Sistema Urinário de Gallus gallus domesticus

Abstract

The urinary system of the domestic chicken (Gallus gallus domesticus) has its own anatomical and functional characteristics. Understanding this system and its particularities is essential to ensure good meat and egg production. This was the objective of the materials developed by academics from the extension project “Knowing, respecting and producing birds: didactic and alternative models in the teaching and learning process”, linked to the discipline Comparative Anatomy of Domestic Animals (BA066) of the Zootechnics course at the Federal University of Paraná (UFPR). Chickens have two kidneys (right and left), located in the abdominal cavity and fitted into the synsacrum bone. They are elongated organs, divided into cranial, middle and caudal regions. Birds have two types of nephrons in their kidneys: cortical nephrons and medullary nephrons. These nephrons have absent or poorly developed loops of Henle, which limits the ability of birds to concentrate urine when compared to mammals. The formation and elimination of urine is similar to the process observed in mammals, involving glomerular filtration, reabsorption and tubular secretion. However, there are important differences: birds excrete uric acid, which does not remain dissolved in water. Thus, the urine mixes with the feces, and in the rectum Water reabsorption occurs, resulting in the formation of a white precipitate of urate crystals. One of the most striking characteristics of the avian urinary system is the renal portal system, responsible for conducting blood from the pelvic limbs first to the kidneys and only then to the heart. This generates two important effects: greater deposition of uric acid crystals in the caudal lobe and a greater impact of infections or toxins in that same region of the kidney. Another peculiarity of chickens is that, due to evolutionary adaptations related to flight, they do not have a bladder, which helps to keep their bodies lighter.