Sec 3 Biology Excretion in Humans topical questions

Define excretion and name the organ that excretes carbon dioxide.

Name the tube that carries urine from the bladder out of the body, and the tubes that carry urine from the kidneys to the bladder.

Name the process by which fluid is forced from the glomerulus into the Bowman’s capsule, and state what drives it.

State two substances that are selectively reabsorbed from the filtrate.

Name the waste product removed by the kidneys in urine, and state which organ manufactures it.

Explain why ultrafiltration is not described as "selective", while reabsorption is.

Explain why the urine of a healthy person contains no glucose, and why glucose might appear in the urine of a person with diabetes.

The kidneys filter 180 dm³ of plasma per day but produce only 1.5 dm³ of urine. Calculate the volume of filtrate reabsorbed per day and express it as a percentage of the filtrate.

Plasma contains about 0.3 g/dm³ of urea while urine contains about 20 g/dm³. Explain why the urea concentration increases so much.

Describe the complete journey of a urea molecule from its formation to the outside of the body.

A dialysis patient’s blood urea falls from 2.4 g/dm³ to 0.8 g/dm³ during a 5-hour session. Calculate the percentage decrease and the mean rate of decrease per hour.

Explain why a patient with kidney failure is often advised to limit the protein in their diet.

Describe how a dialysis machine removes urea from a kidney-failure patient’s blood, and explain the importance of the glucose and salt concentrations in the dialysis fluid.

During a 4-hour dialysis session a patient’s blood urea falls from 1.8 g/dm³ to 0.6 g/dm³. Calculate the percentage decrease and the mean rate of decrease, and explain why the urea level never falls to zero during the session.

Explain why neither red blood cells nor plasma proteins are found in the glomerular filtrate of a healthy person, and state what their presence in urine would indicate.

A patient with total kidney failure is kept alive by regular dialysis. Explain, in terms of diffusion gradients, why each session must last several hours and why the treatment must then be repeated for life.

A doctor tests the urine of two patients. Patient P’s urine contains glucose but no protein; patient Q’s contains protein but no glucose. Explain what each result suggests about what is going wrong in each patient’s kidneys.

Blood flows through both kidneys at 1.2 dm³ per minute. (a) Calculate the volume of blood passing through the kidneys in one day. (b) An adult’s total blood volume is about 5 dm³. State how many times the whole blood supply passes through the kidneys per day, and what this means for blood cleaning.