PACK 23b: HOMEOSTASIS OSMOREGULATION Flashcards
(31 cards)
What are the two main functions of the kidneys?
Excretion and osmoregulation
Excretion involves the filtration of blood to remove urea, while osmoregulation maintains constant blood water potential.
Where are the kidneys located in the body?
In the abdominal cavity.
What is the role of the renal arteries?
They supply blood to the kidneys from the aorta.
What is the function of the renal veins?
They return blood from the kidneys to the vena cava.
What are the three main regions of the kidney?
- Cortex
- Medulla
- Pelvis
What is the nephron?
A functional unit of the kidney, composed of about one million fine tubules.
What is the primary function of the Bowman’s capsule?
Ultrafiltration, containing a glomerulus.
What occurs in the proximal convoluted tubule?
Selective reabsorption.
What is the role of the Loop of Henle?
To produce a Na+ concentration gradient in the interstitial fluid of the medulla.
What is the function of the collecting duct?
To collect urine from several nephrons and transport it to the pelvis of the kidney.
What type of cells line the Bowman’s capsule?
Podocytes.
What is the significance of the filtration slits in podocytes?
They allow small molecules to pass while blocking larger ones like red blood cells and plasma proteins.
What creates high hydrostatic pressure in the glomerulus?
The wider afferent arteriole compared to the efferent arteriole.
What components are typically not found in the filtrate?
Red blood cells, platelets, plasma proteins.
List four substances found in the filtrate.
- Water
- Glucose
- Amino acids
- Sodium ions
- Urea
What percentage of filtered glucose is reabsorbed in a healthy individual?
99.9%.
Why is glucose almost entirely reabsorbed?
It is a valuable respiratory substrate.
What is the main function of microvilli in the proximal convoluted tubule cells?
To maximize surface area for reabsorption.
What role do mitochondria play in proximal convoluted tubule cells?
They provide ATP needed for active transport.
What is cotransport in the context of glucose reabsorption?
The simultaneous transport of glucose and sodium ions into PCT cells.
Describe the countercurrent multiplier mechanism of the Loop of Henle.
Fluid flows in opposite directions in the loop, creating a Na+ gradient that enables water reabsorption.
What happens to the concentration of filtrate in the descending limb of the Loop of Henle?
It increases as water is lost by osmosis.
What is the effect of ADH on the collecting duct?
It increases the permeability to water.
What happens when ADH levels decrease?
Aquaporins are removed, making the collecting duct less permeable.
