Review

. 2008 Sep;37(3):493-509, vii.

doi: 10.1016/j.gtc.2008.06.003.

Pelvic floor anatomy and applied physiology

Varuna Raizada¹, Ravinder K Mittal

Affiliations

Affiliation

¹ Pelvic Floor Function and Disorder Group, Division of Gastroenterology, University of California, GI-111D, San Diego VA Health Care Center, 3350 La Jolla Village Drive, San Diego, CA 92161, USA.

PMID: 18793993
PMCID: PMC2617789
DOI: 10.1016/j.gtc.2008.06.003

Review

Pelvic floor anatomy and applied physiology

Varuna Raizada et al. Gastroenterol Clin North Am. 2008 Sep.

. 2008 Sep;37(3):493-509, vii.

doi: 10.1016/j.gtc.2008.06.003.

Authors

Varuna Raizada¹, Ravinder K Mittal

Affiliation

¹ Pelvic Floor Function and Disorder Group, Division of Gastroenterology, University of California, GI-111D, San Diego VA Health Care Center, 3350 La Jolla Village Drive, San Diego, CA 92161, USA.

PMID: 18793993
PMCID: PMC2617789
DOI: 10.1016/j.gtc.2008.06.003

Abstract

Pelvic floor muscles have two major functions: they provide support or act as a floor for the abdominal viscera including the rectum; and they provide a constrictor or continence mechanism to the urethral, anal, and vaginal orifices (in females). This article discusses the relevance of pelvic floor to the anal opening and closure function, and discusses new findings with regards to the role of these muscles in the vaginal and urethra closure mechanisms.

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Figures

**Figure 1**
Figure 1a: Pelvic Floor Muscles Seen in the sagittal section of pelvis. Adapted from Thompson P. The Myology of the Pelvic Floor. Newton: McCorquoddale; 1899. Figure 1b: Pelvic floor muscles as seen from the perineal surface. Adapted from Thompson P. The Myology of the Pelvic Floor. Newton: McCorquoddale; 1899.

**Figure 2**
This schematic shows that the external anal sphincter is made up of subcutaneous, superficial and deep part. We believe that deep external anal sphincter is actually the puborectalis muscle (see text for explanation) Adapted from Frank.H.Netter, Atlas of Human Anatomy. Plate 393, 4^th ed, Philadelphia, PA : Saunders/Elsevier, c2006 with permission

**Figure 3**
A sketch of the external anal sphincter from a lateral view, as described by Shafik: External anal sphincter is described as made of 3 loops, basal loop (BL), intermediate loop (IL) and deep loop (DP). Note the relationship between the puborectalis muscle (PR) and DP. We believe that DP is actually the posterior part of the puborectalis muscle (see text for explanation). Adapted from Bogduk N. Issues in Anatomy: the external anal sphincter revisited. Aust N Z J Surg. Sep 1996;66(9):626–629, with permission.

**Figure 4**
Anatomy based on the MRI images: A: Coronal mid anal T2-weighted fast spin-echo (2,500/100) MR image obtained with an endoanal coil. B Corresponding drawing demonstrates the internal sphincter (IS), intersphincteric space (ISS), longitudinal muscle(LM), external sphincter (ES),puborectalis muscle (PR), and levator ani muscle (LA). These MRI images show that a part of the external anal sphincter is located below and a small portion surrounds the internal anal sphincter. Puborectalis muscle surrounds the upper part of the internal anal sphincter. Based on MR images it is quite clear that external anal sphincter consists of only 2 parts, subcutaneous (below the internal anal sphincter) and superficial (around the internal anal sphincter) (See text for explanation). Adapted from Stoker J, Halligan S, Bartram CI. Pelvic floor imaging. Radiology. Mar 2001;218(3):621–641, with permission.

**Figure 5**
Seated CT defecography, axial images of Puborectalis at rest (A), squeeze (B) and defecation (C). Note that the pelvic floor hiatus becomes smaller during squeeze and larger during defection. Adapted from Li D, Guo M. Morphology of the levator ani muscle. Dis Colon Rectum. Nov 2007;50(11):1831–1839, with permission.

**Figure 6**
MRI images at rest and squeeze in the mid sagittal plane: These images show movements of the anorectal angle and levator plate (formed by the ileococcygeus muscle): Sagittal at rest (A) and straining (B) showing the changes in the different components of the levator ani (bl = bladder; ut = uterus; IC = Ileococcygeus; PR = puborectalis). On straining, the resting convex shape of the IC becomes flattened, and the genital hiatus reduces in size because of ventral movement of the puborectalis. Adapted from Singh K, Jakab M, Reid WM, Berger LA, Hoyte L. Three-dimensional magnetic resonance imaging assessment of levator ani morphologic features in different grades of prolapse. Am J Obstet Gynecol. Apr 2003;188(4):910–915, with permission.

**Figure 7**
Magnetic resonance images (MRI) in the mid sagittal and coronal planes: these images were obtained at rest (Solid) and squeeze (dotted) and then the images were overlapped to show the movement of various anatomical structures during squeeze. Note the cranial and ventral movements of the anal canal and change in the anorectal angle with squeeze. In the coronal images, note the vertical movement of the anus, and flattening of the levator plate with squeeze. Obtained from author

**Figure 8**
Ultrasound images of the anal canal obtained from the 3D-US volume: cross-sectional (axial) images along the length of anal canal in a nulliparous subject. In this example the anal sphincter complex is shown at every 1 mm distance using I-Slice function of HD-11 (Philips). Marked in the figure are the IAS (black circle) and the EAS (white outer ring) are smooth, uniform and symmetrical. Obtained from author

**Figure 9**
Anal canal pressures along the length of the canal and its relationship with anatomical structures: Anal canal pressure was measured using the station pull through technique. Each bar represents mean+SE from the 17 subjects. Note the baseline pressure and the squeeze pressures at each station. The pressures during squeeze at all stations are significantly higher than at rest (p<0.005). Also note, the location of Internal anal sphincter (IAS), puborectalis (PRM) and external anal sphincter (EAS) along the length of the anal canal. Obtained from author

**Figure 10**
Ultrasound images of the anal canal in the sagittal and axial planes with a water filled bag placed in the anal canal: the sagittal image shows the anal canal along its entire length. Axial images at various locations along the length of anal canal allow visualization of various components of the anal closure mechanism. Axial images at R=rectum, 1=Puborectalis (PRM) & Internal sphincter (IAS), 2 = PRM, IAS, and external anal sphincter (EAS), 3 = IAS & EAS, 4 = EAS only. Obtained from author

**Figure 11**
Pelvic Floor Hiatus Captured from the 3D ultrasound images at rest and during a pelvic floor contraction: Note that with contraction the hiatus becomes smaller and the puborectalis muscle moves towards the pubic symphsis. The anterior motion of the puborectalis muscle compresses, anal canal, vagina and urethra against the back of pubic symphsis, which constitutes the constrictor function of pelvic diaphragm. Obtained from author

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References

1. Fritsch H, Brenner E, Lienemann A, Ludwikowski B. Anal sphincter complex: reinterpreted morphology and its clinical relevance. Dis Colon Rectum. 2002;45(2):188–194. - PubMed
1. Fritsch H, Aigner F, Ludwikowski B, et al. Epithelial and muscular regionalization of the human developing anorectum. Anat Rec (Hoboken) 2007;290(11):1449–1458. - PubMed
1. Dyck PJ, Thomas PK. Autonomic and somatic systems to the anorectum and pelvic floor. 4th ed. Philadelphia PA: Elsvier Saunders; 2005.
1. Rattan S. The internal anal sphincter: regulation of smooth muscle tone and relaxation. Neurogastroenterol Motil. 2005;17 Suppl 1:50–59. - PubMed
1. Goyal RK, Hirano I. The enteric nervous system. N Engl J Med. 1996;334:1106–1115. - PubMed

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Pelvic floor anatomy and applied physiology

Affiliation

Pelvic floor anatomy and applied physiology

Authors

Affiliation

Abstract

Figures

References

Publication types

MeSH terms

Grants and funding

LinkOut - more resources

Full Text Sources

Medical