Anatomy of Blood Vessels
• Arteries carry blood away from heart
• Veins carry blood back to heart
• Capillaries connect smallest arteries to veins
20-1
Vessel Wall
• Tunica interna (intima)
– smooth inner layer that repels blood cells and platelets
– simple squamous endothelium overlying a basement
membrane and layer of fibrous tissue
• Tunica media
– middle layer
– usually thickest; smooth muscle, collagen, some elastic
– smooth muscle for vasomotion
• Tunica externa (tunica adventitia)
– outermost layer
– loose connective tissue with vasa vasorum
20-2
20-3
Arteries
• Conducting (elastic) arteries - largest
– pulmonary, aorta and common carotid
– tunica media consists of perforated sheets of elastic
tissue, alternating with thin layers of smooth muscle,
collagen and elastic fibers
– expand during systole, recoil during diastole; lessens
fluctuations in BP
• Distributing (muscular) arteries
– distributes blood to specific organs; femoral and
splenic
– smooth muscle layers constitute 3/4 of wall thickness
20-4
20-5
Arteries and Metarterioles
• Resistance (small) arteries
– arterioles control amount of blood to various
organs
• Metarterioles
– short vessels connect arterioles to capillaries
– muscle cells form a precapillary sphincter about
entrance to capillary
20-6
20-7
Arterial Sense Organs
• Major arteries above heart
• Carotid sinuses
– in walls of internal carotid artery
– monitors BP – signaling brainstem
• HR  and vessels dilate
• Carotid bodies
– oval bodies near carotids
– monitor blood chemistry
• adjust respiratory rate to stabilize pH, CO2, and O2
• Aortic bodies
– in walls of aorta
– same function as carotid bodies
20-8
Capillaries
• Thoroughfare channel - metarteriole
continues through capillary bed to venule
• Precapillary sphincters control which beds are
well perfused
– only 1/4 of the capillaries are open at a given time
20-9
Control of Capillary Bed Perfusion
20-10
Control of Capillary Bed Perfusion
20-11
Capillaries
• The walls of capillaries are thin and leaky to
varying degrees
Types of Capillaries
• Continuous - occur in most tissues
– endothelial cells have tight junctions with intercellular
clefts (allow passage of solutes)
• Fenestrated - kidneys, small intestine
– organs that require rapid absorption or filtration
– filtration pores – spanned by very thin glycoprotein layer allows passage of only small molecules
• Sinusoids - liver, bone marrow, spleen
– irregular blood-filled spaces; some have extra large
fenestrations, allow proteins and blood cells to enter
20-13
Fenestrated Capillary
20-15
Which capillary
is fenestrated?
Sinusoid in Liver
20-17
Veins
• Veins
–
–
–
–
lower blood pressure: 10mmHg with little fluctuation
thinner walls, less muscular and elastic tissue
expand easily, have high capacitance
valves aid skeletal muscles in upward blood flow
• Venules
– postcapillary venules more porous than capillaries
– muscular venules have tunica media
• Venous sinuses
– veins with thin walls, large lumens, no smooth muscle
20-18
Veins of Hepatic Portal
System
20-19
Superficial and Deep Veins of Upper Limb
20-20
Arterial
Pressure
Points
• Some major
arteries close to
surface -- allows
palpation for
pulse and serve as
pressure points to
reduce arterial
bleeding
20-21
Arteries of the Upper Limb
• Subclavian passes
between clavicle
and 1st rib
• Vessel changes
names as passes
to different
regions
20-22
– subclavian to
axillary to
brachial to radial
and ulnar
– brachial used for
BP and ABG
– radial artery for
pulse and ABG
Major Systemic Arteries
• Supplies oxygen and nutrients to all organs
20-24
Major Branches of Aorta
• Ascending aorta
– right and left coronary arteries supply heart
• Aortic arch
– brachiocephalic
• right common carotid supplying right side of head
• right subclavian supplying right shoulder and upper limb
– left common carotid supplying left side of head
– left subclavian supplying shoulder and upper limb
• Descending aorta
– thoracic aorta above diaphragm
– abdominal aorta below diaphragm
20-25
Major Branches of the Aorta
20-26
Arteries of the Head and Neck
• Common carotid to internal and external carotids
– external carotid supplies most external head structures
20-27
Arterial
Supply
of
Brain
Paired vertebral aa. combine to form basilar artery on pons
•
• Circle of Willis on base of brain formed from anastomosis of basilar and
internal carotid aa
• Supplies brain, internal ear and orbital structures
– anterior, middle and posterior cerebral
– superior, anterior and posterior cerebellar
20-28
Arteries of the Thorax
• Thoracic aorta supplies viscera and body wall
– bronchial, esophageal and mediastinal branches
– posterior intercostal and phrenic arteries
• Internal thoracic, anterior intercostal and
pericardiophrenic arise from subclavian artery
20-29
Major Branches of Abdominal Aorta
20-30
Celiac Trunk Branches
• Branches of celiac trunk supply upper abdominal viscera - stomach, spleen, liver and pancreas
20-31
Mesenteric Arteries
20-32
Arteries of the Lower Limb
• Branches to the lower limb arise from external iliac
20-33
branch of the common iliac artery
Major Systemic Veins
• Deep veins run parallel to arteries while superficial veins
have many anastomoses
20-34
Deep Veins of Head and Neck
• Large, thin-walled dural sinuses form in between layers of
dura mater (drain brain to internal jugular vein)
20-35
Superficial Veins of Head and Neck
• Branches of internal and external jugular veins drain the
external structures of the head
• 20-36
Upper limb is drained by subclavian vein
Inferior Vena Cava and Branches
• Notice absence of veins draining the viscera --- stomach,
20-37
spleen, pancreas and intestines
Veins of Hepatic Portal System
• Drains blood from viscera (stomach, spleen and
intestines) to liver so that nutrients are absorbed
20-38
Superficial and Deep Veins of Lower Limb
20-39