Kidney

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The relations of the viscera and large vessels of the abdomen.

The kidney is involved in the purification and filtering of blood. Kidneys are located retroperitoneally in the abdominal cavity, and are smooth, bean-shaped organs approximately 12 cm long, 6 cm wide and 3 cm thick. On the medial side is the hilum, through which the renal blood vessels, lymphatics, nerves and renal pelvis enter or leave the renal sinus. The liver usually pushes the right kidney to a slightly lower level.

Coverings

The kidneys are covered by a thin, fibrous capsule and embedded in perirenal fat which extends into the renal sinus. The perirenal fat is in turn covered by a renal fascia, which itself is covered by pararenal fat. Also embedded within the fat are:

Relations

Left Kidney

The following are closely related to the anterior surface of the left kidney:

Right Kidney

The main anterior relations of the right kidney are:

Internal anatomy

Vertical section of kidney.

Internally, the kidney is comprised of an outer cortex and an inner medulla. These are separated from one another by inward extensions of the cortex, called renal columns. The apex of each pyramid extends towards the renal sinus as a renal papilla which contains mainly collecting ducts. These drain from the tip of the papilla into a minor calyx (8-10 / kidney). The minor calyces open into 2-3 major calyces which unite to become the renal pelvis. The renal pelvis then narrows and leaves the renal sinus as the ureter. Significant parts to spot in the vertical section of kidney are:

  1. renal artery
  2. renal vein
  3. renal cortex
  4. renal medulla
  5. renal calyces
  6. medullary pyramids
  7. renal pelvis
  8. ureter

Also, nephrons are, like, super-important.

Tubules

The tubular segments through which ultrafiltrate flows are the proximal and distal tubules. The proximal tubules have convoluted early and middle segments in the renal cortex, but a straight outer segment which enters the outer medulla. The loop of Henle has medullary thin descending and thin ascending limbs and a thick ascending limb with outer medullary and cortical segments. The cortical distal diluting segments include the early distal tubule, which makes contact with the afferent arteriole at the macula densa cells forming the juxtaglomerular apparatus. The collecting duct has cortical, outer medullary and inner medullary segments.

Vessels

Arteries

The right renal artery is longer than the left and passes posterior to the inferior vena cava. Both arteries give branches to the ureters and suprarenal glands, as well as to the kidney.

Veins

The renal veins empty into the inferior vena cava and pass anterior to the corresponding arteries. The left vein is longer than the right and passes anterior to the aorta to reach the inferior vena cava. It receives the left suprarenal vein and the left gonadal vein.

Lymphatics

The lymphatic drainage of the kidney is to para-aortic (lumbar) lymph nodes.

Innervation

The autonomic supply is through the renal plexus, an offshoot of the coeliac and aorticorenal plexus. Its efferent component is mainly sympathetic and is vasomotor. Preganglionic parasympathetic fibers from the vagal trunks also contribute to the plexus. Pain afferents arise mainly from the renal pelvis and reach the spinal cord at T10-L2 segments, therefore referred pain from the kidneys is often felt over the T10-L1.

Development

  • state the developmental origins of the urogenital and nephrogenic ridges
  • Happens during the 4th week of development
  • intermediate mesoderm (located between the somites and lateral mesoderm) begins to proliferate
  • This forms bilateral, longitudinal urogenital ridges, which bulge into the dorsal aspect of the coelom
  • Nephrogenic ridge (cord): Formed by the lateral part of each ridge
  • which gives rise to much of the urinary system, while the medial part of the ridge becomes the genital, or gonadal ridge, responsible for the formation of parts of the male and female reproductive systems.


  • state the roles of the ureteric bud and metanephric mesoderm in kidney development


  • list the parts of the kidney tubule and duct system that are derived from the ureteric bud and metanephric vesicle


  • outline the ascent of the kidneys and the accompanying changes in blood supply


  • outline the development of the bladder and urethra from the urogenital sinus


  • outline the role of the mesonephric ducts in the formation of the trigone of the bladder


  • explain the following in terms of abnormal development of the urinary system: renal agenesis, pelvic kidney, horseshoe kidney, polycystic, ectopic kidneys, exstrophy bladder .

Abnormalities

The kidney can become abnormal in several ways. Some of the conditions are:


Pathology

  • To acquire basic concepts of the pathogenesis of both primary and systemic glomerular diseases
  • To define the nephrotic syndrome and describe the commonest clinico-pathological patterns associated with the nephrotic syndrome
  • Define nephritis and to outline the commonest pathological syndromes associated with nephritis

Histology

  • describe the anatomical organization of the kidney.
  • list the components of a uriniferous tubule.
  • prepare a labeled diagram of a renal corpuscle.
  • list the components of the urinary filtration barrier.
  • name the factors that contribute to ultrafiltration.
  • describe components, location and function of the juxtaglomerular apparatus.
  • compare the epithelial lining of proximal tubule, thin segment and distal tubule.
  • describe the location and histology of the renal medulla.
  • explain the structure and significance of transitional epithelium.
  • compare the features of ureter and urinary bladder.

Objectives

  • state the location of the kidneys within the abdominal cavity and in relation to bony landmarks
  • name the connective tissue coverings of the kidney
  • describe the external and internal features of the kidney
  • list the anterior relations of the left and right kidneys
  • name the structures in the hilum of the kidney and state their relationship to one another
  • describe the features of the ureters, their intra-abdominal course and state their relationship to gonadal and intestinal vessels
  • describe the features of the suprarenal glands and state their location and functions
  • state the arterial supply, venous drainage and lymphatic drainage of the kidneys, ureters and suprarenal glands
  • state the nerve supply to the kidneys, ureters and suprarenal glands, with particular reference to pain
  • state the most likely sites of obstruction of the ureters due to a urinary calculus (stone)
  • state the functional significance of the sympathetic innervation of the suprarenal glands.


Resources