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URETERS, URINARY BLADDER AND URETHRA LEARNING OBJECTIVES At the end of the lecture the student should be able to Identify ureter, urinary bladder and urethra Identify the course and relations of ureter Identify the parts and relations of urinary bladder Identify the urethra URINARY SYSTEM Consists of – – – – Kidney Ureter Urinary bladder Urethra URETER Thick-walled narrow cylindrical tube which is directly continuous near the lower end of the kidney with the tapering extremity of the renal pelvis Convey the urine from the kidneys to the urinary bladder. 25 to 30 cm. in length Has two parts Abdominal part Pelvic part COURSE OF URETER Completely retroperitoneal begins in the sinus of the kidney by the union of calyces. Renal pelvis (or pelvis of the ureter)– is dilated and emerges through the lower part of the hilum. Runs downward along the medial border of the kidney, tapering to become the ureter proper near the lower end of the kidney Ureter proper descends over the back wall of the abdomen, with a slight medial inclination Enters the pelvic cavity by crossing the commencement of the external iliac vessels. Run posteroinferiorly on the lateral walls of the pelvis and then curve anteriormedially to enter the bladder through the back RELATIONS OF URETER Right ureter lateral to the inferior vena cava. Its pelvic is covered by the second part of the duodenum and the renal vessels. The ureter proper is covered with peritoneum, but four sets of vessels cross in front of it, between it and the peritoneum, namely, – Right colic artery – Testicular or ovarian artery – Ileocolic – Superior mesenteric in the root of the mesentery RELATIONS OF URETER LEFT URETER lateral to the inferior mesenteric vein. Its pelvis is more exposed than that of the right After it escapes from behind the renal vessels, it is covered only by the peritoneum. Ureter proper, as on the right side, is separated at intervals from the peritoneum by vessels – Upper left colic artery – Testicular or ovarian artery – Two or more lower left colic CONSTRICTIONS OF URETER 1.junction of ureter and renal pelvis 2.where ureters cross brim of pelvic inlet 3.during their passage through the wall of the urinary bladder. These are the potential sites of obstruction by ureteric stones URINARY BLADDER Musculo-membranous sac which acts as a reservoir for the urine Its size, position, and relations vary according to the amount of fluid it contains. URINARY BLADDER Empty bladder is in the lesser pelvis Tetrahedral in shape Presents a fundus, a vertex, a superior and an inferior surface. Lie on the pubic bones, separated by retropubic space. URINARY BLADDER When the bladder is moderately full it contains about 0.5 liter Assumes an oval form Exhibits – – – – – postero-superior antero-inferior two lateral surfaces Fundus summit. PARTS OF URINARY BLADDER Apex points towards the superior edge of pubic symphysis when bladder is empty Fundus is opposite the apex, formed by convex posterior wall. Body is the major portion between apex and fundus Fundus and inferolateral surfaces meet inferiorly at the neck RELATIONS OF BLADDER Inferolateral surface – Pubic bones – Levator ani – Obturator internus Superior surface – Peritoneum Fundus In male – Posteriorly by rectovesical septum – Laterally by seminal glands In female – Vagina MALE AND FEMALE BLADDER LAYERS OF URINARY BLADDER 3 layers of unstriped muscular fibers External layer, composed of fibers having for the most part a longitudinal arrangement Middle layer, in which the fibers are arranged, more or less, in a circular manner Internal layer, in which the fibers have a general longitudinal arrangement. DETRUSOR MUSCLE The fibers of the detrusor muscle arise from the posterior surface of the body of the pubis in both sexes (musculi pubovesicales) In male from the adjacent part of the prostate and its capsule At the sides of the bladder the fibers are arranged obliquely and intersect one another. Innervation of detrusor muscle When the bladder is stretched, this signals the parasympathetic nervous system to contract the detrusor muscle. This encourages the bladder to expel urine through the urethra. Ligaments of bladder Bladder is relatively free Held firmly anteriorly by its neck by – – – – lateral ligament of bladder. Tendinous arch of the pelvic fascia Puboprostatic ligament in males Pubovesical ligament In females Posteriorly – Directly upon anterior wall of vagina Internal urethral sphincter Towards the neck of bladder the fibers form the internal urethral sphincter. The muscle is made of smooth muscle Under involuntary control. It is kept tonically contracted by lumbar splanchnic nerves (L1-L2) of the sympathetic nervous system. During micturition it is relaxed via the parasympathetic nervous system. This is the primary muscle for preventing the release of urine. Trigone of bladder Trigone is a smooth triangular region of the internal urinary bladder formed by Two ureteral orifices Internal urethral orifice. Urethra Tube that connects the urinary bladder to the genitals for removal out of the body. In males, Urethra travels through the penis, and carries semen as well as urine. In females, the urethra is shorter and emerges above the vaginal opening. Male urethra Urethra is about 8 inches (20 cm) long and opens at the end of the penis. In men divided into 4 parts, named after the location: – – – – Intramural (preprostatic) part Prostatic urethra Membranous urethra Penile urethra Female urethra Is a narrow membranous canal, about 4 cm. long, extending from the internal to the external urethral orifice. Placed behind the symphysis pubis, embedded in the anterior wall of the vagina Its diameter when undilated is about 6 mm External orifice is situated directly about 2.5 cm in front of the vaginal opening. Internal urethral sphincter located at the bladder's inferior end and the urethra's proximal end at the junction of the urethra with the urinary bladder. It is a continuation of the detrusor muscle made of smooth muscle, therefore it is under involuntary or autonomic control. This is the primary muscle for prohibiting the release of urine External urethral sphincter located at the bladder's distal inferior end in females It is a secondary sphincter to control the flow of urine through the urethra. Unlike the internal sphincter muscle, the external sphincter is made of skeletal muscle, therefore it is under voluntary control of the somatic nervous system. References KLM clinical anatomy Gray’s textbook of anatomy Thank you