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Questions and Answers
Which artery supplies blood below the pectinate line?
What is the main venous drainage pathway for hemorrhoids located above the pectinate line?
Which nerve is responsible for the sensation of touch and temperature below the pectinate line?
Which lymph nodes drain lymphatic fluid from above the pectinate line?
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What makes the internal haemorrhoidal plexus prone to varices?
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What artery supplies the area below the pectinate line?
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Which lymphatic drainage route is associated with the area below the pectinate line?
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What is the primary nervous supply for the region above the pectinate line?
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What is a significant characteristic of the inferior rectal artery?
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What type of sensitivity is provided by the inferior anal nerve?
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What is the arterial supply for the area above the pectinate line?
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Which lymphatic drainage route is associated with the area below the pectinate line?
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What type of sensitivity is associated with the inferior hypogastric plexus?
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Which vein does the internal haemorrhoidal plexus drain into?
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What is the venous drainage pattern for hemorrhoids located below the pectinate line?
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Study Notes
Dentate/Pectinate Line
The dentate line is a transition zone between the anal canal and rectum, marked by a change from columnar to stratified squamous epithelium. It divides the anal canal into superior and inferior sections, each with distinct blood supply, drainage, and innervation.
Arterial Supply: Above: superior rectal artery (from inferior mesenteric artery); Below: middle rectal artery (internal iliac) and inferior rectal artery (internal pudendal).
Venous Drainage: Above: internal haemorrhoidal plexus to inferior mesenteric vein; Below: external haemorrhoidal plexus to internal iliac vein.
Lymphatic Drainage: Above: internal, common iliac, and lumbar lymph nodes; Below: superficial inguinal lymph nodes.
Nervous Supply: Above: inferior hypogastric plexus; Below: inferior anal nerve (pudendal).
Dentate/Pectinate Line
- The dentate line is the transition zone between the upper and lower anal canal.
- Above the dentate line, the anal canal is lined by columnar epithelium and supplied by the superior rectal artery.
- Below the dentate line, the anal canal is lined by stratified squamous epithelium and supplied by the middle and inferior rectal arteries.
- The venous drainage of the anal canal above the dentate line is via the internal haemorrhoidal plexus, which drains into the superior rectal vein and ultimately the inferior mesenteric vein. This arrangement is prone to varices due to portal hypertension.
- The venous drainage below the dentate line is via the external haemorrhoidal plexus, which drains into the inferior and middle rectal veins and ultimately the internal iliac vein.
- The lymphatic drainage above the dentate line is to the internal iliac, common iliac, and lumbar lymph nodes.
- The lymphatic drainage below the dentate line is to the superficial inguinal lymph nodes.
- The nervous supply above the dentate line is from the inferior hypogastric plexus, which is only sensitive to stretch.
- The nervous supply below the dentate line is from the inferior anal nerve, a branch of the pudendal nerve. This nerve is sensitive to touch, pain and temperature.
### Dentate/Pectinate Line
- The dentate line, also called the pectinate line, is a significant anatomical landmark in the anal canal.
- This line marks the transition between the upper and lower anal canal.
- It's characterized by a change in tissue type, from the columnar epithelium above to squamous epithelium below.
Arterial Supply
- Above the dentate line: The superior rectal artery, a branch of the inferior mesenteric artery (IMA), provides arterial supply.
- Below the dentate line: The middle rectal artery, branching from the internal iliac artery, and the inferior rectal artery, originating from the internal pudendal artery, supply blood.
Venous Drainage
- Above the dentate line: Venous drainage occurs through the internal hemorrhoidal plexus. This plexus drains into the superior rectal vein, which subsequently joins the inferior mesenteric vein (IMV).
- Below the dentate line: The external hemorrhoidal plexus drains into the inferior and middle rectal veins, ultimately connecting to the internal iliac vein.
- The internal hemorrhoidal plexus is prone to varices, forming hemorrhoids, due to increased pressure caused by portal hypertension.
Lymphatic Drainage
- Above the dentate line: Lymph drains to the internal iliac nodes, continuing to the common iliac nodes and eventually reaching the lumbar lymph nodes.
- Below the dentate line: Lymph drains to the superficial inguinal lymph nodes.
Nervous Supply
- Above the dentate line: The inferior hypogastric plexus provides innervation. Pain and temperature sensations are not present.
- Below the dentate line: The inferior anal nerve, stemming from the pudendal nerve, is responsible for touch, pain, and temperature sensations.
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Description
Test your knowledge about the dentate line, a crucial anatomical landmark that separates the anal canal from the rectum. Explore its significance regarding arterial supply, venous drainage, and related clinical implications such as hemorrhoids. Assess your understanding of the vascular anatomy associated with this region.
