Gland Endocrine glands secrete substances that circulate through the blood stream. The glands secrete their products through basal lamina into the blood stream. Basil lamina typically can be seen a layer around the glands to which a million maybe more tiny blood vessels are attached. These glands often secrete hormones which play an important role in maintaining homeostasis. The pineal gland, thymus gland, pituitary gland, thyroid gland, and the two adrenal glands are all endocrine glands. Exocrine glands secrete their products through a duct onto an outer surface of the body, such as the skin or the gastrointestinal tract. Secretion is
Evolution of the brain as we progressed along the human timeline of evolution (see Homininae), starting from about 600 cm in "Homo habilis" up to 1600 cm in "Homo neanderthalensis" (male averages). The increase in brain size topped with Neanderthals; Brain size of "Homo sapiens" varies significantly between population (races), with male averages ranging between about 1,200 to 1,450 cm. Evolution of the brain The principles that govern the evolution of brain structure are not well understood. Brain to body size does not scale isometrically (in a linear fashion) but rather allometrically. The brains and bodies of mammals do not scale linearly. Small bodied