Page 25 - Anatomy and Physiology of Farm Animals, 8th Edition

10 / Anatomy and Physiology of Farm Animals

(A) (B) (C)
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(D) (E)

(F) (G) (H)

Figure 1-6. Types of exocrine glands and comparison of simple and compound glands. (A) Simple
tubular gland. (B) Simple coiled tubular gland. (C) Simple branched tubular gland. (D, E) Simple acinar/
alveolar glands and simple branched acinar/alveolar glands. (F) Compound tubular gland. (G, H)
Compound acinar/alveolar glands. Compound tubuloacinar/tubuloalveolar glands consist of either a
mixture of tubular and acinar/alveolar secretory units or tubular secretory units “capped” by acini or
alveoli. Source: Eurell and Frappier, 2006. Reproduced with permission of John Wiley & Sons.

does. If the secretory portion of the gland terminology may be applied to ducts
forms a tube‐like structure, it is called draining lobes or lobules of glands, that is,
tubular; if the secretory portion resembles interlobar ducts and interlobular ducts,
a grape or hollow ball, it is called alveolar respectively.
or acinar (the terms are used inter- Another classification of glands is based
changeably). A combination of tubular and on the manner in which their cells elabo-
alveolar secretory structures produces a rate their secretion. By this classification,
tubuloalveolar gland. the most common type is the merocrine
Compound glands often are subdivided gland. Merocrine glands pass their secre-
grossly into lobes, which in turn may be tory products through the cell membrane
further subdivided into lobules. Hence, without any appreciable loss of cytoplasm
the connective tissue partitions (called or noticeable damage to the cell membrane.
septa) are classified as interlobar septa if The holocrine gland is the least common
they separate lobes, and as interlobular type. After the cell fills with secretory
septa if they separate lobules. Similar material, the entire holocrine gland cell