Anatomic regions approximation

Most enzymatic hydrolysis of the macromolecules in food occurs in the small intestine. The small intestine is approximately 5 m long with a radius of approximately 2 cm, and is divided into three anatomical regions the duodenum (the first 25 cm), the jejunum (the second 2.0 m), and the ileum (the last 2.75 m). The intestinal membrane wall consists of four basic layers the mucosa, submucosa, muscularis, and serosa. 

Corticosteroids are only minimally absorbed following application to normal skin for example, approximately 1% of a dose of hydrocortisone solution applied to the ventral forearm is absorbed. Long-term occlusion with an impermeable film such as plastic wrap is an effective method of enhancing penetration, yielding a tenfold increase in absorption. There is a marked regional anatomic variation in corticosteroid penetration. Compared with the absorption from the forearm, hydrocortisone is absorbed 0.14 times as well through the plantar foot arch, 0.83 times as well... 

The conducting airways go down the first 15 generations and constitute the anatomical dead space, which is approximately 100—150 mL in a human adult [32]. Beyond this region lies the respiratory region. These continue to divide until they reach the alveolar sacs, with a total surface area of 70—80 m [33]. 

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