每日一词: 心血管系统 (Cardiovascular system)

心血管系统使血液在身体周围循环，将肺部的氧气和营养物质输送到器官、肌肉和神经。心脏将富百度竞价代理含氧气的血液通过一个血管网络——动生殖器脉泵送李庄案。当它到达组织中被称为毛细血管的微小血管时，血液释放出氧气，细胞利用它来制造能量。

细胞也会释放出废物，如二氧化碳，血液一往无前虎山行会吸收并带走这些废物。使用过的 "脱氧 "血液沿着静脉回到英语音标肺部，在那里吸收新鲜的氧气并再次开始循环。在静止状态下，正常的心脏通常每分钟跳动约70至80次，因为电脉冲使心脏肌肉有节奏地收缩。

心脏的每一侧都分为一个叫做心房的上腔和三次握手一个更大的下腔，叫做心室。心房是接收血液的腔室，心室是排出血液的腔室。血液从每个心房通过一个单向阀流入下面的心室。

The cardiovascular system circul匡威标志ates blood ar最性感的美女ound the body, transporting oxygen from the lungs and nutrients to organs, muscles and nerves. The heart pumps oxygen-rich blood through a network of blood vessels, the arteries. When it reaches tiny vess以人为本els called capillaries in tissues, blood releases the oxygen, 煮酒论英雄which cells use to make energy.

The cells also release waste p综合症roducts, such as carbon dioxide, which the blood absorbs and carries away. The used on 'deoxygenated' blood travelslionheart along veins and back to the lungs, where it 锁屏软件absorbs fresh oxygen and begins the cycle again小市民. At rest, a normal heart typically beats around 70 to 80 times a minute as electrical impulses make the cardiac muscles rhythmically contract.

Each side of the heart is divided into an upper chamber called an atrium and a larger, lo全国大学生广告艺术大赛wer chamber,张家界翼装飞行 cal代数几何le多媒体教学的优点d a ventricle. The atria are the blood-recei原子核结构ving chambers and the ventricles are the discharging chambers. Blood flows from each atrium through a one-way valve into thecpu是什么 ventricle below.