The anal canal and sphincter complex are often oversimplified, but the alternative perspectives on this anatomic region and its histologic characteristics influence how anal cancer pathology is conceptualized and ultimately treated. In this chapter, we highlight the divergent definitions and complexity of anal canal anatomy, review the anatomic and functional configuration of the pelvic floor and anal sphincter musculature, delineate histologic characteristics of the anal canal and perianal skin, and describe the distinct vascular and lymphatic drainage patterns of the anal canal and perianal skin.
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The anal canal is located within the anal triangle of the perineum between the right and left ischioanal fossae. It is the final segment of the gastrointestinal tract, around 4cm in length. The canal begins as a continuation of the rectum and passes inferoposteriorly to terminate at the anus.4,7/5(59) The article also highlights the recent histological and anatomical changes to the traditional terminology of the anal canal. The terminology has been adopted by the American Joint Committee on Cancer, separating the anal region into the anal canal, the perianal region and the radious.net by: 7 The anal canal is the last part of the gastrointestinal tract. It is about 3 to 4 cm long and lies completely extraperitoneally. It begins at the anorectal junction distally from the perineal flexure and ends at the anus. It is divided into three anatomical zones; columnar, intermediate and radious.netons: Fecal continence and defecation
Authors Authors and affiliations Margaret H. Sundel Lysandra Voltaggio Ira L. Leeds Sandy Hwang Fang. Chapter First Online: 20 July Keywords Anus Anal Anal canal Anal anatomy Anal histology.
Abbreviations RAIR Rectoanal inhibitory reflex S2-S4 Sacral nerves S2-S4. This is a preview of subscription content, log in to check access.
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Anal canal histology
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As discussed above, the pectinate line divides the anal canal into two parts - which have a different arterial supply, venous drainage, innervation and lymphatic drainage. Haemorrhoids are vascular cushions found within the anal canal of healthy individuals, which help with the maintenance faecal continence.
The rectum is the last part of the large intestine and connects the sigmoid colon to the anal canal. The rectum begins at the height of S2-S3 and ends at the perineum. It is about 12 to 16 cm long und may be subdivided into three parts: The upper third lies intraperitoneally Inflammatory processes and non-neoplastic lesions A number of inflammatory and infectious processes may affect the anal canal; the histologic findings of anal fissures and ulcers, abscesses, and fistulas are not particularly distinctive and are discussed only briefly. Infectious agents that can affect the anorectum include human papillomavirus (HPV; discussed later in the condyloma Estimated Reading Time: 9 mins Histology of the anal canal The normal gross and microscopic morphology of the anal canal is described, including the more common variants. Constant problems in the literature are the confusing terminology and the relation of the histological zones to the so-called cloacal membrane. For this reason, the review includes remarks Cited by:
If they become swollen and distended, they are referred to as pathological haemorrhoids. Pathological haemorrhoids are observed in people who suffer from constipationprolonged straining when defecating, or raised intra-abdominal pressure e.
g pregnancy, ascites. They can cause bleeding and itchiness, and depending on the severity, can be managed conservatively or surgically.
In this article, we shall look at the anatomy of the anal canal - its position, structure, relations and neurovascular supply. At the junction of the rectum and the anal canal, there is a muscular ring - known as the anorectal ring.
Above the anal valves are small pouches which are referred to as anal sinuses - these contain glands that secrete mucus. The anal valves collectively form an irregular circle - known as the pectinate line or dentate line.
Perineal body. Bulb of the penis Perineal body.
Neurovascular Supply and Lymphatics As discussed above, the pectinate line divides the anal canal into two parts - which have a different arterial supply, venous drainage, innervation and lymphatic drainage. Anastomosing branches from the middle rectal artery.
How to Draw Easily Anal Canal Histology
Inferior rectal artery branch of the internal pudendal artery. Venous Drainage Superior rectal vein, which empties into the inferior mesenteric vein portal venous system.
Clinical AJCC definition of anal canal: Begins at puborectalis sling at apex of anal sphincter complex (palpable as anorectal ring but difficult for pathologists to identify) Ends at squamous mucocutaneous junction with perianal skin; includes 1 - 2 cm of rectal type glandular mucosa and possibly transitional mucosa at dentate line A thorough understanding of anal cancer necessitates a nuanced comprehension of the anatomy involved. The anal canal and sphincter complex are often oversimplified, but the alternative perspectives on this anatomic region and its histologic characteristics influence how anal cancer pathology is conceptualized and ultimately radious.net by: 2
Inferior rectal vein, which empties into the internal pudendal vein systemic venous system. Nerve Supply Visceral innervation via the inferior hypogastric plexus. Somatic innervation via the inferior rectal nerves branches of the pudendal nerve.
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Sensitive to pain, temperature, touch and pressure. Lymphatics Internal iliac lymph nodes Superficial inguinal lymph nodes [start-clinical].
The Anal Canal Home The Abdomen The Gastrointestinal Tract The Anal Canal. star star star star star.
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Anatomical Position The anal canal is located within the anal triangle of the perineum between the right and left ischioanal fossae. Anatomical Structure Except during defecation, the anal canal is collapsed by the internal and external anal sphincters to prevent the passage of faecal material.
It is formed from a thickening of the involuntary circular smooth muscle in the bowel wall. It blends superiorly with the puborectalis muscle of the pelvic floor.
By TeachMeSeries Ltd Anatomical Relations The anal canal lies in close proximity to several other important structures in the pelvis and perineum: Anteriorly Posteriorly Laterally Male Female Anococcygeal ligament Coccyx and sacrum Ischioanal fossae Perineal body Urogenital diaphragm Urethra Bulb of the penis Perineal body Urogenital diaphragm Vagina.
Neurovascular Supply and Lymphatics As discussed above, the pectinate line divides the anal canal into two parts - which have a different arterial supply, venous drainage, innervation and lymphatic drainage. Modality Above Pectinate line Below Pectinate line Arterial Supply Superior rectal artery branch of inferior mesenteric arter y Anastomosing branches from the middle rectal artery.
Inferior rectal artery branch of the internal pudendal artery Anastomosing branches from the middle rectal artery.
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Sensitive to stretch. Somatic innervation via the inferior rectal nerves branches of the pudendal nerve Sensitive to pain, temperature, touch and pressure. Lymphatics Internal iliac lymph nodes Superficial inguinal lymph nodes Clinical Relevance - Haemorrhoids By Dr.
Gunther [CC BY 3. print Print this Article. The anal canal is the final segment of the gastrointestinal tract.
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It has an important role in defecation and maintaining faecal continence. close Rate this article. close Edit this article. Found an error?