Anatomy 30
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Anatomy 30






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Anatomy 30 Anatomy 30 Document Transcript

  • Abdominal & pelvic cavitiesT oday we will discuss the abdominal and the pelvic cavities , well also understand what do we mean by the peritoneal cavity and the retroperitoneal space. Now imagine that we want to open the wall of the abdominal cavity and describe what well find inside, so since we know that the abdominal and the pelvic cavities have more than one wall then we can choose any one of them to start with. So lets choose to open the anterior abdominal wall . Now, what layers do we have to open ? (outside to inside ) 1. Well begin with skin . 2. The superficial fascia. Well find it if we open the skin. Now this superficial fascia in the abdomen is a modified or specialized fascia , because it contains actually two layers : I .The superficial layer or the fascia of Camper. Its a fatty tissue that could be very thick depending on the constitution of the individual, whether he is slim or obese . For example, it could be 8 cm thick in a fat or obese person . 1|Page
  • II . A membranous layer or the fascia of Scarpa .Its deep to the superficial layer and underneath it .So as a summary, the superficial fascia itself has the fascia of Camper;the fatty layer and a membranous layer below it in which we call it thefascia of Scarpa .3. The deep fascia.Well see it if we open the superficial fascia . Its a fascia that covers themuscles .4. The muscles .They are seen after the deep fascia .Now, we learned last time that themuscles of the abdominal walldepend on the location.For example, if you are totallylateral, then you have to openthrough three layers :I. Firstly, the external oblique .II. Secondly, the internal oblique.III. finally, the transversus abdominis .But, If you are in the anterior wall,,Then you have to open through the anterior wall of the rectus sheath,which is composed of the aponeurosis of the external oblique inaddition to a part of the aponeurosis of the internal oblique . Then Illfind a muscle , which is the rectus abdominis.Now, if I open this muscle , Ill find the posterior wall of the sheath ,which is composed of part of the internal oblique and the aponeurosis of 2|Page
  • the transversus abdominis . So you have to differentiate which root doyou choose , do you choose laterally or anteriorly .Now, we have to understand that the supplying vessels and nerves ofthe anterolateral abdominal wall run between the middle layer and theinnermost layer . I mean between the internal oblique and thetransversus abdominis . These vessels as we said last time, include thelower sixth intercostal nerves and vessels in addition to the L1 nervewhich is represented or incorporated in two nerves which are theiliohypogastric nerve and the ilioinguinal nerve . So we do havesupplying vessels and supplying nerves running in the interval betweenthe internal oblique and the transversus abdominis.5. The transversalis fascia .Its a layer of connective tissue. So called because it lies underneath thetransversus abdominis.6. The peritoneum . It can be seen after we open the transversalis fascia. Its a serousmembrane just like the pleura and the serous pericardium. Itscomposed of a thin connective tissue layer in addition to a simplesquamous epithelium . Now this membrane surrounds the wholeabdominal and pelvic cavities . It just like that we have a large balloonand the wall of this balloon is adherent to the wall of the abdominal andpelvic cavities, covering the surfaces of these cavities, whether we aretalking about the diaphragm above, the anterolateral wall and muscles,the posterior wall or even the wall of the pelvis. And this is why we callit parietal peritoneum .The same way as the pleural cavity and itspleural membrane (balloon ) that covers the wall of the chest.The parietal peritoneum in the abdomen and the parietal pleura in thechest are sensitive to the common sensations, like the pain, the touchand the temperature.. So if you open the chest or the abdomen , you willfind that after the level of these cavities there will not be any commonsensations. For example, if we are talking about the level of the internal 3|Page
  • organs, as the lungs which are covered by visceral pleura OR theabdominal organs which are covered by visceral peritoneum ,then weare talking about no sensitivity to the common sensations .Its sensitive only to the autonomic sensations like the stretch. Andthats why you can feel if your stomach is full , or you feel a colicwhenever there is an over distention of the wall of the stomach. But ifyou have a needle and introduce it inside your stomach, then you wontfeel any pain :P . Dont be astonished also, that in some great accidentsor war accidents , whenever the abdomen is opened and the person isstill awake , you can hold the viscera and push them inside , and thisperson will not feel anything.Where he would feel ? He will feel a pain if you touch the parietal peritoneum. Now, we cananesthetize the abdominal wall by introducing a needle into this wallitself and then we inject a lidocaine which is a local anesthetic. By this,the whole area which is injected by the lidocaine, is anesthetized .Andthus if I open the abdominal wall , the patient wont feel anything . Alsoif I go deeper into the viscera, he wont be able to feel anything becauseas we said earlier, the viscera itself with the covering visceralperitoneum are not sensitive to the common sensations .So at the pastbefore the presence of anesthesia , the patients had to afford the painthat used to happen during the cutting of the skin ,muscles and peritoneum .This is a sagittal section of the abdominal cavity,we are looking inside . As you can see we have aposterior wall and an anterior wall . This is theballoon which weve talked about, now any organlies within or inside this balloon is calledintraperitoneal organ.If you follow this peritoneum, you will see that it starts lining theposterior abdominal wall which in this case is called the parietal 4|Page
  • peritoneum, then it leaves the posterior wall and surrounds the smallintestines and here is called the visceral peritoneum , then it comes backto the posterior wall. So this organ which is the small intestine is liningwithin the cavity and its surrounded by a double layers of peritoneumand suspended in the posterior abdominal wall through also layers ofperitoneum .So all the intraperitoneal organs in the abdominal cavity have theseproperties:1. They lie within the abdominal cavity.2.They are surrounded by visceral peritoneum.3. They are suspended and usually from the posterior abdominal wallby a double layer of peritoneum which we now call the mesentery .4. They are actually freely mobile , because any structure that is liedand suspended within a cavity, should be by default a mobile structure .Now, we may have some structures that dont lie within the peritonealcavity and are located behind the peritoneum. As a result they will notbe surrounded completely by the parietal peritoneum because it willcover their anterior surfaces only. So they dont have a mesentry andthey are not mobile. These organs are said to be retroperitoneal organslying within what we call the retroperitoneal space .In the same way , some organs which are located within the pelvis suchas the urinary bladder and the rectum, are surrounded by theperitoneum only in their superior surfaces . They dont have a mesentryand they are not freely mobile . They are called subperitoneal organsand located in the subperitoneal space .*Do you think that the subperitoneal space is continuous with theretroperitoneal space ?Yes its freely continuous with it . So some structures can easily passfrom the retroperitoneal space down to the subperitoneal space . 5|Page
  • *What are the retroperitoneal organs?Most of the organs in the gastrointestinal tract are intraperitoneal ,butwe have a few exceptions of some organs that are retroperitoneal orsubperitoneal. Now when you say GIT you should think not only aboutthe tube , but you should also think about the glands associated withthe tube . So if you were asked what is the GIT? You will say its acontinuous tube extending from the mouth down to the anus and alongthis pathway we have some dilatations withdifferent shapes and directions and thats why wewill talk about the different parts of it .So it includes :1.the oral cavity .2.the pharynx.3. The esophagus .It pierces the diaphragm and ends in the abdomen.Now, this esophagus that penetrates the diaphragm, has a very shortintra-abdominal part , only 1-3 cm . So when we are talking about theorgans in the abdomen , we should also mention the esophagus , itdoesnt end in the thorax , it extends for vey short 1 to 3 cm in theabdomen .4. The stomach.Its a dilatation that comes after the esophagus .5. The small intestines.Its approximately 6 m long .Its divided into three parts (duodenum ,jejunum , ileum ).6. The large intestines.It begins with the cecum plus the appendix , then the colon which hasdifferent parts ( ascending , transverse, descending and sigmoid) . Thenwe end in the rectum and the anal canal . 6|Page
  • Now, associated with this tube , we have two major glands , the liverand the pancreas .All these structures that Id mentioned above are intraperitonealorgans. Except for some organs which areretroperitoneal :1. The duodenum.2. The ascending colon.3. The descending colon.4. PancreasSo as a summary, all the GIT organs are intraperitoneal except theduodenum ,the ascending colon, the descending colon and the pancreas,they are retroperitoneal. One Gland is intraperitoneal which is the liver,and the other one which is the pancreas is retroperitoneal . Finally wehave another intraperitoneal organ , but it doesnt belong to the GIsystem . Its the spleen , it actually belongs to the lymphatic system.*what other organs are retroperitoneal or subperitoneal ?Retroperitoneal: Firstly, the organs that wed mentioned above . I meanthe pancreas, the duodenum , ascending and descending colon. Also thelarge vessels as the aorta, the vena cava and there branches, the urinarysystem which is composed of kidneys and ureters .Subperitoneal : the suprarenal glands ,the end of the GI, I mean therectum and the anal canal, the urinary bladder, the urethra and theinternal reproductive organs in both males and females. Such as, thefallopian tubes , the ovaries , the uterus and the vagina in females . Theprostate , the seminal glands and the vas deferens in males . Done by : Abeer Khassawneh . 7|Page