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Analsphincters and Puborectalis – Perineum and External Genitalia

by James Pickering, PhD
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    00:01 I want to talk about anal sphincters for a moment and how we can control those sphincters and also puborectalis. What we have is a picture of hemisection through the rectum on this side and on the other side we have a transverse section through the pelvis.

    00:18 What we can see is that here we have anterior and here we have posterior in this transverse section. We have anterior and we have posterior here.

    00:29 Anterior in the male we have got the prostrate and then we have the rectum here.

    00:33 We can see the circular and longitudinal muscle layers of the rectum here.

    00:38 What we can also see is that coming around, if you look at this transverse image, coming around from anteriorly we have this sling like arrangement.

    00:51 And this sling like arrangement coming from the pubic bones on both the left and the right side is puborectalis of levator ani. Puborectalis, it comes from the pubic bone and it sweeps around the rectum. It's coming in this direction in this direction here and then it's going to sweep around sweep around the rectum and then it going to go and attach to the other pubic bone. So it create this sling. Now that is contracted and that creates this angle.

    01:26 Creates this angle called the anorectal angle which is maintained by puborectalis and this once again helps to control defecation.

    01:39 Relaxation of this muscle will straighten that angle and ease defecation. We also have a number of other muscles that are involved in maintaining fecal continent.

    01:51 And we have external and internal anal sphincters and we can see these here. If we look at the internal anal sphincter The internal anal sphincter is going to be a thickening of the circular and longitudinal muscles which we have running around the rectum. So we have a thickening of these smooth muscles so we can see these running around in here. We have a thickening of these muscles and they form the internal anal sphincter. These are going to to be controlled by the autonomic nervous system which means we are not consciously aware of them.

    02:35 That is being controlled unconsciously we are not in conscious control. We then have an external anal sphincter and we are in control of this sphincter.

    02:46 The external anal sphincter muscle is a striated muscle and it's divided into various parts. We have deep parts. We have superficial parts and we have subcutaneous parts.

    02:56 We can also see we have puborectalis here as well helping to maintain fecal continent.

    03:04 Its a ring that goes around the rectum we can see it sorry, its a ring that goes around the rectum we can see around here. And that surrounds the opening of the anus and we can see that going all the way around.

    03:18 External anal sphincter, deep part, superficial and subcutaneous parts.

    03:25 Importantly this is controlled by the somatic nervous system.

    03:29 And when we have the urge to defecate we can control this and we can keep this sphincter shut until an appropriate point.

    03:38 I have mentioned puborectalis we can draw that again, a sling like muscle originating from the pubis. It's formed as levator ani, the pelvic floor and it blends with the external anal sphincter. It passes posterior to the anorectal junction creating that anorectal angle.

    03:56 And this is important in maintaining the fecal continent.


    About the Lecture

    The lecture Analsphincters and Puborectalis – Perineum and External Genitalia by James Pickering, PhD is from the course Pelvis.


    Included Quiz Questions

    1. Puborectalis
    2. Pubococcygeus
    3. Ileococcygeus
    4. Coccygeus
    1. Greater vestibular glands
    2. External urethral sphincter
    3. Intermediate part of the male urethra
    4. Bulbourethral glands

    Author of lecture Analsphincters and Puborectalis – Perineum and External Genitalia

     James Pickering, PhD

    James Pickering, PhD


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