Histo Urinary

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UNILOBAR KIDNEY (hemisected):
contains a medulla and a cortex. Kidney has a thin connective tissue capsule indicated by blue arrows. The hilum is where blood vessels and nerves enter and exit the kidney and where the renal pelvis exits. Renal papilla = RP, black arrows indicate the calyx (C) where urine collects, RS = renal sinus.

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RENAL LOBE:
consists of a medullary pyramid (medulla) and the overlying cortex at its base. The medulla consists of an inner and outer region. Urine formed by the kidney drains through the collecting ducts in the medulla; the ducts open onto the surface of the renal papilla into the calyx (blue arrow). While this is a unilobar kidney of a rodent, the human kidney contain 10 to 12 lobes per kidney. Black arrows indicate the thin connective tissue capsule.

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RENAL LOBULE:
consists of a medullary ray and its associated cortex. The medullary ray forms the center of the lobule and the outer limits of the lobule are the interlobular blood vessels.

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Junction of the cortex and the medulla (M):
The renal artery and renal vein branch to form segmental branches with the renal sinus. The segmental vessels give rise to the lobar vessels, lobar artery (LA) and lobar vein (LV) which supply the lobes of the kidneys. At the junction of the cortex with the medulla (M) (indicated by black line) the lobar branches give rise to the arcuate vessels (AA = arcuate artery) which run across this junction. From the arcuate vessels interlobular branches run into the cortex (small black arrows). MR = medullary ray in the cortex.

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KIDNEY (corticomedullary junction):
An arcuate vein (AV) and arcuate artery (AA) are seen at the junction. Medullary rays (MR) can be seen running up into the cortex. Small black arrows indicate renal corpuscles.

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RENAL CORPUSCLE in renal cortex:
exhibits two poles: (1) vascular pole (VP) where the afferent and efferent arterioles enter and exist and (2) urinary pole (UP) where the glomerular filtrate exits the urinary space of the renal corpuscle to enter the beginning of the proximal convoluted tubule (PCT). DCT = distal convoluted tubules; black arrows indicate the macula densa.

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RENAL CORPUSCLE of renal cortex:
The renal corpuscle consists of a tuft of capillaries, glomerulus (G), and the glomerular capsule (Bowman's capsule). The glomerular capsule consists of a visceral layer (black arrows) which is closely assoicated with the glomerulus and a parietal layer (green arrows). The urinary space (US) is the space between the visceral and parietal layers of the glomerular capsule. The filtrate collects in the urinary space (US) and drains at the urinary pole (UP) into the proximal convoluted tubule (PCT). Blue arrows indicate the peritubular capillary plexus that surrounds the convoluted tubules. Both the vascular pole (VP) and the urinary pole (UP) are present in this micrograph. MD = macula densa.

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RENAL CORPUSCLE in renal cortex:
The renal corpuscle consists of a tuft of capillaries, glomerulus (green arrows), and the glomerular capsule (Bowman's capsule). The glomerular capsule consists of a visceral layer which is closely assoicated with the glomerulus and a parietal layer (small black arrows). The urinary space (US) is the space between the visceral and parietal layers of the glomerular capsule. The filtrate collects in the urinary space (US) and drains at the urinary pole (not shown in this micrograph) into the proximal convoluted tubule (PCT). Black arrowheads indicate the peritubular capillary plexus that surrounds the convoluted tubules. Black arrows indicate the macula densa.

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SCANNING ELECTRON MICROGRAPH OF PODOCYTES COMPLETELY ENCLOSING A GLOMERULAR CAPILLARY.
Arrows = filtration slits between the pedicels of the podocyte.

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ELECTRON MICROGRAPH OF A RENAL CORPUSCLE:
There are 3 cell types present within a glomerulus: endothelial cells of the capillaries, (3), visceral layer of glomerular capsule, podocytes (4), mesangial cells (5). 1 = urinary space; 2 = parietal layer of glomerular capsule.

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FENESTRATED CAPILLARY OF GLOMERULUS (red cells in lumen):
Arrows indicate the fenestrae which lack diaphragms. 1 = primary process of podocyte; 2 = pedicels of podocytes. The fused basal laminae of the endothelial cell and the podocyte is evident.

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FILTRATION BARRIER WITHIN THE RENAL CORPUSCLE:
The filtration barrier is formed by the fenestrated (F) endothelium (E), the filtration slits (FS) between the pedicels (P2), and the glomerular basement membrane (BM) which is the fused basal laminae of the endothelial cell and podocytes. P1= primary processes of podocyte; C = capillary lumen; P = podocyte (visceral layer of glomerular capsule); US = urinary space.

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FILTRATION BARRIER:
Cap = capillary; arrowheads = fenestrae without diaphragms in endothelium; star = glomerular basement membrane; * =pedicels of podocyte; arrows = filtration slits with thin diaphragms; P2 = pedicels of podocytes; P1 = primary process of podocyte; US = urinary space.

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JUXTAGLOMERULAR [JG] APPARATUS:
The JG apparatus consists of the juxtaglomerular cells (large black arrows) in the wall of the afferent arteriole (A), macula densa (not shown) in the distal convoluted tubule (DCT), and Laci cells (extraglomerular mesangial cells). G = glomerulus; PCT = proximal convoluted tubule; US = urinary space; small black arrows =visceral layer of the glomerular capsule (podocytes) and small green arrows indicate the parietal layer of the glomerular capsule.

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RENAL CORTEX:
consists of the cortical labyrinth (CL) and medullary rays (MR). The cortical labyrinth contains renal corpuscles (black arrows), and both proximal and distal convoluted tubules. Medullary rays contain collecting tubules, thick descending limbs of Henle's loops and thick ascending limbs of Henle's loops .

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Cortical Labyrinth:
contains renal corpuscles and proximal convoluted tubules (PCT) and distal convoluted tubules (DCT). Black arrows indicate the macula densa (MD); blue arrow indicates the beginning of the proximal convoluted tubule at the urinary pole (UP).

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CORTICAL LABYRINTH:
PCT = proximal convoluted tubule; DCT = distal convoluted tubule; MD = macula densa; blue arrows indicate the parietal layer of the glomerular capusle; UP = urinary pole; US = urinary space; green arrows indicate the peritubular capillary plexus which surrounds the tubules.

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MEDULLARY RAY:
consists of three types of tubules: (1) collecting ducts (CD), (2) Thick descending limbs of the loops of Henle (TD) and (3) the thick ascending limbs of the loops of Henle (TA). CL = cortical labyrinth which contains the convoluted tubules and the renal corpuscles of the nephron.

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MEDULLARY RAY (black bar):
forms the center of a renal lobule. The medullary ray contains collecting ducts (CD), thick descending limbs of the loops of Henle (TDL) and thick ascending limbs of the loops of Henle (TAL). The thick descending limbs are morphologically very similar to proximal convoluted tubules (PCT) while the thick ascending limbs are morphologically similar to distal convoluted tubules (DCT).

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OUTER MEDULLA OF KIDNEY:
contains collecting ducts (CD), thick ascending limbs of the loops of Henle (AL), thin segments of the loops of Henle, and vasa rectae (VR)

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OUTER MEDULLA OF KIDNEY:
(higher magnification of previous image). CD = collecting duct in which the cell boundaries are obvious (arrows), AL = thick ascending limb of the loop of Henle, T = thin segment of the loop of Henle and VR = vasa recta

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OUTER MEDULLA showing the tubules in longitudinal section:
CD = collecting ducts; AL = thick ascending limb of the loop of Henle; VR = vasa rectae.

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OUTER MEDULLA (higher magnification of previous image):
TAL = thick ascending limbs of Henle's loops; VR = vasa rectae; CD = collecting ducts. The cell boundaries can be seen between the cells in the collecting ducts.

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RENAL PAPILLA:
projects into the calyx. The calyx is lined by transitional epithelium (black arrows). The large collecting ducts of Bellini (green arrows) open into the surface of the renal papilla. In addition to the collecting ducts the inner medulla contains the thin loops of Henle and vasa rectae.

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RENAL PAPILLA:
The large collecting ducts of Bellinin (CD) open onto the surface of the renal papilla. Urine drains from the collecting ducts into the minor calyx.

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TRANSITIONAL EPITHELIUM lines the urinary ducts from the minor calyces to the initial portion of the urethra.The stratified epithelium has dome shaped surface cells (arrows). The lamina propria (LP) is a fibroelastic connective tissue.

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URETER conducts urine from the renal pelvis to the bladder. It has a stellate shaped lumen (L) in transverse section and is lined by transitional epithelium which rests upon a fibroelastic lamina propria (lp). In the upper 2/3 of the ureter the muscularis (M) consists of an inner longitudinal layer of smooth muscle and an outer circular layer of smooth muscle; however, in the lower third, as seen in this micrograph, the muscularis is composed of three layers of smooth muscle: an inner longitudinal layer , a middle circular layer and an outer longitudinal layer. Surrounding the muscular layer is an adventitia (Adv).

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URETER (from lower third):
T = transitional epithelium; CT =connective tissue of the lamina propria; ILM = inner longitudinal layer of smooth muscle; MCM = middle circular layer of smooth muscle; OLM = outer circular layer of smooth muscle; A = adventitia.

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BLADDER:
The bladder is lined by transitional epithelium which is thrown into many folds in the relaxed state. The epithelium rests upon a fibroelastic lamina propria. There are three layers of smooth muscle which are continuous with those of the lower third of the ureter.

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Bladder is lined by transitional epithelium (indicated by black arrows and rests upon a fibroeleastic lamina propria (CT). The mucosa is thrown into folds in the relaxed state. SM = smooth muscle of the muscularis.