Cardiovascular System

BLOOD VESSELS Blood Vessels

 Delivery system of dynamic structures  Closed system  Arteries  Carry blood away from the heart  Capillaries  Contact tissue cells and directly serve cellular needs  Veins  Carry blood toward the heart Venous system Arterial system Large veins Heart (capacitance vessels) Elastic arteries Large (conducting lymphatic vessels) vessels Lymph node Muscular arteries (distributing Lymphatic vessels) system Small veins (capacitance Arteriovenous vessels) anastomosis

Lymphatic Sinusoid capillary Arterioles (resistance vessels) Postcapillary Terminal arteriole venule Metarteriole Thoroughfare Capillaries Precapillary sphincter channel (exchange vessels)

Figure 19.2 Common Capillary beds of carotid arteries head and to head and upper limbs subclavian arteries to upper limbs Superior vena cava Aortic arch

Aorta

RA LA

RV LV Azygos Thoracic system aorta

Venous Arterial drainage blood

Inferior vena Capillary beds of cava mediastinal structures and thorax walls

Diaphragm

Abdominal aorta

Capillary beds of Inferior digestive viscera, vena spleen, pancreas, cava kidneys

Capillary beds of gonads, pelvis, and lower limbs

Figure 19.20 Tissue Layers

 Tunica interna  Tunica media  Tunica externa Tunica intima (interna) • Endothelium Valve • Subendothelial layer Internal elastic lamina Tunica media (smooth muscle and elastic fibers) External elastic lamina Tunica externa (collagen fibers)

Lumen Lumen Capillary Vein Artery network Basement membrane Endothelial cells

(b) Capillary

Figure 19.1b Vein

Artery

(a)

Figure 19.1a Arteries of the head and trunk Internal carotid artery Arteries that supply External carotid artery the upper limb Common carotid arteries Subclavian artery Vertebral artery Axillary artery Subclavian artery Brachiocephalic trunk Brachial artery Aortic arch Ascending aorta Radial artery Coronary artery Ulnar artery Thoracic aorta (above diaphragm) Deep palmar arch Celiac trunk Superficial palmar arch Abdominal aorta Digital arteries Superior mesenteric artery Arteries that supply Renal artery the lower limb Gonadal artery External iliac artery Common iliac artery Femoral artery Inferior mesenteric artery Popliteal artery Internal iliac artery Anterior tibial artery Posterior tibial artery (b) Illustration, anterior view Arcuate artery

Figure 19.21b Arteries

 Transport blood from left ventricle to body tissues  High pressure  Three groups  Elastic (conducting)  Muscular (distributing)  Arterioles (resistance) Table 19.1 (1 of 2) Elastic Arteries

 Conducting arteries  Large and thick-walled  Near the heart  Aorta and major branches  Large lumen = low resistance  Expand during systole and recoil during diastole Muscular Arteries

 Distributing arteries  Distal to elastic arteries  Deliver blood to body organs  Thick tunica media with more smooth muscle  Active in vasoconstriction  Examples  Radial, femoral, brachial Resistance Arteries

 Smallest arterial vessels  Lead to capillary beds  Control valves to capillary beds  Site of most vasodilation and vasoconstriction Table 19.1 (1 of 2) Metarterioles are modified capillaries Vascular shunt Precapillary sphincters Metarteriole Thoroughfare channel

True capillaries Terminal arteriole Postcapillary venule (a) Sphincters open—blood flows through true capillaries.

Terminal arteriole Postcapillary venule (b) Sphincters closed—blood flows through metarteriole thoroughfare channel and bypasses true capillaries.

Figure 19.4 Capillaries

 Capillary beds  Microcirculation between arterioles and venules  Two types 1. Continuous 1. Open junctions between adjacent endothelial cells 2. Most common 3. In skin and muscles 2. Fenestrated 1. Pores = permeable 2. Intestines, endocrine organs, kidneys 21_01e Vascular shunt Precapillary sphincters Metarteriole Thoroughfare channel

True capillaries Terminal arteriole Postcapillary venule (a) Sphincters open—blood flows through true capillaries.

Terminal arteriole Postcapillary venule (b) Sphincters closed—blood flows through metarteriole thoroughfare channel and bypasses true capillaries.

Figure 19.4 Capillaries

 Precapillary sphincters  Local chemical conditions  Vasomotor nerves Continuous Capillaries

 Abundant in the skin and muscles  Tight junctions connect endothelial cells  Intercellular clefts allow the passage of fluids and small solutes  Continuous capillaries of the brain  Tight junctions are complete, forming the blood-brain barrier  Blood Brain Barrier Figure 19.22c Arteries of the head, neck, and brain.

Copyright © 2010 Pearson Education, Inc. Pericyte Red blood cell in lumen Intercellular cleft Endothelial cell Basement membrane Tight junction Pinocytotic Endothelial vesicles nucleus (a) Continuous capillary. Least permeable, and most common (e.g., skin, muscle).

Figure 19.3a Pinocytotic vesicles

Red blood cell in lumen

Fenestrations (pores)

Endothelial Intercellular nucleus cleft Basement membrane Tight junction Endothelial cell (b) Fenestrated capillary. Large fenestrations (pores) increase permeability. Occurs in special locations (e.g., kidney, small intestine).

Figure 19.3b Endothelial cell Red blood cell in lumen Large intercellular cleft

Tight junction Incomplete Nucleus of basement endothelial membrane cell (c) Sinusoidal capillary. Most permeable. Occurs in special locations (e.g., liver, bone marrow, spleen).

Figure 19.3c Capillaries

 Functions  Exchange area for blood and interstitial fluid compartment  Diffusion

 O2 and nutrients from the blood to tissues

 CO2 and metabolic wastes from tissues to the blood Pinocytotic vesicles Red blood cell in lumen Endothelial cell

Fenestration Endothelial cell nucleus (pore) Basement membrane

Tight junction Intercellular cleft

Figure 19.16 (1 of 2) Veins

 Functions  Collect blood from capillary beds  “drain” organs and tissues of blood  Become larger as they come closer to the heart Veins of the head and trunk Veins that drain Dural venous sinuses the upper limb External jugular vein Subclavian vein Vertebral vein Axillary vein Internal jugular vein Cephalic vein Right and left Brachial vein brachiocephalic veins Basilic vein Superior vena cava Median cubital vein Great cardiac vein Ulnar vein Hepatic veins Radial vein Splenic vein Digital veins Hepatic portal vein Veins that drain Renal vein the lower limb Superior mesenteric External iliac vein vein Inferior vena cava Femoral vein Inferior mesenteric vein Great saphenous vein Common iliac vein Popliteal vein Internal iliac vein Posterior tibial vein Anterior tibial vein (b) Illustration, anterior Small saphenous vein view. The vessels of the Dorsal venous arch pulmonary circulation are not shown. Dorsal metatarsal veins

Figure 19.26b

Venules

 Formed when capillary beds unite  Very porous  Allow fluids and WBC’s into tissues Pulmonary blood vessels 12% Systemic arteries and arterioles 15% Heart 8%

Capillaries 5%

Systemic veins and venules 60%

 Thinner walls, larger lumens than arteries  Blood pressure is lower than in arteries  Thin tunica media and a thick tunica externa  Capacitance vessels (blood reservoirs)  Contain up to 65% of the blood supply Vein

Artery

(a)

Figure 19.1a Venous Blood Pressure

 Low pressure  Due to cumulative effects of peripheral resistance  Effect of gravity?  Valves  Skeletal muscle and action  Thoracic pressure changes Valve (open)

Contracted skeletal muscle

Valve (closed)

Vein

Direction of blood flow

Figure 19.7 Varicose Veins

 Incompetent valves  Pregnancy  Obesity  Long periods of standing  Hemorrhoids Blood Flow

 Blood flow is involved in

 O2 delivery  Removal of wastes  Gas exchange (lungs)  Absorption of nutrients (digestive tract)  Urine formation (kidneys) Blood Flow

 Perfusion  Rate of blood flow per given volume of tissue  Blood flow (F)  Volume of blood flowing through a vessel, an organ, or tissue in a given period  Measured as ml/min  Varies widely through individual organs  Based on needs F= ΔP/R Blood Flow

• F= Δ P/R o F = Blood flow o ΔP = Difference in pressure between two points o R = Resistance Blood Flow

 Relationship between blood flow, blood pressure, and resistance  If ΔP increases, blood flow speeds up  If R increases, blood flow decreases  R is more important in influencing local blood flow  Changed by altering blood vessel diameter Blood Pressure

 Blood pressure (BP)  Force per unit area exerted on the wall of a blood vessel by the blood  Typically expressed as the height of a column of mercury (mm Hg)  P = H x D Blood Pressure

 Factors influencing blood pressure  Cardiac output (CO)  Peripheral resistance (PR)  Blood volume Blood Pressure

 Systolic pressure  Pressure exerted during ventricular contraction  Top number  Diastolic pressure  Lowest level of arterial pressure  Bottom number  Average value = 120/80  Pulse pressure  Difference between systolic and diastolic pressure Systolic pressure

Mean pressure

Diastolic pressure

 Basic concepts  The pumping action of the heart generates blood flow  Pressure results when flow is opposed by resistance  Systemic pressure  Highest in the aorta  Declines throughout the pathway  Is 0 mm Hg in the right atrium  The steepest drop occurs in arterioles Systolic pressure

Mean pressure

Diastolic pressure

Figure 19.6 Arterial Blood Pressure

 Reflects two factors of the arteries close to the heart  Elasticity  Volume of blood forced into them at any time  Blood pressure near the heart is pulsatile Arterial Blood Pressure

 Mean arterial blood pressure (MABP)  Pressure that propels blood to tissues  Represents average blood pressure

MABP = diastolic pressure + 1/3 pulse pressure

 Pulse pressure and MAP both decline with increasing distance from the heart Hypertension

 “Silent Killer”  Resting systolic >140 mm Hg and/or diastolic >90 mm Hg  Causes  Loss of flexibility in vessel walls  Results  Heart failure  Renal failure  Stroke  Increased risk of aneurysm Capillary Blood Pressure

 Not pulsatile  Low capillary pressure is desirable  High BP would rupture fragile, thin-walled capillaries  Most are very permeable, so low pressure forces filtrate into interstitial spaces Systolic pressure

Mean pressure

Diastolic pressure

 The opposition to blood flow exerted by vessel walls  The result of friction  Influenced by 3 factors  Blood viscosity  Blood vessel length  Blood vessel radius Peripheral Resistance

 Blood viscosity  Albumin  Erythrocytes Peripheral Resistance

 Vessel length  The father fluid travels = more cumulative friction Peripheral Resistance

 Vessel radius  Most significant factor  Vasoconstriction and vasodilation  Flow is proportional to fourth power of radius  Alteration of radius profoundly affects blood flow  Examples… Poiseuille’s Law

 Formula representing the factors influencing flow

F = ΔPπr4/ 8 nL

F= flow ΔP = pressure gradient r4 = vessel radius n = viscosity L = vessel length Poiseuille’s Law

 Blood flow is directly proportional to pressure gradient and vessel radius  Blood flow is inversely proportional to vessel length and blood viscosity

F = ΔPπr4/ 8 nL Questions?

 Homework #1: Artery Labeling  Due in lab!