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Blood, Blood Vessels
& Circulation
21-1
Physical Characteristics of Blood
• Thicker (more viscous) than water and flows more slowly than
water
• Temperature of 100.4 degrees F
• pH 7.4 (7.35-7.45)
• 8 % of total body weight
• Blood volume
– 5 to 6 liters in average male
– 4 to 5 liters in average female
– hormonal negative feedback systems maintain constant blood volume and
osmotic pressure
Blood components
• 55% = plasma: mainly water
– 7 to 8% dissolved substances (sugars, amino acids, lipids & vitamins), ions,
dissolved gases, hormones
– most of the proteins are plasma proteins: provide a role in balancing osmotic
pressure and water flow between the blood and extracellular fluid/tissues
– loss of plasma proteins from blood – decreases osmotic pressure in blood and
results in water flow out of blood into tissues  swelling
– most common plasma proteins: albumin, globulins, clotting proteins (fibrin)
Blood: Cellular elements
• 45% of blood is the cellular elements or formed elements
• 99% of this (44.55% of total blood) is erythrocytes or RBCs
– formed by differentiation of hematopoietic stem cells (HSCs) in the red bone
marrow of long bones and pelvis – makes about 2 million per second!
– made from an immature cell = reticulocyte
– as they mature in the marrow they lose most organelles and its nucleus
– lives only about 120 days – destroyed by the liver and spleen
– liver degrades the hemoglobin to its globin component and the heme is
degraded to a pigment called bilirubin - bile
– Iron(Fe+3)
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transported in blood attached to transferrin protein
stored in liver, muscle or spleen
attached to ferritin or hemosiderin protein
in bone marrow being used for hemoglobin synthesis
-1% found in the Buffy coat :
-leukocytes (WBCs) and platelets
(thromobocytes)
-neutrophils: phagocytic properties
-release agents which destroy/digest
bacteria
-eosinophils: parasitic defense cells
-also involved in the allergic response
-release histaminase to slows down
inflammation caused by basophils
-basophils: release heparin, histamine &
serotonin
-heighten the inflammatory response
and account for hypersensitivity (allergic)
reaction
-monocytes: enter various tissues and
differentiate into phagocytic
macrophages
Hematopoiesis
HSC
Anatomy of Blood Vessels
• Closed system of tubes that carries blood
• Arteries carry blood away from heart to
tissues
– elastic arteries
– muscular arteries
– arterioles
• Capillaries are thin enough to allow exchange
• Venules merge to form veins that bring blood
back to the heart
21-8
Cardiovascular System
Blood vessels: Types
A. Arteries
-carry oxygenated blood (most of the time)
away from the heart
-thicker than veins
-three layers: inner endothelium
middle smooth muscle
outer connective tissue
-arteriole = small artery
C. Capillaries
-site of gas exchange with tissues
-connect arterioles and venules
-network of microscopic vessels
(one cell thick) = capillary bed
-site of exchange: gases, nutrients,
wastes
-can be closed off when not needed
B. Veins
-carry deoxygenated blood (most of
the time) – toward the heart
-same three layers as arteries
(less SM and connective tissue)
-thinner and more expansive than
arteries
-contain valves - to help the flow
of blood back to heart
-small vein = venule
21-9
• Tunica interna (intima)
– innermost layer - simple squamous
epithelium known as endothelium
Arteries
• Tunica media
– major component - circular smooth
muscle fibers
– smooth muscle is innervated by
sympathetic nervous system
– contraction of this muscle causes
vasodilation
• increases diameter of vessel
– Relaxation of this muscle causes or
vasoconstriction
• decreases diameter of vessel
• Tunica externa
– elastic & collagen fibers
21-10
Veins
• Proportionally thinner walls than same
diameter artery
– tunica media less muscle
– lack external & internal
elastic lamina
• Still adaptable to variations
in volume & pressure
• Valves are thin folds of
tunica interna designed to prevent
backflow
• Venous sinus has no muscle at all
– coronary sinus that drains the heart muscle
or dural venous sinuses that drain the brain
21-11
Capillaries
• Microscopic vessels that connect
arterioles to venules
• Found near every cell in the body but
more extensive in highly active tissue
(muscles, liver, kidneys & brain)
• Function is exchange of nutrients,
gases & wastes between blood and
tissue fluid
• Structure is single layer of simple
squamous epithelium (endothelium)
and its basement membrane
21-12
The Lymphatic System
• Lymphocytes travel throughout the body
in spaces between the cells and are
carried in the blood and lymphatic
system.
• the lymphatic system = system of
lymphatic vessels + lymph nodes +
lymphatic tissues (spleen, thymus,
tonsils) that filter lymph and circulate
WBCs
• lymph = yellow-colored fluid that is
produced from your blood plasma at
capillary beds
–
–
produced when plasma filters out of
your blood and into your tissues
some of that filtrate drains from tissues
and becomes lymph
The Lymphatic System
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Lymph comes from your blood plasma but is returned
to you blood stream
along the way it flows through lymph nodes which
house lymphocytes and macrophages
these immune cells clean the lymph of bacteria
so what gets returned to your blood is cleaned
lymph is the way we “launder” our blood
http://www.niaid.nih.gov/topics/immuneSystem/Pages/structureImages.
aspx
Velocity of Blood Flow
• Speed of blood flow in cm/sec is inversely related to crosssectional area
– blood flow is slows in the arterioles
• slowest rate in capillaries allows for
exchange
• Blood flow becomes faster when
vessels merge to form veins
• Venous return depends on:
– 1. skeletal contraction
– 2. valves preventing backflow
21-15
Blood Pressure
• Pressure exerted by blood on walls of a
vessel
– caused by contraction of the ventricles
– highest in aorta
• 120 mm Hg during systole & 80
during diastole
• If heart rate increases, BP rises
• Pressure falls steadily in systemic circulation with distance from left ventricle
• Regulation of Blood Pressure:
– 1. role of cardiovascular center in the medulla
– 2. sensory receptors – proprioceptors (physical activity),
baroreceptors, chemoreceptors (oxygen, carbon dioxide)
– 3. hormones – epinephrine, anti-diuretic hormone
– 4. local factors – local physical and chemical factors
– 5. higher centers of the brain, limbic system, hypothalamus
21-16
Vascular Pathways
1. Systemic
21-17
Vascular Pathways
2. Pulmonary
21-18
Arterial Branches of Systemic Circulation
• All are branches from aorta
supplying arms, head, lower
limbs and all viscera with
O2 from the lungs
• Aorta arises from left
ventricle (thickest chamber)
– 4 major divisions of aorta
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ascending aorta
arch of aorta
thoracic aorta
abdominal aorta
21-19
Aorta and Its Superior Branches
• Aorta is largest artery of the body
– ascending aorta
• 2 coronary arteries supply myocardium
– arch of aorta -- branches to the arms & head
• brachiocephalic trunk branches into right common carotid and right subclavian
• left subclavian & left carotid arise independently
– descending aorta – divides into thoracic and abdominal
21-20
Left
Common
Carotid
Brachiocephalic
Trunk
Left
Subclavian
Superior
Vena
Cava
Aortic Arch
Ascending
Aorta
Pericardium
Diaphragm
21-21
Coronary Arteries
• Branches off ascending
aorta
• Left coronary artery
– anterior interventricular
art.
– left marginal
– circumflex branch
• in coronary sulcus, supplies
left atrium and left ventricle
• in the posterior IV sulcus
supplies both ventricles
• Right coronary artery
– right marginal branch
• in coronary sulcus, supplies
right ventricle
– posterior interventricular
art.
• in the sulcus – connects with
the circumflex 21-22
Coronary Veins
• Collects wastes from cardiac muscle
• Drains into a large sinus on posterior surface of heart
called the coronary sinus
• Coronary sinus empties into right atrium
21-23
Right Conus artery
Left coronary
artery
Left
Marginal
Artery & vein
Right coronary
artery
Anterior
Interventricular
Small cardiac
vein
Great
Cardiac
Vein
Right
Marginal
artery
Anterior
Interventricular
Green dots on veins
21-24
Great
Cardiac
Vein
Circumflex
artery
Posterior
Interventricular
Artery
(right & left)
Coronary
Sinus
Green dots on veins
21-25
Subclavian Branches
• Subclavian arteries pass
superior to the 1st rib
– gives rise to vertebral a. that
supplies part of the blood to the
Circle of Willis on the base of the
brain
• Become the axillary artery in
the armpit
• Become the brachial artery in
the arm
– deep radial artery
– radial and ulnar collaterals
• Divide into radial and ulnar
branches in the forearm
21-26
vertebral
Radial collateral
Ulnar
collateral
thyrocervical
brachial
suprascapular
Common
interosseous
thoracoacromial
axillary
Common
Carotid
subscapular
circumflex humeral
ulnar
deep brachal
radial
brachial
interosseous
radial collateral
ulnar collateral
Deep palmar arch
Superficial palmar arch
brachial
Digital arteries
ulnar
radial
Common Carotid Branches
Circle of Willis
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External carotid arteries
– supplies structures external to skull as branches of
maxillary and superficial temporal branches
– “Seven little fairies ascended over Polly’s super
mums”
Internal carotid arteries (contribute to Circle of
Willis)
– supply eyeballs and parts of brain
21-28
posterior
auricular
superficial temporal
maxillary
occipital
internal
carotid
external
carotid
carotid
sinus
facial
lingual
superior
thyroid
21-29
Abdominal Aorta and Its Branches
• Supplies abdominal & pelvic viscera & lower extremities
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celiac trunk supplies liver, stomach, spleen & pancreas
superior & inferior mesenteric arteries supply intestines
renal arteries supply kidneys
gonadal arteries supply ovaries
and testes
• Splits into common iliac
arteries at 4th lumbar vertebrae
– external iliacs supply
lower extremity
– internal iliacs supply
pelvic viscera
21-30
Inferior
Vena Cava
Celiac
Superior
Mesenteric
Renal
Gonadal
Inferior
mesenteric
Common
Iliac
21-31
Visceral Branches off Abdominal Aorta
• Celiac trunk is first branch inferior to diaphragm
– left gastric artery, splenic artery, common hepatic artery (gives rise to
right gastric)
• Superior mesenteric artery lies in mesentery of intestines
– supplies upper intestines (small and large)
– jejunal, ileals, ileocolic, right & middle colic arteries
• Inferior mesenteric artery
– supplies descending colon, sigmoid colon & rectum
– left colic, sigmoid and rectal branches
21-32
Left
Gastric
Hepatic
Proper
Common
Hepatic
Splenic
Splenic
Vein
Celiac
trunk
Left
Colic
Artery
Inferior
Mesenteric
Sigmoid
Superior
Rectal
Arteries of the Lower Extremity
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External iliac artery become femoral artery when it passes under the inguinal ligament &
into the thigh
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femoral artery gives off deep femoral branch
femoral artery becomes popliteal artery behind the knee
gives off anterior tibial and fibular/peroneal branches
continues on as posterior tibial artery (runs alongside the tibial nerve)
21-34
Common iliac
External iliac
Internal iliac
Deep femoral
Ascending branch
of Lateral femoral circumflex
Lateral femoral circumflex
Obturator
Deep femoral continues
Descending branch
of Lateral circumflex
Femoral
-lateral femoral circumflex wraps around head of femur – gives off ascending and descending branches – descending
branch runs down lateral side of thigh
-descending genicular runs down medial side of thigh
Common iliac
External iliac
Internal iliac
Deep femoral
Ascending branch
of Lateral femoral circumflex
Obturator
Lateral femoral circumflex
Femoral
Descending
Genicular
Deep femoral continues
Deep Femoral
Descending br
Of Lateral femoral circumflex
Genicular
Arteries of the
Knee
Anterior
Tibial
Femoral
Deep Femoral
Descending
Genicular
Descending br
Of Lateral femoral circumflex
Genicular
Arteries of the
Knee
Anterior
Tibial
21-37
Veins of the Systemic Circulation
• Drain blood from entire
body & return it to right
side of heart
• Deep veins parallel the
arteries in the region
• Superficial veins are found
just beneath the skin
• All venous blood drains
to either superior or
inferior vena cava or
coronary sinus
21-38
Major Systemic Veins
• All veins empty into the right atrium of the heart
– superior vena cava drains the head and upper extremities
– inferior vena cava drains the abdomen, pelvis & lower limbs
– coronary sinus is large vein draining the heart muscle back into
the heart
21-39
Veins of the Head and Neck
• External and Internal
jugular veins drain the
head and neck into the
superior vena cava
• Blood from the brain
drains into several large
dural sinuses - empty
into internal jugular
vein
– Transverse sinus
– Sigmoid sinus
– Sagittal sinus
21-40