THE PELVISIn common usage, thepelvisis the part of the trunk that isinferoposterior to the abdomen, and is the area of transition between thetrunk and the lower limbs. Thispelvic cavityis a continuation of theabdominal cavity. Anatomically, the pelvis is the part of the bodysurrounded by the pelvic girdle (bony pelvis), part of the appendicularskeleton of the lower limb (Fig. !").The superior boundary of the pelvic cavity is the pelvic inlet, the superiorpelvic aperture. The pelvis is limited inferiorly by the pelvic outlet, whichis bounded anteriorly by the pubic symphysis (L. symphysis pubis) andposteriorly by the coccy#. The pelvic inlet (superior pelvic aperture) isbounded by the linea terminalis of the pelvis, which is formed by the$Fig. N1 Pelvic girdle.Features of the pelvic girdle demonstratedanatomically (A). The pelvic girdle is formed by the two hip bones (ofthe inferior a#ial skeleton) anteriorly and laterally and the sacrum (ofthe a#ial skeleton) posteriorly.1.PELVIC GIRDLE Thepelvicgirdleisabasin%shapedringof bonesthatconnectsthevertebral column to the two femurs. The primary functions of the pelvicgirdle are to$ &ear the weight of the upper body when sitting and standing. Transfer that weight fromthea#ial tothelower appendicularskeleton for standing and walking. 'rovideattachmentforthepowerful musclesof locomotionandposture and those of the abdominal wall, withstanding the forcesgenerated by their actions.(onse)uently, the pelvic girdle is strong and rigid, especially comparedto the pectoral (shoulder) girdle. *ther functions of the pelvic girdle areto$ (ontain and protect the pelvic viscera (inferior parts of the urinarytracts and the internal reproductive organs) and the inferiorabdominal viscera(intestines), whilepermittingpassageoftheirterminal parts (and, in females, a full%term fetus) via the perineum. 'rovide support for the abdominopelvic viscera and gravid(pregnant) uterus. 'rovide attachment for the erectile bodies of the e#ternal genitalia. 'rovideattachmentforthemusclesandmembranesthatassistthefunctionslistedabovebyformingthepelvic+oorand,llinggaps that e#ist in or around it.COP!RISON OF !LE !ND FE!LE "ON# PELVESFig. N$T%&racic a'd a(d&)i'&pelvic cavity. ! a'd ".Thepelvisisthespacewithinthepelvicgirdle, overlappede#ternallybytheabdominal andgluteal (lowerlimb)regionsandtheperineum. Thus, thepelvishasnouni)uee#ternalsurface area.$. THE *IDNE#$.1. POSITION !ND SH!PEThe kidneys are paired retroperitoneal organs that lie lateral to theupper lumbar vertebrae. In the rela#ed, supine position, theirsuperior polesarelevel withthetwelfththoracicvertebra, whiletheir inferior polesarelevel withthethirdlumbar vertebraandabout -.. cm superior to the iliac crest. *n deep inspiration in theerectposition, however, bothkidneysmaydescendnearorevenpast the iliac crest. /sually the right kidney lies " to - cm inferior tothe left kidney because its developmental ascent is blocked by theliver.&othkidneys lieinclosepro#imitytotheabdominal aortaandinferiorvenacava. Thesema0orvesselse#tendbranchestoeachkidney that enter at a notched, medially located area of theparenchyma knownas the hilum.At the levelof the kidneys,theabdominal aorta lies directly anterior to the vertebral column,passing about -.. cm anteromedial to the left kidney.Note:The inferior vena cava lies to the right of the aorta, nearly touchingthe medial aspect of the right kidney. &oth kidneys are rotated sothat their medial surfaces areslightlyanterior, facilitatingtheirconnection to these ma0or vessels. And ,nally, The suprarenalglandsarebilateral glandstypicallyrelatedtothesuperomedialaspects of the kidneys but not attached to them.$.$. F+NCTIONS OF THE *IDNE#Fig. N, P&-iti&' a'd relati&'- &. /id'ey0 Anteriorviews Theovoidkidneysremovee#cesswater, salts, andwastesofprotein metabolism from the blood while returning nutrients andchemicals to the blood.$.,. !NTERIOR REL!TIONS1idneydevelopment occursintheretroperitoneal spaceoneachsideof adorsal mesentery, whichisinitiallyattachedalongthemidline of the posterior body wall. 2uring growth of the liver androtation of the gut, certain portions of the gut fuse to the posteriorbody wall and become secondarily retroperitoneal. Throughout thisprocess, peritoneal re+ections areshiftedfromthemidlineanddistorted in an irregular but predictable pattern. After developmentiscomplete, certainpartsof thekidneyscontact intraperitonealorgans through an intervening layer of peritoneum, whereas otherparts contact primarily or secondarily retroperitoneal organs withoutaninterveninglayer of peritoneum. Thepresenceor absenceofintervening peritoneummay a3ect the spread of infection ormetastatic disease.$.,.1. Le.t *id'eyThe superolateral aspect of the left kidney contacts the spleen.4eparating these organs is the peritoneumthat forms theposterior surface of the perisplenic region of the greaterperitoneal sac. A triangular area on the superomedial aspect ofthe left kidney contacts the stomach. 4eparating these organsis the peritoneum of the lesser sac (omental bursa). The splenicand gastric areas of the anterior renal surface are separated bythe splenorenal ligament, a derivative of the dorsal mesenterythat forms the left boundary ofThe lesser sac. The two layers of the peritoneum that form thesplenorenal ligament enclose the splenic vessels.The perihilarregion of the left kidney contacts the tailof thepancreas, a secondary retroperitoneal organ, withoutintervening peritoneum. This point of contact occurs posteriorto the left e#tremity of the transverse mesocolon.$.,.$.Rig%t*id'ey.The upper two thirds of the right kidney contact the right lobeof theliver. Thesuperior polee#tends abovethecoronaryligament to directly contact the bare area of the liver withoutintervening peritoneum. Inferior to the pole, the kidney iscoveredwithperitoneumthatformstheposteriorwall ofthehepatorenal recess (also known as the 5orison pouch), part ofthe subhepatic space of the greater peritoneal sac.Theperihilarregionof theright kidneydirectlycontactsthesecond (descending) part of the duodenum, which issecondarily retroperitoneal. 5ost of the lower third of the rightkidney is in direct contact with the right colic +e#ure6 however,asmall sectionof theinferior polemay contact thesmallintestine through a layer of inframesocolic peritoneum.Fig N1 Anterior relations of kidneys.$.1. POSTERIOR REL!TIONS The appro#imate upper third of both kidneys contacts thediaphragm. The diaphragm normally separates the kidneysfromthe diaphragmatic part of the parietal pleura. *noccasion, however, a de,ciency in the region of the lateralarcuate ligament or the lumbocostal trigone allows one ofthe kidneys to directly contact the overlying diaphragmaticpleura. Theupperthirdof theleftkidneyliesanteriorto, andisthus protectedby, theeleventhandtwelfthleft ribs. Asmaller portion of the right kidney receives similarprotection in its relationship to right twelfth rib. 7ithregardtothelowertwothirdsof bothkidneys, thelateral aspects rest on the aponeuroses of the transversusabdominis muscles6 the central aspects rest on theFig N2 8evel of 8"9- intervertebral disc)uadratus lumborum muscles6 and the medial aspects reston the psoas muscles.$.2. GROSS STR+CT+RE The renal artery and vein, as well as the urine collecting system,enter and e#it the medialaspect of each kidney at the hilum.This indentedregionleads toaspacious cavitywithineachkidney known as the renal sinus. 7ithin the renal sinus, a matri#of perinephricfatsurroundsbranchesof therenal arteryandvein, aswell asthelargebranchesof theurinarycollectingsystem. The veins are generally the most anterior and thebranches of the collecting systemmost posterior, with thearteries coursing in between. Theentireouter rimof therenal parenchymaconsists of abrownishpinkregionknownastherenal corte#. 2eeptothecorte#, numerous darker%colored renal pyramids, with basesdirectedperipherallyandapices directedcentrally,collectivelyformtherenal medulla. Theapicesoftherenal pyramidsareknown as the renal papillae. Two or more pyramids may fuse attheir papillae6 thustherearemorepyramidsthanpapillaeineach kidney. The areas of corte# overlying the bases of the pyramids,separating them from the outer surface of the kidney, are knownas cortical arches. The areas of corte# pro0ecting betweenpyramids are known as renal (cortical) columns (of &ertin). Theterm:column;referstotheirappearanceonsection6 infact,they are more like walls, which surround and separate thepyramids.,. +RIN!R# "L!DDER The urinary bladder, a hollow viscus with strong muscular walls,is characteri