In the following video, we will learn what the kidney looks like microscopically and identify the structures we learned about in previous sections.

Key Definitions:

• Epithelium – The layer of cells that covers all internal and external surfaces of the body, including the renal tubules.
• Podocytes – Specialized cells present in the glomeruli of the kidneys that create the filtration barrier, allowing fluid and small molecules to pass through while keeping larger proteins and cells in the blood.
• Bowman’s Space – The space surrounding the glomerulus that the filtrate initially passes into.
• Bowman’s Capsule – The membrane surrounding Bowman’s space.
• Brush Border – A feature of the cells of the proximal convoluted tubule that creates increased surface area for absorption.
• Lumen – The space inside a structure in the body, for example, the space that contains the filtrate in a renal tubule.

Section summary

Nephrons are microscopic structures which filter blood to eliminate wastes via urine.  Histologically, the cortex of the nephron comprises the glomeruli, Bowmans capsules, PCT, and DCT.  The nephron loops (or Loop of Henle) are at the border of the cortex and medulla and form the renal pyramids. The collecting ducts travel from the cortex, through the medulla, and converge to form the renal papillae at the tip of the pyramids.

Glomeruli are easily recognized by its round structure (full of  many capillaries and RBC), surrounded by a thin membrane (Bowmans capsule), separated by a slight space (Bowmans space). PCTs are recognized by its eosinophilic appearance and ‘fuzzy’ lumen which represents the brush border/microvilli that PCT uses to reabsorb nutrients out of the filtrate.  In contrast, the loop, DCT, and collecting duct structures have a clear lumen.