Welcome to The Juxtaglomerular Apparatus.
The juxtaglomerular [JG] apparatus is a structure in the kidneys.
It’s a specialized region of a nephron where the afferent arteriole and the
distal convoluted tubule [DCT] come into direct contact with each other.
The JG apparatus as a whole works to regulate filtrate formation
and systemic blood pressure.
In this diagram we can see the: Efferent arteriole, Afferent
arteriole, DCT, Glomerulus, and Proximal convoluted tubule.
The specialized cells of the afferent arteriole at this region are
called juxtaglomerular [JG] cells.
These cells contain the enzyme renin and function as mechanoreceptors
to sense blood pressure.
Let’s zoom in to see the JG cells up close.
The specialized cells of the DCT, at the point of contact with the afferent
arteriole, are the macula densa cells.
These cells function as chemoreceptors to sense changes in the solute concentration
and flow rate of the filtrate.
Here’s a close-up of the Macula densa cells.
Now let’s examine the functions of these cells using specific examples.
When systemic blood pressure decreases, there is a decreased
stretch of the JG cells, which leads to their release of renin.
Renin release causes the activation of the renin-angiotensin
mechanism, which ultimately leads to an increased blood pressure.
Now here’s another example
When filtrate has low osmolality or decreased flow rate, the macula
densa cells sense this, which leads to vasodilation of the
afferent arteriole and stimulation of the JG cells to release renin.
This will return filtrate flow rate and osmolality to normal.
And, in our last example
When filtrate has increased osmolality or increased flow rate,
the macula densa cells sense this, which leads to the vasoconstriction
of the afferent arteriole.
This will return osmolality and the flow rate of the filtrate to normal.
Review.
Let’s complete this sentence with the missing terms related
to the juxtaglomerular apparatus.
Juxtaglomerular cells function to act as blank receptors, whereas
macula densa act as blank receptors.
Juxtaglomerular cells function to act as mechano receptors, whereas
macula densa act as chemo receptors.
Let’s try another one
JG cells contain the enzyme blank.
JG cells contain the enzyme renin.
Here’s one more.
As a result of the increased osmolality of the filtrate, the macula densa will cause
the blank of the afferent arterioles.
As a result of the increased osmolality of the filtrate, the macula densa
will cause the vasoconstriction of the afferent arterioles.
In conclusion, the juxtaglomerular [JG] apparatus is a structure in the kidneys.
They regulate the function of each nephron.
The system as a whole regulates filtrate formation and systemic blood pressure.
Congratulations!
You have completed The Juxtaglomerular Apparatus video.