Ch. 19 The Cardiovascular System: Blood Vessels

I. OVERVIEW OF BLOOD VESSEL STRUCTURE AND FUNCTION OVERVIEW: Parts & Function Arteries and arterioles: Capillaries Veins and Venules TOPICS Histology Gross Anatomy Physiology Blood Flow Blood Pressure Disorders Specific Blood Vessels & Identification Arteries Capillaries Veins

I. Histology of Blood Vessel Walls– 3 layers 1. Tunica intima • Endothelium Valve • Subendothelial layer Internal elastic lamina 2. Tunica media (smooth muscle and elastic fibers) External elastic lamina 3. Tunica externa (collagen fibers) Vasa Vasorum Lumen Vein Lumen Artery Capillary network Basement membrane Vasodilation & Vasoconstriction Endothelial cells (b) Capillary Figure 19.1b

* a) Endothelium & Basement membrane Function: In veins: 1. Tunica Intima = * a) Endothelium & Basement membrane Function: In veins: * b) Subendothelial Layer– Areolar C.T w/ mostly elastic fibers c) Internal Elastic Lamina (membrane) = Type of vessels: Artery Endothelium SubEndo. Internal E.L. Vein Endothelium SubEndo.

Thickest layer in arteries * a) smooth muscle: 2. Tunica Media = Thickest layer in arteries * a) smooth muscle: * b) Connective tissue: Appears wavy c) External Elastic Lamina = Vessels: only large arteries Location: between T.M. & T.E. 3. Tunica Externa (adventitia) = Thickest layer in veins Outer border unclear Artery Tunica M. Smooth Muscle External E.L Tunica Externa. Vein Tunica M. Smooth Muscle Tunica Ex.

Tunica Intima Endothelium & Internal Elastic Lamina Tunica Media Tunica Externa Tunica Intima Endothelium Tunica Media Tunica Externa

B. Arterial System Elasticity = Compliance 1. Elastic Artery Resistance to Flow: Pressure: 2. Muscular Artery Smooth muscle: Lumen diameter: 3. Arteriole Number & Size: resistance to flow: Flow to capillaries: controlled by

4. Vascular Anastomoses = Arterial anastomoses = Organs: Joints, abdominal organs, brain, and heart Venous anastomoses = very common BRAIN: Arterial Anastomoses = Circle of Willis - Internal Carotid & Vertebral Arteries

C. Capillaries 5-10 µm diameter Basic Structure Endothelium: Some scattered smooth muscle Function: Three Types Continuous capillaries = Prevalence: tight junctions: Brain:

2. Fenestrated capillaries Tight Junctions: Fenestrations Locations: C. Capillaries … 2. Fenestrated capillaries Tight Junctions: Fenestrations Locations: 3. Sinusoidal capillaries (sinusoids) Flattened Leakiest: Pass large molecules and blood cells

4. Capillary Beds a) Metarteriole & Thourghfare Channel = Vascular Shunt Location: Attach Capillary beds attached (10-100 capillaries) b) Precapillary Spincters = Normally closed, but open to allow O2 & nutrients c) Function: Thoroughfare Channel Metarteriole Figure 11.11a

Bypassed Capillary Beds Figure 11.11b

D. Venous System 1. Venules 2. Veins Overall size & Lumen size: Pressure is? Thin walls Capacitance Vessels: blood reservoirs Venous Valves: foldsn in largest V Function: Venous Sinuses: flattened with only endothelium

C. Venous System … - Differences Between Vessels