LAB 15: urinary & endocrine

• The kidneys function in the elimination of nitrogenous wastes produced during cellular metabolism, and in the elimination of a number of other materials, such as water and salt, that may be present in excess in the extracellular fluids.
• The kidneys also function in the conservation of necessary substances such as proteins and glucose.
• the kidneys are necessary for both excretion and the maintenance of a constant internal environment within the body.
• the kidneys and the reproductive organs are often considered together as the urogenital system because they are located in the same general body region and may share certain passages
• The paired, bean-shaped kidneys are embedded in fat on the dorsal body wall.
• The kidneys are not suspended by a mesentery as are the other abdominal organs and are covered by peritoneum only on the portion next to the abdominal cavity.
• the kidneys are said to be retroperitoneal
• The adrenal glands, which are triangular-shaped endocrine organs, sit on the superior borders of the kidneys.
• A slender ureter, blood vessels, lymphatic vessels and nerves leave each kidney at the hilus
• the indented medial border of the kidney

  hilus
• The ureter conducts urine from the kidney to the urinarybladder.
• The urinary bladder is a pear-shaped, muscular organ that functions in the temporary storage of urine.
• It is attached to the body by a mid-ventral mesentery and to the brim of the pelvic canal by a pair of lateral mesenteries.


  urinary bladder
• The base of the urinary bladder narrows into a duct called the urethra which continues through the pelvic canal to the exterior
• The kidney is surrounded by three layers of tissue:

  • renal capsule
  • middle adipose capsule
  • renal fascia
• renal capsule: a sheet of dense irregular connective tissue next to the kidney surface
• renal fascia, an outer thin layer of dense irregular connective tissue.
• Deep to the cortex is the darker reddish-brown renal medulla, which contains cone-shaped masses called renal pyramids
• The functional unit of the kidney is the nephron and the blood vessels associated with it.
• Each kidney contains about 1 million microscopic nephrons, which are tubular structures that have been modified to perform all phases of urine formation.
• A nephron consists of a renal corpuscle and a renal tubule.
• Most nephrons are located primarily in the renal cortex area (cortical nephrons)
• A renal corpuscle, located in the cortex region consists of: a Bowman’s (glomerular) capsule and a glomerulus
• Bowman’s (glomerular) capsule, a double-walled invaginated sphere that is formed from the enlarged proximal end of the renal tubule
• glomerulus: a tuft of capillary loops enclosed by the Bowman’s capsule.
• The glomerulus differs from other capillary beds in the body in that it is fed by the afferent arteriole and is drained by the efferent arteriole
• The remainder of the nephron, the renal tubule, is composed of a single-layered tube constructed of epithelial cells.
• The coiled proximal convoluted tubule is located near to Bowman’s capsule.
• The tubule straightens and makes a hairpin turn called the loop of Henle (U-shaped loop) that has ascending and descending limbs.
• The loop of Henle of a cortical nephron dips only slightly into the medulla region, whereas the loop of a juxtamedullary nephron extends deep into the medulla.
• The ascending limb of the tubule extends back to the cortex region where it merges into the distal convoluted tubule, which then empties into a collecting duct.
• Each collecting duct receives urine from many nephrons.

  • The collecting ducts run through the renal pyramids, giving them their striped appearance
• The efferent arteriole subdivides into the peritubular capillaries which intertwine and meander around the tubular system.
• The efferent arterioles of juxtamedullary nephrons tend not to break up into peritubular capillaries but instead form bundles of long vessels called the vasa recta that parallel the loops of Henle
• Urine formed by the nephrons drains into collecting ducts, to a renal papilla at the base of a pyramid, into a minor calyx, to a major calyx and into the renal pelvis
• renal pelvis: a funnel-shaped tube continuous with the ureter
• path iof urine:

  glomerulus -> Bowman's capsule -> > PCT + descending limb -> loop of Heule -> ascending limb -> DST -> collecting duct -> urine drains in tubules to base of pyramid -> renal papilla -> minor calyx -> major calyx -> renal pelvis -> ureter -> urinary bladder -> urethra
• Once the large renal artery enters the kidney it eventually divides to form about 1 million tufts of capillaries (glomeruli) within the nephrons of each kidney
• The nephrons are capable of producing a concentrated urine primarily through the processes of glomerular filtration, tubular reabsorption, and tubular secretion
• Formation of urine begins when blood enters the glomerular capillaries where it is under one of the highest capillary pressures in the body