Renal Structure and Function Flashcards
What are the main functions of the Kidney?
- Regulation of H2O and Electrolyte Balance
- Metabolic Waste Excretion
- Bioactive Substance Excretion (drugs and hormones)
- Regulation of Arterial Blood Pressure
- Regulation of RBC Production
- Regulation of Vitamin D Production
- Metabolism
What is Metabolic Waste?
Product of something that you metabolize/make in your own body
How do the kidneys maintain homeostasis due to the variable input of H2O and electrolytes?
By varying the output of water and minerals in the urine
What are some examples of Metabolic Waste that are excreted by the Kidneys and where do they come from?
- Urea (from Proteins)
- Uric Acid (from Nucleic Acids)
- Creatinine (from Muscle Creatine)
- Products from Hemoglobin breakdown
- Various Hormone metabolites (from Endocrine system)
Blood Pressure ultimately depends on what?
Blood Volume
How do the Kidneys regulate Arterial Blood Pressure?
- Regulating Blood Volume via maintenance of Na and H2O balance
- Releasing Vasoconstrictors that regulate smooth muscle in peripheral vasculature
How does the Kidney regulate RBC Production?
Releases Erythropoietin that controls erythrocyte production by the bone marrow
–Secretion of EPO is regulated by the partial pressure of O2 in Kidneys
What actions are performed by Vitamin D?
Tells Gut to increase Ca absorption
Where does the last step in producing Vitamin D occur?
Kidney
CNS is an obligate user of blood glucose meaning?
CNS can ONLY use Blood glucose as a fuel source
What metabolic process occurs in the Kidney?
Renal Ammonioagenesis which is a key way to excrete excess Acid from the body and is crucial to maintaining Acid-Base Homeostasis
What are Renal Columns?
Portions of the Renal Cortex that stretch into the Medulla and break it up
What has more surface area in the Kidney, Renal Cortex OR Renal Medulla?
Renal Cortex (ligher in color)
Where does a majority of Filtration occur in the Kidney?
Renal Cortex (lighter in color)
Where does a majority of Reabsorption happen in the Kidney?
Renal Cortex (darker in color) because most of the Distal and Proximal Tubules are located in the Renal Cortex
What is the functional unit of the Kidney and where are they found?
- The Nephron
2. Found majority in the Renal Cortex and a small part in the Renal Medulla
How many Nephrons does each Kidney have?
Roughly 1 million each so 2 million total
Describe Filtration in the Kidney and where it occurs:
Filtration of PLASMA occurs in the Glomerulus
About 180 L/day of plasma is filtered in the Nephron
About how much Plasma is excreted in Urine?
2 L/day
What is the Renal Corpuscle
“Balloon around the capillary”
- FILTERS BLOOD
- The Glomerulus (compact tuft of interconnected capillary loops) is surrounded by Bowman’s Space (balloon-like hollow capsule filled with fluid) that
What do you call the blood that is filtered from the Glomerulus into the Bowman’s Space and where does it go?
- Filtrate
2. Drains into Proximal Tubule
In what part of Nephron does a majority of reabsorption occur?
Proximal Tubule
How much of filtrate leaves the Proximal Tubule and goes back into the blood?
About 60%
What is the function of the Loop of Henle?
It creates and maintains an osmotic gradient in the Medulla
Where is the only place in the body that does not have an Osmolarity of 300 mOsm/L?
Surrounding the Loop of Henle (can get up to 1200 mOsm/L at the bottom of the gradient)
What is the Macula Densa?
Used to demarcate the area between the Loop of Henle an the Distal Tubule
What makes the Distal Tubule different than the Proximal Tubule?
Distal Tubule performs REGULATION as well as Reabsorption while Proximal only performs Reabsorption
What is reabsorbed in the Collecting Duct and how is that regulated?
ADH regulates WATER reabsorption in the Collecting Duct by opening up Aquaporin channels on the membrane when Osmolarity around the Collecting Duct is higher
What is necessary for Water to be Reabsorbed?
- Concentration gradient established by Loop of Henle
2. ADH
How thick is the Nephron?
1 Cell thick long tube
Where is the one place in the Nephron that has different cell types?
Distal Tubule:
- Principal Cells (primary)
- Intercalated Cells (alpha and beta) for Acid/Base balance
What happens in the Renal Medulla?
Concentration Gradient is established and can be used to concentrate Urine
What part of the Nephron runs right next to the Glomerulus?
the Distal Tubule
What is the Juxtaglomerular Apparatus?
Where the Distal Tubule runs right next to the Glomerulus and the Macula Densa cells can sense flow rate into the Glomerulus and stimulate Juxtaglomerular cells to secrete Renin which increases the amount of filtrate
What is the Renin-Angiotensin-Aldosterone System?
- Macula Densa sense low flow rate into the Glomerulus
- Macula Densa cells stimulate the Juxtaglomerular cells of the Glomerulus to secrete Renin
- Renin turns Angiotensinogen (produced by the Liver) into Angiotensin I
- Angiotensin I is converted by ACE (from lungs) into Angiotensin II
- Angiotensin II stimulates Aldosterone and ADH release in the Kidneys AND Vasoconstricts to increase BP
- Aldosterone reabsorbs Na and H2O in the Distal Tubule
- ADH opens up Aquaporin channels in Collecting Duct and increases H2O reabsorption
- Increased Filtrate causes negative feedback to shut off Macula Densa cells
What provides Nephron Heterogeneity?
The length of the Loop of Henle
What are the types of Nephrons?
- Outer Cortical (Superficial) Nephron
2. Juxtamedullary (Deep) Nephron
What percentage of Nephrons belongs to each type?
80% Outer Cortical (Superficial) Nephron
20% Juxtamedullary (Deep) Nephron
What kind of Nephron creates the Osmotic Gradient in the Medulla?
Juxtamedullary (Deep) Nephron
What percent of Cardiac Output goes to the Kidney and what is it called?
- “Renal Blood Flow (RBF)”
- 1 L/min (roughly 20% of CO)
Enters Kidney via the Renal Artery (1 per Kidney)
This means each Renal Artery roughly takes in 0.5 L/min and branches into 1 million Nephrons
What blood vessel enters the Glomerulus?
Afferent Arteriole
-has smooth muscle so it is regulate-able and has high pressure
What blood vessel exits the Glomerulus?
Efferent Arteriole
-has smooth muscle so it is regulate-able and has higher pressure
Where does blood go after the Efferent Arteriole?
- Peritubular Capillaries (goes to Cortical Nephron)
2. Vasa Recta (goes to Juxtamedullary Nephron)
What are Peritubular Capillaries?
Extend from Efferent Arterioles to the Cortical (Superficial) Nephrons and are profusely distributed throughout the Renal Cortex
What are Vasa Recta?
- Extend from Efferent Arterioles to the Juxtaglomedullary Nephrons
- Extend into the outer medulla where they divide many times to form bundles of parallel vessels that surround and supply blood to the the Loop of Henle
What is the difference between Plasma and Blood?
Plasma has NO RBCs
What are the 3 Renal Processes?
- Glomerular Filtration
- Tubular Reabsorption
- Tubular Secretion
What is the point of Secretion?
Moving of substances that were NOT filtered enough from the blood into the Nephron so it can be excreted
What is the formula for excretion?
Excretion= Filtration - Reabsorption + Secretion
What is the definition of Filtration?
Process by which water and solutes leave the vascular system through the filtration barrier and enter Bowman’s Space
What is the definition of Secretion?
Process of moving substances into the Tubular Lumen from the cytosol of Epithelial cells that form the walls of the Nephron
What is the definition of Reabsorption?
Process of moving substances from the Lumen across the epithelial layer of cells into the surrounding Interstitium where most substances are then taken up into surrounding blood vessels
What is the definition of Excretion?
Exit of a substance from the body
What is the definition of Synthesis?
Constructing a substance from molecular precursors
What is the definition of Catabolism?
Breaking down a substance into smaller component molecules
