GIT anat

• Cholesterol gallstones are the most common type of gallstone, and can't be seen with Xray
• Burning, localised epigastric pain suggests peptic ulcer.
• The deep ring of the inguinal canal occurs in the same layer which gives rise to the internal spermatic fascia
• The lesser omentum attaches the liver to the stomach
• The presynaptic sympathetic cell body is located T1-L2/L3
• Layers of the anterior abdominal wall

  Skin

  Superficial fatty layer of Camper's Fascia

  Deep membranous layer of Scarpa's Fascia

  External Oblique muscle

  Internal Oblique muscle

  Rectus Sheath

  Rectus abdominis

  Transversus Abdominis muscle

  Transversalis Fascia

  Parietal Peritoneum
• Arcuate line


  demarcation point midway between umbilicus and pubic symphysis
• Above arcuate line

  rectus sheath has both anterior and posterior components
• Below arcuate line


  posterior rectus sheath ends and all muscles become anterior
• Under sheath is transversalis fascia then extraperitoneal fat then parietal peritoneum.
• Median fold is obliterated foetal urachus
• Medial fold is obliterated foetal umbilical arteries
• Lateral fold is functional inferior epigastric arteries
• Borders of inguinal triangle

  -Inferior border:inguinal ligament

  -Medial border:lateral border of rectus abdominis

  -Lateral border:inferior epigastric artery
• What is a direct inguinal hernia?


  Hernias that arise in the inguinal triangle (as they are medial to the inferior epigastric artery)

  Results in potential weakness in anterior abdominal wall
• What is the difference between direct and indirect hernia?

  Direct- A direct inguinal hernia penetrates directly through the wall of your inguinal canal. This type of hernia occurs in adults over time, from a combination of weakening abdominal muscles and chronic pressure in the muscle wall.

  Indirect- An indirect inguinal hernia enters your inguinal canal through the top. This usually occurs because of a birth defect. In some fetuses, the opening to their canal doesn't close all the way during development in the uterus
• Layers of the testes, as it descends

  From superficial to deep, these layers are:

  -Dartos fascia(from Scarpa's fascia)

  -External spermadic fascia(from external oblique)

  -Cremaster muscle and fascia(from internal oblique)

  Fascia surrounds the muscle

  -Internal spermadic fascia(from transversalis fascia)

  -Tunica vaginalis(from peritoneum)
• What is the layer that is not dragged down by the testes and why?

  Transverse abdominus(too superficial)
• Spermatic cord


  Beginning in the inferior abdomen and ending in scrotum

  Spermatic cord is formed at the opening of the inguinal canal, known as the deep inguinal ring(lateral to inferior epigastric vessels)
• Ectopic testis


  where one of the testicles has not descended into the scrotum as normal, but instead has taken a different path and has descended through the abdominal cavity until it has settled in the pre-pubic area in the inguinal canal, instead of in the scrotum
• scrotum drainage


  The lymphatic fluid from the scrotum drains to the nearby superficial inguinal nodes
• Testes drainage


  Since the testes are originally retroperitoneal organs, the lymphatic drainage is to the lumbar and para-aortic nodes, along the lumbar vertebrae.
• What are derivatives of endoderm?

  Epithelium, parenchyma and glands
• What are derivatives of the mesoderm?

  Lamina propria, blood vessels, muscularis mucosae, submucosal connective tissue, muscularis externa, adventitia
• What are derivatives of the ectoderm?


  Enteric nerves
• Foregut

  Organs-Oesophagus to ampulla of vater in the duodenum

  Arterial supply- Celiac trunk(T12)
• Midgut

  Organs- Ampulla of vater to 2/3rds into T. colon

  Arterial supply- SMA(L1)
• Hindgut

  Organs- 2/3rds into T colon to rectum

  Arterial supply- IMA(L3)
• What does the dorsal mesentary of the stomach become?

  Greater omentum
• What does the ventral mesentary of the stomach become?

  Falciform ligament
• What is the mesentary between stomach and liver?


  Lesser omentum
• What organ drives the rotation of the foregut?


  Liver, grows at such a fast pace, rotates clockwise
• Pancreas development

  1. Pancreas formed from 2 separate outgrowths, the ventral (uncinate part of pancreas) and dorsal pancreatic bud
  2. As the gut tube rotates, it brings around both to meet each other and fuse together
• Annular pancreas

  Failure for the 2 buds to merge can cause as annular pancreas wherein the buds fuse around the duodenum obstructing it

  Clinical presentation-Feeding problems, abdominal distension, vomiting
• Stomach development

  1. Dilation of foregut
  2. Rotates 90 degrees, left side becomes ventral, right side posterior (explains how left vagus nerve is ventral, right is posterior)
  3. Ventral mesentary becomes lesser omentum, dorsal becomes greater omentum
• What is the origin of lower duodenum?

  cranial part of midgut
• Midgut embryology


  1. Elongates rapidly

  2. Forms U shaped loop that herniates through the umbilicus to the outside

  3. Cranial (jejunum and upper ileum) and caudal loop (lower ileum → proximal T. Colon) forms

  4. Middle of U loop attached to vitelline duct (a remnant of the yolk sac) that will later obliterate (if fails this is Meckel's diverticula)

  5. Whilst herniated it rotates 90 degrees counterclockwise so that the caudal loop sits on the lower side

  6. Contents returns inside then completes another 180 degrees counterclockwise rotation so that the appendix ends up in the RUQ

  7. The colon grows downwards, bringing the appendix into the RIF
• Rotation of foregut, degrees

  90 degrees clockwise on its longitudinal axis
• Rotation of midgut, degrees

  270 degrees counterclockwise around SMA
• Omphalocele

  Abdo viscera herniates through umbilicus

  The viscera is covered by the amniotic membrane and peritoneum forming a hernia sac