The Cardiovascular System

Structure of the heart

• Pericardium – encloses heart.• Visceral pericardium – inner

layer; parietal – outer layer.• Wall of heart – 3 layers:• 1Epicardium – protects heart

(reduces friction) – visceral pericardium.

http://www.texasheartinstitute.org/HIC/Topics/images/myocard.jpg

• 2Myocardium – cardiac muscle; thick middle layer.

• 3Endocardium – contains blood vessels – inner lining of blood vessels.

http://sprojects.mmi.mcgill.ca/embryology/cvs/graphics/tube_trans.gif

• Heart divided into 4 chambers.• 2 atria – upper chambers, thin-

walled; receive blood returning to heart.

• 2 ventricles – lower chambers, thicker walled; pump blood into arteries.

http://web.buddyproject.org/web019/web019/images/Heart2.jpg

• Septum divides atrium and ventricle on right from left side.

• R atrium receives blood from body from inferior vena cava and superior vena cava.

• R atrium separated from R ventricle by tricuspid valve.

http://www.integrativebiology.ac.uk/images/heart.jpg

• Developing fetus - hole between L and R atria.

• After birth - hole supposed to close.

• If hole does not close - hole in heart (atrial septal defect)

• Blood enters lungs - breathing problems.

http://texasheart.org/HIC/Topics/images/asd.jpg

• Chordae tendineae – attach cusps of tricuspid valve.

• Originate from papillary muscles on walls of ventricles.

• R ventricle pumps blood through pulmonary artery to lungs.

• Pulmonary valve leads into artery.

http://www.delftoutlook.tudelft.nl/info/images/100703033722010.jpg

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• L atrium receives blood from lungs through pulmonary vein.

• L atrium and L ventricle separated by bicuspid (mitral) valve.

• L ventricle pumps through aorta to entire body.

• Aortic valve leads into aorta.

http://www.med.yale.edu/intmed/cardio/echo_atlas/entities/graphics/bicuspid_aortic_valve.gif

http://www.lifeisnow.com/Images/Sections/MyHeart/03_ViewOfTheHeartValves.jpg

• Mitral valve prolapse – one or both cusps stretch and bulge into L atrium during contraction.

• Results in blood going back into L atrium.

Blood flow

• Blood low in O2, high in CO2 enters R atrium.

• R atrium passes blood into R Ventricle.

• R ventricle contracts, blood flows into pulmonary artery (to lungs)

• Pulmonary vein brings blood high in O2 back to L atrium.

http://www.shoppingtrolley.net/images/anatomy/heart.gif

• Blood passes to L ventricle.• Pumped through aorta to body.• 1st 2 branches of aorta – R,L

coronary arteries – supply blood to heart tissue.

• Cardiac veins – drain blood, join together to form coronary sinus – dump into R atrium.

http://www.nlm.nih.gov/medlineplus/ency/imagepages/18128.htm

Cardiac cycle

• Heart sounds made from opening and closing of valves.

• 1st sound made from recoil of blood against closed AV valves (“lub”)

• 2nd sound made from recoil of blood against semilunar valves. (“dup”)

• Heart murmurs result of incomplete valve closure resulting in swishing noise.

http://www.nlm.nih.gov/medlineplus/ency/imagepages/19613.htm

• Sinoatrial node (SA node) – generates action potentials on its own (pacemaker).

• Impulse passes along fibers to mass of specialized tissue (atrioventricular node)

http://dtc.pima.edu/~biology/202alpha/lesson2/conductionsystem.jpg

• From AV node, moves through bundle of His (AV bundle)

• Divide into L and R branches underneath endocardium.

• Give rise to Purkinje fibers.• Causes ventricular walls to

contract.

http://www.nlm.nih.gov/medlineplus/ency/imagepages/18052.htm

ECG

• Electrocardiogram – recording of electrical changes in heart muscle.

• QRS complex – depolarization of ventricular fibers (ventricles contract)

• T wave – ventricular fibers repolarize.

http://www.nlm.nih.gov/medlineplus/ency/imagepages/1135.htm

• Heart rate – duration of cardiac cycle.

• Stroke volume – volume of blood ejected from ventricles during contraction.

• Cardiac output = heart rate X stroke volume.

http://www.pathguy.com/pathphys/pathphy4.gif

• More cells stretched by incoming blood, more strongly heart walls contract to eject blood – Starling’s law of the heart.

• Cardiac output increases with increasing exercise and blood flow.

http://www.besthealth.com/besthealth/bodyguide/reftext/images/100085.jpg

• Heart rate monitored in medulla oblongata of brain.

• Increase in blood pressure – stretch sensors send message to brain to slow heart rate down.

http://www.gnosticteachings.org/images/stories/energies/medulla_oblongata.jpg

Blood vessels

• Arteries – carry oxygenated blood away from heart.

• Branch into arterioles, then capillaries.

• Artery – 3-layered wall surrounding interior (lumen).

http://www.web-books.com/eLibrary/Medicine/Cardiovascular/Images/Athero.gif

• 1Tunica intima – innermost layer.• 2Tunica media – thick smooth

muscle layer (middle)• 3Tunica adventitia – outer layer;

anchors artery to neighboring structures.

http://www.nlm.nih.gov/medlineplus/ency/imagepages/19194.htm

• Vasoconstriction – vessel decreases in diameter.

• Vasodilation – vessel increases in diameter.

• Pulmonary artery – carries deoxygenated blood away from heart (toward lungs)

http://www.nlm.nih.gov/medlineplus/ency/imagepages/8983.htm

• Capillaries – smallest vessels.• Permit exchange of nutrients,

removal of wastes at tissue level.• Thin, permeable walls to allow

diffusion to occur.

http://www-rocq.inria.fr/who/Marc.Thiriet/Glosr/Bio/AppCircul/ImagCircul/MicroCirc.gif

• Veins – carry deoxygenated blood back to heart.

• Capillaries join venules, join to form veins.

• Same 3 layers; tunica media not very thick.

http://www.merck.com/media/mmhe2/figures/fg036_3.gif

• Blood pressure in veins not high, so veins need valves to prevent backflow.

• Blood must flow against gravity back to heart.

http://www.vascularweb.org/graphics/northpoint_graphics_jpg/Varicose_02_Base_300.jpg

Blood Pressure

• Blood pressure – force exerted by blood against walls of vessels.

• Systolic pressure – stretch of arteries to allow for blood flow pumped from heart.

• Diastolic pressure – relaxation.

http://www.ghi.com/WebMD/topics/bloodpressure.jpg

• Pulse – expanding, recoiling of arterial walls.

• Represents # of heartbeats per minute.

http://www.nlm.nih.gov/medlineplus/ency/imagepages/9801.htm

Factors affecting blood pressure

• 1Cardiac output – increase in cardiac output increases blood pressure.

• 2Peripheral resistance – friction + drag in vessels; increases blood pressure. Vasoconstriction increases b.p.

http://www-rohan.sdsu.edu/course/ens304/public_html/section1/Image34.gif

• 3Blood volume – decrease causes drop in b.p.

• Sympathetic nervous system – causes rise in b.p, heart rate.

• Parasympathetic – decrease.

http://www.biocomtech.com/upload/images/hrs_ce_002pic03.jpg

• Hormones regulate b.p.• Epinephrine, norephinephrine –

rise, fall of b.p.• Antidiuretic hormone – rise in b.p.• Kidneys aid in regulation – drop in

b.p. releases renin; renin causes formation of angiotensin.

• Angiotensin – vasoconstriction.• Stimulates release of

aldosterone – increases b.p.

http://www.colorado.edu/kines/Class/IPHY3430-200/image/angiotensin.jpg

Circulatory Pathways

• 1Pulmonary circulation – pulmonary trunk carries blood from R ventricle.

• Divides into R and L pulmonary artery, into capillaries.

• O2 picked up in lungs, brought back to heart via pulmonary veins.

http://webschoolsolutions.com/patts/systems/pul-circ.gif

Arteries

• 2Systemic – blood leaves L ventricle into ascending aorta.

• Branches into R, L coronary arteries (supply heart wall).

• Aorta curves to back (aortic arch)• 3 branches – brachiocephalic, L

common carotid, L subclavian.

http://butler.cc.tut.fi/~malmivuo/bem/bembook/06/fi/0602.gif

• Aorta turns downward (descending aorta).

• Section above diaphragm – thoracic aorta; branch into intercostal arteries (supply thoracic wall).

• Below diaphragm – abdominal aorta.

http://healthlink.uhseast.com/library/healthguide/en-us/images/media/medical/hw/nr551517.jpg

• Branches into celiac artery (liver, spleen, stomach, pancreas), superior mesenteric artery (small intestine), suprarenal arteries (adrenal glands), renal arteries (kidneys), inferior mesenteric artery (large intestine).

• Divides into R, L iliac (to lower legs)

http://www.merck.com/media/mmhe2/figures/fg034_1.gif

• Pelvis, lower limbs – common iliac divides into internal, external iliac.

• External iliac – becomes femoral.• Forms deep femoral artery (flexor

muscles of thigh), popliteal artery (knee), anterior, posterior tibial arteries.

• Head, neck – from common carotid, subclavian.

• R common carotid arises from brachiocephalic.

• R, L common carotid branch into external, internal carotid.

http://www.nlm.nih.gov/medlineplus/ency/imagepages/9552.htm

• Shoulder, upper limbs – from subclavian.

• Axillary artery – near armpit.• Continues down arm as brachial

artery; divides into ulnar, radial arteries.

http://www.eorthopod.com/images/ContentImages/elbow/elbow_anatomy/elbow_anatomy09a.jpg

Veins

• Head, face veins – blood drained into R, L external jugular.

• Merge with subclavian veins internal jugular brachiocephalic vein superior vena cava.

http://www.anaesthesiauk.com/images/frca_img_ijv.gif

• Upper limbs – ulnar, radial vein brachial vein axillary vein.

• Major superficial arm veins – basilic (forearm to middle of upper arm), cephalic (wrist to shoulder), median cubital vein (where blood is drawn).

http://www.dartmouth.edu/~anatomy/assets/self-tests/elbow/surface/surf-ant-elbow-st.jpg

• Inferior vena cava – longest vein in body – great saphenous vein, joins with femoral vein.

• Abdomen – hepatic portal system – blood from capillaries of digestive tract to liver only.

• Dumps blood into superior, inferior mesenteric veins.

http://www.nlm.nih.gov/medlineplus/ency/imagepages/8733.htm

Diseases

• 1Congestive heart failure – can’t pump blood to body.

• Bad circulation to body increased pressure, fluid leaking in lungs.

• Caused by damage to cardiac muscle.

• Symptoms – shortness of breath, swelling in lower legs.

http://www.valley-homecare.com/resource/images/chf_hearts.gif

• 2Hypertension – increase in blood pressure.

• Due to narrowing of blood vessels (atherosclerosis) or hardening of vessels (arteriosclerosis)

http://www.nlm.nih.gov/medlineplus/ency/imagepages/18077.htm

• 3Endocarditis – infection of lining of heart due to bacterial infection.

• Can cause embolus (blood clot)• 4Aneurysm – sac formation in

vessel or heart chamber; can produce tear in vessel (hemorrhage)

http://www.nlm.nih.gov/medlineplus/ency/imagepages/17031.htm