I/E: The Kidneys Flashcards
What are the main functions of the kidneys?
- Excrete waste products, eg. urea.
- Regulate the water potential of the blood.
Ultrafiltration
The process of blood passing through capillaries in the cortex (outer layer) of the kidneys and substances being filtered out and into long tubules surrounding capillaries.
Selective reabsorption
The process after ultrafiltration where useful substances, eg. glucose and the right amount of water, are reabsorbed back into the blood.
What happen to unwanted substances after selective reabsorption?
Pass to the bladder and are excreted as urine.
Nephrons
Long tubules along with bundles of capillaries where the blood is filtered in the kidneys.
Describe the process of ultrafiltration:
- Blood from renal artery enters arterioles in cortex of kidneys.
- Passes through afferent arteriole into the glomerulus.
- Passes into the efferent arteriole that has a higher pressure.
- Forces liquid and small molecules in blood out of the capillary.
- Pass through capillary wall, basement membrane and epithelium of Bowman’s capsule.
- Glomerulus filtrate passes from Bowman’s capsule along the rest of the nephron and useful substances are reabsorbed.
- Filtrate flows through collecting duct and passes out of kidneys along the ureter.
Glomerulus
Bundle of capillaries looped inside a hollow ball called a Bowman’s capsule.
Where ultrafiltration takes place.
Afferent arteriole
Arteriole that takes blood into each glomerulus.
Efferent arteriole
Arteriole that takes blood away from the glomerulus.
Glomerular filtrate
Substances that enter Bowman’s capsule.
The process of blood passing through capillaries in the cortex (outer layer) of the kidneys and substances being filtered out and into long tubules surrounding capillaries.
Ultrafiltration
The process after ultrafiltration where useful substances, eg. glucose and the right amount of water, are reabsorbed back into the blood.
Selective reabsorption
Long tubules along with bundles of capillaries where the blood is filtered in the kidneys.
Nephrons
Bundle of capillaries looped inside a hollow ball called a Bowman’s capsule.
Where ultrafiltration takes place.
Glomerulus
Arteriole that takes blood into each glomerulus.
Afferent arteriole
Arteriole that takes blood away from the glomerulus.
Efferent arteriole
Substances that enter Bowman’s capsule.
Glomerular filtrate
What is the difference between the afferent arteriole and efferent arteriole?
Efferent arteriole is smaller in diameter than the afferent arteriole, so the blood in the glomerulus is under high pressure.
What does the high pressure in the glomerulus do?
Forces liquid and small molecules in the blood out of the capillary and into the Bowman’s capsule.
The liquid and small molecules forced out of the blood pass through what three layers before entering the Bowman’s capsule?
Capillary wall
Basement membrane
Epithelium of Bowman’s capsule.
What type of molecules can’t pass through the layers to enter the Bowman’s capsule?
Larger molecules, eg. proteins and blood cells.
Label this diagram of the kidneys:
Label this diagram of the nephron:
When does selective reabsorption take place?
As glomerular filtrate flows along proximal convuluted tubule (PCT), through the loop of Henle, and along distal convoluted tubule (DCT).
Describe an adaption of the PCT for effective reabsorption:
Epithelium of the wall of PCT has microvilli = provides a large surface area.
Which processes are used to reabsorb useful solutes along the PCT?
Active transport and facilitated diffusion.
How does water enter the blood?
Through osmosis - water potential of blood is lower than that of the filtrate.
Where is water reabsorbed?
From the PCT, loop of Henle, DCT and collecting duct.
What is urine usually made of?
- Water and dissolved salts
- Urea
- Other substances, eg. hormones and excess vitamins.
What does urine usually not contain?
- Protein and blood cells - too big to filter out of blood.
- Glucose - actively reabsorbed back into the blood.
