Transcript Circulatory system

Circulatory system
Shiping Ding (丁世萍), Ph. D
School of Medicine, Zhejiang University
Learning Objectives
• To be familiar with the type of capillary.
• To be familiar with the type of artery and vein.
• To distinguish with all the types of blood
vessels.
Concepts of organs and systems
 Organ: composed of four kinds of the tissues
in a particular way
Types
Hollow organs: studied from inside to outside
parenchyma
Substantial organs:
interstitium
 System: composed of many organs which
have relationship with each other in
structure and function.
General outline
---Closed tubular system
According to the circulating
fluid in the tubes, blood or lymph:
•Blood vascular system
(cardiovascular system)
•Lymphatic vascular system
Cardiovascular System
The histological study of the cardiovascular system
includes two major components
• Heart – mainly functions as a pump to move blood
(and all the things blood carries) through the body.
• Blood vessels – are the tubes that distribute the
blood to the cells and then back to the heart.
The blood vessels include three major divisions:
Arteries –
deliver blood from heart to capillaries
Capillaries –
the smallest blood vessels and closest to
body cells, the interchanges between blood
and tissues occur there
Veins –
carry blood from body to the heart
Histological Structure of Blood Vessels
Structural feature of
Arteries and Veins:
Tunica intimae
1. Endothelium
2. Basal lamina
3. Subendothelial layer
(Internal elastic membrane)
Tunica media
Mainly smooth muscle
Tunica adventitia
Mainly connective tissue
medium-sized A
Artery
 transport blood from heart to capillaries
 according to their size, structure and function
are classified
Large artery
Medium-sized artery D>1mm
Small artery D>0.3~1mm
Arteriole D<0.3mm
Structure features of artery
• The wall of Arteries consist of three layers
or “coats” often referred to as tunics.
•
– Tunica intimae – is the inner coat
– Tunica media – is the middle layer
– Tunica adventitia or tunica externa is the
outer layer of the wall of the blood vessel
Layers of arteries wall differ in different size
blood vessels. The structure and function of
arteries change as their diameter decreases.
Tunica intimae
•
is the inner coat and it
consists of
1)inner endothelial layer
2)subendothelial layer: a layer
of loose connective tissue
3)internal elastic membrane
(often very distinct)
•
This layer is relatively
constant within different size
arteries.
Tunica media
• This layer makes up the greatest part of the wall of the
artery.
• It is comprised primarily of smooth muscle.
• In small arteries or arterioles it may be only 1-3 cells thick
but in larger arteries may comprise hundreds of layers of
muscle cells.
• In larger arteries, there in increased amounts of elastin
fibers.
Tunica adventitia
• This is the outer layer of the wall of the artery.
• It consists primarily of connective tissue and serves to
attach the blood vessel into the surrounding connective
tissue.
• Often contains adipose tissue and often contains blood
vessels (vasa vasorum) that supply the walls of the blood
vessels.
Medium-sized artery:
 muscular artery: diameter larger than 1mm
Tunica intima
Endothelium
Subendothelial layer: LCT
Internal elastic lamina: clear
Tunica media: contain 10~40 layers of circular
smooth muscle
Tunica adventitia
External elastic lamina
LCT: contain vasa vasorum
Smooth muscle regulates blood flow and pressure.
Medium-sized artery
Tunica
Adventitia
Tunica
Media
Tunica
intima
Medium-sized artery
Classic muscular artery- elastic stain
Large (elastic) artery:
 contains aorta, the pulmonary
trunk and their main branches
With a large lumen relative to
wall thickness
 subendothelial layer is thicker
with a few smooth muscles
 tunica media is thick, contains a
40-70
concentrically-arranged
elastic lamina
 internal and external elastic
lamina are not distinguished
 tunica adventitia are thinner,
abundant vasa vasorum
PT stain
Elastic artery
Muscular artery
Small artery:
 muscular artery and peripheral resistance vessel
 internal elastic lamina is clear, while
external elastic lamina is not distinguished
 the tunica media contains 3~9 layers of smooth muscles
Arterioles:
Less than 0.5mm in
diameter. Have similar and
simpler structure as that of
muscular artery.
Several layers of smooth
muscle in tunica media.
Responsible
for
the
presence of blood pressure.
Vein
 large lumen, thin wall,
irregular
 internal and external
elastic lamina are not clear
 tunica media is thin, with
a few elastic fibers and
smooth muscles
 tunica adventitia is thick
(best-developed)
 some veins have valves
large veins
Medium-sized vein
Arteriole (b) and venule (a)
Vein valves: Bag-like protrusion of
tunica intima, which prevents the
blood flow from running to opposite
direction. Exists only in the vein that
has low position or far away from
heart.
Muscular vein with valve
Vein with valve
A Comparison of a Typical Artery and a Typical Vein
Artery, vein, nerve, elastin stain
Artery, vein, nerve, elastin stain
Artery, vein, nerve, trichrome stain
Capillaries
• Capillaries are the site where materials carried in the
blood are unloaded and other materials are loaded into the
blood.
• In many organs the capillaries form a network.
• Consist of a single layer of simple squamous epithelium.
the average diameter about 8um.
Capillary: Thinnest, simplest, largest, longest and most widely
distributed. Connects the arteries and veins.
Stomach, vascular injection of mucosa
Renal vasculature, vascular dye injection
Capillaries
1) LM:
• A single layer of
endothelial cells
• A basement membrane
• pericyte:
Capillary(b) and venule(a)
Capillary in heart(B)
Pericyte:
long cytoplasmic processes
have a contractile function, participating in the repair process
Capillary - pericyte
 EM
According to the appearance of the endothelium
and basement membrane:
•Continuous capillary
•Fenestrated capillary
•Sinusoid
Capillaries
Continuous C.
Fenestrated C.
Sinusoid
Continuous capillary:
 distributed in muscle tissue, brain, lung and
connective tissue, etc.
 endothelial cell: large number of pinocytotic
vesicles, cell junctions between the endothelia
(tight junction), no pores, no gaps
 basement membrane: integrity
(stripe)
Continuous capillary
* Endothelia contain
special
tubular
organelle, the WeibelPalade (WP) bodies,
which release Factor
VIII related antigen to
facilitate blood clotting
when blood vessels
break. Endothelia also
contains
some
enzymes, such as
EDRF,etc.
* WeibelPalade body
Fig. Of EM
Fenestrated capillary:
 distributed in tissues where rapid
interchange of substances occurs
between the tissue and the blood, as
in the kidney glomerulus, mucosa
of gastrointestine, some endocrine
glands
 endothelial
cells:
present
abundant perforated pores (6080nm in D, with 4-6 nm
diaphragm), have
or haven’t
diaphragm on them
 basal lamina: continuous
Fenestrated
capillary
Fenestrated capillary (kidney)
Sinusoid
 distributed
in
tissues
where
interchange of substance in big size
occurs, as in the liver, spleen, and some
endocrine glands
 a greatly enlarged diameter (30~40um)
 endothelial cell: intercellular clefts are
large between cells, many pores without
diaphragm
 absence of a continuous basement
membrane
macrophages are located either among
or outside the cells of the endothelium
Sinusoid
Heart
 a hollow muscular organ that contracts
rhythmically
 pump blood through the circulatory system
The wall of heart
 epicardium
 myocardium
 endocardium
The wall of heart
E
SE
endocardium
subendocardial layer
Purkinje fibers
myocardium
epicardium
endocardium
Endothelium
Subendothelial layer: fined CT
Subendocardial layer: LCT,
blood vessels, nerves and the
impulse-conducting system of
the heart
Purkinje cell
Cardiac cell
Purkinje cells both broader and shorter than
ordinary cardiac muscle fibers, rich in
sarcoplasm, two nuclei can be found, welldeveloped intercalated disks.
Conducting System
components:
sinoatrial node (SA node):
the primary pacemaker of the heart
located in epicardium of right atrium
atrioventricular node( AV node)
bundles( AV bundles) located in
subendocardial layer.
network of Purkinje fiber
Impulse generating and conducting
system of the heart:
 Pacemaker cells: heartbeat generating
Transitional cells: transmit impulse
 Purkinje cells (bundle cell):
distributed in subendocardial layer.
three types of cells
a. pacemaker cell( P cell):
• mainly distributed in SA and AV node
• small, fusiform or polygonal in shaped
• enclosed by DCT
• less organelle: myofibril, plasmalemmal
vesicles and more glycogen
b. transitional cell:
• mainly distributed in periphery of SAN or
AVN and AV bundle
• The structure is between pacemaker cell and
cardiac M
• thinner and shorter than CM
• more myofibril than P cell
c. Purkinje cell:
• mainly constitute AV bundle and branches
• shorter, boarder than CM, with 1-2 centrally
located nuclei
• rich in mitochondria, glycogen, less myofibril
• well-developed intercalated disks
myocardium thickest layer, consists of cardiac muscle, is
richly supplied with capillaries
three layers are divided roughly, cardiac
muscle arrange spirally.
闰盘
线粒体
epicardium
LCT: contain adipose cells, blood vessels and
nerves
Methothelium
构成心包脏层
心包受损
影响心脏功能
The core of dense connective tissue
心瓣膜
cardic valve
endothelium
prevent the back
flow of blood
Lymphatic vascular system
(Study by yourself)
Lymphatic capillaries
Lymphatic vessel
Lymphatic ducts
VII. Lymph vessels:
A. Lymph enters the blood
via right lymphatic duct
and thoracic duct.
B. Lymph vessels have
larger lumen, thinner wall
and are more permeable,
compared with the vein of
the same grade.
C. Lymph comes from the
tissue fluid. Lymph
capillaries locate in CT
and have blind ends.
Lymph vessels
• Lymph vessels return fluid from tissues to
circulatory system.
• Depend upon muscles to move fluid
• Very thin walled.
lymphatic
Lymphatic with valve
Question
1. To describe the difference between
large artery and medium-sized artery.
2. To describe the types of capillary.
Good-bye!
Thank you for your attention!