HUMB1000 Study Guide - Final Guide: Distal Convoluted Tubule, Simple Squamous Epithelium, Renal Physiology
10 Jun 2018
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Renal system
• Function:
• Excretion
• Regulate blood volume and blood pressure
• Solute conc. in the blood, extracellular pH, red blood synthesis, Vitamin D synthesis
• Urine production
• Filtration
➢ Filtration occurs in the renal corpuscle, which consists of the glomerulus and
Bowman’s capsule. Blood enters the glomerulus, and the fluid and solutes in the blood
are pushed through the glomerular capillary wall and enter the Bowman’s capsule,
which is the first part of the tubule. This solution is now called filtrate and a small
amount of it will eventually become urine.
➢ Substances: Water, glucose, fructose, amino acids, urea, urate ions, creatinine, Na+,
K+, Ca+2, Cl-
• Tubular reabsorption
➢ Reabsorption is the return of water and solutes to the blood following filtration. The
filtrate flows through the proximal convoluted tubules, loop of Henle, distal
convoluted tubules and then to the collecting ducts. As the filtrate moves through
the nephron, much of it is reabsorbed from the nephron to the blood stream via
processes such as diffusion, facilitated diffusion, active transport, symport and
osmosis.
➢ Solutes reabsorbed from the nephron to the blood include amino acids, glucose,
fructose and ions (e.g. K+, Na+, Cl- and Ca2+). As solutes are re-absorbed, water
follows the solutes via osmosis. The small volume of filtrate left after this
reabsorption contains urea, uric acid, creatinine, K+ and other substances.
1. Movement of the filtrate into the cells lining the nephron through the apical surface
of the cell or the apical membrane.
2. Then from these cells into the blood through the basal surface of the cell or basal
membrane.
➢ Loop of Henle
❖ simple squamous epithelium
❖ Further reabsorption of water and some solutes
➢ Distal convoluted tubule & Collecting duct
❖ Antidiuretic Hormone (ADH): Increase permeability of distal convoluted tubule
and collecting duct to reabsorb water
❖ Aldosterone: Causes Na+/K+ pumps to operate on the ascending loop of Henle. Na+
is pumped into the area adjacent to the collecting duct
• Tubular secretion
➢ Occurs in the DCT
➢ Tubular secretion is when substances are secreted into the filtrate from the blood.
Tubular secretion can be active or passive. A good example of tubular secretion is H+
ions, and this plays an important role in the regulation of the pH of the blood.
• Urine
• 1% of filtrate
• Substances: Urea, uric acid, ammonia, creatinine, H+, K+, Bile pigments
• Urethral reflexes & micturition Reflex
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