BIOS 255
(EDAPT WEEK 3)
Anatomy & Physiology III course with a lab
,Anatomy and Functional Roles of the Different Type of
Blood Vessels
Introduction
As mentioned in previous concepts, the heart generates different
pressures as it contracts and relaxes. Pressure generated by the muscular
pumping action of the heart is transferred to both the pulmonary (right
side) and systemic (left side) divisions of the circulatory system as blood is
ejected from the right and left ventricles during each beat. These blood
vessels include the arteries, arterioles, capillaries, venules, and veins.
Arteries, Capillaries, and Veins
We previously discussed the different structures of the heart and learned
about the flow of blood to and from the lungs. This was our introduction
to a few of the major vessels including the pulmonary artery and
veins. We will now begin comparing and contrasting what it means to be
an artery, a vein, and a capillary.
Arteries are vessels that transport blood away from the heart towards
the capillaries. These vessels are typically oxygen rich.
Veins are vessels that drain blood from the capillaries and transport
it towards to the heart. These vessels are typically oxygen poor.
Capillaries are microscopic vessels that allow for the exchange of
substances between the blood and tissues.
The Three Tunics
Each of the major blood vessels consist of 3 layers of tissues known as
tunics.
The tunica intima (interna) consists of a layer of simple squamous
epithelium bound to a subendothelial layer of areolar connective tissue.
,The tunica media consists primarily of smooth muscle with a framework
of elastic connective tissue.
The tunica externa (adventitia) consists of areolar connective tissue with
elastic and collagen fibers.
The major structural differences between the vessels include:
The tunica media will be thicker in the arteries than veins as they will
need to supply more pressure to the blood.
Veins and venules are the only blood vessels that contain valves to
prevent back flow.
Capillaries are only composed of a layer of endothelium and a
basement membrane.
Structure and Function of the
Specific Arteries
, With this understanding of the layers of the vessels, we can take a closer
look at some of the different types of blood vessels. Of all of the blood
vessels of the body, the arteries are the strongest and, in some cases, the
most elastic. Arteries can be subdivided into two categories, the elastic
arteries and the muscular arteries.
The elastic arteries are the largest arteries (2.5-1.0 cm in diameter) that
conduct blood from the heart to the more distant muscular arteries. The
tunica media consists of large portion of elastic fibers and less smooth
muscle than other classes of arteries. These vessels stretch to
accommodate blood being ejected from the left ventricle and the elastic
fibers help them ‘rebound’ to their original diameter, smoothing out
pulsatile blood flow (more on this later).
Elastic Artery
The muscular arteries are smaller than the elastic arteries (1.0 cm – 0.3
mm) and are farther from the heart. The tunica media of these vessels is
proportionally thicker than in elastic arteries and consists of multiple
layers of smooth muscle bound between distinct elastic lamina (“sheets”).
The extra muscle and reduced elastic fibers of the tunica media allows
these vessels to narrow (vasodilation) and widen (vasoconstriction) in
(EDAPT WEEK 3)
Anatomy & Physiology III course with a lab
,Anatomy and Functional Roles of the Different Type of
Blood Vessels
Introduction
As mentioned in previous concepts, the heart generates different
pressures as it contracts and relaxes. Pressure generated by the muscular
pumping action of the heart is transferred to both the pulmonary (right
side) and systemic (left side) divisions of the circulatory system as blood is
ejected from the right and left ventricles during each beat. These blood
vessels include the arteries, arterioles, capillaries, venules, and veins.
Arteries, Capillaries, and Veins
We previously discussed the different structures of the heart and learned
about the flow of blood to and from the lungs. This was our introduction
to a few of the major vessels including the pulmonary artery and
veins. We will now begin comparing and contrasting what it means to be
an artery, a vein, and a capillary.
Arteries are vessels that transport blood away from the heart towards
the capillaries. These vessels are typically oxygen rich.
Veins are vessels that drain blood from the capillaries and transport
it towards to the heart. These vessels are typically oxygen poor.
Capillaries are microscopic vessels that allow for the exchange of
substances between the blood and tissues.
The Three Tunics
Each of the major blood vessels consist of 3 layers of tissues known as
tunics.
The tunica intima (interna) consists of a layer of simple squamous
epithelium bound to a subendothelial layer of areolar connective tissue.
,The tunica media consists primarily of smooth muscle with a framework
of elastic connective tissue.
The tunica externa (adventitia) consists of areolar connective tissue with
elastic and collagen fibers.
The major structural differences between the vessels include:
The tunica media will be thicker in the arteries than veins as they will
need to supply more pressure to the blood.
Veins and venules are the only blood vessels that contain valves to
prevent back flow.
Capillaries are only composed of a layer of endothelium and a
basement membrane.
Structure and Function of the
Specific Arteries
, With this understanding of the layers of the vessels, we can take a closer
look at some of the different types of blood vessels. Of all of the blood
vessels of the body, the arteries are the strongest and, in some cases, the
most elastic. Arteries can be subdivided into two categories, the elastic
arteries and the muscular arteries.
The elastic arteries are the largest arteries (2.5-1.0 cm in diameter) that
conduct blood from the heart to the more distant muscular arteries. The
tunica media consists of large portion of elastic fibers and less smooth
muscle than other classes of arteries. These vessels stretch to
accommodate blood being ejected from the left ventricle and the elastic
fibers help them ‘rebound’ to their original diameter, smoothing out
pulsatile blood flow (more on this later).
Elastic Artery
The muscular arteries are smaller than the elastic arteries (1.0 cm – 0.3
mm) and are farther from the heart. The tunica media of these vessels is
proportionally thicker than in elastic arteries and consists of multiple
layers of smooth muscle bound between distinct elastic lamina (“sheets”).
The extra muscle and reduced elastic fibers of the tunica media allows
these vessels to narrow (vasodilation) and widen (vasoconstriction) in
