosa
37
anal sphincter
internal - smooth muscle external - striated muscle
38
wall of colon
multiple mucous secreting glands no villi but crypts muscles grouped into dense strips (taeniae coli) and rings - shorter than bowel and mean haustra (pouches) are formed
39
appendix
8-10cm long variable position vestigial may have a role in gut microflora
40
peritoneum
continuous membrane covering most abdominal organs made up of two layers - visceral and parietal
41
visceral peritoneum
line the organs, is their serosa
42
parietal peritoneum
lines walls of abdominal cavity
43
intraperitoneal
lies within peritoneum
44
extraperitoneal
outwith peritoneum
45
retroperitoneal
extraperitoneal and behind peritoneum includes pancreas, kidneys, adrenals, urinary tract, parts of duodenum, colon and rectum
46
mesentery
a large fold of parietal peritoneum attached to small intestine and prevents knotting up
47
omentum
continuation of serosa of the stomach essentially an apron hanging over the intestines if perforation/inflammation occurs it can wrap around the segment and seal it off
48
gallbladder
lies below the liver internally mucosa form rugae
49
functions of the gallbladder
stores bile - crucial for fab absorption when triggered by gut hormone (CCK) it empties
50
pancreas
15cm long head lies within curve of duodenum tail touches spleen endocrine and exocrine functions
51
exocrine pancreas
majority of the tissue have an acinar arrangement like liver complex ductal collecting system ending at pancreatic duct which empties into duodenum secretes pancreatic juice - i.e. digestive enzymes and sodium bicarbonate

Year 1 Week 13 - Nutrition and Digestion (6 decks)

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