Laboratory Exercise 15: Anatomy of the Blood Vessels
Blood vessels, the tubes, transport blood to and from the tissues. Arteries carry blood
away from the heart to the tissues. In the tissues, the arterioles divide into smaller
vessels, the capillaries, where nutrients and wastes are exchanged.
From the tissues, the capillaries merge to form venules and veins, which return blood to
the heart. Lymphatic vessels act as auxiliary veins helps return tissue fluid to the
circulation. The lymphatic vessels originate as blind-ended vessels in the tissues. Blood
capillaries are open-ended vessels.
Heart
Veins
Arteries
large
elastic
medium
muscular
small
medium
venule
small
arteriole
Capillaries
where exchange occurs
A. Gross Anatomical Features of Blood Vessels
Arteries – are thick-walled structures to withstand high blood (hydrostatic) pressure. The
elastic membranes in their walls allows for expansion and control of the blood pressure.
The lumen is round and small in diameter.
Veins – are thin-walled structures, with less elastic membranes, and large diameter
lumen. Many veins and lymphatic vessels have valves in their walls. A valve consists of
two semilunar flaps that open to allow return of blood or lymph to the heart and close to
prevent backflow that results from the effect of gravity.
1
B. Microscopic Anatomy of Artery and Vein
The wall of a muscular artery is composed of three layers:
1. Tunica intima – inner layer of simple squamous epithelium (endothelium), a small
amount of loose connective tissue, and the internal elastic membrane circling the lumen
as the outer most part of the tunica intima.
2. Tunica media – thick middle layer composed of circular smooth muscle and broken
elastic membranes (fenestrated membranes). The external elastic membrane is the outer
most part of the tunica media.
3. Tunica externa (adventitia) – outer layer composed of loose connective tissue,
containing small nutrient vessels, vasa vasorum and small nerves of the autonomic
nervous system, nervi vasorum.
The smooth muscle of the tunica media regulates the lumen diameter of the muscular
arteries via the autonomic nervous system. Relaxation of the muscle increases lumen
diameter – vasodilation – and blood volume to a particular area. Contraction of the
muscle decreases lumen diameter – vasoconstriction – and blood volume to a particular
area.
The walls of the veins are composed of the same three layers, but are thinner as they are
not subjected to as much pressure as the artery’s wall and do not distribute blood to the
tissues but collects blood from the tissues. The vein walls are less muscular with a
reduced tunica media but a relatively thick tunica externa.
C. Major Blood Vessels
Outlined below are the main vascular circuits by which blood travels to and from the
heart. For arteries, begin with the heart, work distally. For veins, start peripherally and
trace the venous return to the heart. Names of blood vessels often reflect their location.
2
Outline of Major Systemic Arteries
A. Aorta and its Branches
Left ventricle
Aortic semilunar valve
Ascending aorta
left coronary artery
right coronary artery
Aortic Arch
Brachiocephalic
Right Common Carotid*
right side of head and neck
Right Subclavian → right upper extremity (see section B.)
Left Common Carotid*
left side of head and neck
Left Subclavian
left upper extremity (see section B.)
Thoracic Aorta
Intercostals
intercostals and chest muscles, pleurae
Superior Phrenics
posterior and superior surfaces of diaphragm
Bronchials
bronchi of lungs
Esophageals
esophagus
Abdominal Aorta
Inferior Phrenics
Celiac
inferior surface of diaphragm
Common Hepatic
liver
Left Gastric
stomach and esophagus
Splenic
spleen, pancreas, stomach
Superior Mesenteric
small intestine, cecum, ascending and transverse colon
Suprarenals → adrenal (suprarenal) glands
Renals → kidneys
Gonadals
Testiculars
Ovarians
Inferior Mesenteric
testes
ovaries
Transverse, descending, sigmoid colon, rectum
Common Iliacs (see section C.)
3
B. Arteries of the Upper Limb
Subclavian Artery
Axilliary Artery
Brachial Artery
arm
Radial Artery* (lateral)
forearm
Ulnar Artery (medial)
Palmer Arches
forearm
hand
C. Arteries of the Lower Limb
Common Iliac Artery
Internal Iliac Artery
External Iliac Artery
Femoral Artery*
pelvis and perineum
lower limb, lower abdominal wall
thigh region
Popliteal (behind the knee) Artery*
Anterior Tibial Artery
Tibioperoneal trunk
knee joint and popliteal region
Dorsalis Pedis Artery*
posterior leg
Posterior Tibial Artery
Peroneal Artery (lateral)
(fibular)
plantar region of foot
lateral leg region
*Blood vessels where pulse can be taken.
4
dorsum of foot
Outline of Major Systemic Veins
A. Veins of the upper limb
Venous Networks of Hand
Medial Basilic Vein
Cephalic Vein (Lateral)
(superficial arm and forearm)
Axilliary Vein
Internal Jugular Veins (large) drains blood from the veins
of brain, head and neck, these veins are medial.
External Jugular Veins (small) drains blood from veins
of superficial regions of head and neck, these veins are
lateral
Subclavian Vein
Brachiocephalic Vein
Superior Vena Cava
Right Atrium
Tricuspid valve
Right Ventricle
5
B. Veins of the Lower Limb
Dorsal / Plantar Venous Arches of Foot
Small Saphenous Vein
(posterior leg)
Deep Veins
(peroneal, anterior and posterior
tibialis draining the leg)
Great Saphenous Vein
(medial leg, anterior thigh)
Femoral Vein
(thigh)
External Iliac Vein
Popliteal Vein
(knee joint and popliteal region)
Common Iliac Vein
Inferior Vena Cave
Gonadal
(testes or ovary)
Renal
(kidney)
Suprarenal
(adrenal)
Hepatic
(liver)
Phrenic
(diaphragm)
Right Atrium
6
Arteries of the Brain - Circle of Willis
The major cerebral arteries form the circle of Willis. The circle of Willis surrounds the
infundibulum of the pituitary.
The anterior cerebral arteries are branches of the internal carotid arteries, the posterior
cerebral arteries are branches of the vertebral arteries. The vertebral arteries run through
the transverse foramen of the cervical vertebrae.
From internal carotid arteries there are the;
Anterior cerebral arteries, connecting the 2 anterior cerebral arteries is the
anterior communicating artery
Middle cerebral arteries
Posterior communicating arteries
From vertebral arteries the basilar artery branches off. The basilar artery then gives off the
cerebellar arteries along the base of the cerebellum.
From the basilar artery the posterior cerebral arteries branch off. Connecting the posterior
cerebral arteries to the anterior cerebral arteries are the posterior communicating arteries.
These 4 arteries form the circle of Willis.
D. Portal Circulation
For the most part venous blood follows a direct route to the right atrium. However, blood
leaving the stomach and intestines contain nutrients absorbed from the gastrointestinal
tract. The hepatic portal vein shunts this blood to the liver, to enable the liver to remove
nutrients for later use by the body’s cells and to detoxify harmful substances.
A portal system is one that begins and ends in capillaries. The hepatic portal system begins
in the capillaries of the gastrointestinal tract and ends in capillaries of the liver.
The hepatic portal vein forms from a merger of the superior mesenteric and splenic veins.
The splenic vein receives branches of the inferior mesenteric, pancreatic and short gastric
vein. The right and left gastric veins drain directly into the portal vein near the stomach’s
pyloric region.
Hepatic veins drain the blood from the liver into the inferior vena cava, which returns the
blood to the heart.
E. Lymphatic System
Lymphatic vessels collect excess tissue fluid and return it to the venous system. The
lymphatic system begins as blinded-ended capillaries within the intestinal villi. These
lymphatic capillaries are called lacteals. From the lacteals the lymph fluid flows into larger
and larger lymphatic veins. Along the path of the lymphatic veins are lymph nodes. The
7
lymph nodes house lymphocytes and macrophages that defend the body against foreign
substances. The nodes are in a strategic position to engulf and destroy antigenic materials
and so “sterilize” the lymph before it is returned to the blood circulatory system.
The large lymphatic veins then lead into two collecting ducts. The right lymphatic duct
drains the upper right side of the body and empties into the right subclavian vein. The
major collecting duct, the left lymphatic or thoracic duct, drains the rest of the body and
empties into the left subclavian vein.
8