Urinogenital System

• The urinary organs


  • Kidneys
  • Ureters
  • Urinary bladder
  • Urethra
• Kidneys


  Secrete the urine
• Ureters


  Convey urine to the urinary bladder
• Urinary bladder


  Where urine is for a time retained
• Urethra


  Through which urine is discharged from the body
• Kidneys


  • Situated in the posterior part of the abdomen, one on either side of the vertebral column, behind the peritoneum, and surrounded by a mass of fat and loose areolar tissue
  • Upper extremities are on a level with the upper border of the twelfth thoracic vertebra, their lower extremities on a level with the third lumbar
  • Right kidney is usually slightly lower than the left, probably on account of the vicinity of the liver
  • Long axis of each kidney is directed downward and lateralward; the transverse axis backward and lateralward
  • About 11.25 cm. in length, 5 to 7.5 cm. in breadth, and rather more than 2.5 cm. in thickness
  • Left is somewhat longer, and narrower, than the right
  • Weight of the kidney in the adult male varies from 125 to 170 gm., in the adult female from 115 to 155 gm.
• Anterior surface of right kidney

  • A narrow portion at the upper extremity is in relation with the right suprarenal gland
  • A large area just below this lies in the renal impression on the inferior surface of the liver, and a narrow but somewhat variable area near the medial border is in contact with the descending part of the duodenum
  • The lower part of the anterior surface is in contact laterally with the right colic flexure, and medially, as a rule, with the small intestine
• Anterior surface of left kidney

  • A small area along the upper part of the medial border is in relation with the left suprarenal gland, and close to the lateral border is a long strip in contact with the renal impression on the spleen
  • A somewhat quadrilateral field, about the middle of the anterior surface, marks the site of contact with the body of the pancreas, on the deep surface of which are the lienal vessels
  • Above this is a small triangular portion, between the suprarenal and splenic areas, in contact with the postero-inferior surface of the stomach
  • Below the pancreatic area the lateral part is in relation with the left colic flexure, the medial with the small intestine
• Posterior surface of each kidney

  • Imbedded in areolar and fatty tissue and entirely devoid of peritoneal covering
  • Lies upon the diaphragm, the medial and lateral lumbocostal arches, the Psoas major, the Quadratus lumborum, and the tendon of the Transversus abdominis, the subcostal, and one or two of the upper lumbar arteries, and the last thoracic, iliohypogastric, and ilioinguinal nerves
  • Right kidney rests upon the twelfth rib, the left usually on the eleventh and twelfth
• Lateral border of kidney

  • Convex, and is directed toward the postero-lateral wall of the abdomen
  • On the left side it is in contact at its upper part, with the spleen
• Medial border of kidney

  • Concave in the center and convex toward either extremity; it is directed forward and a little downward
  • Its central part presents a deep longitudinal fissure, bounded by prominent overhanging anterior and posterior lips, named the hilum
  • Above the hilum the medial border is in relation with the suprarenal gland; below the hilum, with the ureter
• Superior extremity of kidney

  • Thick and rounded, and is nearer the median line than the lower; it is surmounted by the suprarenal gland, which covers also a small portion of the anterior surface
• Inferior extremity of kidney

  • Smaller and thinner than the superior and farther from the median line
  • Extends to within 5 cm. of the iliac crest
• Structures in the hilum

  • The vein is in front, the artery in the middle, and the ureter behind and directed downward
  • Frequently, branches of both artery and vein are placed behind the ureter
• Fixation of the kidney

  • Kidney and its vessels are imbedded in a mass of fatty tissue, termed the adipose capsule
  • Kidney and the adipose capsule are enclosed in a sheath of fibrous tissue continuous with the subperitoneal fascia, and named the renal fascia
  • Anterior layer of renal fascia is carried medialward in front of the kidney and its vessels, and is continuous over the aorta with the corresponding layer of the opposite side
  • Posterior layer extends medialward behind the kidney and blends with the fascia on the Quadratus lumborum and Psoas major, and through this fascia is attached to the vertebral column
  • Above the suprarenal gland the two layers of the renal fascia fuse, and unite with the fascia of the diaphragm; below they remain separate, and are gradually lost in the subperitoneal fascia of the iliac fossa
  • Kidney is held in position partly through the attachment of the renal fascia and partly by the apposition of the neighboring viscera
• General structure of the kidney

  • Invested by a fibrous tunic, which forms a firm, smooth covering to the organ
  • Beneath this coat a thin, wide-meshed net-work of unstriped muscular fiber forms an incomplete covering to the organ
  • Kidney is dense in texture, but is easily lacerable by mechanical force
  • Hilum expands into a central cavity, the renal sinus, which contains the upper part of the renal pelvis and the calyces, surrounded by some fat in which are imbedded the branches of the renal vessels and nerves
• Renal calyces


  • Cup-shaped tubes, each of which embraces one or more of the renal papillæ
  • They unite to form two or three short tubes, and these in turn join to form a funnel-shaped sac, the renal pelvis
• Renal pelvis


  • Wide above and narrow below where it joins the ureter, is partly outside the renal sinus
• Medullary substance


  • Consists of a series of red-colored striated conical masses, termed the renal pyramids, the bases of which are directed toward the circumference of the kidney, while their apices converge toward the renal sinus, where they form prominent papillæ projecting into the interior of the calyces
• Cortical substance


  • Reddish brown in color and soft and granular in consistence
  • Lies immediately beneath the fibrous tunic, arches over the bases of the pyramids, and dips in between adjacent pyramids toward the renal sinus
  • The parts dipping in between the pyramids are named the renal columns (Bertini), while the portions which connect the renal columns to each other and intervene between the bases of the pyramids and the fibrous tunic are called the cortical arches
• Renal calyces and pelvis


  Form the upper expanded end of the excretory duct of the kidney
• Kidney


  • Composed of an internal medullary and an external cortical substance
• Medullary substance


  Consists of a series of red-colored striated conical masses, termed the renal pyramids
• Cortical substance


  Reddish brown in color and soft and granular in consistence, lies immediately beneath the fibrous tunic, arches over the bases of the pyramids, and dips in between adjacent pyramids toward the renal sinus
• Renal columns


  Parts of the cortical substance dipping in between the pyramids
• Cortical arches


  Portions of the cortical substance which connect the renal columns to each other and intervene between the bases of the pyramids and the fibrous tunic
• Renal tubules


  Commence in the cortical substance, and after pursuing a very circuitous course through the cortical and medullary substances, finally end at the apices of the renal pyramids by open mouths
• Renal corpuscles


  Small rounded masses of a deep red color, varying in size, but of an average of about 0.2 mm. in diameter, composed of a central glomerulus of vessels and a glomerular capsule
• Glomerulus


  A lobulated net-work of convoluted capillary bloodvessels, held together by scanty connective tissue, derived from a small arterial twig (afferent vessel) and resulting in a vein (efferent vessel)
• Glomerular or Bowman's capsule


  Surrounds the glomerulus, consists of a basement membrane lined by a layer of flattened epithelial cells
• Renal tubules


  1. Neck

  2. Proximal convoluted tube

  3. Descending limb of Henle's loop

  4. Loop of Henle

  5. Ascending limb of Henle's loop

  6. Zigzag tubule

  7. Distal convoluted tubule

  8. Junctional tube

  9. Straight or collecting tubes
• Straight or collecting tubes

  Commence in the radiate part of the cortex, receive the curved ends of the distal convoluted tubules, unite at short intervals, and the resulting tubes pass from the bases of the rays into the renal pyramids, converging to join a central tube (duct of Bellini) which finally opens on the summit of one of the papillae
• Renal artery


  • A large branch of the abdominal aorta, divides into four or five branches which at the hilum lie mainly between the renal vein and ureter
• Inferior renal artery


  Occasionally given off from the abdominal aorta at a lower level, supplies the lower portion of the kidney
• Renal arteries


  Form arterial arches or arcades at the bases of the pyramids, break up into interlobular arteries (end-arteries that give off afferent vessels to the glomeruli) and arteriæ rectæ (supply the renal pyramids)
• Efferent vessels


  Arise from each glomerulus, break up into a dense plexus around the adjacent urinary tubes
• False arteriæ rectæ


  Efferent vessels from the glomeruli nearest the medulla that break up into leashes of straight vessels passing down into the medulla
• Renal veins


  Arise from three sources: veins beneath the fibrous tunic, plexuses around the convoluted tubules in the cortex, and plexuses at the apices of the renal pyramids, join to form the renal vein which emerges from the kidney at the hilum and opens into the inferior vena cava
• Nerves of the kidney

  Derived from the renal plexus, accompany the renal artery and its branches, distributed to the bloodvessels and to the cells of the urinary tubules
• The kidneys are bilateral bean-shaped organs, reddish-brown in colour and located in the posterior abdomen