Blood Vessels PDF

BLOOD vessels Dr. Dalia Eita  Agenda ❑ Types of blood vessels ❑ Structure of large arteries ❑Structure of medium sized arteries and veins  ILOs ❑ Differentiate between types of blood vessels ❑ Identify structure of large arteries ❑ Identify structure of medi...

BLOOD vessels Dr. Dalia Eita  Agenda ❑ Types of blood vessels ❑ Structure of large arteries ❑Structure of medium sized arteries and veins  ILOs ❑ Differentiate between types of blood vessels ❑ Identify structure of large arteries ❑ Identify structure of medium sized arteries and veins THE BLOOD CIRCULATORY SYSTEM The vascular system consists of: 1. The heart 2. Blood vessels  ARTERIO- Arteries Veins VENOUS CONNECTION Large arteries: Large veins: Blood Aorta Inferior vena capillaries cava Medium sized Medium-sized Blood arteries veins Sinusoids Arterio-venous Arterioles Venules anastomosis (A-V shunts) Wall of Blood vessels Tunica Tunica Tunica intima media adventitia Inner outer Middle most most  Blood vessels Endothelial lining: simple squamous epithelium Subendothelial layer: loose C.T. rich in elastic fibers Tunica Internal elastic lamina (arteries) fenestrated band of elastic fibers intima Smooth muscle cells. Elastic fibers. Tunica Collagenous and reticular fibers. media Collagen fibers (type I). Elastic fibers. Tunica Tiny blood vessels called Vasa Vasorum adventitia vasa vasorum ("vessels of the vessel"), which consist of arterioles, capillaries, and venules in the tunica adventitia and the outer part of the media. The vasa vasorum provide metabolites to cells of those layers, since in larger vessels the wall is too thick to be nourished solely by diffusion from the blood in the lumen. Luminal blood alone does provide nutrients and oxygen for cells of the tunica intima. Since they carry deoxygenated blood, large veins typically have more vasa vasorum than arteries. NO ELASTIC FIBERS IN VEINS MEDICAL APPLICATION ❖ The endothelium has an antithrombogenic action, preventing blood coagulation. ❖ Endothelial cells are damaged by atherosclerotic lesions induces the aggregation of blood platelets. ❖ A thrombus is formed that may grow until there is complete obstruction. ❖ From this thrombus, solid masses called emboli may detach and be carried by the blood to obstruct distant bl. vessels  Large ARTERIES: Aorta Characters: Thick walls and wide lumen. Their media are rich in elastic fibers. -About 1/6 of the thickness of the wall. -The intima is thicker than intima of a muscular artery. Tunica -The subendothelial layer is thick and rich in elastic fibers. intima The internal elastic lamina is present but not easily seen. - It is very thick and forms the main thickness of the wall. - It contains fenestrated elastic laminae. Tunica - In between the elastic laminae, smooth muscle cells, reticular fibers, collagenous media fibers and ground substance. Relatively thin layer Tunica Collagen fibers & elastic fibers. adventi Vasa Vasorum lymphatics, and nerves are also present tia Aorta  Tunica intima Tunica media Tunica adventitia Medium-sized arteries and veins Medium-sized artery Medium-sized vein Wall: Thick wall. Thin wall. Lume Narrow round lumen Wide collapsed lumen n: Does not contain blood after Usually contains blood after death. death. No valve in the lumen. Valve present. T. Thick. Thin. intim Internal elastic lamina is Internal elastic lamina is a: well developed. absent.  Medium-sized artery Medium-sized vein T. media: Thick. Thin. Formed of smooth muscle fiber and elastic Formed of few smooth muscle fibers. fibers. No external elastic lamina. External elastic lamina may be present between the media and adventitia. T. adventitia: Thinner than media Thicker than the media contains elastic and collagenous fibers. contains collagenous fibers only. No lymphatic capillaries present in it. Lymphatic capillaries may be present. Flow of Blood: It has a rapid flow of arterial blood. It has a slow flow of venous blood. Medium-sized arteries with specialized characters: 1. Basilar (cerebral) artery: site: in the brain. Character: - Has thin wall and wide lumen. - Its internal elastic lamina is very thick. - It has no elastic fibers in the media. - Its media and adventitia are thin. Coronary artery: - Supplies the heart with blood. - Its wall is like medium sized artery but it differ in the subendothelial layer of its intima which contains: - Amorphous intercellular substances. - Smooth muscle fibers longitudinally arranged. - Fat droplets and monocytes. - There is external elastic lamina between the media and adventitia. Umbilical artery: Site: Present in the umbilical cord. Characters: - Carry venous blood. - Has no internal elastic lamina. - The media is formed of inner longitudinal and outer circular layer of smooth muscle fiber. - Adventitia is formed of mucoid C. T. called Wharton’s Jelly. MEDICAL APPLICATION When the tunica media of an artery is weakened by an embryonic defect, disease, or lesion. dilatation an aneurysm. Rupture of the aneurysm brings severe consequences and may cause death.  Venules Arterioles The immediate postcapillary venules are The small branches of the arteries. similar structurally to capillaries, with pericytes, but range in diameter from 15 to 20 Their diameter is less than 0.1mm. μm. These venules converge into larger collecting venules that become surrounded by tunica media with two or three smooth muscle layers and are called muscular venules. Dr. Dalia Eita References ▪ Junqueira LC, Carneiro J: Junqueira’s Basic Histology. Text and Atlas, fourteenth edition, Copyright © 2016 by McGraw-Hill Education. ▪ Student medical histology book, Mansoura university.