circulatory system循环系统英文资料

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脉管学--循环系统

位于房室口、肺动脉口和主动脉口的周围，心肌和瓣膜附着处的由致密的结缔组织构成的纤维性支架。包括四个瓣纤维环、左纤维三角、右纤维三角（中心纤维体）、圆锥韧带、室间隔膜部和瓣膜间隔等。
（2）心壁
心内膜心肌层心外膜
形成瓣膜和腱索
心房肌和心室肌不相连续，心室肌厚于心房肌，左心室肌厚于右心室肌。心房肌分为两层，心室肌分为外斜、中环和内纵三层。
1、心最小静脉 Smallest Cardiac Vein 2、心前静脉 Anterior Cardiac Vein
心脏各腔室右心房
3、冠状窦 Coronary Sinus
心大静脉心中静脉心小静脉
冠状窦右心房
心
大
心前
静脉
心小静
静
脉
脉
心中静脉
冠状窦
7、心包 Pericardium
脉管学--循环系统
脉管学 Angiology
（循环系统 circulatory system）
一、组成
心血管系统
心Heart 动脉Artery 毛细血管Capillary 静脉Vein
淋巴系统
淋巴管道淋巴器官淋巴组织
循环系统的功能？
细胞
组织液
毛细血管
二、心血管系统 Cardiovascular System
一入口右房室口：右房室瓣（三尖瓣）
RV
一出口肺动脉口：肺动脉瓣
（3）左心房 LA
前部：左心耳后部：固有心房（左心房窦）
固有心房
右
左心耳
肺上
、
下
静
脉
口
左房室口
左肺静脉口（上、下）：无瓣膜
四入口

英文医学课件：6 Circulatory system循环系统

• processes –microvilli-like, finger-liked
• plasmalemmal vesicle
/60-70nm, constitute about 25-35% of total volume
/transendothelial channel
function: transport large molecules and storage of membrane (for enlarge, enlongated, pore-formed and microvilli)
circulatorycirculatorysystemsystemclosedtubularsystembloodcirculatorycardiovasculars心血管系统lymphvasculars淋巴管系统capillariescapillariesbasementmembrane
Chapter 9
ry
---Structural feature:
• endothelial cell: -have fenestrae or pore (6080nm in D, with 4-6 nm diaphragm)
• basal lamina: complete
of
endocardium:
endothelium + DCT
• prevent the back flow of blood
2) Conducting S
① components:
---sinoatriol node node): located epicardium of atrium
(SA in
1. Capillaries
1) LM: • endothelium: • basement membrane: • pericyte: /flattened with processes /function:

完整版人体解剖生理学第六章循环系统

3
一、循环系统的组成
4
第一节循环系统的组成和结构
循环：是指各种体液不停地流动和互相交换的过程，包括：血液循环（起主导作用，也是最主要）、淋巴液循环、脑脊液循环、组织液循环。
血液循环：是指血液在心血管闭合的管通系统内按一定方向，周而复始不停的流动。动力器官：心脏分部：按循环途径可分为两部分：体循环和肺循环：功能：不断地将氧气、营养物质和激素等运送到全身组织器官并将各器官、组织所产生的 CO2 和其它代谢产物带到排泄器官排出体外。以保证机体物质代谢和生理功能的正常进行。
1、工作细胞：无自律性心房肌、心室肌
2、特殊分化心肌细胞：收缩功能基本丧失自律细胞：窦房结、房室交界 (房结区、结希区) 房室束及左右分支、浦肯野纤维非自律细胞：结区
（二）心肌细胞的跨膜电位
?工作细胞的跨膜电位及其离子基础 (心室肌)
1、心肌细胞静息电位 :
心肌细胞在静息状态下膜内为负，膜外为正，呈极化状态，这种膜内外的电位差。
在神经体液调节下，血液沿心血管系统循环不息。
1、体循环左心室→主动脉→各级动脉 →毛细血管→各级静脉→上腔静脉、下腔静脉和冠状窦 →右心房
2、肺循环
右心室→肺动脉→肺泡壁的毛细血管网→肺静脉→左心房
一、心
（一）心的位置
位于中纵隔内，2/3居于正中线左侧，1/3居于右侧。
前方：胸骨体和 2-6 肋软骨后方：5-8 胸椎体心包区：心的前方大部分被肺和胸膜所遮盖，只下部一小区域借心包与胸骨体下半和左侧第 4-5类软骨相邻。
入口：左右两侧→ 对肺静脉口。
出口：左房室口 → 二尖瓣→ 左心室。
4. 左心室 left ventricle

血循环系统 - 英文版

Circulatory System∙ Organ system that passes nutrients (such as amino acids, electrolytes and lymph), gases,hormones blood cells, etc. to and from cells in the body to help fight diseases, stabilize body temperature and pH, and maintain homeostasis. ∙ Anything and everything about circulation the body ∙ Composition:o Cardiovascular system: distributes blood: Circulation that happens in the heart and blood vessels ∙ Lymphatic system: returns excess filtered blood plasma from interstitial fluid (between cells as lymph): protection∙ Principal functions of vertebrate circulatory systemof all the substances essential for cellular metabolism▪Respiratory –transports O 2to the tissue cells through the RBC ▪ Nutritive – carries absorbed nutrients through the liver and to the cells ▪ Excretory – removes metabolic wastes , excess water and other substances▪Hormones – part of endocrine systemo Regulation – transport regulatory hormones & temperature regulation▪ Hormone transport – blood carries hormones and carry them to distant targetorgans they regulate▪ Temperature regulation – maintenance of a constant body temperature inwarm-blooded animals.o Protection – protection against injury and foreign microbes▪ Blood clotting – protects against blood loss when vessels are damaged▪ Immune defense – WBCs (leukocytes) provide immunity against many disease-causing agents∙ Basic Typeso Gastrovascular cavity∙ Hydras have 1 opening; water entersand circulates∙ Oxygen/ nutrients are absorbed byChoanocytes∙ Consists of a epidermis andChoanocyteso Open Circulatory System▪Arthropods and some mollusks▪Basic components ofcardiovascular systems∙Hemolympho Limits sizeo Blood + lymph; goesBack into the heart∙Blood vessels- terminate in aopening∙One or more hearts∙Hearts are just musculartubes ▪There is no distinction between the circulating fluid (blood) & the extracellular fluid of the body tissues (interstitial fluid or lymph)▪Fluid in vessels and interstitial fluid mingle in 1 compartment as hemolymph▪Nutrients & waste exchanged by diffusion between hemolymph and body cells ▪Energetically inexpensive▪Limitation: hemolymph can’t be selectively delive red to different tissueso Closed Circulatory System▪Blood and interstitial fluid arephysically separated▪Larger, more active animals need ahigher pressure to pump blood to allbody cells (more efficient bloodpumping)▪Found in earthworm, cephalopods,and all vertebrates▪Advantages:∙Animals can grow larger withmore efficient supply∙Blood flow can be selectivelycontrolled▪TYPES∙Single Circulationo Fishes∙Double Circulationo Crocodiles,birds,Mammals∙Amphibians andmost Reptileshave systems withfeatures of bothCLOSED CIRCULATORY SYSTEMSingle Circulation System – fish (most primitive)∙ Blood passes through the heart only once in a full circuit∙ Heart → Gills (have thin membrane that’s why arteries have lowpressure) → Body → Heart∙ Single atrium collects blood from tissues∙ Single ventricle pumps blood out of the heart ∙ Arteries carry blood away from the heart∙ Blood picks up O 2 and drops CO 2 and goes on through arteries toother body tissues∙ Limitation: pressure lowers; big fishes have to breathe continuouslyDouble Circulation System∙ Blood passes through the heart twice in one full circuit ∙ Heart →Lungs →Heart → Body → Heart∙ Amphibianso Unique in that they can breathe through theirlungs and skino Heart Pumps blood to either▪ Pulmocutaneous circulation – carriesdeoxygenated blood to both the lung and skin▪ Systemic circulation – body tissueso Heart has▪ 3 chambers▪ 2 atria to collect bloodo Right atrium – blood from the body (NOTLUNGS) and is low in O 2 (except oxygenated blood from skin)o Left atrium - blood from lungs (O 2 rich whenair is breathing)o Single ventricle – mixture of oxygenated anddeoxygenated bloodo Internal recesses – separates oxygenatedand deoxygenated (not perfect)o Both atria dump into 1 ventricleo Internal structure keeps 2 O 2 oxygenated and deoxygenated blood mostly separated o Some mixing does occur reducing efficiencyo Noncrocodalian reptiles also have 2 atria and 1 ventricleo Ventricle is partially divide – higher effieciencyo Both must use low moderated pressure systems to minimize pressure flowing through lung tissue∙Crocodiles, birds and mammalso Reptiles have transitional heartso Oxygenated and deoxygenated blood separates into 2 distinct circuitso Systemic circulation – to the bodyo Pulmonary circulation – to the lungso 2 atria and 2 ventriclesThe Human Heart∙Hollow, cone-shaped muscle located between the lungs and behind the sternum (breastbone), tilted at to the left∙About the size of a human fist∙2/3 is located to the left of the midline of the body and 1/3 to the right∙The apex (pointed end) points down and to the left∙Ave. weight between 250-350 grams∙ 4 chambers:o 2 superior atria; the receiving chamberso 2 inferior ventricles; the discharging chambers∙(interatrioventicular) septum – separated the left atrium and ventricle from the right atrium and ventricle, dividing the heart into 2 functionally separate and anatomically distinct units.∙Layerso Endocarium– smooth, inside lining of the heart▪In contact with the blood that the heart pumps▪Protects the cavityo Merges with the inner lining (endothelium)of blood vessels and cover heart valveso Myocardium - middle layer of heart muscle▪Layer that contractso Epicardium or visceral pericardium– outer layer of the heart▪ A fluid sac that surrounds the heart∙Valves:o Atrioventricular (AV) valves - found between the atria and ventricles.▪tricuspid valve, or right atrioventricular valve▪ Between the right atrium and the right ventricle.▪Usually has three papillary muscles.▪Prevents blood from the right ventricle to go to the right atriumo Mitral valve or bicuspid valve or left atrioventricular valve▪ A dual-flap valve that lies between the left atrium and the left ventricle.▪Prevents blood from the left ventricle to go to the left atriumo Semilunar valves - separate the left and right ventricle from the pulmonary artery and the aorta, respectively▪aortic valve∙found between the left ventricle and aorta▪pulmonary valve∙lies between the right ventricle and the pulmonary artery ∙Blood Vessels∙Aortao largest artery in the bodyo arises from the left ventricle of the heart, goes up(ascends) a little ways, bends over (arches), thengoes down (descends) through the chest andthrough the abdomen to where ends by dividinginto 2 common iliac arteries that go to the legs.o Anatomically, it is divided into the ascending aorta,the aortic arch, and the descending aorta.o Can accommodate the greatest pressureo It serves to supply oxygenated blood to the majororgans of the body.o the central conduit from the heart to the body.∙Superior Vena Cava:o A large vein that receivesblood from the head, neck,upper extremities, and thoraxand delivers it to the rightatrium∙Inferior Vena Cava:o A large vein that receivesblood from the lowerextremities, pelvis andabdomen and delivers it tothe right atrium of the heart ∙Pulmonary Artery:o begins at the base of the right ventricle.o it delivers deoxygenatedblood to the lung.∙Pulmonary Vein:o large blood vessels that carry oxygenated blood from thelungs to the left atrium of theheart.o In humans there are fourpulmonary veins, two fromeach lung.∙Myogenic Hearto Electrically excitable, generates own action potentialo Contains auto-rhythmic fibers- can initiate periodic action potential w/o neural activation▪SA Node – most important group of auto-rhythmic cellso Nervous input can increase or decrease rate∙Sino-Atrial Nodeo Found at the upper part of the right atrium of the hearto Acts as the hearts natural pacemakero Triggers a sequence of electrical events in the heart that control the regular muscle contractions (every 0.6 seconds or 100/min) that pump blood out of the heart with a rhythm of about 60-70 beats/min (resting heart)o Depolarization is transmitted through 2 pathways▪Cardiac muscles of the left atrium▪Cardiac muscles of the right atrium and AV Nodeo Depolarization spread quickly among the muscles of the left and right atriasimultaneously▪ Possible because of gap junctions in intercalated diskso AV node provides the only pathway for conduction of depolarization from atria toventricleso Delays ventricular contraction by 0.1 sec (part where atrium transfers blood to ventricles) o Permits atria to finish contraction and emptying of contentso Wave of depolarization is conducted to ventricles by AV bundle or bundle of His▪ Relays depolarization to Purkinje Fibers∙ Stimulates contraction of myocardial cells of the L and R ventricle almostsimultaneouslyo Contraction of the heart is controlled by Ca and troponin/tropomyosin system similar toskeletal muscleso Pattern of voltage change produced by SA node can be measured with electrodes onthe skin▪ Voltage measurements on the skin of the chest are called electrocardiogram(ECG)∙ Record of electrical impulses generated during the cardiac cycle ∙ Monitor electrical activity produced by SA node ∙ Examine fornormal frequency, strength,duration and direction of signals∙ P wave - begins when SA node fires; coincides with depolarization of the atria and, therefore, associatedwith atrial systole ∙ QRS Complex – 3 waves – AV node excites ventricle∙ T wave- repolarization of ventricles back to resting state FLOW OF BLOOD∙ Functioning:o Flow of blood through the heart: one direction▪ from the atria to theventricles, and out of the arteries.▪ Blood is prevented fromflowing backwards by the valves.∙From the left atrium the blood moves to the left ventricle which pumps it out to the body (via the aorta).∙From the R atrium blood moves to the R ventricle which pumps the blood to the lungs∙On both sides, the lower ventricles are thicker and stronger than the upper atria.∙The muscle wall surrounding the left ventricle is thicker than the wall surrounding the right ventricle due to the higher force needed to pump the blood through the systemiccirculation.∙IT ONLY TAKES ABOUT 20 SECONDS TO PUMP BLOOD TO EVERY CELL OF OUR BODYCARDIAC CYCLE (heart beat)∙Filling of atrium, pumping of ventricle∙the sequence of events that occurs when the heart beats.∙ two phases:o diastole phase, the heart ventricles are relaxed and the heart fills with blood.o systole phase, the ventricles contract and pump blood to the arteries.∙One cardiac cycle is completed when the heart fills with blood and the blood is pumped out of the heart.∙Diastole Phase – R sideo Atria and ventricles are relaxed and AV valves are openo Deoxygenated blood from the superior and inferior vena cavae flows into the right atriumo Open AV valves allow blood to pass through to the ventricleso SA node contracts triggering the atria to contracto R atrium empties its contents into R ventricleo Tricuspid Valve closes ∙Systole Phase – R sideo R ventricle receives impulses from the Purkinje Fibers and contracts o SL (pulmonary) valve openso Deoxygenated blood is pumped in to the pulmonary artery. SLvalve closeso Pulmonary artery carries blood to lugs to pick up oxygeno Blood is returned to the L atrium by pulmonary veins∙Diastole Phase – L sideo Blood from pulmonary veins fill left atrium (blood from venacava is also filling the R Atrium) o SA node contracts triggering left atrium to contracto AV (mitral) valves openso L atrium empties its content to L ventricle ∙Systole Phase – L sideo L ventricle receives impulses from the Purkinje fibers and contracts o SL (aortic) valve openso Oxygenated blood is pumped into the aorta. Aorta providesoxygenated blood to the body o Oxygen depleted blood isreturned to the heart via venacavae∙CARDIAC OUTPUT∙Amount of blood the heart pumpsper unit time in L/min∙Depends in the size of the heart and how often it beats∙Stroke volume - amount of blood a heart ejects at each beat∙Higher heart rates of smaller animals gives them a greater cardiac outputthat would be predicted based onthe size of their hearts (must meethigh metabolic demands) HEART SOUNDS∙Lub-dubo the 1st heart sound (lub) is causedby the vibration of the heart atthe time of the closure of thetricuspid and mitral valves.o the 2nd heart sound (dub) iscaused by the vibrations at thetime of closure of the pulmonicand aortic valvesHEART BEAT∙Regular Heart Beat: 70-80 beats a minute∙When you run around a lot your heart pumps more blood into yout body—maybe up to 200 times a minute∙As people grow older their heart rates changeo A newborn baby has a heart rate of about 130o 3 year-old: about 100o18 year-old: about 90 times a minuteo Adult: 70-80o The older you get the slower your heart beats∙An average heart pumps about 10 mililiters of blood into your body with every beat∙That’s about 5L every minute or about 7200L everydayPULSE∙ Represents the tactile aterial palpitationof the heartbeat through the fingertips ∙ May be palpated in any place wherean artery is compressed against a bone, such as at the neck (carotid artery), at the wrist (radial artery), behind the knee (popliteal artery), on the inside of the elbow (brachial artery), and near the ankle joint (posterior tibial artery)BLOOD∙ Specialized bodily fluid in animals thatdelivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those some cells ∙ Amount in adults: 4.5-6 quarts ∙ Functionso Transport of gases, nutrients,waste products, and hormones o Maintenance of bodytemperatureo Protection from substance o Clot formationCOMPONENTS OF BLOOD∙ Erythrocytes (Red Blood Cells)o Life span: 120 dayso Function: to carryoxygen from the lungs to every cell in the bodyo Makeup almost 99.9%of formed elements in bloodo Composition: proteinand iron compound, called HEMOGLOBIN , that captures oxygen molecules as the blood moves through the lungsUnites readily with oxygen to form oxyhemoglobin (found in arteries)∙ Form of oxygen as it is transported in the blood stream ∙ Together with iron, it gives blood a bright red coloro Membrane is flexibleo Able to bend in many directions w/o breaking o Biconcave disc shape o No nuclei o About 4.5M in female and 5M in males per cubic mm of blood o Formed in the reticulo-endothelial tissue of the bone marrow o Discharged into the blood capillaries after losing nuclei o Remain in the blood for 3-5 weeks o Destroyed by spleen and liver∙ Leukocytes(White blood cells)o With nucleo Average from 6 thousand – 10Tcells per cubic mm of blood, or about 1 for every 700 RBC o Primary defense mechanismagainst bacteria, viruses, fungi, and parasiteso Produce antibodies, which arereleased into the circulating blood to target and attach to foreign organismso WBC are classified according to their size, shape of nucleus & reaction to dyes used in staining them∙ Thrombocytes (Platelets)o Small irregularly shaped clearcell fragments (i.e. cells that do not have a nucleus o 2-3 m in diametero Derived from fragmentation ofprecursor megakaryocytes o Average lifespan: 5-9 dayso Natural source of growth factor▪ Play a significant role inthe repair and regeneration of connective tissueso Involved in hemostasis(process that stops the flow ofblood), leading to the formation of blood clots▪ Ability of the system to prevent excessive blood loss upon injuryo Normal platelet count: 150,000-450,000/ of blood▪ If too low, excessive bleeding can occur▪ If too high, blood clots/thrombosiscan form∙ May obstruct blood vesselsand result in stroke, myocardial infarction, pulmonary embolism or the blockage of blood vessels to other parts of the body, such as extremities of the arms or legsBLOOD CLOT FORMATION∙ Platelets (cell fragments) in the bloodstream come into contact w/ damaged blood vesselFirst to defendMacrophages∙Platelets and vessel wall release enzyme thrombokinase∙Conversion of inactive enzyme prothrombin into active thrombin∙Thrombin catalyses the conversion of fibrinogen to insoluble fibrin∙Fibrin forms a over the wound that traps RBCS and seals the wound∙Resulting jelly clot like exposure to air to form a scab∙Calcium, vitamin K, and a variety of enzymes called factors are also necessary for efficient blood clotting∙HEMOPHILIAo Genetic defect in clotting factorso Inherited deficiency of a specific clotting factor causes thiso Most common form is X-linked recessive mutationo Treatment requires transfusions of purified clotting factors from donors or genetically engineered organismso Attempting gene therapyBLOOD TYPE∙The most common blood type classification systemis the ABO system discovered by Karl Landsteiner.o observed two distinct chemical moleculeson the surface of the red blood cells and labeledmolecules "A" and "B."o If the red blood cell had only "A" moleculeson it, that blood was called type A.o If the red blood cell had only "B" moleculeson it, that blood was called type B.BLOOD VESSELS∙Arterieso Conduct blood away from the hearto contain a high percentage of smooth muscle.o The artery walls consist of three layers:▪Tunica Adventitia: strong outer covering of arteries and veins which consists of connective tissues, collagen and elastic fibers.▪Tunica Media: the middle layer and consists of smooth muscle and elastic fibers.This layer is thicker in arteries than veins.▪Tunica Intima: the inner layer which is in direct contact with the blood flowing through the artery. It consists of an elastic membrane and smooth endothelialcells.∙Arterioleso Most highly regulated blood vessels in the bodyo Contribute the most to overall blood pressureo Respond to a wide variety of chemical &electrical messages and are constantly changing size to speed up or slow down blood flow∙Capillarieso Site of gas and nutrient/waste exchangeo Single-celled layer of endothelium on a basement membraneo Smallest and narrowest vessels in the body∙Blood enters capillary on arteriole end under pressure∙Pressure forces some fluid out of the blood (not RBC or large proteins)∙Most of the fluid that leaves will be recaptured by the venule end of the capillary∙Venuleso Small, thin extensions of capillaries∙Veinso Conduct blood back to the hearto Thinner and less muscular than arteries o Need help returning blood to the heart▪Smooth musclecontractions help propelblood▪Valves inside veinssqueezed by skeletalmusclesDISORDERS∙Systemic hypertension (High Blood Pressure)o High BP in the systemic arterieso Usually caused by the constriction of the small arteries (arterioles)o Causes: obesity, smoking, aging, etc.∙Congestive heart failureo Condition in which the heart’s function as a pump is inadequate to meet the body’s needo Leads to a buildup of fluid in the lungs and surrounding body tissueso Results from pulmonary hypertension- blood backs up in the lungs, raising pressure, and forcing fluid out into lung tissue∙Atherosclerosiso Disease of the arteries characterized by the deposition of plaques of fatty material on their inner wallso Usual cause of heart attack, strokes and peripheral vascular diseaseo Coronary artery disease results from plaque forming in the coronary arteries supplying the heart muscle∙Myocardial infarction (MI) /Heart Attacko Occurs when blood flow stops to a part of the heart causing damage to the heart muscleo Localized regions of the heart muscle dieo Cardiac angioplasty can detect narrowing of coronary vesselso Balloon angioplasty can widen the lumen of narrowed vesselso Coronary artery bypasses take a healthy blood vessel and use it to replace a blockedcoronary artery。

circulatory system循环系统

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The lymphatic system is a widely distributed system with multiple functions. Its role in circulation is to return excess fluid and proteins from the tissues to the bloodstream. The fluid carried in the lymphatic system is called lymph. Another function of the lymphatic system is to absorb digested fats from the small intestine These fats are then added to the blood near the heart. One other major function of the lymphatic system is to protect the body from impurities and invading microorganisms.

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Coronary heart disease (CHD) is a condition in which proper circulation of blood and oxygen are not provided to the heart and surrounding tissue. This result is due to a narrowing of the small blood vessels, which normally supply the heart with blood and oxygen. The typical cause of coronary heart disease is a condition known as atherosclerosis, which takes place with plaque and fatty build up on the artery walls, narrowing the vessels. Some more frequent symptoms of coronary heart disease include:

circulatory system循环系统英文

• • • • • • • • • • • • •
• systemic circulation
faintness abdominal distension and pain vomiting oliguria edama headache dizziness twitching
• Heart Vessels • Arteries and Veins • Ascending aorta Source, left ventricle of the
heart; branches:left and right coronary artery, continues as aortic arch;. • Left coronary artery Source, ascending aorta; branches：anterior interventricular branches and circumflex branches. • Right coronary artery Source, ascending aorta； branches：sinoatrial nodal branches, right marginal branches, posterior interventricular branches, atrioventricular nodal branches. • Coronary sinus formed by union of great cardiac vein and oblique vein of left atrium; tributaries:middle cardiac vein, small cardiac vein.
• Cardiac base
The cardiac base is primarily made up by the left atrium with a lesser contribution of the right atrium. Grooves There are three grooves on the surface of heart:the coronary sulcus, the anterior interventricular groove, the posterior interventricular groove.

Circulatory System 循环系统

Circulatory System 循环系统Circulatory System, or cardiovascular system, in humans, the combined function of the heart, blood, and blood vessels to transport oxygen and nutrients to organs and tissues throughout the body and carry away waste products. Among its vital functions, the circulatory system increases the flow of blood to meet increased energy demands during exercise and regulates body temperature. In addition, when foreign substances or organisms invade the body, the circulatory system swiftly conveys disease-fighting elements of the immune system, such as white blood cells and antibodies, to regions under attack. Also, in the case of injury or bleeding, the circulatory system sends clotting cells and proteins to the affected site, which quickly stop bleeding and promote healing.The human circulatory system is composed of the muscular heart and an intricate network of elastic blood vessels known as arteries, veins, and capillaries. These structures work together to circulate blood throughout the body, in the process delivering life-preserving oxygen and nutrients to tissue cells while also removing waste products. The heart, blood, and blood vessels are the three structural elements that make up the circulatory system. The heart is the engine of the circulatory system. It is divided into four chambers: the right atrium, the right ventricle, the left atrium, and the left ventricle. The walls of these chambers are made of a special muscle called myocardium, which contracts continuously and rhythmically to pump blood. The pumping action of the heart occurs in two stages for each heart beat: diastole, when the heart is at rest; and systole, when the heart contracts to pump deoxygenated blood toward the lungs and oxygenated blood to the body. During each heartbeat, typically about 60 to 90 ml (about 2 to 3 oz) of blood are pumped out of the heart. If the heart stops pumping, death usually occurs within four to five minutes.Blood consists of three types of cells: oxygen-bearing red blood cells, disease-fighting white blood cells, and blood-clotting platelets, all of which are carried through blood vessels in a liquid called plasma. Plasma is yellowish and consists of water, salts, proteins, vitamins, minerals, hormones, dissolved gases, and fats.Three types of blood vessels form a complex network of tubes throughout the body. Arteries carry blood away from the heart, and veins carry it toward the heart. Capillaries are the tiny links between the arteries and the veins where oxygen and nutrients diffuse to body tissues. The inner layer of blood vessels is lined with endothelial cells that create a smooth passage for the transit of blood. This inner layer is surrounded by connective tissue and smooth muscle that enable the blood vessel to expand or contract. Blood vessels expand duringexercise to meet the increased demand for blood and to cool the body. Blood vessels contract after an injury to reduce bleeding and also to conserve body heat.In an average healthy person, approximately 45 percent of the blood volume is cells, among them red cells (the majority), white cells, and platelets. A clear, yellowish fluid called plasma makes up the rest of blood. Plasma, 95 percent of which is water, also contains nutrients such as glucose, fats, proteins, and the amino acids needed for protein synthesis, vitamins, and minerals. The level of salt in plasma is about equal to that of sea water. The test tube on the right has been centrifuged to separate plasma and packed cells by density. Arteries have thicker walls than veins to withstand the pressure of blood being pumped from the heart. Blood in the veins is at a lower pressure, so veins have one-way valves to prevent blood from flowing backwards away from the heart. Capillaries, the smallest of blood vessels, are only visible by microscope—ten capillaries lying side by side are barely as thick as a human hair. If all the arteries, veins, and capillaries in the human body were placed end to end, the total length would equal more than 100,000 km (more than 60,000 mi)—they could stretch around the earth nearly two and a half times.The arteries, veins, and capillaries are divided into two systems of circulation: systemic and pulmonary. The systemic circulation carries oxygenated blood from the heart to all the tissues in the body except the lungs and returns deoxygenated blood carrying waste products, such as carbon dioxide, back to the heart. The pulmonary circulation carries this spent blood from the heart to the lungs. In the lungs, the blood releases its carbon dioxide and absorbs oxygen. The oxygenated blood then returns to the heart before transferring to the systemic circulation.Only in the past 400 years have scientists recognized that blood moves in a cycle through the heart and body. Before the 17th century, scientists believed that the liver creates new blood, and then the blood passes through the heart to gain warmth and finally is soaked up and consumed in the tissues. In 1628 English physician William Harvey first proposed that blood circulates continuously. Using modern methods of observation and experimentation, Harvey noted that veins have one-way valves that lead blood back to the heart from all parts of the body. He noted that the heart works as a pump, and he estimated correctly that the daily output of fresh blood is more than seven tons. He pointed out the absurdity of the old doctrine, which would require the liver to produce this much fresh blood daily. Harvey’s theory was soon proven correct and became the cornerstone of modern medical science.。

circulatorysystem循环系统英文资料实用PPT

Lymphatic System
The lymphatic system is a network of vessels that transport lymphatic fluid throughout the body, carrying away waste and helping to fight infections. It is also involved in immune function.
PVD can lead to problems with the circulation of blood to the arms, legs, and feet. Symptoms include pain or cramping in the legs, numbness, and skin changes.
removing carbon dioxide and other waste products.
Blood Vessels
01
Types
Blood vessels come in three types: arteries, veins, and capillaries.
02 03
Function
They transport blood throughout the body, delivering essential nutrients and gases to the cells and removing waste products.
Structure
Arteries and veins are thick-walled and elastic, while capillaries are tiny, thin-walled vessels that allow for the exchange of nutrients, gases, and waste products between the blood and the surrounding tissue.

血液循环系统英语作文

血液循环系统英语作文The Circulatory System。

The circulatory system, also known as thecardiovascular system, is an essential part of the human body. It is responsible for transporting oxygen, nutrients, and hormones to cells throughout the body, as well as removing waste products like carbon dioxide and other toxins. This system consists of the heart, blood vessels, and blood, and it plays a crucial role in maintaining the overall health and well-being of an individual.The heart is the central organ of the circulatory system. It is a muscular organ that pumps blood throughout the body, ensuring that all the cells receive the necessary nutrients and oxygen. The heart consists of four chambers: the left and right atria, and the left and right ventricles. The atria receive blood from the body and the lungs, while the ventricles pump blood out to the body and the lungs.The heart also has its own blood supply, provided by thecoronary arteries, which ensure that the heart muscle receives the oxygen and nutrients it needs to function properly.The blood vessels are the highways of the circulatory system, carrying blood to and from the heart and throughout the body. There are three main types of blood vessels: arteries, veins, and capillaries. Arteries carry oxygen-rich blood away from the heart to the rest of the body, while veins carry oxygen-poor blood back to the heart. Capillaries are tiny blood vessels that connect arteries and veins and allow for the exchange of oxygen, nutrients, and waste products between the blood and the body's cells.The blood itself is a complex fluid that carries out a variety of important functions in the body. It is made up of plasma, red blood cells, white blood cells, and platelets. Plasma is the liquid portion of the blood and carries nutrients, hormones, and waste products. Red blood cells are responsible for carrying oxygen from the lungs to the rest of the body, while white blood cells are part of the body's immune system and help fight off infections.Platelets are small cell fragments that play a crucial role in blood clotting, which is essential for preventing excessive bleeding when the body is injured.The circulatory system is a closed-loop system, meaning that the blood circulates continuously throughout the body. The process begins when the heart pumps oxygen-rich blood to the body's cells through the arteries. As the blood travels through the capillaries, oxygen and nutrients are exchanged for carbon dioxide and waste products. The oxygen-poor blood then returns to the heart through the veins, where it is pumped to the lungs to pick up more oxygen and release carbon dioxide. This cycle repeatsitself over and over again, ensuring that all the cells in the body receive the oxygen and nutrients they need to function properly.In addition to its role in delivering oxygen and nutrients to the body's cells, the circulatory system also plays a crucial role in maintaining the body's temperature and pH balance, as well as transporting hormones and other signaling molecules throughout the body. It also helps toregulate blood pressure and plays a vital role in thebody's immune response, helping to fight off infections and heal injuries.Maintaining a healthy circulatory system is essential for overall health and well-being. A balanced diet, regular exercise, and avoiding smoking and excessive alcohol consumption can help keep the circulatory system in good working order. It is also important to manage stress and get regular check-ups with a healthcare provider to monitor blood pressure, cholesterol levels, and other indicators of cardiovascular health.In conclusion, the circulatory system is a complex and essential part of the human body. It is responsible for delivering oxygen and nutrients to the body's cells, removing waste products, and maintaining the overall health and well-being of an individual. Understanding how the circulatory system works and taking steps to keep it healthy is crucial for living a long and healthy life.。

介绍循环系统作文英语初一

The human body is a marvel of engineering,with each system designed to perform specific functions that keep us alive and healthy. Among these,the circulatory system plays a crucial role in maintaining life by transporting nutrients,oxygen,and waste products throughout the body.This essay will explore the intricacies of the circulatory system,its components,and its vital functions.The circulatory system,also known as the cardiovascular system,is composed of the heart,blood vessels,and blood.It is a closed network that ensures the continuous flow of blood,delivering essential substances to cells and tissues while removing waste products.At the heart of the system is the heart itself,a muscular organ that pumps blood through the body.The heart has four chambers:two atria and two ventricles.The right atrium receives oxygenpoor blood from the body and sends it to the right ventricle,which then pumps it to the lungs to pick up oxygen and release carbon dioxide.This oxygenrich blood returns to the left atrium,from where it is sent to the left ventricle,and then pumped out to the rest of the body.Blood vessels are the highways of the circulatory system.There are three main types:arteries,veins,and capillaries.Arteries carry oxygenrich blood away from the heart,while veins return oxygenpoor blood back to it. Capillaries are the smallest blood vessels,allowing for the exchange of oxygen,nutrients,and waste products between the blood and the bodys cells.Blood,the life fluid of the circulatory system,is composed of plasma,red blood cells,white blood cells,and platelets.Plasma,the liquid component, carries nutrients,hormones,and waste products.Red blood cells,rich in hemoglobin,transport oxygen and carbon dioxide.White blood cells play a critical role in the immune system,defending the body against infections and diseases.Platelets are essential for clotting,preventing excessive bleeding when an injury occurs.The circulatory system is not only responsible for oxygen and nutrient delivery but also plays a role in temperature regulation.As blood flows through the body,it helps to distribute heat evenly,maintaining a stable internal temperature.This is particularly important in maintaining the delicate balance of body functions.Moreover,the circulatory system is integral to the immune response. White blood cells circulate throughout the body,identifying and neutralizing foreign invaders,such as bacteria and viruses.This constant surveillance helps to protect the body from illness and infection.Understanding the circulatory system is not just important for medical professionals but for everyone.It helps us appreciate the complexity of our own bodies and the remarkable processes that keep us alive.By recognizing the importance of a healthy circulatory system,we can make informed decisions about our lifestyle and habits,such as maintaining a balanced diet,engaging in regular exercise,and avoiding smoking,all of which contribute to a healthy heart and efficient circulation.In conclusion,the circulatory system is a vital and complex network that underpins our very existence.From the powerful beat of the heart to the delicate dance of blood cells,every component plays a crucial role in sustaining life.By appreciating the intricacies of this system,we can better understand the importance of taking care of our bodies and the steps we can take to ensure a healthy and vibrant life.。