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THE HEART Ch 19 Human Anatomy Sonya Schuh-Huerta, Ph.D. Leonardo Da Vinci, Human Heart. The Heart: An Amazing Piece of Machinery. Although it’s not where you keep your emotions, it’s an amazing vital organ of your body. - PowerPoint PPT Presentation
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THE HEARTTHE HEARTCh 19Ch 19
Human AnatomyHuman Anatomy
Sonya Schuh-Huerta, Ph.D.Sonya Schuh-Huerta, Ph.D.
Leonardo Da Vinci, Human Heart
The Heart: An Amazing Piece ofMachinery
• Although it’s not where
you keep your emotions,
it’s an amazing vital
organ of your body
The Heart
• A muscular double pump– Pulmonary circuit takes blood to & from
the lungs– Systemic circuit vessels transport blood
to & from body tissues– Atria receive blood from the pulmonary &
systemic circuits– Ventricles the muscular pumping
chambers of the heart
The Pulmonary & Systemic Circuits
Oxygen-rich,CO2-poor blood
Oxygen-poor,CO2-rich blood
Capillary bedsof lungs wheregas exchangeoccurs
Capillary beds of allbody tissues where gas exchange occurs
Pulmonary veinsPulmonaryarteries
PulmonaryCircuit
Systemic Circuit
Aorta and branches
Left atrium
Heart
Left ventricleRight atrium
Right ventricle
Venae cavae
Location & Orientation Within the Thorax
• Heart typically weighs 250–350 grams (~healthy heart)
• Largest organ of the mediastinum– Located between the lungs– Apex lies to the left of the midline – Base is the broad posterior surface
(c)
Superior vena cava
Left lung
AortaParietal pleura (cut)
Pericardium (cut)
Pulmonary trunk
Diaphragm
Apex of heart
Location of the Heart in the Thorax
Heart
Posterior
Right lung
(b)
Mediastinum
Pericardium(cut)
Fat inepicardium
Rib 5
Left lung
Aorta
Mediastinum
Apex ofheart(d)
Right auricleof right atrium
Superiorvena cava
Right ventricle
Diaphragm
(a)
Rib 2
Midsternal line
Structure of the Heart – Coverings
• Pericardium – 2 primary layers– Fibrous pericardium
• Strong layer of dense connective tissue
– Serous pericardium• Formed from 2 layers
– Parietal layer of the serous pericardium– Visceral layer of the serous pericardium (= epicardium)
Layers of the Pericardium & of the Heart Wall
Fibrous pericardium
Parietal layer of serous pericardium
Pericardial cavity
Epicardium (visceral layer of serous pericardium)
Myocardium
Endocardium
Pulmonarytrunk
Heart chamber
Heart wall
Pericardium
Myocardium
Structure of the Heart – Layers of the Heart Wall
• Epicardium – Visceral layer of the serous pericardium
• Myocardium– Consists of cardiac muscle – all the muscle of the heart– Muscle arranged in circular & spiral patterns
• Endocardium– Endothelium resting on a layer of connective tissue– Lines the internal walls of the heart
Circular & Spiral Arrangements of Cardiac Muscle Bundles
Cardiacmusclebundles
Heart Chambers
• Right & left atria– Superior chambers
• Right & left ventricles– Inferior chambers
• Internal divisions– Interventricular septa– Interatrial septa
• External markings – Coronary sulcus– Anterior interventricular sulcus– Posterior interventricular sulcus
Gross Anatomy of the HeartLeft common carotidarteryLeft subclavian artery
Aortic arch
Ligamentum arteriosum
Left pulmonary artery
Left pulmonary veins
Auricle ofleft atrium
Circumflex artery
Left coronary artery(in coronary sulcus)
Left ventricle
Great cardiac vein
Anterior interventricularartery (in anteriorinterventricular sulcus)
Apex
Brachiocephalic trunk
Superior vena cava
Right pulmonary artery
Ascending aortaPulmonary trunk
Right pulmonary veins
Right atrium
Right coronary artery(in coronary sulcus)
Anterior cardiac vein
Right ventricle
Right marginal artery
Small cardiac vein
Inferior vena cava
Inferior View of the Heart
(d) Inferior view; surface shown rests on the diaphragm (base of heart).
Aorta
Left pulmonary artery
Left pulmonary veins
Auricle of left atrium
Left atrium
Great cardiac vein
Posterior vein of left ventricle
Left ventricle
Apex
Superior vena cava
Right pulmonary artery
Right pulmonary veins
Right atrium
Inferior vena cava
Right coronary artery(in coronary sulcus)
Coronary sinus
Posterior interventricularartery (in posteriorinterventricular sulcus)
Middle cardiac vein
Right ventricle
Right Atrium
• Forms right border of heart
• Receives blood from systemic circuit
• Pectinate muscles – Ridges inside anterior of right atrium
• Crista terminalis– Landmark used to locate veins entering right
atrium
• Fossa ovalis– Depression in interatrial septum
• Remnant of foramen ovale (from embryonic developmt)
Right Ventricle• Receives blood from right atrium through
the tricuspid valve• Pumps blood into pulmonary circuit via
– Pulmonary trunk
• Internal walls of right ventricle– Trabeculae carneae – Papillary muscles– Chordae tendineae
• Pulmonary semilunar valve– Located at opening of right ventricle &
pulmonary trunk
Heart Chambers
Aorta
Left pulmonary artery
Left atrium
Left pulmonary veins
Mitral (bicuspid) valve
Aortic valve
Pulmonary (semilunar) valve
Left ventricle
Papillary muscleInterventricular septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
Superior vena cava
Right pulmonary artery
Pulmonary trunk
Right atrium
Right pulmonary veins
Fossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Left Atrium
• Makes up heart’s posterior surface
• Receives oxygen-rich blood from lungs through pulmonary veins
• Opens into the left ventricle through:– Mitral valve (= bicuspid; left atrioventricular
valve)
Left Ventricle
• Forms apex of the heart
• Very thick strong muscle
• Internal walls of left ventricle– Trabeculae carneae – Papillary muscles– Chordae tendineae
• Pumps blood to systemic circuit via– Aortic semilunar valve (= aortic valve)
Heart Valves
• Each valve composed of– Endocardium with connective tissue core
• Atrioventricular (AV) valves– Between atria & ventricles tricuspid & bicuspid
• Aortic & pulmonary valves– At junction of ventricles & great arteries pulmonary
& aortic semilunar
Heart Chambers & Valves
Aorta
Left pulmonary artery
Left atrium
Left pulmonary veins
Mitral (bicuspid) valve
Aortic (semilunar) valve
Pulmonary (semilunar) valve
Left ventricle
Papillary muscleInterventricular septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
Superior vena cava
Right pulmonary artery
Pulmonary trunkRight atrium
Right pulmonary veinsFossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Fibrous Skeleton
• Surrounds all 4 valves– Composed of dense connective tissue
• Functions:– Anchors valve cusps– Prevents overdilation of valve openings– Main point of insertion for cardiac muscle– Blocks direct spread of electrical impulses
Fibrous Skeleton & Valve StructurePulmonary valve
Aortic valve
Area of cutaway
Mitral valve
Tricuspid valve
Myocardium
Tricuspid(right atrioventricular) valve
Mitral (bicuspid,left atrioventricular)valve
Aorticvalve
Pulmonaryvalve
Fibrousskeleton
Anterior
The Beating Heart
Blood returning to the heart fills atria, putting pressure against atrioventricular valves; atrioventricular valves are forced open.
As ventricles fill, atrioventricular valve flaps hang limply into ventricles.
Atria contract, forcing additional blood into ventricles.
(a) AV valves open; atrial pressure greater than ventricular pressure
Direction ofblood flow
Atrium
Ventricle
Cusp ofatrioventricularvalve (open)
Chordaetendineae
Papillarymuscle
1
2
3
The Beating Heart
Ventricles contract, forcing blood against atrioventricular valve cusps.
Atrioventricular valves close.
Papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria.
(b) AV valves closed; atrial pressure less than ventricular pressure
Atrium
Blood inventricle
Cusps ofatrioventricularvalve (closed)
1
2
3
The Beating Heart
As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open.
As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close.
(a) Semilunar valves open
(b) Semilunar valves closed
Aorta
Pulmonarytrunk
Heart Sounds
• “Lub-dub” sound of valves closing– First sound “lub”
• The AV valves closing
– Second sound “dub”• The semilunar valves closing
Heart SoundsPulmonary valve
Aortic valve
Area of cutaway
Mitral valve
Tricuspid valve Myocardium
Tricuspid(right atrioventricular) valve
Mitral(left atrioventricular)valve
Aorticvalve
Pulmonaryvalve
Fibrousskeleton
Anterior
“Lub”
“dub”
Pathway of Blood Through the Heart
• Beginning with oxygen-poor blood in the superior & inferior venae cavae– Go through pulmonary & systemic circuits– Blood passes through all structures
sequentially• Atria contract together • Ventricles contract together
Blood Flow Through the Heart
Rightatrium
Aorta
To body
To heart
To heart
To lungs
MitralvalveLeftventricle
Leftatrium
Leftatrium
Aorta Leftventricle
Four pulmonary
veins
Rightventricle
Superior vena cava (SVC)Inferior vena cava (IVC)
Coronary sinus
Rightatrium
Pulmonarytrunk
Pulmonaryveins
Pulmonaryarteries
Aorticsemilunarvalve
Tricuspidvalve
Tricuspidvalve
Pulmonarytrunk
Rightventricle
Pulmonarysemilunarvalve
Pulmonarysemilunar valve
IVC
SVC
Two pulmonary arteriescarry the blood to thelungs (pulmonary circuit)to be oxygenated.
Oxygen-rich blood returnsto the heart via the fourpulmonary veins.
Oxygen-poor bloodreturns from the bodytissues back to the heart.
Oxygen-rich blood isdelivered to the bodytissues (systemic circuit).
Oxygen-rich blood
Oxygen-poor blood
Mitralvalve
Aorticsemilunar
valve
Coronarysinus
Heartbeat
• 70–80 beats per minute at rest (adult)– Systole contraction of a heart chamber– Diastole expansion (relaxation) of a heart
chamber
• Systole & diastole also refer to– Stage of heartbeat when ventricles contract &
expand
Structure of Heart Wall
• Walls differ in thickness– Atria thin walls– Ventricles very thick walls (especially left)– Systemic circuit
• Longer than pulmonary circuit• Has greater resistance to blood flow
Structure of Heart Wall
• Left ventricle:3 times thicker than right– Exerts more
pumping force– Flattens right
ventricle into a crescent shape
Rightventricle
Leftventricle
Interventricularseptum
Cardiac Muscle Tissue
• Forms a thick layer called myocardium– Striated like skeletal muscle– Contractions pump blood through the heart &
into blood vessels
Cardiac Muscle Tissue
• Cardiac muscle cells– Short– Branching– Have 1 or 2 nuclei– Not fused muscle cells like skeletal muscle fibers
Cardiac Muscle Tissue
• Cells join at intercalated discs– Complex junctions– Form cellular networks
• Cells are separated by delicate endomysium– Binds adjacent cardiac fibers– Contains blood vessels & nerves
Intercalated Discs
• Intercalated discs complex junctions– Adjacent sarcolemmas interlock– Possess 3 types of cell junctions
• Desmosomes• Fasciae adherens long desmosome-like junctions• Gap junctions
Fasciae adherensGap junctions
Microscopic Anatomy of Cardiac MuscleNucleus Intercalated discs Cardiac muscle cell
(a)
Nucleus
Nucleus
I bandA band
Cardiac muscle cell
Sarcolemma
Z disc
Mitochondrion
Mitochondrion
T tubuleSarcoplasmicreticulum
I band
Intercalated disc
(b)
Cardiac Muscle Tissue
• Triggered to contract by Ca2+ entering the sarcoplasm– Signals sarcoplasmic reticulum (SR) to release Ca2+ ions– Ions diffuse to sarcomeres
• What does this trigger?
sliding filament mechanism – remember this?
Cardiac Muscle Tissue
• Not all cardiac cells are innervated– Will contract in rhythmic manner without
innervation– Inherent rhythmicity
• Is the basis of the rhythmic heartbeat – heart can beat on its own!
Conducting System
• Cardiac muscle has intrinsic ability to:– Generate & conduct impulses– Signal cells to contract rhythmically
• Conducting system: – A series of specialized cardiac muscle cells– Sinoatrial (SA) node (= pacemaker) sets the
inherent rate of contraction generates the electrical impulses
Conducting System of the Heart
The Sinoatrial (SA) node (pacemaker)generates impulses.
Internodal pathway
Superior vena cava Right atrium
Left atrium
Purkinje fibers
Inter-ventricularseptum
The impulsespause (0.1 sec) at the Atrioventricular(AV) node.
The atrioventricular(AV) bundle of His connects the atria to the ventricles.
The bundle branches conduct the impulses through the interventricular septum.
The Purkinje fibersstimulate the contractilecells of both ventricles.
1
2
3
4
5
Thoracic spinal cord
The vagus nerve(parasympathetic)decreases heart rate. Cardioinhibitory
centerCardio-acceleratorycenter
Sympathetic cardiacnerves increase heart rateand force of contraction.
Medulla oblongata
Sympathetictrunkganglion
Dorsal motor nucleusof vagus
Sympathetic trunk
AV node
SA node
Parasympathetic fibers
Sympathetic fibers
Interneurons
Innervation of the Heart
• Heart rate is altered by external controls
• Nerves to the heart include– Visceral sensory fibers
– Parasympathetic branches of the vagus nerve
– Sympathetic fibers from cervical &
upper thoracic chain ganglia
Blood Supply to the Heart
• Functional blood supply– Coronary arteries
• Arise from the aorta– Located in the coronary sulcus– Main branches
• Left & right coronary arteries
Blood Supply to the Heart
Rightventricle
Rightcoronaryartery
Rightatrium
Rightmarginalartery
Posteriorinterventricularartery
Anteriorinterventricularartery
Circumflexartery
Leftcoronaryartery
Aorta
Anastomosis(junction ofvessels)
Leftventricle
Superiorvena cava
(a) The major coronary arteries
Left atrium
Pulmonarytrunk
Superiorvena cava
Anteriorcardiacveins
Smallcardiac vein
Middle cardiac vein
Greatcardiacvein
Coronarysinus
(b) The major cardiac veins
Disorders of the Heart
• Coronary artery disease– Atherosclerosis fatty deposits– Angina pectoris chest pain– Myocardial infarction blocked coronary
artery• Heart attack!
– Silent ischemia no pain or warning; lack of blood & O2 to certain area of heart
Disorders of the Heart
• Heart failure– Progressive weakening of the heart– Cannot meet the body’s demands for
oxygenated blood
• Congestive heart failure (CHF)– Heart enlarges– Pumping efficiency declines
• Pulmonary arterial hypertension – Enlargement & potential failure of right ventricle
Disorders of the Conduction System
• Arrhythmias variation from normal heart rhythm (irregular); often valve problems– Ventricular fibrillation
• Rapid, random firing of electrical impulses in the ventricles
• Results from crippled conduction system• Common cause of cardiac arrest• Ventricles cannot beat together in synchrony
Disorders of the Conduction System
• Arrhythmias– Atrial fibrillation
• Impulses circle within atrial myocardium, stimulating AV node
• Can promote formation of clots– Leads to strokes
• Occur in episodes characterized by:– Anxiety, fatigue, shortness of breath, palpitations
Disorders of the Heart•Congestive heart failure (CHF)
Development of the Heart• Heart folds into thorax region ~Day 20–21• Heart starts pumping on ~Day 22!• Earliest heart chambers are unpaired• Heart in near-final form by Day 35• Blood travels different route than in adult – blood doesn’t
pick up O2 from lungs, but from placenta/mom!
Atrium
Aorta
Superiorvena cava
Inferiorvena cava
Ventricle
Tubularheart Ventricle
Ventricle
4a4
3
2
1
Foramen ovale
Ductus arteriosis
Pulm trunk
Congenital Heart Defects
• Can be traced to month 2 of development– Most common defect is ventricular septal defect
• 2 basic categories of defect– Inadequately oxygenated blood reaches body
tissues– Ventricles labor under increased workload
Congenital Heart Defects
Occurs in~1 in every500 births
Occurs in~1 in every1500 births
Narrowedaorta
Occurs in~1 in every2000 births
(a) Ventricular septal defect.The superior part of the inter-ventricular septum fails to form;thus, blood mixes between thetwo ventricles. More blood isshunted from left to right becausethe left ventricle is stronger.
(b) Coarctation of the aorta.A part of the aorta is narrowed,increasing the workload ofthe left ventricle.
(c) Tetralogy of Fallot. Multiple defects (tetra = four): (1) Pulmonary trunk too narrowand pulmonary valve stenosed, resulting in (2) hypertrophied right ventricle; (3) ventricular septal defect; (4) aorta opens from both ventricles.
The Heart in Old Age
Some age-related changes 1. Hardening & thickening of heart valve cusps
2. Decline in cardiac reserve* (= extra pumping ability)
3. Fibrosis of cardiac muscle excess fibrous connective tissue; less elastic & contractile
*Cardiac reserve = the difference between the rate at which the heart pumps blood at a particular time & its maximum capacity for pumping blood
The Heart in Old Age
• Heart usually functions well throughout life
• But in America, heart disease has become the #1 cause of death!
• Regular aerobic exercise increases the strength & efficiency of the heart
• Decreases bad cholesterol levels (LDL) & lowers blood pressure
So, again exercise is key!
What You Can Do…
• Exercise 150 minutes+/week (of moderate exercise)
• Or exercise 75 minutes+/week (of vigorous exercise)
• Helps clear fatty deposits in coronary arteries & maintains good cardiovascular health throughout life
• Also increases life expectancy!
(Recommendations by AHA)
Some Hot Current Research
• Stem cells to study human heart cells (their development, growth, & function)
• Future promise for regenerative medicine
Cardiomyocytes derived from human stem cells (all in the dish!)
Questions…?
What’s Next?Lab: Sheep Heart Dissection! & Start Blood VesselsWed Lecture: Blood Vessels Wed Lab: Blood Vessels & Respiratory Sys