Physiology 3120 Lecture Notes - Lecture 37: Renal Pelvis, Urinary Tract Infection, Renal Vein
15 May 2018
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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
drinking
- 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
glucose
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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