Blood Vessels
Circulatory System
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Three basic components:
• Heart - serves as pump that establishes the
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pressure gradient needed for blood to flow to
tissues
Blood - transport medium within which materials
being transported are dissolved or suspended
Blood vessels - passageways through which
blood is distributed from heart to all parts of body
and back to heart
Types Of Blood Vessels
• Arteries – carry blood away from the heart
• Capillaries – smallest blood vessels
• The site of exchange of molecules between blood and tissue fluid
• Veins – carry blood toward the heart
arteries → arterioles → capillaries → venules → veins
Functions Of Blood Vessels
• Arteries - carry blood away from heart
• Arterioles - small arteries that deliver blood to
capillaries
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Capillaries – thin walled vessels allow for
exchange between blood and tissue cells
• Venules - collect and drain blood into veins
• Veins - return blood to heart
Structure Of Blood Vessels
• Composed of three layers (tunics)
• Tunica intima – composed of simple squamous epithelium
• Tunica media – sheets of smooth muscle
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Contraction – vasoconstriction
Relaxation – vasodilation
• Tunica externa – composed of connective tissue
• Lumen - central blood-filled space of a vessel
Structural Differences
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Arteries have thicker tunica media and narrower lumens
Veins have thicker tunica externa
Arteries have more elastic and collagen fibers
Veins have larger lumens and valves
Types Of Arteries
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Elastic arteries – the largest arteries
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Diameters range from 2.5 cm to 1 cm
Includes the aorta and its major branches
Sometimes called conducting arteries
High elastin content dampens surge of blood
pressure
Types Of Arteries
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Muscular (distributing) arteries
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Lie distal to elastic arteries
Diameters range from 1 cm to 0.3 mm
Includes most named arteries
Tunica media is thick
Unique features
• Internal and external elastic laminae
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Types Of Arteries
Arterioles
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Smallest arteries
Diameters range from 0.3 mm to 10 µm
Larger arterioles possess all three tunics
Diameter of arterioles controlled by:
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Local factors in the tissues
Sympathetic nervous system
Capillaries
• Smallest blood vessels
• Diameter from 8–10 µm
• Red blood cells pass through single file
• Endothelial cells – held together by tight junctions and desmosomes
• Routes into and out of capillaries
• Direct diffusion
• Through intercellular clefts - gaps of unjoined membrane where
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small molecules can enter and exit
Through fenestrations - pores
Capillaries
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Site-specific functions of capillaries
• Lungs – oxygen enters blood, carbon dioxide leaves
• Small intestines – receive digested nutrients
• Endocrine glands – pick up hormones
• Kidneys – removal of nitrogenous wastes
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Tendons and ligaments – poorly vascularized
Epithelia and cartilage – avascular, receive
nutrients from nearby CT
Capillaries
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Three types of capillary
• Continuous – most common
• Fenestrated – have pores
• Sinusoids
Sinusoids
• Wide, leaky capillaries found in some organs
• Usually fenestrated
• Have large diameters
• Intercellular clefts are wide open
• Occur in bone marrow, liver, spleen and lymphoid tissue
Capillary Beds
• An interconnected network of vessels running through tissues
• Consists of:
• Collateral arteries feeding an arteriole
• Metarterioles
• Arteriovenous anastomoses
• Capillaries
• Venules
Capillary Beds
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Precapillary sphincters - regulate the flow of blood to
tissues
Veins
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Conduct blood from capillaries
toward the heart
Blood pressure is much lower
than in arteries
Smallest veins – called venules
• Diameters from 8 – 100 µm
• Smallest venules – called
postcapillary venules
Venules join to form veins
Role Of Veins
• To return blood to the heart, veins have special adaptations
• Large-diameter lumens, which offer little resistance to flow
• Valves (resembling semilunar heart valves), which prevent backflow of
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blood
Skeletal muscle pump - muscles press against thin-walled veins
Pulmonary Circulation
• Consists of blood vessels that take the blood to and from the lungs for
the purpose of gas exchange
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Pulmonary Trunk: oxygen-poor blood leaves the right ventricle via the
pulmonary trunk; large artery that branches to left and right pulmonary
arteries
Pulmonary Arteries : take the blood to the lung where oxygen is picked up
and CO2 is left off
Pulmonary Veins: blood returns to the heart via four pulmonary veins that
go to the left atrium
Systemic Circulation
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Consists of blood vessels
that extend to and from
the heart delivers oxygen
and nutrients to body
tissues picks up CO2 and
waste products
The Aorta And Vena Cava
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Ascending aorta – arises from the left
ventricle branches to form coronary
arteries
Aortic arch – lies posterior to the
manubrium branches to form
• Brachiocephalic trunk
• Left common carotid
• Left subclavian arteries
Descending aorta – continues from the
aortic arch
• Thoracic aorta – in the region of
T5–T12
• Abdominal aorta – ends at L4
• Divides into right and left common
iliac arteries
• Superior/Inferior vena cava returns
blood from the systemic veins to the
heart
The Hepatic Portal System
• A specialized part of the vascular circuit
• Picks up digested nutrients
• Delivers nutrients to the liver for processing
Veins Of The Hepatic Portal System
Hepatic veins
Liver
Gastric veins
Spleen
Hepatic portal vein
Inferior vena cava
Splenic vein
Inferior
mesenteric vein
Superior
mesenteric vein
Small intestine
Large intestine
Rectum
Cerebral Arterial Circle (Circle Of Willis)
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“Circle” equalizes blood pressure in the brain and can provide alternative channels if
one vessel becomes blocked
The circle is formed from : posterior cerebral arteries, posterior communicating arteries,
internal carotid arteries, anterior cerebral arteries, and anterior communicating arteries
Anterior
Cerebral arterial circle
(circle of Willis)
• Anterior
communicating
artery
Middle
cerebral
artery
Internal
carotid
artery
• Anterior
cerebral artery
• Posterior
communicating
artery
• Posterior
cerebral artery
Basilar artery
Vertebral artery
(c)
Posterior
Arteries Of The Right Upper Limb And Thorax
Vertebral artery
Suprascapular artery
Axillary artery
Brachial artery
Common carotid
arteries
Right subclavian
artery
Left subclavian
artery
Left axillary
artery
Brachiocephalic
trunk
Anterior
intercostal
artery
Descending
aorta
Radial
artery
Ulnar
artery
(b)
Arteries Of The Head And Neck, Right Aspect
Internal
carotid artery
External
carotid artery
Common
carotid artery
Subclavian
artery
Axillary
artery
(a)
Brachiocephalic
trunk
Internal thoracic
artery
Major Branches Of The Abdominal Aorta
Diaphragm
Adrenal
gland
Suprarenal
artery
Celiac trunk
Renal artery
Superior
mesenteric artery
Kidney
Abdominal
aorta
Gonadal
artery
Inferior
mesenteric artery
Common iliac
artery
The Celiac Trunk And Its Main Branches
Liver
Inferior vena cava
Celiac trunk
Common hepatic
artery
Right gastric artery
Abdominal aorta
(b)
Left gastric
artery
Splenic artery
Spleen
Superior
mesenteric
artery
Arteries Of The Right Pelvis And Lower Limb
Common iliac artery
Internal iliac artery
External iliac artery
Popliteal artery
Anterior tibial
artery
Femoral artery
Popliteal artery
Anterior tibial artery
Posterior tibial artery
Fibular artery
(a) Anterior view
Posterior
tibial
artery
Fibular artery
(b) Posterior view
Flow Chart Summarizing Main Systemic Arteries
Figure 19.17
Systemic Veins
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Three major veins enter the right atrium
Superficial veins lie just beneath the skin
Multivein bundles – venous plexuses
Unusual patterns of venous drainage
• Dural sinuses
• Hepatic portal system
Venae Cavae and Tributaries
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Superior vena cava
• Returns blood from body regions superior to the
diaphragm
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Inferior vena cava
• Returns blood from body regions inferior to the
diaphragm
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Superior and inferior vena cava
• Join the right atrium
Major veins of the systemic circulation.
Dural sinuses
External jugular vein
Vertebral vein
Internal jugular vein
Superior vena cava
Axillary vein
Great cardiac vein
Hepatic veins
Hepatic portal vein
Superior mesenteric
vein
Inferior vena cava
Ulnar vein
Radial vein
Digital veins
Common iliac vein
External iliac vein
Femoral vein
Great saphenous vein
Popliteal vein
Posterior tibial vein
Anterior tibial vein
Fibular vein
Subclavian vein
Right and left
brachiocephalic veins
Cephalic vein
Brachial vein
Basilic vein
Splenic vein
Median cubital vein
Renal vein
Inferior mesenteric vein
Internal iliac vein
Dural Sinuses In The Cranium
Superior sagittal
sinus
Falx cerebri
Inferior sagittal
sinus
Straight sinus
Cavernous
sinus
Junction of
sinuses
Transverse
sinuses
Sigmoid sinus
Jugular foramen
Right internal
jugular vein
(b)
Veins of the head and Neck
Ophthalmic vein
Superficial
temporal vein
Facial vein
Occipital vein
Posterior
auricular vein
External
jugular vein
Vertebral vein
Internal
jugular vein
Superior and
middle thyroid
veins
Brachiocephalic
vein
Subclavian
vein
Superior
vena cava
(a)
Veins Of The Right Upper Limb And Thorax Wall
Internal jugular vein
External jugular vein
Brachiocephalic veins
Left subclavian vein
Superior vena cava
Azygos vein
Accessory
hemiazygos vein
Right subclavian vein
Axillary vein
Brachial vein
Cephalic vein
Basilic vein
Hemiazygos vein
Posterior intercostals
Inferior vena cava
Median
cubital vein
Cephalic
vein
Ascending
lumbar vein
Median vein of the forearm
Basilic vein
Ulnar vein
Radial vein
Deep palmar
venous arch
Superficial palmar
venous arch
Digital veins
(a)
Antecubital Fossa
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Form anastomese
frequently
Median cubital
vein is used to
obtain blood or
administer IV fluids
Figure 19.22
Veins Of The Right Upper Limb And Thorax Wall
Brachiocephalic
veins
Superior vena
cava
1
2
3
4
5
6
Intercostal
veins
7
8
9
Left superior
intercostal
vein
Azygos vein
Accessory
hemiazygos
vein
Hemiazygos
vein
Intercostal
veins
10
11
12
Inferior vena
cava
(b)
Ascending
lumbar vein
Renal vein
Veins of the Abdomen
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Lumbar veins
Gonadal (testicular or ovarian) veins
Renal veins
Suprarenal veins
Hepatic veins
Tributaries Of The Inferior Vena Cava
Hepatic veins
Inferior vena cava
Right
suprarenal vein
Inferior phrenic
vein
Left suprarenal
vein
Renal veins
Right
gonadal vein
Left ascending
lumbar vein
Lumbar veins
Left gonadal
vein
Common iliac
vein
External iliac
vein
Internal iliac
vein
Dissection of the posterior abdominal wall
Right
Diaphragm
Hepatic
veins
Inferior
vena cava
Renal veins
Abdominal
aorta
Common
iliac veins
Left
Veins of the Pelvis and Lower Limbs
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Deep veins
• Share the name of the accompanying artery
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Superficial veins
• Great saphenous vein empties into the femoral
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vein
Small saphenous vein empties into the popliteal
vein
Veins Of The Right Lower Limb And Pelvis
Common iliac vein
Internal iliac vein
External iliac vein
Inguinal ligament
Femoral vein
Great saphenous
vein (superficial)
Great saphenous vein
Popliteal vein
Popliteal vein
Anterior tibial vein
Fibular (peroneal) vein
Fibular (peroneal)
vein
Anterior tibial vein
Small saphenous vein
(superficial)
Posterior tibial vein
Dorsalis pedis vein
Dorsal venous arch
Metatarsal veins
Plantar veins
(a)
Plantar arch
Digital veins
(b)
Flowchart Summarizing The Main Veins
Veins of
R. upper
limb
R. External jugular R. vertebral
Intracranial
– superficial
– cervical spinal
dural sinuses
head and neck
cord and vertebrae
R. subclavian
– R. head, neck,
and upper limb
R. axillary
R. internal jugular
– dural sinuses of the brain
Same as R. brachiocephalic
R. brachiocephalic
– R. side of head and R. upper limb
L. brachiocephalic
– L. side of head and L. upper limb
Superior vena cava
– runs from union of brachiocephalic
veins behind manubrium to R. atrium
R. atrium of heart
Azygos system
– drains much of
thorax
Diaphragm
Inferior vena cava
– runs from junction of common iliac
veins at L5 to R. atrium of heart
R. suprarenal
(L. suprarenal drains into L. renal vein)
– adrenal glands
R. gonadal
(L. gonadal drains into L. renal vein)
– testis or ovary
R. common iliac
– pelvis and R. lower limb
(a)
Veins of
R. lower limb
L. and R. hepatic veins
– liver
L. and R. renal veins
– kidneys
Lumbar veins (several pairs)
– posterior abdominal wall
L. common iliac
– pelvis and L. lower limb
Veins of
L. lower limb