5.0 URINARY SYSTEM: INTRODUCTION
The urinary system (tractus uropoeticus) comprises the
Early in the 5th week the metanephroi or permanent kidneys develops. They start to function, however, in the 11nd week. Throughout the fetal life urine formation occurs.
Two mesodermal primordia of the metanephros are recognized:
5.2 - images: Development/Fetal kidney
The fetal kidneys are subdivided into 10-12 lobes that are visible on their surfaces as elevations separated by grooves. Each lobe comprises a cortex and medulla. Lobation in the cortex disappears during infancy as the nephrons grow but however persists in the medulla.
See: 5.2 POJA-L2308 et al.
(See Embryology for the complete description of the development of the stages of Pronehroi, Mesonephroi and Metanephroi).
5.3 - images: Kidney general/Vascularization/Macroscopy
An adult kidney (ren) is enclosed by a fibrous capsule and embedded in dense adipous connective tissue. An outer cortex forms a non-lobulated cap of renal tissue covering the medullary lobes. Each medullary lobe forms a pyramid with a convex base forming the corticomedullary junction and a papilla as tip that projects into the calyx. Cortical parenchyma interposed between the pyramids are referred as interlobar columns (Bertin).
See: 5.3 POJA-L2287 et al; 5.3 POJA-L5006B.
5.4 - images: Kidney nephron
An uriniferous tubule consists of two embryologically different parts:
5.4.1 - images: Glomerulus
The nephron is involved in filtration at the glomerular level, selective resorption from the filtrate passing along the tubular system and secretion by the tubular cells into the filtrate.
See: 5.4.3 POJA-L2396 et al; 5.4.2 POJA-L2336 et al; 5.4.2. POJA-L2432 et al.
5.4.2 - images: Juxtaglomerular System
5.4.3 - images: Tubular System
5.5 - images: Interstitium/Pelvis
5.6 - images: Ureter
The upper urinary tract is a collective name for the renal calices, renal pelvis and ureter. Transitional epithelium lines renal pelves, ureters, bladder and proximal urethra. The ureter is a thick-walled muscular tube of 25-30 cm long and its peristaltic contractions convey urine from the kidney towards the bladder.
See: 5.6 POJA-L5013 et al; 5.6 POJA-L2421 et al.
5.7 - images: Urine Bladder
The lower urinary tract is formed by the bladder and urethra. The urine bladder is an active reservoir and varies in size, shape, position and relations with neighboring organs. The bladder wall is composed of distinct tissue layers and each layer contributes to the organ-specific functions. The urothelium is believed to form the main barrier and together with the proper lamina also have sensory properties and is also thought to serve as a mechano-sensor. The detrusor muscle layers are needed for bladder emptying and elasticity of the bladder wall allowed for the required expansion during filling. For the sensory-motor control nerves as well as highly developed networks of interstitial cells are present with specific roles in afferent and efferent signaling pathways.
See: 5.7 POJA-L5012 et al; 5.7 POJA-L4468+2425.
The male urethra (up to 20 cm long) and female urethra (ca 4 cm long) extend from an internal orifice in the bladder. Except during the passage of any fluid along it the urethral canal is a mere slit. Small mucous urethral glands open in the urethra.
See: Male Organs 6.5 POJA-L2749 et al; 6.5 POJA-L4248B et al.
5.8 - images: Pathology
Acute tubular necrosis: See: 5.8 POJA-L2312+3878+3879.
Papillary necrosis: See: 5.8 POJA-La0044+L3882+3883+3884.
Pyelonephritis/tubulointerstitial nephritis: See: 5.8 POJA-La0048+L3881+3880.
- kidneys,
- ureters,
- bladder and
- urethra.
Early in the 5th week the metanephroi or permanent kidneys develops. They start to function, however, in the 11nd week. Throughout the fetal life urine formation occurs.
Two mesodermal primordia of the metanephros are recognized:
- (I) The metanephric diverticulum (or ureteric bud), being the primordium of the ureter, renal pelvis, calyces and collecting tubules. It penetrates (II) and induces the formation of a metanephric cap over its expanded end.
- (II) The metanephric mesoderm (or metanepric blastema).
5.2 - images: Development/Fetal kidney
The fetal kidneys are subdivided into 10-12 lobes that are visible on their surfaces as elevations separated by grooves. Each lobe comprises a cortex and medulla. Lobation in the cortex disappears during infancy as the nephrons grow but however persists in the medulla.
See: 5.2 POJA-L2308 et al.
(See Embryology for the complete description of the development of the stages of Pronehroi, Mesonephroi and Metanephroi).
5.3 - images: Kidney general/Vascularization/Macroscopy
An adult kidney (ren) is enclosed by a fibrous capsule and embedded in dense adipous connective tissue. An outer cortex forms a non-lobulated cap of renal tissue covering the medullary lobes. Each medullary lobe forms a pyramid with a convex base forming the corticomedullary junction and a papilla as tip that projects into the calyx. Cortical parenchyma interposed between the pyramids are referred as interlobar columns (Bertin).
See: 5.3 POJA-L2287 et al; 5.3 POJA-L5006B.
5.4 - images: Kidney nephron
An uriniferous tubule consists of two embryologically different parts:
- A nephron derived from the metanephric mesoderm (II). A nephron is a functional unit and consists of a tangle of capillaries (glomerulus) and a tubular system that that ends up into a collecting tubule.
- A collecting tubule derived from the metanephric diverticulum (I).
5.4.1 - images: Glomerulus
The nephron is involved in filtration at the glomerular level, selective resorption from the filtrate passing along the tubular system and secretion by the tubular cells into the filtrate.
See: 5.4.3 POJA-L2396 et al; 5.4.2 POJA-L2336 et al; 5.4.2. POJA-L2432 et al.
5.4.2 - images: Juxtaglomerular System
5.4.3 - images: Tubular System
5.5 - images: Interstitium/Pelvis
5.6 - images: Ureter
The upper urinary tract is a collective name for the renal calices, renal pelvis and ureter. Transitional epithelium lines renal pelves, ureters, bladder and proximal urethra. The ureter is a thick-walled muscular tube of 25-30 cm long and its peristaltic contractions convey urine from the kidney towards the bladder.
See: 5.6 POJA-L5013 et al; 5.6 POJA-L2421 et al.
5.7 - images: Urine Bladder
The lower urinary tract is formed by the bladder and urethra. The urine bladder is an active reservoir and varies in size, shape, position and relations with neighboring organs. The bladder wall is composed of distinct tissue layers and each layer contributes to the organ-specific functions. The urothelium is believed to form the main barrier and together with the proper lamina also have sensory properties and is also thought to serve as a mechano-sensor. The detrusor muscle layers are needed for bladder emptying and elasticity of the bladder wall allowed for the required expansion during filling. For the sensory-motor control nerves as well as highly developed networks of interstitial cells are present with specific roles in afferent and efferent signaling pathways.
See: 5.7 POJA-L5012 et al; 5.7 POJA-L4468+2425.
The male urethra (up to 20 cm long) and female urethra (ca 4 cm long) extend from an internal orifice in the bladder. Except during the passage of any fluid along it the urethral canal is a mere slit. Small mucous urethral glands open in the urethra.
See: Male Organs 6.5 POJA-L2749 et al; 6.5 POJA-L4248B et al.
5.8 - images: Pathology
Acute tubular necrosis: See: 5.8 POJA-L2312+3878+3879.
Papillary necrosis: See: 5.8 POJA-La0044+L3882+3883+3884.
Pyelonephritis/tubulointerstitial nephritis: See: 5.8 POJA-La0048+L3881+3880.
COPYRIGHTS
All rights reserves worldwide for the POJA collection are hold by L.G. Poels and P.H.K. Jap and Radboud University Medical Center (Radboud UMC Nijmegen). No one may modify, copy, distribute, transmit, display, or publish any materials contained in the POJA collection without prior written permission of the authors Poels and Jap or the UMC St Radboud. Any commercial use of the POJA collection is forbidden. POJA images are partly deposited in the Health Education Assets Library (HEAL database) as well as in the MedEdPortal/AAMC database).
All rights reserves worldwide for the POJA collection are hold by L.G. Poels and P.H.K. Jap and Radboud University Medical Center (Radboud UMC Nijmegen). No one may modify, copy, distribute, transmit, display, or publish any materials contained in the POJA collection without prior written permission of the authors Poels and Jap or the UMC St Radboud. Any commercial use of the POJA collection is forbidden. POJA images are partly deposited in the Health Education Assets Library (HEAL database) as well as in the MedEdPortal/AAMC database).