Advan. Physiol. Edu. 32: 169-170, 2008;
doi:10.1152/advan.00106.2007
1043-4046/08 $8.00
ADV PHYSIOL EDUC 32:169-170, 2008
© 2008 American Physiological Society
ILLUMINATIONS
Modeling the Anatomy and Function of the Pelvic Diaphragm and Perineal Body Using a "String Model"
Satheesha Nayak B.
Melaka Manipal Medical College (Manipal Campus)
Madhav Nagar, Udupi District, Manipal, Karnataka 576104, India
E-mail: nayaksathish{at}yahoo.com
David W. Rodenbaugh
Department of Biosciences
Minnesota State University-Moorhead
Moorhead, MN 56563
Understanding the attachment and function of the pelvic diaphragm and perineal body is important for gynecologists, gastroenterologists, surgeons, and other medical practitioners. The structure and function of the pelvic diaphragm are typically introduced to medical students in anatomy class during the first year of the medical school curriculum. However, it is difficult to facilitate student comprehension of the attachments and structural purpose of the perineal muscles during a cadaver dissection. A simple yet effective and innovative model was used to illustrate the anatomical arrangement of the perineal muscles and help explain the function of the pelvic diaphragm and perineal body. The model is called the "string model" because strings were used in place of the perineal muscles during the demonstration.
The perineal body is a fibromuscular structure/node situated at the center of the perineum. Three paired and three unpaired perineal muscles insert into the perineal body, for a total of nine muscles. These muscles originate from the walls of the pelvis and converge at the perineal body from different angles. The perineal body is pulled in different directions as the nine muscles contract. The net result of these muscle contractions is the movement of the perineal body in an upward, or superior, direction. The perineal body is an important active support component for the pelvic organs. Its normal function is essential for the protection and placement of the pelvic organs. For example, many bodily functions increase intra-abdominal pressure, e.g., sneezing, coughing, laughing, micturition, defecation, and parturition. An increase in intra-abdominal pressure causes the pelvic diaphragm to contract. The pelvic viscera are protected due to the contraction of the pelvic diaphragm and subsequent movement of the pelvic organs in a superior direction. Any defects in the perineal body and/or pelvic diaphragm may result in the prolapse of pelvic organs, especially during periods of increased intra-abdominal pressure. The string model is a practical, cost-effective, supplemental method for demonstrating the dynamic function of these structures to anatomy students examining this static structure during cadaver dissection.
The string model is constructed by tying nine strings together at one end, as shown in Fig. 1. The knot represents the perineal body (Fig. 1, arrow A). Each string is held by an individual student. A pencil box is used to demonstrate how the pelvic organs are supported and moved by the pelvic diaphragm during perineal muscle contraction. While the students hold the strings, a pencil box is placed on top of the knot (Fig. 2). Each student is instructed to pull on the string they are holding. As the nine strings are simultaneously pulled in different directions (representing muscle contraction), the pencil box moves upward. The exercise of pulling the strings is repeated to show how the pelvic viscera (pencil box) moves when the muscles contract.
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Fig. 1. The "string model," which was constructed by tying 9 strings together at one end. The knot (A) represents the perineal body.
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Fig. 2. A pencil box was used in the string model to demonstrate how the pelvic organs are supported and moved by the pelvic diaphragm during perineal muscle contraction. While students hold the strings, a pencil box is placed on top of the knot. As the nine strings are simultaneously pulled in different directions (representing muscle contraction), the pencil box moves upward. The exercise of pulling the strings is repeated to show how the pelvic viscera (pencil box) moves when the muscles contract.
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This model was developed and used in the anatomy class at Melaka Manipal Medical College (Manipal Campus). The anatomy class consisted of 125 medical students. Informal feedback was collected at the end of the session to learn about the usefulness of this demonstration. The students responded positively. Some of the responses were "Superb model," "Very useful," "We understood it," "Keep up the good work," and "Use more such models." Building and demonstrating a variety of models during class makes class livelier and engaging by breaking the monotony of lecture. Importantly, models such as the string model and/or other models are easy to integrate into class without consuming a significant amount of time (1, 2). Finally, an advantage of this model is the fact that the instructor can prepare the model during class right in front of the students. The instructor is both facilitating learning and modeling learning strategies students can use in other classes. Students can begin to learn how everyday items (string) can be used to comprehend dynamic processes such as the function of the pelvic diaphragm.
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REFERENCES
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- Nayak S. The blanket method: a novel method of teaching peritoneal relations of female reproductive organs. Adv Physiol Educ 30: 95–96, 2006.[Free Full Text]
- Nayak SB, Kramer V. The rope method: a novel method of teaching rotation of the midgut. Adv Physiol Educ 31: 238–239, 2007.[Free Full Text]
Copyright © 2008 by the American Physiological Society.
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REFERENCES