Chapter 13&14 lecture-1

Chapters 13 & 14
Blood, Heart, and
Circulation
Lecture PowerPoint
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Circulatory System Components
• Cardiovascular system
– Heart: four-chambered pump
– Blood vessels: arteries, arterioles, capillaries,
venules, and veins
• Lymphatic system
– Lymphatic vessels, lymphoid tissues,
lymphatic organs (spleen, thymus, tonsils,
lymph nodes)

Circulatory System Functions
• Transportation
– Respiratory gases, nutrients, and wastes
• Regulation
– Hormonal and temperature
• Protection
– Clotting and immune

Composition of the Blood
1. Plasma: fluid part of blood
– Plasma proteins
– Serum

1. Plasma: fluid part of blood
•Nutrients and metabolites
– Glucose, amino acids, fatty acids etc
•Hormones
– Insulin, glucagon, sex hormones etc.
•Ions
– Na+
(major ion; maintains osmotic pressure)
– K+
, Ca++
, Cl-
, Mg++
etc
•Bicarbonate; important buffer
•Respiratory gasses
– O2, CO2
•Waste products
– Urea, food additives etc.

Plasma: fluid part of blood (Continued)
• Proteins constitute 7-9% of plasma
• Three types of plasma proteins: albumins, globulins, &
fibrinogen
– Albumin accounts for 60-80% (Major protein)
• Creates colloid osmotic pressure that draws H20 from
interstitial fluid into capillaries to maintain blood volume &
pressure
– Globulins
• Alpha and beta globulins transport lipid soluble molecules
• Gamma globulins are antibodies (fight infection)
– Fibrinogen
• a soluble protein that functions in clotting
• Converted to fibrin; an insoluble protein polymer
• Serum is fluid left when blood clots (plasma minus fibrinogen)

2. Formed Elements
Granulocytes
Neutrophils
Eosinophils
Basophils
Agranulocytes
Lymphocytes
Monocytes

2. Erythrocytes
– Carry oxygen
– Lack nuclei and
mitochondria
– Have a 120-day life
span
– Contain hemoglobin
and transferrin

• 3. Leukocytes
• Have nucleus, mitochondria, & amoeboid ability
• Can squeeze through capillary walls (diapedesis)
– Granular leukocytes help detoxify foreign
substances & release heparin
• Include eosinophils, basophils, & neutrophils
13-10

• 3. Leukocytes (Contd)
• Agranular leukocytes
are phagocytic &
produce antibodies
• Include lymphocytes
& monocytes
13-11

4. Platelets (thrombocytes)
- Smallest formed element
– Lack nuclei
- Very short-lived (5−9 days)
- Clot blood
- Need fibrinogen

Hematopoiesis
• Is formation of blood cells from stem cells in
bone marrow (myeloid tissue) & lymphoid
tissue
• Erythropoiesis is formation of RBCs
– Stimulated by erythropoietin (EPO) from kidney
• Leukopoiesis is formation of WBCs
– Stimulated by variety of cytokines
• = autocrine regulators secreted by immune system
13-13

Erythropoiesis
• 2.5 million RBCs
are produced/sec
• Lifespan of 120
days
• Old RBCs removed
from blood by
phagocytic cells in
liver, spleen, &
bone marrow
– Iron recycled
back into
hemoglobin
production 13-14

Blood Clotting
• Hemostasis: cessation of bleeding when a
blood vessel is damaged
• Damage exposes collagen fibers to blood,
producing:
1. Vasoconstriction
2. Formation of platelet plug
3. Formation of fibrin protein web

Blood Clotting: Platelets
• Platelets don't
stick to intact
endothelium
because of
presence of
prostacyclin
(PGI2--a
prostaglandin) &
NO
– Keep clots from
forming & are
vasodilators
13-20
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.

Consequences of Blood Clotting
in Normal Vessels

• Damage to endothelium
allows platelets to bind to
exposed collagen
– von Willebrand factor
increases bond by
binding to both
collagen & platelets
– Platelets stick to
collagen & release
ADP, serotonin, &
thromboxane A2
• = platelet release
reaction
13-21
Damaged blood vessel wall

• Some chemicals (serotonin
& thromboxane A2)
stimulate vasoconstriction,
reducing blood flow to
wound
• Other chemicals (ADP &
thromboxane A2) cause
other platelets to become
sticky & attach & undergo
platelet release reaction
– This aggregation
continues until platelet
plug is formed
13-22
Platelet aggregation

Blood Clotting: Fibrin
• Next, calcium and phospholipids (from the
platelets) convert prothrombin to the active
enzyme thrombin, which converts
fibrinogen to fibrin.

• Fibrinogen is converted to fibrin via one of
two pathways:
1. Intrinsic: Activated by exposure to collagen
or glass which activates a cascade of other
blood factors.

2. Extrinsic: Initiated by tissue factor (factor III).
This is a more direct pathway.
• Vitamin K is needed for both pathways.

13-25
Intrinsic: Activated by
exposure to collagen
Extrinsic: Initiated by tissue
factor (factor III).

• Platelet plug becomes infiltrated by meshwork of fibrin
• Clot now contains platelets, fibrin & trapped RBCs
– Platelet plug undergoes plug contraction to form more
compact plug
Role of Fibrin
13-23

Anticoagulants
• Clotting can be prevented with certain
drugs:
– Calcium chelators (sodium citrate or EDTA)
– Heparin: blocks thrombin
– Coumarin: inhibits vitamin K

Dissolution of Clots
• When damage is repaired, activated
factor XII causes activation of kallikrein
– Kallikrein converts plasminogen to plasmin
• Plasmin digests fibrin, dissolving clot
13-26

Structure of the Heart
• Right atrium: receives
deoxygenated blood from the
body
• Left atrium: receives
oxygenated blood from the
lungs
• Right ventricle: pumps
deoxygenated blood to the
lungs
• Left ventricle: pumps
oxygenated blood to the body
• Chambers separated by
fibrous skeleton

Pulmonary and Systemic Circulations
• Pulmonary: between heart
and lungs
– Blood pumps to lungs via
pulmonary arteries.
– Blood returns to heart via
pulmonary veins.
• Systemic: between heart
and body tissues
– Blood pumps to body
tissues via aorta.
– Blood returns to heart via
superior and inferior
venae cavae.

• Resistance in systemic circuit > pulmonary
– Amount of work done by left ventricle pumping to systemic is
5-7X greater
• Causing left ventricle to be more muscular (3-4X thicker)
Pulmonary & Systemic Circulations
continued
13-34

Valves of the Heart
• Atrioventricular
valves: located
between the atria
and the ventricles
– Tricuspid: between
right atrium and
ventricle
– Bicuspid: between
left atrium and
ventricle

Valves of the Heart
• Semilunar valves:
located between
the ventricles and
arteries leaving the
heart
– Pulmonary:
between right
ventricle and
pulmonary trunk
– Aortic: between left
ventricle and aorta

Valves of the Heart
• Opening & closing of
valves results from
pressure differences
– High pressure of
ventricular contraction
is prevented from
everting AV valves by
contraction of papillary
muscles which are
connected to AVs by
chorda tendinea
13-37

Three Types of Muscle
• Skeletal Muscle
– Voluntary
– Striated
– Not interconnected
– Long and not branched
• Cardiac Muscle
– Involuntary
– Striated
– Interconnected via intercalated
discs (Gap junctions)
– Functional syncytium
• Smooth Muscle
– Involuntary
– Non-striated
– Most have gap junctions

• Pericardial Sac:
• Anchors the
heart
• Reduces friction
against the rib
cage
Structure of Heart Wall

III. Electrical Activity of the Heart
and the Electrocardiogram

Electrical Activity of the Heart
• Cardiac muscle cells are interconnected by gap junctions
called intercalated discs.
– Once stimulation is applied, it flows from cell to cell.
– The area of the heart that contracts from one
stimulation event is called a myocardium.
– The atria and ventricles are separated electrically by
the fibrous skeleton.

Autorhythmicity: Rhythmic beat of heart
produced by producing its own action
potentials
Authorhythmic cells: Special cardiomyocytes
that initiate and conduct action potentials
At −40mV, voltage-gated Ca2+
channels open, triggering
action potential and
contraction.
Repolarization occurs with the
opening of voltage-gated K+
channels

• Sinoatrial node: “pacemaker”; located in
right atrium
– Pacemaker potential: slow, spontaneous
depolarization

• Pacemaker cells in the sinoatrial node
depolarize spontaneously, but the rate at
which they do so can be modulated:
– Epinephrine and norepinephrine increase the
heart rate.
– Parasympathetic neuron slows heart rate.

• Myocardial action potentials
– Cardiac muscle cells have a resting potential of
−90mV.
– They are depolarized to threshold by action potentials
from the SA node.
Voltage-gated Na+
channels
open, and membrane potential
plateaus at 15mV for 200−300
msec.
Due to balance between
slow influx of Ca2+
and
efflux of K+
More K+
are opened, and
repolarization occurs.

– Action potentials
spread via
intercalated discs
(gap junctions).
– AV node at base of
right atrium and
bundle of His
conduct stimulation
to ventricles.

– In the interventricular
septum, the bundle
of His divides into
bundle branches.
– Branch bundles
become Purkinje
fibers, which
stimulate ventricular
contraction.

– Action potentials from the SA
node spread rapidly.
• 0.8–1.0 meters/second
– At the AV node, APs slow
down.
• 0.03−0.05 m/sec
• This accounts for half of
the time delay between
atrial and ventricular
contraction.
– The speed picks up in the
bundle of His, reaching 5
m/sec in the Purkinje fibers.
– Ventricles contract 0.1–0.2
seconds after atria.

Refractory Periods
• Because the atria and
ventricles contract as
single units, they cannot
sustain a contraction.
• Because the action
potential of cardiac cells
is long, they also have
long refractory periods
before they can contract
again.

Electrocardiogram
• This instrument records the electrical
activity of the heart by picking up the
movement of ions in body tissues in
response to this activity.

Electrocardiogram
• P wave: atrial depolarization
• QRS wave: ventricular
depolarization
• S-T segment: plateau phase
• T wave: ventricular
repolarization

Heart Sounds
• Produced by closing valves
- “Lub” = closing of AV valves
• Occurs at ventricular systole
- “Dub” = closing of semilunar valves
• Occurs at ventricular diastole

ECG and Heart Sounds
• Lub occurs after
the QRS wave.
• Dub occurs at the
beginning of the
T wave.

Heart Murmur
• Abnormal heart sounds produced by
abnormal blood flow through heart.
– Many caused by defective heart valves.
• Mitral stenosis: Mitral valve calcifies and
impairs flow between left atrium and
ventricle.
– May result in pulmonary hypertension.

Heart Murmur
• Incompetent valves: do not
close properly
– May be due to damaged
papillary muscles
• Septal defects: holes in
interventricular or interatrial
septum
– Blood crosses sides.

Cardiac Cycle
• Repeating pattern
of contraction and
relaxation of the
heart.
– Systole: contraction
of heart muscles
– Diastole: relaxation
of heart muscles

Cardiac Cycle
1. Ventricles begin contraction, pressure
rises, and AV valves close (lub).
2. Pressure builds, semilunar valves open,
and blood is ejected into arteries.
1. Pressure in ventricles falls; semilunar
valves close (dub).

Cardiac Cycle
4. Pressure in ventricles falls below that of
atria, and AV valve opens. Ventricles fill.
5. Atria contract, sending last of blood to
ventricles

Blood Vessels
• Arteries
• Arterioles
• Capillaries
• Venules
• Veins

Parallel Arrangement of Blood Flow
Allows:
All organs to receive blood of same composition
Blood flow through an organ system to be adjusted according to need
Blood constantly reconditioned
Reconditioning organs (digestive organs, Kidneys, Skin) receive more blood
than their own need

Blood Vessels
• Innermost layer of all vessels is
the endothelium
• Capillaries are made of only
endothelial cells
• Arteries & veins have 3 layers
called tunica externa, media, &
interna
– Externa is connective tissue
– Media is mostly smooth
muscle
– Interna is made of
endothelium, basement
membrane, & elastin
• Although have same basic
elements, arteries & veins are
quite different

Arteries
• Large arteries are muscular & elastic
– Contain lots of elastin so very elastic
– Expand during systole & recoil during diastole
• Helps maintain smooth blood flow during diastole
• Serve as rapid transit pathway to the tissues and pressure
reservoir during diastole
13-67

Arterioles
• Small arteries & arterioles are muscular
– Provide most resistance in circulatory system
– Arterioles cause greatest pressure drop
– Mostly connect to capillary beds
• Some connect directly to veins to form arteriovenous
anastomoses
13-68

Physical Laws Describing Blood
Flow
• Blood flows through vascular system when there is pressure
difference (∆P) at its two ends
– Flow rate is directly proportional to difference (∆P = P1 - P2)
14-33

Physical Laws Describing Blood
Flow
Flow rate is inversely proportional to resistance
Flow = ∆P/R
Resistance is directly proportional to length of vessel (L) & viscosity of
blood (η) and inversely proportional to 4th power of radius
So diameter of vessel is very important for resistance because
viscosity and length of the vessel do not change
Mean Arterial Pressure:
Diastolic Pressure (80) + 1/3rd
Pulse Pressure (13.33)
Pulse Pressure = Systolic Pressure (120) – Diastolic Pressure (80)
So MAP for a normal BP is 80 + 13.33 = 93.33
14-34

Relationship between blood flow,
radius & resistance
14-35
Relationship between blood flow,
radius & resistance

Vasoconstriction and
Vasodilation

Intrinsic Regulation of Blood Flow
(Autoregulation)
• Maintains fairly constant blood flow despite BP
variation
• Myogenic control mechanisms occur in some
tissues because vascular smooth muscle
contracts when stretched & relaxes when not
stretched
– E.g. decreased arterial pressure causes cerebral vessels to
dilate & vice versa. Brain requires a constant supply of
blood
14-39

• Metabolic control mechanism matches blood
flow to local tissue needs
• Low O2 or pH or high CO2, adenosine, or K+
from high metabolism cause vasodilation which
increases blood flow (= active hyperemia)
• Reactive hyperemia: a local vosodilation in
response to stopping or constriction of blood
flow to the area.
(Autoregulation) continued
14-40

• Local Histamine Release: In injuries or
allergies local histamine release causes
vasodilation
• Local Heat or Cold: Used therapeutically to
reduce vasodilation by applying cold packs to
affected areas
(Autoregulation) continued
14-40

• Sympathoadrenal activation (Neural Control)
causes increased CO & resistance in periphery
& viscera
– Blood flow to skeletal muscles is increased
• Because their arterioles dilate in response to Epi & their
Symp fibers release ACh which also dilates their
arterioles
• Thus blood is shunted away from visceral & skin to
muscles
Endocrine control: Many hormones affect the radii of
arterioles; e.g., epinephine, angiotensin and vasopressin
cause vasoconstriction
Extrinsic Regulation of Blood Flow
14-36

Paracrine Regulation of Blood Flow
• Endothelium produces several paracrine
regulators that promote relaxation:
– Nitric oxide (NO), bradykinin, prostacyclin
• NO is involved in setting resting “tone” of vessels
– Levels are increased by Parasymp activity
– Vasodilator drugs such as nitroglycerin or Viagra act thru NO
• Endothelin 1 is vasoconstrictor produced by
endothelium
14-38

Aerobic Requirements of the Heart
• The coronary arteries supply blood to a
massive number of capillaries (2,500–
4,000 per cubic mm tissue). Heart is the
most perfused tissue in human body
– Unlike most organs, blood flow is restricted
during systole. Cardiac tissue therefore has
myoglobin to store oxygen during diastole to
be released in systole.

Circulatory Changes During Exercise
• Cardiac output
can increase
5X due to
increased
cardiac rate.
• Stroke volume
can increase
some due to
increased
venous return.

Cerebral Circulation
• The brain cannot tolerate much variation
in blood flow.
– At high pressure, vasoconstriction occurs to
protect small vessels from damage and
stroke.
– When blood pressure falls, cerebral vessels
automatically dilate.

• Provide extensive surface area for exchange
• Blood flow through a capillary bed is determined by state of
precapillary spincters of arteriole supplying it
Capillaries
13-69

• In continuous capillaries, endothelial cells are tightly joined
together
– Have narrow intercellular channels that permit exchange of
molecules smaller than proteins
– Present in muscle, lungs, adipose tissue
• Fenestrated capillaries have wide intercellular pores
– Very permeable
– Present in kidneys, endocrine glands, intestines.
• Discontinuous capillaries have large gaps in endothelium
• Are large & leaky
• Present in liver, spleen, bone marrow.
Types of Capillaries
13-70

Exchange across capillary wall

Exchange of Fluid between
Capillaries & Tissues
• Distribution of ECF between blood & interstitial
compartments is in state of dynamic equilibrium
• Movement out of capillaries is driven by
hydrostatic pressure exerted against capillary
wall
– Promotes formation of tissue fluid
– Net filtration pressure= hydrostatic pressure in
capillary (17-37 mm Hg) - hydrostatic pressure of
ECF (1 mm Hg)
14-19

Cutaneous Blood Flow
• The skin can tolerate the greatest fluctuations in
blood flow.
• The skin helps control body temperature in a
changing environment by regulating blood flow =
thermoregulation.
– Increased blood flow to capillaries in the skin releases
heat when body temperature increases.
– Sweat is also produced to aid in heat loss.
– Vasoconstriction of arterioles keeps heat in the body
when ambient temperatures are low.

Cutaneous Blood Flow
• Thermoregulation
is aided by
arteriovenous
anastomoses,
which shunt blood
from arterioles
directly to venules.

• Contain majority of blood in circulatory system
• Capicitance vessels
• Very compliant (expand readily), but not elastic
• Contain very low pressure (about 2mm Hg)
– Insufficient to return blood to heart
– Have valves for one way flow
Veins
13-71

Venous Return continued
• Veins hold most of
blood in body (70%) &
are thus called
capacitance vessels
– Have thin walls &
stretch easily to
accommodate more
blood without
increased pressure
(=higher
compliance)
• Have only 0-
10 mm Hg
pressure
14-16

Venous Return
• Is return of blood to
heart via veins
• Controls EDV & thus SV
& CO
• Dependent on:
– Blood volume &
venous pressure
– Vasoconstriction
caused by Symp
– Skeletal muscle
pumps
– Pressure drop during
inhalation
14-15

• Blood is moved
toward heart by
contraction of
surrounding skeletal
muscles (skeletal
muscle pump)
– & pressure drops
in chest during
breathing
– 1-way venous
valves ensure
blood moves only
toward heart
Venous Return
13-72

Functions of the Lymphatic System
• Transports excess interstitial fluid (lymph) from
tissues to the veins
• Produces and houses lymphocytes for the
immune response
• Transports absorbed fats from intestines to
blood

Lymphatic System continued
• Lymphatic capillaries
are closed-end tubes
that form vast networks
in intercellular spaces
– Very porous, absorb
proteins,
microorganisms, fat
13-88

Vessels of the Lymphatic System
• Lymphatic capillaries: smallest;
found within most organs
– Interstitial fluids, proteins,
microorganisms, and fats can
enter.
• Lymph ducts: formed from
merging capillaries
– Similar in structure to veins
– Lymph is filtered through
lymph nodes
• Tonsils, thymus, spleen
– Sites for lymphocyte
production

Organs of the Lymphatic System

Edema
• Normally filtration, osmotic reuptake, & lymphatic drainage
maintain proper ECF levels
• Edema is excessive accumulation of ECF resulting from:
– High blood pressure
– Venous obstruction
– Leakage of plasma proteins into ECF
– Myxedema (excess production of glycoproteins in
extracellular matrix) from hypothyroidism
– Low plasma protein levels resulting from liver disease
– Obstruction of lymphatic drainage
14-23

Blood Pressure (BP)
• Is controlled mainly by HR, SV, & peripheral
resistance
– An increase in any of these can result in increased
BP
• Sympathoadrenal activity raises BP via arteriole
vasoconstriction & by increased CO
• Kidney plays role in BP by regulating blood
volume & thus stroke volume
14-54

• Is volume of blood pumped/min by each
ventricle
• Stroke volume (SV) = blood pumped/beat by
each ventricle
• CO = SV (`70 ml/min) x HR (`70 beats/min)
=4900ml/min
• Total blood volume is about 5.5L
Cardiac Output (CO)
14-4

Regulation of Cardiac Rate
• Without neuronal influences, SA node will drive
heart at rate of its spontaneous activity
• Normally Symp & Parasymp activity influence
HR (chronotropic effect)
• Autonomic innervations of SA node is main
controller of HR
– Sympathetic NS increases heart rate by releasing
epinephrine and Nor-epinephrine
– Parasympathetic NS innervates at the SA node
and releases Acetylcholine. The affect is to reduce
the heart rate
14-5

Stroke Volume
• Is determined by 3 variables:
– End diastolic volume (EDV) = volume of blood in
ventricles at end of diastole
– Total peripheral resistance (TPR) = impedance to
blood flow in arteries
– Contractility = strength of ventricular contraction
14-9

• EDV is workload (preload) on heart prior to
contraction
– SV is directly proportional to preload & contractility
• Strength of contraction varies directly with EDV
• Total peripheral resistance = afterload which
impedes ejection from ventricle
• Ejection fraction is SV/ EDV
– Normally is 60%; useful clinical diagnostic tool
Regulation of Stroke Volume
14-10

Frank-Starling Law of the Heart
• States that strength
of ventricular
contraction varies
directly with EDV
– Is an intrinsic
property of
myocardium
– As EDV
increases,
myocardium is
stretched more,
causing greater
contraction & SV
Fig 14.2
14-11

Frank-Starling Law of the Heart continued
• (a) is state of myocardial sarcomeres just before filling
– Actins overlap, actin-myosin interactions are reduced &
contraction would be weak
• In (b, c & d) there is increasing interaction of actin & myosin
allowing more force to be developed
14-12

Extrinsic Control of Contractility
• At any given EDV,
contraction depends
upon level of
sympathoadrenal
activity
– NE & Epi produce an
increase in HR &
contraction (positive
inotropic effect)
• Due to increased
Ca2+
in
sarcomeres
14-13

Blood Pressure (BP)
• Arterioles play role in blood distribution & control of BP
• Blood flow to capillaries & BP is controlled by aperture of
arterioles
• Capillary BP is decreased because they are downstream of
high resistance arterioles
14-52

Blood Pressure (BP)
• Capillary BP is also low because of large total
cross-sectional area
14-53

Baroreceptor Reflex
• Is activated by changes in BP
– Which is detected by baroreceptors (stretch
receptors) located in aortic arch & carotid sinuses
• Increase in BP causes walls of these regions to stretch,
increasing frequency of APs
• Baroreceptors send APs to vasomotor & cardiac control
centers in medulla
• Is most sensitive to decrease & sudden
changes in BP
14-55

Atrial Stretch Receptors
• Are activated by increased venous return & act
to reduce BP
• Stimulate reflex tachycardia (slow HR)
• Inhibit ADH release & promote secretion of
ANP
14-58

Chapter 13&14 lecture-1

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