Serous fluid major salivary glands produce mixed (serous and mucus) saliva. Another type of serous fluid is secreted by the serous membranes (serosa), two-layered membranes which line the body cavities. Serous membrane fluid collects on microvilli on the outer layer and acts as a lubricant and reduces friction from muscle movement. This can be seen in the lungs, with the pleural cavity. Blood serum is the component of blood that is neither a blood cell, nor a clotting factor. Blood serum and blood plasma are similar, but serum does not contain any clotting factors, such as fibrinogen, prothrombin, thromboplastin and many others.
Mucus improve the odds of pregnancy. It is also proposed as a method to avoid pregnancy. Mucus is able to absorb water or dehydrate through pH variations. The swelling capacity of mucus stems from the bottlebrush structure of mucin within which hydrophilic segments provide a large surface area for water absorption. Moreover, the tunability of swelling effect is controlled by polyelectrolyte effect. Polymers with charged molecules are called polyelectrolytes. Mucins, a kind of polyelectrolyte proteoglycans, are the main component of mucus, which provides the polyelectrolyte effect in mucus. The process of inducing this effect comprises two steps: attraction of counter-ions and