The Gastrointestinal System Notes

Question 1

Embryology

Foregut

Answer 1

• Endodermal derivative.
• Anterior part of embryonic alimentary canal.
• Develops into esophagus, stomach, pharynx, and extreme anterior
  part of the intestine

Question 2

Embryology

Midgut

Answer 2

• Endodermal derivative.
• Middle part of embryonic alimentary canal.
• Develops into distal part of duodenum, jejunum, ileum, cecum, and
  appendix, ascending colon, and most of the transverse colon.

Question 3

Embryology

Hindgut

Answer 3

• Endodermal derivative.
• Posterior part of embryonic alimentary canal.
• Develops into distal transverse colon, descending colon, sigmoid
  colon, rectum, and super anal canal.
• Bladder and urethral epithelium come from this tissue.

Question 4

Embryology

Proctoderm

Answer 4

• Ectodermal derivative.

*Develops into final third of anal canal.

• Where it connects to hindgut, roughly forms the pectinate line.

Question 5

Histology

Smooth Muscle

Answer 5

• Fibers are fusiform, consisting of elongated cells that have tapered
  ends.
• Contraction gives cork-screw appearance.
• Has no striations, no T tubules, and no troponin.
• Regulated by autonomic nervous system and hormones (thus,
  referred to as involuntary muscle).
• Located in dermis of the skin, and in vessel and visceral walls.