General Histology Lec 3: The Circulatory System PDF

‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ lec 3 The Circulatory System Is the main transport system in which substances are carried from one part of the body to another in a variab...

‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ lec 3 The Circulatory System Is the main transport system in which substances are carried from one part of the body to another in a variable size tubes called vessels. We have: Blood circulatory system: in which 02, CO2, nutrients, cells of immune system, hormones,...etc. are transported to various parts of the body. The Blood Circulatory System is formed of the following structures Heart: to pump the blood. Arteries: series of vessels that carry blood from the neart to the tissues and they become smaller and smaller as they branch until they end in the capillaries. Capillaries: diffuse network of thin tubules that anastomose with each others & through their wall the exchange of 02 & nutrients between blood & tissues occur. by gabs Veins: series of vessels that will carry blood from the tissues to the heart In general the Blood Circulatory System is divided into: Macrocirculation: vessels more then 0.1 mm. in diameter. Microcirculation. vessels only visible by microscope 1  ‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ General structure of blood vessels The walls of all the blood vessels are composed of three identifiable layers named: tunica intima, tunica media, tunica adventitia. (tunica = coat ‫)طبقة أو غالف‬  ‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ In the smallest blood vessels (capillaries & venules) these 3 tunics are greatly simplified. There are no absolute criteria to distinguish between large arteries, medium size arteries and arterioles because blood vessels constitute a continuous system. generally the basis of classification are the size and tissue composition of the vessel. Tunics of the blood vessel wall Tunica Intima: consist of a layer of highly specialized cells called endothelial cells that line the vessel's interior surface, These cells rest on a basal lamina  ‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ Beneath these cells is the sub endothelial layer which consist of loose connective tissue that may contain some smooth muscle cells. In arteries the T. intima is separated from the T. media by the internal elastic lamina (membrane) which is composed of elastic fibers & has fenestrae (gabs) that allow substances to diffuse and nourish the deeper cells in the blood vessel wall, this membrane is very obvious in the muscular arterjes and bajenent arterioles.  ‫ فردوس حميد عبو‬.‫د‬ ‫مدرس مساعد‬ ‫جامعة الحدباء كلية طب االسنان‬ The intima often appears wrinkled in section due to contraction of the smooth muscle cells present in the subendothelial layer (particularly true in arteries).