Serum (blood) Serum (blood) In blood, the serum () is the component that is neither a blood cell (serum does not contain white blood cells- leukocytes, or red blood cells- erythrocytes), nor a clotting factor; it is the blood plasma not including the fibrinogens. Serum includes all proteins not used in blood clotting and all the electrolytes, antibodies, antigens, hormones, and any exogenous substances (e.g., drugs and microorganisms). The study of serum is serology. Serum is used in numerous diagnostic tests, as well as blood typing. Measurements of serum concentrations has proved useful in many fields including clinical trials of therapeutic vs
Mucus normal breathing. Further distinction exists between the superficial and cell-lining layers of ASL, which are known as mucus layer (ML) and pericilliary liquid layer (PCL), respectively. "Phlegm" is a specialized term for mucus that is restricted to the respiratory tract, whereas the term "nasal mucus" describes secretions of the nasal passages. Nasal mucus is produced by the nasal mucosa; and mucus lining the airways (trachea, bronchus, bronchioles) is produced by specialized airway epithelial cells (goblet cells) and submucosal glands. Small particles such as dust, particulate pollutants, and allergens, as well as infectious agents and bacteria are caught in the viscous