Exam 3: Urinary & Digestive Flashcards
(96 cards)
Functions of the Kidneys
Filters blood, excreting toxic metabolic wastes
Regulates blood volume, pressure, and osmolarity
Regulates electrolytes
Regulates pH balance
Secretes erythropoietin
Regulates Ca2+ levels
Clears hormones from the blood via urination
Detoxifies free radicals
Peristaltic Contraction
A wave contraction from one end of the ureter to the other, ensuring constant outflow. This same contraction occurs in the intestines.
What Nitrogenous Wastes are removed through urination?
Urea, Uric Acid, & Ammonia
Urea Formation Steps
Proteins -> Amino Acids -> NH2 removed -> Ammonia
Ammonia is converted to Urea by the liver
Urea can be converted to Uric Acid
Major Nitrogenous Wastes
Ammonia - Most toxic when abundant in the body
Urea - Formed from converted Ammonia, less toxic
Uric Acid - Product of Nucleic Acid Catabolism
Creatinine - Product of creatine phosphate catabolism
Where does filtration occur in the kidneys?
Filtration starts in the cortex and then moves into the medulla via nephrons. Most of the work occurs in the medulla.
What are calyxes
Dumping stations where anything that enters becomes urine. There is no more filtration, secretion, or absorption from the calyx to the urethra.
Why is the kidney highly vascularized?
There is constant filtration occurring, which is highly metabolic and requires more blood flow. They receive about 21% of all cardiac output
What is the route of Renal Circulation?
Renal Artery, Segmental Artery, Interlobar Artery, Arcuate Artery, Cortical Radiate Artery, Afferent Artery, Glomerulus, Efferent Arteriole, Peritubular Capillaries or Vasa Recta, Cortical Radiate Vein, Arcuate Vein, Interlobar Vein, Renal Vein
Where does O2 transport occur in the Kidneys?
Peritubular Capillaries, after blood passes through them it is deoxygenated and begins venous return
How is the Glomerulus Capillary Bed different from others?
The Glomerulus is for filtration, only moving sugars and not O2/CO2
What are the two principal parts of a nephron and what are their functions?
Renal Corpuscle (Glomerulus) - Filters the blood plasma
Renal Tubule (PCT, Loop, DCT) - A long, coiled tube that converts the filtrate into urine
Glomerular Capsule Layers and Tissue Types?
Parietal Layer - Simple Squamous Epithelium
Visceral Layer - Podocyte cells provide structure and support to keep the capillaries from tearing under high-pressure
Types of Nephrons and their Abundance
Juxtamedullary Nephrons - 15% of all nephrons
Cortical Nephrons - 85% of all nephrons
Juxtamedullary Nephrons
Better at conserving water
Efferent Arterioles branch into the vasa recta
The loop branches down farther into the medulla
Longer of the two types
Cortical Nephrons
Shorter of the two types
Efferent arterioles branch into peritubular capillaries
Stages of Urine Formation
1) Glomerular Filtration: Ultra-filtration Filtration is driven by BP where small molecules (Ca2+, Na+, K+, glucose, Mg+, H2O) are pushed out to the proximal tubule and large proteins and cells remain in the blood.
2) Tubular Reabsorption: Useful molecules are transported from the tubule to the blood
3) Tubular Secretion: Waste from the blood is moved to the tubule
4) Water Conservation: Water is removed from the urine and returned to the blood
Hydration and Water Conservation
Dehydration causes an increase in water conservation
Overhydration causes a decrease in water conservation
Glomerular Filtration Membranes
Fenestrated Endothelium: Highly permeable with large filtration pores, doesn’t let blood cells through
Basement Membrane: Proteoglycan gel with a negative charge that repels albumin and has very small filtration pores
Filtration slits: Openings through podocytes that are medium in size and negatively charged. Increases the rate of flow out of the capillaries
Molecule Size and Glomerular Filtration
Any molecule smaller than 3 nm can pass freely through the membrane. This includes water, electrolytes, glucose, fatty acids, amino acids, nitrogenous wastes, and vitamins
Some substances of low molecular weight are bound to the plasma proteins and cannot get through the membrane. This includes calcium, iron, and thyroid hormone. If these molecules are unbound, they pass through.
Forces involved in Glomerular Filtration
Blood Hydrostatic Pressure (BP) is the only force driving substances out of the capillary
Colloid Osmotic Pressure is a concentration pressure from the surrounding fluids (H2O) pushing back into the capillary
Capsular Pressure is the hydrostatic pressure that pushes back into the capillary.
If BP falls too low, the kidneys will not work due to the lack of pressure driving fluid through the glomerulus.
Adding all three forces gives us Net Filtration Pressure, which must be positive
Glomerular Filtration Rate
The amount of filtrate formed per minute by both kidneys. The total amount of filtrate produced per day is about 50-60 times the amount of blood in the body, though nearly all of it is reabsorbed.
Why is it important to regulate the Glomerular Filtration Rate?
If GFR is too high, fluid cannot reabsorb. Urine output will also rise, potentially leading to dehydration and electrolyte depletion.
If GFR is too low, wastes are reabsorbed rather than expelled to the bladder
Methods of GFR Control
Renal Autoregulation
Sympathetic Control
Hormonal Control