Formation of urine
- Created by: Steff06
- Created on: 28-02-16 12:07
View mindmap
- Formation of urine
- Ultrafiltration:
- Blood flows into the GLOMERULUS from the AFFERENT arteriole. The AFFERENT arteriole is WIDER than the EFFERENT arteriole.
- Difference in diameters of arterioles ensures that blood in the capillaries of the glomerulus is under increased PRESSURE.
- Pressure in the glomerulus is higher than in the Bowman's capsule.
- Glomerular filtration:
- 1. Glomerulus brings a large surface area of blood capillaries in close contact with the Bowman's capsule.
- 2. Liquid and small molecules are filtered from the blood under pressure.
- 3. Glomerular filtrate is produced containing WATER, GLUCOSE, SALTS, UREA, AMINO ACIDS.
- 4. PROTEINS and BLOOD CELLS are TOO BIG to pass into the tubule.
- ADAPTIONS of Bowman's capsule for ultrafiltration:
- 1. ENDOTHELIUM of the capillary. Has NARROW GAPS between cells and is ONE CELL thick.
- Provides SHORTER DIFFUSION distance. Gaps allow blood plasma and substances dissolved in it to PASS THROUGH.
- 2. BASEMENT MEMBRANE. Consists of fine MESH of COLLAGEN FIBRES and GLYCOPROTEINS.
- Acts as FILTER to prevent passage of molecules greater than 69000.
- 3. PODOCYTES (Epithelial cells of Bowman's capsule). Have specialised finger-like PROJECTIONS (major processes).
- These ensure there are GAPS between the cells so fluid from blood can pass into LUMEN of Bowman's capsule.
- 1. ENDOTHELIUM of the capillary. Has NARROW GAPS between cells and is ONE CELL thick.
- Presence of PROTEINS left in the capillary means the blood has a very LOW WATER POTENTIAL.
- This ensures some fluid is retained in the blood and is important to help to REABSORB WATER later on.
- Ultrafiltration:
Comments
No comments have yet been made