Source of epistaxis after ligation of external carotid artery is –
**Core Concept**
The source of epistaxis (nosebleed) can be attributed to the rich blood supply of the nasal mucosa, primarily derived from the sphenopalatine artery, a branch of the maxillary artery, which in turn is a branch of the external carotid artery. However, the sphenopalatine artery also receives some blood supply from the ophthalmic artery, a branch of the internal carotid artery.
**Why the Correct Answer is Right**
The ophthalmic artery, which is a branch of the internal carotid artery, supplies blood to the nasal mucosa through its posterior ethmoidal and anterior ethmoidal branches. These branches anastomose with the sphenopalatine artery, which is a branch of the external carotid artery. Therefore, ligation of the external carotid artery may not completely eliminate the blood supply to the nasal mucosa, allowing epistaxis to persist. This is because the ophthalmic artery provides an alternative source of blood supply.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided, so we cannot evaluate its accuracy.
* **Option B:** This option is not provided, so we cannot evaluate its accuracy.
* **Option C:** This option is not provided, so we cannot evaluate its accuracy.
* **Option D:** This option is not provided, so we cannot evaluate its accuracy.
**Clinical Pearl / High-Yield Fact**
The ophthalmic artery's contribution to the blood supply of the nasal mucosa highlights the importance of considering alternative sources of blood supply when managing epistaxis, particularly in cases where the external carotid artery has been ligated.
**Correct Answer: D. The ophthalmic artery.**