External anal sphincter
Musculus sphincter ani externus
Closes the anus.
About the external anal sphincter of the horse
External anal sphincter is a muscle of the body (trunk), a single structure on the midline. Its name in the Nomina Anatomica Veterinaria is Musculus sphincter ani externus. You can turn it above, see it in place in the body of the horse, and open it inside the whole animal in Vetomica.
Where it runs from and to
A muscle is told apart from its neighbours by what it takes hold of at each end, which is also what decides what it does when it shortens.
- Origin
- The fascia of the tail beneath the first caudal vertebrae.
- Insertion
- It rings the anus and blends below it with the muscles of the perineum.
- Action
- Closes the anus.
- Nerve
- The caudal rectal branches of the pudendal nerve.
Written for Vetomica in its own words from the standard reference anatomy of the horse; the books it was checked against are listed below.
Terminology
- English
- External anal sphincter
- Latin (NAV)
- Musculus sphincter ani externus
- Status
- A valid term in the Nomina Anatomica Veterinaria
Questions about the external anal sphincter
- What is the Latin name of the external anal sphincter?
- In the Nomina Anatomica Veterinaria, the external anal sphincter is called Musculus sphincter ani externus.
- Where is the external anal sphincter of the horse?
- External anal sphincter is a muscle of the body (trunk), a single structure on the midline.
- Where does the external anal sphincter originate and insert?
- Origin: The fascia of the tail beneath the first caudal vertebrae. Insertion: It rings the anus and blends below it with the muscles of the perineum.
- What nerve supplies the external anal sphincter?
- The caudal rectal branches of the pudendal nerve.
- What does the external anal sphincter do?
- Closes the anus.
See the external anal sphincter inside the whole horse.
Vetomica opens on this structure with every layer of the horse around it: peel back the skin and the muscles, cut a section through it, X-ray it, and practise naming it until you stop getting it wrong.
Free for 7 days, no card. After that the skeletons stay free.
