Download The Cardiovascular System

The Cardiovascular (CV) System
A closed system of the heart & blood
vessels
The heart pumps blood
Blood vessels allow blood to circulate
to all parts of the body
The function of the CV system is to
deliver oxygen & nutrients & to remove
carbon dioxide & other waste products
The Heart
Location
Thorax between the lungs in the
inferior mediastinum
Orientation
Pointed apex directed toward left hip
Base points toward right shoulder
About the size of your fist
The Heart: Coverings
Pericardium—a double-walled sac
Fibrous pericardium is loose &
superficial
Serous membrane is deep to the
fibrous pericardium & composed of
two layers
Visceral pericardium
Next to heart; also known as
the epicardium
Parietal pericardium
Outside layer that lines the
inner surface of the fibrous
pericardium
Serous fluid fills the space between
the layers of pericardium
The Heart: Heart Wall
Three layers
Epicardium
Outside layer
This layer is the visceral
pericardium
Connective tissue layer
Myocardium
Middle layer
Mostly cardiac muscle
Endocardium
Inner layer
Endothelium
The Heart: Chambers
Right & left side act as separate pumps
Four chambers
Atria
Receiving chambers
Right atrium
Left atrium
Ventricles
Discharging chambers
Right ventricle
Left ventricle
Differences in Right & Left
Ventricles
The Heart: Septa
Interventricular septum
Separates the two ventricles
Interatrial septum
Separates the two atria
The Heart: Chambers
The Heart: Valves
Allow blood to flow in only one direction
to prevent backflow
Four valves
Atrioventricular (AV) valves—
between atria & ventricles
Bicuspid (mitral) valve (left side
of heart)
Tricuspid valve (right side of
heart)
Semilunar valves—between ventricle
& artery
Pulmonary semilunar valve
Aortic semilunar valve
The Heart: Valves
AV valves
Anchored in place by chordae
tendineae (“heart strings”)
Open during heart relaxation &
closed during ventricular contraction
Semilunar valves
Closed during heart relaxation but
open during ventricular contraction
Notice these valves operate opposite of
one another to force a one-way path of
blood through the heart
Systemic & Pulmonary Circulations
Systemic circulation
Blood flows from the left side of the
heart through the body tissues &
back to the right side of the heart
Pulmonary circulation
Blood flows from the right side of the
heart to the lungs & back to the left
side of the heart
The Heart: Associated Great Vessels
Arteries (aa.)
Aorta
Leaves left ventricle
Pulmonary aa.
Leave right ventricle
The Heart: Associated Great Vessels
Veins (vv.)
Superior & inferior venae cavae
Enter right atrium
Pulmonary vv. (four)
Enter left atrium
The Heart
Blood Flow Through the Heart
Superior & inferior venae cavae dump
blood into the right atrium
From right atrium, through the tricuspid
valve, blood travels to the right ventricle
From the right ventricle, blood leaves the
heart as it passes through the pulmonary
semilunar valve into the pulmonary trunk
Pulmonary trunk splits into right & left
pulmonary aa. that carry blood to the
lungs
Blood Flow Through the Heart
Oxygen is picked up & carbon dioxide is
dropped off by blood in the lungs
Oxygen-rich blood returns to the heart
through the four pulmonary vv.
Blood enters the left atrium & travels
through the bicuspid valve into the left
ventricle
From the left ventricle, blood leaves the
heart via the aortic semilunar valve &
aorta
Systemic & Pulmonary Circulations
Coronary Circulation
Blood in the heart chambers does not
nourish the myocardium
The heart has its own nourishing
circulatory system consisting of
Coronary aa.—branch from the
aorta to supply the heart muscle with
oxygenated blood
Cardiac vv.—drain the myocardium
of blood
Coronary sinus—a large vein on the
posterior of the heart, receives blood
from cardiac vv.
Blood empties into the right atrium via
the coronary sinus
The Heart: Conduction System
Intrinsic conduction system (nodal
system)
Heart muscle cells contract, without
nerve impulses, in a regular,
continuous way
The Heart: Conduction System
Special tissue sets the pace
Sinoatrial node = SA node
(“pacemaker”), is in the right
atrium
Atrioventricular node = AV
node, is at the junction of the
atria & ventricles
Atrioventricular bundle = AV
bundle (bundle of His), is in the
interventricular septum
Bundle branches are in the
interventricular septum
Purkinje fibers spread within the
ventricle wall muscles
Heart Contractions
Contraction is initiated by the sinoatrial
node (SA node)
Sequential stimulation occurs at other
autorhythmic cells
Force cardiac muscle depolarization in
one direction—from atria to ventricles
Heart Contractions
Once SA node starts the heartbeat
Impulse spreads to the AV node
Then the atria contract
At the AV node, the impulse passes
through the AV bundle, bundle branches,
& Purkinje fibers
Blood is ejected from the ventricles to the
aorta & pulmonary trunk as the
ventricles contract
Heart Contractions
Tachycardia—rapid heart rate over 100
beats per minute
Bradycardia—slow heart rate less than 60
beats per minutes
The Heart: Cardiac Cycle
Atria contract simultaneously
Atria relax, then ventricles contract
Systole = contraction
Diastole = relaxation
Filling Heart Chambers: Cardiac
Cycle
The Heart: Cardiac Cycle
Cardiac cycle—events of one complete
heart beat
Mid-to-late diastole—blood flows
from atria into ventricles
Ventricular systole—blood pressure
builds before ventricle contracts,
pushing out blood
Early diastole—atria finish refilling,
ventricular pressure is low
The Heart: Cardiac Output
Cardiac output (CO)
Amount of blood pumped by each
side (ventricle) of the heart in one
minute
Stroke volume (SV)
Volume of blood pumped by each
ventricle in one contraction (each
heartbeat)
Usually remains relatively constant
About 70 mL of blood is pumped out
of the left ventricle with each
heartbeat
Heart rate (HR)
Typically 75 beats per minute
The Heart: Cardiac Output
CO = HR  SV
CO = HR (75 beats/min)  SV (70
mL/beat)
CO = 5250 mL/min
Starling’s law of the heart—the more the
cardiac muscle is stretched, the stronger
the contraction
Changing heart rate is the most common
way to change cardiac output
The Heart: Regulation of Heart Rate
Increased heart rate
Sympathetic nervous system
Crisis
Low blood pressure
Hormones
Epinephrine
Thyroxine
Exercise
Decreased blood volume
The Heart: Regulation of Heart Rate
Decreased heart rate
Parasympathetic nervous system
High blood pressure or blood volume
Decreased venous return
Cardiac Output Regulation
Blood Vessels: The Vascular System
Transport blood to the tissues & back
Carry blood away from the heart
Aa.
Arterioles
Exchanges between tissues & blood
Capillary beds
Return blood toward the heart
Venules
Vv.
Blood Vessels: Microscopic Anatomy
Three layers (tunics)
Tunic intima
Endothelium
Tunic media
Smooth muscle
Controlled by sympathetic
nervous system
Tunic externa
Mostly fibrous connective tissue
Blood Vessels: The Vascular System
Differences Between Blood Vessels
Walls of aa. are the thickest
Lumens of vv. are larger
Larger vv. have valves to prevent
backflow
Skeletal muscle “milks” blood in vv.
toward the heart
Walls of capillaries are only one cell layer
thick to allow for exchanges between
blood & tissue
Blood Vessels: The Vascular System
Movement of Blood Through Vessels
Most arterial blood is pumped by the
heart
Vv. use the milking action of muscles to
help move blood
Capillary Beds
Capillary beds consist of two types of
vessels
Vascular shunt—vessel directly
connecting an arteriole to a venule
True capillaries—exchange vessels
Oxygen & nutrients cross to cells
Carbon dioxide & metabolic
waste products cross into blood
Major Aa. of System Circulation
Aorta
Largest artery in the body
Leaves from the left ventricle of the
heart
Regions
Ascending aorta—leaves the left
ventricle
Aortic arch—arches to the left
Thoracic aorta—travels
downward through the thorax
Abdominal aorta—passes
through the diaphragm into the
abdominopelvic cavity
Major Aa. of System Circulation
Arterial branches of the ascending aorta
Right & left coronary aa. serve the
heart
The Heart
Major Aa. of Systemic Circulation
Arterial branches of the aortia arch(BCS)
Brachiocephalic trunk splits into the
Right common carotid artery
Right subclavian artery
Left common carotid artery splits
into the
Left internal & external carotid
aa.
Left subclavian artery branches into
the
Vertebral artery
In the axilla, the subclavian
artery becomes the axillary
artery  brachial artery 
radial & ulnar aa.
Major Aa. of Systemic Circulation
Arterial branches of the thoracic aorta
Intercostal aa. supply the muscles of
the thorax wall
Other branches of the thoracic aorta
supply the
Lungs (bronchial aa.)
Esophagus (esophageal aa.)
Diaphragm (phrenic aa.)
Major Aa. of Systemic Circulation
Arterial branches of the abdominal aorta
Celiac trunk is the first branch of the
abdominal aorta. Three branches are
Left gastric artery (stomach)
Splenic artery (spleen)
Common hepatic artery (liver)
Superior mesenteric artery supplies
most of the small intestine & first half
of the large intestine
Major Aa. of Systemic Circulation
Arterial branches of the abdominal aorta
Left & right renal aa. (kidney)
Left & right gonadal aa.
Ovarian aa. in females serve the
ovaries
Testicular aa. in males serve the
testes
Lumbar aa. serve muscles of the
abdomen & trunk
Major Aa. of Systemic Circulation
Arterial branches of the abdominal aorta
Inferior mesenteric artery serves the
second half of the large intestine
Left & right common iliac aa. are the
final branches of the aorta
Internal iliac aa. serve the pelvic
organs
External iliac aa. enter the thigh
 femoral artery  popliteal
artery  anterior & posterior
tibial aa.
Major Vv. of Systemic Circulation
Superior & inferior vena cava enter the
right atrium of the heart
Superior vena cava drains the head &
arms
Inferior vena cava drains the lower
body
The Heart
Major Vv. of Systemic Circulation
Vv. draining into the superior vena cava
Radial & ulnar vv.  brachial vein
 axillary vein
These vv. drain the arms
Cephalic vein drains the lateral
aspect of the arm & empties into the
axillary vein
Basilic vein drains the medial aspect
of the arm & empties into the
brachial vein
Basilic & cephalic vv. are jointed at
the median cubital vein (elbow area)
Major Vv. of Systemic Circulation
Vv. draining into the superior vena cava
Subclavian vein receives
Venous blood from the arm via
the axillary vein
Venous blood from skin &
muscles via external jugular vein
Vertebral vein drains the posterior
part of the head
Internal jugular vein drains the dural
sinuses of the brain
Major Vv. of Systemic Circulation
Vv. draining into the superior vena cava
Left & right brachiocephalic vv.
receive venous blood from the
Subclavian vv.
Vertebral vv.
Internal jugular vv.
Brachiocephalic vv. join to form the
superior vena cava  right atrium of
heart
Azygous vein drains the thorax
Major Vv. of Systemic Circulation
Vv. draining into the inferior vena cava
Anterior & posterior tibial vv. &
fibial vv. drain the legs
Posterior tibial vein  popliteal vein
 femoral vein  external iliac vein
Great saphenous vv. (longest vv. of
the body) receive superficial drainage
of the legs
Each common iliac vein (left & right)
is formed by the union of the internal
& external iliac vein on its own side
Major Vv. of Systemic Circulation
Vv. draining into the inferior vena cava
Right gonadal vein drains the right
ovary in females & right testicle in
males
Left gonadal vein empties into the left
renal vein
Left & right renal vv. drain the
kidneys
Hepatic portal vein drains the
digestive organs & travels through
the liver before it enters systemic
circulation
Major Vv. of Systemic Circulation
Vv. draining into the inferior vena cava
Left & right hepatic vv. drain the
liver
Arterial Supply of the Brain
Internal carotid aa. divide into
Anterior & middle cerebral aa.
These aa. supply most of the
cerebrum
Vertebral aa. join once within the skull to
form the basilar artery
Basilar artery serves the brain stem
& cerebellum
Arterial Supply of the Brain
Posterior cerebral aa. form from the
division of the basilar artery
These aa. supply the posterior
cerebrum
Circle of Willis
Anterior & posterior blood supplies are
united by small communicating arterial
branches
Result—complete circle of connecting
blood vessels called cerebral arterial circle
or circle of Willis
Arterial Supply of the Brain
Fetal Circulation
Fetus receives exchanges of gases,
nutrients, & wastes through the placenta
Umbilical cord contains three vessels
Umbilical vein—carries blood rich in
nutrients & oxygen to the fetus
Umbilical aa. (2)—carry carbon
dioxide & debris-laden blood from
fetus to placenta
Fetal Circulation
Blood flow bypasses the liver through the
ductus venosus & enters the inferior vena
cava  right atrium of heart
Blood flow bypasses the lungs
Blood entering right atrium is
shunted directly into the left atrium
through the foramen ovale
Ductus arteriosus connects the aorta
& pulmonary trunk (becomes
ligamentum arteriosum at birth)
Fetal Circulation
Hepatic Portal Circulation
Vv. of hepatic portal circulation drain
Digestive organs
Spleen
Pancreas
Hepatic portal vein carries this blood to
the liver
Liver helps maintain proper glucose, fat,
& protein concentrations in blood
Hepatic Portal Circulation
Major vessels of hepatic portal circulation
Inferior & superior mesenteric vv.
Splenic vein
Left gastric vein
Pulse
Pressure wave of blood
Monitored at “pressure points” in aa.
where pulse is easily palpated
Pulse averages 70–76 beats per minute at
rest
Blood Pressure
Measurements by health professionals are
made on the pressure in large aa.
Systolic—pressure at the peak of
ventricular contraction
Diastolic—pressure when ventricles
relax
Write systolic pressure first &
diastolic last (120/80 mm Hg)
Pressure in blood vessels decreases as
distance from the heart increases
Comparison of Blood Pressures in
Different Vessels
Measuring Arterial Blood Pressure
Blood Pressure: Effects of Factors
BP is blood pressure
BP is affected by age, weight, time of
day, exercise, body position,
emotional state
CO is the amount of blood pumped out of
the left ventricle per minute
PR is peripheral resistance, or the
amount of friction blood encounters as it
flows through vessels
Narrowing of blood vessels &
increased blood volume increases PR
BP = CO  PR
Blood Pressure: Effects of Factors
Neural factors
Autonomic nervous system
adjustments (sympathetic division)
Renal factors
Regulation by altering blood volume
Renin—hormonal control
Blood Pressure: Effects of Factors
Temperature
Heat has a vasodilating effect
Cold has a vasoconstricting effect
Chemicals
Various substances can cause
increases or decreases
Diet
Factors Determining Blood Pressure
Variations in Blood Pressure
Normal human range is variable
Normal
140–110 mm Hg systolic
80–75 mm Hg diastolic
Hypotension
Low systolic (below 110 mmHG)
Often associated with illness
Hypertension
High systolic (above 140 mmHG)
Can be dangerous if it is chronic
Capillary Exchange
Substances exchanged due to
concentration gradients
Oxygen & nutrients leave the blood
Carbon dioxide & other wastes leave
the cells
Capillary Exchange: Mechanisms
Direct diffusion across plasma
membranes
Endocytosis or exocytosis
Some capillaries have gaps (intercellular
clefts)
Plasma membrane not joined by tight
junctions
Fenestrations (pores) of some capillaries
Fluid Movements at Capillary Beds
Blood pressure forces fluid & solutes out
of capillaries
Osmotic pressure draws fluid into
capillaries
Blood pressure is higher than osmotic
pressure at the arterial end of the
capillary bed
Blood pressure is lower than osmotic
pressure at the venous end of the
capillary bed
Fluid Movements at Capillary Beds
Developmental Aspects of the CV
System
A simple “tube heart” develops in the
embryo & pumps by the fourth week
The heart becomes a four-chambered
organ by the end of seven weeks
Few structural changes occur after the
seventh week
Developmental Aspects of the CV
System
Aging problems associated with the CV
system include
Venous valves weaken
Varicose vv.
Progressive atherosclerosis
Loss of elasticity of vessels leads to
hypertension
Coronary artery disease results from
vessels filled with fatty, calcified
deposits