1
Q
what are the kidneys controlled by?
A
both neural and endocrine inputs
2
Q
primary function of the kidneys
A
maintain the ECF volume, electrolyte composition, and osmolarity
3
Q
what happens in the presence of excess water or of a particular electrolyte (solute)
A
kidneys can fix this by getting rid of the extra amount in urine (increase their elimination)
4
Q
what happens when there is a deficit of water or of a solute (3)
A
- the kidneys cannot create more of it.
- They cannot actively add water or electrolytes back into the body
- What they can do is reduce how much they lose in urine (reduce their elimination)
5
Q
10 major functions of the kidneys
A
- Maintain water balance in the body
- Maintain body fluid osmolarity
- Maintain proper plasma volume
- Help maintain acid-base balance
- Regulate ECF solutes (such as sodium, potassium, chloride, calcium, phosphate, and others)
- Excrete wastes of metabolism
- Excrete foreign compounds ingested
- Produce erythropoietin
- Produce renin
- Activate vitamin D
6
Q
kidney shape 4
A
- The kidneys are bean-shaped organs, each about 10 cm in length
- Associated with each kidney is an adrenal gland, which is situated on top of the kidney.
- The outside of the kidney is the renal cortex and
the inner part is called the renal medulla. - At the inner core of each kidney is the renal pelvis
7
Q
renal pelvis
A
through which the urine empties and is channeled to the ureter.
8
Q
nephron (3)
A
- The functional unit of the kidney
- there are more than one million in a healthy
adult kidney. - It is within the nephrons that blood is filtered to produce urine and the reabsorption of
necessary fluids and molecules occurs
9
Q
2 components of the nephron + brief description (2)
A
- the vascular component, which supplies blood to the nephron.
- the tubular component, which carries the filtrate throughout the nephron.
10
Q
the vascular component (5)
A
- The major part of the vascular component of the nephron is the glomerulus, which is a ball-like
capillary through which water and solutes are filtered from the plasma. - When blood enters the kidney via the renal artery, the renal artery subdivides into many small afferent arterioles, each of which
supplies a nephron. - Leaving the nephron are the efferent arterioles, which transport unfiltered blood from the glomerulus.
- The capillaries of the nephron are different in that arterial blood enters and then leaves, with no
oxygen extracted. - Instead, the efferent arteries subdivide into capillaries, the peritubular capillaries, that deliver oxygen to the renal tissues.
11
Q
the tubular component (2)
A
- Filtered blood enters a hollow tube, formed by a single layer of epithelial cells, that transports urine to the renal pelvis.
- Even though it is technically one long continuous tube, it is divided along its length
based on differences in structure and function.
12
Q
flow through the tubular component (7)
A
- It begins with Bowman’s capsule, which encircles the glomerulus to collect the fluid filtered from the
glomerular capillaries. - Fluid then passes into the proximal tubule within the renal cortex, which is
highly coiled along its length. - Next is the loop of Henle, which forms a hairpin loop that dips down into
the renal medulla. - The descending limb of the loop of Henle travels from the cortex to the medulla
while the ascending limb travels from the medulla back to the cortex. - The ascending limb passes
through the fork of the afferent and efferent arteries in a region called the juxtaglomerular apparatus. - The tubule now coils again and is called the distal tubule, also entirely within the cortex.
- The distal tubule empties into a collecting duct, which travels deep into the medulla and ultimately drains into the renal pelvis
13
Q
2 types of nephrons
A
- Cortical Nephrons
- Juxtamedullary Nephrons
14
Q
Cortical Nephrons (4)
A
- The glomeruli of this type of nephron lie in the outer layer of the cortex.
- About 80% of all nephrons are cortical nephrons that primarily serve secretory and regulatory functions.
- Their loop of Henle only
slightly dips into the renal medulla. - The peritubular capillaries from this type of nephron wrap around the short loops of Henle.
15
Q
Juxtamedullary Nephrons (2)
A
- This type of nephron is found on the inner layer of the cortex and are responsible for the
concentration and dilution of urine. - The peritubular capillaries from these nephrons form hairpin loops of vasculature, called the vasa recta, that are in close proximity to the long loops of Henle.
16
Q
3 basic processes of the kidneys when it comes to the formation of urine
A
- Glomerular Filtration (GF)
- Tubular Reabsorption (TR)
- Tubular Secretion (TS)
17
Q
Glomerular Filtration (GF) (3)
A
- About 20% of the blood that flows through the glomerular capillaries is filtered into Bowman’s capsule.
- It is important to note that this plasma filtrate is normally protein free, but does contain the same
solutes as the plasma. - Collectively, about 125 ml of glomerular filtrate is formed each minute.
18
Q
Tubular Reabsorption (TR) (2)
A
- As the filtrate flows through the tubules, important substances are returned to the peritubular
capillaries by the process of tubular reabsorption. - Of the 180 litres of plasma filtered each day, about
178.5 is reabsorbed.
19
Q
Tubular Secretion (TS) (3)
A
- This is the second route for substances in the blood to enter the renal tubules.
- Tubular secretion is the
selective transfer of substances from the peritubular capillaries into the tubules. - Remember, only 20%
of the plasma is filtered in the glomeruli so this route allows excretion of selected substances from the
remaining 80% of the plasma.
