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

Introduction to the GI Tract Flashcards

deck complete

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
Q

chief cells of the gastric mucosa

A

secret enzymes of gastric juice (pepsin)

26
Q

parietal cells of the gastric mucosa

A

secrete hydrochloric acid and intrinsic factor (imp for B12 absorption)

27
Q

endocrine cells of the gastric mucosa

A

secrete grelin - hormone which promotes appetite) and gastrin - digestive hormone

28
Q

functions of the stomach

A

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
Q

where does the upper GI tract end

A

pylorus (where stomach moves to small intestine)

30
Q

features of the small intestine

A

tube approx 2.5cm wide
6-8m long
sits concertinad and coiled in central abdomen
divided into 3

31
Q

duodenum

A

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
Q

jejenum

A

approx 2.5m long
transitions seamlessly into ileum

33
Q

ileum

A

3.5m long
ends at ileo-caecal valve in RIF

34
Q

smal intestinal mucosa

A

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
Q

colon/large intestine

A

diameter approx 6cm
length 1.5m
4 sections - caecum, colon, rectum and anal canal
colon divided into ascending, transverse, descending and sigmoid sections

36
Q

rectum

A

last 15-20cm of large intestine
repository for stool
ends at the anal canal where there is a transition to squamous mucosa

37
Q

anal sphincter

A

internal - smooth muscle
external - striated muscle

38
Q

wall of colon

A

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
Q

appendix

A

8-10cm long
variable position
vestigial
may have a role in gut microflora

40
Q

peritoneum

A

continuous membrane covering most abdominal organs
made up of two layers - visceral and parietal

41
Q

visceral peritoneum

A

line the organs, is their serosa

42
Q

parietal peritoneum

A

lines walls of abdominal cavity

43
Q

intraperitoneal

A

lies within peritoneum

44
Q

extraperitoneal

A

outwith peritoneum

45
Q

retroperitoneal

A

extraperitoneal and behind peritoneum
includes pancreas, kidneys, adrenals, urinary tract, parts of duodenum, colon and rectum

46
Q

mesentery

A

a large fold of parietal peritoneum attached to small intestine and prevents knotting up

47
Q

omentum

A

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
Q

gallbladder

A

lies below the liver
internally mucosa form rugae

49
Q

functions of the gallbladder

A

stores bile - crucial for fab absorption
when triggered by gut hormone (CCK) it empties

50
Q

pancreas

A

15cm long
head lies within curve of duodenum
tail touches spleen
endocrine and exocrine functions

51
Q

exocrine pancreas

A

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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