Clinical anatomy : internal and external hemorrhoids

 Hemorrhoids, also known as piles, are vascular structures located in the anal canal. They consist of clusters of blood vessels, smooth muscle, and connective tissue.

Anatomically, hemorrhoids are classified into two main types:

1. Internal Hemorrhoids: These hemorrhoids originate above the dentate line within the anal canal. The dentate line is a transitional area between the internal and external lining of the anal canal. Internal hemorrhoids are covered by a mucous membrane, which lacks pain receptors, hence they are usually painless unless they prolapse and become thrombosed. Internal hemorrhoids are supplied by branches of the superior rectal artery, which is a branch of the inferior mesenteric artery, making them part of the portal venous system. Increased pressure in the portal venous system, such as due to constipation or straining during bowel movements, can cause dilation and swelling of these veins, leading to the development of internal hemorrhoids.

2. External Hemorrhoids: These hemorrhoids originate below the dentate line and are covered by anoderm, which contains pain receptors. External hemorrhoids are supplied by branches of the inferior rectal artery, which is a branch of the pudendal artery, making them part of the systemic venous system. Factors such as increased intra-abdominal pressure or pregnancy can lead to enlargement and inflammation of these veins, contributing to the development of external hemorrhoids. External hemorrhoids may cause pain and discomfort, especially during bowel movements or when irritated.

Both internal and external hemorrhoids can become symptomatic when they swell, prolapse, thrombose, or become inflamed. Symptoms may include rectal bleeding, itching, discomfort, and pain. Treatment options range from conservative measures such as dietary modifications, topical treatments, and lifestyle changes to more invasive interventions like rubber band ligation, sclerotherapy, or surgical excision, depending on the severity and symptoms of the hemorrhoids.

Summary of internal and external hemorrhoids

Internal Hemorrhoids:

1. Origin: Above the dentate line in the anal canal.

2. Lining epithelium : it is covered by simple columnar epithelium 

3. Nerve Supply: it is supply by  Autonomic nerves, so it is typically painless.

4. Blood Supply: Superior rectal artery from the portal venous system.

5. Causes: Increased portal venous pressure from factors like constipation or straining during bowel movement.

External Hemorrhoids:

1. Origin: Below the dentate line in the anal canal.

2. Lining epithelium : it is covered by stratified squamous epithelium 

3. Nerve Supply: it is painful because it is supplied by  Somatic nerves, particularly the pudendal nerve.

4. Blood Supply: Inferior rectal artery from the systemic venous system.

5. Causes: Increased intra-abdominal pressure or pregnancy-related factors leading to enlargement and inflammation.