Clearance tests and micturition are essential aspects of kidney function and urinary system regulation. These processes help monitor kidney health, assess kidney filtration capacity, and ensure effective urine elimination from the body.
SCROLL DOWN TO THE BOTTOM OF THE PAGE FOR ACTUAL NOTES
Clearance Tests:
Clearance tests are medical examinations used to estimate the glomerular filtration rate (GFR) of the kidneys. GFR refers to the rate at which the kidneys filter waste and excess substances from the blood. A decline in GFR may indicate impaired kidney function and is a crucial marker for kidney diseases.
The two most commonly used clearance tests are:
- Creatinine Clearance Test: This test measures the amount of creatinine (a waste product from muscle metabolism) present in a 24-hour urine sample, as well as the creatinine level in the blood. By comparing the creatinine concentration in the urine and blood, doctors can estimate the GFR, which reflects the kidneys’ ability to filter creatinine. A decreased GFR suggests reduced kidney function.
- Glomerular Filtration Rate (GFR) Estimated by Serum Creatinine: This test involves a simple blood test to measure the concentration of creatinine in the blood. The result is used to estimate the GFR using a formula that takes into account age, sex, race, and body size. This estimated GFR is an essential tool for identifying kidney dysfunction.
Clearance tests are valuable in diagnosing and monitoring kidney diseases, determining the progression of kidney dysfunction, and guiding treatment decisions.
Micturition:
Micturition, commonly known as urination or voiding, is the process of discharging urine from the urinary bladder to the outside of the body. It is a coordinated and controlled process involving the following steps:
- Filling of the Urinary Bladder: The urinary bladder gradually fills with urine from the kidneys through the ureters. As the bladder stretches, it triggers stretch receptors, which signal the brain that the bladder is becoming full.
- Initiation of Micturition Reflex: When the bladder reaches its capacity, nerve signals from the stretch receptors travel to the spinal cord and then to the brain’s micturition center, located in the pons. The micturition center coordinates the reflex for urination.
- Voluntary Control: Under normal circumstances, the micturition reflex can be voluntarily delayed or suppressed, allowing us to hold urine until a suitable time and place for urination. This control is mediated by higher brain centers, giving us conscious control over the process.
- Voiding Phase: When it is convenient and appropriate to urinate, the brain sends signals to relax the external urinary sphincter (a ring of muscle surrounding the urethra) and contract the bladder’s detrusor muscle. These coordinated muscle actions lead to the expulsion of urine from the bladder through the urethra.
In infants and very young children, micturition is primarily a reflex action, and they have limited voluntary control over urination. As children mature, they develop more conscious control over the micturition process.
In conclusion, clearance tests are essential in assessing kidney function, while micturition is the coordinated process of emptying the urinary bladder. Both processes are crucial for maintaining proper kidney health and eliminating waste products from the body effectively.
ACTUAL NOTES
