Pelvis, Pelvic cavity and contents common to both Male and Female Lecturer: Dante Roel Fernandez RT, M.D. Professor Department of Anatomy Fatima College of Medicine
DEFINITION: - The pelvis is the region of the trunk located below the abdomen. - "Pelvis" is loosely used to denote the region where the trunk and lower extremities meet. - The word pelvis means "basin" and is more correctly applied to the skeleton of the region
Pelvis <ul><li>Loosely used to denote the region where the trunk and lower extremities meet. </li></ul><ul><li>Means “Basin” </li></ul>
II. SURFACE LANDMARKS: <ul><li>1. Iliac crest: the most superior border of the hip region. </li></ul>
2. Anterior Superior Iliac Spine (ASIS): <ul><li>anterior end of iliac crest. </li></ul>
3. Posterior Superior Iliac Spine (PSIS): <ul><li>posterior end of the iliac crest. </li></ul>
4. Pubic Tubercle: <ul><li>where the medial end of the inguinal ligament is attached. It is the bony projection at the supero-lateral border of the body of the pubic bone. </li></ul>
5. Symphysis Pubis: <ul><li>lies in between the bodies of the pubic bone. </li></ul>
III. COMPOSITION The pelvis is composed of two hip bones (os coxae or inominate hones), the sacrum and the coccyx. The hip bone is comprised of the ilium, ischium, and pubis. - The hip bones form the lateral and anterior boundaries of the pelvis The 2 hip bones unite anteriorly at the symphysis pubis. The hip bones articulate posteriorly with the sacrum.
IV. DIFFERENCES BETWEEN MALE AND FEMALE PELVIS Male Female 1. Bones Heavier, rougher Lighter, smoother 2. Sacrum Narrow, more curved Broader, less curved 3. Ilium Lesser lateral flair Greater lateral flair 4. Greater Deeper, narrower Smaller, wider sciatic notches 5. Iliac fossae Deeper Shallower
<ul><li>6.Sciatic spines More projecting Less projecting </li></ul><ul><li>7. Ischial tuberosity Inverted Everted </li></ul><ul><li>8. Symphysis pubis Longer Shorter </li></ul><ul><li>9. Subpubic angle Narrower, pointed Wider, more </li></ul><ul><li> rounded </li></ul><ul><li>10. Margins of the More everted Less everted ischiopubic rami </li></ul>
<ul><li>11. Obturator foramen Oval Triangular </li></ul><ul><li>12. Superior aperture More heart shaped More oval shaped </li></ul><ul><li>13. Major pelvis Wider Narrower </li></ul><ul><li>14. Minor pelvis Deeper, narrower Shallower, wider </li></ul><ul><li>15. Capacity of Less More minor pelvis </li></ul>
V. TWO MAIN DIVISIONS OF THE PELVIS - The pelvis is divided into two parts by the pelvic brim or pelvic inlet - The pelvic brim or inlet is formed by: 1. sacral promontory 2. iliopectineal line 3. upper border of the symphysis pubis
<ul><li>Divisions: 1. False/Greater Pelvis Above the pelvic inlet/brim Boundaries: Behind: lumbar vertebrae Lateral: iliac fossa and iliacus muscle Front: lower part of the anterior abdominal wall </li></ul>
2. True/Lesser. pelvis Lies below the pelvic inlet/brim Bounded inferiorly by the pelvic diaphragm Has an inlet, outlet and a cavity A. Pelvic Inlet or Pelvic Brim Boundaries: Posterior — sacral promontory Lateral — iliopectineal lines Anterior — symphysis pubis
B. Pelvic Outlet Boundary: Posterior — coccyx Lateral — ischial tuberosities Anterior — pubic arch C. Pelvic Cavity - Lies between the inlet and the outlet - Short, curved canal, with a shallow anterior wall and a much deeper posterior wall.
VI. COMPOSITION OF THE WALLS OF THE PELVIC WALL - Includes the supporting framework of bones, joints, ligaments, and membranes - The majority of the framework is internally lined with muscles which are covered with fascia. - The bones comprising the framework are the sacrum and the coccyx from behind, the lower half of the hip bones at the sides and in front.
- The joints are the sacro-coccygeal joint, a pair of sacro-iliac joints and the pubic symphysis. - The ligaments include the ligaments of the joints and also the sacrotuberous and sacrospinous ligaments
The membranes are: 1. Perineal Membrane — tills up the greater part of the pubic archway. 2. Obturator Membrane — almost completely closes the obturator foramen except in the anterior-superior aspect where it leaves a gap, called the obturator canal, by which the obturator nerve escape from the pelvis.
Vll. BOUNDARIES OF THE PELVIC CAVITY <ul><li>Anterior Pelvic Wall - the shallowest wall - formed by the posterior surface of the bodies of the pubic bones, pubic rami, and symphysis pubis. </li></ul>
Posterior Pelvic Wall <ul><li>- formed by the sacrum, coccyx, and piriformis muscles and a covering of parietal pelvic fascia. </li></ul>
Lateral Pelvic wall <ul><li>- formed by the parts of the innominate bone below the pelvic inlet, obturator membrane, sacrotuberous and sacrospinous ligaments, and the obturator internus muscle with its fascia. </li></ul>
Inferior Pelvic Wall <ul><li>supports the viscera of the pelvis </li></ul><ul><li>formed by the pelvic diaphragm </li></ul><ul><li>- the pelvic cavity floor divides the pelvis into the main pelvic cavity above and the perineum below. </li></ul>
Vlll. MUSCLES 1. Obturator Internus Origin : Obturator membrane and adjoining parts of the hip bone Insertion : Medial surface of the greater trochanter of the femur. Nerve Supply : Nerve to obturator internus from the sacral plexus Action : Lateral rotator of the femur when standing. Functions as an abductor when the hip joint is flexed.
Obturator Fascia - It is the most definite layer of fascia in the pelvic canal. - It lines the free surface of the obturator internus. - At the margins of the muscles it fuses with the periosteum, except the ff: a. Inferiorly where it joins the edge of the falciform process of the sacrotuberous ligament.
b. At the upper (anterior) edge of the obturator, where it passes over the border of the muscle to join the obturator membrane and to form the floor of the obturator canal which transmits the obturator vessels and nerves. - It gives rise to almost the entire levator ani. - Under the origin of the levator ani, it is located in the sidewall of the ischiorectal fossa, and near the falciform process, it splits to form the Alcock's canal where the pudendal nerve and the internal pudendal artery and vein pass through.
Piriformis 0: Primarily from the 2 nd, 3rd, and 4 th piece of the sacrum, leaves the pelvis via the greater sciatic foramen and enters the gluteal region and runs across the uppermost part of the hack of the hip joint. I: the greater trochanter of the femur. NS: Anterior primary rami of the first and second sacral nerves. A: lateral rotator of the thigh
Pelvic Diaphragm The coccygeus and the levator ani form a muscular sheath called the pelvic diaphragm. Coccygeus 0: ischial spine I: Side of the last piece of the sacrum and the first piece of the coccyx. NS: Lower sacral nerves. A: acts with the levator ani to support the pelvic viscera
Levator Ani 0: Originates from the inner side of the pubis, along a line extending laterally from the inferior margin of the symphysis to the obturator canal, and from the obturator fascia along the arcus tendinous which extends from the pubis to the spine. I: Median raphe behind the anus; the anococcygeal ligament into the tip and aisles of the coccyx and into an aponeurosis that is attached to the anterior sacrococcygeal ligament.
Divisions: Iliococcygeus, pubococcygeus, puborectalis. - Behind the rectum, some of the fiber bundles from the muscles of the two sides interdigitate, while some terminate in the anococcygeal ligament. - Some fiber bundles also interdigitate across the median line in front of' the rectum, and some are inserted into the walls of the rectum
NS: By the branches of the anterior primary rami of the coccygeal and lower sacral nerves (for the pelvic surface) and by the branches of the inferior hemorrhoidal nerve (for the perineal surface). A: together with the coccygeus, forms a muscular support for the pelvic viscera. - constricts the rectum and pulls it forward. - The puborectalis forms a U-shaped sling around the anorectal junction assisting to maintain fecal continence
<ul><li>Assists the abdominal muscles in compressing the abdominal contents; they are called into use in forced expiration, in vomiting, and in defecation. - In the female, this constricts the vagina from side to side; the anterior borders of the two levators act in association with the bulbospongiosus muscles as a "vaginal sphincter". - The whole muscle is important in the mechanism of parturition; supporting the head of the child during the expulsive efforts of the uterus and the abdominal muscles. </li></ul>
IX. PELVIC JOINTS 1. Sacro-iliac joint - very strong synovial joints between the auricular surfaces of the sacrum and the iliac bones - Ligaments: a. anterior sacroiliac b. posterior sacroiliac c. interosseous sacroiliac d. sacrotuberous e. sacrospinous - the sacrospinous and sacrotuberous ligaments prevent rotation movement at the sacroiliac joint - with limited amount of movement - mainly acts to transmit the weight of the body from the vertebral column to the bony pelvis
2. Sacro-coccygeal joint - a cartilaginous joint between the bodies of the last sacral vertebra and the first coccygeal vertebra 3. Symphysis pubis - a cartilaginous joint between the 2 pubic bones - almost with no possible movement
X. PELVIC PERITONEUM The peritoneum extends downwards from the posterior wall of the abdomen over the pelvic brim into the pelvis. As far as the 3rd piece of the sacrum, it covers the dorsal wall as a continuous sheath. except along the root of the medial limb of the pelvic mesocolon where it is reflected off the sacrum as the two layers of that fold. At the third sacral piece, the mesocolon terminates and peritoneum is spread over the front and sides of the rectum and over the dorsal wall of the pelvic cavity on each side of it, forming the floors of the pararectal fossae. As these fossae are traced downwards, they become shallower and gradually covers less and less of the sides of the rectal wall until it reaches the middle third of the rectum which it covers only in front.
<ul><li>At the middle third of the rectum. it covers only the front. - At the junction of the middle and lower thirds of the rectum, the peritoneum leave the rectum and the dorsal wall of the pelvis and curves forwards to the back of the vagina and the roots of the broad ligaments. it extends forwards: - As the upper layer of the broad ligament on both sides. Over the uppermost part of the back of the vagina and the intestinal surface of the uterus </li></ul>
Curving over the fundus of the uterus and the free edge of each broad ligament. it now passes backwards as the lower layer of the ligament and over the lower or vesical surface of the uterus and is then reflected forwards to cover the upper surface of the urinary bladder. When the bladder is empty. the peritoneum forms the paravesical fossae. - As the peritoneum sweeps forwards from the rectum to the vagina it forms the floor of the rectouterine pouch (of Douglas)
- On the vesical surface of the uterus, the peritoneum extends down only to the junction of its body and neck and is then reflected onto the bladder. making the bottom of the utero-vesical pouch - From the bladder, it passes on the anterior wall of the abdomen and the sidewall of the pelvis.
X1. CLINICAL CORRELATION A. Pelvic Measurements in Obstetrics 1. External Pelvic Measurements -The only method to get accurate and factual information about the shape and dimensions of the pelvic cavity is by x-ray pelvimetry.
2.Internal Pelvic Measurements Made by internal examination of the ff: 1. Pubic arch — spread fingers under the pubic arch to examine its shape. 2. Lateral walls — palpate and check if it is concave, straight or converging. 3. Posterior wall — palpate the sacrum and determine if it is straight or curved 4. Ischial tuberosities — distance between the ischial tuberosities may be estimated by using a closed fist.
B. Caldwel and Moloy Classification - based on the diameters of the pelvic inlet 1. Gynecoid (41%) 2. Android (33%) 3. Anthropoid (24%) 4. Platypelloid (2%) C. Fractures of the Pelvis - Usually brought about by direct trauma. - Secondary hemorrhage is common cause of death. - Associated with damage to pelvic viscera. D. Uterine and Vaginal Prolapse - Due to injury to pelvic floor via difficult childbirth.
XII. ORGANS IN THE PELVIS COMMON TO BOTH MALES AND FEMALES 1. Urinary Bladder 2. Sigmoid Colon 3. Rectum
URINARY BLADDER I Hollow with strong muscular walls. - Receives the urine from the kidneys through the ureters, and contains it until the muscular walls contract and expel it through the urethra in the process of micturition. - Lies in the lower anterior part of the pelvis immediately below the peritoneum, amidst the extraperitoneal tissue, whose areolar element is condensed around it to ensheath it.
ADULT URINARY BLADDER - Entirely contained in the pelvic cavity when empty. - When distended. its neck remains stationary as it balloons upwards lifting up the peritoneum and stripping it off the anterior wall of the abdomen CHILD URINARY BLADDER - Even when empty, it is in contact with the abdominal wall for at birth the pelvis is too small. - As the pelvis enlarges. the bladder gradually sinks and a larger part of the bladder is accommodated in the pelvis by the sixth year. - It becomes a wholly pelvic organ shortly after puberty.
RELATIONS Anteriorly — related to the transversalis fascia and pubic hones. Posterior — male: seminal vesicles, vasa deferentia, pelvic colon and rectum Supero-posteriorly — female: uterus SHAPE AND SURFACES - In the adult, the hardened empty bladder has a three-sided pyramid form. - A full adult bladder is spherical or widely ovoid.
- In the infant, the bladder has an oval shape pointed at both end and the ureters enter it posteriorly near its lower end - In the cadaver, it may be found contracted or flaccid and collapsed by the weight of the intestines.
PARTS OF THE URINARY BLADDER - An apex, a base and three surfaces: the superior surface and a pair of infero-lateral surfaces. - The surfaces and the base are triangular in outline, slightly convex and separated by well-defined blunt borders. - The base and the infero-lateral surfaces meet at the neck and is continuous with the urethra.
NECK OF THE ADULT BLADDER - In the male, it is continuous with the prostate which surrounds the first part of the urethra; - it is connected with the pubo-prostatic ligament in front and at the sides and posteriorly it is related to the commencement of the ejaculatory ducts. - In the female, it abruptly narrows to become one with the urethra; in front and at the sides, the pubo-vesical ligaments are attached to it and is related posteriorly to the vagina.
APEX OF THE ADULT BLADDER The anterior angle of the bladder. - It is immediately behind the upper margin of the pubis about an inch from the skin. - It is continuous with strong fibrous cord – the median umbilical ligament which runs upward in the medial line of the back of the anterior abdominal wall to the umbilicus; -the ligament lies in between the transversalis fascia and the peritoneum. - This ligament is the elongated, attenuated urachus, the shrunken cephalic part of the ventral section of the cloaca of the embryo - Its lumen occasionally persists at birth and in the adult the vesical end of the ligament usually contains a narrow cavity which may or may not be continuous with the cavity of the bladder.
SUPERIOR SURFACE: - Covered with peritoneum. - Since the bladder is below the peritoneum, it is the only surface coated by the peritoneum. - The ureters join the bladder at the posterior angles of this surface. - In the male, the pelvic colon and coils of the ileum rest on the upper surface. - In the female, it is related to the overhanging uterus and a loop of the ileum
INFERO-LATERAL SURFACE - Forms the dorsal wall of the retropubic space of Retzius. - Related to the retropubic fat which separates each of them from the pubic bone, the obturator internus and the levator ani; as the bladder fills, it comes into relation with a greater area of the side wall and the pelvis and with the obturator vessels and nerves.
BASE OR POSTERIOR SURFACE - It is separated from the upper surface by a rounded border; the ureters begin to go through the bladder wall at the corners where the borders join the posterior angles of the upper surface. - In the male, the seminal vesicles, and the ampulla of the vas deferens cover it, except the small area in the middle below the upper border which is covered with peritoneum of the rectovesical pouch.
MUCOUS COAT - When the bladder is full it is smooth but it has less elasticity, and is therefore wrinkled when the bladder is empty. - The trigone is a triangular area that occupies most of the inner surface of its posterior wall. - In this trigone, the mucous membrane is smooth even when the bladder is empty, because it is elastic and is tightly bound by areolar tissue to the muscular coat. - It is also thinner than the rest of the mucous coat and allows the blood in the blood vessels to be seen through it.
OPENINGS IN THE BLADDER There are three openings in the bladder. 1. two orifices of the ureters. 2. internal urethral orifice at the commencement of the urethra. - It is a y-shaped slit situated at the lower angle of the trigone. - Between the limbs of the slit, the mucous membrane in the male is bulged forward by the median lobe of the prostate.
VESSELS OF THE URINARY BLADDER A. Arteries 1. Superior vesical branches of the umbilical artery. 2. Inferior vesical branch of the internal iliac artery. B. Veins - Form plexuses which are dense around the neck and around the ends of the ureters. - The plexuses are drained by the inferior vesical veins.
- some of them being interrupted in small glands that lie on the infero-lateral surface. - From the posterior part, some pass to the external glands but most go to the internal iliac nodes. - Vessels from the neck are associated with those from the prostate that run to the sacral and median common iliac nodes. Nerve supply Upper lumbar nerves through the hypogastric plexus (sympathetic). Pelvic splanchnic which arises from the 2nd , 3rd, and 4th sacral nerves (parasympathetic) — for emptying the urinary bladder.
SIGMOID COLON - about 10-15 inches in length, mobile and hanging down in the pelvic cavity in the form of a loop commences at the level of the pelvic brim as the continuation of the descending colon attached to the posterior pelvic wall by the fan-shaped - sigmoid mesocolon - supplied by the sigmoid branches of the inferior mesenteric artery drained by veins corresponding to the arteries with lymph vessels draining to the nodes along the sigmoid arteries and from these nodes, to the inferior mesenteric nodes nerve supply: sympathetic and parasympathetic nerves from the inferior hypogastric plexus
RECTUM - the part of the alimentary canal into which the feces pass from the colon to await discharge from the body by the act of defecation. - around five inches long with a diameter that varies with the bulk of its contents. - the continuation of the pelvic colon at the level of S3 vertebra - becomes continuous to the anal canal at the level of pelvic diaphragm
Flexures of the Rectum - Other than its antero-posterior curves, it has three sideward bends, the upper and lower flexures are concave towards the left, the middle one towards the right - Most obvious when the gut is distended. - Internally the flexures are marked as the three prominent crescenteric shelves known as the horizontal folds of the rectum or Houston's valves. - The folds are produced by an infolding of the mucous and submucous coats and majority of the circular muscle coat. - Three are usually present but the lowest of the three is often absent or small.
Peritoneal Covering of the Rectum Upper third — with peritoneal covering at its front and its sides Middle third — with peritoneal covering in front Lower third — devoid of peritoneum. Embedded in loose fascia below the level of peritoneum. - The only difference in the peritoneal relations in the female is that when the peritoneum leaves the rectum, it passes forwards on the upper part of the back of the vagina and then onwards over the uterus and its sides
General Relations of the Rectum Posteriorly 1. Branches of the superior rectal artery 2. The sacrum and coccyx and anococcygeal body in the middle and the piriformis, coccygeous and levator ani on each side 3. For the side of the upper third of the rectum: loop of the ileum or pelvic colon. 4. The lower 2/3 is related to the fat on the coccygeus and levator ani and to the condensed areolar tissue around the middle rectal artery.
Anteriorly In the males The upper 2/3, being covered with peritoneum, is related to the ileum or pelvic colon. The lower third is separated from the bladder by the seminal vesicles and vas deferens. and is directly related to the sheath of the prostate below the bladder. In the females The upper 2/3, being clothed with peritoneum, is related to the intestines. The lower third is directly related to the middle third of the vagina.