Urinary System

Question 1

Describe the structure of the kidney.

Answer 1

1. Covered with connective tissue termed the capsule
   
   1. ​Dense irregular connective tissue
   2. Consists of collagen fibers, fibroblasts, and myofibroblasts
2. Hilum is a medially located deep vertical fissure
   
   1. Where ureter, blood vessels, and nerves enter/exit kidney
3. Conducting system consists of calyces and renal pelvis
   
   1. Resemble ureter and bladder in structure
      
      1. Transitional epithelium
      2. Kidney Calyces
         
         1. Receive urine from collecting ducts minor → major → renal pelvis → ureter
4. Kidney substance consists of cortex (external) and medulla (internal)
   
   1. Cortex
      
      1. Convoluted tubules of cortex form the cortical labyrinth
      2. Radial ray formed by straight tubules and collecting ducts are called medullary rays
      3. Projections of the cortex b/t the pyramids of the medulla are called renal columns
   2. Medulla
      
      1. Consists mostly of renal tubules and collecting ducts
      2. Tubules form renal pyramids (8-12 in each kidney)
      3. Outer Medulla
         
         1. Part of the pyramid closest to the cortex
         2. Outer Stripe
            
            1. Mostly thick tubules and collecting ducts
         3. Inner Stripe
            
            1. Both thick and thin tubules of Loop of Henle
         4. Renal Papilla
            
            1. Projects into minor calyx
            2. Tip formed by area cribosa (where collecting ducts empty into minor calyx)

Question 2

Describe the structure of the nephron, connecting tubule, and the collecting duct.

Answer 2

1. Nephron consists of renal corpuscle and renal tubules
   
   1. Renal corpuscle
      
      1. ​Spherical structure (approx. 200 µm in diameter) that functions to filtrate blood
      2. Consists of a glomerulus that is surrounded by Bowman’s capsule
         
         1. Bowman’s capsule consists of two layers
            
            1. Parietal Layer
               
               1. Outer layer that separates the corpuscle from the surrounding tissue
               2. Is formed by simple squamous epithelium
            2. Visceral Layer
               
               1. Inner layer that covers the glomerulus
               2. Is formed by modified epithelial cells called podocytes
                  
                  1. ​​Podocytes form numerous processes that begin from the cell body and cover the surface of the capillaries of the glomerulus
                     
                     1. Large processes = primary processes
                     2. Fine, digit-like processes = secondary processes/pedicels
                        
                        1. ​These completely envelop glomerular capillaries by interdigitating with the pedicels from neighboring processes
                        2. Narrow gaps b/t these are termed filtration slits
                        3. At the base of these glycocalyx of the adjacent cells form a negatively-charged barrier with a diameter about the sized of an albumin molecule called the slit diaphragm
               3. Urinary space is the space b/t parietal and visceral layers of the Bowman’s capsule
                  
                  1. Primary ultrafiltrate goes from here to the proximal convoluted tubule
               4. Vascular pole is the area of the Bowman’s capsule where the blood vessels (arterioles) enter and exit the corpuscle
               5. Urinary pole is the area of the Bowman’s capsule where the proximal convoluted tubule originates
         2. Glomerulus

Question 3

Describe the differences b/t juxtamedullary and cortical nephrons.

Question 4

Describe the components of the juxtaglomerular apparatus and relate the structure of these components to their function.

Question 5

Describe the blood supply within the kidney.

Question 6

Describe the histological structure of all the layers of the ureter, urinary bladder, and male and female urethra.