Cardiovascular system Blood Vessels Anatomy Chap 22 Basic

Cardiovascular system Blood Vessels Anatomy Chap. 22

Basic Anatomy of Circulatory routes Carry blood towards the heart Connect capillaries to veins Arteries Veins Carry blood away from the heart Arterioles Venules Capillaries Allow for “exchange” (filtration/reabsorption) of O 2/CO 2, nutrients/wastes Control blood flow into capillaries & help regulate BP

Structure of Blood Vessels

Arteries & Veins Both are comprised of 3 layers of tissue - tunica interna, tunica media & tunica externa - surrounding “lumen” through which blood will flow: All structural difference between arteries & veins primarily due to differences in pressure of blood flowing within Lumen – larger diameter in veins compared to corresponding artery

Arteries & Veins Tunica Interna – innermost endothelium of simple squamous epithelium + basement membrane § Arteries – have an “internal elastic lamina” of elastic CT to allow for expansion under pressure § Veins – may have “valves” (folds of endothelium + CT) to prevent backflow of blood due to low pressure

Arteries & Veins Tunica Media – middle layer containing smooth muscle (for contractility/vasoconstriction) & elastic CT (for elasticity) § Arteries – have relatively thick tunica media allowing for significant vasoconstriction & elasticity § Elastic/conducting arteries – relatively more elastic tissue than smooth muscle; ie. aorta, pulmonary trunk, etc. § Muscular/distributing arteries - relatively more muscle tissue than elastic tissue; ie. brachial, femoral, etc. § Veins – relatively thin tunica media therefore no significant constriction/elasticity

Arteries & Veins Tunica Externa (a. k. a. adventitia) – made of collagenous CT § Arteries – thin layer § Veins – thickest layer of vein, trying to support against gravity & low pressure

Arteries & Veins

Arterioles & Venules Very small, almost microscopic vessels with only 2 layers of tissue surrounding lumen § Arterioles – endothelium (tunica interna) + very thin layer of smooth muscle cells (tunica media); regulate blood flow to tissues & affect arterial blood pressure § Venules – endothelium (tunica interna) + thin layer of CT (tunica externa)

Capillaries § Microscopic, very thin-walled vessels comprised of endothelium with basement membrane; allows for filtration and reabsorption § Found in all tissues of the body except for those that are “avascular” § Usually form branching networks (“capillary beds”) within tissues for increased surface area § blood flow into capillaries may be regulated by “pre- capillary sphincters” Capillaries can be classified as continuous, fenestrated, or sinusoids

Circulatory Routes overview

Circulatory Routes – Pulmonary Circuit

Circulatory Routes – Systemic circuit § Arterial blood from left ventricle into ascending aorta § Venous return to right atrium through superior vena cava (SVC), inferior vena cava (IVC) & coronary sinus Left common carotid artery Brachiocephalic trunk Ascending aorta (gives off coronary arteries) Left subclavian artery Aortic arch Thoracic (descending) aorta Abdominal aorta Common iliac arteries

Cerebral circulation Basilar artery (from union of vertebral arteries) + Internal carotid arteries Cerebral arterial circle (“circle of Willis)

Cerebral circulation Venous drainage from dural venous sinuses and cerebral veins into internal jugular vein and vertebral veins

Hepatic portal circulation Venous blood flow from GIT & spleen to liver – ensures delivery of nutrients to liver first I V C y tic a p He a r rte A O R T A ein v stic Cy Lt. ga c stri n vei ein ic v n e l Sp LIVER Hepatic Veins (blood mixes in sinusioids) Hepatic Portal Vein r rio eric e p t Su sen me in ve Inf me erior ve sen in ter i c

Hepatic portal circulation § Cystic vein, left gastric vein, splenic vein, inferior & superior mesenteric veins Hepatic portal vein § Hepatic portal vein (deoxygenated/nutrient rich blood) + Hepatic artery (oxygenated blood) sinusoids of liver § Sinusoids of liver Hepatic veins IVC

Lt. Gastric v

Fetal Circulation Placenta – O 2/CO 2 & nutrient/waste between mom & baby Umbilical cord – (2) umbilical arteries (baby mom) & (1) umbilical vein (mom baby) Umbilical vein (O 2/nutrient rich blood) hepatic portal vein & ductus venosus IVC Rt. atrium Rt. Atrium some blood to rt. Ventricle, most shunts across foramen ovale in interatrial septum lt. atrium lt. ventricle

Fetal Circulation Blood from Rt. Ventricle pulmonary trunk across ductus arteriosus to aorta Aorta systemic arteries internal iliac arteries umbilical arteries placenta

Fetal Circulation- Changes at Birth § Umbilical vein ligamentum teres (round ligament) § Umbilical arteries lateral umbilical ligaments § Ductus venosus ligamentum venosum § Foramen ovale fossa ovalis § Ductus arteriosus ligamentum arteriosum § Placenta delivered (“afterbirth”)