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Lecture 37

Physiology 3120 Lecture Notes - Lecture 37: Renal Pelvis, Urinary Tract Infection, Renal Vein

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Tom Stavraky

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Lecture 37 Renal Physiology
- Different colours for urine are possible
o Pink urine: eat a lot of beets, urinary tract infection (medical condition where
urinary tract gets infected and causes there to be a little bit of blood)
o Brown urine: anti-malarial drugs (hemolytic break down RBCs), muscle-waste
diseases muscles start to break down inappropriately pigment produced makes
the urine look brown
Overview of kidney function
- Urine:
o Produced by the kidneys
o Tells you a lot about the health of an individual
- Regulation of Ionic Composition of Blood
o Kidney filters blood, process the filtered product and measures all of the ions
o Kidney makes decisions about how many ions stay in the body (reabsorbed) and
what needs to be excreted in the urine product produced
o E.g. eat excess sodium = increased sodium in the urine
o If ingest excess ions, kidneys regulate ion levels so the blood composition is correct
o Urine is the product of ion balancing
- Regulation of Blood pH
o Proteins fold in certain conformations depending on pH
o If pH increases or decreases too much, proteins start to unfold and do not function
o Most proteins function as enzymes = don’t want proteins falling apart
o Lungs do a better and quicker job at regulating blood pH
- Regulation of Blood Volume
o More blood volume = heart has to work harder
o Less blood volume = heart has to make up for the low level of blood
o Kidneys work with the heart to make sure the blood volume is appropriate
o If have a higher blood volume, kidney compensates and excretes a larger volume of
urine so heart doesn’t have an excess job to do of dealing with a higher volume
o Low blood volume = produce lower volume of urine and behavioral response of
- Regulation of Blood Pressure
o High blood volume = high blood pressure (they are closely linked)
o Kidneys work closely with the heart to maintain blood pressure
o Kidneys respond to pressure receptors (baroreceptors) and volume receptors and
adapt how it filters and processes the filtered product
- Maintenance of Blood Osmolarity (300 mOsm/kg)
o If it changes, cells either gain or lose water = swelling or shriveling of cells
o Osmolarity: ALL of the solutes dissolved in blood (not just ions)
Water volume (main component of blood) + glucose + amino acids, etc.
- Production of Hormones
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o Kidneys are also endocrine glands
o E.g. Erythropoietin (EPO), activated Vitamin D (Calcitrol)
EPO: stimulates RBC production must always make RBCs because RBCs are
continuously replaced
Activated Vitamin D: functions as a steroid hormone in the body (binds to
intracellular receptor to change gene expression)
Kidneys take vitamin D that exists in the body and convert it to the active
form (calcitrol)
Vitamin D is obtained from the sun (vitamin D3) or by eating fortified
products or healthy greens (vitamin D2) either are activated when they
get into blood and pass by the kidneys
Kidneys are important for the activation of vitamin D
- Regulation of Blood Glucose Levels
o If you were to not eat any carbohydrates, kidneys convert proteins and fats into
o Gluconeogensis: producing glucose from non-glucose sources (non-carbohydrate)
because glucose must be in the blood
o Brain is an organ that requires glucose
o Kidneys ensure that there is sufficient levels of glucose floating around for the brain
- Excretion of Wastes and Foreign Substances in the urine
o Waste products are made metabolically and foreign substances need to be excreted
o E.g. metabolic waste products: urea (break down of amino acids), Uric acid
(nucleotides), Creatinine (waste product of the break down of creatine high
energy carrier in skeletal muscle), Urobilin (break down of hemoglobin from RBCs)
Kidney anatomy
- Have two kidneys but one is sufficient to function on (but need at least one)
o If have two kidneys you can be a donor but not if you only have one
- Cortex: outside layer
o Looks granular microscopically
o This is because there is a component of the nephron that sits in the cortex
- Medulla: inner layer that looks striated
o Nephron: functional part of the kidney is contained within the medulla
o Structure of the nephron is responsible for the striations
o Medulla has a very high osmolarity
o Closer to the middle of the kidney you travel, the higher the interstitial fluid
osmolarity is (more concentrated)
- Renal pelvis: hollow segment where fluid collects
o When kidney filters blood and produces urine, the urine products collects in the
middle of the kidney in the renal pelvis
o When body has decided it is excreting the fluid, it is called urine and it is no longer
modifiable and collects in the central, hollow region
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- To collect the urine that is being produced as blood is being filtered into the tissue sections
of the kidney, there are funnel-like structures called calyces
- Calyces: little pyramidal cones sitting at the bottom of the medulla
o Medulla radiates outwards and each of the most central parts of the medulla are
collecting cups
o Collects filtered products and puts it in the center of the kidney (renal pelvis)
- Ureter: tube structure where urine kidney exits the body
o 2 kidneys = 2 ureters collect in the bladder
o From the bladder, the urethra brings the urine out of the body
- A lot of blood needs to be supplied to the kidney because the kidney filters blood
o To filter a lot of blood, there must be a big blood vessel bringing blood to the kidney
- Renal artery: how blood enters the kidney
- Renal vein: how blood exits the kidney
Kidney blood supply
- How much blood gets devoted to the kidney?
- Liver and the kidney have the most blood flow (mL/min) but the liver gets the most
- Liver gets a lot of blood because it is a filter
o Liver is a detoxer
o Liver takes blood, filters it, metabolizes and breaks down the materials, modifies it
o Liver needs a lot of the blood because it deals with the composition of the blood
(like the kidney)
- Based on size, the kidney gets a lot more blood compared to the liver
o Body has made a decision that the kidney needs a lot of blood
o Kidneys are very small but a lot of blood is still devoted there
o Kidney receives a lot of blood because the kidneys need to filter the blood (pH, ions)
o High volume of blood goes to the kidneys not an error on the body’s part
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