1. Cardiovascular system - Blood Vessels Anatomy

2. Basic Anatomy of Circulatory routes
Arteries
Arterioles
Capillaries
Venules
Veins
Carry blood towards the heart
Carry blood away from the heart
Connect capillaries to veins
Control blood flow into capillaries & help regulate BP
Allow for “exchange” (filtration/reabsorption) of O2/CO2, nutrients/wastes

3. Structure of Blood Vessels

4. Arteries & Veins
Both are comprised of 3 layers of tissue surrounding “lumen” through which blood will flow: tunica interna, tunica media & tunica externa
Structural difference between arteries & veins primarily due to differences in pressure of blood flowing within

5. 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

6. 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

7. 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

8. Arteries & Veins

9. 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)

10. 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”
may have a central or “thoroughfare” channel that provides direct connection between “metarteriole” (terminal end of arteriole) & venule
Capillaries can be classified as continuous, fenestrated, or sinusoids

11. Circulatory Routes - overview

12. Circulatory Routes – Pulmonary Circuit

13. 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 SVC, IVC & coronary sinus

14. Systemic circuit - Arteries

15. Systemic circuit - Veins

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

17. Hepatic portal circulation
Venous blood flow from GIT & spleen to liver – ensures delivery of nutrients to liver first
AORTA
Hepatic artery
Cystic vein
Lt. gastric vein
Splenic vein
IVC
LIVER
Hepatic Veins
(blood mixes in sinusioids)
Hepatic Portal Vein
Superior mesenteric vein
Inferior mesenteric vein

18. 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

19. Fetal Circulation
Placenta – 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

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

21. 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”)

22. Upper extremity arteries & veins

25. Coronary circulation