Blood flows into glomerulus from the afferent ateriole. The afferent arteriole is wider than the efferent arteriole so the blood is under high pressure. The blood in the glomerulus is higher in pressure than the Bowman's capsule. So blood plasma containing dissolved substances is pushed out into the lumen of the Bowman's capsule.
The substances include:
- amino acids
- inorganic ions like sodium, chloride…