Circulatory system

General outline Blood vascular system (cardiovascular system)Blood vascular system (cardiovascular system) Lymphatic vascular systemLymphatic vascular system According to the circulating fluid in the tubes, blood or lymph:

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. 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. 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 – carry blood from heart to body carry blood from heart to body Capillaries – the smallest blood vessels, the interchanges the smallest blood vessels, the interchanges between blood and tissues occur there between blood and tissues occur there Veins – carry blood from body to the heart carry blood from body to the heart

Capillaries Capillaries are the site where materials carried in the blood are unloaded and other materials are loaded into the blood. 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. In many organs the capillaries form a network. Consist of a single layer of simple squamous epithelium. the average diameter about 8um. Consist of a single layer of simple squamous epithelium. the average diameter about 8um.

Capillaries 1) LM: A single layer of endothelial cells A basal lamina pericyte:

Pericyte: long cytoplasmic processes long cytoplasmic processes have a contractile function, participating in the repair process have a contractile function, participating in the repair process

According to the appearance of the endothelium and basal lamina: Continuous capillaryContinuous capillary Fenestrated capillaryFenestrated capillary SinusoidSinusoid EM  EM

Capillaries Continuous C. Fenestrated C. Sinusoid

Continuous capillary:  distributed in muscle tissue, brain, lung and connective tissue, etc. connective tissue, etc.  endothelial cell: large number of pinocytotic vesicles, no pores, exist cell junctions vesicles, no pores, exist cell junctions between the endothelia(tight juntion) between the endothelia(tight juntion)  basal lamina: integrity

(stripe)

Continuous capillary

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  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 pores, have or haven’t diaphragm on them  endothelial cells: present abundant pores (60-80nm in D, with 4-6 nm diaphragm), have or haven’t diaphragm on them  basal lamina: continuous

Fenestrated capillary

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

Structural feature of Arteries and Veins: Tunica intima 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 Large artery Medium-sized artery D>1mm Small artery D>0.3~1mm arteriole are classified

The wall of Arteries consist of three layers or “coats” often referred to as tunics. The wall of Arteries consist of three layers or “coats” often referred to as tunics. – Tunica intima – 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. Layers of arteries wall differ in different size blood vessels. The structure and function of arteries change as their diameter decreases. Structure features of artery

Tunica intima is the inner coat and it consists of is the inner coat and it consists of 1) inner endothelial layer 1) inner endothelial layer 2) subendothelial layer: a layer of loose connective tissue 2) subendothelial layer: a layer of loose connective tissue 3) internal elastic membrane (often very distinct) 3) internal elastic membrane (often very distinct) This layer is relatively constant within different size arteries. This layer is relatively constant within different size arteries.

Tunica media This layer makes up the greatest part of the wall of the artery. This layer makes up the greatest part of the wall of the artery. It is comprised primarily of smooth muscle 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 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. In larger arteries, there in increased amounts of elastin fibers.

Tunica adventitia This is the outer layer of the wall of the artery. 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. 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. 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  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 smooth muscle Tunica adventitia External elastic lamina LCT: contain vasa vasorum

Smooth muscle regulates blood flow and pressure.

TunicaAdventitiaTunicaMediaTunicaintima Medium-sized artery

Large artery:  contains aorta, the pulmonary trunk and their main branches  elastic artery  subendothelial layer is thicker with a few smooth muscles smooth muscles  tunica media is thick, contains a concentrically- arranged elastic membrane arranged elastic membrane  internal and external elastic lamina are not distinguished  tunica adventitia are thinner, abundant vasa vasorum

Large artery

Elastic artery Muscular artery

Small artery:  muscular artery and peripheral resistance vessel vessel  internal elastic lamina is clear, while external elastic lamina is not distinguished external elastic lamina is not distinguished  the tunica media contains 3~9 layers of smooth muscles muscles

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 smooth muscles  tunica adventitia is thick(best-developed)  many veins have valves

Medium-sized vein

Heart  a hollow muscular organ that contracts rhythmically rhythmically  pump blood through the circulatory system system

The wall of heart endocardium  endocardium Endothelium Subendothelial layer: fined CT Subendocardial layer: LCT, blood vessels, nerves and the impulse-conducting system of the heart  myocardium: thickest layer, consists of cardiac muscle, is richly supplied with capillaries richly supplied with capillaries epicardium  epicardium LCT: contain adipose cells, blood vessels and nerves nervesMethothelium

The wall of heart E SE subendocardial layer endocardium myocardium epicardium Purkinje fibers

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) network of Purkinje fiber located in subendocardial layer

Impulse generating and conducting system of the heart: Pacemaker cells: heartbeat generating  Pacemaker cells: heartbeat generating  Transitional cells: transmit impulse distributed in subendocardial layer, both broader and shorter than ordinary cardiac muscle fibres, rich in sarcoplasm, two nuclei can be found,well-developedintercalateddisks. distributed in subendocardial layer, both broader and shorter than ordinary cardiac muscle fibres, rich in sarcoplasm, two nuclei can be found, well-developed intercalated disks. Purkinje cells (bundle cell):  Purkinje cells (bundle cell):

Purkinje cell Cardiac cell

Lymphatic capillaries Lymphatic vessel Lymphatic ducts Lymphatic vascular system (Study by yourself)

Lymph vessels Lymph vessels return fluid from tissues to circulatory system. Lymph vessels return fluid from tissues to circulatory system. Depend upon muscles to move fluid Depend upon muscles to move fluid Very thin walled. Very thin walled.