sign in sign up
<<
Home , Arteriole, Blood vessel, Metarteriole, Precapillary sphincter, Tunica externa, Venule

3/27/2016

Blood Vessels

• Delivery system of dynamic structures Cardiovascular System • Closed system – Vessels • Carry blood away from the – • Contact cells and directly serve cellular needs – • Carry blood toward the heart

Venous system Arterial system Common Large veins Heart beds of carotid ar teries head and to head and (capacitance upper limbs subclavian arteries to upper limbs Elastic arteries Superior vessels) vena cava Aortic Large (conducting arch lymphatic vessels)

vessels node Muscular arteries (distributing Lymphatic vessels) RA LA system

Small veins RV LV (capacitance Arteriovenous Azygos Thoracic system aorta vessels) Venous Arterial drainage blood

Inferior Lymphatic vena Capillary beds of cava mediastinal structures Sinusoid capillary and walls Diaphragm Abdominal (resistance vessels) aorta Postcapillary Terminal Capillary beds of Inferior digestive viscera, vena , , cava kidneys Thoroughfare Capillaries channel (exchange vessels) Capillary beds of gonads, , and lower limbs

Figure 19.2 Figure 19.20

Tunica intima Structure • Valve • Subendothelial layer • Tissue layers ( and – elastic fibers) Tunica media External elastic lamina – – Tunica externa ( fibers) Valve Valve

Tunica intima

Tunica media Lumen Endothelial Lumen Capillary Cell Tunica network externa Endothelial cells

(b) Capillary

Figure 19.1b

1 3/27/2016

Blood Vessel Structure Blood Vessel Structure

Vasa vasorum nourishes outer layers of large vessels

Arteries of the head and trunk Arteries that supply Arteries the upper limb Common carotid arteries Subclavian artery • Transport blood from left ventricle to body Brachiocephalic trunk Aortic arch tissues Coronary artery – High pressure Thoracic aorta (above diaphragm) Deep palmar arch • Three groups Celiac trunk Digital arteries – Elastic (conducting) Superior mesenteric artery Arteries that supply the lower limb – Muscular (distributing) External iliac artery – Arterioles (resistance) Inferior mesenteric artery Anterior tibial artery (b) Illustration, anterior view Arcuate artery

Figure 19.21b

Arteries

• Elastic arteries – Near the heart • Aorta and major branches – Conducting arteries • Conduct blood from the heart to medium-sized arteries – Large and thick-walled – Large lumen = low resistance – Highly elastic • Expand during & recoil during

Table 19.1 (1 of 2)

2 3/27/2016

Arteries Arteries

• Muscular arteries • Resistance arteries – Distributing arteries – Smallest arterial vessels (arterioles) • Distal to elastic arteries • Lead to capillary beds • Deliver blood to body organs • Control valves to capillary beds – Thick tunica media with more smooth muscle – Site of most and – Active in vasoconstriction Metarteriole – Examples • Radial, femoral, brachial

Venule Arteriole

Capillaries Capillaries

• Exchange vessels • Two types • Exceedingly thin walls – just a tunica intima 1. Continuous • Capillary beds • Open junctions between adjacent endothelial cells • Most common – • In & muscles between arterioles 2. Fenestrated and • Pores = permeable • Intestines, endocrine organs, kidneys

Capillaries Capillaries

• Precapillary sphincters – Cuff of smooth muscle fibers – Acts as a valve to control blood flow into the capillary – Responds to local chemical conditions – (sympathetic)

3 3/27/2016

Vascular shunt Precapillary sphincters Metarteriole Thoroughfare channel Capillaries

• Tissue capillary bed may be flooded with blood or nearly completely empty True capillaries Terminal arteriole Postcapillary venule • Examples: GI tract after a meal; skeletal muscle (a) Sphincters open —blood flows through true capillaries. during exercise

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

Figure 19.4

Continuous Capillaries Continuous Capillaries

• Abundant in the skin and muscles • Continuous capillaries of the – Tight junctions connect endothelial cells – Tight junctions are complete, forming the blood- – Intercellular clefts brain barrier allow the passage of – Carrier-mediated transport fluids and small solutes

Pericyte Pinocytotic vesicles in lumen Red blood Intercellular cell in lumen cleft Fenestrations Endothelial (pores) cell

Basement Endothelial Intercellular membrane nucleus cleft Tight junction Pinocytotic Basement membrane Endothelial vesicles Tight junction Endothelial cell nucleus (b) Fenestrated capillary. Large fenestrations (a) Continuous capillary. Least permeable, and (pores) increase permeability. Occurs in special most common (e.g., skin, muscle). locations (e.g., , small intestine).

Figure 19.3a Figure 19.3b

4 3/27/2016

This is not in the Study Guide, just FYI Capillaries Endothelial cell • Functions Red blood cell in lumen – Exchange area for blood and interstitial fluid Large compartment intercellular – cleft • O and nutrients from the blood to tissues Tight junction 2 • CO and metabolic wastes from tissues to the blood Incomplete Nucleus of 2 basement endothelial membrane cell (c) Sinusoidal capillary. Most permeable. Occurs in special locations (e.g., , marrow, spleen).

Figure 19.3c

Veins of the head and trunk Veins that drain Veins the upper limb External Vertebral vein Internal jugular vein Cephalic vein • Functions Right and left Brachial vein brachiocephalic veins Basilic vein Superior vena cava – Collect blood from capillary beds Median cubital vein Great cardiac vein Ulnar vein Hepatic veins – “drain” organs and tissues of blood Radial vein Splenic vein Digital veins Hepatic portal vein • Become larger as they come closer to the heart Veins that drain 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 are not shown. Dorsal metatarsal veins

Figure 19.26b

Venules

• Formed when capillary beds unite • Very porous – Allow fluids and WBC’s into tissues

Copyright © 2010 Pearson Education, Inc.

5 3/27/2016

Pulmonary blood Veins vessels 12% Systemic arteries • Thinner walls, larger lumens than arteries and arterioles 15% Heart 8% • is lower than in arteries • Thin tunica media and a thick tunica externa • Capacitance vessels (blood reservoirs) Capillaries 5% – Contain up to 60% of the blood supply Systemic veins and venules 60%

Figure 19.5

Blood Vessel Matching 1. Pump 2. Resistance vessels, site of most vasodilation and vasoconstriction Pressure 3. Exchange sites 4. Pressure reservoirs, conducting vessels 5. Blood reservoirs • Low pressure 6. Distributing vessels – Due to cumulative effects of peripheral resistance a. Veins • Working against gravity b. Arterioles c. Capillaries – Valves d. Heart e. Elastic arteries – Skeletal muscle action f. Muscular arteries – Thoracic pressure changes

Venous Valves Valve (open)

Contracted skeletal muscle

Valve (closed)

Vein

Direction of blood flow

Figure 19.7

6 3/27/2016

Varicose Veins Blood Flow

• Incompetent valves • Blood flow is involved in

– – O2 delivery – Obesity – Removal of wastes – Long periods of standing – Gas exchange () – – Absorption of nutrients (digestive tract) – Urine formation (kidneys)

Blood Flow Blood Flow

• • F= Δ P – Rate of blood flow per given volume of tissue R • Blood flow (F) o F = Blood flow – Volume of blood flowing through a vessel, an , or tissue in a given period o ΔP = Difference in pressure between two points • Measured as ml/min o R = Resistance • Varies widely through individual organs – Based on needs

Blood Flow Blood Pressure

ó F= Δ P • Blood pressure (BP) R – Force per unit area exerted on the wall blood vessel • Relationship between blood flow, blood by the blood pressure, and resistance – Expressed as the height of a column of mercury – If ∆P increases, blood flow speeds up (mmHg) – If R increases, blood flow decreases – P = H x D • R is more important in influencing local blood • P = pressure • H = height of column flow • D = density of material in the column – Changed by altering blood vessel diameter

7 3/27/2016

Blood Pressure Blood Pressure

• Factors influencing blood pressure • Systolic pressure – (CO) – Pressure exerted during ventricular contraction – Peripheral resistance (PR) – Top number – Blood volume • Diastolic pressure – Lowest level of arterial pressure – Bottom number • Average value = 120/80 • – Difference between systolic and diastolic pressure

Blood Pressure

Systolic pressure • Basic concepts Mean pressure – The pumping action of the heart generates blood flow – Pressure results when flow is opposed by resistance Diastolic pressure • Systemic pressure – Highest in the aorta – Declines throughout the pathway – Is close to 0 mmHg in the right atrium • The steepest drop occurs in arterioles

Figure 19.6

Arterial Blood Pressure Arterial Blood Pressure

• Reflects two factors of the arteries close to the ó Mean arterial blood pressure (MABP) heart ôPressure that propels blood to tissues – Elasticity ôRepresents average blood pressure – Volume of blood forced into them at any time • Blood pressure near the heart is pulsatile MABP = diastolic pressure + 1/3 pulse pressure

Pulse pressure and MABP both decline with increasing distance from the heart

8 3/27/2016

Hypertension Capillary Blood Pressure

• “Silent Killer” • Not pulsatile – Resting systolic >140 mmHg and/or diastolic >90 mmHg • Low capillary pressure is desirable • Causes – High BP would rupture fragile, thin-walled capillaries – Loss of flexibility in vessel walls – Most are very permeable, so low pressure forces • Results filtrate into interstitial spaces – – Renal failure – – Increased risk of

Peripheral Resistance Peripheral Resistance

• The opposition to blood flow exerted by vessel • Viscosity = a fluid’s resistance to flow walls • Blood viscosity influenced by… – The result of friction – Albumin • Influenced by 3 factors – Blood viscosity – Erythrocytes – Blood vessel length – Blood vessel radius

Peripheral Resistance Peripheral Resistance

• Vessel length • Vessel radius – The farther fluid travels = more cumulative friction – Most significant factor – Vasoconstriction and vasodilation – Flow is proportional to fourth power of radius • Alteration of radius profoundly affects blood flow

9 3/27/2016

Poiseuille’s Law Poiseuille’s Law

• Formula representing the factors influencing flow • Blood flow is directly proportional to pressure gradient and vessel radius F = ΔPπr 4 F = ΔPπr 4 8 nL 8 nL F= flow ΔP = pressure gradient r4 = vessel radius n = viscosity L = vessel length

Poiseuille’s Law Regulation of Peripheral Resistance

• Blood flow is inversely proportional to vessel • Local control length and blood viscosity – Arterioles vary diameters = autoregulation F = ΔPπr 4 • A response to the chemical composition of the blood 8 nL – Faster flow = faster removal of wastes

Regulation of Peripheral Resistance Regulation of Peripheral Resistance

ó Local control • Local control Localized hypoxia – Precapillary sphincters Metabolites (CO2, lactic acid, adenosine) • Respond to local stimuli and vasoactive – Endothelial cells & platelets Acidic pH • Vasodilators – NO , Inhibit smooth muscle • Vasoconstrictors

– Endothelians, seratonin, thromboxane A 2 Vasodilation

Increased blood flow

10 3/27/2016

Intrinsic mechanisms Extrinsic mechanisms Peripheral Resistance (autoregulation) • Maintain mean arterial pressure (MAP) • Distribute blood flow to individual • Redistribute blood during exercise and organs and tissues as needed thermoregulation Amounts of: • Example of autoregulation pH Sympathetic Nerves – Blood flow to skeletal muscles O2 ααα Receptors , • During muscle activity, blood flow increases in direct Metabolic β Receptors ββ norepinephrine controls Amounts of: proportion to the metabolic activity

CO 2 • Blood flow can increase 10 × or more during physical activity

+ II K Hormones Adenosine Antidiuretic (ADH) Endothelins Atrial natriuretic Myogenic Stretch peptide (ANP) controls

Dilates Constricts

Figure 19.15

Peripheral Resistance

Brain • Neural control Heart

Skeletal – Directed by ANS via sympathetic innervation muscles • lacks parasympathetic input Skin

Kidney

Abdomen

Other Total blood flow at rest 5800 ml/min

Total blood flow during strenuous exercise 17,500 ml/min

Figure 19.13

Peripheral Resistance Peripheral Resistance

ó Neural control • Baroreflex ôVasomotor center in medulla = primary control center – Baroreceptors (pressure receptors) in ôIntegrates input from 3 ANS reflex circuits • Carotid sinuses ˜Baroreflex • Aortic arch ˜Chemoreflex – Example: Blood pressure increases ˜Ischemic reflex • Inhibitory signals are sent to the vasomotor center • Stimulatory signals are sent to the cardioinhibitory center (which acts through which ?)

11 3/27/2016

3 Impulses from baroreceptors stimulate cardioinhibitory center and inhibit vasomotor 4a Sympathetic Peripheral Resistance center. impulses to heart cause HR, contractility, and CO.

2 Baroreceptors in carotid sinuses and aortic arch are stimulated. • Chemoreflex 4b Rate of vasomotor impulses allows vasodilation, – Excitatory or inhibitory signals to vasomotor causing R 5 CO and R 1 Stimulus: return blood Blood pressure pressure to (arterial blood homeostatic range. center pressure rises above : Blood pressure in normal range normal range). – Chemorecetors detect low blood pH, O 2 levels

5 CO and R and high CO 2 levels return blood pressure 4b Vasomotor to homeostatic range. fibers stimulate vasoconstriction, Chemoreceptors are located in the causing R – • Carotid bifurcation 2 Baroreceptors in carotid sinuses and aortic arch are inhibited. • Aortic arch

4a Sympathetic impulses to heart • Large arteries of the neck cause HR, contractility, and 3 Impulses from baroreceptors stimulate CO. cardioacceleratory center and stimulate vasomotor center.

Peripheral Resistance Peripheral Resistance

• Medullary Ischemic Reflex • Hormonal controls – Triggered by low perfusion of the medulla – Angiotensin II • Generated by kidney release of • Causes vasoconstriction Hypoxia and hypercapnia (high blood CO 2) of the brain – Atrial natriuretic peptide/factor • Causes blood volume and blood pressure to decline Vasoconstriction in extremities • Causes generalized vasodilation

Blood flow directed to head and upper body

Activity of Fluid loss from Crisis stressors: Bloodborne Release Dehydration, Body size muscular of ANP hemorrhage, exercise, trauma, chemicals: high hematocrit Peripheral Resistance pump and excessive body epinephrine, respiratory sweating temperature NE, ADH, pump angiotensin II; ANP release Conservation Blood volume Blood pH, O , of Na + and 2 • Hormonal controls cont. Blood pressure CO water by kidney 2 – Antidiuretic hormone (ADH, ) Blood Baroreceptors Chemoreceptors • Causes intense vasoconstriction in cases of extremely low volume BP Venous Activation of vasomotor and cardiac – Epinephrine return acceleration centers in brain stem • Causes generalized vasoconstriction and increases cardiac output Stroke Heart Diameter of Blood Blood vessel volume rate blood vessels viscosity length

Cardiac output Peripheral resistance

Initial stimulus Physiological response Result Mean systemic arterial blood pressure

Figure 19.11

12 3/27/2016

Fluid Shifts Between Capillaries and Venous system Arterial system Large veins Heart (capacitance Tissue vessels) Elastic arteries Large (conducting lymphatic vessels) • Capillaries allow plasma and solutes to pass into interstitial space Ï vessels interstitial or (ECF) Lymph node Muscular arteries (distributing – Facilitates exchange of resources & wastes between Lymphatic vessels) system cells & plasma Small veins (capacitance Arteriovenous – Dynamic equilibrium vessels) anastomosis – Imbalances? Lymphatic Sinusoid capillary – Exceptions? Arterioles (resistance vessels) Postcapillary Terminal arteriole venule Metarteriole Thoroughfare Capillaries Precapillary sphincter channel (exchange vessels)

Figure 19.2

Regulation of ECF Movement

HP = hydrostatic pressure • Due to fluid pressing against a wall • Hydrostatic and osmotic pressure • “Pushes” • Arteriole Venule In capillary (HP c) • Pushes fluid out of capillary – Hydrostatic “pushes” and osmotic “sucks” Interstitial fluid • 35 mm Hg at arterial end and 17 mm Hg at venous end of – 4 types capillary in this example Capillary • In interstitial fluid (HP if ) Net HP—Net OP Net HP—Net OP • Pushes fluid into capillary (35—0) —(26—1) (17—0) —(26—1) • 0 mm Hg in this example

Capillary hydrostatic pressure Move water out of Net Net OP = osmotic pressure • Due to presence of nondiffusible the vascular system HP OP Net Net 35 25 solutes (e.g., plasma proteins) Interstitial osmotic pressure HP OP • “Sucks” mm mm 17 25 • In capillary (OP c) mm mm • Pulls fluid into capillary • 26 mm Hg in this example • In interstitial fluid (OP if ) Interstitial hydrostatic pressure Move water into • Pulls fluid out of capillary NFP (net filtration pressure) NFP is ~8 mm Hg; • 1 mm Hg in this example Capillary osmotic pressure the vascular system is 10 mm Hg; fluid moves out fluid moves in

Figure 19.17

Regulation of ECF Movement Regulation of ECF Movement

• Hydrostatic • Osmotic – Capillary hydrostatic pressure (HP ) c – Interstitial fluid osmotic pressure (OP if ) • Capillary blood pressure • The osmotic pressure force created by interstitial solutes • Tends to force fluids through the capillary walls • Low (~1 mm Hg), due to low protein content • Is greater at the arterial end (35 mm Hg) of a bed than at the venous end (17 mm Hg) – Capillary colloid osmotic pressure (OP c) • Created by non-diffusible plasma proteins, which draw – Interstitial hydrostatic pressure (HP if ) • Pressure of fluid within intercellular spaces water toward themselves • Constantly enters lymphatic drainage • ~26 mm Hg • Averages 0 mmHg

13 3/27/2016

Regulation of ECF Movement Regulation of ECF Movement

• The movement of fluid between the • Net Filtration Pressure (NFP) extracellular compartments is driven by a – Comprises all the forces acting on a capillary bed pressure gradient – Most influenced by capillary hydrostatic pressure NFP = (HP c - HP if ) - (Op c - OP if )

Regulation of ECF Movement

HP = hydrostatic pressure Arterial NFP • Due to fluid pressing against a wall • • “Pushes” • In capillary (HP ) Arteriole Venule c – Arterial end of a capillary bed = hydrostatic forces • Pushes fluid out of capillary Interstitial fluid • 35 mm Hg at arterial end and dominate 17 mm Hg at venous end of • Fluid moves out capillary in this example Capillary • In interstitial fluid (HP if ) • NFP = (35-0) – (26-1) = 10 mm Hg Net HP—Net OP Net HP—Net OP • Pushes fluid into capillary (35—0) —(26—1) (17—0) —(26—1) • 0 mm Hg in this example • Venous NFP Net Net OP = osmotic pressure • Due to presence of nondiffusible – Venous end of a capillary bed = osmotic forces dominate HP OP Net Net 35 25 solutes (e.g., plasma proteins) HP OP • “Sucks” • Fluid moves in mm mm 17 25 • In capillary (OP c) • NFP = (17-0) – (26-1) = -8 mm Hg mm mm • Pulls fluid into capillary • 26 mm Hg in this example • In interstitial fluid (OP if ) • Excess fluid • Pulls fluid out of capillary NFP (net filtration pressure) NFP is -8 mm Hg; • 1 mm Hg in this example – Returned to the blood via the is 10 mm Hg; fluid moves out fluid moves in Filtration= Reabsorption= fluid moves out fluid moves in

Figure 19.17

Venous system Arterial system Large veins Heart (capacitance vessels) Elastic arteries Large (conducting lymphatic vessels) vessels • Occurs when filtration greatly exceeds Lymph node Muscular arteries reabsorption (distributing Lymphatic vessels) – Abnormal increase in interstitial fluid volume 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

14 3/27/2016

Venous Blood Pressure Venous Return

• Changes little during the • Venous hydrostatic pressure relatively low • Low pressure due to cumulative effects of • Returning blood to heart requires adaptations peripheral resistance • Central venous pressure – Pressure at the point where vena cava enter heart – Average = 4.6 mm Hg

Mechanisms of Venous Return 21_09

1. Thoracic pump • Pressure changes created during breathing move blood toward the heart by squeezing abdominal veins as thoracic veins expand 2. Cardiac Suction • During atrial systole, movement of AV valves enlarges atria = lower pressure = increasing pressure gradient between vena cava 3. Muscular pump • Contraction of skeletal muscles “milk” blood toward the heart and valves prevent backflow 4. Gravity • Helps with return of blood from superior regions

Mechanisms of Venous Return Types and Causes of LVR

• Circulatory shock 1. – Definition = CO is insufficient to meet the metabolic – Most common form of shock demands of the tissues – Result of blood loss – Cardiogenic shock • Direct losses: hemorrhage, trauma, burns, ulcers • Heart’s ability to pump blood is impaired • Indirect losses: fluids other than blood lost Other types of shock – – Burns and dehydration • Due to low venous return (LVR) – Hypovolemic shock – Vascular shock » Neurogenic shock » Septic shock » Anaphylactic shock

15 3/27/2016

Acute bleeding (or other events that cause Initial stimulus blood volume loss) leads to: Physiological response 1. Inadequate tissue perfusion Signs and symptoms resulting in ↓ O2 and nutrients to cells Types and Causes of LVR Shock 2. Anaerobic metabolism by cells, so lactic Result acid accumulates 3. Movement of interstitial fluid into blood, so tissues dehydrate 2. Vascular shock Chemoreceptors activated Baroreceptor firing reduced Hypothalamus activated Brain (by ↓ in blood pH) (by ↓ blood volume and pressure) (by ↓ pH and ↓ blood pressure) – Body retains normal blood volume but blood Major effect Minor effect Activation of Cardioacceleratory and Sympathetic nervous ADH Neurons accumulates in extremities respiratory centers vasomotor centers activated system activated released depressed by ↓ pH

a) Neurogenic shock Intense vasoconstriction ↑Heart rate (only heart and brain spared) • Usually follows trauma Ï widespread vasodilation depressed ↓ Renal blood flow Kidney

b) Septic shock Renin released Adrenal cortex • Bacterial endotoxin simulates vasodilation Angiotensin II produced in blood c) Anaphylactic shock Aldosterone Kidneys retain Water • Following allergic reaction released salt and water retention

↑ Rate and Tachycardia, Skin becomes ↓ Urine output Thirst Restlessness Coma • Sudden release of Ï massive vasodilation and permeability depth of weak, thready cold, clammy, (early sign) (late sign) changes breathing pulse and cyanotic

Blood pressure maintained; CO blown 2 if fluid volume continues to off; blood decrease, BP ultimately pH rises drops. ↓ BP is a late sign.

Figure 19.18

Pathways of Blood Circulation Systemic Circulation

• Complete circuits begin and end at heart • Carries rich blood to all parts of the body • A double pump with 2 pathways • Subdivisions – Pulmonary circulation – • Supplies myocardium – Systemic circulation – Hepatic-portal circulation • Directs blood from spleen, , pancreas, gallbladder, and intestines to the liver via portal vein – Organs of and recycling – materials are substantially metabolized in the liver before reaching general circulation – Jaundice • Portal systems – 2 capillary beds

Inferior vena cava (not part of hepatic Pulmonary Circulation portal system)

Gastric veins Hepatic veins Spleen • Carries oxygen poor blood from heart to Inferior vena cava alveolar surface of lungs and oxygen rich blood Liver Splenic vein back to the heart Right gastroepiploic Hepatic portal vein vein Inferior mesenteric vein Superior mesenteric vein Small intestine Large intestine

Rectum

(c) The hepatic portal circulation.

Copyright © 2010 Pearson Education, Inc.

16 3/27/2016

Fetal Circulation

• Oxygen and nutrients obtained from maternal • Ductus venosus blood – Continuation of the umbilical – Respiratory and digestive systems not yet functional vein under liver – Blood oxygenated in placenta – Drains into inferior vena cava • Attached to uterine wall by cotyledons (contain placental – Allows blood to bypass the liver villi) – Functionally closes minutes • Waste carried from by umbilical arteries after birth – Extensions of the internal iliac arteries – Structurally closes in term • Nutrient rich blood enters fetal circulation by umbilical infants in 3-7 days vein

Fetal Circulation Fetal Circulation

• Foramen ovale • Foramen ovale – Opening between right and left atria Ï bypasses fetal – First breath after birth decreases pulmonary pressure lungs – Left atrial pressure exceeds right and forces foramen – Blood routed to aorta ovale closed – May remain open • Patent foramen ovale or ASD • “Hole in the heart” • May be surgically closed

Fetal Circulation Fetal Circulation

• Ductus arteriosis • Ductus arteriosis – Connects with descending thoracic – Failure to close at birth = patent ductus arteriosis aorta – Leads to pulmonary – Also aids in bypassing lungs and congestive heart failure – NSAIDs are administered to force closure • Why NSAIDs MUST be avoided in late pregnancy

17 3/27/2016

Fetus Aortic arch Superior vena cava Fetal Circulation Ductus arteriosus Ligamentum arteriosum Pulmonary artery Pulmonary veins Heart Foramen ovale Placenta Left atrium Fossa ovalis Liver Ductus venosus Ligamentum venosum Umbilical vein Aorta Hepatic portal vein Umbilical vein Ligamentum teres Ductus venosus Internal Inferior vena cava Foramen ovale Umbilicus Abdominal aorta iliac arteries Common iliac artery Umbilical arteries Inferior vena cava Medial umbilical ligaments Umbilical Urinary bladder Right atrium Ductus arteriosis Umbilical cord arteries

Placenta Right ventricle Placenta

High oxygenation Moderate oxygenation Low oxygenation Pulmonary artery (a) Very low oxygenation

Figure 28.14a

Categories for Blood Pressure Hypertension Levels in Adults (Ages 18 Years and Older) • “Silent Killer” Blood Pressure Level (mmHg) Category Systolic Diastolic – Produces few symptoms Normal < 120 and < 80 • Major cause of heart failure, stroke & kidney Prehypertension 120-139 or 80-89 failure High Blood Pressure • Resting systolic above? Stage 1 140–159 or 90–99 • Resting diastolic above? Hypertension

Stage 2 160 or 100 Hypertension

Hypertension Renal Hypertension

• Arteries are stretched • Blood flow to kidneys is reduced – Tears endothelium = exposes muscle = focal point – Leads to thickening of arterioles Ï respond as for = worsens hypertension though BP were reduced Ï Angiotensin II produced • Remember atherosclerosis? Ï aldosterone released – Emboli may lodge in narrowed vessel • Increases blood volume and BP – Clots may form on roughened endothelium – Worsens existing hypertension Ïkidney failure may result – Long-standing belief that high , high diets contribute are being called into question

18 3/27/2016

Hypertension Hypertension

• Primary hypertension • 90% of hypertensive conditions – – 10% of cases – Cause unknown Due to identifiable disorders – Contributing factors include – • • Kidney disease • Obesity • Atherosclerosis » extensively vascularized • Endocrine disorders » 10 miles per pound!! – Hyperthyroidism » Means increased peripheral • Smoking – Cushing’s disease » Nicotine = coronary vasoconstrictor – Polycythemia • Diet » Salt = water retention Ï higher blood volume » Mineral deficiencies (Mg, K, Ca)

This picture shows a red and swollen thigh and leg caused by a • Deep venous (DVT) blood clot () in the deep veins in the groin • Affects mainly the veins in the lower leg and the thigh which prevents normal return of blood from the leg to the heart. • It involves the formation of a clot (thrombus) in the larger veins of the area

• Can be caused by any condition that restricts venous return in the lower extremities • Cause in 1/3 of cases is unknown

19