Anatomy of Renal System (1) PDF

Anatomy of renal System (i) Introduction o Components of Urinary System:  2 Kidneys → major organs where blood filtration takes place.  2 Ureters → passage tubes to transport urine.  Bladder → storage & expulsion of urine.  Urethra → excretion of urine. o Divided into: Upper part...

Anatomy of renal System (i) Introduction o Components of Urinary System:  2 Kidneys → major organs where blood filtration takes place.  2 Ureters → passage tubes to transport urine.  Bladder → storage & expulsion of urine.  Urethra → excretion of urine. o Divided into: Upper part (kidneys & ureters) & Lower part (bladder & urethra). Kidneys o Reddish brown bean-shaped organs. o Located on each side of the VC. o Responsible for:  Excretion of waste products of metabolism (urine).  Maintenance of water & electrolyte balance in the body. o Location:  Posterior abdominal wall → 1o retroperitoneal (developmentally devoid of mesentery).  At vertebral level of: ✓ Left kidney: T12, L1, L2. ✓ Right kidney: L1, L2, L3.  Right Kidney is at lower level than left due to presence of right lobe of liver.  Upper part is protected by 11th & 12th ribs (right kidney is protected by 12th rib only). o Movement: limited (~ 3 cm) in vertical dimension due to presence of fascial covering. o Fascial coverings:  From outside to inside: Pararenal fat → Renal Fascia → Perirenal Fat → Fibrous Capsule. A. Pararenal Fat: ✓ Extraperitoneal fat layer of lumbar region. ✓ Thicker posteriorly & laterally to the kidney. 1  B. Renal Fascia: ✓ Condensed C.T. membrane. ✓ Surrounds kidney, perirenal fat, & suprarenal gland. ✓ Often sends a thin septum. ✓ Separated into anterior & posterior layers: ▪ Posterior layer: extends medially to fuses with psoas major M. fascia → fuses with the lateral aspect of the body of vertebrae. ▪ Anterior layer: passes anterior to the kidney → anterior to abdominal aorta & inferior vena cava → fuses with the opposite side anterior fascia. ▪ Laterally, the two layers fuse together & with the transversalis fascia. ✓ Boundaries: ▪ Laterally: continuous with transversalis fascia. ▪ Medially: blends with adventitia of renal vessels & Psoas fascia. ▪ Superiorly: two layers enclose the kidney → fuse together at the upper pole → split to enclose the suprarenal gland → continuous with diaphragmatic fascia → forms 1o attachment for suprarenal gland (suspensory ligament of suprarenal gland). ▪ Inferiorly:  Extends along the ureter but not attached → limited mobility for kidney.  Clinically → perirenal abscess & nephroptosis. ✓ In perirenal abscess or injured kidney:  The direction of pus or blood is determined by attachments of renal fascia.  Pus or blood will be forced its way into pelvis between anterior & posterior layers of renal fascia. C. Perirenal fat: ✓ Surrounds both kidney & suprarenal gland and separates between them. ✓ It extends into the renal sinus between renal vessels. D. Fibrous capsule: ✓ Dense irregular connective tissue. ✓ Outermost layer of kidney. External Anatomy Of Kidney o Convex lateral border. o Convex medial border → except in its middle (concave) → the renal hilum. o Has upper pole, middle area, & lower pole. 2 o Renal Hilum:  The area where structures enter or leave the kidney (root of kidney).  Transpyloric plane pass through the hilum of left kidney at the level of L1.  The hilum opens into renal sinus.  Structures within hilum (A→P): ✓ Renal vein: ▪ Most anterior. ▪ Left is longer than right. ✓ Renal artery: right is longer than left. ✓ Ureter: most posterior. o Kidney’s relations: A. Right kidney: ✓ Superiorly: ▪ Liver (right lobe). ▪ Suprarenal gland. ✓ Anteriorly: ▪ Right colic flexure. ▪ 2nd part of duodenum. ▪ Right lobe of the liver. ✓ Posteriorly: ▪ Diaphragm. ▪ Psoas major. ▪ Quadratus lumborum. B. Left kidney: ✓ Superiorly: ▪ Spleen. ▪ Suprarenal gland. ✓ Anteriorly: ▪ Pancreas. ▪ Left colic flexure. ✓ Posteriorly: ▪ Diaphragm. ▪ Psoas major. ▪ Quadratus lumborum. 3 Internal Anatomy Of Kidney o In hemisected kidney:  Outer layer (Cortex): divided into 2 zones (cortical zone & juxtamedullary zone).  Inner medulla = renal pyramids (~8-18).  2 projections: 1. Renal columns: extensions of cortex between the pyramids. 2. Medullary rays (radiated area): striated projections from bases of renal pyramids into cortex.  Note: kidney is protected by dense irregular C.T. capsule (Renal Capsule). o Nephron:  Functional unit of the kidney that is responsible for blood filtration & urine production.  Each kidney contains ~1 million nephrons (constant).  Consists of: A. Renal corpuscle: ▪ Corpuscle = tiny body. ▪ Located in the cortex. ▪ Function: blood filtration & urine formation. ▪ Composed of: - Glomerulus: capillary network. - Glomerular (Bowman’s) capsule:  Double walled cup (simple squamous epithelium).  Visceral wall: surround the capillaries.  Parietal wall: continues with tubules. B. Renal tubules: ▪ Proximal convoluted tubule (PCT): in cortex. ▪ Loop of Henle: - In cortex & medulla. - Has descending & ascending limbs. ▪ Distal convoluted tubule (DCT): - In cortex. - Drain into collecting duct. ▪ Collecting Ducts: - Larger tubules that receive the DCT of several nephrons. - Each collecting duct & group of nephrons draining into its Renal Lobule. 4  ▪ Papillary ducts: - Large ducts that result from union of collecting ducts. - Located at the apex of renal pyramids (renal papilla). - Drain into minor calyx.  Types of Nephrons: A. Cortical nephron: ▪ 80–85%. ▪ Glomerulus in the outer part of cortex. ▪ Short loop of Henle. B. Juxtamedullary nephron: ▪ Glomerulus deep in the cortex. ▪ Long loop of Henle penetrates deeply into the medulla. o Draining system:  Each pyramid contains many collecting ducts.  Gathered to form Papillary ducts of Bellini (~20).  Drain through renal papilla (Apex of pyramid).  Each pyramid drains into Minor calyx (~8-18).  Minor calyces join into Major calyx (~2-3).  Major calyces join into Renal pelvis.  Renal pelvis drains to ureter. Blood Supply to Kidney o Arterial blood supply:  Renal arteries: ✓ At level of intervertebral disc of L1-L2. ✓ Right artery passes behind the inferior vena cava. ✓ At hilum, both arteries divided into large anterior & small posterior branches → give rise to 5 segmental arteries.  Segmental arteries: ✓ In renal sinus. ✓ Include: Superior (Apical) segmental artery1, Anterosuperior segmental artery2, Anteroinferior segmental artery3, Inferior segmental artery4, & Posterior segmental artery5 (only continuation of branch of renal artery). 5   Lobar arteries: one for each pyramid.  Interlobar arteries: pass through renal lobes.  Arcuate arteries: ✓ Over the bases of the pyramids. ✓ Arching between medulla and cortex.  Interlobular arteries: between lobules of the kidney. o Renal veins:  Lie anterior to the arteries.  Left Renal vein: ✓ Longer & crosses midline. ✓ Receives: ▪ Left gonadal vein. ▪ Left suprarenal vein. ▪ Left inferior phrenic vein. ✓ As it crosses midline, it traverses the acute angle between superior mesenteric artery (SMA) & abdominal aorta (AA).  Renal vein entrapment syndrome: ✓ AKA: Nutcracker Syndrome. ✓ Compression of Left renal vein at midline between SMA & AA. ✓ Syndrome: ▪ Hematuria &/or proteinuria. ▪ Left flank pain. ▪ Nausea & vomiting due to compression on 3rd part of duodenum. ▪ Left testicular pain in men. 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