Proximal convoluted tube

Question 1

WHy does their need to be reaborbtion?

Answer 1

• ultrafiltration removes urea as well as other products needed by the body
• the ultrafiltrate is also hypotonic to the blood plasma
• gluocse is normally never excreted for example
• the main function of the nephron after the Bowman’s capsule is to return most of the filtered substance back to the blood

Question 2

What is reabsorbed in the proximal tubule?

Answer 2

all of the:

• glucose
• amino acids
• vitamins
• hormones

85% of water and sodium chloride is reabsorbed

Question 3

How does the proximal convoluted tubule reabsorb these substances?

Answer 3

• active transport
• although water and chloride ions follow passively down conc gradients

Question 4

What are the adaptations of the cells lining the proximal convoluted tubule?

Answer 4

• covered with microvilli
  
  • greatly increasing SA over which substances can be reabsorbed
• many mitochondria
  
  • provide the ATP needed in AT systems

Question 5

What happens once the filtrate leaves the proximal convoluted tube?

Answer 5

• removed by the extensive capillary network which surrounds the tubules down steep conc gradients
• maintained by the contrant flow of blood through the capillaries
• the filtrate reaching the loop of Henle at the end of the proximal convoluted tubule is isotonic with tissue fluid surrouding the tubule and isotonic with blood
• 80% pf the glomerular filtrate is reabsorbed - the same regardless of conditions