Pronephros
Pronephros is the most primitive of the three excretory organs that develop in vertebrates. It is the first kidney to form during the embryonic development of vertebrates and is functional in the larvae of fish and amphibians. In higher vertebrates, such as reptiles, birds, and mammals, the pronephros is a transient structure that is eventually replaced by the mesonephros and then the metanephros.
Development[edit | edit source]
The pronephros develops from the intermediate mesoderm in the early embryo. It appears as a series of tubules that connect to the pronephric duct, which eventually becomes the mesonephric duct. These tubules are segmented and form in a cranial-to-caudal sequence. In mammals, the pronephros is non-functional and regresses early in development, while in lower vertebrates, it serves as a functional excretory organ during the larval stage.
Structure[edit | edit source]
The pronephros consists of a series of nephrotomes, which are segmented structures that contain nephric tubules. These tubules open into the coelomic cavity and are connected to the pronephric duct. The pronephric duct extends caudally and eventually connects to the cloaca in lower vertebrates or to the mesonephric duct in higher vertebrates.
Function[edit | edit source]
In lower vertebrates, the pronephros functions as an excretory organ during the larval stage. It filters waste products from the blood and excretes them into the surrounding environment. In higher vertebrates, the pronephros is non-functional and serves as a precursor to the more advanced mesonephros and metanephros.
Evolutionary Significance[edit | edit source]
The pronephros is considered an evolutionary relic, representing the earliest form of the vertebrate kidney. Its presence in the embryonic development of higher vertebrates suggests a common ancestry with lower vertebrates. The transition from pronephros to mesonephros and metanephros reflects the increasing complexity and specialization of the excretory system in vertebrates.
Related Pages[edit | edit source]
See Also[edit | edit source]
| Urinary system - Kidney - edit |
|---|
| Renal capsule | Renal cortex | Renal medulla (Renal sinus, Renal pyramids) | Renal calyx | Renal pelvis |
| Nephron - Renal corpuscle (Glomerulus, Bowman's capsule) → Proximal tubule → Loop of Henle → Distal convoluted tubule → Collecting ducts
Juxtaglomerular apparatus (Macula densa, Juxtaglomerular cells) Renal circulation - Renal artery → Interlobar arteries → Arcuate arteries → Cortical radial arteries → Afferent arterioles → Glomerulus → Efferent arterioles → Vasa recta → Arcuate vein → Renal vein |
| Renal physiology |
| Filtration - Ultrafiltration | Countercurrent exchange
Hormones effecting filtration - Antidiuretic hormone (ADH) | Aldosterone | Atrial natriuretic peptide Endocrine - Renin | Erythropoietin (EPO) | Calcitriol (Active vitamin D) | Prostaglandins |
| Assessing Renal function / Measures of Dialysis |
| Glomerular filtration rate | Creatinine clearance | Renal clearance ratio | Urea reduction ratio | Kt/V | Standardized Kt/V | Hemodialysis product |
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