Human Anatomy and Physiology Unit IV Circulation and Body Defense Part III Blood Vessels

Blood Vessel Topics Components of the blood vessel system Basic structures of blood vessels Blood distribution Capillary exchange Factors affecting blood pressure and flow Control of blood pressure and flow Circulatory routes

Components of the Blood Vessel System The circulatory system is composed of arteries, arterioles, capillaries, venules, and veins

Components of the Circulatory System Heart Arteries Arterioles Capillaries Venules Veins

Blood Vessel Topics Components of the blood vessel system Basic structures of blood vessels Blood distribution Capillary exchange Factors affecting blood pressure and flow Control of blood pressure and flow Circulatory routes

Basic Blood Vessel Structure Specializations of the blood vessel wall gives different types of vessels their unique functions

Basic Blood Vessel Structure Tunica Interna Endothelium Basement membrane Internal elastic lamina Tunica Media Smooth muscle External elastic lamina Tunica Externa Connective tissue

Figure 21.1Comparative structure of blood vessels 21_01abc

Arteries Elastic Well-defined elastic laminae Thick tunica media dominated by elastic fibers Act as pressure reservoirs Muscular Well-defined internal elastic lamina but thin external elastic lamina Thick tunica media dominated by smooth muscle Maintain vascular tone

Figure 21.2 Pressure reservoir function of elastic arteries 21_02

Figure 21.2 Pressure reservoir function of elastic arteries 21_02

Elastic Artery 21_01d

Muscular Artery 21_01d

Arterioles Poorly defined internal elastic lamina Thin layer of smooth muscle forming precapillary sphincter Well-innervated tunica external Control blood flow into capillary beds

Figure 21.3 Arterioles, capillaries, and venule 21_03

Figure 21.3 Arterioles, capillaries, and venule 21_03

Capillaries Microscopic; smallest vessels in body Tunica interna: endothelium and basement membrane Tunica media: None Tunica externa: None Permit exchange of nutrients and wastes between blood and interstitial fluid; distribute blood to postcapillary venules

Figure 21.3 Arterioles, capillaries, and venule 21_03

Figure 21.1Comparative structure of blood vessels

Types of Capillaries Three types Continuous – leaky; muscle, CT, lungs Fenestrated – leakier; kidneys, sm. Intestine, brain, eye, endocrine glands Sinusoids – leakiest; liver, red bone marrow, spleen

Figure 21.4 Anatomy of a continuous capillary 21_04

Figure 21.4 Anatomy of a fenestrated capillary 21_04

Figure 21.4 Anatomy of a sinusoidal capillary 21_04

Figure 21.3 Arterioles, capillaries, and venule 21_03

Venules Microscopic Tunica interna: endothelium and basement membrane Tunica media: 1-2 layers of smooth muscle Tunica externa: Sparse Pass blood into veins; act as blood reservoirs

Figure 21.3 Arterioles, capillaries, and venule 21_03

Veins Range from 0.5mm-30mm Tunica interna: endothelium and basement membrane; no internal elastic lamina; contains valves; large lumen Tunica media: Much thinner than in arteries; no external elastic lamina Tunica externa: Thickest of three layers Return blood to heart

Figure 21.5 Venous veins 21_05

Blood Vessel Topics Components of the blood vessel system Basic structures of blood vessels Blood distribution Capillary exchange Factors affecting blood pressure and flow Control of blood pressure and flow Circulatory routes

Blood Distribution Because systemic veins and venules contain more than half the total blood volume, they are called blood reservoirs

Figure 21.6 Blood distribution in the cardiovascular system 21_06

Blood Vessel Topics Components of the blood vessel system Basic structures of blood vessels Blood distribution Capillary exchange Factors affecting blood pressure and flow Control of blood pressure and flow Circulatory routes

Capillary Exchange Blood hydrostatic pressure pushes fluid out of capillaries (filtration), and blood colloid osmotic pressure pulls fluid into the capillaries (reabsorption)

Figure 21.7 Capillary exchange 21_07

Blood Vessel Topics Components of the blood vessel system Basic structures of blood vessels Blood distribution Capillary exchange Factors affecting blood pressure and flow Control of blood pressure and flow Circulatory routes

Blood Flow BF= CO; (SV X HR) The same factors that change CO change BF Stroke volume: preload and contractility Heart rate: nervous system and chemicals

Figure 21.8 21_08

Figure 21.9 21_09

Figure 21.10 21_10

Figure 21.11 21_11