PowerPoint Handout: Lab 1, Musculoskeletal Pelvis, Perineum and Urinary System Review Slide Title Slide Number Slide Title Slide Number Osseous Pelvis: Introduction Slide 2 Deep Pouch Slide 14 Osseous Pelvis: Features Slide 3 Superficial Pouch: Man Slide 15 Pelvic Ligaments and Foramina Slide4 Superficial Pouch: Woman Slide 16 Pelvic Regions Slide 5 Perineal Body Slide 17 Android Versus Gynecoid Pelvis Slide 6 Neurovascular Structures in Superficial Pouch Slide 18 Pelvic Measurements Slide 7 Review: Female Urethra Slide 19 Muscles of Pelvic Cavity Slide 8 Review: Male Urethra Slide 20 Pelvic Floor Muscles Slide 9 Urethral Injury (Goldman Classification Slide 21 Perineum Slide 10 Sacral Plexus Slide 22 Urogenital and Anal Triangles Slide 11 Pudendal Nerve Slide 23 Perineal Membrane: Introduction Slide 12 Spinal, Epidural, and Pudendal Blocks Slide 24 Perineal Membrane: Deep and Superficial Pouches Slide 13 Osseous Pelvis: Introduction The pelvis is the region of the body surrounded by a ring of bones that structurally connects the vertebral column to the lower extremity. The axial skeleton and the appendicular skeleton both contribute bones to the pelvis. • The axial skeleton's contribution to the pelvis is the sacrum and the coccyx. • The appendicular skeleton's contribution to the pelvis is the right and left hip bones (pelvic bones or os coxae), which are joined anteriorly by the fibrocartilaginous pubic symphysis. The mature hip bones are formed by the fusion of three bones. • Ilium • Ischium • Pubis Posterior Anterior Osseous Pelvis: Features Osteology of the pelvis • Anterior superior iliac spine (ASIS) • Anterior inferior iliac spine • Pelvic brim • Sacral promontory • Arcuate line Anterior Inferior Iliac Spine • Sacral ala • Pectineal line • Superior margin pubic symphysis • Ischial spine • Ischial tuberosity Pubic Arch • Ischiopubic ramus • Pubic arch • Pubic tubercle • Acetabulum • Obturator foramen • Pubic symphysis • It is important to note that the pubic tubercles and the anterior superior iliac spines are in the same vertical plane when the pelvis is in its anatomical position, . Ischiopubic Ramus Pelvic Ligaments and Foramina Pelvic ligaments • Obturator membrane • Sacrotuberous ligament • Sacrospinous ligament • Anterior and posterior sacroiliac ligaments Pelvic foramina whose boundaries are formed partially by ligaments • Greater sciatic foramen • Lesser sciatic foramen • Obturator canal Pelvic Regions The pelvic brim divides the abdominopelvic cavity into the abdominal cavity superiorly and the and the pelvic cavity inferiorly. • The abdominal cavity is the space between the diaphragm and the pelvic brim (pelvic inlet). • The pelvic cavity is the space between the pelvic brim (pelvic inlet) and the muscular pelvic floor. The pelvic brim divides the pelvis into two regions. • The greater pelvis (aka: false pelvis) is the space within the pelvis between the level of the iliac crests and the pelvic brim. The space within the greater pelvis is a component of the abdominal cavity. • The lesser pelvis (aka: true pelvis) is the space between the pelvic brim (pelvic inlet) and the pelvic diaphragm (muscular floor of the pelvis). The space within the lesser pelvis is a component of the pelvic cavity. Iliac Crest False pelvis Pelvic Brim (Inlet) True pelvis Android Versus Gynecoid Pelvis An android (male-like) pelvis can be differentiated from a gynecoid Table 1 (female-like) pelvis by comparing the shape of the pelvic inlet, the size and shape of the pelvic outlet, and the subpubic angle (See Table 1). Female Male Pelvic Measurements The size of the lesser pelvis is important in obstetrics because it determines, to a large extent, the capacity for vaginal childbirth. Several measurements, determined radiographically or manually during pelvic examination, are used to assess the size of the lesser pelvis and its suitability for a vaginal delivery. • The interspinous distance is the transverse distance between the ischial spines, which is typically the narrowest diameter of the birth canal. • The transverse diameter is the distance between the inner edges of the ischial tuberosities. • The true (anatomical) conjugate diameter is the distance between the sacral promontory and the most superior point on the pubic symphysis. This distance can only be measured on radiographs. • The obstetrical conjugate diameter is the shortest distance between the sacral promontory and the pubic symphysis. This distance cannot be measured directly during the pelvic examination, but can be estimated by first determining the diagonal conjugate diameter (see below). • The diagonal conjugate diameter is the distance between the sacral promontory (palpated by the middle finger) and the anterior surface of the pubic symphysis' inferior margin. • This distance can be determined during a pelvic examination, which is then used to calculate the obstetrical conjugate. Once the diagonal conjugate is measured, the examiner subtracts 1.5 to 2 cm from the diagonal conjugate measurement. Muscles of Pelvic Cavity Pelvic muscles contribute to the walls and floor of the pelvic cavity. • Lateral walls • Obturator internus muscle: The obturator internus muscle inserts on the internal surface of the obturator membrane and passes through the lesser sciatic foramen to insert on the greater trochanter of the femur. Within the pelvis, the obturator internus muscle is covered in thick fascia called the obturator fascia. • Posterior walls • Piriformis muscle: The proximal attachment of the piriformis muscle is on the anterior aspects of the S2-4 vertebral segments and passes through the greater sciatic foramen to its distal attachment on the greater trochanter of the femur. • Floor • The pelvic floor (pelvic diaphragm) is a funnel--shaped structure composed of the following muscles: levator ani and coccygeus (next slide). Pelvic Diaphragm Pelvic Floor Muscles The following muscles form the funnel-shaped pelvic floor (pelvic https://3d4medic.al/8K6xxapi diaphragm). • Levator ani (consisting of 3 muscles) • Puborectalis muscle • Pubococcygeus muscle • Iliococcygeus muscle: (Note that the iliococcygeus muscle has its origin on the tendinous arch, which is continuous with the obturator fascia.) • Coccygeus (ischiococcygeus) muscle • The coccygeus muscle's superior border is adjacent to the inferior border of the piriformis muscle. • Its origin is on the ischial spine and the pelvic surface of the sacrospinous ligament. • It inserts onto the lateral margin of coccyx and the most inferior portion of sacrum. Perineum The funnel-shaped pelvic floor (diaphragm) forms a physical boundary between the pelvic cavity and the perineum. The perineum is a diamond-shaped region of the body wall inferior to the pelvic diaphragm between the buttocks and thighs. Its borders consist of the following structures. • Anterior: inferior border of pubic symphysis • Anteriolateral margin: ischiopubic ramus • Posteriolateral margin: sacrotuberous ligament • Posterior: tip of coccyx The pelvic floor contains openings for important structures to pass between the pelvic cavity and the perineum. • The urogenital hiatus is an anterior opening in the pelvic floor through which structures pass to enter the in the urogenital triangle of the perineum. Note that different structures pass through this hiatus in males as compared to females rectal hiatus • In males the urethra passes from the lesser pelvis to the (anal aperture) perineum via the urogenital hiatus. • In females the urethra and vagina pass from the lesser pelvis to the perineum via the urogenital hiatus. • The rectal hiatus (anal aperture) is a posterior opening of the pelvic floor through with the anal canal passes to enter the anal triangle region of the perineum. Urogenital and Anal Triangles The diamond-shaped perineum can be further subdivided into two triangular regions (urogenital triangle and anal triangle) by an imaginary line connecting the two ischial tuberosities. Take note that the two triangles are not in the same plane when the pelvis is in anatomical position. • The urogenital triangle is the anterior triangular region of the diamond-shaped perineum • In anatomical position, the urogenital triangle is oriented in a horizontal plane. • The urogenital triangle contains the urethra and external genitalia. • The anal triangle is the posterior triangular region of the diamond-shaped perineum • In anatomical position, the anal triangle is oriented in a plane that is almost vertical. • The anal triangle contains the anal canal, anus, external anal sphincter, inferior rectal nerve (branch of pudendal nerve), and the fat-filled ischioanal fossa. Urogenital Triangle rectal hiatus (anal aperture) Anal Triangle Perineal Membrane: Introduction The perineal membrane is an important fascial layer within the urogenital triangle. • Its attachments are on the ischial tuberosities and the ischiopubic rami. • The posterior margin of the perineal membrane is NOT attached to bone, but is anchored at its midline to the perineal body. • The perineal membrane creates an important boundary that separates the perineum into two spaces. (See next slide for details.) • A deep space (pouch) superior to the perineal membrane • A superficial space (pouch) inferior the perineal membrane Perineal Membrane: Deep and Superficial Pouches Figure 2 The perineal membrane separates the urogenital triangle into two pouches (spaces). • By definition, the deep perineal pouch (space) is the space located between the perineal membrane and the fascia covering the inferior