HISTOLOGIC FEATURES

• + REGION OF TUBULE

  = PCT (Proximal Convoluted Tubule) * most important

  + FEATURE

  = • Simple cuboidal epithelium

  = • cells are well-stained, with numerous mitochondria, prominent basal folds, and lateral interdigitations

  = • long microvilli, lumens often occluded

  + LOCATION

  = Cortex

  + FUNCTION

  = Major in Reabsorption of all organic nutrients, all proteins, most water, and electrolytes; secretion of organic anions and cations, H+, and NH4
• LOOP OF HENLE

  + REGION OF TUBULE

  = Thin Limbs of Henle

  + FEATURE

  = • simple squamous epithelium

  = • few mitochondria

  + LOCATION

  = Medulla

  + FUNCTION

  = Passive reabsorption of Na+ and Cl
• LOOP OF HENLE

  + REGION OF TUBULE

  = TAL (Thick ascending limbs of Henle)

  + FEATURE

  = • simple cuboidal epithelium

  = • no microvilli, but many mitochondria

  + LOCATION

  = Medulla and medulla rays

  + FUNCTION

  = Active reabsorption of various electrolytes
• LOOP OF HENLE

  + REGION OF TUBULE

  = DCT (Distal Convoluted Tubule)

  + FEATURE

  = • Simple cuboidal epithelium

  = • cells smaller than in PCT

  = • short microvilli and basolateral folds, more empty lumens

  + LOCATION

  = Cortex

  + FUNCTION

  = Reabsorption of electrolytes
• COLLECTING SYSTEM

  + REGION OF TUBULE

  = Principal cells

  + FEATURE

  = • most abundant

  = • cuboidal to columnar

  = • pale-staining

  = • distinct cell membranes

  + LOCATION

  = Medulla rays and medulla

  + FUNCTION

  = Regulated reabsorption of water & electrolytes; regulated secretion of K+
• COLLECTING SYSTEM

  + REGION OF TUBULE

  = Intercalated cells

  + FEATURE

  = • few & scattered

  = • slightly darker staining

  + LOCATION

  = Medulla rays

  + FUNCTION

  = Reabsorption of K+ (low-K+ diet); help maintain acid-base balance