GI tract

Question 1

give an overview of the GI tract

Answer 1

• Mouth to Anus
• Mostly abdominal
• Oral cavity + pharynx (head and neck)
• Oesophagus (neck, thorax, abdomen)
• Rectum + anal canal (pelvic cavity)
• Muscle tube with common structure
• Tract + accessory organs = Gastrointestinal system
  Alimentary/digestive/gastrointestinal

Question 2

describe the upper vs lower GI tract

Answer 2

upper :
Mouth
Pharynx
Oesophagus
Stomach
Duodenum
Lower:
Jejunum + ilium
Colon
Ascending, Transverse, Descending
Sigmoid
Rectum

• seperated by suspensory muscle of duodenum

Question 3

describe the vasculature and innervation of the 3 parts of the gut

Answer 3

Question 4

label this schematic diagram of the head

Answer 4

Question 5

draw a diagram to show the pathways of air and food via the cavities in the head

Answer 5

green - air
grey - food

Question 6

what are the components of the oral cavity ?

Answer 6

• space within the mouth and it is broken up into the oral vestibule and oral cavity proper by the teeth and gums
• provides mechanical digestion from teeth and tongue

Question 7

describe the 3 parts of the pharynx

Answer 7

Nasopharynx (should not be food here!)
* Inferior edge of soft palate
Oropharynx (posterior to oral cavity)
* Superior border of epiglottis
Laryngopharynx (air passes to larynx, food to oesophagus

Question 8

what is the abdomen ?

Answer 8

• portion of trunk between thorax and pelvis enclosing abdominal cavity
• diaphragm separates cavity from thorax
• continuous with pelvic cavity - makes abdominopelvic cavity
• cavity is not protected by bone , mostly muscle and aponeurosis.

Question 9

what are the abdominal quadrants ?

Answer 9

• Medial plane sagittal
• Transumbilical plane transverse
• Goes through umbilicus

Question 10

what are the abdominal regions ?

Answer 10

• provide more accuracy than quadrants
• 2 Sagittal planes
• Midclavicular
• Transverse:
• Subcostal: inferior borders of 10th costal cartilage
• Transtubercular: iliac tubercles + 5th lumbar vertebrae

note - flank can also be referred to as lumbar and groin referred to as inguinal

Question 11

label the abdominopelvic cavity

Answer 11

Question 12

what is the peritoneal cavity ?

Answer 12

• space within the abdomen that lies between the parietal peritoneum (lining the abdominal wall) and the visceral peritoneum (covering the abdominal organs).
• It is a potential space that normally contains a small amount of lubricating fluid to reduce friction between organs as they move.
• Parietal: somatic innervation, lines walls
• Visceral: referred pain, lines organs

Question 13

what the types of peritoneal organs ?

Answer 13

Intraperitoneal:
* Suspended in the peritoneal cavity
* Surrounded by visceral peritoneum
Retroperitoneal:
* Organs outside the peritoneal cavity
* Only one or part of one surface covered by visceral peritoneum
Secondarily retroperitoneal:
* Started intraperitoneal, moved to retroperitoneal
* Surgical mobilization?

Question 14

what is a peritoneal fold ?

Answer 14

double layer of peritoneum (the thin membrane lining the abdominal cavity) that connects or suspends organs within the abdomen. These folds contain blood vessels, lymphatics, and nerves that supply the organs they are associated with.

Question 15

what are the 3 types of peritoneal folds ?

Answer 15

Mesenteries:
* Attach viscera to posterior abdominal wall
* Conduit for vessels, nerves, lymphatics
Omenta:
* Double layer of peritoneum
* Connect stomach to other viscera
* Greater and lesser omentum, correspond to curvatures of the stomach
Ligaments:
* Double folds of peritoneum
* Connect viscera to abdominal walls

Question 16

what is a peritoneal recess ?

Answer 16

Small pockets formed by peritoneal folds, which can sometimes trap fluid or infections.

Question 17

what are the viscera in the upper and lower digestive tract ?

Answer 17

Upper:
part of oesophagus
stomach
duodenum

lower:
jejunum
ileum
colon

Question 18

what are the typical GI tract layers?

Answer 18

• 4 layers from innermost to outermost:

mucosa

submucosa:
* dense connective tissue, blood vessels, lymphatics, and nerves
* Supports mucosa and helps regulate secretion and absorption.

Muscularis Externa (Muscular Layer):
* Inner circular muscle – Controls lumen diameter and helps in segmentation.
* Outer longitudinal muscle – Aids in peristalsis (wave-like movements).
* Myenteric (Auerbach’s) plexus – Nerve network that controls gut motility.
* Submucosal plexus

Serosa (or Adventitia) (Outermost Layer):
* Serosa – Found in intraperitoneal organs; a slippery layer of visceral peritoneum reducing friction.
* Adventitia – Found in retroperitoneal organs; a fibrous connective tissue layer anchoring the organ in place.

Question 19

describe the oesophagus

Answer 19

Question 20

describe the stomach

Answer 20

Question 21

describe the duodenum

Answer 21

Question 22

describe the jejunum and ileum

Answer 22

Question 23

describe the cecum and appendix

Answer 23

• Dilated pocket of large intestine with dead end
  Evolutionary remnant?
• Also the little cu-de-sac of the veriform appendix

Question 24

describe the colon

Answer 24

Question 25

label these colon features

Answer 25

Question 26

describe the liver

Answer 26

* Right upper quadrant * 4 lobes * Partly covered by thoracic cage * Multitude of functions including bile production * Gallbladder attached to inferior surface

Question 27

describe the pancreas

Answer 27

* A mixed exocrine and endocrine gland * Located on the posterior abdominal wall * Head is enclosed by the loop of the duodenum * Tail is located in the hilum of the spleen * Insulin produced in the islets of Langerhans

Question 28

describe the spleen

Answer 28

Lymphatic organ Left upper quadrant / left hypochondrium Protected by 9th – 11th ribs

Question 29

describe the coeliac trunk and its branches

Answer 29

* Coeliac Trunk (Major Branch of Abdominal Aorta) * Left Gastric Artery – Supplies lesser curvature of the stomach * Splenic Artery – "Wiggly" (tortuous), supplies spleen, pancreas, and stomach * Short Gastric Arteries – Supply fundus of stomach * Left Gastro-Omental Artery – Supplies greater curvature * Common Hepatic Artery – Divides into: * Proper Hepatic Artery – Supplies liver * Gastroduodenal Artery – Supplies stomach & duodenum

Question 30

describe the vessels of the mesentary

Answer 30

Superior Mesenteric Artery (SMA) * "Pops over" the left renal vein (can compress it → Nutcracker Syndrome) Supplies midgut, including: * Duodenum (via Inferior Pancreaticoduodenal Artery) * Jejunum & Ileum (via Jejunal & Ileal Arteries) – Fan out in mesentery

Question 31

describe the colon blood supply

Answer 31

Major Arteries for Colon Supply: * Ileocolic Artery – Supplies cecum and appendix * Right Colic Artery – Supplies ascending colon * Middle Colic Artery – Supplies transverse colon * Left Colic Artery – Supplies descending colon * Branches into ascending and descending branches * Sigmoid Branches – Supply sigmoid colon * Superior Rectal Artery – Supplies rectum

Question 32

describe the portal venous system

Answer 32

* "Border control" for blood from GI tract, accessory organs, and spleen * Carries oxygen-poor, nutrient-rich blood * All blood is directed to the liver for detoxification, processing, and nutrient storage * Hepatic veins drain the processed blood into the Inferior Vena Cava (IVC)

Question 33

describe innervation of the gut

Answer 33

Parasympathetic Innervation: * Vagal branches (CN X) – Increase secretion and motility in the GI tract * Pelvic splanchnic nerves (S2, S3, S4) – Supply distal colon, rectum Sympathetic Innervation: * Inhibits motility (slows down digestion) * Reduces secretion and blood flow to the GI tract

Question 34

label these referred pain areas

Answer 34

Question 35

what are the boundaries of the parts of the gut ?

Answer 35