Differences Between Endocrine vs Exocrine Glands
Gland is a specific structure which secrets various chemical substances such as enzymes, hormones, and metabolites. There are two types of glands in the body called endocrine glands and exocrine glands. Throughout the embryo development, endocrine glands lack ducts and remain as blocks of tissue. So, it secrets chemical substances directly to the blood stream, while exocrine gland secrets its product into a duct. However, some glands may have both endocrine and exocrine activities such as the pancreas (Taylor et al, 1998).
Endocrine Glands
Endocrine system is composed of a number of endocrine glands. Endocrine glands have specific characteristics such as secrete hormones into the blood stream, no ducts (so, it is called ductless glands). Therefore, these glands have rich blood supply with a large number of blood vessels. Endocrine system and nervous system function in a coordinated way to maintain the many physiological body activities. Hypothalamus, pituitary gland (Posterior and Anterior), adrenal cortex are some of major human endocrine glands.
There are four types of vertebrate hormones, which act on target cells (Taylor et al, 1998). Peptides and proteins, derivative of amines, steroids and fatty acids are them. Endocrine gland releases hormones as a response to the level of specific metabolite in the blood stream. For an example, pancreas releases insulin due to a higher level of glucose. Except that situation, endocrine glands secrete hormones either due to the presence of another hormone or due to stimulation by neurons.
Exocrine Glands
Exocrine gland is a gland that secretes chemical substances into ducts. As an example, sweat gland and salivary glands. In salivary glands, saliva is produced within the gland, and it secrets into saliva duct and travels to the surface. Salivary glands, sweat glands, mammary glands, and adrenal gland are some of examples for the exocrine glands. There are two types of exocrine glands, simple type and compound type. Tubular, branched tubular, and coiled tubular are examples for simple type of exocrine glands and tubular and alveolar are examples for compound exocrine glands.
These exocrine glands have three different ways of secreting products into ducts. Merocrine, holocrine, and apocrine are those three different ways.
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What is the difference between Endocrine Glands and Exocrine Glands? • The main difference between the endocrine gland and exocrine gland is that, an endocrine gland lacks ducts and remains as blocks of tissue. • So, endocrine gland secrets chemical substances directly to the blood stream, while exocrine gland secrets its product into a duct. • Exocrine glands secrete their products into the external environment, but endocrine glands release their products into internal environment. • The hormones produced by endocrine glands circulate through the blood stream and over the body and act on the target, while products of exocrine gland do not circulate all over the body. • These endocrine glands have relatively large blood supply than exocrine glands. • Exocrine glands have more complex structure than endocrine glands. • Merocrine, holocrine, and apocrine are three different ways of secreting products of exocrine glands into ducts, but endocrine gland do not have such system. • Responses of endocrine glands are slower than exocrine glands since it travels through the blood stream. • Endocrine system and nervous system function in a coordinated way to maintain the many physiological body activities, but exocrine system does not.
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References:
Taylor, D.J., Green N.P.O., Stout, G.W., (1998), Biological Science. Cambridge University Press, Cambridge