Unit 3 Lecture 1: Intro to Renal Physiology Flashcards
What is the renal cortex & renal medulla
The outer portion is the cortex & the inner more part is the medulla; both are key to filtration
What are the main roles of the Kidney
- Fluid and Ion homeostasis
- Waste excretion
- Drug removal (can determine when it can be removed)
- Hormone production
- Glucose synthesis
When it comes to Fluid and Ion homeostasis what does this include?
- ECF volume/blood pressure (more fluid in the system can acutely change blood pressure)
- Regulates osmolarity and ion balance (it can secrete or absorb many ions depending on how the body is feeling or excrete or absorb more water depending on how much water the body has)
- Can balance out pH by H+ excretion or reuptake
Note: A lot of fluid and ion homeostasis is done through either excretion or uptake of the things mentioned above
What are some examples of hormones produced or activated when it comes to the kidneys?
- Erythropoietin (EPO)
- Renin ==> Angiotensin 2
- Vitamin D activation
Total Body Fluid Volume is?
The amount of fluid in the entire body if you were to dehydrate every cell: 40L
- 3L of it is plasma
How much blood and plasma do the kidneys receive?
The renal blood flow is 22% of CO (1500L/day) but since plasma is 60% of blood, that is equal to 900L/day
Do the kidneys filter blood itself?
The kidneys technically filter through the plasma in the blood which makes up 60% of the blood.
HOWEVER; Only 20% of the renal plasma flow is filtered by the glomerulus (180L/day)
REMEMBER: 60% of renal blood flow is taken up (renal plasma flow) but of that 60%, only 20% of the renal plasma flow is filtered through the glomerulus)
According to the GFR we should lose about 180L/day but that doesn’t make sense. Why is that?
We realistically lose only 1.5L/day because most of the fluid lost is reabsorbed
Explain how the glomerulus works when it comes to plasma and blood?
The glomerulus takes in plasma and blood through the afferent arteriole and siphs through it to see what ions and hormones it needs to take then whatever is not needed is sent back to the venous system via the efferent arteriole
When ions and hormones are filtered by the glomerulus where do they head down through?
They head down through the Bowman’s Capsule
If we have 625mL plasma/min arriving at the afferent arteriole and into the glomerulus and we only filter 20% of it, how much plasma is filtered? How much goes back to the vasculature?
125mL/min is filtered; 500mL plasma/min goes back to the vasculature
When the plasma is being filtered what is something unique that occurs with the fluid?
More than 19% of the 20% of fluid is going to be reasborbed into the peritubular capillary and into the venous system; cannot lose too much fluid in one sitting
Note: >99% is being reabsorbed while <1% is being secreted (5mL leaves; 620mL remains in the system)
What is the Juxtaglomerular apparatus?
Is it the site where Renin is produced
Explain the path of filtrate from the glomerulus
- Glomerulus to Bowman’s space (Renal corpuscle)
- Proximal convoluted tubule
- Proximal straight tubule
- Descending thin loop of henle
- Ascending loop of henle
- Ascending thick loop
- Distal convoluted tubule
- Cortical collecting duct
- Medullary collecting duct
- Renal Pelvis
What is the pathway for renal blood supply?
- Renal Artery
- Afferent Arteriole
- Glomerulus (i.e. Capillaries)
- Efferent Arteriole
- Pertibular Capillaries or Vasa Recta
- Venules
- Renal Vein
Note: Typically after afferent arteriole blood should go to the capilaries then the veins but they go to the efferent arteriole instead of the veins
At different parts of the nephrons, what is happening?
Different ions will be secreted or absorbed
Note: Back and forth filtration and secretion happens through both passive and active transport
How many types of nephrons are there? What are they called?
2 Nephrons; Juxtamedullary nephrons & Cortical Nephrons
What are some distinct features when it comes to Juxtamedullary and Cortical Nephrons?
- Both are in the renal corpuscle
- Cortical = shorter loop of Henle
- Most nephrons = cortical (80%)
- Large vasa recta in Juxtamedullary
- More concentrated urine = long Henle loop = Juxtamedullary
- Excretory & regulatory functions (water reabsorption) = Cortical
Define Glomerular filtration
Non-discriminant filtration of protein-free plasma from glomerulus into Bowman’s Capsule
- Non-discriminant - The size of the holes determine what siphs through
Note: This allows small ions and proteins to go through and prevent RBCs and WBCs from being filtered
What is Tubular Reabsorption?
The reabsorption of select substances that have already been filtered; Tubule to capillaries
What is Tubular Secretion?
Things not filtered by glomerulus (sent to efferent arteriole), are secreted into the tubules
What is the formula for figuring out the amount of solute excreted?
(Amount Filtered - Amount reabsorbed) + Amount Secreted
What determines whether filtration occur?
The filtration barrier; if the substance is an ion or small protein it can then go through the barrier
- Water, ions, small molecules can go through
- RBCs, WBCs, Plasma Proteins cannot
What property of the glomerulus allows for it to filter? What property of the Tubule allows for the substances to not leak through?
- The glomerulus capillary is composed of endothelial cells (easily allows things to pass)
- Epithelial cells which are what make the tubule make sure substances don’t slip out
What are podocytes?
Found on the glomerular capillary, these are large spaces in between where filtration occurs
Explain the movement of filtrate from the glomerular capillary to the bowman’s capsule
- Filtrate moves through gaps between endothelial cells known as fenestrations
- Moves through basement membrane
- Goes through podocyte slits (surrounded around the glomerular capillary) and moves into the lumen of Bowman’s capsule
When would we refer to the peritubular capillaries as the vasa recta?
In the renal medulla (Vasa Recta)
* Typically see this in juxtamedullary nephrons where the vasa recta is long and goes all the way down to the level of the renal medulla
What does the pertibular capillary and vasa recta do that are the same but not in the same location?
They both provide nutrients but peritubular capillary is in the cortex region while the vasa recta is in the medulla region of the nephron
