Human Urinary System

 

The kidneys are the principal, urine-forming organs of the urinary system.  Accessory organs include the ureters, urinary bladder, and urethra.  We will study both the gross and microscopic anatomy of the kidneys in great detail. 

 

 

I.          Gross anatomy of the kidneys and nearby structures:

            A.        Kidney - note its retroperitoneal location in the abdominal cavity

 

            B.        Renal hilus - indentation on the central medial surface of kidney

 

            C.        Renal (fibrous) capsule - thin, fibrous covering

 

            D.        Adipose capsule - adipose “padding” lying over the fibrous capsule

 

            E.        Adrenal glands – pyramid-shaped glands that lie on the superior aspect of kidneys

 

 

II.          Frontal (coronal) sections of the kidneys reveal the following:

            A.        Renal cortex -  

 

            B.        Renal medulla -  

 

            C.        Renal pyramids - “triangular” structures in the medulla

 

            D.        Renal papilla - apex of each pyramid

 

            E.        Renal column - cortical tissue separating the pyramids

 

            F.         Renal pelvis - enlarged proximal portion of ureter

 

            G.        Renal calyces (singular = calyx)

                        1.         Major calyces - 2 or 3 direct extensions of the renal pelvis

 

                        2.         Minor calyces - 7 to 13 cup-like extensions of the major calyces that surround the renal papilla

 

III.         The Nephron - the functional urine-forming unit of the kidney

*Note:  In addition to charts and models, study the microscope slides that are set    up to show the structures marked with an *.

 

            *A.       Bowman’s (glomerular) capsule -

 

            *B.       Glomerulus – ball of capillaries (note *capsular space)

 

            *C.       Renal corpuscle - Bowman’s capsule plus the glomerulus

 

            *D.       Proximal convoluted tubule (PCT) - located in the cortex.  Note the simple cuboidal cells with microvilli; the microvilli create a “brush border” appearance.

 

            E.        Loop of Henle – extensions of the proximal convoluted tubules

                        1.         Descending limb -

                        2.         Ascending limb -

 

            *F.       Distal convoluted tubule (DCT) - located in the cortex; note the simple cuboidal epithelium, lack of microvilli, and “cleaner” lumen

 

             G.       Collecting duct - receives renal filtrate from several DCTs

 

             H.       Papillary ducts - terminal ends of the collecting ducts that form the renal papillae; empty urine into the minor calyces

 

             I.         Cortical nephrons - nephrons where the loop of Henle is “short” and extends only slightly or not at all into the renal medulla.  About 80% of all nephrons are of this type.

 

             J.        Juxtamedullary nephrons - nephrons where the loop of Henle extends well into the renal medulla.  About 20% of the nephrons in the kidney are of this type.

 

 

IV.        Blood supply to the nephron:

            A.        Renal artery -

 

            B.        Interlobar artery - passes between the renal pyramids

 

            C.        Arcuate artery – denotes the corticomedullary boundary

 

            D.        Interlobular artery - travels through the renal cortex region

 

            E.        Afferent arteriole -

 

            F.         Glomerulus -

 

            G.        Efferent arteriole -

 

            H.        Peritubular capillaries - surround the portions of the tubules in the cortex

 

            I.          Vasa recta - capillaries that surround the loops of Henle and collecting ducts in the renal medulla

 

            J.         Interlobular vein -

 

            K.        Arcuate vein – denotes the corticomedullary boundary

 

            L.         Interlobar vein -

 

            M.        Renal vein -

 

V.        Urinary bladder and associated structures:

            A.        Urinary bladder

                        1.         Fundus - “dome-like” portion

                        2.         Body - central portion

                        3.         Neck - constricted portion connected to the urethra

                        4.         Trigone - smooth, triangular area within the urinary bladder

                                    a.         Openings to the ureters

                                    b.         Opening to the urethra

                        5.         Rugae -

                        6.         Detrusor muscle - the smooth muscle of the urinary bladder wall

 

            E.        Ureters - view slide showing *transitional epithelium, if available

 

            F.         Urethra and associated structures:

1.         Internal urethral sphincter - smooth muscle sphincter located at the urethral opening where the urethra attaches to the urinary bladder

2.         External urethral sphincter - skeletal muscle that is part of the urogenital diaphragm; located 1-3 cm below the internal urethral sphincter        

                        3.         Urethral orifice -

 

VI.        Additional structures to identify:

            A.        Juxtaglomerular (JG) apparatus - special region of endocrine cells where the DCT contacts the afferent arteriole; involved in regulation of blood pressure through the production of renin

 

B.                 Adrenal gland

 

C.                Urinary bladder histology (cross section; *identify on microscope slides)

a.      *Transitional epithelium lining

b.      *Detrusor muscle – collection of three layers of smooth muscle in the wall

 

Last Updated 12/31/06