Cardiovascular system -Cardiovascular system -Blood VesselsBlood Vessels

Anatomy Chap. 22Anatomy Chap. 22

Basic Anatomy of Circulatory routes

Arteries

Arterioles

Capillaries

Venules

VeinsCarry blood away from the heart

Control blood flow into capillaries & help regulate BP

Allow for “exchange” (filtration/reabsorption) of O2/CO2, nutrients/wastes

Connect capillaries to veins

Carry blood towards the heart

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 & VeinsTunica 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

Ascending aorta (gives off coronary arteries)

Aortic arch

Brachiocephalic trunk

Left common carotid artery

Left subclavian artery

Thoracic (descending) aorta

Abdominal aorta

Common iliac arteries

Arterial blood from left ventricle into ascending aorta

Venous return to right atrium through superior vena cava (SVC), inferior vena cava (IVC) & coronary sinus

Cerebral circulationBasilar 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

LIVER

Hepatic Portal Vein

Cystic vein

Lt. gastric vein

Splenic vein

Inferior mesenteric

veinSuperio

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mesenteric

vein

AORTA

(blood mixes in sinusioids)

Hepatic Veins

IVC

Hepatic arte

ry

Hepatic portal circulationVenous blood flow from GIT & spleen to liver – ensures delivery of nutrients to liver first

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 CirculationPlacenta – O2/CO2 & nutrient/waste between mom & baby

Umbilical cord – (2) umbilical arteries (baby mom) & (1) umbilical vein (mom baby)

Umbilical vein (O2/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

Blood from Rt. Ventricle pulmonary trunk across ductus arteriosus to aorta

Aorta systemic arteries internal iliac arteries umbilical arteries placenta

Fetal Circulation

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”)

Systemic circuit - Arteries

Systemic circuit - Veins

Upper extremity arteries

Ulna veinRadial vein

Upper extremity arteries & veins

Arteries & Veins of lower extremity

Arteries & Veins of lower extremity

Arteries & Veins of lower extremity

Vessels of abdominal region

Lt. Gastric a