Fluid Balance: Renal Focus Flashcards
What are the 5 Functions of the Kidneys?
- Filters blood
- Eliminates Metabolic Byproducts
- Blood Pressure Regulation
- RBC Production Regulation
- Skeletal System
How do the Kidneys Filter Blood?
The blood enters the renal artery and filters the blood to send it back into the body through the renal vein.
How do the Kidneys Eliminate Metabolic Byproducts?
- The excess and waste metabolites from the blood get filtered out through urine and excreted through the urethra
- The blood passes through the nephrons! Each nephron includes a filter, called the glomerulus, and a tubule. The nephrons work through a two-step process: the glomerulus filters blood, and the tubule returns needed substances to circulation and removes wastes.
How are the Usuable Substances Returned?
A blood vessel runs alongside the tubule. As the filtered fluid moves along the tubule, the blood vessel reabsorbs almost all of the water, along with minerals and nutrients your body needs. The tubule helps remove excess acid from the blood. The remaining fluid and wastes in the tubule become urine.
How is Urine Created?
- The glomerulus filters water and other substances from the bloodstream.
- Inside the glomerulus, blood pressure pushes fluid from capillaries into the glomerular capsule, towards the filtration membrane.
- The filtration membrane, allows water and small solutes to pass but blocks blood cells and large proteins.
Reabsorption moves important/necessary nutrients and water back into the bloodstream. The resulting filtrate contains waste. - Waste ions and hydrogen ions pass from the capillaries into the renal tubule. This process is called secretion. The secreted ions combine with the remaining filtrate and become urine.
- The urine flows out of the nephron tubule into a collecting duct. It passes out of the kidney through the renal pelvis, into the ureter, and down to the bladder.
What are the Three Metabolic Byproducts During Excretion?
i. Amino acid byproduct: ammonia and urea
ii. Purine Byproduct: uric acid
iii. Creatinine Phosphate Byproduct: creatinine
How is the BP Regulated by the Kidneys?
The renin-angiotensin-aldosterone system contributes to blood pressure regulation as it controls the volume!
How Does the RAAS work?
- Blood Pressure Drops when the blood pressure drops below average it stimulates the initiation of the renin-angiotensin-aldosterone -system
- Sympathetic Nervous System: The drop in blood pressure stimulates the sympathetic nervous system.
- The stimulation of the sympathetic nervous system triggers the stimulation of the kidneys. Specifically, the juxtaglomerular cells release renin due to stimulation.
- The release of renin into the circulation causes the activation of angiotensinogen (synthesized and secreted by the liver).
- The reaction between renin and angiotensin causes the transformation of angiotensin I.
ACE (angiotensin-converting enzyme) is found in the endothelium of the kidney. The purpose of the ACE enzyme is to convert Angiotensin I to Angiotensin II. - Angiotensin II is responsible for constricting the blood vessel and increasing blood volume (Increase in angiotensin II= increase in vasocrontriction= increase in systemic vascular resistance= high blood pressure).
How do the Kidneys Make RBCs?
Red blood cells are made by the bone marrow. To get the marrow to make red blood cells, the kidneys make a hormone called erythropoietin, or EPO. Erythropoietin promotes the production of mature red blood cells in the bone marrow. More red blood cells lead to increased oxygenation.
How do the Kidneys Impact the Skeletal System?
The kidneys contribute to calcium homeostasis by adjusting the reabsorption and excretion of filtered calcium through processes that are regulated by parathyroid hormone (PTH) and vitamin D3
How is Vitamin D Activated?
Vitamin D is activated within the kidneys
The active form of Vitamin D is Calcitriol!
- Calcitriol acts on cells in the gastrointestinal tract to increase the production of calcium transport proteins, which results in increased uptake of calcium from the stomach into the body
Body Fluid Compartments.
- ICF- intracellular space (within the cells) Makes up 40% High potassium (K+)
- ECF- extracellular space (within plasma and interstitial cells)
Makes up 20%
High sodium (Na+), calcium (Ca+) and Chloride (Cl-)
Electrolyte tests are used to measure the ECF levels
Why are Pediatric Patients at Risk for Deydration?
In pediatric patients, up to 80% of the body’s weight is water and up to 50% is in ECF. therefore they are at a higher risk of dehydration!
Define Edema.
Edema is defined as the expansion of the interstitial fluid by 2-3 litres. Causing pitting and swelling within the extremities.
What Causes Edema?
- Increased capillary pressure
- Heart failure
- Kidney Disease or failure - Increased capillary permeability
- Inflammation
- Anaphylaxis, Sepsis
- Thermal Injury - Increased loss of proteins
- Burns
- Malnutrition/starvation - Immobility or limited movement
- Post-surgical patients
