Lecture Notes: Blood Vessels (Chapter 22)

Overview

• Focus on types of blood vessels, their structure (tunics), and functions
• Blood vessels: Arteries, Veins, Capillaries
• Circuits: Systemic (all body regions) and Pulmonary (to/from lungs)

Types of Blood Vessels

Arteries

• Carry blood away from the heart
• Become smaller (arterioles) as they branch toward capillaries
• End arteries provide a single blood supply route to organs (e.g., splenic, renal artery)
• Elastic, Muscular, Arterioles: largest to smallest

Veins

• Carry blood back to the heart
• Become larger as they merge toward the heart
• More anastomoses than arteries provide alternate routes
• Contain valves to prevent backflow
• Larger lumen compared to arteries

Capillaries

• Microscopic vessels for exchange between blood and body fluids
• Types: Continuous, Fenestrated, Sinusoid
• Capillary beds originate from metarterioles, lead to post-capillary venules

Structure of Blood Vessel Walls (Tunics)

Tunica Intima

• Innermost layer
• Endothelium with areolar connective tissue

Tunica Media

• Middle layer
• Smooth muscle; thicker in arteries than veins
• Sympathetic activity causes vasoconstriction, relaxation causes vasodilation

Tunica Externa

• Outer layer of connective tissue
• Anchors vessels to surroundings
• Large vessels have vaso vasorum (own blood supply)

Companion Vessels

• Arteries and veins lying next to each other
• Supply the same body region

Blood Pressure and Flow

• Arteries: High pressure, no valves
• Veins: Low pressure, valves to prevent backflow
• Skeletal Muscle Pump and Respiratory Pump aid venous return

Capillary Beds

• Functional units of cardiovascular system
• Pre-capillary sphincters regulate blood flow
• Open sphincters allow exchange, closed bypass capillaries

Clinical Application: Varicose Veins

• Enlarged, twisted veins, commonly in legs
• Occur due to faulty valves causing blood pooling
• Factors: heredity, pregnancy, obesity, menopause, aging, prolonged standing
• Treatments: lifestyle changes, medical procedures

Summary

• Understanding blood vessels aids comprehension of circulatory function
• Structural features (e.g., tunics, valves) relate to specific functions and issues (e.g., varicose veins)