pituitary gland – 垂体
sella turcica – n. 蝶鞍
dura mater – n. 硬膜
anterior pituitary – 垂体前叶
designate – v. 指定，指明
deficiency – n. 不足，缺乏
overproduction – n. 过度生产
rhythmic – a. 节奏的，有节律的
diurnal rhythm – 昼夜节律
melanocyte – n. 黑素（细胞）
melanocyte-stimulating hormone (MSH) – 促黑激素
lipotropin – n. 促脂解素
posterior pituitary – 垂体后叶
deposit – v. n. 存放，使沉积
vasopressin – n. 加压素
osmolarity – n. 渗透性
osmoreceptor – n. 渗透压感受器
“let-down” reflex – 乳汁释放反射
intermediate lobe – 垂体中叶
enkephalin – n. 脑啡肽
endorphin – n. 内啡肽
★RN/ISPN Review ★
The Pituitary Gland 垂体
The pituitary gland is located in the skull in the bony sella turcica under a layer of dura mater. It is divided into three lobes: An anterior lobe, a posterior lobe, and an intermediate lobe. Traditionally, the anterior pituitary was known as the body’s master gland because it has so many important functions and, through feedback mechanisms, regulates the function of many other endocrine glands. In addition, its unique and protected position in the brain led early scientists to believe that it must be the chief control gland. However, as knowledge of the endocrine system has grown, scientists now designate the hypothalamus as the master gland because it has even greater direct regulatory effects over the neuroendocrine system, including stimulation of the pituitary gland to produce its hormones.
The anterior pituitary produces six major hormones: GH, adrenocorticotropic hormone (ACTH), follicle-stimulating hormone, luteinizing hormone, PRL, and thyroid-stimulating hormone (TSH, also called thyrotropin). These hormones are essential for the regulation of growth, reproduction, and some metabolic processes. Deficiency or overproduction of these hormones disrupts this regulation.
The anterior pituitary hormones are released in a rhythmic manner into the bloodstream. Their secretion varies with time of day (often referred to as diurnal rhythm) or with physiological conditions such as exercise or sleep. Their release is affected by activity in the CNS, by hypothalamic hormones, by hormones of the peripheral endocrine glands, by certain diseases that can alter endocrine functioning, and by a variety of drugs, which can directly or indirectly upset the homeostasis in the body and cause an endocrine response. Normally, diurnal rhythm occurs when the hypothalamus begins secretion of corticotropin-releasing factor (CRF) in the evening, peaking at about midnight; adrenocortical peak response is between 6 and 9 AM; levels fall during the day until evening, when the low level is picked up by the hypothalamus and CRF secretion begins again.
The anterior pituitary also produces melanocyte-stimulating hormone (MSH) and various lipotropins. MSH plays an important role in animals that use skin color changes as an adaptive mechanism. It also might be important for nerve growth and development in humans. Lipotropins stimulate fat mobilization.
The posterior pituitary stores two hormones that are produced by the hypothalamus and deposited in the posterior lobe via the nerve axons where they are produced. These two hormones are ADH, also referred to as vasopressin, and oxytocin. ADH is directly released in response to increased plasma osmolarity or decreased blood volume (which often results in increased osmolarity). The osmoreceptors in the hypothalamus stimulate the release of ADH. Oxytocin stimulates uterine smooth muscle contraction in late phases of pregnancy and also causes milk release or “let-down” reflex in lactating women. Its release is stimulated by various hormones and neurological stimuli associated with labor and with lactation.
The intermediate lobe of the pituitary produces endorphins and enkephalins, which are released in response to severe pain or stress and occupy specific endorphin receptor sites in the brainstem to block the perception of pain. These hormones are also produced in peripheral tissues and in other areas of the brain. They are released in response to overactivity of pain nerves, sympathetic stimulation, transcutaneous stimulation, guided imagery, and vigorous exercise.
1. One of the statements below is true. Which one?
A. The anterior pituitary produces testosterone from cholesterol and releases it when releasing hormones arrive from the hypothalamus.
B. The hypothalamus produces ADH and oxytocin which are stored in the posterior pituitary.
C. The posterior pituitary contains autonomic centres that exert neural control over the adrenal glands.
D. The thalamus produces ADH and oxytocin which are stored in the anterior pituitary
2. From where are antidiuretic hormone and oxytocin released?
A. The anterior pituitary
B. The posterior pituitary
C. The adrenal cortex
D. The adrenal medulla
“在线自测”
ISPN/RN复习练习、效果检验一站完成。
答案 Answers 1. B. the hypothalamus produces ADH and oxytocin which are stored in the posterior pituitary. Rationale: Testosterone is not produced in the pituitary, nor does the pituitary contain autonomic centres. 2. B. The posterior pituitary Rationale: ADH & OT are produced in the hypothalamus and transported to the posterior pituitary.
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