Water concentration of body is monitored by osmoreceptors in hypothalamus, which detect concentration of electrolytes in extracellular fluid. When osmolarity (plasma sodium concentration) increases above normal because of water deﬁcit, feedback system operates.
Osmoreceptors are sensory receptor primarily found in hypothalamus ( located in vascular organ of lamina terminalis, a circumventricular organ ) of most homoeothermic organisms that detects changes in osmotic pressure. They contribute to osmoregulation controlling fluid balance in the body. They are defined functionally as neurons that have an intrinsic ability to detect changes in osmolality.
Tubular secretion is the transfer of materials from peri-tubular capillaries to the renal tubular lumen which is reversal of reabsorption.
This step is usually used to remove drugs, toxins and poisons, or other natural compounds in excessive amounts (such as potassium (K+), hydrogen (H+), and urea).
Most reabsorption from filtrate takes place in proximal convoluted tubule, whose walls are lined with microvilli to increase surface area for absorption. This process is selective reabsorption. Reabsorption of some substance is passive, while some substances are actively transported.
Urine formation begins with ﬁltration of large amounts of ﬂuid through glomerular capillaries into Bowman’s capsule. Glomerular Filtration takes place through the semipermeable walls of the glomerulus and glomerular capsule.
The filtrate in the glomerulus is very similar in composition to plasma with the important exceptions of plasma proteins and blood cells.
Pale yellow, Amber or honey pee color is normal urine. Abnormal color may be caused by infection, disease, medicines, or food consumed. Pigments and other compounds in certain foods and medications can change its color. Various abnormally colored urine may be observed.
Urine is a liquid by-product of metabolism in humans and in many animals. It is a collection of substances that have not been reabsorbed during glomerular filtration or tubular secretion and flows from kidneys to urinary bladder through the ureters.