Chapter 94: Rectum, Anus and Perineum Flashcards
What is unique about the resting membrane potential in GI smooth muscle cells?
The resting membrane potential is not constant. It oscillates in slow waves over time, generated by pacemaker cells called the interstitial cells of Cajal
How many bacteria are there per gram of feces?
10^9 bacteria per gram of feces
- Up to 90% anaerobes
Where is the most common location for a perineal hernia in dogs?
Between external anal sphincter and levator ani
What anatomical difference is there regarding the perineum in dogs and cats?
Cats do not have a sacrotuberous ligament
Where is the colorectal junction? The rectoanal junction?
Colorectal is arbitrary but the entry of the cranial rectal artery can be used as a point.
Rectoanal is ventral to 2nd or 3rd caudal vertebrae (also where the mesorectum ends).
Intraperitoneal rectum has what four layers?
Mucosa
Submucosa
Muscularis (has inner circular and outer longitudinal layers)
Serosa
What is different about retroperitoneal rectum vs intraperitoneal?
It LACKS serosa
What is the main blood supply to the rectum?
Cranial rectal artery
The intrapelvic has poorer supply in dogs, but in cats the middle and caudal rectal aa. step up)
How long is the anal canal?
1-2 cm, beneath the 4th caudal vertebra
What muscles surround the anal canal?
Smooth internal and striated external anal sphincter.
What is the anorectal line?
Where columnar rectal epithelium changes to stratified squamous (cutaneous) zone
Where do the anal sac ducts open through?
The cutaneous zone.
Blood supply to the anus?
Right and left caudal rectal aa. and branches of the internal pudendal.
**Cranial rectal artery too **
Where does venous drainage from the anus end up?
CVC and Portal systems
Where does the lymph drainage of the anus go?
Sacral, medial and internal iliac nodes.
