Cardio Vascular System Lecture 2 PDF

BLOCK CAS-206 Cardio Vascular System Lecture 2 General structure of blood vessels Ass. Prof. Dr. Safaa Said Department of Histology &Cell Biology Assuit University  Learning  After this lecture, students sh...

BLOCK CAS-206 Cardio Vascular System Lecture 2 General structure of blood vessels Ass. Prof. Dr. Safaa Said Department of Histology &Cell Biology Assuit University  Learning  After this lecture, students should be able to: objectives  Mention the general structure of blood vessels.  Recognize the different parts of the blood vessel wall.  Discuss the normal structure of endothelial cells.  Discuss the function of endothelial cells.  General structure of blood vessels: All blood vessels larger than capillaries have three layers: tunica intima, tunica media, and tunica adventitia. 1. Tunica intima, which lies next to the lumen, is the inner most layer. It is composed of: a. simple squamous epithelium (endothelium) , b. subendothelial C.T.& c. Internal elastic lamina. 1. Tunica media, the middle layer. Composed of helically arranged smooth muscle cells with some elastic and collagen fibers interspersed between them. An external elastic lamina between tunica media &tunica adventitia Capillaries &postcapillary venules do not have a tunica media, in these small vessels pericytes replace the tunica media. 1. Tunica adventitia (the outermost layer). It is usually continuous with the surrounding C.T. It is composed of ordinary C.T. containing fibroblast, Collagen and elastic fibers. Vasa vasorum Like the heart, larger blood vessels receive a blood supply from outside their structure through a system of small vessels called the vasa vasorum. Vasa vasorum are more found in the walls of veins than arteries.  Endothelial cell This specialized simple squamous epithelial cell lines the endocardium of the heart, lines all the arteries and veins, and makes up all the capillaries The endothelial cells rest on a basal lamina. These flattened polygonal cells are elongated in the direction of blood flow. The nucleus causes the cell to bulge into the capillary lumen. The cytoplasm contains few organelles including a small Golgi complex, mitochondria, free ribosomes & a few cisternae of RER. Endothelial cells are connected to each other by tight junctions. Functions of endothelial cells: 1.They provide smooth surface. 2.They secrete collagen, lamin, endothlin and nitric oxide. 3.They have membrane bound enzymes for bradykinin, serotonin, prostaglandins, thrombin, norepinephrin and lipoprotein lipase. REFERENCES: JUNQUEIRA’S BASIC ELSEVIER’S INTEGRATED HISTOLOGY (TEXT AND ATLAS) HISTOLOGY (2007) 1ST EDITION. (2018) 15 TH EDITION.