Because blood plasma is one of the fluid components, osmotic pressure can directly influence blood pressure and other medical indicators. Learning Objectives Describe the process and purpose of osmoregulation. Key Points Osmoregulation maintains the proper balance of electrolytes in the human body, despite external factors such as temperature, diet, and weather conditions. By diffusion of water or solutes, osmotic balance ensures that optimal concentrations of electrolytes and non-electrolytes are maintained in cells, body tissues, and in interstitial fluid.
Solutes or water move across a semi-permeable membrane, causing solutions on either side of it to equalize in concentration. Cells in hypotonic solutions swell as water moves across the membrane into the cell, whereas cells in hypertonic solutions shrivel as water moves out of the cell.
Key Terms electrolyte : any of the various ions such as sodium or chloride that regulate the electric charge on cells and the flow of water across their membranes osmosis : The net movement of solvent molecules from a region of high solvent potential to a region of lower solvent potential through a partially permeable membrane osmotic pressure : the hydrostatic pressure exerted by a solution across a semipermeable membrane from a pure solvent.
What is osmoregulation? Internally, the kidney has three regions: an outer cortex, a medulla in the middle, and the renal pelvis in the region called the hilum of the kidney. The hilum is the concave part of the bean-shape where blood vessels and nerves enter and exit the kidney; it is also the point of exit for the ureters. Structure of the kidney : Externally, the kidney is surrounded by the renal fascia, the perirenal fat capsule, and the renal capsule.
Internally, the kidney is most importantly filled with nephrons that filter blood and generate urine. Because the kidney filters blood, its network of blood vessels is an important component of its structure and function.
The arteries, veins, and nerves that supply the kidney enter and exit at the renal hilum. Renal blood supply starts with the branching of the aorta into the renal arteries which are each named based on the region of the kidney they pass through and ends with the exiting of the renal veins to join the inferior vena cava. The renal arteries split into several segmental arteries upon entering the kidneys. Each segmental artery splits further into several interlobar arteries that enter the renal columns, which supply the renal lobes.
The interlobar arteries split at the junction of the renal cortex and medulla to form the arcuate arteries. Cortical radiate arteries, as the name suggests, radiate out from the arcuate arteries, branch into numerous afferent arterioles, and then enter the capillaries supplying the nephrons.
The nephron, the functional unit of the kidney, is responsible for removing waste from the body. Each kidney is composed of over one million nephrons that dot the renal cortex, giving it a granular appearance when sectioned sagittally from front to rear.
Eighty-five percent of nephrons are cortical nephrons, deep in the renal cortex; the remaining 15 percent are juxtamedullary nephrons, which lie in the renal cortex close to the renal medulla. The nephron is the functional unit of the kidney. A nephron consists of three parts: a renal corpuscle, a renal tubule, and the associated capillary network, which originates from the cortical radiate arteries. The renal tubule is a long, convoluted structure that emerges from the glomerulus.
It can be divided into three parts based on function. The first part is called the proximal convoluted tubule PCT , due to its proximity to the glomerulus. The second part is called the loop of Henle, or nephritic loop, because it forms a loop with descending and ascending limbs that goes through the renal medulla.
The third part of the renal tubule is called the distal convoluted tubule DCT ; this part is also restricted to the renal cortex. This last part of the nephron connects with and empties its filtrate into collecting ducts that line the medullary pyramids. The collecting ducts amass contents from multiple nephrons, fusing together as they enter the papillae of the renal medulla.
Urine leaves the medullary collecting ducts through the renal papillae, emptying into the renal calyces, the renal pelvis, and finally into the bladder via the ureter. All the blood in the human body is filtered about 60 times a day by the kidneys.
The nephrons remove wastes, concentrate them, and form urine that is collected in the bladder. Internally, the kidney has three regions—an outer cortex, a medulla in the middle, and the renal pelvis, which is the expanded end of the ureter. The renal cortex contains the nephrons—the functional unit of the kidney. The renal pelvis collects the urine and leads to the ureter on the outside of the kidney. The ureters are urine-bearing tubes that exit the kidney and empty into the urinary bladder.
Blood enters each kidney from the aorta, the main artery supplying the body below the heart, through a renal artery.
It is distributed in smaller vessels until it reaches each nephron in capillaries. Within the nephron the blood comes in intimate contact with the waste-collecting tubules in a structure called the glomerulus. Water and many solutes present in the blood, including ions of sodium, calcium, magnesium, and others; as well as wastes and valuable substances such as amino acids, glucose and vitamins, leave the blood and enter the tubule system of the nephron.
As materials pass through the tubule much of the water, required ions, and useful compounds are reabsorbed back into the capillaries that surround the tubules leaving the wastes behind. Some of this reabsorption requires active transport and consumes ATP. Some wastes, including ions and some drugs remaining in the blood, diffuse out of the capillaries into the interstitial fluid and are taken up by the tubule cells. These wastes are then actively secreted into the tubules.
The blood then collects in larger and larger vessels and leaves the kidney in the renal vein. The renal vein joins the inferior vena cava, the main vein that returns blood to the heart from the lower body.
The amounts of water and ions reabsorbed into the circulatory system are carefully regulated and this is an important way the body regulates its water content and ion levels.
The waste is collected in larger tubules and then leaves the kidney in the ureter, which leads to the bladder where urine, the combination of waste materials and water, is stored. The bladder contains sensory nerves, stretch receptors that signal when it needs to be emptied.
These signals create the urge to urinate, which can be voluntarily suppressed up to a limit. The conscious decision to urinate sets in play signals that open the sphincters, rings of smooth muscle that close off the opening, to the urethra that allows urine to flow out of the bladder and the body.
Dialysis is a medical process of removing wastes and excess water from the blood by diffusion and ultrafiltration.
When kidney function fails, dialysis must be done to artificially rid the body of wastes and fluids. This is a vital process to keep patients alive. In some cases, the patients undergo artificial dialysis until they are eligible for a kidney transplant. In others who are not candidates for kidney transplants, dialysis is a lifelong necessity. Dialysis technicians typically work in hospitals and clinics.
While some roles in this field include equipment development and maintenance, most dialysis technicians work in direct patient care. Their on-the-job duties, which typically occur under the direct supervision of a registered nurse, focus on providing dialysis treatments.
Water is lost from the body as:. Sweat glands in the skin produce sweat. Water, ions and urea are lost from the skin as they are contained in sweat.
Water leaves the body via the lungs when we exhale as well as excess carbon dioxide. We cannot control the level of water, ion or urea loss by the lungs or skin.
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