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The
Circulatory System
A. General
1. Base
2. Apex
B. Pericardial
Membranes
1. Fibrous
pericardium
a. Fibrous CT
b. Adheres to
blood vessels at base, sternal wall of thorax, and diaphragm
2. Parietal
pericardium
3. Pericardial
cavity
a. Pericardial
fluid
4. Epicardium
(visceral pericardium)
5. Myocardium
6. Endocardium
(endothelial cells)
1. Right
Atrium
a. Tricuspid
valve
a. Papillary
muscles
b. Chordae
tendinea
c. Pulmonary
semilunar valve
3. Left
Atrium
a. Mitral
(bicuspid) valve
4. Left
Ventricle
a. Papillary muscles
large
b. Chordae
tendinae thicker and stronger
c. Aortic
semilunar valve
d. Coronary
arteries just distal to the semilunar valve
D. Path of
Blood in the Heart
E. Double
Pump
F. Heartbeat
1. Volumes
a. Stroke
volume
(1) Amount of
blood pumped by a ventricle with each beat
b. Cardiac
output
c. Amount
pumped by one ventricle in one minute
d. Usually
about 5 liters in a resting adult
2. Cardiac
Cycle (or heartbeat)
a. Systole
b. Diastole
c. Atrial
systole/ventricular diastole (0.15s) - atrial diastole/ventricular systole
(0.3s) - atrial diastole/ventricular diastole (0.4s)
d. If HR = 70
bpm then each beat = 60s/70 = 0.85s/beat; At 75 bpm each beat = 60s/75 = 0.8s;
etc.
3. Heart
Sounds
a. lub (1st
heart sound)= AV valves closing
b. dub (2nd
heart sound) = semilunar valves
c. Murmers
caused by valvular insufficiency
d. Rheumatic
fever (streptococcal infection) can cause faulty valves, especially the mitral
e. Mitral
stenosis - narrowing of opening
4. Cardiac
Conduction System
a. Heartbeat
is intrinsic
(1) Pacemaker
cells - Sinoatrial node
(2) Located in
posterior wall of right atrium
(3) Automatically
depolarize and contract, impulse spreads throughout atria
b. Pathway
(1) AV node
(a) Wall of
right atrium near septum just superior to ventricles
(b) Can act as
pacemaker if SA node is inactive (damaged)
(2) AV bundle
(bundle of His)
(a) Upper part of interventricular septum
(b) Splits into right and left bundle branches
(c) Give rise to Purkinje fibers
(3) Purkinje
fibers
(a) Innervate
Ventricles
(b) Contraction
begins at apex and spreads back toward base
5. Medical
Focus: The Electrocardiogram
a. Records
electrical activity of the heart during a cardiac cycle
b. P wave -
depolarization of atria
c. QRS
complex - depolarization of ventricles
d. T wave -
repolarization of ventricles (repolarization of atria masked by QRS complex)
e. Bradycardia
- HR < 60 bpm
f. Tachycardia
- HR > 100 bpm
g. Arrhythmia
- abnormal rhythm
h. Fibrillation
- rapid uncoordinated contractions
6. Regulation
of the Heartbeat
a. Nervous
system input regulates intrinsic rate
b. Cardiac
control center in medulla oblongata
c. Parasympathetic
motor impulses conducted by vagus nerve slow HR
d. Sympathetic
motor impulses speed HR
e. Sensory
input from various receptors
(i) Baroreceptors
send information about blood pressure, low BP stimulates HR; high
BP stimulates ¯ HR
f. Influence
of cerebrum and hypothalamus
g. Temperature
- cold lowers HR
h. Electrolyte
concentration - K+ and Ca++
G. Cardiac
Disorders
1. Atherosclerosis
2. Plaque
3. Coronary
blockage, ischemic heart disease
4. Angina
pectoris - insufficient oxygen supply to myocardium during exercise or stress
5. Thrombus -
stationary clot
6. Embolus -
moving clot
7. Thromboembolism
- clot breaks free and travels; emboli that block coronaries lead to myocardial
infarction
8. Thrombolytic
therapy - ballon antioplasty
9. Coronary
bypass
H. MedAlert:
Preventing Heart Attacks
1. Risk
factors:
a. Male
gender
b. Family
history
c. Tobacco
usage
d. Severe
obesity
e. Hypertension
(1) Smoking
(2) Obesity
f. Low HDL
and high LDL
g. Impaired
circulation to brain or legs
h. Diabetes
mellitus
2. Preventative
behaviors
a. EXERCISE!!
b. Stress
reduction
c. Dietary
control
d. Don't
smoke
I. Medical
Focus: Congestive Heart Failure
II. Vascular
System
A. Blood
Vessels
1. Arteries
and Arterioles
a. Layers
(1) Tunica
interna or intima - endothelium
(2) Tunica
media - elastic fibers and smooth muscle
(3) Tunica
externa or adventitia - outer CT layer
b. Arteriosclerosis
(1) CVA
2. Capillaries
3. Veins and
Venules
a. Varicose
Veins
(1) Hemorrhoids
4. Phlebitis
-inflammation of a vein, may lead to thromboembolism
a. Blockage
of pulmonary arteriole - pulmonary embolism
B. Path of
Circulation
1. Pulmonary
Circulation
2. Systemic
Circulation
a. Major
Systemic Arteries
b. Major
Systemic Veins
3. Vital
Systemic Circulatory Routes
a. Blood
Supply to the Brain
(1) Vertebral
and internal carotid arteries
(2) Join to
form the circle of Willis near pituitary
(3) Offer
alternate routes of flow if one gets blocked
b. Blood
Supply to the Heart
(1) Right and
left coronary arteries
(2) Coronary
capillary beds
(3) Cardiac
veins
(4) Coronary
sinus, empties into right atrium
c. Blood
Supply to the Liver
(1) Hepatic
portal system carries blood from stomach, intestines, and other organs to liver
(2) Begins and
ends in capillaries, 2 sets of capillaries (one at small intestine, one at
liver) between artery (superior mesenteric) and final vein (hepatic veins to
inferior vena cava)
4. Fetal
Circulation
a. Foramen
ovale - between right and left atria
(fossa ovalis)
b. Ductus
arteriosus - between pulmonary artery and aorta (ligamentum arteriosum)
c. Umbilical
arteries and vein
d. Ductus venosus
- between umbilical vein and inferior vena cava; bypasses hepatic portal
circulation
1. Expansion
and recoil of artery walls as blood is pumped from heart
2. Indicates
heartrate
B. Blood
Pressure
2. Maintaining
Blood Pressure
a. BP = CO X
TPR
(1) Cardiac
output is amount pumped by the heart per minute
(a) CO = HR X
SV
(2) Resistance
is dependent on 3 variables
(a) Diameter
of vessel
(i) R = 1/r4
(b) Viscosity
(c) Length of
vascular bed
b. To
increase BP
(1) Increase
CO (increase HR or SV)
(a) Sympathetic
stimulation
(2) Increase
TPR
(a) Vasoconstriction
(b) Sympathetic
stimulation of vascular smooth muscle
(c) Angiotensin
II
(3) Increase
blood volume
(a) Aldosterone
(b) ADH
1. Decrease
CO (HR or SV)
a. Parasympathetic
stimulation
2. Decrease
TPR
a. Vasodilation
(1) Parasympathetic
stimulation
3. Decrease
blood volume
a. Atrial
natruiretic factor (ANF)
D. Blood Flow
in Arteries, Arterioles, and Capillaries
1. Related to
pressure differences and cross-sectional area
2. Pressure
drops from aorta to capillaries
3. Cross-sectional
area of capillary beds is huge
4. Very slow
rate of flow through capillaries allows exchange of nutrients for wastes
E. Blood Flow
in Veins and Venules
1. Pressure
is so low that the driving force is based on milking action of skeletal
muscles, respiratory movements
2. Valves
prevent backflow
F. Hypertension