Chapter 8 Circulatory system Teacher ： Huang Ju-en ( 黄巨恩 ) Dept.of Histology and Embryology

1.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 Substantial organs:  System: composed of many organs which have relationship with each other in structure and function. parenchyma interstitium

heart lymphatic duct vein artery lymphatic vessel capillary lymphatic capillary tissue fluid 2.Composition of circulatory system  Cardiovascular system  lymph vascular system

heart artery capillary vein

一、 Composition of blood vessel and their general structures  Tunica intima  Tunica media  Tunica adventitia Endothelium Internal elastic M. Subendothelium

1.Intima Distribution 、 morphology (1)Endothelium Face the lumen and belong to squamous Model of endothelium of blood vessel

Weibel- Palade body Fig. Of EM

(2)Subendothelial layer Located beneath the endothelium Composed of thinner layer of C.T containing small amount of collagenous fibers,elastic fibers or some smooth muscle (3)Internal elastic membrane Internal elastic membrane is composed of elastic protein and there exist many fenestrations on it. It is wave-like and serve as a border between intima and media of artery.

2. Media Located between Intima and adventitia Composition Function Large A. ——elastic M. medium A. —— Smooth M. Dilate and retract blood vessels, Maintain tension of blood vessels Thickness depend on different kinds of blood vessels

3.Adventitia Distribution Thickness Composition outermost 、 thicker adventitia L.C.T containing fibroblast, collagenous F., elastic F. and external elastic membrane

nucleus Intercalated disc Cardiac muscular fiber Heart The wall is thickest and consist of largely cardiac muscle

 heart 1. The structure of heart wall endocardium ： endothelium, subendothelial layer, subendocardial layer. myocardium ： three layers are divided roughly, cardiac muscle arrange spirally. epicardium ： plasma membrane, mesothelium on the surface

Intercalated disc

Mesothelium Adipose tissue Tunica adventitia

2 ． Heart conducting system  Definition ： This system is composed of specific cardiac muscle fibers that can generate and conduct impulses to all parts of the heart, making heart contraction in rhythm.  Types of cell ： pacemaker cell, transitional cell, Purkinje fiber.  ※ cardiac skeleton── A supporting structure, locating between atrial muscle and ventricular muscle and consisting of DCT. It is a frame of heart and provide a attachment for cardiac muscle and cardiac valve. ※ cardiac valve──The thin-scalloped structure, formed by endocardium protruding into cavity of heart.

Endothelium The core of dense connective tissue Valve Endocardium

 Arteries （ Artery ， A ） 1. Grade ： large A ： Φ >10 mm medium-sized A ： Φ 1 ─ 10mm small A ： Φ 0.3 ─ 1mm arteriole ： Φ <0.3 mm. 2. Characteristics of various arteries :  large A （ elastic A ）： Conducting A.  Medium-sized A （ muscular A ）： Distributing A.

(1) Subendothelial layer: is thicker. There not only are many layers of internal elastic membrane outsides, but also confused together with elastic membrane of middle membrane. As a result, layering of large A are not as clear as medium-size A. (2) Middle tunic: consist mainly of elastic membrane of 40 ～ 70 layers, with occasional smooth muscle cells, elastic fibers and collagen fibers among elastic membranes. Major components of ground substance are chondroitin sulfate. (3) External tunic ： This is a thin layer of connective tissue and there is not obvious border with enveloping connective tissue. External elastic membrane is not obvious. Features of large A

Elastic M. Smooth Muscle Intima Media Adventitia Large Artery

（ 1 ） Layering clearly. internal elastic membrane is integrate （ 2 ） Middle tunic consist of smooth muscle of 10 ～ 40 layers, intermixing with elastic fibers, collagenous fibers and ground substance. （ 3 ） Thickness of external tunic equal middle and often there is obvious external elastic membrane between two tunic. Features of medium-side A external tunic Middle tunic

3 ． Small A ： They are also muscular A but layering is not clear. Smooth muscle is small. There is no external elastic membrane. 4 ． Arteriole ： layering is not more clear. There is only one or two layers of smooth muscle Arteriole Small A. Small V

 Capillary (Cap.) 1.Distributions ： broadly and have a relation with metabolism. Size ： Cap. generally is 6 ～ 8 μ m, but some sinusoid can reach 40 μ m in diameter. 2.General structures ： ① endothelia ② basal membrane ③ pericytes ： The flat-thin cells with processes between endothelium and basal membrane. ④ small amounts of connective tissues

3.Classifications and their EM structures ：  continuous cap. ：  fenestrated cap. ：  sinusoid （ sinusoidal cap., discontinuous cap. ）： 4.The structural bases of substance interchange of cap. ： （ 1 ） Larger square, thin vascular wall, short distance with surrounding cells. （ 2 ） O 2 、 CO 2 and lipid-soluble substances can penetrate the walls of cap. directly. （ 3 ） liquid and macromolecule can pass through endothelial pores. （ 4 ） pinocytotic vesicles can transport liquid. （ 5 ） intercellular space facilitate more easily elements to pass through. （ 6 ） basal membrane make small molecular substances filtrate readily, so disintegrate basal membrane or no is easier to material exchanges. 5. Capillary permeability: The ability of substances passing through capillary.

continuous cap. fenestrated cap. sinusoid Classifications and ultrastrutural feature of Cap.

Pore Pinocytotic vesicle

pore Endothelium pinocytotic (plasmalemmal) vesicles Basal membrane Intercellular space RBC sinusoid

 Vein, V 1.structural characteristics ： ① internal and external elastic membrane both are unclear ② The thickness of external tunic> middle tunic ③ large and irregular lumens, thin walls. 2.Vein valves ： Internal tunic of veins (their diameter usually are over 2 mm) protrude into lumens and form pleats, in the center of which connective tissue containing elastic fibers exist, but endothelia overlap on the surfaces. 3.Microcirculation 1 ． Definition ： The blood circulation of micro-small blood vessels between arterioles and venules 2 ． Compositions ： arterioles, precapillary arterioles, metaarterioles, true capillaries, short cuts, arteriovenous anastomosis and venules.

Questions 1.By comparison, what are the same and different items among larger, medium-side and small arteries in the structures of vessel walls? Try to describe the relationships between the structures and functions of blood vessels 2. How to distinguish arteries and veins under LM? 3.How to distinguish the surface of endocardium from that of epicardium under LM? 4.Try to describe the general characteristics of structures of capillaries. What are structural and functional features for each kind of capillaries respectively?

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