pituitary gland

a gland, pea-sized in humans, that lies at the base of the brain and is connected by a stalk (the infundibulum) to the hypothalamus. The pituitary gland is divided into an anterior and a posterior lobe, which differ in function. The anterior lobe (adenohypophysis) produces and secretes tropic hormones (i.e., thyroid-stimulating hormone, follicle-stimulating hormone, corticotropin, and luteinizing hormone), growth hormone, prolactin, and melanocyte-stimulating hormone in response to releasing hormones from the hypothalamus. The posterior lobe (neurohypophysis) secretes two hormones, vasopressin and oxytocin, which are synthesized in the hypothalamus and transported down axons in the infundibulum to the neurohypophysis in response to direct neural stimulation. The pituitary’s role particularly in secreting tropic hormones, which regulate the production of other hormones, has resulted in its designation as the “master gland of the endocrine system.” Also called hypophysis; hypophysis cerebri.

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Psychology term of the day

November 18th 2024

recessive allele

the version of a gene (see allele) whose effects are manifest only if it is carried on both members of a homologous pair of chromosomes. Hence, the trait determined by a recessive allele (the recessive trait) is apparent only in the absence of another version of that same gene (the dominant allele). The term autosomal recessive is used to describe patterns of inheritance in which characteristics are conveyed by recessive alleles. For example, Tay–Sachs disease is an autosomal recessive disorder.