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The Circulatory System and Blood
Copyright © 2010 Pearson Education, Inc. Figure 19.2
Large veins(capacitancevessels)
Largelymphaticvessels
Arteriovenousanastomosis
Lymphaticcapillary
Postcapillaryvenule
Sinusoid
Metarteriole
Terminal arteriole
Arterioles(resistance vessels)
Muscular arteries(distributingvessels)
Elastic arteries(conductingvessels)
Small veins(capacitancevessels)
Lymphnode
Capillaries(exchange vessels)
Precapillary sphincterThoroughfarechannel
Lymphaticsystem
Venous system Arterial systemHeart
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Blood Flow Through Body Tissues
• Blood flow (tissue perfusion) is involved in
• Delivery of O2 and nutrients to, and removal of
wastes from, tissue cells
• Gas exchange (lungs)
• Absorption of nutrients (digestive tract)
• Urine formation (kidneys)
• Rate of flow is precisely the right amount to
provide for proper function
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Blood Pressure
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Velocity of Blood Flow
• Changes as it travels through the systemic
circulation
• Is inversely related to the total cross-sectional
area
• Is fastest in the aorta, slowest in the
capillaries, increases again in veins
• Slow capillary flow allows adequate time for
exchange between blood and tissues
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Monitoring Circulatory Efficiency
• Vital signs: pulse and blood pressure, along
with respiratory rate and body temperature
• Pulse: pressure wave caused by the
expansion and recoil of arteries
• Pulse is routinely taken at wrist. Please learn
other sites (surface anatomy) where pulse is
taken.
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Maintaining Blood Pressure
• Requires
• Cooperation of the heart, blood vessels, and
kidneys
• Supervision by the brain
Copyright © 2010 Pearson Education, Inc. Figure 19.12
Common carotid
artery
Brachial artery
Radial artery
Femoral artery
Popliteal artery
Posterior tibial
artery
Dorsalis pedis
artery
Superficial temporal
artery
Facial artery
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Variations in Blood Pressure
• Blood pressure cycles over a 24-hour period
• BP peaks in the morning due to levels of
hormones
• Age, sex, weight, race, mood, and posture
may vary BP
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Alterations in Blood Pressure
• Hypotension: low blood pressure
• Systolic pressure below 100 mm Hg
• Often associated with long life and lack of
cardiovascular illness
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Homeostatic Imbalance: 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 or
hypothyroidism
• Acute hypotension: important sign of
circulatory shock
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Alterations in Blood Pressure
• Hypertension: high blood pressure
• Sustained elevated arterial pressure of 140/90
or higher
• May be transient adaptations during fever,
physical exertion, and emotional upset
• Often persistent in obese people
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Homeostatic Imbalance: Hypertension
• Prolonged hypertension is a major cause of
heart failure, vascular disease, renal failure,
and stroke
• Primary or essential hypertension
• 90% of hypertensive conditions
• Due to several risk factors including heredity,
diet, obesity, age, stress, diabetes mellitus,
and smoking
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Homeostatic Imbalance: Hypertension
• Secondary hypertension is less common
• Due to identifiable disorders, including kidney
disease, arteriosclerosis, and endocrine
disorders such as hyperthyroidism and
Cushing’s syndrome
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The Major Blood Vessels
Copyright © 2010 Pearson Education, Inc. Figure 19.21b
Internal carotid artery
Common carotid arteries
Subclavian artery
Subclavian artery
Aortic archAscending aortaCoronary arteryThoracic aorta (abovediaphragm)
Renal artery
Superficial palmar arch
Radial artery
Ulnar artery
Internal iliac artery
Deep palmar arch
Vertebral artery
Brachiocephalic trunk
Axillary artery
Brachial artery
Abdominal aorta
Superior mesenteric artery
Gonadal artery
Common iliac arteryExternal iliac artery
Digital arteries
Femoral arteryPopliteal arteryAnterior tibial arteryPosterior tibial artery
Arcuate artery(b) Illustration, anterior
view
Inferior mesenteric artery
Celiac trunk
External carotid artery
Arteries of the head and trunk
Arteries that supply the upper limb
Arteries that supply the lower limb
Copyright © 2010 Pearson Education, Inc. Figure 19.22b
• Superficial
temporal artery***
• Maxillary artery
• Occipital artery
• Facial artery***
• Lingual artery
• Superior thyroid
artery
Ophthalmic artery
Larynx
Thyroid gland
(overlying trachea)
Clavicle (cut)
Brachiocephalic
trunk
Internal thoracic
artery
Basilar artery
Vertebral artery
Internal
carotid artery
Subclavian
artery
Axillary
artery
(b) Arteries of the head and neck, right aspect
External
carotid artery
Common
carotid artery
Thyrocervical
trunk
Costocervical
trunk
Branches of
the external
carotid artery
***routes for infection
Copyright © 2010 Pearson Education, Inc. Figure 19.22d
Frontal lobe
Optic chiasma
Middle
cerebral
artery
Internalcarotid arteryMammillarybody
Temporal
lobe
Occipital lobe
Cerebral arterialcircle (circle of Willis)
• Posteriorcerebral artery
Basilar artery
Vertebral artery
Cerebellum
• Posteriorcommunicating artery
(d) Major arteries serving the brain (inferior view, right side
of cerebellum and part of right temporal lobe removed)
Pons
• Anteriorcerebral artery
• Anteriorcommunicating artery
Posterior
Anterior
Copyright © 2010 Pearson Education, Inc. Figure 19.23b
Vertebral artery
Costocervical trunk
Thoracoacromial artery
Axillary artery
Subscapular artery
Radial artery
Ulnar artery
Brachial artery
Suprascapular artery
Thyrocervical trunk
Posterior circumflex
humeral artery
Anterior circumflex
humeral artery
Deep artery of arm
Common
interosseous
artery
Deep palmar archSuperficial palmar archDigital arteries
Common carotid
arteries
Right subclavian artery
Left subclavian artery
Brachiocephalic trunk
Posterior intercostal
arteries
Anterior intercostal
arteryInternal thoracic artery
Lateral thoracic artery
Descending aorta
(b) Illustration, anterior view
Copyright © 2010 Pearson Education, Inc. Figure 19.24b
Liver (cut) Diaphragm
Esophagus
Left gastric
artery
Superior
mesenteric
mesenteric
Left
gastroepiploic
artery
Spleen
Stomach
Pancreas
(major portion lies
posterior to stomach)
Splenic artery
Inferior vena cava
Celiac trunk
Hepatic artery
proper
Common hepatic
artery
Gastroduodenal
artery
Right gastric artery
Gallbladder
Abdominal aorta
Right
gastroepiploic
artery
Duodenum
(b) The celiac trunk and its major branches. The left half of the liver has been removed.
Duodenal ulcers and the hepatopancreaticoduodenal artery
Copyright © 2010 Pearson Education, Inc. Figure 19.24c
(c) Major branches of the abdominal aorta.
Hiatus (opening)
for inferior
vena cava
Diaphragm
Inferior
phrenic artery
Middle
suprarenal
artery
Renal artery
Superior
mesenteric
artery
Median sacral
arteryCommon
iliac artery
Ureter
Gonadal
(testicular or
ovarian) artery
Hiatus (opening)
for esophagus
Celiac trunk
Adrenal
(suprarenal)
gland
Kidney
Abdominal aorta
Lumbar arteriesInferior
mesenteric
artery
Copyright © 2010 Pearson Education, Inc. Figure 19.24d
(d) Distribution of the superior and inferior mesenteric arteries.
The transverse colon has been pulled superiorly.
Celiac trunk Transverse colon
Inferior mesenteric
artery
Aorta
Descending colon
Sigmoid colon
Rectum
Superior
mesenteric artery
Ascending colon
Ileum
Right common iliac
artery
Appendix
Cecum
Branches ofthe inferior mesenteric artery
• Left colic artery• Sigmoidal arteries• Superior rectal
artery
Branches ofthe superiormesenteric artery
• Middle colic artery• Intestinal arteries• Right colic artery• Ileocolic artery
Copyright © 2010 Pearson Education, Inc. Figure 19.25b
Common iliac artery
Deep artery of thigh
Obturator artery
Femoral artery
Adductor hiatus
Popliteal artery
Anterior tibial artery
Posterior tibial artery
Fibular artery
Dorsalis pedis artery
Arcuate artery
Dorsal metatarsal
arteries
(b) Anterior view
Internal iliac artery
Superior gluteal artery
External iliac artery
Lateral circumflex
femoral artery
Medial circumflex
femoral artery
Copyright © 2010 Pearson Education, Inc. Figure 19.25c
(c) Posterior view
Popliteal artery
Anterior tibial artery
Fibular artery
Dorsalis pedis artery
(from top of foot)
Plantar arch
Medial plantar
artery
Lateral plantar
artery
Posterior tibial
artery
Copyright © 2010 Pearson Education, Inc. Figure 19.26b
Renal vein
Splenic vein
Basilic vein
Brachial vein
Cephalic vein
Dural venous sinuses
External jugular vein
Vertebral vein
Internal jugular vein
Superior vena cava
Right and left
brachiocephalic veins
Axillary vein
Great cardiac vein
Hepatic veins
Hepatic portal vein
Superior mesenteric
veinInferior vena cava
Ulnar vein
Radial vein
Common iliac vein
External iliac vein
Internal iliac vein
Digital veins
Femoral vein
Great saphenous vein
Popliteal vein
Posterior tibial vein
Anterior tibial vein
Small saphenous vein
Dorsal venous arch
(b) Illustration, anterior
view. The vessels of the
pulmonary circulation
are not shown. Dorsal metatarsal veins
Inferior mesenteric vein
Median cubital vein
Subclavian vein
Veins of the head and trunk Veins that drain
the upper limb
Veins that drain
the lower limb
Copyright © 2010 Pearson Education, Inc. Figure 19.27c
(c) Dural venous sinuses of the brain
Confluence
of sinuses
Superior sagittal
sinus
Falx cerebri
Inferior sagittal
sinus
Straight sinus
Cavernous
sinus
Transverse
sinuses
Sigmoid sinus
Jugular foramen
Right internal
jugular vein
Cavernous sinus,
cranial nerves, and
migraines
Copyright © 2010 Pearson Education, Inc. Figure 19.29c
(c) The hepatic portal circulation.
Hepatic veins
Liver
Spleen
Gastric veins
Inferior vena cava
Inferior vena cava
(not part of hepatic
portal system)
Splenic vein
Right gastroepiploic
vein
Inferior
mesenteric vein
Superior
mesenteric vein
Large intestine
Hepatic portal
vein
Small intestine
Rectum
Copyright © 2010 Pearson Education, Inc. Figure 19.30b
Popliteal vein
Common iliac vein
Fibular vein
Anterior tibial vein
Dorsalis pedis vein
Dorsal venous arch
Dorsal metatarsal
veins(b) Anterior view
Internal iliac veinExternal iliac veinInguinal ligament
Femoral veinGreat saphenous
vein (superficial)
Small saphenous
veinCoronary bypass
surgery and other
grafts
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The Heart
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Cardiac Muscle Tissue
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The Path of Blood Flow
Copyright © 2010 Pearson Education, Inc. Figure 19.19a
R. pulmon-
ary veins
Pulmonary
trunk
Pulmonary capillaries
of the R. lung
Pulmonary capillaries
of the L. lungR. pulmonary
artery
L. pulmonary
artery
To
systemic
circulation
L. pulmonary
veins
(a) Schematic flowchart.
From
systemic
circulationRA
RV LV
LA
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The Heart Beat: Electrical Conduction
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The Fetal Heart
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Developmental Aspects
• Fetal shunts (foramen ovale and ductus
arteriosus) bypass nonfunctional lungs
• Ductus venosus bypasses the liver
• Umbilical vein and arteries circulate blood to
and from the placenta
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between atrium
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Structure of Blood Vessel Walls
• Arteries and veins
• Tunica intima, tunica media, and tunica
externa
• Lumen
• Central blood-containing space
• Capillaries
• Endothelium with sparse basal lamina
Copyright © 2010 Pearson Education, Inc. Figure 19.1b
Tunica media(smooth muscle andelastic fibers)
Tunica externa
(collagen fibers)
Lumen
Artery
LumenVein
Internal elastic lamina
External elastic lamina
Valve
(b)
Endothelial cellsBasement membrane
Capillary
network
Capillary
Tunica intima
• Endothelium• Subendothelial layer
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Tunics
• Tunica intima
• Endothelium lines the lumen of all vessels
• In vessels larger than 1 mm, a subendothelial
connective tissue basement membrane is
present
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Tunics
• Tunica media
• Smooth muscle and sheets of elastin
• Sympathetic vasomotor nerve fibers control
vasoconstriction and vasodilation of vessels
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Tunics
• Tunica externa (tunica adventitia)
• Collagen fibers protect and reinforce
• Larger vessels contain vasa vasorum to
nourish the external layer
Copyright © 2010 Pearson Education, Inc. Table 19.1 (1 of 2)
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Elastic (Conducting) Arteries
• Large thick-walled arteries with elastin in all
three tunics
• Aorta and its major branches
• Large lumen offers low-resistance
• Act as pressure reservoirs—expand and recoil
as blood is ejected from the heart
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Muscular (Distributing) Arteries and
Arterioles
• Distal to elastic arteries; deliver blood to body
organs
• Have thick tunica media with more smooth
muscle
• Active in vasoconstriction
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Arterioles
• Smallest arteries
• Lead to capillary beds
• Control flow into capillary beds via
vasodilation and vasoconstriction
Copyright © 2010 Pearson Education, Inc. Figure 19.1a
Artery
Vein
(a)
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Venules
• Formed when capillary beds unite
• Very porous; allow fluids and WBCs into
tissues
• Postcapillary venules consist of endothelium
and a few pericytes
• Larger venules have one or two layers of
smooth muscle cells
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Veins
• Formed when venules converge
• Have thinner walls, larger lumens compared with corresponding arteries
• Blood pressure is lower than in arteries
• Thin tunica media and a thick tunica externa consisting of collagen fibers and elastic networks
• Called capacitance vessels (blood reservoirs); contain up to 65% of the blood supply
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Capillaries
• Microscopic blood vessels
• Walls of thin tunica intima, one cell thick
• Pericytes help stabilize their walls and control
permeability
• Size allows only a single RBC to pass at a
time
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Capillaries
• In all tissues except for cartilage, epithelia,
cornea and lens of eye
• Functions: exchange of gases, nutrients,
wastes, hormones, etc.
Copyright © 2010 Pearson Education, Inc. Figure 19.16 (1 of 2)
Red blood
cell in lumen
Endothelial cell
Intercellular cleft
Fenestration
(pore)Endothelial cell nucleus
Tight junction
Basement membrane
Pinocytotic vesicles
Copyright © 2010 Pearson Education, Inc. Figure 19.16 (2 of 2)
Basementmembrane
Endothelialfenestration(pore)
Intercellularcleft
Pinocytoticvesicles
Caveolae
4 Transportvia vesicles orcaveolae (largesubstances)
3 Movementthroughfenestrations (water-soluble substances)
2 Movementthrough intercellular clefts (water-soluble substances)
1 Diffusionthrough membrane (lipid-soluble substances)
Lumen
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Sinusoidal Capillaries
• Fewer tight junctions, larger intercellular
clefts, large lumens
• Usually fenestrated
• Allow large molecules and blood cells to pass
between the blood and surrounding tissues
• Found in the liver, bone marrow, spleen
Copyright © 2010 Pearson Education, Inc. Figure 19.3c
Nucleus of
endothelial
cell
Red blood
cell in lumen
Endothelial
cell
Tight junction
Incomplete
basement
membrane
Large
intercellular
cleft
(c) Sinusoidal capillary. Most permeable. Occurs in
special locations (e.g., liver, bone marrow, spleen).
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Capillary Beds
• Interwoven networks of capillaries form the
microcirculation between arterioles and
venules
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Blood Flow Through Capillary Beds
• Precapillary sphincters regulate blood flow
into true capillaries
• Regulated by local chemical conditions and
vasomotor nerves (sympathetic division of
ANS).
Copyright © 2010 Pearson Education, Inc. Figure 19.4
(a) Sphincters open—blood flows through true capillaries.
(b) Sphincters closed—blood flows through metarteriole
thoroughfare channel and bypasses true capillaries.
Precapillary
sphincters Metarteriole
Vascular shunt
Terminal arteriole Postcapillary venule
Terminal arteriole Postcapillary venule
Thoroughfare channel
True capillaries
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Blood Composition
• Blood: a fluid connective tissue composed of
• Plasma
• Formed elements
• Erythrocytes (red blood cells, or RBCs)
• Leukocytes (white blood cells, or WBCs)
• Platelets
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Blood Composition
• Hematocrit
• Percent of blood volume that is RBCs
• 47% ± 5% for males
• 42% ± 5% for females
Copyright © 2010 Pearson Education, Inc. Figure 17.1
1 Withdraw
blood and place
in tube.
2 Centrifuge the
blood sample.
Plasma• 55% of whole blood• Least dense componentBuffy coat• Leukocytes and platelets• <1% of whole bloodErythrocytes
• 45% of whole blood• Most densecomponent
Formed
elements
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Physical Characteristics and Volume
• Sticky, opaque fluid
• Color scarlet to dark red
• pH 7.35–7.45
• 38C (100.4F)
• ~8% of body weight
• Average volume: 5–6 L for males, and 4–5
L for females
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Functions of Blood
1. Distribution of
• O2 and nutrients to body cells
• Metabolic wastes to the lungs and kidneys
for elimination
• Hormones from endocrine organs to target
organs
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Functions of Blood
2. Regulation of
• Body temperature by absorbing and
distributing heat
• Normal pH using buffers
• Adequate fluid volume in the circulatory
system
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Functions of Blood
3. Protection against
• Blood loss
• Plasma proteins and platelets initiate clot formation
• Infection
• Antibodies
• Complement proteins
• WBCs defend against foreign invaders
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Blood Plasma
• 90% water
• Proteins are mostly produced by the liver
• 60% albumin
• 36% globulins
• 4% fibrinogen
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Blood Plasma
• Nitrogenous by-products of metabolism—
lactic acid, urea, creatinine
• Nutrients—glucose, carbohydrates, amino
acids
• Electrolytes—Na+, K+, Ca2+, Cl–, HCO3–
• Respiratory gases—O2 and CO2
• Hormones
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Formed Elements
• Only WBCs are complete cells
• RBCs have no nuclei or organelles
• Platelets are cell fragments
• Most formed elements survive in the
bloodstream for only a few days
• Most blood cells originate in bone marrow
• Most blood cells do not divide
Copyright © 2010 Pearson Education, Inc. Figure 17.9
Formed
elements
Platelets
Leukocytes
Erythrocytes
Differential
WBC count
(All total 4800 –
10,800/l)
Neutrophils (50 – 70%)
Lymphocytes (25 – 45%)
Eosinophils (2 – 4%)
Basophils (0.5 – 1%)
Monocytes (3 – 8%)
Agranulocytes
Granulocytes
Copyright © 2010 Pearson Education, Inc. Table 17.2 (1 of 2)
Copyright © 2010 Pearson Education, Inc. Table 17.2 (2 of 2)
Copyright © 2010 Pearson Education, Inc. Figure 17.2
Platelets
Neutrophils Lymphocyte
Erythrocytes Monocyte
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Erythrocytes
• Biconcave discs, anucleate, essentially no
organelles
• Filled with hemoglobin (Hb) for gas transport
• Provide flexibility to change shape as
necessary
• Are the major factor contributing to blood
viscosity
Copyright © 2010 Pearson Education, Inc. Figure 17.3
2.5 µm
7.5 µm
Side view (cut)
Top view
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Erythrocytes
• Structural characteristics contribute to gas transport
• Biconcave shape—huge surface area relative to volume
• >97% hemoglobin (not counting water)
• No mitochondria; ATP production is anaerobic; no O2 is used in generation of ATP
• A superb example of complementarities of structure and function!
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Erythrocyte Function
• RBCs are dedicated to respiratory gas
transport
• Hemoglobin binds reversibly with O2
• Hemoglobin structure
• Protein globin + Heme pigment
• Iron atom in each heme can bind to one O2 molecule
• Each Hb molecule can transport four O2
• oxygen
Copyright © 2010 Pearson Education, Inc. Figure 17.4
Heme
group
(a) Hemoglobin consists of globin (two
alpha and two beta polypeptide
chains) and four heme groups.
(b) Iron-containing heme pigment.
a Globin chains
b Globin chains
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Hemoglobin (Hb)
• O2 loading in the lungs
• Produces oxyhemoglobin (ruby red)
• O2 unloading in the tissues
• Produces deoxyhemoglobin or reduced
hemoglobin (dark red)
• CO2 loading in the tissues
• Produces carbaminohemoglobin (carries 20%
of CO2 in the blood)
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Hematopoiesis
• Hematopoiesis (hemopoiesis): blood cell
formation
• Occurs in red bone marrow of axial skeleton,
girdles and proximal epiphyses of humerus
and femur
• Hemocytoblasts (hematopoietic stem cells)
• Give rise to all formed elements
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Erythropoiesis
Erythropoiesis: red blood cell production
• Ejection of the nucleus and formation of
reticulocytes
• Reticulocytes then become mature
erythrocytes
Copyright © 2010 Pearson Education, Inc. Figure 17.5
Stem cell
HemocytoblastProerythro-
blast
Early
erythroblast
Late
erythroblast Normoblast
Phase 1
Ribosome
synthesis
Phase 2
Hemoglobin
accumulation
Phase 3
Ejection of
nucleus
Reticulo-
cyte
Erythro-
cyte
Committed
cell
Developmental pathway
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Regulation of Erythropoiesis
• Too few RBCs leads to tissue hypoxia
• Too many RBCs increases blood viscosity
• Balance between RBC production and
destruction depends on
• Hormonal controls
• Adequate supplies of iron, amino acids, and B
vitamins
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Hormonal Control of Erythropoiesis
• Erythropoietin (EPO)
• Direct stimulus for erythropoiesis
• Released by the kidneys in response to
hypoxia
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Hormonal Control of Erythropoiesis
• Causes of hypoxia
• Hemorrhage or increased RBC destruction
reduces RBC numbers
• Insufficient hemoglobin (e.g., iron deficiency)
• Reduced availability of O2 (e.g., high altitudes)
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Dietary Requirements for Erythropoiesis
• Nutrients—amino acids, lipids, and carbohydrates
• Iron
• Stored in Hb (65%), the liver, spleen, and bone
marrow
• Stored in cells as ferritin and hemosiderin
• Transported loosely bound to the protein transferrin
• Vitamin B12 and folic acid—necessary for DNA
synthesis for cell division
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Fate and Destruction of Erythrocytes
• Life span: 100–120 days
• Old RBCs become fragile, and Hb begins to
degenerate
• Macrophages engulf dying RBCs in the
spleen
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Fate and Destruction of Erythrocytes
• Heme and globin are separated
• Iron is salvaged for reuse
• Heme is degraded to yellow the pigment bilirubin
• Liver secretes bilirubin (in bile) into the intestines
• Degraded pigment leaves the body in feces as stercobilin
• Globin is metabolized into amino acids
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Erythrocyte Disorders
• Anemia: blood has abnormally low O2-
carrying capacity
• A sign rather than a disease itself
• Blood O2 levels cannot support normal
metabolism
• Accompanied by fatigue, paleness, shortness
of breath, and chills
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Causes of Anemia
1. Insufficient erythrocytes
• Hemorrhagic anemia: acute or chronic loss
of blood
• Hemolytic anemia: RBCs rupture
prematurely
• Aplastic anemia: destruction or inhibition of
red bone marrow
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Causes of Anemia
2. Low hemoglobin content
• Iron-deficiency anemia
• Secondary result of hemorrhagic anemia or
• Inadequate intake of iron-containing foods
or
• Impaired iron absorption
3. Abnormal hemoglobin
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Causes of Anemia
4. Pernicious anemia
• Deficiency of vitamin B12
• Lack of intrinsic factor needed for absorption
of B12
• Treated by intramuscular injection of B12 or
application of Nascobal
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Causes of Anemia
5. Sickle-cell anemia
• Defective gene codes for abnormal
hemoglobin (HbS)
• Causes RBCs to become sickle shaped in
low-oxygen situations
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Erythrocyte Disorders
• Polycythemia: excess of RBCs that increase
blood viscosity
• Results from:
• Polycythemia vera—bone marrow cancer
• Secondary polycythemia—when less O2 is
available (high altitude)
• Blood doping
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Leukocytes
• Make up <1% of total blood volume
• Can leave capillaries via diapedesis
• Move through tissue spaces by ameboid
motion and positive chemotaxis
• Leukocytosis: WBC count over 11,000/mm3
• Normal response to bacterial or viral invasion
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Lymphocytes
• Large, circular nuclei with a thin rim of blue
cytoplasm
• Mostly in lymphoid tissue; few circulate in the
blood
• Crucial to immunity
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Lymphocytes
• Two types
• T cells act against virus-infected cells and
tumor cells
• B cells give rise to plasma cells, which
produce antibodies
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Monocytes
• The largest leukocytes
• Abundant cytoplasm
• U- or kidney-shaped nuclei
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Monocytes
• Leave circulation, enter tissues, and
differentiate into macrophages
• Actively phagocytic cells; crucial against
viruses, intracellular bacterial parasites, and
chronic infections
• Activate lymphocytes to mount an immune
response
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Leukopoiesis
• Production of WBCs
• Stimulated by chemical messengers from
bone marrow and mature WBCs
• All leukocytes originate from hemocytoblasts
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Leukocyte Disorders
• Leukopenia
• Abnormally low WBC count—drug induced
• Leukemias
• Cancerous conditions involving WBCs
• Named according to the abnormal WBC clone involved
• Myelocytic leukemia involves myeloblasts
• Lymphocytic leukemia involves lymphocytes
• Acute leukemia involves blast-type cells and primarily affects children
• Chronic leukemia is more prevalent in older people
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Leukemia
• Bone marrow totally occupied with cancerous
leukocytes
• Immature nonfunctional WBCs in the
bloodstream
• Death caused by internal hemorrhage and
overwhelming infections
• Treatments include irradiation, antileukemic
drugs, and stem cell transplants
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Platelets
• Small fragments of megakaryocytes
• Formation is regulated by thrombopoietin
• Blue-staining outer region, purple granules
• Granules contain serotonin, Ca2+, enzymes,
ADP, and platelet-derived growth factor
(PDGF)
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Platelets
• Form a temporary platelet plug that helps seal breaks in blood vessels
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Hemostasis
• Fast series of reactions for stoppage of
bleeding
1. Vascular spasm
2. Platelet plug formation
3. Coagulation (blood clotting)
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What causes vascular spasm?
• Vasoconstriction of damaged blood vessel
• Triggers
• Direct injury
• Chemicals released by endothelial cells and
platelets
• Pain reflexes
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Platelet Plug Formation
At site of blood vessel injury, platelets stick to
exposed collagen fibers, then swell, become
spiked and sticky, and release chemical
messengers causing more platelets
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Coagulation
• A set of reactions in which blood is
transformed from a liquid to a gel
• Reinforces the platelet plug with fibrin
threads
Copyright © 2010 Pearson Education, Inc. Figure 17.13
Collagen
fibers
Platelets
Fibrin
Step Vascular spasm
• Smooth muscle contracts,
causing vasoconstriction.
Step Platelet plug
formation• Injury to lining of vessel
exposes collagen fibers;
platelets adhere.
• Platelets release chemicals
that make nearby platelets
sticky; platelet plug forms.
Step Coagulation
• Fibrin forms a mesh that traps
red blood cells and platelets,
forming the clot.
1
2
3
Copyright © 2010 Pearson Education, Inc. Figure 17.15
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Clot Retraction
• Actin and myosin in platelets contract within
30–60 minutes
• Platelets pull on the fibrin strands, squeezing
serum from the clot
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Clot Repair
• Platelet-derived growth factor (PDGF)
stimulates division of smooth muscle cells and
fibroblasts to rebuild blood vessel wall
• Vascular endothelial growth factor (VEGF)
stimulates endothelial cells to multiply and
restore the endothelial lining
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Disorders of Hemostasis
Thromboembolytic disorders: undesirable clot formation
• Thrombus: clot that develops and persists in an unbroken blood vessel
• May block circulation, leading to tissue death
• Embolus: a thrombus freely floating in the blood stream
• Pulmonary emboli impair the ability of the body to obtain oxygen
• Cerebral emboli can cause strokes
• Prevented by
• Aspirin
• Antiprostaglandin that inhibits thromboxane A2
• Heparin
• Anticoagulant used clinically for pre- and postoperative cardiac care
• Warfarin
• Used for those prone to atrial fibrillation
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Disorders of HemostasisBleeding disorders: abnormalities that prevent normal clot
formation
Thrombocytopenia: deficient number of circulating platelets
• Widespread hemorrhage, for example, due to suppression or destruction of bone marrow (e.g., malignancy, radiation)
• Treated with transfusion of concentrated platelets
Impaired liver function
• Inability to synthesize procoagulants
• Causes include vitamin K deficiency, hepatitis, and cirrhosis
• Liver disease can also prevent the liver from producing bile, impairing fat and vitamin K absorption
Hemophilias include several similar hereditary bleeding disorders
• Symptoms include prolonged bleeding, especially into joint cavities
• Treated with plasma transfusions and injection of missing factors
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Human Blood Groups
• RBC membranes bear 30 types glycoprotein antigens that are
• Perceived as foreign if transfused blood is mismatched
• Unique to each individual
Presence or absence of each antigen is used to classify blood cells into different groups
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ABO Blood Groups
• Types A, B, AB, and O
• Based on the presence or absence of two agglutinogens (A and B) on the surface of the RBCs
• Blood may contain anti-A or anti-B antibodies (agglutinins) that act against transfused RBCs
• Anti-A or anti-B form in the blood at about 2 months of age
Copyright © 2010 Pearson Education, Inc. Table 17.4
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Rh Blood Groups
• There are 45 different Rh agglutinogens (Rh factors)
• C, D, and E are most common
• Rh+ indicates presence of D
• Anti-Rh antibodies form if an Rh– individual receives
Rh+ blood
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Hemolytic Disease of the Newborn
• Also called erythroblastosis fetalis
• Anti-Rh antibodies cross the placenta and destroy the RBCs of an Rh+ baby
• The baby can be treated with prebirthtransfusions and exchange transfusions after birth
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Transfusions
• Whole-blood transfusions are used when
blood loss is substantial
• Packed red cells (plasma removed) are used
to restore oxygen-carrying capacity
• Transfusion of incompatible blood can be fatal
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Transfusion Reactions
• Occur if mismatched blood is infused
• Donor’s cells
• Are attacked by the recipient’s plasma agglutinins
• Agglutinate and clog small vessels
• Rupture and release free hemoglobin into the bloodstream
• Result in
• Diminished oxygen-carrying capacity
• Hemoglobin in kidney tubules and renal failure
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Restoring Blood Volume
• Death from shock may result from low blood volume
• Volume must be replaced immediately with
• Normal saline or multiple-electrolyte solution that
mimics plasma electrolyte composition
• Plasma expanders (e.g., purified human serum
albumin, hetastarch, and dextran)
• Mimic osmotic properties of albumin
• More expensive and may cause significant
complications
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Diagnostic Blood Tests
• Hematocrit
• Blood glucose tests
• Microscopic examination reveals variations in size and shape of RBCs, indications of anemias
• Differential WBC count
• Prothrombin time and platelet counts assess hemostasis
• SMAC, a blood chemistry profile
• Complete blood count (CBC)
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Autoregulation
• Automatic adjustment of blood flow to each tissue in
proportion to its requirements at any given point in
time
• Is controlled intrinsically by modifying the diameter of
local arterioles feeding the capillaries
• Two types of autoregulation
1.Metabolic
2.Myogenic
Copyright © 2010 Pearson Education, Inc. Figure 19.15
Metabolic
controls
pH Sympathetic
a Receptors
b ReceptorsEpinephrine,
norepinephrine
Angiotensin II
Antidiuretic
hormone (ADH)
Atrial
natriuretic
peptide (ANP)
Dilates
Constricts
Prostaglandins
Adenosine
Nitric oxide
Endothelins
Stretch
O2
CO2
K+
Amounts of:
Amounts of:
Nerves
Hormones
Myogenic
controls
Intrinsic mechanisms(autoregulation)
• Distribute blood flow to individual
organs and tissues as needed
Extrinsic mechanisms
• Maintain mean arterial pressure (MAP)
• Redistribute blood during exercise and
thermoregulation
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Long-Term Autoregulation
• Angiogenesis
• Occurs when short-term autoregulation cannot
meet tissue nutrient requirements
• The number of vessels to a region increases
and existing vessels enlarge
• Common in the heart when a coronary vessel
is occluded, or throughout the body in people
in high-altitude areas
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Fluid Movements: Bulk Flow
• Extremely important in determining relative
fluid volumes in the blood and interstitial
space
• Direction and amount of fluid flow depends on
two opposing forces: hydrostatic and colloid
osmotic pressures
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Circulatory Shock
• Any condition in which
• Blood vessels are inadequately filled
• Blood cannot circulate normally
• Results in inadequate blood flow to meet
tissue needs
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Circulatory Shock
• Hypovolemic shock: results from large-scale
blood loss
• Vascular shock: results from extreme
vasodilation and decreased peripheral
resistance
• Cardiogenic shock results when an inefficient
heart cannot sustain adequate circulation
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Maintaining Blood Pressure
• The main factors influencing blood pressure:
• Cardiac output (CO)
• Peripheral resistance (PR)
• Blood volume
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Cardiac Output (CO)
• Determined by venous return and neural and
hormonal controls
• Resting heart rate is maintained by the
cardioinhibitory center via the
parasympathetic vagus nerves
• Stroke volume is controlled by venous return
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Cardiac Output (CO)
• During stress, the cardioacceleratory center
increases heart rate and stroke volume via
sympathetic stimulation
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Control of Blood Pressure
• Short-term neural and hormonal controls
• Counteract fluctuations in blood pressure by
altering peripheral resistance
• Long-term renal regulation
• Counteracts fluctuations in blood pressure by
altering blood volume
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Short-Term Mechanisms: Neural Controls
• Neural controls of peripheral resistance
• altering blood vessel diameter
• Alter blood distribution
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Short-Term Mechanisms: Neural Controls
• Neural controls operate via reflex arcs that
involve
• Baroreceptors
• Vasomotor centers and vasomotor fibers
• Vascular smooth muscle
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Short-Term Mechanisms: Baroreceptor-
Initiated Reflexes
• Baroreceptors are located in
• Carotid sinuses
• Aortic arch
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Short-Term Mechanisms: Baroreceptor-
Initiated Reflexes
• Increased blood pressure stimulates baroreceptors to
• causing arteriole dilation and venodilation
• Stimulates the cardioinhibitory center
• Baroreceptors in the carotid sinus reflex protect the blood
supply to the brain
• Baroreceptors in the aortic reflex help maintain adequate
blood pressure in the systemic circuit
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Short-Term Mechanisms:
Chemoreceptor-Initiated Reflexes
• Chemoreceptors are located in the
• Carotid sinus
• Aortic arch
• Large arteries of the neck
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Short-Term Mechanisms:
Chemoreceptor-Initiated Reflexes
• Chemoreceptors respond to rise in CO2, drop
in pH or O2
• Increase blood pressure
• Are more important in the regulation of
respiratory rate (Chapter 22)
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Influence of Higher Brain Centers
• Reflexes that regulate BP are integrated in the
medulla
• Higher brain centers in the cortex and
hypothalamus can modify BP via relays to the
medulla
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Short-Term Mechanisms: Hormonal
Controls
• Adrenal medulla hormones norepinephrine
(NE) and epinephrine cause generalized
vasoconstriction and increase cardiac output
• Angiotensin II, generated by kidney release of
renin, causes vasoconstriction
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Short-Term Mechanisms: Hormonal
Controls
• Atrial natriuretic peptide causes blood volume
and blood pressure to decline, causes
generalized vasodilation
• Antidiuretic hormone (ADH)(vasopressin)
causes intense vasoconstriction in cases of
extremely low BP
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Long-Term Mechanisms: Renal Regulation
• Baroreceptors quickly adapt to chronic high
or low BP
• Long-term mechanisms step in to control
BP by altering blood volume
• Kidneys act directly and indirectly to
regulate arterial blood pressure
1. Direct renal mechanism
2. Indirect renal (renin-angiotensin) mechanism
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Direct Renal Mechanism
• Alters blood volume independently of
hormones
• Increased BP or blood volume causes the
kidneys to eliminate more urine, thus reducing
BP
• Decreased BP or blood volume causes the
kidneys to conserve water, and BP rises
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Leukocytes
• Make up <1% of total blood volume
• Can leave capillaries via diapedesis
• Move through tissue spaces by ameboid
motion and positive chemotaxis
• Leukocytosis: WBC count over 11,000/mm3
• Normal response to bacterial or viral invasion
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Lymphocytes
• Large, dark-purple, circular nuclei with a thin
rim of blue cytoplasm
• Mostly in lymphoid tissue; few circulate in the
blood
• Crucial to immunity
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Lymphocytes
• Two types
• T cells act against virus-infected cells and
tumor cells
• B cells give rise to plasma cells, which
produce antibodies
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Monocytes
• The largest leukocytes
• Abundant pale-blue cytoplasm
• Dark purple-staining, U- or kidney-shaped
nuclei
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Monocytes
• Leave circulation, enter tissues, and
differentiate into macrophages
• Actively phagocytic cells; crucial against
viruses, intracellular bacterial parasites, and
chronic infections
• Activate lymphocytes to mount an immune
response
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