3 Mixed seromucous salivary glands, structure of glandular acini The three large glands have a different composition in the type of secretory units is concerned: - The parotid glands (which represent 25% of the production of saliva) are formed by serous production units and they are compound acinar type.
How Anti-Lock Brakes Work. An anti-lock brake system (ABS) is a braking system that is made to allow a vehicle to maintain traction with the road when braking. Braking is controlled by driver input via the brake pedal, and older braking systems response to a driver braking suddenly or with intense pressure was sometimes to lock up or skid.
There is a valve in the brake line of each brake controlled by the ABS. 1  On some systems, the valve has three positions: 2  In position one, the valve is open; pressure from the master cylinder is passed right through to the brake. 3  In position two, the valve blocks the line, isolating that brake from the master cylinder.