Cardiovscular System Vascular System and development

Vascular System 0 Transport blood to the tissues and back 0 Carry blood away from the heart 0 Arteries 0 Arterioles 0 Exchanges between tissues and blood 0 Capillary beds 0 Return blood toward the heart 0 Venules 0 Veins

Blood Vessels

Differences Between Blood Vessels 0 Walls of arteries are the thickest 0 Lumens of veins are larger 0 Larger veins have valves to prevent backflow 0 Skeletal muscle “milks” blood in veins toward the heart 0 Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue

Fetal Circulation 0 Fetus receives exchanges of gases, nutrients, and wastes through the placenta 0 Umbilical cord contains three vessels 0 Umbilical vein—carries blood rich in nutrients and oxygen to the fetus 0 Umbilical arteries (2)—carry carbon dioxide and debris-laden blood from fetus to placenta

Fetal Circulation 0 Blood flow bypasses the liver through the ductus venosus and enters the inferior vena cava  right atrium of heart 0 Blood flow bypasses the lungs 0 Blood entering right atrium is shunted directly into the left atrium through the foramen ovale 0 Ductus arteriosus connects the aorta and pulmonary trunk (becomes ligamentum arteriosum at birth)

Developmental Aspects of the Cardiovascular System 0 A simple “tube heart” develops in the embryo and pumps by the fourth week 0 The heart becomes a four-chambered organ by the end of seven weeks 0 Few structural changes occur after the seventh week

Aging effects on Cardiovascular System 0 Aging problems associated with the cardiovascular system include 0 Venous valves weaken 0 Varicose veins 0 Progressive atherosclerosis 0 Loss of elasticity of vessels leads to hypertension 0 Coronary artery disease results from vessels filled with fatty, calcified deposits