Albert was 12 years old when he began to experience symptoms that he felt were n

Question

Albert was 12 years old when he began to experience symptoms that he felt were not normal. He constantly felt thirsty and was drinking several liters of water a day. As well, he was frequently urinating, sometimes several times an hour. Albert was also losing weight despite the fact that he was eating more now than ever before. Finally he decided to talk to his parents who took him to his family physician where he was diagnosed with diabetes mellitus. As part of his diagnosis, it was noted that he had elevated plasma sodium concentrations and that his blood pressure was 90/55 when lying down and decreased to 75/45 when standing.

1. How is glucose normally filtered and reabsorbed?

2. At a normal plasma glucose concentration, how much glucose is reabsorbed?

Please discuss in detail.

Explanation / Answer

1. GLUCOSE FILTRATION AND REABSORBTION

Glucose that is present in the blood reaches the Bowman's Cpsule through the afferent artery. In the Bowman's capsule particles of size smaller than 1.8 nanometers are filtered. The filterate contains substances such as water, glucose, urea and salts. The glucose molecules are filtered through the Bowman's capsule because of the high hydrostatic pressure. This filterate now enters the proximal convoluted tubule where tubular reabsorbtion takes place. Glucose molecules are also reabsorbed from here and will be collected into the peritubular capillaries which are present surrounding the proximal convoluted tubule. The glucose molecules are reabsorbed by secondary active transport mechanism with the help of co-transporters present in the wall of proximal convoluted tubule. These co-transporters move both sodium and glucose out of the proximal convoluted tubule. The co transporters are powered by Sodium- potassium pump which maintains the concentration gradient and sodium ions help in driving glucose out of the proximal convoluted tubule to the peritubular capillaries.

2. At normal plasma glucose concentrations, almost 100 percent of glucose is reabsorbed i.e approximately 180g of glucose each day. the glucose transporters that are present in the proximal convoluted tubule ensure that less than 1% {approxx. 0.5g/day (0.03-0.3 g/d) } is excreted through urine. During reabsorbtion, water is reabsorbed more than glucose there by increasing the glucose concentration in the proximal convoluted tubule. This increased concentration of glucose increases the affinity of the transporters to glucose molecules which would result in the complete reabsorbtion of glucose.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.