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Dissection of major arterial pathways

Anterior view

Dissection of aortic arch and its branches

Anterior view

The left ventricle pumps blood into the much larger

systemic circulation, which is distributed throughout

all the body’s tissues. Unlike the smaller pulmonary

Systemic Circuit

circuit, the extensive systemic circuit serves a multitude of functions before returning to the right atrium:

(1) it distributes the necessary nutrients and other supplies to all the body cells while removing their

metabolic wastes; (2) it acquires metabolic fuel through the lining of the digestive system to distribute

throughout the body; (3) it expels wastes and excess water and adjusts the body’s electrolyte composition through its association with the tubes of the kidney; (4) it distributes generated heat throughout

the body and plays an important role in adjusting heat loss to the external environment as it courses

through the skin; and (5) it distributes hormones, regulatory chemical-messenger molecules secreted

by endocrine glands, to various sites of action throughout the body.

 1 Aorta

 2 Brachiocephalic artery

 3 Right common carotid artery

 4 Right subclavian artery

 5 Right internal thoracic artery

 6 Left common carotid artery

 7 Left subclavian artery

 8 Left axillary artery

 9 Left brachial artery

10 Left ulnar artery

 11 Left radial artery

12 Left radial recurrent artery

13 Coeliac trunk

14 Common hepatic artery

15 Left gastric artery

16 Splenic artery

17 Superior mesenteric artery

18 Right renal artery

19 Left renal artery

20 Inferior mesenteric artery

21 Common iliac arteries

22 Internal iliac arteries

23 External iliac artery

24 Femoral artery

25 Deep femoral artery

26 Popliteal artery

27 Azygos vein

28 Thyroid gland

29 Trachea

30 Ligamentum arteriosum

31 Vagus nerve

32 Phrenic nerve

33 Anterior scalene muscle

34 Brachialis muscle

35 Brachioradialis muscle

36 Innermost intercostal muscles

37 Quadratus lumborum muscle

38 Psoas major muscle

39 Clavicle

40 First rib

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 1 Coronary sinus

 2 Right coronary artery

 3 Conus arteriosus branch

 4 Marginal branch

 5 Anterior interventricular artery

 6 Lateral branches

 7 Circumflex branch of left coronary

 8 Posterior interventricular artery

 9 Anterior cardiac vein

10 Great cardiac vein

 11 Posterior vein of left ventricle

12 Middle cardiac vein

13 Oblique vein

14 Aorta

Dissection of coronary arteries and cardiac veins

Anterior view

Dissection of coronary arteries, coronary sinus, and cardiac veins

Posterior view

The coronary arteries are the fi rst branches of the aorta. These important vessels

provide the constantly needed blood supply to the heart. The left coronary artery is,

on average, larger than the right coronary artery and supplies a greater percentage

Heart Vessels

of the heart tissue. Accompanying the branches of the coronary arteries, a series of cardiac veins emerge from the capillaries of the heart to return blood to the right atrial chamber, either by entering directly or by joining the large coronary sinus,

which enters the right atrium from the posterior side.

15 Pulmonary trunk

16 Superior vena cava

17 Left atrium

18 Right atrium

19 Right ventricle

20 Left ventricle

21 Pulmonary veins

22 Pulmonary artery

23 Inferior vena cava

24 Ligamentum arteriosum

25 Brachiocephalic artery

26 Left common carotid artery

27 Left subclavian artery

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 1 Internal carotid artery

 2 Basilar artery

 3 Vertebral artery

 4 Posterior cerebral artery

 5 Posterior communicating artery

 6 Middle cerebral artery

 7 Posterior inferior cerebellar artery

 8 Posterior superior cerebellar artery

 9 Common carotid artery

10 External carotid artery

 11 Superior thyroid artery

12 Ascending pharyngeal artery

13 Lingual artery

14 Facial artery

15 Occipital artery

16 Posterior auricular artery

17 Superficial temporal artery

18 Transverse facial artery

19 Maxillary artery

20 Optic chiasm

21 Thyroid gland

22 Trigeminal nerve

23 Lateral pterygoid muscle

24 Temporal lobe of cerebrum

25 Zygomatic arch

Dissection of branches of external carotid artery

Lateral view

Dissection of basilar artery

Inferior view

Like the heart, which needs a constant, uninterrupted blood

supply, the brain tissue also must be guaranteed of a continuous perfusion in order to maintain its crucial functions. The

Head Vessels

common carotid arteries, arising from the aortic arch, bifurcate into external and internal carotids. The

external carotid supplies all tissues of the head except the brain, while the function of the internal

carotid is to supply the brain. Because of the brain’s critical vascular needs the internal carotid artery

has a partner, the vertebral artery, which courses cranially from the subclavian artery to assist with the

essential blood supply to the brain.

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Head Vessels

Deep dissection series of head with facial and anterior neck anatomy

removed exposing internal carotid and vertebral arteries

Anterior views

 1 Internal carotid artery

 2 Vertebral artery

 3 Basilar artery

 4 Middle cerebral artery

 5 Anterior cerebral artery

 6 Anterior communicating artery

 7 Posterior communicating artery

 8 Cerebral veins

 9 Cerebellar veins

10 Superior sagittal sinus

 11 Transverse sinus

12 Inferior sagittal sinus

13 Sigmoid sinus

14 Opening of straight sinus

15 Confluence of the sinuses

16 Dura mater

17 Pia-arachnoid mater

18 Spinal cord

19 Vertebral body

20 Cervical transverse process

21 Temporal lobe of cerebrum

22 Pituitary gland

23 External acoustic meatus

24 Pons

25 Frontal lobe of cerebrum

26 Vagus nerve

27 Cervical sympathetic trunk

28 Superior cervical ganglion

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Unlike the internal and external carotid arteries, the internal and external jugular veins form a wide array of collateral circuitry.

The major structural difference of the venous pathways in the head is the existence of dural venous sinuses within the skull.

The dural venous sinuses are non-collapsible, endothelial lined spaces within the tough meningeal dura mater. All the

smaller veins draining capillaries within the brain tissue enter into the dural venous sinuses. These dural sinuses converge

with one another throughout the skull to exit the cranial vault via the internal jugular vein.

Dissections of dural venous sinuses and cerebral veins

Posterior view (top), lateral view (bottom)

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The arterial pathway into the upper

limb consists of a single, major arterial roadway that gradually tapers as

Superior Limb Vessels

Dissection of subclavian and axillary arteries

Anterior view

it gives rise to the various branches that supply the tissues of the limb. This large arterial roadway

begins as the subclavian artery, takes on regional names — the axillary artery and brachial artery —

as it tapers distally, then branches into the radial and ulnar arteries, which course through the antebrachium, paralleling the bones of the same names. The radial and ulnar arteries terminate as the

collateral arches in the hand. This central pathway through the limb is the sole blood supply to this

region, supplying the integument, muscles, bones, joints, and connective tissues of the upper limb.

The deep venous pathways follow the arteries and have similar names. However, superfi cial veins

that have no arterial counterparts aid the deep veins in returning blood to the heart.

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Dissection of subclavian and axillary arteries

Anterosuperior view

 1 Brachiocephalic artery

 2 Common carotid artery

 3 Vertebral artery

 4 Subclavian artery

 5 Thyrocervical trunk

 6 Inferior thyroid artery

 7 Ascending cervical artery

 8 Suprascapular artery

 9 Dorsal scapular artery

10 Axillary artery

 11 Superior thoracic artery

12 Thoracoacromial trunk

13 Pectoral artery

14 Acromial artery

15 Clavicular artery

16 Deltoid artery

17 Lateral thoracic artery

18 Subscapular artery

19 Circumflex scapular artery

20 Thoracodorsal artery

21 Posterior circumflex humeral artery

22 Anterior circumflex humeral artery

23 Brachial artery

24 Deep artery of arm

25 Internal thoracic artery

26 Internal thoracic vein

27 Anterior scalene muscle

28 Middle scalene muscle

29 Deltoid muscle

30 Pectoralis minor muscle

31 Pectoralis major muscle

32 Subscapularis muscle

33 Teres major muscle

34 Latissimus dorsi muscle

35 Serratus anterior muscle

36 Phrenic nerve

37 Brachial plexus

38 Clavicle

39 First rib

40 Suprascapular nerve

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 1 Testis

 2 Interstitial (Leydig) cell

 3 Basement membrane

 4 Sertoli cell

 5 Spermatogonium

 6 Primary spermatocyte

 7 Secondary spermatocyte

 8 Spermatid

 9 Seminiferous tubule

10 Tunica albuginea

 11 Epididymis

12 Spermatic cord

Sagittal section of left testis

Medial view

Photomicrograph of testis

40x

The testes are oval-shaped organs about 2 inches (5 cm) long and 1 inch (2.5 cm) wide

that occupy the scrotal sac of a male. They are covered by a tough fi brous tunic and

wrapped in a serous sac that separates them from the external tissues that surround

Testes

them. Internally, the testes consist of numerous small compartments created by connective tissue bands that

project inward from the outer fi brous tunic. Each testicular compartment is occupied by a thin, highly coiled

seminiferous tubule. This thin tube is the site of sperm production. Situated between the tubules are the interstitial cells (of Leydig). It is these large interstitial cells that secrete the steroidal hormones in the testis.

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In addition to the endocrine organs discussed

on the preceding pages, there are other endocrine tissues in the body. These include tisOther Endocrine Structures

Other organs with endocrine tissues

Stomach (upper left), kidney (upper right), heart (lower right),

placenta (lower left), and adipose tissue (center)

sues in the wall of the gastrointestinal tract that produce hormones such as gastrin and secretin, tissues in the kidney that

produce renin and erythropoietin, tissues in the atrium of the heart that produce atrial natriuretic peptide, tissues of the placenta that produce human chorionic gonadotropin, estrogens, and progesterone, and adipose tissue that produces leptin.

These hormones have a variety of functions, from stimulating the release of digestive enzymes, to raising blood pressure,

to decreasing blood pressure, to regulating reproductive cycles, and suppressing appetite.

261

16 Cardiovascular System

If you have ever planted a

 garden of signifi cant size, you have probably experienced the importance of an irrigation system. At its simplest, an irrigation system is

a network of channels or furrows that deliver needed water from

one main source to the roots of all the garden’s plants. Like an

irrigation system, the body’s blood vessels form an extensive

network of “irrigation channels” to deliver needed fl uid — in

this case the homeostatically maintained blood — to all the

body’s cells. In fact, this delivery system is probably the most

phenomenal irrigation network imaginable. Emanating

from a muscular pump, the heart, these vessels form an

 extensive system of tubular roadways that carry nourishing

blood away from the heart and toward the tissues. Th ey

then make a “U-turn” through small permeable, exchange

vessels, the capillaries, which feed all the body’s cells. Here,

life-supporting molecules, such as water, oxygen, glucose,

and amino acids are delivered to the cells, and the by-products

of cellular metabolism are picked up from the surrounding

tissue fl uid. Th e blood then fl ows back to the heart through

a series of return vessels, the veins, that parallel the delivery

vessels. Th is circular pattern of fl ow to and from the heart

constitutes the vascular (blood vessel) component of the

 cardiovascular (circulatory) system. Th is irrigation network

is so impressive, that if all the blood vessels of the body were

placed end-to-end they would extend 25,000 miles (96,500 km),

which is approximately two times the equatorial circumference

of the earth.

Th e irrigation network of blood vessels are of no value without

a pump. Th e heart is the dual, self-regulating pump that generates

the pressure to drive the blood through this impressive irrigation

network. It pumps the blood through two cycles — a pulmonary

cycle to pick up oxygen from the lungs and a systemic cycle to deliver

the oxygen to all the cells of the body. Soon aft er conception, and up

until death, the heart pumps blood. It averages approximately 70 beats

per minute, or about 3 billion contractions in an average lifetime.

Th e fi nal aspect of the cardiovascular system is the accessory drainage

network — the lymphatics. Th ese small vein-like vessels insure that the

cardiac return equals the cardiac output. Th is chapter will depict the anatomy

of this amazing muscular pump and the vascular and lymphatic roadways that

distribute the blood throughout the body.

Find more information

about the cardiovascular

system in

REAL ANATOMY

262

 1 Erythrocyte (red blood cell)

 2 Leukocyte - neutrophil (white blood cell)

 3 Leukocyte - monocyte (white blood cell)

 4 Thrombocyte (platelet)

 5 Blood plasma

Blood smear

700x

In the histology chapter we learned that the fl uid material we call blood has been historically classifi ed as

a connective tissue. This classifi cation was a result of the fact that, like other connective tissues, blood

has more extracellular matrix than cells. More recently, however, blood has been placed in a tissue catBlood

egory of its own — the hematolymphoid complex. The extracellular portion of the blood is a water solution that gives rise to

its liquid nature. Blood is closely related to other aqueous fl uids within the body, in fact most of the other body fl uids, such

as interstitial fl uid, lymph, cerebrospinal fl uid, and aqueous humor, arise from the blood. These extracellular fl uids are the

water environment that nourish, protect, and exchange with every cell of the body. This water environment is derived from

the blood, renewed by the blood, and returned to the blood. Dispersed in the blood plasma are the three groups of blood

cells — erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets). The blood smear below

depicts the three cell categories.

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Heart

Posterior view

Heart

Anterior view

From its origin in the embryo as a simple pumping tube, the heart develops into a strong fi bromuscular

organ. During its development the original tubular pump is folded and subdivided into a four chambered

organ that has a pyramidal or conical form. It is approximately the size of a closed fi st and weighs

Heart

approximately 300 grams in males and a little less than this in females. For its small size, comprising only one half of one

percent of the total body mass, it is an important and functionally amazing organ. The wall of the heart consists of three

structural layers that each play signifi cant roles in its function as an effi cient pump. While the tissue makeup of this wall is

similar at any location in the heart, the thickness can vary considerably. Internally a septum and series of valves divide the heart

into four chambers through which the blood moves in a unidirectional fl ow. The chambers differ in structure and function, which

is primarily refl ected in the anatomy of their walls. Embedded within the walls of heart is a special electrical conduction system

that helps regulate its coordinated pumping action.

 1 Right atrium

 2 Left atrium

 3 Right ventricle

 4 Left ventricle

 5 Right auricle

 6 Left auricle

 7 Aorta

 8 Brachiocephalic artery

 9 Left common carotid artery

10 Left subclavian artery

 11 Pulmonary trunk

12 Right pulmonary artery

13 Left pulmonary artery

14 Ligamentum arteriosum

15 Superior vena cava

16 Inferior vena cava

17 Coronary sinus

18 Right coronary artery

19 Conus arteriosus branch

20 Marginal branch

21 Anterior interventricular artery

22 Lateral branches

23 Circumflex branch

24 Posterior interventricular artery

25 Anterior cardiac vein

26 Great cardiac vein

27 Posterior vein of left ventricle

28 Middle cardiac vein

29 Small cardiac vein

30 Right superior pulmonary vein

31 Right inferior pulmonary vein

32 Left superior pulmonary vein

33 Left inferior pulmonary vein

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Dissection of heart and pericardial sac

Anterolateral view

Transverse section of heart comparing ventricle thickness

Inferior view, left ventricle at right

Dissected heart showing interior of chambers

Anterior view

Heart

 1 Parietal pericardium

 2 Fibrous pericardium

 3 Visceral pericardium

 4 Epicardium

 5 Myocardium

 6 Endocardium

 7 Right atrium

 8 Right auricle

 9 Interatrial septum

10 Fossa ovalis

 11 Crista terminalis

12 Valve of inferior vena cava

13 Pectinate muscle

14 Tricuspid valve

15 Chordae tendineae

16 Trabeculae carnae

17 Papillary muscle

18 Right ventricle

19 Pulmonary valve

20 Left atrium

21 Left auricle

22 Bicuspid valve

23 Left ventricle

24 Aortic valve

25 Apex

26 Aorta

27 Brachiocephalic artery

28 Left common carotid artery

29 Left subclavian artery

30 Pulmonary trunk

31 Left pulmonary artery

32 Ligamentum arteriosum

33 Anterior interventricular artery

34 Lateral branches of interventricular artery

35 Superior vena cava

36 Right coronary artery

37 Left coronary artery

38 Right pulmonary veins

39 Left pulmonary veins

40 Diaphragm

41 Lung

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Dissection of heart revealing tricuspid valve

Anterior view

Heart dissection with atria and arteries removed

Superior view, anterior at top

Aortic valve

Superior view

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Muscular artery

100x

Elastic lamellae of aorta

640x

Section of aorta — large elastic artery

100x

Like all tubes in the body, blood vessels have a basic pattern of design that involves

three structural tunics, or layers. The inner layer of the vessel is the tunica intima.

This consists of the luminal endothelium and a thin network of underlying elastic

Blood Vessels

connective tissue. The middle layer of the vessel is the tunica media, which consists of varying amounts of smooth muscle

and elastic connective tissue. Variations in the tunica media defi ne the different types of blood vessels. The outer layer, the

tunica externa, is a dense connective tissue outer coat. The designations — elastic arteries, muscular arteries, arterioles,

venules, and veins — are based on size differences and the differences in the vessels’ tunica media. Elastic arteries have

a thick elastic tunica media. Muscular arteries have a tunica media dominated by smooth muscle. Arterioles are tiny arteries

with a muscular tunica media. All the venous vessels have a thin, almost non-existent tunica media. The smallest blood

vessels, the capillaries, loose all the layers of their wall except the inner endothelium. These microscopic, thin walled tubes

become the exchange vessels of the system.

 1 Endothelium of tunica intima

 2 Internal elastic membrane of tunica intima

 3 Elastic lamellae of tunica media

 4 Smooth muscle cells of tunica media

 5 Connective tissue of tunica externa

 6 Red blood cells

 7 White blood cells

 8 Venous valves

 9 Nerve

10 Striated skeletal muscle

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Arteriole

500x

Capillary

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Neurovascular bundle — note thin-walled vein fi lled with red

blood cells (6) compared to thick-walled muscular arteries (4)

100x

Longitudinal section of vein showing valves

Anterior view

Transverse section of vein showing valves

Superior view

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 1 Heart

 2 Pulmonary trunk

 3 Right pulmonary artery

 4 Left pulmonary artery

 5 Right superior pulmonary vein

 6 Right inferior pulmonary vein

 7 Left superior pulmonary vein

 8 Left inferior pulmonary vein

 9 Aorta

10 Right coronary artery

 11 Left coronary artery

12 Right common carotid artery

13 Right subclavian artery

14 Left common carotid artery

15 Left subclavian artery

Dissections of pulmonary trunk, arteries, and veins

Anterosuperior view below, anterior view above

The vascular system consists of two long circular loops of continuous

branched tubing that each begin and end with the heart. Leaving the

right ventricle and returning to the left atrium is the smaller pulmonary

Pulmonary Circuit

circulation. This circular loop courses through the lung tissues where its smallest vessels form an extensive interface with

the small air sacs of the lungs. This important interface is the site of exchange of O2

 and CO2

 between the blood and air.

16 Superior vena cava

17 Inferior vena cava

18 Trachea

19 Right principal bronchus

20 Left principal bronchus

21 Esophagus

22 Thyroid gland

23 Vagus nerve

24 Pulmonary plexus

25 Posterior vagal trunk

26 Esophageal plexus

27 Anterior vagal trunk

28 Anterior scalene muscle

29 Cricothyroid muscle

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