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Functional Anatomy of Pelvic Floor

Innervation of the Pelvic Floor Muscles: A Reappraisal for the Levator Ani Nerve.
Wallner C, Maas CP, Dabhoiwala NF, Lamers WH, Deruiter MC
Obstet Gynecol. 2006 Sep;108(3):529-534.

OBJECTIVE: We investigated the clinical anatomy of the levator ani nerve and its topographical relationship with the pudendal nerve. METHODS: Ten female pelves were dissected and a pudendal nerve blockade was simulated. The course of the levator ani nerve and pudendal nerve was described quantitatively. The anatomical data were verified using (immuno-)histochemically stained sections of human fetal pelves. RESULTS: The levator ani nerve approaches the pelvic-floor muscles on their visceral side. Near the ischial spine, the levator ani nerve and the pudendal nerve lie above and below the levator ani muscle, respectively, at a distance of approximately 6 mm from each other. The median distance between the levator ani nerve and the point of entry of the pudendal blockade needle into the levator ani muscle was only 5 mm. CONCLUSION: The levator ani nerve and the pudendal nerve are so close at the level of the ischial spine that a transvaginal "pudendal nerve blockade" would, in all probability, block both nerves simultaneously. The clinical anatomy of the levator ani nerve is such that it is prone to damage during complicated vaginal childbirth and surgical interventions. LEVEL OF EVIDENCE: II-3.

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Estrogen and ghrelin decrease cytoplasmic expression of p27(kip1), a cellular marker of ageing, in the striated anal sphincter and levator muscle of ovariectomized rats.
Rizk DE, Al-Marzouqi AH, Hassan HA, Al-Kedrah SS, Fahim MA
Int Urogynecol J Pelvic Floor Dysfunct. 2006 Aug 10;.

A study was carried out to investigate the effect of estrogen and/or ghrelin on the cellular marker of ageing, p27(kip1), in pelvic floor muscles of ovariectomized rats. Virgin Wistar rats (13 months old) underwent ovariectomy followed (1 month) by 42 daily intraperitoneal 17-beta estradiol (10 mug/kg), ghrelin (2 mug/kg), both hormones, or placebo vehicle (n=6x4 groups). Six more age-matched animals underwent sham surgery without ovariectomy. Cytoplasmic expression of p27(kip1) in the striated urethral and anal sphincters and levator muscle was measured by Western blot analysis in all animals (n=30). p27(kip1) signal intensity significantly increased postovariectomy in all muscles compared to sham animals. In the anal sphincter and levator, signal intensity decreased to sham levels with ghrelin or estrogen and decreased further after estrogen or ghrelin and estrogen/ghrelin administration. Urethral sphincter signal intensity decreased without reaching sham levels after drug administration. Estrogen and/or ghrelin replacement reverses the ovariectomy-induced exacerbation of biochemical cellular ageing in the anal sphincter and levator muscle of middle-aged rats.


Visualization of the endopelvic fascia by transrectal three-dimensional ultrasound.
Reisinger E, Stummvoll W
Int Urogynecol J Pelvic Floor Dysfunct. 2006 Feb;17(2):165-9. Epub 2005 Apr 14.

The aim of our pilot study was to explore the feasibility of visualizing the endopelvic fascia by transrectal three-dimensional (3D) ultrasound. Transrectal 3D ultrasound was performed in 12 nulliparous women and 11 women with a history of vaginal delivery. A 6-10 MHz volume probe was used to examine the suburethral anterior vaginal wall. In all women, an echogenic layer was identified at an average of 3-5 mm from the vaginal surface. This echogenic layer was found to be contiguous to the lateral pelvic sidewall and uninterrupted in 10 of 12 nulliparous women, whereas gaps in this layer were identified in all 11 parous women. We hypothesize that this echogenic layer may represent the suburethral component of the endopelvic fascia. Depending on the number and localization of the interruptions in this echogenic layer, the mechanical support of the pelvic floor seems to be weakened corresponding to a higher incidence of descensus of the anterior vaginal wall, which frequently was associated with urinary incontinence.

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Endogenous sex hormones and cardiovascular disease incidence in men.
Arnlov J, Pencina MJ, Amin S, Nam BH, Benjamin EJ, Murabito JM, Wang TJ, Knapp PE, D'Agostino RB Sr, Bhasin S, Vasan RS
Ann Intern Med. 2006 Aug 1;145(3):176-84.

BACKGROUND: Data suggest that endogenous sex hormones (testosterone, dehydroepiandrosterone sulfate [DHEA-S], and estradiol) influence cardiovascular disease (CVD) risk factors and vascular function. Yet, prospective studies relating sex hormones to CVD incidence in men have yielded inconsistent results. OBJECTIVE: To examine the association of circulating sex hormone levels and CVD risk in men. DESIGN: Prospective cohort study. SETTING: Community-based study in Framingham, Massachusetts. PARTICIPANTS: 2084 middle-aged white men without CVD at baseline. MEASUREMENTS: The authors used multivariable Cox regression to relate baseline levels of testosterone, DHEA-S, and estradiol to the incidence of CVD (coronary, cerebrovascular, or peripheral vascular disease or heart failure) during 10 years of follow-up. RESULTS: During follow-up, 386 men (18.5%) experienced a first CVD event. After adjustment for baseline standard CVD risk factors, higher estradiol level was associated with lower risk for CVD (hazard ratio per SD increment in log estradiol, 0.90 [95% CI, 0.82 to 0.99]; P = 0.035). The authors observed effect modification by age: Higher estradiol levels were associated with lower CVD risk in older (median age >56 years) men (hazard ratio per SD increment, 0.86 [CI, 0.78 to 0.96]; P = 0.005) but not in younger (median age < or =56 years) men (hazard ratio per SD increment, 1.11 [CI, 0.89 to 1.38]; P = 0.36). The association of higher estradiol level with lower CVD incidence remained robust in time-dependent Cox models (updating standard CVD risk factors during follow-up). Serum testosterone and DHEA-S levels were not statistically significantly associated with incident CVD. LIMITATIONS: Sex hormone levels were measured only at baseline, and the findings may not be generalizable to women and nonwhite people. CONCLUSIONS: In the community-based sample, a higher serum estradiol level was associated with lower risk for CVD events in older men. The findings are consistent with the hypothesis that endogenous estrogen has vasculoprotective influences in men.


Pelvic floor: anatomy and function.
Bharucha AE
Neurogastroenterol Motil. 2006 Jul;18(7):507-19.

The pelvic floor is a dome-shaped striated muscular sheet that encloses the bladder, uterus, and rectum, and, together with the anal sphincters, has an important role in regulating storage and evacuation of urine and stool. This article reviews the anatomy, nerve supply, pharmacology, and functions of the anal sphincters and the pelvic floor. The internal and external anal sphincters are primarily responsible for maintaining faecal continence at rest and when continence is threatened, respectively. Defecation is a somato-visceral reflex regulated by dual nerve supply (i.e. somatic and autonomic) to the anorectum. The net effects of sympathetic and cholinergic stimulation are to increase and reduce anal resting pressure, respectively. Faecal incontinence and functional defecatory disorders may result from structural changes and/or functional disturbances in the mechanisms of faecal continence and defecation.

Androgen and menopause.
Somboonporn W
Curr Opin Obstet Gynecol. 2006 Aug;18(4):427-32.

PURPOSE OF REVIEW: Androgen therapy is being increasingly used in the management of postmenopausal women. The most common indication is to improve sexual function. The aim of this review is to evaluate current knowledge pertaining to testosterone and sexual function in postmenopausal women. RECENT FINDINGS: The change of testosterone levels during the menopause transition remains controversial. A correlation of endogenous testosterone levels and sexual function is still inconclusive. A Cochrane Review and recent randomized control trials have, however, consistently demonstrated that short-term testosterone therapy in combination with traditional hormone therapy regimens improves sexual function in postmenopausal women, particularly surgically menopausal women with hypoactive sexual desire disorder. An adverse effect on the lipid profile has been identified which appears to be mostly associated with oral methyltestosterone. Data for other effects of testosterone and long-terms risks are lacking. Testosterone may act in a variety of ways in different tissues. This is, however, an area that requires further investigation. SUMMARY: Testosterone therapy is a promising option for treating women with hypoactive sexual desire disorder after surgical menopause. Two remaining questions need to be answer: who is most likely to benefit from testosterone therapy and what are the long-term health risks?


Dissection bias in subperitoneal pelvic anatomy.
Hockel M, Fritsch H
Am J Obstet Gynecol. 2006 May;194(5):1504; author reply 1505. Epub 2006 Apr 21.

Inhibitory effects of sildenafil on small intestinal motility and myoelectrical activity in dogs.
Xu X, Chen JD
Dig Dis Sci. 2006 Apr;51(4):671-6.

Previous studies have shown that sildenafil inhibits the esophageal motility in both humans and animals. The aim of this study was to investigate the effects of sildenafil on intestinal myoelectrical activity and motility. The study was composed of 2 experiments and performed in 7 healthy female dogs with a duodenal cannula 20 cm beyond pylorus (19-26 kg). The first experiment was designed to study the effects of sildenafil on intestinal myoelectrical activity and it included 2 sessions each consisting of 30-minute baseline, 15-minute posttreatment (placebo or 100 mg sildenafil) and 90 minutes after a liquid meal. Intestinal myoelectrical activity was recorded during the entire experiment period. The second experiment was aimed to investigate the effect of sildenafil on intestinal motility and was performed immediately after a solid meal. Intestinal motility was measured by a manometric catheter inserted into the small intestine via the duodenum cannula for 30 minutes at baseline and 60 minutes after sildenafil. Sildenafil significantly reduced the amplitude but had no effect on the frequency and regularity of the intestinal myoelectrical activity. Sildenafil significantly inhibited postprandial intestinal contractions. Although the frequency of the contractions was not altered, the mean area under the curve was significantly reduced during the first 30 minutes (P < .03) and second 30 minutes after sildenafil (P < .03); the power of intestinal contractile activities was also significantly reduced during the first 30 minutes (P < .0004) and second 30 minutes after sildenafil (P < .0003) in comparison with baseline. In conclusion, sildenafil inhibits the amplitude of both intestinal contractile activity and intestinal slow waves.

Frank H. Netter, M.D. (1906-1991): The artist and his legacy.
Hansen JT
Clin Anat. 2006 May 8;.

The renowned medical illustrator Frank H. Netter, M.D., was born on 25 April 1906 in Brooklyn, NY, and died on 17 September 1991 in New York, NY, at the age of 85. In his professional career, Dr. Netter painted over 4,000 medical illustrations, many of which became the center pieces of over 250 issues of Clinical Symposia and were compiled in the 13 volume set of The CIBA Collection of Medical Illustrations. Two years prior to his death, the Atlas of Human Anatomy was published, considered by many to be Dr. Netter's crowning achievement. The Atlas rapidly became the most widely used atlas of anatomy in American medical schools and currently is published in 16 languages. Netter's impressive career as an illustrator and his unique style and legacy to medical education are summarized briefly in this review. Clin. Anat., 2006. (c) 2006 Wiley-Liss, Inc.

Cadaveric fascia lata.
Moalli PA
Int Urogynecol J Pelvic Floor Dysfunct. 2006 May 6;.


The relationship between anterior and apical compartment support.
Summers A, Winkel LA, Hussain HK, Delancey JO
Am J Obstet Gynecol. 2006 Mar 28;.
OBJECTIVE: The purpose of this study was to determine whether the degree of anterior compartment (bladder) and apical compartment (cervix) prolapse are correlated, and whether 2 anterior compartment elements (urethra and bladder) are related at maximal Valsalva. STUDY DESIGN: Women with a complete spectrum of pelvic support were recruited for a pelvic support study. Dynamic magnetic resonance scans were taken during Valsalva. A convenience sample of 153 women with a mean age of 53.3 +/- 12.5 (SD) years with a uterus in situ was studied. Anterior compartment status was assessed by the most caudal bladder point and the internal urinary meatus. The external cervical os was used to assess the apical compartment. The position of the bladder, urethra, and uterus were determined in 20 nulliparous women to determine their reference locations. The distances of each structure below the reference positions were calculated at maximum Valsalva. RESULTS: Average distances of the bladder base, urethra, and uterus from the reference positions at maximal Valsalva were 4.1 +/- 2.4 cm, 3.1 +/- 1.3 cm, and 4.3 +/- 2.4 cm, respectively. The Pearson correlation coefficient of the relationship between the bladder base and uterine distances was r = 0.73 (r(2) = 0.53). The Pearson correlation coefficient of the bladder distance and urethral distance was r = 0.82 (r(2) = 0.67). CONCLUSION: Half of the observed variation in anterior compartment support may be explained by apical support.


Striated muscle fiber compositions of human male urethral rhabdosphincter and levator ani.
Sumino Y, Sato F, Kumamoto T, Mimata H
J Urol. 2006 Apr;175(4):1417-21.

PURPOSE: We clarified the contractile properties of human male periurethral striated muscle fibers to better understand how the rhabdosphincter and the levator ani maintain urinary continence. MATERIALS AND METHODS: Muscle specimens were obtained from 52 male patients who underwent radical prostatectomy or radical cystectomy. The specimens were frozen in liquid nitrogen. Frozen sections (10 mum thick) were stained with myofibrillar ATPase at different pH values (pH 4.2, 4.6 and 10.6), and evaluated for quantitative parameters and fiber type distribution. Myosin heavy chain analysis was performed using SDS-PAGE. RESULTS: Of all 52 cases 37 provided specimens that could be divided into the 2 major fiber types, type 1 (slow twitch) and type 2 (fast twitch). Although type 1 muscle fibers were predominant in RS and LA muscle groups (RS 69.6 +/- 2.7%, LA 67.0 +/- 2.0%), mean muscle fiber size was significantly smaller in RS (mean area 906 +/- 86 mum(2)) than in LA (mean area 2,967 +/- 170 mum(2)) (p <0.0001). In 11 specimens type 2 muscle fibers could be subdivided into types 2A (fast fatigue resistant) and 2B (fast fatigable). Type 2A fibers were significantly more prevalent than type 2B fibers (p <0.05). Likewise, MHC analysis of these 11 specimens found a significantly higher percentage of fiber type 2A expression products (MHC 2A) than of fiber type 2B expression products (MHC 2X) (p <0.05). CONCLUSIONS: RS and LA contribute to urinary continence mechanism by slow contraction. Moreover, the smaller mean size of muscle fibers in RS suggests more fatigue resistance compared with muscle fibers in LA because small fibers have a shorter diffusion distance for metabolic substrates. These results should help contribute to a more detailed understanding of the function of periurethral striated muscles in the human male.

Perineal groove.
Mullassery D, Turnock R, Kokai G
J Pediatr Surg. 2006 Mar;41(3):e41-3.

We present a case of this uncommon congenital anomaly of the perineum. A 6-month-old baby had a perineal groove excised for cosmetic reasons. The histology showed a strip of squamous epithelium with an intervening area lined by rectal type of mucosa, suggesting an embryological remnant such as urorectal septum.

Going in circles: conserved mechanisms control radial patterning in the urinary and digestive tracts.
Mendelsohn C
J Clin Invest. 2006 Mar;116(3):635-7.

Radial patterning in the urinary tract and gut depends on reciprocal signaling between epithelial cells, which form mucosa, and mesenchyme, which forms smooth muscle and connective tissue. These interactions depend on sonic hedgehog (Shh), which is secreted by epithelial cells and induces expression of bone morphogenetic protein 4 (Bmp4), a signaling molecule required for differentiation of smooth muscle progenitors. Patterning of the specialized mucosa lining the anterior-posterior (A-P) axis may be controlled independently by regionally expressed mesenchymal transcription factors. A study by Airik et al. in this issue of the JCI reveals that T-box 18 (Tbx18), a transcription factor selectively expressed in ureteral mesenchyme, regulates smooth muscle differentiation by maintaining Shh1 responsiveness in mesenchymal progenitors. Deletion of Tbx18 resulted in defective urothelial differentiation at the level of the ureter, suggesting that Tbx18 acts via mesenchyme as an important regulator of A-P patterning in the urinary tract.

Estrogen receptors and human disease.
Deroo BJ, Korach KS
J Clin Invest. 2006 Mar;116(3):561-70.

Estrogens influence many physiological processes in mammals, including but not limited to reproduction, cardiovascular health, bone integrity, cognition, and behavior. Given this widespread role for estrogen in human physiology, it is not surprising that estrogen is also implicated in the development or progression of numerous diseases, which include but are not limited to various types of cancer (breast, ovarian, colorectal, prostate, endometrial), osteoporosis, neurodegenerative diseases, cardiovascular disease, insulin resistance, lupus erythematosus, endometriosis, and obesity. In many of these diseases, estrogen mediates its effects through the estrogen receptor (ER), which serves as the basis for many therapeutic interventions. This Review will describe diseases in which estrogen, through the ER, plays a role in the development or severity of disease.

Visible Korean Human: Its techniques and applications.
Park JS, Chung MS, Hwang SB, Shin BS, Park HS
Clin Anat. 2006 Feb 27;.

Three recent studies have offered an unprecedented view of the human body. The Visible Human Project, the Visible Korean Human (VKH), and the Chinese Visible Human have featured the serial sectioning of whole cadavers, producing cross-sectional images that methodically catalogue gross human anatomy. By volumetric reconstruction, these cross-sectional images can be transformed into three-dimensional (3D) images of anatomic structures. Compiling these 3D images would create an invaluable library for medical education and research. The goal of this report is to promote the expansion of such a library of 3D anatomic images and to help users fully understand and utilize the serially sectioned images. To do this, we will discuss the fundamental techniques and equipment used in the VKH and its preliminary experiments. We will also address new applications of the VKH, including virtual brain surgery, virtual endoscopy, and virtual cardiopulmonary resuscitation via the development of virtual dissection software. Clin. Anat., 2006. (c) 2006 Wiley-Liss, Inc.

Chinese visible human project.
Zhang SX, Heng PA, Liu ZJ
Clin Anat. 2006 Feb 27;.

Research on the digital visible human is of great significance and has considerable application value. The US visible human project created the first digital image dataset of a complete human (one male and one female) in 1995. To promote worldwide application-oriented visible human research, additional visible human datasets, representative of different populations of the world, are needed. The Chinese visible human (CVH) male (created in October 2002) and female (created in February 2003) Project achieved greater integrity of images, better blood vessel identification, and were free of organic disease. The most noteworthy technical advance of the Chinese visible human project (CVHP) was the construction of a low temperature laboratory, which prevented loss of small structures (including teeth, nasal conchae, and articular cartilage) from the milling surface. Thus, better integrity of images was achieved. To date, we have acquired five CVH datasets and volume rendered them for visualization on a PC. 3D reconstruction of some organs and structures has been completed and work to segment a complete dataset is under way. Although there is still a long way to go to make the visible human meet the application-oriented needs in various fields, progress is being made toward acquiring new datasets, performing segmentation, and setting up a platform of computer-assisted medicine. Here, we review the history and highlights of the CVHP and foresee its future development as well. Clin. Anat., 2006. (c) 2006 Wiley-Liss, Inc.

An interactive three-dimensional virtual body structures system for anatomical training over the internet.
Temkin B, Acosta E, Malvankar A, Vaidyanath S
Clin Anat. 2006 Feb 27;.

The Visible Human digital datasets make it possible to develop computer-based anatomical training systems that use virtual anatomical models (virtual body structures-VBS). Medical schools are combining these virtual training systems and classical anatomy teaching methods that use labeled images and cadaver dissection. In this paper we present a customizable web-based three-dimensional anatomy training system, W3D-VBS. W3D-VBS uses National Library of Medicine's (NLM) Visible Human Male datasets to interactively locate, explore, select, extract, highlight, label, and visualize, realistic 2D (using axial, coronal, and sagittal views) and 3D virtual structures. A real-time self-guided virtual tour of the entire body is designed to provide detailed anatomical information about structures, substructures, and proximal structures. The system thus facilitates learning of visuospatial relationships at a level of detail that may not be possible by any other means. The use of volumetric structures allows for repeated real-time virtual dissections, from any angle, at the convenience of the user. Volumetric (3D) virtual dissections are performed by adding, removing, highlighting, and labeling individual structures (and/or entire anatomical systems). The resultant virtual explorations (consisting of anatomical 2D/3D illustrations and animations), with user selected highlighting colors and label positions, can be saved and used for generating lesson plans and evaluation systems. Tracking users' progress using the evaluation system helps customize the curriculum, making W3D-VBS a powerful learning tool. Our plan is to incorporate other Visible Human segmented datasets, especially datasets with higher resolutions, that make it possible to include finer anatomical structures such as nerves and small vessels. Clin. Anat., 2006. (c) 2006 Wiley-Liss, Inc.


Contemporary views on female pelvic anatomy.
Barber MD
Cleve Clin J Med. 2005 Dec;72 Suppl 4:S3-11.

Three-dimensional study of pelvic asymmetry on anatomical specimens and its clinical perspectives.
Boulay C, Tardieu C, Benaim C, Hecquet J, Marty C, Prat-Pradal D, Legaye J, Duval-Beaupere G, Pelissier J
J Anat. 2006 Jan;208(1):21-33.
The aim of this study was to assess pelvic asymmetry (i.e. to determine whether the right iliac bone and the right part of the sacrum are mirror images of the left), both quantitatively and qualitatively, using three-dimensional measurements. Pelvic symmetry was described osteologically using a common reference coordinate system for a large sample of pelvises. Landmarks were established on 12 anatomical specimens with an electromagnetic Fastrak system. Seventy-one paired variables were tested with a paired t-test and a non-parametric test (Wilcoxon). A Pearson correlation matrix between the right and left values of the same variable was applied exclusively to values that were significantly asymmetric in order to calculate a dimensionless asymmetry index, ABGi, for each variable. Fifteen variables were significantly asymmetric and correlated with the right vs. left sides for the following anatomical regions: sacrum, iliac blades, iliac width, acetabulum and the superior lunate surface of the acetabulum. ABGi values above a threshold of +/- 4.8% were considered significantly asymmetric in seven variables of the pelvic area. Total asymmetry involving the right and the left pelvis seems to follow a spiral path in the pelvis; in the upper part, the iliac blades rotate clockwise, and in the lower part, the pubic symphysis rotates anticlockwise. Thus, pelvic asymmetry may be evaluated in clinical examinations by measuring iliac crest orientation.