Download Blood Vessels

WHAT ARE BLOOD VESSELS ?
 Blood vessels are intricate networks of tubes
that transport blood throughout the entire
body.
 They carry blood through miles in a never
ending stream. If you could take all the blood
vessels of a average size child and line them up
they could reach about 60,000 miles long. In
an adult, the blood vessels could reach 100,000
miles long.
 Part of the Circulatory System.
TYPES
 ARTERIES, ARTERIOLES
 VEINS, VENULES
 CAPILLARIES
ARTERIES & ARTERIOLES
 Transport Blood away from heart
 Wall are thicker than veins
 Walls made up of 3 layers
 When they are cut, they remain opened because of
their thick wall nature.
VEINS & VENULES
 Transport blood to the heart
 Wall are thinner than arteries
 Wall made up of same 3 layers
 When they are cut, they remain opened because of
their thick wall nature
STRUCTURE…
Composed Of Three Layers
(Tunics)

Tunica intima –is the
innermost layer, composed
of epithelium
 Tunica media –made up of
smooth muscle cells coated
with elastic tissue.
 Tunica externa (adventitia) –
Entirely composed of
connective tissue. It also
contains nerves that supply
the vessel.
Lumen
 Central blood-filled space of
a vessel
Major Types Of
Blood Vessels:
• Artery
• Vein
• Capillary
WALL OF BLOOD VESSELS
Structure of Blood Vessels
 Composed of three layers (tunics)
 Tunica intima – composed of simple squamous
epithelium
 Tunica media – sheets of smooth muscle


Contraction – vasoconstriction
Relaxation – vasodilation
 Tunica externa – composed of connective tissue
 Lumen
 Central blood-filled space of a vessel
Copyright © 2008 Pearson
Education, Inc., publishing as
Benjamin Cummings
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Copyright © 2008 Pearson
Education, Inc., publishing as
Benjamin Cummings
Figure 19.1a
Types of Arteries
 Elastic arteries – the largest arteries
 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
Copyright © 2008 Pearson
Education, Inc., publishing as
Benjamin Cummings
Figure 19.2a
 Muscular (distributing)
arteries
 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
Copyright © 2008 Pearson
Education, Inc., publishing as
Benjamin Cummings
Figure 19.2b
Capillaries
 Smallest blood vessels
 Diameter from 8–10 µm

Red blood cells pass through single file
 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
Copyright © 2008 Pearson
Education, Inc., publishing as
Benjamin Cummings
RBCs in a Capillary
Copyright © 2008 Pearson
Education, Inc., publishing as
Benjamin Cummings
Figure 19.3
Classification Of Vein
 Superficial veins
Superficial veins are those whose course is close to the surface of the body, and have no
corresponding arteries.
 Deep veins
Deep veins are deeper in the body and have corresponding arteries.
 Pulmonary veins
The pulmonary veins are a set of veins that deliver oxygenated blood from the lungs to the
heart.
 Systemic veins
Systemic veins drain the tissues of the body and deliver deoxygenated blood to the heart.
Comparism Btw Arteries and Veins
ARTERIES
VEINS
Transport blood away from the heart
Transport blood towards the heart
Carry Oxygenated blood ( except the
Pulmonary and Umbilical Artery)
Carry Deoxygenated Blood (except the
Pulmonary and Umbilical artery)
Have relatively narrow lumens
Have relatively wide lumens
Have relatively more muscle/elastic
tissue
Have relatively less muscle/elastic
tissue
Transport blood under higher pressure
Transport blood under lower pressure
than arteries
They do not have valves (except for the
semi-lunar valves of the pulmonary
artery and the aorta)
Have valves throughout the main veins
of the body. These are to prevent blood
flowing in the wrong direction, as this
could (in theory) return waste
materials to the tissue
ROLE IN DISEASE
 Main article: Vascular disease
 Blood vessels play a role in virtually every medical condition. Cancer,
for example, cannot progress unless the tumor causes
angiogenesis,(formation of new blood vessels) to supply the malignant
cells' metabolic demand. Atherosclerosis, the formation of lipid lumps
(atheromas) in the blood vessel wall, is the most common
cardiovascular disease, the main cause of death in the Western world.
 Blood vessel permeability is increased in inflammation. Damage, due
to trauma or spontaneously, may lead to haemorrhage due to
mechanical damage to the vessel endothelium. In contrast, occlusion
of the blood vessel by atherosclerotic plaque, by an embolised blood
clot or a foreign body leads to downstream ischemia (insufficient blood
supply) and possibly necrosis. Vessel occlusion tends to be a positive
feedback system; an occluded vessel creates eddies in the normally
laminar flow or plug flow blood currents. These eddies create
abnormal fluid velocity gradients which push blood elements such as
cholesterol or chylomicron bodies to the endothelium. These deposit
onto the arterial walls which are already partially occluded and build
upon the blockage.
 Vasculitis is inflammation of the vessel wall, due to autoimmune
disease or infection.