Transcript Chapter 18 - Marion ISD

The Cardiovascular System
Ch. 18,19
Introduction
• Cardiovascular system
– Heart
– Blood vessels
• Arteries
• Capillaries
• Veins
Heart anatomy
Structure of the heart
• Description-hollow,
cone-shaped,
muscular pump
• 12 cm by 9 cm
• Located behind
sternum, within
mediastinum
(space)
Coverings of the heart
• Pericardium – encloses heart –
tough connective tissue.
• Fibrous pericardium surrounds visceral
serous pericardium.
– Visceral pericardium- surrounds heart
– Parietal pericardium-lines the cavity
• Paricardial cavity- space containing
serous fluid between parietal and
visceral pericardium – contains serous
fluid
Wall of the heart
• 3 layers
– Epicardiumoutermost layer
• Connective tissue
and epithelium –
contains blood vessels
and lymph vessels
– Myocardium –
cardiac muscle,
middle layer
– Endocardium –
innermost layer,
contains nervous
tissue for control of
the heart.
Skeleton of the heart
• Rings of dense connective tissue
• Surround pulmonary trunk and aorta
Heart chambers and valves
• Chambers
– Atria
– Ventricles
• Septum
• Atrioventricular (AV)
valve
– Tricuspid
– Bicuspid or mitral
• Cordae tendinae
• Pulmonary valves
• Aortic valve
Path of blood through heart
• Inferior or superior
vena cava
• Right atrium
• Right AV valve
• Right ventricle
• Pulmonary artery
• Pulmonary valve
• Lungs
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Pulmonary vein
Left atrium
Left AV valve
Left ventricle
Aorta
Aortic valve
Body
Blood supply to the heart
• Branches of aorta, carry
oxygenated blood – right and
left coronary arteries – feed
heart
• Branches from coronary
arteries feed capillaries of
myocardium
• Smaller branches of arteries –
anastomoses – alternate
pathways for blood
– Blocked artery – angina
pectoris – myocardial
infarction – heart attack
• Cardiac veins- drain blood
from heart
Heart beating
Heart
actions
• Cardiac cycle – pressure in
chambers rises/falls with
contraction/relaxation of
atria and ventricles
• Atria fill, open av valves
• Ventricles fill
• Valves close
• Ventricles contract, blood
goes through pulmonary
artery and aorta
• Ventricles relax, valves close
in vessels
Heart sounds
• Heart sounds caused by valve
closure
– First sound (lubb) – ventricles contract
and AV valves close
– Second sound (dupp) ventricles relax
and aortic and pulmonary valves close.
Cardiac conduction system
• Functional synctium – atrial
and ventricular – mass of
fibers that works as a unit
• Cardiac tissue conducts
impulses through myocardium
– cardiac conduction system.
• Sinoatrial node in right atrium
– pacemaker – self exciting
• Impulses spread through atrial
synctium then ventricular
synctium.
• Purkinje fibers contract tiny
muscles attached to chordae
tendinae
Electrocardiogram
• ECG – electrical
recording of changes
that occur in cardiac
cycle
• P wave – depolarization
of atria
• QRS complex –
depolarization of
ventricles
• T wave – ventricular
repolarization
Regulation of the cardiac
cycle
• Amount of blood pumped must adjust
according to body needs
• SA node innervated by sympathetic
and parasympathetic nervous system
divisions so CNS controls heart rate.
• Cardiac control center in medulla
oblongata – adjusts heart rate based
on blood pressure measurements from
baro receptors.
• Cerebrum/hypothalamus influence
heart rate as well
Blood vessels
• Blood vessels
– include:Arteries , arterioles,
capillaries, venules, veins
• Create closed system –
carries blood away from
heart to cells in body
then back to the heart.
Arteries and veins
• Arteries –strong, elastic
• Divide into arterioles
• Wall of artery - smooth muscles
and connective tissue
• Capable of
vasoconstriction/vasodilation –
increases/decreases blood
flow/pressure
• Clogged vessels –
artherosclerosis – diets high in
fat
– Diets high in
fruits/vegetables=add phyto
sterols to blood – scour out
plaque deposits
capillaries
• Smallest vessels – layer of
endothelium
– Allows substances to be
exchanged with cells
– More permeability in
capillaries of liver, intestines,
glands
– More metabolic activity –
higher number of capillaries
– Precapillary sphincters –
regulate amount of blood
entering capillary bed
– Capillary beds can close
down if more is needed
elsewhere.
Exchanges
in
the
capillaries
• Blood in capillaries – high
oxygen/nutrients
• Diffuse through wall to
tissue
• Plasma proteins stay in
capillary
• Hydrostatic pressure –
drives passage of
fluids/small molecules.
• Osmosis causes tissue fluid
to return to blood
• Lymphatic vessels collect
extra fluid and return it to
circulation
Venules and veins
• Venules – lead from
capillaries – merge to form
veins – veins return blood to
heart.
• 3 layers with valves to
prevent backflow
• Thinner, less muscular than
arteries
• No high pressure blood
• Function as blood reservoirs
Blood circulation
Paths of circulation
• Two divisions
– Pulmonary circuit – right
ventricle through pulmonary
artery to lungs, then pulmonary
veins to left atrium.
– Systemic circuit – carries blood
from left ventricle through
aorta to body cells and back
through veins into the left
atrium
Arterial system
Venous system
Blood pressure
• Factors that affect blood pressure
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Heart action
Blood volume
Peripheral resistance
Blood viscosity
Control of blood pressure
• adjusting Cardiac output and
Peripheral resistance
• If blood pressure increases, heart
rate slows and blood vessels dilate
• If BP drops, heart rate increases and
blood vessels constrict.
• Vasomotor center of medulla
oblongata controls
Fetal circulation
• Two umbilical arteries – carry blood to placenta
• Placenta – structure attached to uterine wall – substances
exchanged between blood of mother and baby
• Umbilical vein – returns blood from placenta to baby.
• Ductus venosus – returns blood from placenta to inferior
vena cava, bypassing liver
• Foramen ovale – opening in septum between right and left
atria that allows most of blood to bypass fetal lungs
• Ductus arteriosus-small vessel connecting pulmonary
artery with descending aorta, allows more blood to bypass
fetal lungs
• After birth: Ovale closes, Ductus arteriosus contracts
Changes after birth