Kidneys - BP & Homeostasis Flashcards
What are the main roles of the kidney?
HOMEOSTASIS
Your kidneys remove wastes and extra fluid from your body. Your kidneys also remove acid that is produced by the cells of your body and maintain a healthy balance of water, salts, and minerals—such as sodium, calcium, phosphorus, and potassium—in your blood.
Without this balance, nerves, muscles, and other tissues in your body may not work normally.
Your kidneys also make hormones that help:
- control your blood pressure
- make red blood cells
- keep your bones strong and healthy
What is the main functional unit of the kidney?
Millions of nephrons.
What are the stages of blood processing in the nephron?
Each nephron includes a filter, called the glomerulus, and a tubule.
The nephrons work through a two-step process: the glomerulus filters your blood, and the tubule returns needed substances to your blood and removes wastes.
Explain glomerular filtration (GF)
The glomerulus is a network of capillaries. Blood enters the glomerulus via the afferent arteriole (And exits via the efferent arteriole).
The capillary endothelium of the glomerulus is porous = allows smaller molecules, waste products (such as ions, glucose and amino acids), and fluid—mostly water—to pass into the tubule.
Larger molecules, such as proteins and blood cells, stay in the blood vessel.
The filtered components are known as filtrate - enter the tubule.
What occurs in the tubule?
Reabsorption and Secretion
A blood vessel (a branch capillaries from the efferent arteriole) runs alongside the tubule.
As the filtrate moves along the tubule, the blood vessel reabsorbs almost all of the water, along with minerals and nutrients your body needs.
Waste products, such as excess hydrogen, potassium and organic acid, in the blood vessel are forced into the tubule via active transport (aka secretion).
The remaining fluid and wastes in the tubule become urine.
Name the parts of the tubule
Proximal convoluted tubule (PCT)
Loop of Henle
- Descending loop
- Ascending loop
Distal convoluted tubule (DCT)
Collecting duct
What occurs at the proximal convoluted tubule (PCT)
- Filtrate enters the PCT from Bowmans capsule
- PCT structure is designed to maximise re-absorption
- Most ions & water are re-absorbed into the surrounding blood vessel through
The remaining filtrate enters the Loop of Henle.
What occurs at the loop of henle
The loop of Henle is in an area of the kidney called the Medulla. The medulla is highly salty.
The loop of Henle has two parts:
- Descending loop
- Ascending loop
Filtrate firstly enters the descending loop. The descending loop is permeable to water, not to ions. Because the medulla is highly salty, the remaining water in the filtrate is re-absorbed.
The filtrate then enters the ascending loop. The ascending loop is NOT permeable to water.
In this section Ions (NaCl - SALT) are actively pumped into the medulla (making it highly salty).
The remaining filtrate is now URINE. It enters the distal convoluted tubule.
What occurs in the Distal convoluted tubule (DCT) & Collecting duct?
Final adjustments to the filtrate are made.
Urea is reabsorbed into the medulla to make it saltier = maintain concentration gradient to draw water out in the descending loop of henle
