Kidney – Tutorial

Please read Unit 11 – Introduction to Urinary System Tissues prior to completing the activities in this chapter.

Introduction to the Kidneys

The kidneys are important bean-shaped blood cleaning organs located retroperitoneally in the posterior abdominal wall just lateral to either side of the vertebral column at the T₁₂ to L₃ vertebrae level.  An average size adult kidney is approximately 4 inches (10 cm) long and 2.2 inches (5.5 cm) wide.  Blood is supplied to the kidneys by bilateral renal arteries that branch off the abdominal aorta.  Within each kidney are millions of functional units known as nephrons that work to clean metabolic wastes from blood plasma before it is returned to the general circulation via the renal veins to the inferior vena cava.  In the process of removing metabolic wastes from blood the kidneys produce urine which is excreted from the body via the urinary tract.  In addition to removing metabolic wastes from blood, the kidneys also help regulate blood volume, blood pressure, and circulating levels of ions such as Na⁺, K⁺, Cl^–, and H⁺.  The kidneys are also important endocrine organs as they secrete the hormones erythropoietin (EPO), renin, and calcitriol.

The kidneys are usually surrounded by a cushioning layer of fat known as the renal fat pad (perinephric fat).  The entire kidney proper is surrounded by a fibrous capsule of collagen over its entire surface that anchors it to surrounding tissues.  The renal artery, renal vein, and ureter attach at an indentation on the medial border of the kidney known as the hilum (hilar region).  Internally, each kidney is divided into a superficial cortex, and a medulla which lies just deep to the cortex.  The medulla of each kidney is divided into distinct triangular structures known as renal pyramids and at the pointed tip of each renal pyramid is a renal papilla.  Nephrons, the functional units of kidneys that work to clean blood and produce urine, occupy both the cortex and medulla of the kidney.

Urine produced by nephrons is collected by a system of collecting ducts in the renal pyramids and is discharged from the renal papillae into funnel-shaped collecting chambers known as calyces (singular = calyx).  The calyces merge into an even larger centrally located collection region known as the renal pelvis that collects urine from the entire kidney.  The renal pelvis then transports urine into the ureter within the hilar region (hilum) of each kidney.

The tutorials of this chapter will focus primarily on the histological organization of tissue in the cortex and medulla of the kidney.  The tutorials will not cover the specific functions of different segments of a nephron.

Tutorial:  Use the image slider below to learn more about the structure and characteristics of the kidneys. 

Microscopy:  Use the image slider below to learn how to use a microscope to study kidney tissue on a microscope slide.

Tutorial:  Use the hotspot image below to learn more about the gross structure of the kidneys on a low power magnification image.  

Tutorial:  Use the hotspot image below to learn more about the structure of renal corpuscles of the renal (kidney) cortex. 

Tutorial:  Use the hotspot image below to learn more about the characteristics of simple cuboidal epithelium lining collecting ducts in the renal medulla. 

Tutorial:  Use the image slider below to study numerous examples of kidney tissue.