Lecture 17- Kidney Physiology

Question 1

What makes up the urinary system?

Answer 1

2 kidneys, 2 ureters and bladder

Question 2

What protects the kidneys?

Answer 2

ribs

Question 3

How are the kidneys protected?

Answer 3

by the dorsal and ribs fused to the body wall

Question 4

What is the cardiac output of the kidneys?

Answer 4

they filter 1.2 litres a minutes and recieve 25% of the blood

Question 5

What is the kidney cortex made up of?

Answer 5

Cortex (outer pale layer) and the medulla
(pinky central area) contain nephrons. Highly perfused by blood vessels

Question 6

What is the hilum?

Answer 6

: entry/exit of blood vessels, veins
and ureter

Question 7

What are the nephrons and what are their characteristics?

Answer 7

Nephrons are the functional units, they are a
complex tubular structure that enables the
refinement of the filtrate, which will
eventually be excreted, based on what
components the blood needs.

Question 8

What are the key parts of the kidneys?

Answer 8

3 main areas:
* Renal Corpuscle (Bowman‘s capsule& Glomerulus)
* Renal Tubule (filtrate)
* Collecting Duct

Question 9

What is the difference in the functioning of the 2 nephrons?

Answer 9

*Two different kinds of nephrons:
* Cortical - deliver nutrients to the epithelial cells.

• Juxtamedullary – serve as osmotic exchangers for the production of
  concentrated urine

Question 10

Draw the structure of the nephron

Question 11

How does blood travel through the nephron?

Answer 11

Fluid moves:
* through the barrier
of the Glomerulus
into Bowman‘s
capsule
* down the proximal
tubule
* down the loop of
henle
* In the distal tubule
* In the collecting duct
* out the renal vein

Question 12

How does fluid travel through the nephron?

Answer 12

Fluid moves:
* through the barrier
of the Glomerulus
into Bowman‘s
capsule
* down the proximal
tubule
* down the loop of
henle
* In the distal tubule
* In the collecting duct
* out the renal vein

Question 13

What is the renal corpuscle?

Answer 13

Sieve function

Movement back in circulation

Specific particles: big/charged Removed out of body

Question 14

What is the renal tubule?

Answer 14

The renal tubule is involved in the reabsorption and secretion of various substances

Question 15

What is the collecting duct?

Answer 15

The collecting duct receives filtrate from multiple nephrons and carries it towards the renal pelvis for excretion as urine.
It is lined with both principal cells and intercalated cells, which are involved in the reabsorption of water and electrolytes, as well as the secretion of potassium, hydrogen ions, and ammonia.
The collecting duct plays a crucial role in the final concentration or dilution of urine, depending on the body’s hydration status.

secretion and reabsorption occurs here

Question 16

Where do filtration, reabsorption, secretion and excretion occur?

Answer 16

Filtration is the selection of blood components only based on size
(like a sieve)

Reabsorption is the movement of ions, flowed by water, back into the
capillaries from the lumen of the nephron. Greatest amount happens
in the proximal convoluted tubule. This process is much more
important than secretion for most (but not all) substances (in terms of
determining excretion rate).

Secretion is movement of molecules from the blood into the lumen of the nephron, more selective than filtration.

Excretion is the removal of urine from the body.

Question 17

Summarise the nephron

Answer 17

• The functional unit of the kidney.
• Responsible for blood processing.
• Change in the types of cells along the length of the nephron to
  enable it to perform its function.
• 3 main areas:
• Renal Corpuscle (Bowman‘s capsule& Glomerulus)
• Renal Tubule (filtrate)
• Collecting Duct
• Two different kinds of nephrons:
• Cortical - deliver nutrients to the epithelial cells.
• Juxtamedullary – serve as osmotic exchangers for the production of
  concentrated urine.

Question 18

What are the different processes occurring in the nephron and at what rates?

Answer 18

Filtration is the selection of blood components only based on size
(like a sieve)

Reabsorption is the movement of ions, flowed by water, back into the
capillaries from the lumen of the nephron. Greatest amount happens
in the proximal convoluted tubule. This process is much more
important than secretion for most (but not all) substances (in terms of
determining excretion rate).

Secretion is movement of molecules from the blood into the lumen of the nephron, more selective than filtration.

Excretion is the removal of urine from the body.

Question 19

What is the glomerular filtration process?

Answer 19

Glomerular filtration is the process by which blood is filtered across
the capillaries of the glomerulus and into Bowmans Capsule.
▶ The movement of fluid from the vascular space to Bowmans Capsule is
also known as ultrafiltration and the fluid us known as ultrafiltrate.
▶ The ‘ultrafiltrate’ fluid has a similar
composition to plasma (isotonic) but
with no protein/cells.
▶ The filtration barrier restricts movement
of solutes on a basis of size and charge

Question 20

Why are podocytes important?

Answer 20

▶ Podocytes: finger-like projections on
glomerulus

Question 21

What is ultrafiltration and what are the properties of the ultrafiltrate?

Answer 21

ultrafiltration in the kidneys refers to the selective removal of water, electrolytes, and small solutes from the bloodstream in the renal corpuscles, forming the glomerular filtrate that enters the renal tubules for further processing and urine formation

▶ Small molecules < 1.8 nm freely filtered; >3.6 nm not filtered.
▶ Cations are more readily filtered than anions with the same
molecular radius.
▶ Albumin has a radius of ~3.5 nm (LIMIT), but its negative charge
prevents filtration.
▶ In many diseases the negative charge on the filtration barrier is
lost so that proteins (e.g. albumine) are more readily filtered and
appear in the urine, known as proteinuria

Question 22

What does a filtration barrier restrict?

Answer 22

The filtration barrier restricts movement
of solutes on a basis of size and charge.

Question 23

What are the pedicels of the bowmans capsule?

Answer 23

▶ Podocytes: finger-like projections on
glomerulus

Question 24

Draw the structure of the membrane at Bowman’s capsule

Question 25

What are the limits of ultrafiltration?

Answer 25

▶ Small molecules < 1.8 nm freely filtered; >3.6 nm not filtered.
▶ Cations are more readily filtered than anions with the same
molecular radius.
▶ Albumin has a radius of ~3.5 nm (LIMIT), but its negative charge
prevents filtration.
▶ In many diseases the negative charge on the filtration barrier is
lost so that proteins (e.g. albumine) are more readily filtered and
appear in the urine, known as proteinuria

Question 26

What is the glomerular filtration rate and what are its units?

Answer 26

The rate of filtration
is called Glomerular
Filtration Rate (GFR)

Question 27

Write the order of the glomerular filtration and where it occurs, where the plasma moves

Answer 27

Occurs at the Renal Corpuscle, where plasma moves from the blood vessels of
the glomerulus into the lumen of Bowmans Capsule.

 20% plasma moves into Bowmans Capsule, most of this is reabsorbed further
along the nephron. (no proteins)

 80% proceeds to the vasa recta where secretion of desired solutes into the
nephron lumen occurs, ready for excretion.

Question 28

What is the GFR of a normal adult?

Answer 28

GFR
125 ml/min

Question 29

What can influence the GFR?

Answer 29

It is influenced by antidiuretics like coffee and alcohol or drugs and illness

GFR is influenced by a complex interplay of factors, including renal blood flow, systemic blood pressure, hormonal regulation, intrarenal mechanisms, and pathological conditions

Question 30

What factors control the GFR?

Answer 30

Generally, Glomerular Filtration Rate (GFR) is relatively constant.
* GFR is controlled by 2 factors:
* Net filtration
* Changes in renal blood flow and blood pressure
* Filtration Coefficient
* Changes in diameter of the afferent and efferent arterioles to alter the GFR
* Governed by surface area of glomerular capillaries (podocyte changes)

Question 31

What factors affect net filtration?

Answer 31

▶ Glomerular Filtration Rate (GFR) is the volume
of plasma from which a given substance is
removed by glomerular filtration
▶ 20% plasma moves into Bowmans
space, this is dependent upon:
1. Hydrostatic pressure (from glomerulus and
backwards from Bowman‘s capsule)
2. Colloid osmotic pressure (presence of
proteins in blood draws water)
3. Hydrostatic fluid pressure (membrane
opposes pressure)

Question 32

How does the structure of the podocytes affect the filtration coefficient?

Answer 32

they contain pedicils which can change in size that and control the amount of permeability by exposing more or less of the basement membrane which is permeable

Question 33

how is GFR calculated?

Answer 33

25% of your cardiac output goes to the kidneys
- of this blood the afferent arteriole attains 750ml/min of blood and 20% of this is the GFR which is 125ml/min