This document discusses the anatomy and function of arteries and arterioles. It defines arteries as blood vessels that carry oxygenated blood away from the heart, while arterioles are smaller vessels that branch off arteries and lead to capillaries. The document then describes the two types of arteries - elastic and muscular arteries - and provides examples of each. It also outlines the three layers (tunica) that make up the wall of arteries - the innermost intima layer, middle media layer, and outer adventitia layer. Finally, it states that arterioles have the greatest influence on local blood flow and overall blood pressure through their ability to variably contract.

1. ARTERIES
AND
ARTERIOLES
NAME: BETTY ANDY-NWEYE
CLASS: PRE MED FOUR
COURSE: PHYSIOLOGY

2. INTRODUCTION
 Arteries are blood vessels that carry blood away
from the heart. The blood is normally oxygenated
except the case of the pulmonary and umbilical
arteries.
 Arterioles are small diameter blood vessels in the
microcirculation that extends and branches out from
an artery and leads to capillaries.
 NOTE: pulmonary arteries carry deoxygenated
blood that has just returned from the body to the
heart and takes it to the lungs where carbon dioxide
is exchanged for oxygen.

3. Artery
 The main functions of arteries is to carry blood away
from the heart to other organs in the body
 The systemic arteries are subdivided into two types
according to their relative compositions of elastic
and muscle tissue as well as their size and makeup.
They are:
1. Elastic (large conducting) arteries
2. Muscular (medium size distributing) arteries

4. Elastic arteries

These arteries are important for helping to propel blood onward while the ventricles are relaxing

Their walls stretch to accommodate the surge of blood from the left ventricles during systole.

Examples of elastic arteries are;
1.
Aorta- root systemic artery
2.
Brachiocephalic artery- an artery of the mediastinum that supplies blood to the right arm, head and neck
3.
Right and left common carotid arteries
4.
Right and left subclavian arteries
5.
Right and left vertebral arteries
6.
Right and left common iliac arteries

5. Arteries continued…
 The elastic fibers of the above mentioned arteries
function as pressure reservoir.
 Pressure reservoir: stretched elastic arteries
momentarily store some of this energy and
therefore function as pressure reservoirs. During
systole, the elastic fibers recoil, converting their
stored energy into kinetic energy thereby pushing
blood forward in the vascular system in a more or
less continuous fashion.

7. Muscular arteries
 These are arteries that branch out into various
regions of the body
 These arteries branch from larger, more elastic
arteries and perform the function of distributing
blood to various parts and regions of the body
 They have more smooth muscle than elastin in
their tunica media and are therefore, capable of
vasoconstriction and vasodilation than are elastic
arteries.

8. Muscular arteries are:
 Brachial artery- arm
 Radial artery- forearm

9. Structure of an artery
 Arteries consist of three layers or coats surrounding
a hollow center called the lumen.
 Three layers of an artery are:
1. Tunica interna/intima
2. Tunica media
3. Tunica adventitia

10. Tunica interna
 This is the proximal and innermost coat of all blood
vessels
 It is in direct contact with the flow of blood
 It consists of a simple squamous endothelium lying
on its basement membrane and a thin connective
tissue component called the internal elastic lamina
 This layer is made up of mainly endothelial cells
 The hollow internal cavity which the blood flows is
lumen

11. Tunica media
 This is the middle layer that is made up of smooth
muscle cells and elastic tissue
 Thick layer
 It consists of elastic fibers and smooth muscle
which are arranged circularly about the artery like a
ring
 Due to their elastic fibers, walls can stretch easily or
expand in response to increase in pressure

12. Tunica
adventitia/externa
 The outermost layer
 Consists of two components: elastin fibers and
collagen fibers which form a connective tissue wrap
for the vessel

14. Arterioles
 These are the smallest of the true arteries
 Branches from the medium size arteries and begin
to loose wall thickness
 Helps to regulate blood pressure by the variable
contraction of the smooth muscle of their walls
 They deliver blood to the capillaries

15. Arterioles and blood
pressure
 Arterioles have the greatest influence on both local
blood flow and on overall blood pressure. They are
the primary “adjustable nozzles” in the blood
system, across which the greatest pressure drop
occurs.
 The combination of heart output and systemic
vascular resistance, which refers to the collective
resistance of all of the body’s arterioles, are the
principal determinants of arterial blood pressure at
any given moment.