Kidneys: Key Information

Kidneys Key Information • • • • • retroperitoneal in the abdomen one on each side of the vertebral column They are approximately 10-12cm in length, 6 cm in width and 3 cm thick kidneys extend from the T12 to L4 vertebrae, with the right kidney situated slightly lower than the left (right L1-L4, left T12-L3) They are embedded in fat (perirenal fat) and surrounded by a fascia (renal fascia). Anatomical relations of the kidneys • • • • Anterior to the 12th rib on the right side and 11th and 12th rib on the left side. Posterior relations of the kidneys include psoas major, quadratus lumborum and transverse abdominis muscles, subcostal vessels and nerves (T12) and the iliohypogastric and ilioinguinal nerves (branches of L1 spinal nerve). The renal hilum is located at the concave medial margin of the kidney and contains the renal artery, renal vein (left vein longer than right vein and arise from the aorta at level L1-L2) and the upper end of the ureter. Normally the renal vein is anterior, the ureter posterior and the renal artery in between (secondary branches of the vessels are not unusual). Surface features • Anterior and posterior surfaces Upper and lower poles Lateral and medial borders Hilum Renal fascia: (also known as Gerota’s fascia or perirenal fascia) – encloses the kidneys and the suprarenal glands. Perirenal fat: collection of extraperitoneal fat. • Pararenal fat – mainly located on the posterolateral aspect of the kidney. • • • • • Internal structures • • • • • • • Renal capsule – tough fibrous capsule. Cortex: extends into the medulla, dividing it into triangular shapes – these are known as renal pyramids. Medulla - Pyramids: small structures that contain strings of nephrons and tubules - Columns: connective tissue extensions that radiate downward from the cortex through the medulla to separate the most characteristic features of the medulla, the renal pyramids and renal papillae. Renal papilla: - apex of a renal pyramid is called a renal papilla. - Each renal papilla is associated with a structure known as the minor calyx. location where the renal pyramids in the medulla empty urine into the minor calyx in the kidney Calyces - Major: Several minor calyces converge to form a major calyx. urine passes through the major calices into the renal pelvis - Minor: A minor calyx surrounds the renal papillae of each pyramid and collects urine from that pyramid Renal pelvis: - The area at the centre of the kidney - flattened and funnel-shaped structure. From the renal pelvis, urine drains into the ureter, which transports it to the bladder for storage. Renal sinus: - The renal sinus is a fat-filled cavity in the middle of the kidney that cushions important parts. Blood Supply Arteries • • • • • • Renal artery Segmental arteries Interlobar arteries Arcuate arteries Interlobular arteries Afferent arterioles Venous Drainage Vein Renal Description • serval renal veins drain each kidney and unit in a variable fashion from the right and left renal vein • these veins lie anterior to the right and left renal arteries. • the longer left renal vein receives the left suprarenal vein, left gonadal vein and a communication with the ascending lumbar vin, it then traverses the acute angle between the SMA anteriorly and the IVC posteriorly. • each renal vein drains into the IVC Lymphatic Drainage Pathways • • left to the left lateral para-aortic nodes. right to the right interaorticocaval and paracaval nodes Innervation Type Sympathetic Some Parasympathetic Descriptions • T12 – L1 • Mainly celiac plexus to the renal plexus • renal branches of the vagus nerve to the celiac plexus and the renal plexus Suprarenal/adrenal glands Key information • The suprarenal glands are found on the posterior poles of the kidneys and are surrounded by adipose tissue. • The suprarenal glands can be divided into two functionally and histologically distinct parts, the suprarenal cortex and the suprarenal medulla. • The suprarenal cortex secretes corticosteroid class of hormones regulated by the pituitary hormone ACTH, and the suprarenal medulla secretes epinephrine and norepinephrine under the control of the sympathetic nervous system. Internal Structure Blood Supply and Vasculature Artery Superior suprarenal arteries Middle suprarenal arteries Inferior suprarenal arteries Description (6–8) from the inferior phrenic arteries. (£ 1) from the abdominal aorta near the level of origin of the SMA (£ 1) from the renal arteries Venous Drainage • Occurs via large suprarenal veins - Short suprarenal vein -> drains into IVC - Longer left suprarenal vein often joined by the inferior phrenic vin -> empties into the left renal vein Innervation • • Celiac plexus Splanchnic nerves