Pelvic Cavity http://www.smbs.buffalo.edu/ana/newpage45.htm [ Home ] [ Up ] [ Anterior Body Wall ] [ Embryonic Body Cavity ] [ Lunglecture ] [ Mediastinum ] [ Heart ] [ Autonomic NS ] [ Rotation of the Gut/Abdomen ] [ Abdominal-Peritoneal Cavities ] [ Glands ,Lymphoid Organs and Blood Supply ] [ Pelvic Cavity ] [ Posterior body wall ] [ Perineum ] [ Home ] [ Up ] [ Anterior Body Wall ] [ Embryonic Body Cavity ] [ Lunglecture ] [ Mediastinum ] [ Heart ] [ Autonomic NS ] [ Rotation of the Gut/Abdomen ] [ Abdominal-Peritoneal Cavities ] [ Glands ,Lymphoid Organs and Blood Supply ] [ Pelvic Cavity ] [ Posterior body wall ] [ Perineum ] Fall 1999 Moore, pp 332-388 Lecture 19 Dr. C. Dlugos PELVIC CAVITY AND ORGANS Overview: An understanding of the pelvis and the organs contained within it is essential in several medical disciplines such as gynecology, obstetrics, urology and gastroenterology. The functions of the pelvis include protection of the viscera, composition of the girdle by which the lower limb is attached to the axial skeleton, and an attachment site for the external genitalia. This lecture should provide the student with basic information concerning the pelvis, differences in the pelvis within the sexes, and a general knowledge of the anatomy of the pelvic organs in males and females. Objectives 1. to learn the anatomy of the bony pelvis and what regions comprise the false and the true pelvis 2. to be aware of sexual differences in the pelvis 3. to understand the anatomy of the pelvic diaphragm in the male and the female 4. to understand the anatomy of the pelvic organs in the male and the female Pelvis:(Latin for basin), region of transition where the trunk and the lower limbs meet, inferior portion of the trunk, contains pelvic cavity, the inferior portion of the abdominopelvic cavity, below the pelvic brim. 1. The pelvis is divided into two parts (Moore Fig. 3.1. pp332-333): a. the greater pelvis or pelvis major (false pelvis), between iliac fossae, part of the abdominopelvic cavity proper b. the lesser pelvis or pelvis minor (true pelvis), "obstetric pelvis", boundaries 1 of 10 9/12/2013 1:18 PM Pelvic Cavity http://www.smbs.buffalo.edu/ana/newpage45.htm : anterior (pubic symphysis), posterior (sacrum and coccyx) and lateral (bodies of ischia). 2. Separation between the false and the true pelvis is the pelvic brim or inlet readily discernable because of the presence of the linea terminalis or iliopectineal line, an oblique ridge on the internal surface of the ilium which is continued on the pubis. Most of these terms are review from first block. 3. Bony and cartilaginous constituents of the pelvis: (Moore Fig.3.2., p334) a os coxae or hip bones: three bones which fuse at age 16-17, ilium, pubis, and ischium. b. sacrum: five sacral vertebrae fuse together (1) anterior and posterior sacral foramina, meet with anterior and posterior rami of sacral nerves (2) large articulating surface for joining with os coxae c. Ligaments which prevent sacrum from rotating on the sacroiliac joints and demarcate the greater and lesser sciatic foramina (1) sacrotuberous ligament : extends between sacrum and ischial tuberosity (2) sacrospinous ligament: extends between sacrum and ischial spine d. Coccyx: 3-5 fused vertebrae (1) may fuse to sacrum late in life (2) partially closes pelvic outlet and functions as an attachment for muscles which close pelvic diaphragm. 4. Pubic symphysis: fibrocartilage, unites two sides of pubic bones 5 . Acetabulum: head of the femur articulates with os coxae, point at which all three bones comprising the hip bone meet. (Moore, Fig.3.2., 3.3., pp334-335). The false pelvis you have already studied, it lies between the iliac fossa at vertebral levels L5 and S1 and contains the ileum and the sigmoid colon. The true pelvis or pelvis minor is situated between the pelvic inlet and pelvic outlet and contains the pelvic organs such as the urinary bladder, rectum, and reproductive organs. Regions of true pelvis: Superior pelvic aperture (pelvic inlet): oval (female) or heart shaped (male) opening, larger in females than in males, periphery is demarcated by linea terminalis which separates the false from the true pelvis. The linea terminalis has a pubic portion (pectineal line) and an illial portion, (arcuate line). This boundaries of the inlet are; 1) anteriorly the pubic symphysis, 2) laterally, the linea terminalis and 3) posteriorly, the sacrum and the 2 of 10 9/12/2013 1:18 PM Pelvic Cavity http://www.smbs.buffalo.edu/ana/newpage45.htm sacral promotory or the projection on the ventral portion of the sacrum where it is connected to the last lumbar vertebrae. 2. Pelvic cavity: contains rectum, bladder, and reproductive organs. The walls of the pelvic cavity are formed by the pubic symphysis anteriorly, the obturator internus muscle laterally and the piriformis muscle posteriorly. 3. Inferior pelvic aperture (pelvic outlet): bounded anteriorly by pubic symphysis, posteriorly by sacrum and coccyx, and laterally by ischial tuberosities, diamond shaped, partially closed because of coccyx. Pelvic diaphragm comprises this area. Differences in the pelvis between sexes (Moore, Table p336). 1. In the female, the bones are more delicate, the female pelvis is less massive, and the muscular impressions are less marked. 2. In the female, the ilia flare more laterally and the anterior iliac spines are more widely separated causing a widening of the hips with respect to the male. 3. In the female, the superior aperture of the lesser pelvis is wider. 4. In the female, the subpubic angle (angle between the ischiopubic rami) is wider (usually greater than 90°) 5. In the female, the sacrum is shorter, wider, and less curved 6. In the female, the acetabulum is smaller. 7. In the female, the pelvic inlet is round or oval with respect to the heart-shaped pelvic inlet in the male. Pelvic diaphragm: funnel shaped fibromuscular diaphragm comprised of two levator ani and two coccygeus muscles. This diaphragm closes the pelvic outlet posteriorly . It is open anteriorly where the urethra, vagina, and anal canal exit (Moore 3.5, p342-343). Muscles:(Moore, Fig. 3.6. p344-345) 1. Levator ani: broad muscle which forms the hammock-like floor of the pelvis and has several parts: 1. Pubococcygeus muscle:attaches on pubis, coccyx , and anococcygeal ligament (the region where the two halves of pubococcygeus meet behind the rectum), the main portion of the levator ani 2. Puborectalis muscle: lies deep to pubococcygeus and forms a supportive sling around the rectum (Fig. 3.6., p344 and Fig. 3.7., p345). 3. Iliococcygeus muscle: thin muscle which attaches to the obturator fascia, the ischial spine, the coccyx and anococcygeal ligament. e. Innervation of the levator ani: branches of S3,4 supply the pelvic surface 3 of 10 9/12/2013 1:18 PM Pelvic Cavity http://www.smbs.buffalo.edu/ana/newpage45.htm and the perineal nerve (S2,3,4,) supplies its perineal surface. 2. Coccygeus (ischiococcygeus): smaller and less important, dorsal to levator ani, attaches to ischial spine, sacrospinous ligament, and coccyx Innervation:pudendal plexus from 4 and 5 sacral nerves Functions of pelvic diaphragm (levator ani and coccygeus muscles): 1. supports pelvic viscera and closes pelvic outlet a. In particular, a part of the diaphragm, the puborectal sling ( puborectalis muscle ) holds the front portion of the anorectal junction anteriorly. This action takes pressure from the external anal sphincter and supports the vagina and bladder in the female and the bladder, seminal vesicles, and prostate in the male. 2. Resists the inferior thrust of increases in abdominal pressure (ie. coughing, sneezing) for maintaining urinary continence. 3. Raises the pelvic floor and assists in urination and defecation. 4. Supports fetal head during uterine contractions during delivery. Peritoneum: covers the superior portions of the pelvis (Moore, Fig. 3.15, p360, Table 3.5., p388). 1. In males the peritoneum passed from the anterior body wall, superior to the the pubic bone and covers the superior and part of the posterior surface of the urinary bladder and superior tips of the seminal vesicles. It invaginates between the bladder and the rectum as the rectovesicular pouch ,the most inferior extent of the peritoneum in the male. It attaches to the anterior aspect of the rectum. 2. In females, the peritoneum takes the same course except that it forms a shallow pouch between the bladder and the uterus, the vesicouterine pouch and the deeper rectouterine pouch between the rectum and the uterus. In the female, the rectouterine pouch is the most inferior extent of the peritoneum. Fascia of the pelvis: 1. Visceral fascia:covers organs, binds the pelvic viscera to each other and to the parietal fascia 2. Parietal fascia: covers the pelvic surfaces of muscles and lines the pelvic cavity a. superior parietal fascia is thickened at the neck of the urinary bladder to form the pubovesicular ligament (female) and the puboprostatic ligament (male), anchors neck of urinary bladder to the pubis. The pubovesicular ligament in the female, attaches to the vagina as well. (Moore,Fig. 3.16., ,p360-61). 4 of 10 9/12/2013 1:18 PM Pelvic Cavity http://www.smbs.buffalo.edu/ana/newpage45.htm Spaces within the fascia 1. retropubic space: fascial plane between bladder and pubic symphysis which allows for expansion of the bladder and access to the bladder and the prostate without entering the peritoneal cavity. Pelvic organs Bladder (vesica urinaria) (Moore, Fig.3.61., p361). 1. Location: In adults the bladder is located within the pelvis minor in back of the pubic symphysis. In infants, the bladder is located in the abdomen and descends into the pelvis major at about age 6. The bladder does not reside in the pelvis minor until after puberty. 2. Surfaces: superior (supports sigmoid colon and urethra), two inferiolateral (cover levator ani), and posterior surfaces (fundus of the bladder) 3.