Intro to GI tract

Question 1

what terms are used to describe the GI tract?

Answer 1

gut
alimentary canal
digestive tract
gastrointestinal tract

Question 2

what does the GI tract do?

Answer 2

double open-ended tube that allows digestion and absorption of food

Question 3

what does the GI tract include?

Answer 3

oesophagus
stomach
liver
gall
pancreas
small intestine
ileum
colon
rectum
anus

Question 4

how long is the GI tract?

Answer 4

very long - up to 10 metres

Question 5

what cavities is the GI tract found in?

Answer 5

oesophagus - thoracic cavity
all other organs are in the abdominal cavity

Question 6

what is the wall of the GI tract formed of?

Answer 6

mucosa - the lining of the GI tract, comprises of 3 layers including a thin muscular layer
submucosa - connective tissue, where blood vessels and nerve lie
muscularis - layers of smooth muscle and enteric nerve system
serosa - the visceral layer of the peritoneum
some areas of the GI tract have modifications to these standard layers

Question 7

what is found in the mouth?

Answer 7

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

Question 8

what is the mouth key for?

Answer 8

mastication
speech
start digestion
some absorption

Question 9

what makes up the pharynx?

Answer 9

nasopharynx
oropharynx
laryngopharynx

Question 10

what is the pharynx involved in?

Answer 10

swallowing - food bolus moves from the buccal cavity to the oesophagus through the pharynx

Question 11

what is peristalsis?

Answer 11

contracting of muscles behind food bolus and relaxing of muscles in front of food bolus, allowing it to pass through the oesophagus

Question 12

what is the oesophagus?

Answer 12

first segment of true digestive tract

Question 13

where is the oesophagus located?

Answer 13

extends from pharynx to stomach, traverses the diaphragm
posterior to heart and trachea
has cervical, thoracic and abdominal sections

Question 14

what cells line the oesopahgus?

Answer 14

stratified squamous epithelium (thick and robust) until last cm when it become columnar epithelium

Question 15

what type of muscle control does it use?

Answer 15

voluntary in the upper third, mixed in the middle and involuntary in the lower third

Question 16

what are the two sphincters found in the oesophagus?

Answer 16

upper and lower oesophageal sphincter

Question 17

features of the upper oesophageal sphincter?

Answer 17

muscular
primarily cricopharyngeus
stops air getting into the gut

Question 18

features of the lower oesophageal sphincter

Answer 18

thickened muscular layer in lower oesophagus, cardia of stomach (intrinsic) and the diaphragm (extrinsic)
prevents food/acid reflux

Question 19

location of stomach

Answer 19

lies under diaphragm in central/left midline

Question 20

features of stomach

Answer 20

can hold up to 1.5l
usually collapsed
divided into cardia, fundus, body, antrum
oesophagus enters in the cardia, exits to duodenum at the pylorus
mucosa is folded into rugae, within these are gastric pits
muscles lie in oblique layers - very strong and effective

Question 21

what is the function of the stomach?

Answer 21

food reservoir - stores food until its ready to be digested
digestion - started by gastric acids and juices, physically broken down by churning
some absorption - water, alcohol, some drugs

Question 22

what are the features of gastric mucosa

Answer 22

glands
chief cells
parietal cells
endocrine cells

Question 23

what do glands in gastric mucosa do?

Answer 23

secrete mucous which protects the mucosa from the acid environment of the stomach

Question 24

what do chief cells in gastric mucosa do?

Answer 24

secrete enzymes of gastric juice (pepsin)

Question 25

what do parietal cells in gastric mucosa do?

Answer 25

secrete hydrochloric acid and intrinsic factor (important for b12 absorption)

Question 26

what do endocrine cells in gastric mucosa do?

Answer 26

secrete grelin (hormone that promotes appetite) gastrin (digestive hormone)

Question 27

what is the small intestine?

Answer 27

tube approx 2.5cms wide 6-8ms long divided into three

Question 28

features of duodenum

Answer 28

shortest section of small intestine 4 sections - superior duodenal flexure, descending, horizontal, ascending transitions into the jejunem at the duodenojejunal flexure where the biliary tract enters the GI tract

Question 29

features of jejunum and ileum

Answer 29

jejunum is 2.5ms long transitions seamlessly into the ileum iluem ends at the ileo-ceacal valve in the right illiac fossa

Question 30

features of small intestinal mucosa

Answer 30

folded into villi surface cells (enterocytes) have microvilli known as the brush border digestive enzymes goblet cells (mucus-secreting) enteroendocrine cells stem cells (found in deep crypts adjacent to villi)

Question 31

features of villi

Answer 31

increased surface area for absorption million of villi when healthy has a carpet-like appearance each villi contains blood vessels and lymph vessel

Question 32

what makes up the large intestine

Answer 32

caecum colon - ascending, transverse, descending, sigmoid rectum anal canal

Question 33

features of rectum

Answer 33

last 15-20cm of large bowel repository for stool ends at the anal canl where there is a transition to squamous mucosa internal (smooth muscle) and external (striated) anal sphincter

Question 34

features of the colon wall

Answer 34

multiple mucus secreting glands no villi - crypts instead muscles are grouped into dense strips (taeniae coli) and rings, these are shorter than the bowel and mean pouches (haustra) form

Question 35

appendix (idky its literally so irrelevant)

Answer 35

8-10cms long variable position vestigial (basically means it does fuck all, probably used to do something though) may have a role in gut microflora

Question 36

features of peritoneum

Answer 36

continuous membrane which covers most abdominal organs visceral layer - lines the organs, is their serosa parietal layer - lines the walls of the abdo cavity

Question 37

peritoneum terms

Answer 37

intraperitoneal - lies within peritoneum extraperitoneal - outwith the peritoneum retroperitoneal - intraperitoneal and behind the peritoneum mesentery - large fold of parietal peritoneum that is attached to the small intestine and prevents it knotting up omentum - continuation of the serosa of the stomach, apron hangs over intestines, if there is perforation/inflammation it can wrap around the segment and seal it off

Question 38

location of gallbladder

Answer 38

lies below the liver

Question 39

features of gallbladder

Answer 39

mucosa from rugae

Question 40

function of gallbladder

Answer 40

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

Question 41

location of pancreas

Answer 41

head lies within the curve of duodenum tail touches the spleen

Question 42

features of the exocrine pancreas

Answer 42

majority of the tissue has an acinar arrangemtn complex ductal collecting system, ends at the pancreatic duct and empties into duodenum secrete pancreatic juice (digestive enzymes and sodium bicarbonate)