BLOOD VESSEL ANATOMY
Blood vessel
1. Length – about 60,000 miles of blood vessels
2. Arteries – from heart to body; branch and diverge
3. Veins – from body to heart; merge and converge
Blood vessel wall
1. Tunica intima – (interna) innermost; endothelial; simple
squamous
2. Tunica media – circular smooth muscle and elastin;
thicker in arteries
3. Tunica adventitia – (externa) loosely woven collagen; thicker in veins
-a. vasa vasorum – blood vessel supply larger vessels
Arteries
1. Elastic (conducting) – aorta and major branches; large
lumen; recoil and expand
2. Muscular (distributing) – more smooth muscle; to organs;
more vasoconstriction
3. Arterioles – lead to capillary beds; smooth muscle;
supply of bypass capillary bed
Capillaries
1. Thin walled – tunica intima only
2. Size – 1 mm long; 8 – 10 micrometers in diameter
3. Supply – good except in tendons, ligaments, cartilage,
epithelium, cornea, lens
Capillary types
1. Continuous – tight junction; intercellular clefts; most
common; skin, muscle,
2. Fenestrated – small pores in endothelials; absorption;
kidneys, intestine
3. Sinusoidal – very leaky; clefts and fenestrations; cells
pass; liver, marrow
Capillary bed
1. Capillary bed – interwoven network of capillaries
2. Metarteriole – arteriole to capillary bed and
thoroughfare channel
3. Precapillary sphincter – cuff of smooth muscle; open or
close capillary bed
4. Thoroughfare channel – shunts blood from metarteriole to
post capillary venule
Venous system
1. Venules – 8 – 100 micrometers; postcapillary very leaky
2. Capacitance vessels – large lumens; contains 65% of
blood; partially filled
3. Venous valves – like semilunar; allow one way movement of
blood
4. Varicose veins – incompetent valves; torturous and
dilated
Vascular anastomoses
1. Arterial anastomoses – more than one artery supply organ;
merge
2. Arteriovenous anastomoses – metarteriole thoroughfare
shunt
3. Venous anastomoses – connect more freely than arteries
BLOOD VESSEL PHYSIOLOGY
Blood flow, blood pressure, and resistance
1. Blood flow – volume flowing; organ, vessel, body; ml/min
2. Blood pressure – force per unit area exerted on wall; mm
of Hg (Mercury)
3. Resistance – opposition to flow; measure of friction
encountered
-a. Blood viscosity – thicker flows slower
-b. Vessel length – longer the greater the resistance
-c. Vessel diameter – most important; other two change
little
-d. F r4 –
flow is directly proportional to radius to the fourth power
4. F=ΔP/R – flow
is directly proportional to pressure changes; indirect to resistance
Systemic blood pressure
1. Pressure gradient – pressure always greatest next to pump
2. Aorta – highest pressure in body
3. Right atrium – lowest blood pressure in body
4. Arterioles – where the steepest changes in blood pressure
occur
Arterial blood pressure
1. Systolic – ventricular contraction; about 120 mm
2. Diastolic – semilunar valve closed; about 80 mm
3. Pulse pressure – difference between the two; about 40 mm
4. Mean arterial pressure – propels blood throughout cardiac
cycle; diastole longer
-a. MAP = diastolic pressure + pulse pressure / 3
Capillary blood pressure
1. Lowered pressure – 40 mm to 20 mm into and out of
capillary bed
2. Fragile – capillaries would rupture too much pressure
3. Fluid exchange – are porous; even low pressure force
fluid out
Venous blood pressure
1. Constancy – about 20 mm; average of 60 mm arterial system
2. Respiratory pump – changes in abdominal and thoracic
pressure
3. Muscular pump – skeletal muscle contract; more important
Neural control of blood pressure (short term)
1. Vasomotor center – ANS; medulla; with cardiac center;
cardiovascular center
2. Baroreceptor – elastic arteries of thorax and neck;
respond to stretch or lack of
4. Chemoreceptor – low oxygen, pH, or increased CO2 ;
increase blood pressure
5. Higher brain centers – cerebral cortex and hypothalamus
Chemical control of blood pressure (short term)
1. Hormones – most of the substances involved
-a. Adrenal medulla hormones – epinephrine and
norepinephrine; vasoconstriction
-b. Atrial natriuretic peptide (ANP) – kidney releases more
Na and water 
-c. Antidiuretic hormone (ADH) – kidney conserves more
water; vol increases
2. Histamine – inflammation; allergy; potent vasodilator
3. Endothelial cells – from the blood vessels release
vasodilators and vasoconstrictor
Renal control of blood pressure (long term)
1. Direct effect – just doing their job
-a. High blood volume – high blood pressure; more water and
solutes lost
-b. Low blood volume – low blood pressure; more water and
solutes conserved
2. Indirect effect – rennin angiotensin mechanism;
vasoconstriction; ↑vol pres
-a. Renin – enzyme released by kidneys; steps lead to
angiotensin II
-b. Angiotensin II – vasoconstrictor; adrenal cortex to
release aldosterone
-c. Aldosterone – kidney conserve Na and water; ADH from
pituitary
-d. Antidiuretic hormone – less water released
Taking a pulse
1. Pulse – expansion and recoil of elastic arteries;
pressure wave
2. Radial pulse – radial artery surfaces near wrist
3. Arterial pulse points – common carotid, brachial, femoral
Monitoring blood pressure
1. Blood pressure cuff – cuts of blood flow to brachial
artery
2. Sounds of Korotkoff – soft tapping sounds; become louder
3. Systolic pressure – the pressure at which the sounds
start
4. Diastolic pressure – the pressure at which the sounds
stop
Blood pressure alterations
1. Orthostatic hypotension – in elderly; when rising; old
SNS; legs not brains
2. Hypertension – systolic > 140 mm; heart works harder;
blood vessel damage
3. Primary (essential) hypertension – no known cause;
factors identified
4. Secondary hypertension – known cause; hyperthyroidism or
excess renin
Velocity of blood flow
1. Velocity – is measured in cm/s
2. Cross sectional area – is inversely proportional to blood
velocity
-a. Aorta – cross section of 2.5 square cm; 45 cm/s
-b. Capillaries – total cross section 4500 squared cm;
velocity 0.03 cm/s
-c. Vena cavae – cross section 8 squared cm; velocity 10 to
30 cm/s
Autoregulation: local regulation of blood flow
1. Autoregulation – automatic adjustments; need; independent
systemic controls
2. Metabolic control – low nutrients or oxygen;
vasodilation; more blood in tissue
3. Myogenic control – increase stretch vasodilation;
increase it, vasoconstriction
4. Long term autoregulation – increase number and/or size of
blood vessels
Blood flow in special areas
1. Skeletal muscle – 25% of capillaries open at rest;
increase 10 fold during exercise
2. Brain – constancy; 750 ml/ minute
3. Skin – thermoregulation; varies from 50 to 2500 ml/minute
4. Lungs – reverse autoregulation; ↓ oxygen,
vasoconstriction, ↓oxygen, vasodilation
5. Heart – coronary arteries dilated during diastole;
exercise, dilation increases
6. Intestine – increased blood flow at rest; decreased
during exercise
Capillary exchange of nutrients and gases
1. Diffusion – most important mechanism; move along a
concentration gradient
-a. Water soluble – amino acids, sugars; through clefts and
fenestrations
-b. Lipid soluble – such as respiratory gases; through lipid
bilayer
2. Larger molecules – like proteins, through cytoplasmic
vesicles (bulk transport)
Fluid movements in capillary beds
1. Hydrostatic pressure – fluid pressure against wall
-a. Capillary (BHP) – 35 mm arterial side; 16 mm venous side
-b. Interstitial fluid (IFHP) – let stand at 0 mm
2. Osmotic pressure – large molecules (albumin); draws fluid
in
-a. Capillary (BCOP) – albumin; 26 mm
-b. Interstitial fluid (IFOP) – few proteins; 1 mm
3. Net Filtration Pressure – NFP = (BHP − IFOP) − (BCOP ─IFHP)
4. Arterial end - (35 ─ 0) ─ (26 ─ 1) = 10
mm out of capillary
5. Venous end – (17 ─ 0) ─ (26 ─ 1) = − 9 mm into capillary
6. Lymphatic system
– returns fluid and proteins back to the blood
Circulatory Shock
1. Circulatory shock – vessels inadequately filled;
insufficient circulation
2. Hypovolemic – extensive blood loss
3. Vascular shock – volume the same; abnormal vasodilation
-a. Anaphylaxis – systemic allergic reaction; histamine is a
vasodilator
-b. Neurogenic shock – failure of autonomic nervous system
regulation
-c. Septic shock – bacterial infection; toxins are
vasodilators
4. Cardiogenic shock – heart can not sustain adequate
circulation
BLOOD VESSELS
Pulmonary and systemic circulation
1. Pulmonary circulation – right ventricle to lungs and back
to left atrium
-a. Pulmonary trunk – from right ventricle
-b. Pulmonary arteries – right and left
-c. Pulmonary veins – from lungs back to left atrium
2. Systemic circulation – the rest to be considered
The aorta and major arteries
1. Ascending aorta – from left atrium
-a. Coronary arteries – from base of aorta
2. Aortic arch – arches over
-a. Brachiocephalic artery – right
-b. Left common carotid artery – middle
-c. Left subclavian artery – left
3. Thoracic (descending) aorta – to diaphragm
4. Abdominal aorta – several branches off
-a. Common iliac arteries – right and left
Arteries of the head and neck
1. Common carotid artery – branches
-a. External carotid artery – superficial head
-b. Internal carotid artery – carotid canal of temporal
bone; eyes; to Circle of Willis
2. Anterior cerebral artery – medial surface of cerebral
hemisphere
3. Middle cerebral artery – lateral fissure; lateral brain
4. Posterior cerebral artery – posterior brain
5. Circle of Willis – made up of
-a. Anterior communicating artery – between internal
carotids
-b. Posterior communicating artery – left and right;
complete the circle of Willis
6. Vertebral artery – from subclavian artery through foramen
magnum; to basilar
7. Basilar artery – vertebral arteries fuse; branches to
inner ear, pons, cerebellum
8. Subclavian – it and common carotid branch off
braciocephalic
Arteries of the upper limb
1. Axillary artery – continuation of the subclavian artery
2. Brachial artery – medial humerus; anterior flexors of arm
-a. Deep brachial artery – major branch; posterior triceps
brachii
3. Radial artery – lateral muscles of forearm, wrist, thumb
and index finger
4. Ulnar artery – serves the medial forearm muscles and
other fingers
5. Palmar arches – deep and superficial anastomoses of the
ulna and radius
6. Metacarpal arteries – supply fingers; form deep palmar
arch
7. Digital arteries – supply fingers; from superficial
palmar arch
Arteries of the thorax
1. Anterior intercostal arteries – anterior intercostal
muscles
2. Posterior intercostal arteries – intercostal muscles
3. Thoracic aorta – descends to the diaphragm
Arteries of the abdomen
1. Celiac trunk – thick short vessel with other vessels
branching off
-a. Common hepatic artery – to liver
-b. Left gastric artery – stomach right (lesser) curvature
-c. Splenic artery – runs deep to stomach; terminates as
branches in spleen
2. Superior mesenteric artery – single; arterial supply most
of intestine
3. Suprarenal arteries – flank origin of superior mesenteric
artery; adrenal glands
4. Renal arteries – kidneys
5. Gonadal arteries – testicular arteries and ovarian
arteries
6. Inferior mesenteric artery – serves distal part of the
large intestine
7. Common iliac arteries – aorta splits; to lower limb
Arteries of the pelvis and lower limbs
1. Common iliac artery – splits into internal and external
iliac arteries
2. Internal iliac artery – pelvic walls and viscera
3. External iliac artery – anterior abdominal wall lower
limb; become femoral
4. Femoral artery – major branch off external iliac; medial
thigh; becomes popliteal
5. Popliteal artery – supplies knee region; anterior and
posterior tibial arteries
6. Anterior tibial artery – supplies anterior leg muscles;
becomes dorsalis pedis
7. Dorsalis pedis artery – ankle and dorsum of foot
8. Posterior tibial artery – calf muscles; become medial and
lateral plantar arteries
9. Plantar arch – from medial and lateral plantar arteries
and dorsalis pedis
Vena cavae and the major veins of the systemic circulation
1. Superior vena cava – all systemic superior to diaphragm
2. Brachiocephalic veins – right and left; split into
3. Internal jugular vein – to brain
4. Subclavian vein – to arm
5. Inferior vena cava – all systemic inferior to diaphragm
6. Common iliac veins – right and left
Veins of the head and neck
1. External jugular vein – drains superficial scalp and
face; into subclavian vein
2. Vertebral vein – cervical vertebrae, spinal cord, some
neck
3. Internal jugular vein – drains brain
4. Superior sagittal sinus – falx ceribri; singular
5. Inferior sagittal sinuses – falx ceribri; singular
6. Straight sinus – drains inferior sagittal sinus; singular
7. Transverse sinuses – drain superior sagital and straight
sinuses; double
8. Sigmoid sinuses – drain transverse; into internal jugular
Veins of the upper limbs
1. Deep veins – same name as corresponding arteries and
drain the same areas
-a. Palmar venous arches – deep and superficial both into
radial and ulnar vein
-b. Radial vein – lateral arm
-c. Ulnar vein – medial arm
-d. Brachial vein – arm; from both ulnar and radial veins
-e. Axillary vein – axillary; drains brachial
-f. Subclavian vein – drains axillary; other arm veins
2. Superficial veins – some variation
-a. Dorsal venous arch – plexus of veins on the dorsal of
the hand
-b. Cephalic vein – from dorsal venous arch up lateral arm;
to axillary vein
-c. Basilic vein – posterior medial joins brachial
-d. Median cubital vein – joins the cephalic and basilic
-e. Median vein – between ulnar and radial vein can
terminate in either
Veins of the thorax
1. Azygos system – laterally flank the vertebral column
-a. Azygos vein – lateral right vertebral column; empties
into the superior vena cava
-b. Hemiazygos vein – lateral left vertebral column; crosses
mid thorax to azygos
Veins of the abdomen
1. Gonadal – right to inferior vena cava; left joins renal
vein
2. Renal veins - kidneys
3. Suprarenal veins – right to inferior vena cava; left
joins renal vein
4. Hepatic portal vein – begins hepatic portal system many
contributors
-a. Superior mesenteric vein – small intestine, part of
large intestine, and stomach
-b. Spleenic vein – spleen and part of stomach and pancreas
-c. Inferior mesenteric vein – distal large intestine and
rectum
6. Hepatic veins – from liver to inferior vena cava
Veins of the pelvis and lower limbs
1. Common iliac vein – inferior vena cava splits
1. Internal iliac vein – pelvic cavity
2. External iliac vein – becomes the femoral vein
3. Femoral vein – drains deeps structure in thigh
4. Popliteal vein – crosses the back of the knee
5. Anterior tibial vein – anterior leg
6. Dorsalis pedis vein – dorsal foot; to anterior tibial
7. Posterior tibial vein – posterior leg
8. Plantar arch – from medial, lateral plantar veins; from
posterior tibial artery
9. Greater saphenous veins - medial leg to femoral vein;
superficial; longest