Physiology 2 Flashcards
What foreign compounds do the kidneys excrete
Drugs and their metabolites
food additives
pesticides
What metabolic waste do the kidneys excrete
Urea, bilirubin and uric acid
What is bilirubin a byproduct of
Haemoglobin
What is uric acid a byproduct of
purine metabolism
What is urea a byproduct of
protein metabolism
Why can we never completely turn of urine production
we have to get rid of some metabolic wastes in the solution
What does renin do
control the renin-angiotensin system and controls arterial blood pressure
What do we do in response to hypoxia
Increase the secretion of erythropoietin to bring about more RBC production
Why do we need calcitriol
To stimulate calcium absorption in the GI tract
How is vitamin D converted into Calcitriol
The OH group added by either the liver or by cells in the kidney
What is the primary function o the kidney
to regulate the volume, composition and osmolarity of the body fluids
How do we maintain homeostasis in the body
Input = Output
What is the major loss of water from the body
Urine
Where are the kidneys located
Between T12 and L3
What helps the smooth muscle of the ureter to propel urine for the kidney down to the bladder
Peristalsis
What does the urinary bladder act as
A temporary store vessel for urine until there is an appropriate time to expel the urine
What is the renal medulla made up of
several renal pyramids
What appearance does the renal cortex have
granulated appearance
How much do the kidneys receive of the cardiac output
20-25%
What appearance does the renal medulla have
Striped or striated
What is a nephron
The functional unit of the kidney
How many nephrons does each kidney have
about 1 million
What are the 3 functional mechanisms of the nephron
filtration
reabsorption
secretion
What does the filtration form
the initial tubular fluid at the start of the nephron
What does the tubular fluid lack compared to the plasma
The large plasma proteins and red blood cells
Describe the vascular supply to the nephron
Initially an afferent arteriole which subdivides into a glomerulus (tuft) which then drains back into an efferent arteriole
Unique to anywhere else in the body
Where does the blood go after passing through the peritubular capillaries
Renal vein
What is the tubular component of the nephrons made up
single epithelial cell wall
What happens between the glomerulus and the Bowman’s capsule
Glomerular filtration
What is the loop of Henle made up of
descending and then ascending limbs
How can the tubular fluid be modified
Through reabsorption and secretion of molecules into the tubules
What happens when the tubular fluid leaves the collecting duct and why
It is then called urine and no further modification can occur here
What are the 2 different types of nephrons in the kidney
Cortical (most common)
Juxtamedullary (20%)
What are the 2 main differences between the Cortical and juxtamedullary nephrons
Juxtamedullary have a very long loop of Henle
and they have a single network of capillaries (Vasa recta) whereas the cortical nephron have peritubular capillaries
What causes the renal medulla to have the striated appearance
Loads of Nephrons in particular the loop of Henles
What do the Juxtamedullary nephrons allow us to do
Produce a concentrated urine
Why is the desert rat able to produce more concentrated urine than us as humans
They have more juxtamedullary nephrons than we do
What does the concentration or relaxation in the afferent arteriole do
Determines how much blood will flow into the glomerular capillary
What cells make up the inner layer of the Bowman’s capsule
Podocytes
What do the foot-like processes of the podocytes do
They interdigitate with the neighbouring cells forming slits for filtration
How much of the plasma that flows through the capillaries ends up forming the tubular fluid
around 20%
What is the difference in composition of the tubular fluid and the plasma
Tubular fluid is identical other than lacking large plasma protein and RBCs
What is formed between the podocytes and the epithelial cells
Basement membrane (an acellular layer)
Where does glomerular filtration occur
across the glomerular membrane
What happens in the juxtaglomerular apparatus
The distal tubule passes through the fork that is formed between the afferent and efferent arterioles
What do the granular cells (modified vascular cells) do
The produce and secrete renin
What are the specialised tubular cells also known as
Macula densa
What does the macula densa do
they sense the amount of salt in the tubular fluid as it passes through the region of the nephron
What can urine be thought of as being
modified filtrate of the blood
In order to produce urine, what must the kidneys incorporate
filtration system
rich blood supply
mechanisms for urine modification (tubular reabsorption and secretion)
What renal processes occur in the production of urine
glomerular filtration
tubular reabsorption
tubular secretion
What happens to the majority of the plasma that enters the glomerulus ?
it is not filtered and leaves through the efferent arteriole
How can we calculate the rate of excretion of a particular substance
Rate of filtration + rate of secretion - rate of reabsorption
What is the rate of filtration equal to
The concentration of the substance in the plasma x Glomerular filtration rate
What is GFR for a healthy adult at rest
125ml/min and kept relatively constant
What happens if we increase the concentration of the substance in the plasma
The rate at which the kidneys filter the substance will increase as GFR is constant
How can we calculate the rate of excretion of a substance
The concentration of the substance in urine x urine flow rate
What does the rate of excretion depend on
The hydration status of the body
What happens if the rate of filtration is greater than the rate of excretion
The kidneys are filtering more than what is being excreted - more reabsorption
If the rate of filtration is less than the rate of excretion, what has happened to the net secretion
Net secretion of that substance has occurred
What is important to do to the GFR when calculating the rate of filtration
convert it from ml/min to litres / min so that the units are consistent
