Mammalian kidney

Mammalian kidney
Unipapillary, multilobar, smooth, bean-shaped camel kidney, in which the renal papillae are completely fused into the renal crest.[1]
Details
PrecursorUreteric bud, metanephrogenic blastema
SystemUrinary system and endocrine system
ArteryRenal artery
VeinRenal vein
NerveRenal plexus
LymphCollecting lymphatic vessels
Anatomical terminology

The mammalian kidneys are a pair of excretory organs of the urinary system of mammals,[2] being functioning kidneys in postnatal-to-adult individuals[3] (i. e. metanephric kidneys).[2] The kidneys in mammals are usually bean-shaped[4] or externally lobulated.[5] They are located behind the peritoneum (retroperitoneally)[6] on the back (dorsal) wall of the body.[7] The typical mammalian kidney consists of a renal capsule, a peripheral cortex, an internal medulla, one or more renal calyces, and a renal pelvis.[7] Although the calyces or renal pelvis may be absent in some species.[7] The medulla is made up of one or more renal pyramids,[8] forming papillae with their innermost parts.[9] Generally, urine produced by the cortex and medulla drains from the papillae into the calyces, and then into the renal pelvis, from which urine exits the kidney through the ureter.[7][10] Nitrogen-containing waste products are excreted by the kidneys in mammals mainly in the form of urea.[11]

The structure of the kidney differs between species.[12] The kidneys can be unilobar (a single lobe represented by a single renal pyramid) or multilobar,[13][14] unipapillary (a single or a common papilla), with several papillae or multipapillary,[14][15] may be smooth-surfaced or lobulated.[1][13] The multilobar kidneys can also be reniculate, which are found mainly in marine mammals.[16] The unipapillary kidney with a single renal pyramid is the simplest type of kidney in mammals, from which the more structurally complex kidneys are believed to have evolved.[17][6][18] Differences in kidney structure are the result of adaptations during evolution to variations in body mass and habitats (in particular, aridity) between species.[19][20][12]

The cortex and medulla of the kidney contain nephrons,[21] each of which consists of a glomerulus and a complex tubular system.[22] The cortex contains glomeruli and is responsible for filtering the blood.[7] The medulla is responsible for urine concentration[23] and contains tubules with short and long loops of Henle.[24] The loops of Henle are essential for urine concentration.[25] Amongst the vertebrates, only mammals and birds have kidneys that can produce urine more concentrated (hypertonic) than the blood plasma,[7] but only in mammals do all nephrons have the loop of Henle.[26]

The kidneys of mammals are vital organs[27] that maintain water, electrolyte and acid-base balance in the body, excrete nitrogenous waste products, regulate blood pressure, and participate in bone formation[28][29][30] and regulation of glucose levels.[31] The processes of blood plasma filtration, tubular reabsorption and tubular secretion occur in the kidneys, and urine formation is a result of these processes.[8] The kidneys produce renin[32] and erythropoietin[33] hormones, and are involved in the conversion of vitamin D to its active form.[34] Mammals are the only class of vertebrates in which only the kidneys are responsible for maintaining the homeostasis of the extracellular fluid in the body.[35] The function of the kidneys is regulated by the autonomic nervous system and hormones.[36]

The potential for regeneration in mature kidneys is limited[37][38] because new nephrons cannot be formed.[39] But in cases of limited injury, renal function can be restored through compensatory mechanisms.[40] The kidneys can have noninfectious and infectious diseases; in rare cases, congenital and hereditary anomalies occur in the kidneys of mammals.[41] Pyelonephritis is usually caused by bacterial infections.[42][43] Some diseases may be species specific,[44] and parasitic kidney diseases are common in some species.[45][46] The structural characteristics of the mammalian kidneys make them vulnerable to ischemic and toxic injuries.[47] Permanent damage can lead to chronic kidney disease.[48][49] Ageing of the kidneys also causes changes in them, and the number of functioning nephrons decreases with age.[50]

  1. ^ a b Abdalla 2020, p. 1, Abstract.
  2. ^ a b Withers, Cooper, Maloney et al. 2016, p. 25, 1.2.8 Excretion.
  3. ^ Vidya K Nagalakshmi; Jing Yu (17 March 2015). "The ureteric bud epithelium: morphogenesis and roles in metanephric kidney patterning". Molecular Reproduction and Development. 82 (3): 151–166. doi:10.1002/MRD.22462. ISSN 1040-452X. PMC 4376585. PMID 25783232. Wikidata Q30300352.
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  11. ^ Fenton, Knepper 2007, p. 679, Abstract.
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  13. ^ a b Breshears, Confer 2017, p. 617, Structure.
  14. ^ a b WHO 1991, p. 49, 3.4 Species, strain, and sex differences in renal structure and function.
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  16. ^ Ortiz 2001, p. 1832, Kidney structure.
  17. ^ Kriz, Kaissling 2012, p. 595, Renal vasculature.
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  19. ^ Zhou, Rong, Guo et al. 2023, p. 2, Introduction.
  20. ^ Zhou, Rong, Guo et al. 2023, p. 6, The Evolution of Renal Structures Was Driven by Body Size and Habitats in Mammals.
  21. ^ Davidson 2009, Figure 1. Structure of the mammalian kidney.
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  23. ^ C Michele Nawata; Thomas L Pannabecker (24 May 2018). "Mammalian urine concentration: a review of renal medullary architecture and membrane transporters". Journal of Comparative Physiology B. 188 (6): 899–918. doi:10.1007/S00360-018-1164-3. ISSN 0174-1578. PMC 6186196. PMID 29797052. Wikidata Q88802057.
  24. ^ Kriz, Kaissling 2012, p. 600, Nephrons and Collecting Duct System.
  25. ^ Casotti, Lindberg, Braun 2000, p. R1723.
  26. ^ Casotti, Lindberg, Braun 2000, p. R1722-R1723.
  27. ^ Little, McMahon 2012, p. 1, Summary.
  28. ^ Little, McMahon 2012, p. 2, An Overview of Cell Players and Cellular Processes in Metanephric Kidney Development.
  29. ^ Jing Yu; M. Todd Valerius; Mary Duah; et al. (1 May 2012). "Identification of molecular compartments and genetic circuitry in the developing mammalian kidney". Development. 139 (10): 1863–1873. doi:10.1242/DEV.074005. ISSN 0950-1991. PMC 3328182. PMID 22510988. Wikidata Q30419294. Archived from the original on 15 July 2022.
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  32. ^ M. L. S. Sequeira Lopez; R. A. Gomez (1 July 2010). "The renin phenotype: roles and regulation in the kidney". Current Opinion in Nephrology and Hypertension. 19 (4): 366–371. doi:10.1097/MNH.0B013E32833AFF32. ISSN 1062-4821. PMC 3079389. PMID 20502328. Wikidata Q30431545.
  33. ^ S. Suresh; Praveen Kumar Rajvanshi; C. T. Noguchi (1 January 2019). "The Many Facets of Erythropoietin Physiologic and Metabolic Response". Frontiers in Physiology. 10: 1534. doi:10.3389/FPHYS.2019.01534. ISSN 1664-042X. PMC 6984352. PMID 32038269. Wikidata Q89620015. Archived from the original on 8 May 2022.
  34. ^ D. D. Bikle (1 January 2011). "Vitamin D: an ancient hormone". Experimental Dermatology. 20 (1): 7–13. doi:10.1111/J.1600-0625.2010.01202.X. ISSN 0906-6705. PMID 21197695. Wikidata Q33783519. Archived from the original on 14 July 2022.
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  37. ^ Little, McMahon 2012, p. 12, 7 Reassessing Renal Disease, Repair, and Regeneration Using Developmental Biology.
  38. ^ Kumar 2018, p. 28, Figure 1 Schematic illustration highlighting patchy regenerative/reparative processes after mammalian acute kidney injury.
  39. ^ Davidson 2011, p. 1435, Introduction.
  40. ^ Davidson 2011, p. 1437-1439, Postnatal regenerative response of the mammalian kidney.
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  50. ^ Breshears, Confer 2017, p. 637, Aging of the Kidney.