C13 - The hindgut of carnivores and pigs, blood supply and innervation

Question 1

Define hindgut

Answer 1

• The caudal portion the the embryonic gut which develops into the colon and the rectum​
• Begins at the cecum
• Ends at the anus

Question 2

Give the portions of the hindgut

Answer 2

1. Cecum (​Right side of the abdominal cavity, except from in pig)
2. Colon
3. Rectum (Partly inside, partly outside the abdomen)

Question 3

Caecum

Dog and swine

Answer 3

• Basis caeci (Dorsal dilation of cecum, eq)
• Corpus caeci
• Apex caeci
• Curvatura caeci major
• Curvatura caeci minor
• Teniae caeci (eq, su) (Bands of cecum)
  
  • Tenia dorsalis (Ø su)
  • Tenia ventralis
  • Tenia medialis
  • Tenia lateralis
• Haustra caeci (eq, su) (Sacculations of the cecum between the teniae and between the plica semilunares)
• Ostium caecocolicum (Opening between cecum → colon)
• Valva caecocolica (eq)
• M. sphincter caeci (ca, bo, su)
• Plica iliocolica (Attaches to tenia dorsalis)
• Plica caecocolica (C**olon ventrale dextrum → tenia lateralis of the caecum)
• Dog:
  
  • No haustra, no tenia
  • Right side, L2-L4
  • Caudal directed
  • Attached to ileum and colon ascendens by peritoneal folds
  • Communicate with colon ascendens at the ostium ileocaecolicaum
• Swine:
  
  • 3 haustra, 3 tenia (ø tenia dorsalis)
  • Left side
  • Apex in inguinal region

Question 4

Caecum

Give the interspecies differences

Answer 4

• Tenia caeci (eq, sus)
  
  • Tenia dorsalis (ø sus)
  • Tenia ventralis
  • Tenia medialis
  • Tenia lateralis
• Haustra caeci (eq, sus)
• Valva caecolica (eq)
• M. sphincter caeci (ø eq)
• Ca: ø haustra & tenia
• Ru: ø haustra & tenia
• Eq: 4 haustra & tenia
• Su: 3 huastra & tenia

Question 5

Colon

Dog

Answer 5

• Colon ascendens
  
  • ​Shortest of the three segments
  • Lateral: duodenum descendens and right lobe of pancreas
  • Medial: root of the mesentery
• Flexura coli dextra
• Colon transversum
  
  • ​Right → left, passes between stomach and a. mesenterica cranialis
  • Th12 level
• Flexura coli sinistra
• Colon descendens
  
  • ​Extends to the pelvic inlet, continued by the rectum
  • Longest of the three segments
  • Lies dorsally in the left half of the abdominal cavity
  • Related medially to duodenum ascendens: plica duodenocolica
• Location: dorsal in the abdomen

Question 6

Colon

Pig

Answer 6

• Colon ascendens
  
  • Ansa spiralis coli (Coiled on the left side of the mesentery)
    
    • Gyri centripetales (Moves towards flexura centralis)
    • Flexura centralis (Last in-going coil is continous with the first out-going coil)
    • Gyri centrifugales (Move away from flexura centralis towards ansa distalis coli)
  • Ansa distalis coli (Last part of colon ascendens)
• Colon transversum (Passing right → left direction, cranial to a. mesenterica cranialis)
• Colon descendens (Passes in a straight line to pelvic inlet, suspended by mesocolon descendens)
• Teniae coli (Bands of colon, formed by longitudinal muscles, Sus: 2)
• Haustra coli (Sacculation of the colon between tenia, and between plica semilunares)

Question 7

Rectum

Dog and swine

Answer 7

• Ampulla recti (enlargement of terminal part)
• Follows colon into the pelvic cavity, terminates at canalis analis
• Pelvic part of large intestines
• Most is covered with peritoneum
• Dog:
  
  • Short
  • L7 level
  • enters the pelvic cavity ventral to sacrum
  • In the retroperitoneal part of the pelvic cavity: ampulla recti
  • Outer muscle layer of rectum: m. retrococcygeus
• Swine:
  
  • Embedded in fat
  • Distinct ampulla recti before canalis analis

Question 8

Bloodsupply of the large intestines

Pig

Answer 8

• Caecum: a. ileocolica → a. caecalis
• Colon ascendens:
  
  • Gyri centripetalis: a. mesenterica cranialis → a. ileocolica → r. colicus
  • Gyri centrifugalis: a. mesenterica cranialis → a. colica dextra
  • R. colicus & a. colica dextra anastamoses at the flexura centralis
• Colon transversus: a. mesenterica cranialis → a. colica media
• Colon descendens: a. mesenterica caudalis → a. colica sinistra (anastamoses with a. colica media)
• Rectum: a. mesenterica caudalis → a. rectalis cranialis

Veins follow the pattern of the arteries, and drain into vena portae

Question 9

Bloodsuply of the large intestines

Dog

Answer 9

• Caecum: a. ileocolica → a. caecalis
• Colon ascendens:
  
  • a. ileocolica → r. colicus
  • a. mesenterica cranialis → a. colica dextra
• Colon transversus: a. mesenterica cranialis → a. colica media
• Colon descendens:
  
  • a. mesenterica caudalis → a. colica sinistra
  • a. colica media
• Rectum: a. mesenterica caudalis → a. rectalis cranialis

Question 10

Innervation

Answer 10

• Sympathetic
  
  • Decreased activity
  • Ggl. & plexus mesentericus cranialis
  • Ggl. & plexus mesentericus caudalis
• Parasympathetic:
  
  • Increased activity
  • Vagal nerves: supply intestines to the junction between colon transversus and colon descendens
  • Pelvic nerves: supply colon descendens and rectum