Present study were carried out on ten adult males of coot bird, for determinate the histological structure of kidneys. The results were showed that each kidney consisted of three parts, a large cranial (mean of its length 28±0.15mm and its width13±0.08mm),a small caudal (mean of its length 13±0.07mm and its width 4±0.08mm) and a middle part (mean of its length30±0.08mm and its width7.5±0.10mm ) .
Histological results were showed that the kidneys consisted of cortex and medulla, the cortex made up the majority of the kidney and composed of large and small renal corpucles,each renal corpuscle consisted of Bowman’s capsule and glomerulus .The proximal convoluted tubules were lined by simple cuboidal epithelium .The distal convoluted tubules and collecting tubules were lined by simple cuboidal epithelium. The macula densa was situated at vascular pole of glomerulus in close to distal convoluted tubules.
Medulla of kidney was composed of thin and thick segment of henles loop and collecting ducts and these structures were lined by simple cuboidal epithelium. The collecting ducts continued to form the papillary ducts which lined by simple columnar epithelium.
Key words: kidneys, coot bird, nephrons ,glomerulus ,histological.