Transcript Ch19.Heart_1

THE HEART
Ch 19
Leonardo Da Vinci, Human Heart
Human Anatomy
Sonya Schuh-Huerta, Ph.D.
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
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
Capillary beds
of lungs where
gas exchange
occurs
Pulmonary
arteries
Pulmonary
Circuit
Pulmonary veins
Aorta and branches
Venae cavae
Left atrium
Right atrium
Left ventricle
Heart
Right ventricle
Oxygen-rich,
CO2-poor blood
Oxygen-poor,
CO2-rich blood
Systemic Circuit
Capillary beds of all
body tissues where
gas exchange occurs
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
Location of the Heart in the Thorax
Superior vena cava
Midsternal line
Rib 2
Aorta
Parietal pleura (cut)
Pulmonary trunk
Left lung
Pericardium (cut)
Apex of heart
Diaphragm
Diaphragm
(c)
(a)
Mediastinum
Mediastinum
Heart
Right lung
(b)
Posterior
Superior
vena cava
Aorta
Right
auricle
of right
atrium
Left lung
Right
ventricle
(d)
Fat in
epicardium
Rib 5
Pericardium
(cut)
Apex of
heart
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
Pericardium
Myocardium
Pulmonary
trunk
Fibrous pericardium
Parietal layer of serous
pericardium
Pericardial cavity
Epicardium (visceral
layer of serous
pericardium)
Myocardium
Endocardium
Heart chamber
Heart
wall
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
Cardiac
muscle
bundles
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 Heart
Brachiocephalic trunk
Left common carotid
artery
Left subclavian artery
Superior vena cava
Aortic arch
Ligamentum arteriosum
Right pulmonary artery
Left pulmonary artery
Ascending aorta
Pulmonary trunk
Left pulmonary veins
Right pulmonary
veins
Right atrium
Right coronary artery
(in coronary sulcus)
Anterior cardiac vein
Auricle of
left atrium
Circumflex artery
Left coronary artery
(in coronary sulcus)
Left ventricle
Right ventricle
Right marginal artery
Small cardiac vein
Inferior vena cava
Great cardiac vein
Anterior interventricular
artery (in anterior
interventricular sulcus)
Apex
Inferior View of the Heart
Aorta
Left pulmonary artery
Superior vena cava
Right pulmonary artery
Right pulmonary veins
Left pulmonary veins
Auricle of left atrium
Right atrium
Left atrium
Inferior vena cava
Great cardiac vein
Posterior vein of
left ventricle
Left ventricle
Coronary sinus
Right coronary artery
(in coronary sulcus)
Posterior interventricular
artery (in posterior
interventricular sulcus)
Middle cardiac vein
Right ventricle
Apex
(d) Inferior view; surface shown rests on the diaphragm (base of heart).
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
Superior vena cava
Right pulmonary artery
Pulmonary trunk
Left pulmonary artery
Left atrium
Left pulmonary veins
Right atrium
Right pulmonary
veins
Fossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Mitral (bicuspid) valve
Aortic valve
Pulmonary (semilunar)
valve
Left ventricle
Papillary muscle
Interventricular septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
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
Superior vena cava
Right pulmonary artery
Pulmonary trunk
Right atrium
Left pulmonary artery
Left atrium
Left pulmonary veins
Mitral (bicuspid) valve
Right pulmonary
veins
Fossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Aortic (semilunar) valve
Pulmonary (semilunar)
valve
Left ventricle
Papillary muscle
Interventricular septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
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 Structure
Pulmonary valve
Aortic valve
Area of cutaway
Mitral valve
Tricuspid valve
Tricuspid
(right atrioventricular)
valve
Mitral (bicuspid,
left atrioventricular)
valve
Aortic
valve
Myocardium
Pulmonary
valve
Fibrous
skeleton
Anterior
The Beating Heart
1
Blood returning to
the heart fills atria,
putting pressure
against atrioventricular
valves; atrioventricular
valves are forced
open.
Direction of
blood flow
Atrium
Cusp of
atrioventricular
valve (open)
2
As ventricles fill,
atrioventricular
valve flaps hang
limply into
ventricles.
Chordae
tendineae
Papillary
muscle
Ventricle
3
Atria contract,
forcing additional
blood into ventricles.
(a) AV valves open; atrial pressure greater than ventricular pressure
The Beating Heart
1
Ventricles contract,
forcing blood against
atrioventricular valve
cusps.
2
Atrioventricular
valves close.
3
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
Cusps of
atrioventricular
valve (closed)
Blood in
ventricle
The Beating Heart
Aorta
Pulmonary
trunk
As ventricles contract
and intraventricular
pressure rises, blood
is pushed up against
semilunar valves,
forcing them open.
(a) Semilunar valves open
As ventricles relax
and intraventricular
pressure falls, blood
flows back from
arteries, filling the
cusps of semilunar
valves and forcing
them to close.
(b) Semilunar valves closed
Heart Sounds
• “Lub-dub”  sound of valves closing
– First sound “lub”
• The AV valves closing
– Second sound “dub”
• The semilunar valves closing
Heart Sounds
Pulmonary valve
“Lub”
Aortic valve
Area of cutaway
Mitral valve
Myocardium
Tricuspid valve
Tricuspid
(right atrioventricular)
valve
Mitral
(left atrioventricular)
valve
Aortic
valve
“dub”
Pulmonary
valve
Fibrous
skeleton
Anterior
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
Superior vena cava (SVC)
Inferior vena cava (IVC)
Coronary sinus
SVC
Right
atrium
Tricuspid
valve
Right
ventricle
Pulmonary
semilunar valve
Pulmonary
trunk
Pulmonary
trunk
Coronary
sinus
Tricuspid
valve
Right
atrium
IVC
Pulmonary
semilunar
valve
Right
ventricle
Oxygen-poor blood
To heart returns from the body
tissues back to the heart.
Two pulmonary arteries
To lungs
carry the blood to the
lungs (pulmonary circuit)
Pulmonary
to be oxygenated.
arteries
Oxygen-rich blood
Oxygen-poor blood
To body
Oxygen-rich blood is
delivered to the body
tissues (systemic circuit).
Oxygen-rich blood returns To heart
to the heart via the four
pulmonary veins.
Aorta
Mitral
valve
Left
ventricle
Aortic
semilunar
valve
Aorta
Aortic
semilunar
valve
Pulmonary
veins
Left
atrium
Left
ventricle
Mitral
valve
Left
atrium
Four
pulmonary
veins
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
Left
ventricle
Right
ventricle
Interventricular
septum
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
Microscopic Anatomy of Cardiac Muscle
Nucleus
Intercalated discs
Cardiac muscle cell
Gap junctions
Fasciae adherens
(a)
Cardiac
muscle cell
Mitochondrion
Nucleus
Intercalated
disc
Mitochondrion
T tubule
Sarcoplasmic
reticulum
(b)
Z disc
Nucleus
Sarcolemma
I band
A band
I band
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
Superior vena cava
Right atrium
1 The Sinoatrial (SA)
node (pacemaker)
generates impulses.
Internodal pathway
2 The impulses
Left atrium
pause (0.1 sec) at the
Atrioventricular
(AV) node.
3 The atrioventricular
Purkinje
fibers
4 The bundle branches
Interventricular
septum
(AV) bundle of His
connects the atria to
the ventricles.
conduct the impulses
through the interventricular
septum.
5 The Purkinje fibers
stimulate the contractile
cells of both ventricles.
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
The vagus nerve
(parasympathetic)
decreases heart rate.
Dorsal motor nucleus
of vagus
Cardioacceleratory
center
Sympathetic
trunk
ganglion
Cardioinhibitory
center
Medulla oblongata
Thoracic spinal cord
Sympathetic trunk
Sympathetic cardiac
nerves increase heart rate
and force of contraction.
AV node
SA node
Parasympathetic fibers
Sympathetic fibers
Interneurons
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
Aorta
Pulmonary
trunk
Superior
vena cava
Left atrium
Anastomosis
(junction of
vessels)
Left
coronary
artery
Right
atrium
Right
coronary
artery
Right
ventricle
Circumflex
artery
Left
ventricle
Right
marginal
artery
Superior
vena cava
Great
cardiac
vein
Anterior
cardiac
veins
Coronary
sinus
Anterior
interventricular
artery
Posterior
interventricular
artery
(a) The major coronary arteries
Small
cardiac vein
Middle cardiac vein
(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!
4a
4
Aorta
Superior
vena cava
Tubular
heart
Ventricle
2
1
Pulm trunk
Foramen
ovale
Atrium
3
Ductus
arteriosis
Ventricle
Inferior
vena cava
Ventricle
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
Narrowed
aorta
Occurs in
~1 in every
500 births
Occurs in
~1 in every
1500 births
(a) Ventricular septal defect.
(b) Coarctation of the aorta.
The superior part of the interA part of the aorta is narrowed,
ventricular septum fails to form;
increasing the workload of
thus, blood mixes between the
the left ventricle.
two ventricles. More blood is
shunted from left to right because
the left ventricle is stronger.
Occurs in
~1 in every
2000 births
(c) Tetralogy of Fallot.
Multiple defects (tetra = four):
(1) Pulmonary trunk too narrow
and 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 Vessels
Wed Lecture: Blood Vessels
Wed Lab: Blood Vessels &
Respiratory Sys