名市大医学部２年コミュのHuman Biology [chapter 10]

ラスト、Chapter 10の解答例…。

というか、ここはどういう形式で出題されるのかいまいち不透明なので、RAA系の図（授業で配布されたやつ）を説明した文章を作ってみました。

RAA系は複雑なので、文章内容に自信が今ひとつありません。
おまけに相当長くなってしまったんで、今回の解答例の中で一番磨き甲斐がありそうです。
まぁこんなの試験で全部書かせるとは思えないので、使えそうな部分をつまみ食いして下さい。

とりあえず、僕のを叩き台にして、いい解答が生まれることを期待します。

(1) レニン・アンギオテンシン系の流れ図を理解しておくこと。
→各自でよろしくっ。

(2) 血圧や赤血球の量に腎臓がどのように関与しているのか理解しておくこと。
　　The renin-angiotensin-aldosterone (RAA) system can be activated when there is a loss of blood volume or a drop in blood pressure (such as in hemorrhage).
　　First, if the perfusion of the juxtaglomerular apparatus in the kidneys decreases, its cells release the enzyme renin. Then, renin cleaves an inactive peptide called angiotensinogen, which is secreted by the liver, and turns it into angiotensin I. Last, angiotensin I is then converted to angiotensin II by angiotensin-converting enzyme (ACE) which is found mainly in lung capillaries.
　　Angiotensin II is the major bioactive product of RAA system and drives blood pressure up in various ways. First, in the case it works directly for raising blood pressure, it is a potent vasoconstrictor of arterioles throughout the body. It, at the same time, promotes tubular Na+Cl- reabsorption and K- excretion, and thereafter, water is returned to the blood by the process of osmosis. Next, in the case it works indirectly, it acts to cause the release of aldosterone from adrenal gland, and causes ADH secretion by stimulating posterior pituitary gland. Aldosterone acts on the tubules in the kidneys causing them to reabsorb more Na+ and water from the urine in the same way as angiotensin II does. Aldosterone also acts on the central nervous system to increase an individual's appetite for salt, and stimulate the sensation of thirst. ADH stimulates reabsorption of water in the kidneys, too. In addition to these effects, angiotensin II also promotes vasoconstriction by activating sympathetic nervous system.
　　When the effective circulation increases in this way and, in turn, cardiac cells are stretched due to increased blood volume, ANH is secreted by the atria of the heart and then inhibits the secretion of renin and aldosterone. Its effect, therefore, is to promote the excretion of Na+, called natriuresis. If ANH is present, less water will be reabsorbed, even if ADH is present, because the reabsorption of water is dependent on a salt concentration gradient.
　　Asside from producing renin, the kidneys assist the endocrine system and also the cardiovascular system by producing erythropoietin. When the oxygen-carrying capacity of the blood is reduced, the kidneys secrete it and then it promotes red blood cell production by stimulating red bone marrow.