Corneocytes Corneocyte surface area

The study could show that glycerol induced a shrinking of superficial corneozytes, which is independent from osmotic effects (Figure 20.2). An equimolar NaCl solution had no significant influence on the corneocytes surface area compared to untreated and H2O treated corneocytes. Only a mild, but significant increase of SC hydration, measured by capacitance was monitored (Figure 20.3). 

Fluhr, J.W., Pelosi, A., Lazzerini, S. etal. Differences in corneocyte surface area in pre- and postmenopausal women. Assessment with the noninvasive videomicroscopic imaging of corneocytes method (VIC) under basal conditions. Skin Pharmacol. Appl. Skin Physiol. 2001, 14 (Suppl 1) 10-6. 

In general, rat skin has been proven more permeable than human skin (ECETOC, 1993). This is likely to be caused by the different structure of the skin in both species (e.g. number of appendages, intercellular lipid composition of the stratum corneum and corneocyte surface area). It should be noted, however, that some cases have been reported where rat skin was found to be less permeable than human skin (Hotchkiss et al., 1992). Since the availability of human skin is limited, pig skin is often used. Because of its similar morphology and barrier function (Bronaugh et al., 1982), pig skin is often considered a good alternative to human skin. 

FIGURE 2.2 (a) The corneocyte is a flat, hexagonal-like structure with a surface area of about 1000 /zm2 and... 

Corneocytes are about 1 /xm thick and have a mean area of approximately 1000 /xm2. However, the surface area is dependent upon age, anatomical location, and conditions that influence epidermal proliferation such as chemical irritation and UV irradiation.3 Corneocyte size increases with age. This is sometimes assumed to be related to the increased transit time within the SC. On most body sites, the SC consists typically of 12 to 16 layers of flattened corneocytes. 

The major barrier of the skin is the outermost dead layer, the stratum corneum. A number of routes of penetration of a drug, across this region can be identified. First, the appendages, the pilosebaceous and eccrine glands, form a potential shunt route across the stratum corneum. The relative surface area of these is very small (<0.1%) and there has been little conclusive evidence to suggest that this is a major route. Second, the penetrant could diffuse across the entire stratum corneum through the dead cells, the corneocytes. A large surface area is available but the... 

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