2122 Vessels

Blood Vessels
Types of Blood Vessels

Arteries - vessels that transport
blood away from the heart
Veins - return blood back to the
heart
Capillaries - microscopic blood
vessels that allow exchanges
between blood and tissues
Structure of a blood
vessel
Tunica externa (adventitia) - outermost layer

made of loose connective tissue. Serves to
anchor, protect and prevent overstretching
Tunica media - middle layer composed of
smooth muscle; functions in dilation and
constriction of blood vessels
Tunica interna(intima) - innermost layer
made of endothelium (s.squamous
epithelium)
Blood flow through tissues
From the heart blood flows into

Aorta
Arteries
Arterioles
Capillaries
Venules
Veins
Superior/ Inferior Vena Cava
Back to the heart
Arteries
Elastic (conducting) arteries
Muscular ( distributing) arteries
Medium arterties
Arterioles
Larger arteries
Tiny , tiny arteries
Metarteriole
Capillaries
Microscopic vessels that connect

arterioles and venules
Walls consist of a single layer of
simple squamous epithelial cells that
allow the exchange of gases
Precapillary sphincters regulate
blood flow
Continuous/Fenestrated capillaries
Veins
Venules merge to form veins

Have 3 distinct layers; thinner
walled than arteries due to thin
tunica interna and media
Large lumens and posses valves
Varicose veins
Blood reservoir
Systemic Circulation
The aorta and its major branches

Arterial supply to neck and head
Arterial supply to upper extremities
Arterial supply to thorax
Arterial supply to abdomen
Arterial supply to pelvic region and
lower extremities
Systemic Veins
Venous drainage of the head and

neck
Major tributaries of the inferior vena
cava
Venous drainage of the upper
extremities
Venous drainage of the lower
extremities
Hepatic Portal System
Routes blood from the stomach,

spleen, pancreas, small and large
intestines to the liver
Blood from these structures all drain
into the hepatic portal vein, then
into the liver
Blood is returned to the inferior
vena cava via the hepatic vein
Fetal Circulation
Placenta - site where exchange of

materials between fetus and mother
occur
Umbilical arteries (2) - carry fetal
blood high in CO2 / low in O2 to the
placenta
Umbilical vein - returns oxygenated
blood from the placenta to the fetus
Fetal Circulation
Ductus venosus - allows blood to

bypass the liver
Foramen ovale - opening in interatrial
septum allowing blood to bypass the
lungs Blood flows from r.atrium
->l.atrium
Ductus arteriosus - vessel connecting
pulmonary artery to the aorta
A. Great Vessels
1.
2.
3.
4.
superior vena cava

inferior vena cava
pulmonary veins
pulmonary trunk (p. artery, p. aorta)
5. systemic aorta
Branches of systemic
aorta
1. from ascending aorta, right and left

coronary artery
2. from aortic arch, brachiocephalic artery
a. right subclavian artery
(1) r. axillary artery
(a) r. brachial artery
1. r. ulnar artery
2. r. radial artery
aorta
3. superficial and deep

palmar arches
(anastomoses)
(b) deep brachial artery
(c) posterior circumflex
(2) r. vertebral artery
aorta
b. right common carotid artery

(a) r. external carotid artery
(b) r. internal carotid artery
c. (cat, not human) left common
carotid artery
(a) l. external carotid artery
(b) l. internal carotid artery
aorta
3. from aortic arch (human, not

cat),
left common carotid
artery
a. l. external carotid artery
b. l. internal carotid artery
aorta
4. from aortic arch, left subclavian

artery (cat and human)
a. l. axillary artery
(1) l. brachial artery
(a) l. ulnar artery
(b) l. radial artery
(c) superficial and deep palmar
arches (anastomoses)
aorta
(2) deep brachial artery

(3) posterior circumflex
b. l. vertebral artery
5. from descending thoracic aorta
a. paired bronchial arteries
b. paired intercostal arteries
aorta
6. from abdominal aorta

a. celiac trunk
(1) splenic artery
(2) l. gastric artery
(3) hepatic artery
aorta
b. superior mesenteric artery

c. paired renal arteries
d. paired gonadal arteries
e. paired lumbar arteries
f. inferior mesenteric artery
aorta
g. right and left common iliac arteries

(1) internal iliacs
(2) external iliacs->femorals->
popliteal->tibial->dorsalis
pedis->
plantar arches
C. Major veins
A. coronary circulation: coronary sinus

B. pulmonary circulation: pulmonary
veins
C. hepatic portal circulation: hepatic
portal vein drains
1. inferior mesenteric which drains
splenic vein
2. superior mesenteric vein
D. Cranial Circulation:
cranial venous
sinuses
E. Systemic Circulation:
1. superior vena cava drains

a. azygos system
b. right and left brachiocephalic veins
c. internal jugular and subclavian vein
d. external jugular and axillary
e. cephalic vein (superficial) and brachial
vein (deep) which drains radial, ulnar,
median cubital and basilic
veins
2. inferior vena cava drains

a. hepatic vein
b. phrenic vein
c. paired renal veins
d. paired gonadal veins
e. paired common iliac veins which drain

(1) paired internal iliac veins
(2) paired external iliac veins which
drain
(a) femoral veins which drain
1. popliteal veins which drain
a peroneal vein
b anterior and posterior
tibial veins
(b) great saphenous veins
Capillary Exchange
Mechanisms of Exchange
Diffusion - major method used to

exchange substances such as O2,
CO2, glucose, and amino acids
Vesicular transport - endocytosis
and exocytosis of lipid-insoluble
molecules
Bulk flow - involves filtration and
reabsorption
Arteries
Pressures
promoting
filtration
Blood hydrostatic
pressure***
Interstitial fluid
osmotic pressure
Veins
Pressures
promoting
reabsorption
Blood colloid
osmotic
pressure***
Interstitial fluid
hydrostatic
pressure
Physiology of Circulation
Important Terms
Blood Flow
Blood pressure
Resistance
Blood Flow
Blood flow - is the amount of blood

flowing through a tissue in a given
period of time
Velocity of blood flow is inversely
related to the diameter of the blood
vessel
Blood flows most slowly in areas of
greatest width
Blood Pressure
Force that the blood exerts against

the walls of a blood vessels
Factors affecting BP include cardiac
output, blood volume, viscosity,
resistance, and the elasticity of the
arteries
Cardiac Output
CO=Stroke volume X Heart Rate

Any factor that increases SV or HR will
increase blood pressure
Peripheral Resistance
Resistance to blood flow due to the

force of friction between vessel wall
and blood
Resistance affected by blood viscosity,
vessel length and vessel radius
Sources affecting
Resistance
Blood viscosity- how thick or thin the

blood is. Measured by hematocrit.
Vessel length- longer the vessel, the
greater the resistance, the greater the
BP
Vessel radius- smaller the vessel the
greater the resistance
Blood Volume
Blood volume , Blood pressure

Blood volume, Blood pressure
Blood volume & blood pressure
monitored by the cardiovascular
center in the medulla (ANS),
baroreceptors and chemoreceptors
and by hormonal regulation
Hormonal Regulation
of Blood Pressure
Renin- angiotensin pathway

Angiotensin II - powerful
vasoconstrictor thus raising resistance
Stimulates secretion of aldosterone
from the adrenal gland promoting
sodium retention
ADH - antidiuretic hormone from the
pituitary causing the kidneys to reabsorb
more water
Hormone lowering BP
ANP - atrial natriutic peptide

released by atrial cells promoting
the loss of salt and water in the
urine , thus blood volume and
causing vasodilation which then
blood pressure
PTH - parathyroid hormone causes
vasodilation
Endothelin = potent
vasoconstrictor
responds to
low blood flow
NO (nitrous oxide) = powerful
vasodilator; balances endothelin
and dilates vessels in response to
high blood flow.
Normal Blood Pressure
Newborn = 90/55 mm Hg
Adults = 120/80 mm Hg
Old Age = 150/90
Systolic Pressure = peak pressure
during systole
Diastolic pressure = lowest pressure
during diastole (filling of ventricles)

2122 Vessels

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2122 Vessels

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Blood Vessels

Types of Blood Vessels

Tunica externa (adventitia) - outermost layer

Blood flow through tissues

From the heart blood flows into

Elastic (conducting) arteries

Muscular ( distributing) arteries

Tiny , tiny arteries

Microscopic vessels that connect

Venules merge to form veins

The aorta and its major branches

Venous drainage of the head and

Hepatic Portal System

Routes blood from the stomach,

Placenta - site where exchange of

Ductus venosus - allows blood to

superior vena cava

1. from ascending aorta, right and left

3. superficial and deep

b. right common carotid artery

3. from aortic arch (human, not

4. from aortic arch, left subclavian

(2) deep brachial artery

6. from abdominal aorta

b. superior mesenteric artery

g. right and left common iliac arteries

A. coronary circulation: coronary sinus

1. superior vena cava drains

2. inferior vena cava drains

e. paired common iliac veins which drain

Diffusion - major method used to

Blood flow - is the amount of blood

Force that the blood exerts against

CO=Stroke volume X Heart Rate

Resistance to blood flow due to the

Blood viscosity- how thick or thin the

Blood volume , Blood pressure

Renin- angiotensin pathway

ANP - atrial natriutic peptide

Normal Blood Pressure

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