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Blood Chapter 16
Composition of Blood
• Body’s only fluid tissue
• It is composed of liquid plasma (54%) and
formed elements (Cells) (46%)
• Erythrocytes, or red blood cells (RBCs)- 45%
• Leukocytes, or white blood cells (WBCs) and Platelets (1%)
Physical Characteristics and Volume
• The pH of blood is 7.35–7.45
• Temperature is 38C, slightly higher than “normal” body
temperature
• 5–6 L for males, and 4–5 L for females
Color depends on its oxygen content.
– Bright red when oxygenated (e.g., arterial blood)
– Dark red when deoxygenated (e.g., venous blood).
Without O2
With O2
Functions of Blood
• Distribution
– Gases, nutrients, signaling molecules, wastes, heat
• Regulation
– Body fluid volume
– Body fluid pH
– Body T°
– Electrolyte levels
• Protection from pathogens and fluid loss
Body Temperature Regulation
Notice how the distribution of
blood varies with temperature.
Under warm conditions, blood
is shunted to the surface so that
heat can radiate away. Under
cold conditions, blood (and thus
heat) are conserved within the
core of the body.
Plasma
• 55% of blood
• Mostly water
• Dissolved Solutes Contains:
– Proteins
– Electrolytes
– Gases
– Nutrients
– Wastes
– Signaling molecules
– Buffers
Some of the Plasma Proteins
– Albumin
• 60% of plasma proteins.
• Produced by the liver.
• Primary function is to maintain the osmotic pressure of the plasma. Also
involved in transport of certain substances (steroids, bilirubin).
– Globulins
• Some globulins are produced in the liver and are transport proteins for
lipids, metal ions, and fat-soluble vitamins.
• Other globulins are produced by plasma cells (a type of leukocyte) during
the immune response. These globulins are also known as antibodies.
– Clotting proteins
• Most produced in the liver.
• Two important examples are prothrombin and fibrinogen.
Erythrocytes (RBCs)
•
•
•
•
•
•
•
Small
Biconcave disks
Anucleate
No organelles
Stuffed with hemoglobin
Transport O2
4-6 million per μL of blood
Figure 16.3
Hemoglobin
• Note the 4 heme groups associated with the 4 polypeptide
chains of the hemoglobin protein. Each has an iron in its
center.
How many O2 molecules could a single hemoglobin carry?
Hemopoiesis
• Blood cell formation = hemopoiesis
• All blood cell production occurs in
the red bone marrow, which is found
in the:
– Axial skeleton
– Pelvic and pectoral girdles
– Proximal epiphyses of the humerus
and femurs.
• What must happen as a hemocytoblast
differentiates into an RBC?
•
- What must be lost?
•
- What must be made?
•
- What must change?
RBC Production
RBC Lifespan
Born in the red
marrow
Circulate for
120d
Swallowed by a macrophage
(usually in the spleen)
Hemoglobin
Heme
Globin
Iron
Bilirubin
Carried by albumin to
the liver
Carried by transferrin
to the liver
Secreted into the small
intestine as part of bile
Stored in the liver as
hemosiderin or ferritin
Converted to stercobilin and
urobilin and excreted in feces
Amino acids
Back into the plasma
for reuse/recycling
Red Blood Cells
An important measurement involving RBCs is the hematocrit.
The hematocrit is the % of whole blood occupied by RBCs. It’s
reflective of the body’s O2 carrying capacity.
What’s the hematocrit in the sample below?
Homeostatic Imbalance
Anemias
• Anything that lowers oxygen carrying capacity
Too Few RBC
• Hemorrhagic, Hemolytic, Aplastic
Low Hemoglobin
• Iron-deficiency, athlete’s anemia
Homeostatic Imbalance
Genetic
Thalassemias
• Missing a globin chain
• RBC fragile and ruputre easy
Homeostatic Imbalance
Sickle-cell anemia
-Results from a defective gene coding for an abnormal
hemoglobin called hemoglobin S (HbS)
- HbS has a single amino acid substitution (287)
- This defect causes RBCs to become sickle-shaped in low-oxygen
situations
Leukocytes (WBCs)
• Only blood components that are complete cells:
– 4000 – 11,000 WBC’s /mm3
– Make up 1% of the total blood volume
– Can leave capillaries via diapedesis
– Move through tissue spaces
– Most are found in lymphatic organs and loose
connective tissues.
Here we see a WBC squeezing its way out of a blood vessel – in
other words, performing diapedesis.
Damaged Cell
WBC
WBC
Releases chemicals that
attract WBCs (known as
chemotactants).
WBC
WBC
WBCs converge on the area –
i.e., they exhibit positive
chemotaxis. They then
release more chemotactants
to attract more WBCs.
Classification of Leukocytes:
1.
Granulocytes- Contain
granules that are dyed by
Wright’s stain
-neutrophils, eosinophils,
and basophils
-all phagocytotic cells
2.
Agranulocytes -lack any
visible granules that take
up Wright’s Stain
-lymphocytes and
moncytes
Neutrophils
• Most numerous. 60% of circulating WBCs.
• A.k.a. polymorphonuclear leukocytes b/c of their multilobed nucleus.
• Function primarily in killing bacteria.
• Contain pale, lilac colored granules
Eosinophils
•
•
•
•
3% of circulating WBCs.
Function primarily in killing parasitic worms.
Also help reduce the severity of allergy attacks.
Contain reddish/orangish granules
Basophils
• Least numerous. <1% of circulating WBCs.
• Involved in inflammation.
• Contain purplish granules that contain:
– Histamine – a vasodilator
– Heparin – an anticoagulant
Lymphocytes
• 25% of circulating WBCs.
• No granules. Large purple nucleus
dominates most of the cell.
• 2 main types:
– T lymphocytes
• Control/coordinate immune response
• Kill virus-infected and cancerous cells
– B lymphocytes
• Secrete antibodies (immunoglobulins)
Monocytes
•
•
•
•
6% of circulating WBCs.
No granules.
Large pale cells w/ U or kidney-shaped nucleus.
Travel in the blood. Become macrophages w/in the
tissue spaces.
In this picture, find: RBCs, 2 neutrophils, an eosinophil, a basophil, a monocyte, a
lymphocyte, and a platelet.
What can you find here?
Homeostatic Imbalance
Leukemias
• Cancerous bone marrow cell that send immature
white blood cells into blood stream
• Immune response lessen
Platelets
• Cell fragments of
megakaryocytes (giant
cells created from mitosis
w/o cytokinesis)
• Contain chemicals vital to
coagulation.
• A.k.a. thrombocytes.
Hemostasis
•
Designed for healing the vasculature and providing a
framework for tissue repair
Three phases
1. Vascular spasms – immediate vasoconstriction in
response to injury
2. Platelet plug formation
3. Coagulation (blood clotting)
Clotting
Factors
Multiple substances are involved in the clotting
process.
– Most of these clotting factors are formed in the
liver.
•
•
Vitamin K is required for the synthesis of many of them.
Calcium is also required for coagulation.
Two ways to make prothrombin activator
1. Extrinsic Pathway – quick
2. Intrinsic Pathway – amplification, large quanities
Clot Retraction
• Healing of the blood vessel is taking place as clot
retraction occurs
• Platelets retract like muscle fibers
• Eventually the blood clot dissolves in fibrinolysis
– Plasmin digests fibrin
Mosquito saliva contains an enzyme called
apyrase. Which of the following is it most
likely to do?
a.
b.
c.
d.
Inhibit fibrinolysis
Promote thrombin production
Inhibit platelet aggregation
Promote fibrin production
•
•
•
•
Antiprostaglandin Aspirin
Low dose helps reduce risk of heart attack
Reduces platelet aggregation and plug formation
Reduces risks to embolism  Heart attack and
stroke
Blood Groups
• Humans have 30 varieties of naturally occurring RBC antigens
• The antigens of the ABO and Rh blood groups cause vigorous
transfusion reactions with agglutination (cell clumping) and
severe consequences when they are improperly transfused
• RBC membranes have glycoprotein antigens on their external
surface
• These antigens are:
– Unique to the individual
– Recognized as foreign if transfused into another individual
• Presence/absence of these antigens are used to classify blood
groups
AB0 blood grouping system
•
Blood group A
– A antigens on the surface of their red
blood cells and B antibodies in their
blood plasma.
•
Blood group B
– B antigens on the surface of their RBCs
and A antibodies
•
Blood group AB
– A and B antigens on the surface of their
RBCs and no A or B antibodies at all
•
Blood group 0 (null)
– No antigens on the surface of their RBCs
but both A and B antibodies
= red blood cell
ABO Blood Groups
Universal donor Universal receiver -
Table 16.4
Blood Typing
http://nobelprize.org/medicine/educational/landsteiner/readmore.html
• When serum containing anti-A or anti-B
antibodies is added to blood, agglutination (cell
clumping) will occur between the antibody and
the corresponding antigens
• Positive reactions indicate agglutination (cell
clumping)
Blood typ e
being tested
RBC
agglutinog ens
AB
B
A
O
A and B
B
A
none
Serum
Reaction
Anti-A
Anti -B
+
+
–
+
+
–
–
–
Rh factor blood grouping system
Rh+
• Have Rh factor on RBCs
• Do not make Rh antibodies
Rh• Do not have Rh factor on RBCs
• Do not make Rh antibodies unless
exposed to Rh factor!!!
What will occur???
http://nobelprize.org/medicine/educational/landsteiner/readmore.html
Women and Pregnacy
• Rh- women with Rh+ babies
• Pregnancy okay, but mother builds Rh antibodies
• If next pregnancy is Rh+ again mothers antibodies
will kill fetus RBCs
• RhoGAM blocks the Rh+ affect and does not
allow mother to make antibodies
Chapter 17
The Heart
Base of Heart
Apex of Heart
Figure 17.1
Heart Coverings
• Pericardium- membranes that cover the heart
• Fibrous Pericardium- outermost layer, Elastic fibrous tissue
» Anchors the heart in place staying attached to diaphragm and lungs
• Parietal Pericardium- directly attached to fibrous pericardium
• Visceral Pericardium- attaches directly to heart
Pericardial fluid fills the space between the parietal and visceral
Layers FUNCTION: lubrication, reduces friction
Homeostatic Imbalance
• Pericarditis  Inflammation of the
pericardium
Heart Wall Layers
• Epicardium – outermost layer
• (same as visceral pericardium)
• Myocardium – inner layer
• cardiac muscle layer forming the bulk of the heart
• Endocardium – endothelial layer that lines the
chambers of the heart
Chambers and Associated Great Vessels
BODY
Superior Portion of the body
Coronary veins
Superior and
Inferior
Vena Cavae
Right Atrium
Inferior
Portion
of the body
Tricuspid Valve
Pulmonary
Semilunar Valve
Right Ventricle
LUNGS
Aorta
Left Atrium
Mitral (bicuspid) valve
Aortic Semilunar Valve
Left Ventricle
Interventricular
Septum
Coronary Circulation- the heart’s own blood supply
• Heart works continuously thus requires a constant supply of oxygen and
nutrients
Aorta
Right
atrium
Coronary
Sinus
Coronary Arteries
Right Coronary Artery
Left Coronary Artery
Supplies: Right atrium,
Supplies: Left atrium, portions of both
Portions of both ventricles
Ventricles and the Interventricular septum
And portions of the hearts
Electrical conduction system
Coronary Veins
Branches of the right and left arteries merge at
junctions Called Anastomoses
This creates Collateral circulation-
Homeostatic Imbalance
Arthrosclerosis
• Plaque build up in coronary artery
• Videos
Homeostatic Imbalance
Heart Attack
• Often the result of blockage of a coronary artery
• Thus a portion of the heart is not being supplied
with oxygen
• Angina pectoralis- pain in the chest
• Myocardial Infarction- prolonged blockage with
death of cardiac muscle tissue
External Heart: Anterior View
Figure 17.4b
External Heart: Posterior View
Figure 17.4d
Gross Anatomy of Heart: Frontal
Section
Figure 17.4e
Heart Valves
• Heart valves insure unidirectional blood flow
through the heart
• Atrioventricular (AV) valves lie between the
atria and the ventricles
• AV valves prevent backflow into the atria when
ventricles contract
• Chordae tendineae anchor AV valves to
papillary muscles
Heart Valves – AV Valves
Figure 17.9
Heart Valves – Semilunar Valves
Figure 17.10
Semilunar Valves
prevent backflow of blood
into the ventricles
Microscopic Heart Muscle Anatomy
•
•
•
•
Intercalated discs anchor cardiac cells together and allow free
passage of ions
Heart muscle behaves as a functional syncytium (as a unit)
Does not need input from nervous system to contract
(automaticity)
The heart is made up of two types of muscle fibers:
1.
2.
Contractile cells – for contraction of muscle
Cells of the conducting system (autorhythmic cells) –control electrical
activity
Contractile Cells
Cardiac contractile muscle is similar
to skeletal muscle contraction needs
(1) Action potential
(2) Release of Calcium into cells
(3) Binding of calcium to troponins
Difference: Skeletal fibers have a
Short refractory period while cardiac
has a long refractory period.
WHY???
Figure 17.11b
Cells of the Conductive System
Autorhythmic cells
– Initiate action potentials
– Have unstable resting
potentials called pacemaker
potentials
– Use calcium influx (rather
than sodium) for rising
phase of the action potential
– Rate of depolarization varies
but Fastest rate of
depolarization is in sinoatrial
(SA) node known as
pacemaker
Electrical Events
1.
2.
3.
4.
5.
Sinoatrial (SA) node generates impulses about 75 times/minute
thus is the pacemaker
Electical impulse from SA node spreads across both atria causing
contraction
Atrioventricular (AV) node delays the impulse approximately 0.1
second.
AV bundle splits into two pathways in the interventricular septum
(bundle branches)
Impulse passes from atria to ventricles via the atrioventricular
bundle (bundle of His)
–
–
Bundle branches carry the impulse toward the apex of the heart
Purkinje fibers carry the impulse to the heart apex and ventricular
walls
Sequence of Electrical Events
VIDEO
Figure 17.14a
Regulation of Heart Rate
• Remember the heart does not need nervous
system stimulation to contract but the
autonomic nervous system can modify heart rate
– Parasympathetic- Conserve
– Sympathetic- Mobilize
– Vagus Nerve-
Electrocardiography
• What are electrical events of heart?
1. Atrial depolarization
2. Atrial repolarization
3. Ventricular depolarization
4. Ventricular repolarization
• P wave corresponds to depolarization
of SA node
• QRS complex corresponds to
ventricular depolarization
• T wave corresponds to ventricular
repolarization
• Atrial repolarization record is masked
by the larger QRS complex
Heart Sounds
• Heart sounds
(lub-dup) are
associated with
closing of heart
valves
Figure 17.19
Cardiac Cycle
• Cardiac cycle refers to all events associated
with blood flow through the heart
– Systole – contraction of heart muscle
– Diastole – relaxation of heart muscle
Phases of the Cardiac Cycle
• Ventricular filling – mid-to-late diastole
– Heart blood pressure is low as blood enters atria
and flows into ventricles
– AV valves are open, then atrial systole occurs
Phases of the Cardiac Cycle
• Ventricular systole
– Atria relax
– Rising ventricular pressure results in closing of AV
valves
Isovolumetric contraction phase
– Ventricular ejection phase opens semilunar valves
Phases of the Cardiac Cycle
• Isovolumetric relaxation – early diastole
– Ventricles relax
– Backflow of blood in aorta and pulmonary trunk
closes semilunar valves
• Dicrotic notch – brief rise in aortic pressure
caused by backflow of blood rebounding off
semilunar valves
Phases of the Cardiac Cycle
Figure 17.18a
Phases of the Cardiac Cycle
Figure 17.18b
Homeostatic Imbalance
•
•
•
•
•
Improper valve function
Changes the sound
Heart Murmurs
Mitral Valve Prolapse  two flaps loose
LISTEN TO SOUNDS
Cardiac Output (CO) and Reserve
• CO is the amount of blood pumped by each
ventricle in one minute
• CO = HR x SV
• HR is the number of heart beats per minute
• SV is the amount of blood pumped out by a
ventricle with each beat
• Cardiac reserve is the difference between
resting and maximal CO
Cardiac Output: Example
• CO (ml/min) = HR (75 beats/min) x SV (70
ml/beat)
• CO = 5250 ml/min (5.25 L/min)
Regulation of Stroke Volume
• SV = end diastolic volume (EDV) minus end
systolic volume (ESV)
• EDV = amount of blood collected in a ventricle
during diastole
• ESV = amount of blood remaining in a ventricle
after contraction
Factors Affecting Stroke Volume
1. Preload – amount ventricles are stretched by
contained blood, the greater the SV will be,
described as the Frank Starling Law
2. Contractility – cardiac cell contractile force due
to factors other than EDV such as SNS and PNS
3. Afterload – back pressure exerted by blood in
the large arteries leaving the heart, thus the
tension the ventricle must produce to push
blood out the semilunar valve
An increase in afterload, decreases SV
Frank-Starling Law of the Heart
• Preload, or degree of stretch, of cardiac muscle
cells before they contract is the critical factor
controlling stroke volume
• Slow heartbeat and exercise increase venous
return to the heart, increasing stroke volume
• Blood loss and extremely rapid heartbeat
decrease stroke volume
Preload and Afterload
Figure 17.20
CHAPTER 18
• Blood vessels
Blood Vessels
I. Overview of Blood Vessel
Structure and Function
II. Pressure Dynamics
including blood flow, blood
pressure and resistance
Cross section of an artery, vein and nerve
Generalized Structure of Blood Vessels
Figure 18.1b
Arterial Vessels: Greatest to smallest
•
•
•
•
Elastic or Conducting Vessels
Muscular Arteries
Arterioles
Capillaries
Elastic (Conducting) Arteries
• Thick-walled, large lumen arteries near the
heart; the aorta and its major branches
– Contain elastin in all three tunics
– Withstand and smooth out large blood pressure
fluctuations seen with systole and diastole
– Blood = flow fairly continuous
Muscular Arteries and Arterioles
• Distal to elastic arteries; deliver blood to organs
and muscles
– Have thick tunica media with more smooth muscle
and less elastic tissue
– Active in vasoconstriction
• Arterioles – smallest arteries; lead to capillary
beds
– Control flow into capillary beds via vasodilation and
constriction
Capillaries – smallest blood vessels
• Allow only a single RBC to pass at a time; usually
one cell layer thick on a basement membrane
Capillary
RBC
RBC
RBC
RBC
thin tunica interna
(Only 1 cell thick)
Easy Gas Exchange!
RBC
RBC
Major types of Capillary Beds
• Continuous
• Fenestrated
• Sinusoidal
Continuous Capillary Structure
•Most Common
•Abundant in the skin and muscles
•Tight junctions
•Intercellular clefts of unjoined
membranes that allow the passage of
water and small molecules
Blood-brain barrier
Continuous capillaries of the brain:
Tight junctions completely around the endothelium
Figure 18.3a
Fenestrated Capillary Structure
•Active capillary absorption or
filtrate formation occurs
•(e.g., small intestines, endocrine
glands, and kidneys)
•Pores (fenestrations) – usually
covered by thin membrane
•Greater permeability to solutes
and fluids than other capillaries
Figure 18.3b
Sinusoids
•Leaky with large lumens
•Found in the liver, bone marrow,
lymphoid tissue, and in some
endocrine organs
•Allow large proteins and blood
cells to move through
•Blood flows sluggishly, allowing
for modification in various ways
Protein
Blood Cell
Capillary Beds
• Have both an arterial and venous side
• Metarteriole joins arterial and venous sides
through the bed
• Precapillary sphincters made of smooth muscle
are present; separate the metarteriole from the
true capillaries
• Sphincters contracted-no flow through the bed
• Sphincters relaxed-blood flows through the bed
Capillary Beds
Figure 18.4a
Capillary Beds
Precapillary sphincter – cuff of smooth muscle
•Blood flow is regulated by vasomotor nerves and local chemical conditions, so it can
either bypass or flood the capillary bed
Figure 18.4b
Velocity of Blood flow
Figure 18.13
Venous Vessels: Smallest to greatest
Venules
•Smallest veins
•Lack a tunica media
Veins
•Composed of three tunics, with a thin tunica media and a thick
tunica externa consisting of collagen fibers and elastic networks
•Capacitance vessels (blood reservoirs) that contain 65% of the
blood supply
•Large-diameter lumens, which offer little resistance to flow
•Valves (resembling semilunar heart valves), which prevent backflow
of blood
•Vena cavae
•largest veins; where they enter the heart
Homeostatic Imbalance
Varicose Veins
• Vein valves become loose
• Obesity, hereditary, pregnancy put downward
pressure on veins
• Blood pools up stretches
• Anal veins, hemorroids
Terminology
Blood Flow
Actual volume of blood flowing through a vessel, an
organ, or the entire circulation in a given period
– Varies widely through individual organs, according to
immediate needs
Blood Pressure (BP)
• Force per unit area exerted on the wall of a
blood vessel by its contained blood
– Measured in mm Hg
– Measured in reference to systemic arterial BP in
large arteries near the heart
• *The differences in BP = provide the driving
force that keeps blood moving from higher to
lower pressure areas*
Relationship of diastolic and systolic BPs
• Systolic pressure – peak
pressure exerted on an
artery during ventricular
contraction; top number in
fraction eg. 120/80
• Diastolic pressure – lowest
level of arterial pressure
when the heart is relaxed;
bottom number infraction
eg. 120/80
Arterial Blood Pressure
• Pulse pressure – the difference between systolic
and diastolic pressure
• Mean arterial pressure (MAP) – pressure that
propels the blood to the tissues
Diastole lasts longer than systole=Mean Pressurenot just halfway between systolic and diastolic
• MAP = diastolic pressure + 1/3 pulse pressure
Venous Blood Pressure
•
Only about 20 mm Hg throughout the venous
system
• Two ways to get blood through the venous system
1. Pressure changes in ventral body cavity push blood
toward the heart
2. Skeletal Muscle Pump: the relaxation/contraction
of skeletal muscle squeezes blood up past one way
valves back toward the heart
Maintaining Blood Pressure
• Maintaining blood pressure requires:
– Cooperation of the heart, blood vessels, and kidneys
– Supervision of the brain
Blood Pressure Controls include short and long
term control mechanisms
Controls of Blood Pressure
• Short-term controls:
– Are mediated by the nervous system and
bloodborne chemicals
– Counteract moment-to-moment fluctuations in
blood pressure by altering peripheral resistance
• Long-term controls:
regulate blood volume
kidney is the big player here
Short-Term Mechanisms: Neural Controls
• Neural controls of peripheral resistance:
– Vasomotor center/Cardiac center in medulla of brain
stem
– Alter blood distribution to respond to specific
demands
– Maintain MAP by altering blood vessel diameter
Short-Term Mechanisms: Vasomotor
Activity
• Sympathetic activity causes:
– Vasoconstriction and a rise in blood pressure if increased;
“Fight or flight”
– Blood pressure to decline to routine levels if decreased
• Vasomotor activity is modified by:
– Baroreceptors (pressure-sensitive) found in aorta/carotids
– Chemoreceptors (O2, CO2, and H+ sensitive) locations as
above
– Higher brain centers
– Bloodborne chemicals and hormones
Chemicals that Increase Blood Pressure
• Adrenal medulla hormones – norepinephrine
and epinephrine increase blood pressure
• Antidiuretic hormone (ADH) – causes intense
vasoconstriction in cases of extremely low BP
• Angiotensin II – causes intense vasoconstriction
when renal profusion is inadequate
• Endothelium-derived factors – endothelin and
prostaglandin-derived growth factor (PDGF) are
both vasoconstrictors
WHY?(Hint:rememberChapter
16 Blood)
Chemicals that Decrease Blood Pressure
• Atrial natriuretic peptide (ANP) – causes blood
volume and pressure to decline
• Nitric oxide (NO) – has brief but potent
vasodilator effects
• Inflammatory chemicals – histamine, etc. are
potent vasodilators
• Alcohol – causes BP to drop by inhibiting ADH
Long-Term Mechanisms: Renal Regulation
• Baroreceptors adapt to chronic high or low
blood pressure
• Kidneys maintain long-term BP by regulating
blood volume
– Increased BP stimulates the kidneys to eliminate
water, thus reducing BP
– Decreased BP stimulates the kidneys to increase
blood volume and BP
Renin-angiotensin mechanism in the
kidneys
(Indirect renal mechanism)
BP
Renin
Angiotensin II
Aldosterone
ADH
vasoconstriction
Enhances renal reabsorption
More water reabsorption
In the kidneys
•
Autoregulation: Local Regulation of Blood Flow
Autoregulation
–
routine, automatic adjustment of blood flow to
each tissue in proportion to its requirements at
any given point in time How does this occur?
1. Myogenic Controls- Increased stretch causes a
reflex vasoconstriction
2. Metabolic Controls-Increased acidity,CO2, or lactic
acid will cause vasodilation
Long-Term Autoregulation
• Is evoked when short-term autoregulation cannot meet tissue
nutrient requirements
• May evolve over weeks or months to enrich local blood flow
• Angiogenesis takes place:
–
–
–
–
When the number of vessels to a region increases
When existing vessels enlarge
When a heart vessel becomes partly occluded
Routinely to people in high altitudes, where oxygen content
of the air is low
Capillary Blood Pressure
What could happen with high
Capillary pressure?
• Low BP is sufficient to force filtrate out into interstitial space
and distribute nutrients, gases, and hormones between
blood and tissues
Capillary Dynamics: Movement of
Fluid
• Arterial side of the capillary bed has higher blood
pressure than the venous side. This pressure is
higher than the oncotic pressure inside the
capillary. Fluid gets forced through vessel walls.
• Venous side of the capillary bed has lower blood
pressure than the arterial side. The oncotic
pressure is higher than the BP so fluid is pulled
back into the vessel. The fluid that doesn’t make
it back in gets picked up by the lymphatic system
and returned to the heart
Capillary Dynamics: Gas & Nutrient
Exchange
• O2, CO2, wastes and nutrients pass through
capillary walls by diffusion which is a passive
process in which molecules move from areas of
high to low concentration
• O2/Nutrients are in a higher concentration inside
the vessel so diffuse to tissue
• CO2/Wastes are in higher concentration in tissue
so diffuse into the vessel
Capillary Exchange of Respiratory Gases and Nutrients
Figure 18.14.2
Circulatory Shock
• Blood vessels are inadequately filled - blood
cannot circulate normally
• Results in inadequate blood flow to meet tissue needs
– Hypovolemic shock – results from large-scale blood
loss
– Vascular shock – poor circulation resulting from
extreme vasodilation
– Cardiogenic shock – the heart cannot sustain
adequate circulation
Homeostatic Imbalance (Alterations in Blood
Pressure)
• Hypotension – low BP in which systolic pressure
is below 100 mm Hg
• Hypertension – condition of sustained elevated
arterial pressure of 140/90 or higher
– Transient elevations - normal
– Fever, physical exertion, and emotional upset
– Chronic elevation - heart failure, vascular disease, renal
failure, and stroke
– In general, a normal blood pressure reading for
healthy adults is below 120 systolic and 80 diastolic,
or 120/80.
Hypotension
• Orthostatic hypotension – temporary low BP
and dizziness when suddenly rising from a
sitting or reclining position
• Chronic hypotension – hint of poor nutrition
and warning sign for Addison’s disease (inadequate
adrenal cortex function)
• Acute hypotension – important sign of
circulatory shock
– Threat to patients undergoing surgery and those in
intensive care units
Hypertension
• Hypertension – sustained BP of 140/90 or
higher:
– Is the major cause of heart failure, vascular disease, renal
failure, and stroke
– Weakens the heart and ravages the blood vessels
– Causes tears in vessel endothelium that accelerate
atherosclerosis
• Elevated diastolic pressure is more significant
than systolic
– It indicates progressive occlusion and/or hardening of the
arterial tree
Hypertension
• Primary or essential hypertension – risk factors
in primary hypertension include diet, obesity,
age, race, heredity, stress, and smoking; no
identifiable cause is found
• Secondary hypertension – due to identifiable
disorders, including excessive renin secretion,
arteriosclerosis, and endocrine disorders