Anatomy of the Pelvis PDF

Dr.Ghassan Lec.1 Anatomy The Pelvis The pelvis The pelvis is the region of the trunk that lies below the abdomen. Its main functions are: 1. Transmits the weight of the body from the vertebral column to the femur. 2. Contains, supports, and p...

Dr.Ghassan Lec.1 Anatomy The Pelvis The pelvis The pelvis is the region of the trunk that lies below the abdomen. Its main functions are: 1. Transmits the weight of the body from the vertebral column to the femur. 2. Contains, supports, and protects the pelvic viscera. 3. Provides attachment for trunk and lower limb muscles. The bony pelvis is composed of four bones: two hip bones [form the lateral and anterior wall] and sacrum and coccyx [part of vertebral column form the posterior wall]. The two hip bones articulate with each other anteriorly at symphysis pubis and posteriory with the sacrum at sacroiliac joint. The pelvis is divided into two parts by the pelvic brim; above the brim is the false pelvis, and below the brim is the true pelvis. The pelvic brim is formed by: Posterior: sacral promontory [anterior and upper margins of the first sacral vertebra] Anterior: upper surface of symphysis pubis. Lateral: ileopectineal line [line that runs downward and forward around the inner surface of the ilium]. 1 False pelvis: it is part of the abdominal cavity, it supports the abdominal contents. It is bounded by: Posterior: lumbar vertebrae. Anterior: lower part of the anterior abdominal wall Lateral: iliac fossa and the ilicus. True pelvis It has an inlet, an outlet, and cavity. The pelvic inlet is the pelvic brim. The pelvic outlet is bounded: 1. anterior : pubic arch 2. Lateral: ischial tuberiosities. 3. posterior : coccyx The pelvic cavity: it lies between the inlet and the outlet. It is short, curved canal with shallow anterior wall and deep posterior wall. The pelvis has anterior, posterior, lateral, and inferior wall. The anterior wall It is formed by posterior surfaces of the bodies of the pubic bones, pubic rami, and the symphysis pubis. Posterior wall Long and curved wall formed by sacrum, coccyx, and piriformis muscle with their covering of parietal pelvic fascia. 2 Sacrum 1. It consists of five rudimentary vertebrae fused together to form a single wedge – shaped bone with forward concavity. 2. Superior border articulates with fifth lumbar vertebra. 3. Inferior border articulates with the coccyx. 4. Laterally, the sacrum articulates with two iliac bones to form the sacroiliac joint. 5. The anterior and upper margins of the first sacral vertebra bulge forward as the sacral promontory. 6. The vertebral foramina together form the sacral canal. 7. The anterior and posterior surfaces of the sacrum posses on each side four foramina for passage of the anterior and posterior rami of the upper four sacral nerves. 8. On the posterior surface, the lamina of the fifth sacral vertebra fail to meet in the midline, forming the sacral hiatus. 9. On the anterior surface, the mass of bone lateral to the foramina is called the lateral mass. 10.On the anterior surface, there are the median sacral crest [adjacent spinous processes are fused with each other [; and lateral sacral crest [fused transverse processes lateral to the posterior foramina]. 3 Coccyx It is consist of four vertebrae fused together to form small triangular bone, which articulates at its base with the lower end of the sacrum.coccygeal vertebrae consist of bodies only, but the first vertebra has a rudimentary transverse process. Piriformis Origin: arises from e front of the lateral masses of the sacrum and leaves the pelvis to enter the gluteal region by passing laterally through the greater sciatic foramen. It is inserted into the greater trochanter of the femur. Action: lateral rotation of the femur. Nerve supply: sacral plexus. Lateral wall of the pelvis It is formed by:  Part of the hip bone below the pelvic inlet.  Obturator foramen and membrane.  Sacrotuberous and sacrospinous ligaments.  Obturator internus muscle and it's covering fascia. Hip bone Large irregular bone, consists of three bones fused together; the ilium [superior], the ischium [posterior and inferior], and the pubis [anterior and inferior]. The outer surface of the hip has a deep depression, the acetabulum, which articulates with the head of femur. Behind the acetebulum is large notch, the greater sciatic notch, which is separated from the lesser sciatic notch by the spine of the ischium. The sciatic notches are converted into greater and lesser sciatic foramen by the sacrotuberous and sacrospinous ligaments. In the lower part of the hip bone is a large opening, the obturator foramen, which is bounded by parts of the ischium and pubis. It is filled by obturator membrane. The ilium: It is the upper flattened part of the hip bone, has the iliac crest, which runs between the anterior and posterior superior iliac spines. Below these spines are the corresponding anterior and posterior inferior iliac spines. The iliopectineal line runs downward and forward around the inner surface of the ilium. The ischium: is the posterior part of the hip and has an ischial spine and tuberosity. The pubis: is the anterior part of the hip bone and have a body and superior and inferior pubic rami. The body of the pubis ha a pubic crest [upper border of the body which ends laterally as the pubic tubercle]. In the lower part of the hip is a large opening, the obturator foramen which is bounded by parts of the ischium and pubis. It is filled by the obturator membrane. Sacrotuberous ligament: strong ligament extends from lateral part of the scrum and coccyx and the posterior inferior iliac spine to the ischial tuberosity. 4 Sacrospinous ligament: triangular –shaped ligament, attached by its base to the lateral part of the scrum and coccyx and by its apex to the ischial spine. These two ligaments convert the greater and lesser sciatic notches into greater and lesser sciatic foramina. Sex differences of the pelvis 1. False pelvis is shallow in the female and deep in the male. 2. The pelvic inlet is oval in female; and heart shaped in the male [this is because of the indentation produced by the sacral promontory]. 3. The pelvic outlet is larger in the female than in male. 4. The pelvic cavity is roomier in the female than in the male and the distance between the inlet and outlet is much shorter. 5. the sacrum is shorter ,wider ,and flatter in the female than in male 6. Pubic arch is more rounded and wider in the female than in male. Inferior wall or pelvic floor The floor of the pelvis supports the pelvic viscera and is formed by the pelvic diaphragm. The pelvic floor stretches across the pelvis and divides it into the main pelvic cavity above [contains the pelvic viscera] and the perineum below. 5 Pelvic diaphragm The pelvic diaphragm is formed by the levator ani muscles and small coccygeus muscles and their coverings fascia. It is incomplete anteriorly to allow passage of the urethra in males and the urethra and the vagina in females. Levator ani Wide thin sheet muscle and has a linear origin from:  Back of the body of the pubis  Tendinous arch formed by a thickening of the fascia covering the obturator internus  Spine of the ischium. Its fibers pass downward and medially to their insertion as fellow:  Anterior fibers [levator prostate or sphincter vaginae] form sling around the lower end of the prostate or the vagina and inserted into the perineal body [mass of fibrous tissue in front of anal canal].  Intermediate fibers: the puborectalis [forms sling around the junction of the anal canal and rectum] and the pubococcygeus [passes posteriorly to be inserted into small fibrous mass called the anococcygeal body ,which lies between the tip of coccyx and the anal canal].  Posterior fibers: the iliococcygeus, which passes posteriorly to be inserted into coccyx and anococcygeal body. 6 Action: 1. Muscles f the two sides form an efficient muscular sling that support and maintain the pelvic viscera in position. 2. It resists the rise in the intrapelvic pressure during straining. 3. Have sphincter action on the anorectal junction. 4. In the female they serve as sphincter of the vagina. Nerve supply Perineal branch of the fourth sacral nerve and perineal branch of the pudendal nerve. Coccygeus Small triangular muscle arises from the spine of ischium and is inserted into lower end of sacrum and upper part of coccyx. Action: assist the levator ani in supporting the pelvic viscera. Nerve supply: fourth and fifth sacral nerves. Pelvic fascia 1. Parietal fascia: it lays the walls of the pelvis and is named according o the muscle it overlies [levator ani fascia or obturator internus fascia]. It is thick and strong over the obturator internus muscle where it gives attachment for levator ani. 2. Visceral fascia: it is layer of loose connective tissue that covers and supports all pelvic viscera. In certain location the fascia thickens to form the facial ligaments, which commonly extend from the pelvic wall to a viscus and provide it with additional support. In the female the facial ligaments attached to the cervix and vagina and are referred as parametrium. 7 The peritoneum in the pelvic cavity of the males It passes from the anterior abdominal wall to the superior surface of the bladder, then it runs posterior surface of the bladder and over the superior surface of the vas deferens, until it reaches the upper end of the seminal vesicles. Here it sweeps backward to reach the anterior surface of the rectum, forming the rectovesical pouch. Then it covers the upper 2l3 of the rectum and becomes continuous with the peritoneum on the posterior abdominal wall. The peritoneum in the pelvic cavity of the females It passes from the anterior abdominal wall to the superior surface of the bladder.then it passes to the anterior surface of the uterus forming the uterovesical pouch. It covers the anterior surface of the body and fundus of the uterus and the posterior surface of the body, fundus, and cervix of the uterus. Then it covers the posterior wall of the vagina and passes to the front of the rectum to form the rectouterine pouch. Contents of the pelvic cavity Sigmoid colon 1. 25-38 cm long. 2. It begins as a continuation of descending colon in front of pelvic brim. 3. Below, it becomes continuous with the rectum in front of third sacral vertebra. 4. It is attached to the posterior pelvic wall by fan –shaped sigmoid mesocolon. 5. It is usually curves to the right of midline before joining the rectum. 6. relation:  Anterior: urinary bladder [in males]; and uterus and upper part of vagina [in females].  Posterior: Rectum, terminal part of ilium, and the sacrum. 7. Arterial supply: sigmidal branches of the inferior mesenteric artery. 8. Venous drainage: inferior mesenteric vein. 9. Nerve supply: inferior hypogaseric plexus. The rectum 1. 13 cm long. 2. It begins as a continuation of the sigmoid colon anterior to the third sacral vertebra. 3. It passes downward to end [2.5 cm in front of the tip of coccyx] by piercing the pelvic diaphragm and becoming continuous with the anal canal. 4. The lower part of the rectum is dilated to form the rectal ampulla. 5. The peritoneum covers the anterior and lateral surfaces of the upper third, anterior surface of the middle third, and leaving the lower third devoid of peritoneum. 8 6. When it examine from the front, the rectum has slight deviation to the left side but quickly return to its position. this due to that ,the rectum has three curves that are prominent when the rectum is distended.the upper and lower curves convex to the right and the middle curve convex to the left ,the result being that the middle part appears to bulge to the left. 7. When examine from lateral side, the rectum follows the anterior concavity of the sacrum before bending downward and backward at its junction with the anal canal. 8. the muscular oat of the rectum is arranged in the usual outer longitudinal and inner circular layers of smooth muscles.the taenia coli of the sigmoid colon ,come together so the longitudinal fibers form a broad band on the anterior and posterior surfaces of the rectum. 9 9. puborectalis portion of the levator ani form sling at the junction of the rectum with anal canal. 10.relation:  posterior [in male and female]: sacrum ,coccyx ,piriformis,coccygeus ,levator ani ,sacral plexus ,sympathetic trunk ,median sacral artery ,and the superior rectal artery.  Anterior [in male]: the upper two third is related to the sigmoid colon and coils of the ileum that occupy the recto-vesical pouch. The lower third is related to the posterior surface of the bladder, vas deferens, seminal vesicles, and the prostate.  Anterior [in female]: the upper two third is related to the sigmoid colon and coils of the ileum that occupy the recto-uterine pouch. The lower third is related to the posterior surface of vagina.  Lateral: the peritoneum [superior] and the fascia cover the levator ani and coccygeus [inferior]. 11.blood supply:  Superior rectal artery: it is branch of inferior mesenteric artery and is the chief artery supplying the mucous membrane of the rectum. It enters the pelvis by passing downward in the root of sigmoid mesocolon and at the level of third sacral vetebra ,it divides ointo two branches which descend on each side of the rectum they pierce the muscular wall and supply the whole thickness of the rectum include the mucous membrane.  Middle rectal artery: it is branch of the internal iliac rtery.it supplies the muscular coat.  Inferior rectal artery: it is a branch of internal pudendal artery. 12. The mucous membrane forms three folds called the transverse folds of the rectum.these folds project into the lumen and are produced by the circular muscle of the wall. Each one is opposite to the concavity of each rectal curve. 13. Lymph drainage The lymph vessels f the rectum drain into pararectal lymph nodes, which are group of nodes surround the rectum.  From upper group to the inferior mesenteric nodes [along the superior rectal artery]  From the middle group to the internal iliac nodes [along the middle rectal artery]. 10   From the lower group to the internal iliac nodes [along the internal pudendal artery]. 14. Nerve supply  Sympathetic supply from the inferior mesenteric plexus.  Parasympathetic supply from pelvis splanchnic nerve.  Pain fibers accompany both sympathetic and parasympathetic nerve.  Sensation of distention is travel by the parasympathetic nerve. Clinical anatomy The Female Pelvis Deformities of the pelvis may be responsible for dystocia (difficult labor). A contracted pelvis may obstruct the normal passage of the fetus. It may be indirectly responsible for dystocia by causing conditions such as malpresentation or malposition of the fetus, premature rupture of the fetal membranes, and uterine inertia.The cause of pelvic deformities may be congenital (rare) or acquired from disease, poor posture, or fractures caused by injury. Pelvic deformities are more common in women who have grown up in a poor environment and are undernourished.In 1933, Caldwell and Moloy classified pelves into four groups: gynecoid, android, anthropoid, and platypelloid The gynecoid Type, present in about 41% of women, is the typical female pelvis, which was previously described. The android Type, present in about 33% of white females and 16% of black females, is the male or funnel-shaped pelvis with a contracted outlet. The anthropoid Type, present in about 24% of white females and 41% of black females, is long, narrow, and oval shaped. The platypelloid Type, present in only about 2% of women, is a wide pelvis flattened at the brim, with the promontory of the sacrum pushed forward 11 Injury to the Pelvic Floor Injury to the pelvic floor during a difficult childbirth can result in the loss of support for the pelvic viscera leading to uterine and vaginal prolapse , herniation of the bladder (cystocele),and alteration in the position of the bladder neck and urethra , leading to stress incontinence. In the latter condition, the patient dribbles urine whenever the intra-abdominal pressure is raised, as in coughing 12