Tubular Reabsorption Essay

Name: Sarah Trudel Student Number: 5973771

1.Describe the process of water, nutrient and electrolyte reabsorption in the nephron of the kidney. In your answer, make sure to address the following questions: (11 marks total)

a) What molecules are reabsorbed in each tubular element of the nephron? (7 marks)

Tubular reabsorption is the process of reclaiming water and solutes from the tubular fluid and returning them to the blood (Saladin, 2004). The first part of the nephron that is involved in the tubular reabsorption is the proximal convoluted tubule (PCT) (Silverthorn et al., 2013). Once the glomerular filtrate reaches the PCT, the following molecules are reabsorbed: Water (H2O), Sodium chloride (NaCl), bicarbonate ions (HCO3-), Calcium

In your answer, make sure to address the following questions: (17 marks total)

a) Where is antidiuretic hormone (ADH) synthesized and where is it secreted? What is the primary stimulus for the secretion of ADH? Where does this hormone act? What effect does ADH have on the osmolarity of the renal filtrate? What is the specific mechanism responsible for producing this effect (Be specific)? (6 marks)

The antidiuretic hormone (ADH) is synthesized by neurons located in the hypothalamus and are stored in and secreted by the posterior pituitary gland (Silverthorn et al., 2013). The high osmolarity of a dehydrated person is the primary stimulus for the secretion of ADH (Saladin, 2004). This hormone acts on the collecting duct of the nephron (Silverthorn et al., 2013). ADH increases and water reabsorption and decreases osmolarity of renal filtrate (reduces urine output) by two mechanisms. (1) Within seconds, cells of the collecting duct transfer aquaporins from storage vesicles in the cytoplasm to the apical cell surface and cells begin to take up more water from the tubular fluid. (2) If the ADH level remains elevated for more than 24 hours, it induces the cell to transcribe the aquaporin gene and manufacture more aquaporins (water channels), further raising the water permeability of the collecting duct (Saladin,

What stimulates the production of this hormone? What effect does it have on the kidneys? (3 marks)

The atrial natriuretic peptide (ANP) hormone is produced in specialized myocardial cells primarily n the atria of the heart (Silverthorn et al., 2013). Natriuretic peptides are released by the heart when increased blood volume causes increased atrial stretch (Silverthorn et al., 2013). At the systemic level, ANP enhances sodium and water excretion to decrease blood volume. In the kidneys specifically, ANP increases glomerular filtration rate by dilating the afferent arterioles, and it directly decreases sodium reabsorption I the collecting duct (Silverthorn et al., 2013).