19 The Cardiovascular System: Blood Vessels: Part A.

19 The Cardiovascular System: Blood Vessels: Part A

Structure of Blood Vessel Walls
Lumen Central blood-containing space Three wall layers in arteries and veins Tunica intima, tunica media, and tunica externa Capillaries Endothelium with sparse basal lamina © 2013 Pearson Education, Inc.

• Internal elastic membrane • External elastic membrane
Figure 19.1b Generalized structure of arteries, veins, and capillaries. Tunica intima • Endothelium • Subendothelial layer • Internal elastic membrane Tunica media (smooth muscle and elastic fibers) Valve • External elastic membrane Tunica externa (collagen fibers) • Vasa vasorum Lumen Lumen Artery Capillary network Vein Basement membrane Endothelial cells Capillary © 2013 Pearson Education, Inc.

Tunics Tunica intima Endothelium lines lumen of all vessels
Continuous with endocardium Slick surface reduces friction Subendothelial layer in vessels larger than 1 mm; connective tissue basement membrane © 2013 Pearson Education, Inc.

Tunics Tunica media Smooth muscle and sheets of elastin
Sympathetic vasomotor nerve fibers control vasoconstriction and vasodilation of vessels Influence blood flow and blood pressure © 2013 Pearson Education, Inc.

Tunica externa (tunica adventitia)
Tunics Tunica externa (tunica adventitia) Collagen fibers protect and reinforce; anchor to surrounding structures Contains nerve fibers, lymphatic vessels Vasa vasorum of larger vessels nourishes external layer © 2013 Pearson Education, Inc.

Sinusoid Metarteriole
Figure The relationship of blood vessels to each other and to lymphatic vessels. Venous system Arterial system Large veins (capacitance vessels) Heart Elastic arteries (conducting arteries) Large lymphatic vessels Lymph node Muscular arteries (distributing arteries) Lymphatic system Small veins (capacitance vessels) Arteriovenous anastomosis Lymphatic capillaries Sinusoid Arterioles (resistance vessels) Terminal arteriole Postcapillary venule Metarteriole Thoroughfare channel Capillaries (exchange vessels) Precapillary sphincter © 2013 Pearson Education, Inc.

Arterial System: Elastic Arteries
Large thick-walled arteries with elastin in all three tunics Aorta and its major branches Large lumen offers low resistance Inactive in vasoconstriction Act as pressure reservoirs—expand and recoil as blood ejected from heart Smooth pressure downstream © 2013 Pearson Education, Inc.

Arterial System: Muscular Arteries
Distal to elastic arteries Deliver blood to body organs Thick tunica media with more smooth muscle Active in vasoconstriction © 2013 Pearson Education, Inc.

Arterial System: Arterioles
Smallest arteries Lead to capillary beds Control flow into capillary beds via vasodilation and vasoconstriction © 2013 Pearson Education, Inc.

Table 19.1 Summary of Blood Vessel Anatomy (1 of 2)
© 2013 Pearson Education, Inc.

Microscopic blood vessels Walls of thin tunica intima
Capillaries Microscopic blood vessels Walls of thin tunica intima In smallest one cell forms entire circumference Pericytes help stabilize their walls and control permeability Diameter allows only single RBC to pass at a time © 2013 Pearson Education, Inc.

In all tissues except for cartilage, epithelia, cornea and lens of eye
Capillaries In all tissues except for cartilage, epithelia, cornea and lens of eye Provide direct access to almost every cell Functions Exchange of gases, nutrients, wastes, hormones, etc., between blood and interstitial fluid © 2013 Pearson Education, Inc.

Three structural types
Capillaries Three structural types Continuous capillaries Fenestrated capillaries Sinusoid capillaries (sinusoids) © 2013 Pearson Education, Inc.

Continuous Capillaries
Abundant in skin and muscles Tight junctions connect endothelial cells Intercellular clefts allow passage of fluids and small solutes Continuous capillaries of brain unique Tight junctions complete, forming blood brain barrier © 2013 Pearson Education, Inc.

Pericyte Tight junction
Figure 19.3a Capillary structure. Pericyte Red blood cell in lumen Intercellular cleft Endothelial cell Basement membrane Tight junction Pinocytotic vesicles Endothelial nucleus Continuous capillary. Least permeable, and most common (e.g., skin, muscle). © 2013 Pearson Education, Inc.

Fenestrated Capillaries
Some endothelial cells contain pores (fenestrations) More permeable than continuous capillaries Function in absorption or filtrate formation (small intestines, endocrine glands, and kidneys) © 2013 Pearson Education, Inc.

Basement membrane Tight junction
Figure 19.3b Capillary structure. Pinocytotic vesicles Red blood cell in lumen Fenestrations (pores) Endothelial nucleus Intercellular cleft Basement membrane Tight junction Endothelial cell Fenestrated capillary. Large fenestrations (pores) increase permeability. Occurs in areas of active absorption or filtration (e.g., kidney, small intestine). © 2013 Pearson Education, Inc.

Blood flow sluggish – allows modification
Sinusoid Capillaries Fewer tight junctions; usually fenestrated; larger intercellular clefts; large lumens Blood flow sluggish – allows modification Large molecules and blood cells pass between blood and surrounding tissues Found only in the liver, bone marrow, spleen, adrenal medulla Macrophages in lining to destroy bacteria © 2013 Pearson Education, Inc.

Sinusoid capillary. Most permeable. Occurs in special
Figure 19.3c Capillary structure. Endothelial cell Red blood cell in lumen Large intercellular cleft Tight junction Incomplete basement membrane Nucleus of endothelial cell Sinusoid capillary. Most permeable. Occurs in special locations (e.g., liver, bone marrow, spleen). © 2013 Pearson Education, Inc.

Capillary Beds Microcirculation
Interwoven networks of capillaries between arterioles and venules Terminal arteriole  metarteriole Metarteriole continuous with thoroughfare channel (intermediate between capillary and venule) Thoroughfare channel  postcapillary venule that drains bed © 2013 Pearson Education, Inc.

Capillary Beds: Two Types of Vessels
Vascular shunt (metarteriole—thoroughfare channel) Directly connects terminal arteriole and postcapillary venule True capillaries 10 to 100 exchange vessels per capillary bed Branch off metarteriole or terminal arteriole © 2013 Pearson Education, Inc.

Blood Flow Through Capillary Beds
True capillaries normally branch from metarteriole and return to thoroughfare channel Precapillary sphincters regulate blood flow into true capillaries Blood may go into true capillaries or to shunt Regulated by local chemical conditions and vasomotor nerves © 2013 Pearson Education, Inc.

Precapillary sphincters
Figure Anatomy of a capillary bed. Vascular shunt Precapillary sphincters Metarteriole Thoroughfare channel True capillaries Terminal arteriole Postcapillary venule Sphincters open—blood flows through true capillaries. Terminal arteriole Postcapillary venule Sphincters closed—blood flows through metarteriole – thoroughfare channel and bypasses true capillaries. © 2013 Pearson Education, Inc.

Venous System: Venules
Formed when capillary beds unite Smallest postcapillary venules Very porous; allow fluids and WBCs into tissues Consist of endothelium and a few pericytes Larger venules have one or two layers of smooth muscle cells © 2013 Pearson Education, Inc.

Pulmonary blood vessels 12% Systemic arteries and arterioles 15%
Figure Relative proportion of blood volume throughout the cardiovascular system. Pulmonary blood vessels 12% Systemic arteries and arterioles 15% Heart 8% Capillaries 5% Systemic veins and venules 60% © 2013 Pearson Education, Inc.

Adaptations ensure return of blood to heart despite low pressure
Veins Adaptations ensure return of blood to heart despite low pressure Large-diameter lumens offer little resistance Venous valves prevent backflow of blood Most abundant in veins of limbs Venous sinuses: flattened veins with extremely thin walls (e.g., coronary sinus of the heart and dural sinuses of the brain) © 2013 Pearson Education, Inc.

Table 19.1 Summary of Blood Vessel Anatomy (2 of 2)
© 2013 Pearson Education, Inc.

Figure 19.1a Generalized structure of arteries, veins, and capillaries.
Artery Vein © 2013 Pearson Education, Inc.

Interconnections of blood vessels
Vascular Anastomoses Interconnections of blood vessels Arterial anastomoses provide alternate pathways (collateral channels) to given body region Common at joints, in abdominal organs, brain, and heart; none in retina, kidneys, spleen Vascular shunts of capillaries are examples of arteriovenous anastomoses Venous anastomoses are common © 2013 Pearson Education, Inc.

Physiology of Circulation: Definition of Terms
Blood flow Volume of blood flowing through vessel, organ, or entire circulation in given period Measured as ml/min Equivalent to cardiac output (CO) for entire vascular system Relatively constant when at rest Varies widely through individual organs, based on needs © 2013 Pearson Education, Inc.

Blood pressure (BP) Force per unit area exerted on wall of blood vessel by blood Expressed in mm Hg Measured as systemic arterial BP in large arteries near heart Pressure gradient provides driving force that keeps blood moving from higher to lower pressure areas © 2013 Pearson Education, Inc.

Resistance (peripheral resistance) Opposition to flow Measure of amount of friction blood encounters with vessel walls, generally in peripheral (systemic) circulation Three important sources of resistance Blood viscosity Total blood vessel length Blood vessel diameter © 2013 Pearson Education, Inc.

Factors that remain relatively constant:
Resistance Factors that remain relatively constant: Blood viscosity The "stickiness" of blood due to formed elements and plasma proteins Increased viscosity = increased resistance Blood vessel length Longer vessel = greater resistance encountered © 2013 Pearson Education, Inc.

Frequent changes alter peripheral resistance
Blood vessel diameter Greatest influence on resistance Frequent changes alter peripheral resistance Varies inversely with fourth power of vessel radius E.g., if radius is doubled, the resistance is 1/16 as much E.g., Vasoconstriction  increased resistance © 2013 Pearson Education, Inc.

Small-diameter arterioles major determinants of peripheral resistance
Abrupt changes in diameter or fatty plaques from atherosclerosis dramatically increase resistance Disrupt laminar flow and cause turbulent flow Irregular fluid motion  increased resistance © 2013 Pearson Education, Inc.

Relationship Between Blood Flow, Blood Pressure, and Resistance
Blood flow (F) directly proportional to blood pressure gradient ( P) If  P increases, blood flow speeds up Blood flow inversely proportional to peripheral resistance (R) If R increases, blood flow decreases: F =  P/R R more important in influencing local blood flow because easily changed by altering blood vessel diameter © 2013 Pearson Education, Inc.

Systemic Blood Pressure
Pumping action of heart generates blood flow Pressure results when flow is opposed by resistance Systemic pressure Highest in aorta Declines throughout pathway 0 mm Hg in right atrium Steepest drop occurs in arterioles © 2013 Pearson Education, Inc.

120 Systolic pressure 100 Mean pressure 80 Blood pressure (mm Hg) 60
Figure Blood pressure in various blood vessels of the systemic circulation. 120 Systolic pressure 100 Mean pressure 80 Blood pressure (mm Hg) 60 Diastolic pressure 40 20 Aorta Veins Arteries Venules Arterioles Capillaries Venae cavae © 2013 Pearson Education, Inc.

Arterial Blood Pressure
Reflects two factors of arteries close to heart Elasticity (compliance or distensibility) Volume of blood forced into them at any time Blood pressure near heart is pulsatile © 2013 Pearson Education, Inc.

Systolic pressure: pressure exerted in aorta during ventricular contraction Averages 120 mm Hg in normal adult Diastolic pressure: lowest level of aortic pressure Pulse pressure = difference between systolic and diastolic pressure Throbbing of arteries (pulse) © 2013 Pearson Education, Inc.

Mean arterial pressure (MAP): pressure that propels blood to tissues MAP = diastolic pressure + 1/3 pulse pressure Pulse pressure and MAP both decline with increasing distance from heart Ex. BP = 120/80; MAP = 93 mm Hg © 2013 Pearson Education, Inc.

Capillary Blood Pressure
Ranges from 17 to 35 mm Hg Low capillary pressure is desirable High BP would rupture fragile, thin-walled capillaries Most very permeable, so low pressure forces filtrate into interstitial spaces © 2013 Pearson Education, Inc.

Changes little during cardiac cycle
Venous Blood Pressure Changes little during cardiac cycle Small pressure gradient; about 15 mm Hg Low pressure due to cumulative effects of peripheral resistance Energy of blood pressure lost as heat during each circuit © 2013 Pearson Education, Inc.

Factors Aiding Venous Return
Muscular pump: contraction of skeletal muscles "milks" blood toward heart; valves prevent backflow Respiratory pump: pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand Venoconstriction under sympathetic control pushes blood toward heart © 2013 Pearson Education, Inc.

Direction of blood flow
Figure The muscular pump. Venous valve (open) Contracted skeletal muscle Venous valve (closed) Vein Direction of blood flow © 2013 Pearson Education, Inc.

Maintaining Blood Pressure
Requires Cooperation of heart, blood vessels, and kidneys Supervision by brain Main factors influencing blood pressure Cardiac output (CO) Peripheral resistance (PR) Blood volume © 2013 Pearson Education, Inc.

Maintaining Blood Pressure
F =  P/R; CO =  P/R;  P = CO × R Blood pressure = CO × PR (and CO depends on blood volume) Blood pressure varies directly with CO, PR, and blood volume Changes in one variable quickly compensated for by changes in other variables © 2013 Pearson Education, Inc.

CO = SV × HR; normal = 5.0-5.5 L/min
Cardiac Output (CO) CO = SV × HR; normal = L/min Determined by venous return, and neural and hormonal controls Resting heart rate maintained by cardioinhibitory center via parasympathetic vagus nerves Stroke volume controlled by venous return (EDV) © 2013 Pearson Education, Inc.

Figure 19.8 Major factors enhancing cardiac output.
Exercise BP activates cardiac centers in medulla Activity of respiratory pump (ventral body cavity pressure) Activity of muscular pump (skeletal muscles) Sympathetic venoconstriction Sympathetic activity Parasympathetic activity Epinephrine in blood Venous return Contractility of cardiac muscle EDV ESV Stroke volume (SV) Heart rate (HR) Initial stimulus Physiological response Result Cardiac output (CO = SV x HR) © 2013 Pearson Education, Inc.

Control of Blood Pressure
Short-term neural and hormonal controls Counteract fluctuations in blood pressure by altering peripheral resistance and CO Long-term renal regulation Counteracts fluctuations in blood pressure by altering blood volume © 2013 Pearson Education, Inc.

Short-term Mechanisms: Neural Controls
Neural controls of peripheral resistance Maintain MAP by altering blood vessel diameter If low blood volume all vessels constricted except those to heart and brain Alter blood distribution to organs in response to specific demands © 2013 Pearson Education, Inc.

Short-term Mechanisms: Neural Controls
Neural controls operate via reflex arcs that involve Baroreceptors Cardiovascular center of medulla Vasomotor fibers to heart and vascular smooth muscle Sometimes input from chemoreceptors and higher brain centers © 2013 Pearson Education, Inc.

The Cardiovascular Center
Clusters of sympathetic neurons in medulla oversee changes in CO and blood vessel diameter Consists of cardiac centers and vasomotor center Vasomotor center sends steady impulses via sympathetic efferents to blood vessels  moderate constriction called vasomotor tone Receives inputs from baroreceptors, chemoreceptors, and higher brain centers © 2013 Pearson Education, Inc.

Short-term Mechanisms: Baroreceptor Reflexes
Baroreceptors located in Carotid sinuses Aortic arch Walls of large arteries of neck and thorax © 2013 Pearson Education, Inc.

Increased blood pressure stimulates baroreceptors to increase input to vasomotor center Inhibits vasomotor and cardioacceleratory centers, causing arteriolar dilation and venodilation Stimulates cardioinhibitory center  decreased blood pressure © 2013 Pearson Education, Inc.

If MAP low  Reflex vasoconstriction  increased CO  increased blood pressure Ex. Upon standing baroreceptors of carotid sinus reflex protect blood to brain; in systemic circuit as whole aortic reflex maintains blood pressure Baroreceptors ineffective if altered blood pressure sustained © 2013 Pearson Education, Inc.

Figure 19.9 Baroreceptor reflexes that help maintain blood pressure homeostasis.
Slide 1 Impulses from baroreceptors stimulate cardioinhibitory center (and inhibit cardioacceleratory center) and inhibit vasomotor center. 3 Sympathetic impulses to heart cause HR, 4a contractility, and CO. Baroreceptors in carotid sinuses and aortic arch are stimulated. 2 Rate of vasomotor impulses allows vasodilation, causing R. 4b IMBALANCE CO and R return blood pressure to homeostatic range. 5 Stimulus: Blood pressure (arterial blood pressure rises above normal range). 1 Homeostasis: Blood pressure in normal range Stimulus: Blood pressure (arterial blood pressure falls below normal range). 1 IMBALANCE CO and R return blood pressure to homeostatic range. 5 Vasomotor fibers stimulate vasoconstriction, causing R. 4b Baroreceptors in carotid sinuses and aortic arch are inhibited. 2 4a Sympathetic impulses to heart cause HR, contractility, and CO. Impulses from baroreceptors activate cardioacceleratory center (and inhibit cardioinhibitory center) and stimulate vasomotor center. 3 © 2013 Pearson Education, Inc.

Short-term Mechanisms: Chemoreceptor Reflexes
Chemoreceptors in aortic arch and large arteries of neck detect increase in CO2, or drop in pH or O2 Cause increased blood pressure by Signaling cardioacceleratory center  increase CO Signaling vasomotor center  increase vasoconstriction © 2013 Pearson Education, Inc.

Short-term Mechanisms: Influence of Higher Brain Centers
Reflexes in medulla Hypothalamus and cerebral cortex can modify arterial pressure via relays to medulla Hypothalamus increases blood pressure during stress Hypothalamus mediates redistribution of blood flow during exercise and changes in body temperature © 2013 Pearson Education, Inc.

Short-term Mechanisms: Hormonal Controls
Short term regulation via changes in peripheral resistance Long term regulation via changes in blood volume © 2013 Pearson Education, Inc.

Short-term Mechanisms: Hormonal Controls
Cause increased blood pressure Epinephrine and norepinephrine from adrenal gland  increased CO and vasoconstriction Angiotensin II stimulates vasoconstriction High ADH levels cause vasoconstriction Cause lowered blood pressure Atrial natriuretic peptide causes decreased blood volume by antagonizing aldosterone © 2013 Pearson Education, Inc.

Inhibits baroreceptors
Figure Direct and indirect (hormonal) mechanisms for renal control of blood pressure. Direct renal mechanism Indirect renal mechanism (renin-angiotensin-aldosterone) Initial stimulus Physiological response Result Arterial pressure Arterial pressure Inhibits baroreceptors Sympathetic nervous system activity Filtration by kidneys Angiotensinogen Renin release from kidneys Angiotensin I Angiotensin converting enzyme (ACE) Angiotensin II Urine formation ADH release by posterior pituitary Thirst via hypothalamus Vasoconstriction; peripheral resistance Adrenal cortex Secretes Aldosterone Blood volume Sodium reabsorption by kidneys Water reabsorption by kidneys Water intake Blood volume Mean arterial pressure Mean arterial pressure © 2013 Pearson Education, Inc.

Long-term Mechanisms: Renal Regulation
Baroreceptors quickly adapt to chronic high or low BP so are ineffective Long-term mechanisms control BP by altering blood volume via kidneys Kidneys regulate arterial blood pressure Direct renal mechanism Indirect renal (renin-angiotensin-aldosterone) mechanism © 2013 Pearson Education, Inc.

Direct Renal Mechanism
Alters blood volume independently of hormones Increased BP or blood volume causes elimination of more urine, thus reducing BP Decreased BP or blood volume causes kidneys to conserve water, and BP rises © 2013 Pearson Education, Inc.

The renin-angiotensin-aldosterone mechanism
Indirect Mechanism The renin-angiotensin-aldosterone mechanism  Arterial blood pressure  release of renin Renin catalyzes conversion of angiotensinogen from liver to angiotensin I Angiotensin converting enzyme, especially from lungs, converts angiotensin I to angiotensin II © 2013 Pearson Education, Inc.

Functions of Angiotensin II
Increases blood volume Stimulates aldosterone secretion Causes ADH release Triggers hypothalamic thirst center Causes vasoconstriction directly increasing blood pressure © 2013 Pearson Education, Inc.

Inhibits baroreceptors
Figure Direct and indirect (hormonal) mechanisms for renal control of blood pressure. Direct renal mechanism Indirect renal mechanism (renin-angiotensin-aldosterone) Initial stimulus Physiological response Result Arterial pressure Arterial pressure Inhibits baroreceptors Sympathetic nervous system activity Filtration by kidneys Angiotensinogen Renin release from kidneys Angiotensin I Angiotensin converting enzyme (ACE) Angiotensin II Urine formation ADH release by posterior pituitary Thirst via hypothalamus Vasoconstriction; peripheral resistance Adrenal cortex Secretes Aldosterone Blood volume Sodium reabsorption by kidneys Water reabsorption by kidneys Water intake Blood volume Mean arterial pressure Mean arterial pressure © 2013 Pearson Education, Inc.

Activation of vasomotor and cardioacceleratory centers in brain stem
Figure Factors that increase MAP. Activity of muscular pump and respiratory pump Release of ANP Fluid loss from hemorrhage, excessive sweating Crisis stressors: exercise, trauma, body temperature Vasomotor tone; bloodborne chemicals (epinephrine, NE, ADH, angiotensin II) Dehydration, high hematocrit Body size Conservation of Na+ and water by kidneys Blood volume Blood pressure Blood pH O2 CO2 Blood volume Baroreceptors Chemoreceptors Venous return Activation of vasomotor and cardioacceleratory centers in brain stem Diameter of blood vessels Blood viscosity Blood vessel length Stroke volume Heart rate Cardiac output Peripheral resistance Initial stimulus Physiological response Result Mean arterial pressure (MAP) © 2013 Pearson Education, Inc.

Monitoring Circulatory Efficiency
Vital signs: pulse and blood pressure, along with respiratory rate and body temperature Pulse: pressure wave caused by expansion and recoil of arteries Radial pulse (taken at the wrist) routinely used Pressure points where arteries close to body surface Can be compressed to stop blood flow © 2013 Pearson Education, Inc.

Superficial temporal artery
Figure Body sites where the pulse is most easily palpated. Superficial temporal artery Facial artery Common carotid artery Brachial artery Radial artery Femoral artery Popliteal artery Posterior tibial artery Dorsalis pedis artery © 2013 Pearson Education, Inc.

Measuring Blood Pressure
Systemic arterial BP Measured indirectly by auscultatory method using a sphygmomanometer Pressure increased in cuff until it exceeds systolic pressure in brachial artery Pressure released slowly and examiner listens for sounds of Korotkoff with a stethoscope © 2013 Pearson Education, Inc.

Measuring Blood Pressure
Systolic pressure, normally less than 120 mm Hg, is pressure when sounds first occur as blood starts to spurt through artery Diastolic pressure, normally less than 80 mm Hg, is pressure when sounds disappear because artery no longer constricted; blood flowing freely © 2013 Pearson Education, Inc.

Variations in Blood Pressure
Transient elevations occur during changes in posture, physical exertion, emotional upset, fever. Age, sex, weight, race, mood, and posture may cause BP to vary © 2013 Pearson Education, Inc.

Alterations in Blood Pressure
Hypertension: high blood pressure Sustained elevated arterial pressure of 140/90 or higher Prehypertension if values elevated but not yet in hypertension range May be transient adaptations during fever, physical exertion, and emotional upset Often persistent in obese people © 2013 Pearson Education, Inc.

Homeostatic Imbalance: Hypertension
Prolonged hypertension major cause of heart failure, vascular disease, renal failure, and stroke Heart must work harder  myocardium enlarges, weakens, becomes flabby Also accelerates atherosclerosis © 2013 Pearson Education, Inc.

Primary or Essential Hypertension
90% of hypertensive conditions No underlying cause identified Risk factors include heredity, diet, obesity, age, diabetes mellitus, stress, and smoking No cure but can be controlled Restrict salt, fat, cholesterol intake Increase exercise, lose weight, stop smoking Antihypertensive drugs © 2013 Pearson Education, Inc.

Homeostatic Imbalance: Hypertension
Secondary hypertension less common Due to identifiable disorders including obstructed renal arteries, kidney disease, and endocrine disorders such as hyperthyroidism and Cushing's syndrome Treatment focuses on correcting underlying cause © 2013 Pearson Education, Inc.

Alterations in Blood Pressure
Hypotension: low blood pressure Blood pressure below 90/60 mm Hg Usually not a concern Only if leads to inadequate blood flow to tissues Often associated with long life and lack of cardiovascular illness © 2013 Pearson Education, Inc.

Homeostatic Imbalance: Hypotension
Orthostatic hypotension: temporary low BP and dizziness when suddenly rising from sitting or reclining position Chronic hypotension: hint of poor nutrition and warning sign for Addison's disease or hypothyroidism Acute hypotension: important sign of circulatory shock; threat for surgical patients and those in ICU © 2013 Pearson Education, Inc.

Hypovolemic shock: results from large-scale blood loss
Circulatory Shock Hypovolemic shock: results from large-scale blood loss Vascular shock: results from extreme vasodilation and decreased peripheral resistance Cardiogenic shock results when an inefficient heart cannot sustain adequate circulation © 2013 Pearson Education, Inc.

Figure 19.18 Events and signs of hypovolemic shock.
Initial stimulus Physiological response Signs and symptoms Result Acute bleeding (or other events that reduce blood volume) leads to: 1. Inadequate tissue perfusion resulting in O2 and nutrients to cells 2. Anaerobic metabolism by cells, so lactic acid accumulates 3. Movement of interstitial fluid into blood, so tissues dehydrate Chemoreceptors activated (by in blood pH) Baroreceptor firing reduced (by blood volume and pressure) Hypothalamus activated (by blood pressure) Brain Major effect Minor effect Respiratory centers activated Cardioacceleratory and vasomotor centers activated Sympathetic nervous system activated ADH released Neurons depressed by pH Intense vasoconstriction (only heart and brain spared) Heart rate Central nervous system depressed Renal blood flow Kidneys Adrenal cortex Renin released Angiotensin II produced in blood Aldosterone released Kidneys retain salt and water Water retention Rate and depth of breathing Tachycardia; weak, thready pulse Skin becomes cold, clammy, and cyanotic Urine output Thirst Restlessness (early sign) Coma (late sign) CO2 blown off; blood pH rises Blood pressure maintained; if fluid volume continues to decrease, BP ultimately drops. BP is a late sign. © 2013 Pearson Education, Inc.

Figure Intrinsic and extrinsic control of arteriolar smooth muscle in the systemic circulation. Vasodilators Metabolic O2 CO2 H+ K+ • Prostaglandins • Adenosine • Nitric oxide Neuronal Sympathetic tone Hormonal • Atrial natriuretic peptide Extrinsic mechanisms Intrinsic mechanisms (autoregulation) Vasoconstrictors • Neuronal or hormonal controls • Maintain mean arterial pressure (MAP) • Redistribute blood during exercise and thermoregulation • Metabolic or myogenic controls • Distribute blood flow to individual organs and tissues as needed Myogenic Neuronal • Stretch Sympathetic tone Metabolic Hormonal • Endothelins • Angiotensin II • Antidiuretic hormone • Epinephrine • Norepinephrine © 2013 Pearson Education, Inc.

Hydrostatic Pressures
Capillary hydrostatic pressure (HPc) (capillary blood pressure) Tends to force fluids through capillary walls Greater at arterial end (35 mm Hg) of bed than at venule end (17 mm Hg) Interstitial fluid hydrostatic pressure (HPif) Pressure that would push fluid into vessel Usually assumed to be zero because of lymphatic vessels © 2013 Pearson Education, Inc.

Colloid Osmotic Pressures
Capillary colloid osmotic pressure (oncotic pressure) (OPc) Created by nondiffusible plasma proteins, which draw water toward themselves ~26 mm Hg Interstitial fluid osmotic pressure (OPif) Low (~1 mm Hg) due to low protein content © 2013 Pearson Education, Inc.

NFP—comprises all forces acting on capillary bed
Hydrostatic-osmotic Pressure Interactions: Net Filtration Pressure (NFP) NFP—comprises all forces acting on capillary bed NFP = (HPc + OPif) – (HPif + OPc) Net fluid flow out at arterial end Net fluid flow in at venous end More leaves than is returned Excess fluid returned to blood via lymphatic system © 2013 Pearson Education, Inc.

Capillary Exchange of Respiratory Gases and Nutrients
Diffusion down concentration gradients O2 and nutrients from blood to tissues CO2 and metabolic wastes from tissues to blood Lipid-soluble molecules diffuse directly through endothelial membranes Water-soluble solutes pass through clefts and fenestrations Larger molecules, such as proteins, are actively transported in pinocytotic vesicles or caveolae © 2013 Pearson Education, Inc.

Arteries of the head and trunk Internal carotid artery
Figure 19.21b Major arteries of the systemic circulation. Arteries of the head and trunk Internal carotid artery External carotid artery Arteries that supply the upper limb Common carotid arteries Subclavian artery Vertebral artery Axillary artery Subclavian artery Brachiocephalic trunk Brachial artery Aortic arch Radial artery Ascending aorta Ulnar artery Coronary artery Celiac trunk Deep palmar arch Abdominal aorta Superficial palmar arch Superior mesenteric artery Digital arteries Arteries that supply the lower limb Renal artery Gonadal artery External iliac artery Inferior mesenteric artery Femoral artery Common iliac artery Popliteal artery Internal iliac artery Anterior tibial artery Posterior tibial artery Arcuate artery Illustration, anterior view © 2013 Pearson Education, Inc.

Arteries of the head and neck, right aspect
Figure 19.22b Arteries of the head, neck, and brain. Ophthalmic artery Branches of the external carotid artery Basilar artery Vertebral artery • Superficial temporal artery Internal carotid artery • Maxillary artery • Occipital artery External carotid artery • Facial artery • Lingual artery Common carotid artery • Superior thyroid artery Thyrocervical trunk Larynx Costocervical trunk Thyroid gland (overlying trachea) Subclavian artery Clavicle (cut) Brachiocephalic trunk Axillary artery Internal thoracic artery Arteries of the head and neck, right aspect © 2013 Pearson Education, Inc.

Major arteries serving the brain (inferior view, right side
Figure 19.22d Arteries of the head, neck, and brain. Anterior Cerebral arterial circle (circle of Willis) Frontal lobe Optic chiasma • Anterior communicating artery Middle cerebral artery • Anterior cerebral artery Internal carotid artery • Posterior communicating artery Mammillary body • Posterior cerebral artery Temporal lobe Basilar artery Vertebral artery Pons Occipital lobe Cerebellum Posterior Major arteries serving the brain (inferior view, right side of cerebellum and part of right temporal lobe removed) © 2013 Pearson Education, Inc.

Liver (cut) Diaphragm Inferior vena cava Esophagus Celiac trunk Common
Figure 19.24b Arteries of the abdomen. Liver (cut) Diaphragm Inferior vena cava Esophagus Celiac trunk Common hepatic artery Left gastric artery Hepatic artery proper Stomach Splenic artery Gastroduodenal artery Left gastroepiploic artery Right gastric artery Spleen Gallbladder Right gastroepiploic artery Pancreas (major portion lies posterior to stomach) Duodenum Superior mesenteric artery Abdominal aorta The celiac trunk and its major branches. The left half of the liver has been removed. © 2013 Pearson Education, Inc.

Major branches of the abdominal aorta.
Figure 19.24c Arteries of the abdomen. Diaphragm Hiatus (opening) for inferior vena cava Inferior phrenic artery Hiatus (opening) for esophagus Adrenal (suprarenal) gland Middle suprarenal artery Celiac trunk Renal artery Kidney Superior mesenteric artery Abdominal aorta Gonadal (testicular or ovarian) artery Lumbar arteries Inferior mesenteric artery Ureter Median sacral artery Common iliac artery Major branches of the abdominal aorta. © 2013 Pearson Education, Inc.

Distribution of the superior and inferior mesenteric arteries.
Figure 19.24d Arteries of the abdomen. Celiac trunk Transverse colon Superior mesenteric artery Aorta Branches of the superior mesenteric artery Inferior mesenteric artery • Middle colic artery Branches of the inferior mesenteric artery • Intestinal arteries • Right colic artery • Ileocolic artery • Left colic artery • Sigmoidal arteries Ascending colon • Superior rectal artery Right common iliac artery Ileum Descending colon Cecum Sigmoid colon Appendix Rectum Distribution of the superior and inferior mesenteric arteries. The transverse colon has been pulled superiorly. © 2013 Pearson Education, Inc.

Superior gluteal artery
Figure 19.25b Arteries of the right pelvis and lower limb. Common iliac artery Internal iliac artery Superior gluteal artery External iliac artery Deep artery of thigh Lateral circumflex femoral artery Medial circumflex femoral artery Obturator artery Femoral artery Adductor hiatus Popliteal artery Anterior tibial artery Posterior tibial artery Fibular artery Dorsalis pedis artery Arcuate artery Dorsal metatarsal arteries Anterior view © 2013 Pearson Education, Inc.

Popliteal artery Anterior tibial artery Fibular artery
Figure 19.25c Arteries of the right pelvis and lower limb. Popliteal artery Anterior tibial artery Fibular artery Posterior tibial artery Lateral plantar artery Dorsalis pedis artery (from top of foot) Medial plantar artery Plantar arch Posterior view © 2013 Pearson Education, Inc.

Veins of the head and trunk Dural venous sinuses Veins that drain
Figure 19.26b Major veins of the systemic circulation. Veins of the head and trunk Dural venous sinuses Veins that drain the upper limb External jugular vein Vertebral vein Subclavian vein Internal jugular vein Axillary vein Right and left brachiocephalic veins Cephalic vein Brachial vein Superior vena cava Basilic vein Great cardiac vein Hepatic veins Splenic vein Median cubital vein Hepatic portal vein Ulnar vein Renal vein Radial vein Superior mesenteric vein Inferior mesenteric vein Digital veins Inferior vena cava Common iliac vein Veins that drain the lower limb Internal iliac vein External iliac vein Femoral vein Great saphenous vein Popliteal vein Posterior tibial vein Anterior tibial vein Small saphenous vein Dorsal venous arch Dorsal metatarsal veins Illustration, anterior view. The vessels of the pulmonary circulation are not shown. © 2013 Pearson Education, Inc.

Veins of the head and neck, right superficial aspect
Figure 19.27b Venous drainage of the head, neck, and brain. Ophthalmic vein Superficial temporal vein Facial vein Occipital vein Posterior auricular vein External jugular vein Vertebral vein Internal jugular vein Superior and middle thyroid veins Brachiocephalic vein Subclavian vein Superior vena cava Veins of the head and neck, right superficial aspect © 2013 Pearson Education, Inc.

Superior sagittal sinus
Figure 19.27c Venous drainage of the head, neck, and brain. Superior sagittal sinus Falx cerebri Inferior sagittal sinus Straight sinus Cavernous sinus Transverse sinuses Sigmoid sinus Jugular foramen Right internal jugular vein Dural venous sinuses of the brain © 2013 Pearson Education, Inc.

Brachiocephalic veins Internal jugular vein Right subclavian vein
Figure 19.28b Veins of the thorax and right upper limb. Brachiocephalic veins Internal jugular vein Right subclavian vein External jugular vein Left subclavian vein Axillary vein Brachial vein Superior vena cava Cephalic vein Azygos vein Accessory hemiazygos vein Basilic vein Hemiazygos vein Posterior intercostals Inferior vena cava Median cubital vein Ascending lumbar vein Median antebrachial vein Basilic vein Cephalic vein Ulnar vein Radial vein Deep venous palmar arch Superficial venous palmar arch Digital veins Anterior view © 2013 Pearson Education, Inc.

Figure 19.29a Veins of the abdomen.
Inferior vena cava Inferior phrenic veins Cystic vein Hepatic veins Hepatic portal system Hepatic portal vein Superior mesenteric vein Splenic vein Suprarenal veins Inferior mesenteric vein Renal veins Gonadal veins Lumbar veins R. ascending lumbar vein L. ascending lumbar vein Common iliac veins External iliac vein Internal iliac veins Schematic flowchart. © 2013 Pearson Education, Inc.

Tributaries of the inferior vena cava.
Figure 19.29b Veins of the abdomen. Inferior phrenic vein Hepatic veins Inferior vena cava Left suprarenal vein Right suprarenal vein Renal veins Left ascending lumbar vein Right gonadal vein Lumbar veins Left gonadal vein Common iliac vein External iliac vein Internal iliac vein Tributaries of the inferior vena cava. Venous drainage of abdominal organs not drained by the hepatic portal vein. © 2013 Pearson Education, Inc.

The hepatic portal circulation.
Figure 19.29c Veins of the abdomen. Hepatic veins Gastric veins Liver Spleen Inferior vena cava Hepatic portal vein Splenic vein Right gastroepiploic vein Inferior mesenteric vein Superior mesenteric vein Small intestine Large intestine Rectum The hepatic portal circulation. © 2013 Pearson Education, Inc.

Common iliac vein Internal iliac vein External iliac vein
Figure 19.30b Veins of the right lower limb. Common iliac vein Internal iliac vein External iliac vein Inguinal ligament Femoral vein Great saphenous vein (superficial) Popliteal vein Small saphenous vein Fibular vein Anterior tibial vein Dorsalis pedis vein Dorsal venous arch Dorsal metatarsal veins Anterior view © 2013 Pearson Education, Inc.

19 The Cardiovascular System: Blood Vessels: Part A.

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19 The Cardiovascular System: Blood Vessels: Part A.

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Presentation on theme: "19 The Cardiovascular System: Blood Vessels: Part A."— Presentation transcript:

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