级临床医学循环系统

第10章循环系统Circulatorysystem—心脏的组织结构心内膜endocardium：内皮endothelium（单层扁平上皮）内皮下层subendothelial

layer又分内、外两层内层含细密纤维和散在分布的平滑肌外层（又称心内膜下层subendocardiallayer）含心脏传导系统、小血管、神经纤维,心肌膜myocardium肌纤维大致按内纵、、外斜螺旋排列.肌纤维间有丰富毛细血管和少量结缔组织心骨骼cardiac

skeleton心房钠尿肽的产生和降血压作用心外膜epicardium是心包膜的脏层,

为浆膜结构,

分布有血管、神经、脂肪组织.心瓣膜cardiac

valve瓣膜的作用为定向分

液,瓣膜内的胶原纤维如出现病理性增生可导致心瓣膜疾病.二心脏传导系统心脏传导系统组成由特殊的心肌纤维组成按收缩节律的传导顺序：窦房结、结、

束、左右

束及分支分布：窦房结位于心外膜,其它部分位于心内膜下层.组成传导系统的三种细胞起搏细胞pacemakercell

位于窦房结该细胞的作用是激发心肌节律移行细胞transitional

cell

位于窦房结、结及束能传导起搏细胞发出的兴奋野纤维Purkinje

cell

较普通心肌纤维粗

位于

束及其分支将兴奋传递至各外心室肌动脉结构动脉管壁的一般结构内膜中膜外膜一、大动脉large

artery又称弹性动脉elastic

artery1内膜tunica

intima内皮

W-P小体与vWF因子的生理作用内皮下层少量胶原纤维和平滑肌纤维中膜tunica

media主要由几十层弹性膜组成,弹性膜间有平滑肌细胞和胶原纤维,基质的主要化学成分为硫酸软骨素.外膜tunica

adventitia由疏松结缔组织构成,含营养血管二、中动脉medium-sized

artery又称肌性动脉muscular

artery内膜:内弹性膜（中、小动脉的标志性结构)中膜:数十层平滑肌.肌纤维间有弹性纤维和胶原纤维.外膜:疏松结缔组织构成.与外膜交界外有外弹性膜.三、小动脉small

artery管径为0.3-1mm,结构与中动脉相似,随管径变细,肌层减少,内弹性膜变薄.四、微动脉arteriole管径在0.3mm以下,中膜由1-2层平滑肌组成,内弹性膜各级动脉血管对血压的影响大动脉管壁弹性结构的弹性回缩能保持血流的连续性舒张压形成的主要因素中动脉分配、调节进入各器官系统的血液流量小、微动脉能影响有效循环血量的外周阻力（与心室收缩一起决定收缩压的高低）毛细血管capillary毛细血管的结构:内皮基膜周细胞pericyte周细胞位于内皮和基膜之间,胞质含肌动蛋白丝、肌球蛋白,有收缩功能,并能增殖分化为内皮细胞和成纤维细胞毛细血管的分类:连续毛细血管continuous

capillary有孔毛细血管fenestrated

capillary血窦sinusoid

capillary静脉Vein静脉也分为大、中、小、微四级管壁结构内膜、中膜、外膜三层与动脉的不同之处：管壁结构变异大,界限不如动脉明显,平滑肌和弹性组织不如动脉丰富,管壁较薄,管腔切面多不规则,较大静脉常有静脉瓣.各级静脉的结构微静脉venule管径0.2mm以下,管腔较毛细血管大,管壁结构与毛细血管相似,也有物质交换功能.小静脉small

vein管径0.2mm以上,内皮外有1-数层平滑肌,外膜开始出现.3中静脉medium-sized

vein管径2-9mm,内、外弹性膜不明显中膜的平滑肌排列较松散,外膜较厚,并可能有纵行平滑肌纤维分布.大静脉large

vein内膜较薄,中膜平滑肌排列松散,外膜较厚,可见成束的纵行平滑肌.静脉瓣由内膜凸入管腔形成The

cardiovascularsystem,

except

forthe

capillaries,sharecommon

structuralfeatures.

The

walls

of

blood

vesselsarecomposedofthreelayers;the

tunicaintima,thetunicamediaandthetunicaadventitia.

Inthe

heart,the

threelayersare

termed ocardium,

themyocardium

and

the

epicardium.The

heart

is

a

hollowmuscular

organ.ocardium

consists

of

threelayers;othelium,thesubendotheliallayerandthesubendocardium.Thebranches

ofthe

impulse-conducting

system

of

theheart(purkinjefibers)

canbeseeninthesubendocardium.dMyocardium

is

the

thickest

of

thetunics

of

the

heart.

Itis

richlywith

capillaries.

The

cardiac

musclecells

are

arranged

roughly

into

the

innerlongitudinal

layer,

the

middle

circularlayer

and

the

outer

oblique

layer.

Theepicardium

is

a

serous

membrane.Arteries

can

be

classified

accordingtotheir

sizes

into

four

groups;large,medium-sized,smallandarterioles.Since

the

change

in

size

andcorresponding

structure

of

the

arteriesare

usually

gradual,no

clearlydefinedlimits

exist

between

different

groups

ofarteries.

The

large

arteries

belong

to

theelastic

arteries,

because

they

contain

alarge

number

of

elastic

membranes

intheirwalls.Exceptforthe

largearteries,mostofthenamedarteriesinthehumanbody

belongto

the

medium-sized

arteries.

These

have10-40layersofconcentricallyarrangedsmoothmusclecellsintheirmedia;hencetheyaretermedmusculararteries.Capillarieshavethesimplest

structure,their

wall

only

consists

of

a

layer

ofendothelial

cells,

a

basallamina

andpericytes

with

long

cytoplasmic

processesthat

partially

surround

othelialcells.

The

capillaries

can

be

classified

intothree

types;

continuous,

fenestrated

anddiscontinuous

sinusoidal.In

contrast

to

their

correspondingarteries,

veins

possess

the

followingfeatures;(a)they

havealargediameterand

thinner

walls

than

their

panyingarteries;(b)theboundaries

betweenthethree

tunics

of

vein

walls

are

not

as

clearas

in

arteries,

because

the

inner

andexternalelasticmembranesare

o