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10. Cardiovascular system

 

 

 


 

Fig. 10-1.

Components of the cardiovascular system are the heart and blood vessel (artery, vein, and capillary).

 


< Heart >

 

Fig. 10-2.

 

The heart is an organ with cardiac muscle (Fig. 16-30), which have a simple function to pump blood.

 

Fig. 10-3.

 

The heart is covered by the pericardium consisting of visceral and parietal pericardia (Fig. 8-35). The visceral pericardium is in close contact with the cardiac muscle, so the visceral pericardium is regarded as the outmost layer of the heart wall. Likewise, visceral peritoneum is regarded as the outmost layer of the gastrointestinal tract wall (Fig. 4-42).

 

Fig. 10-4. Pericardium.

 

On the other hand, the parietal pericardium sticks to the underlying diaphragm (Fig. 3-26).

 

Fig. 10-5. Anterior, anterior, middle, posterior mediastina (midsagittal plane).

 

Mediastinum is the thoracic cavity excluding the bilateral lungs. The mediastinum is subdivided into the superior, anterior, middle, and posterior mediastina. The inferior border of the superior mediastinum is horizontal plane to pass the sternal angle (Fig. 1-19).

 

Fig. 10-6. Anterior, middle, posterior mediastina (horizontal plane).

 

The middle mediastinum includes the heart, the big blood vessels such as ascending aorta, pulmonary trunk, superior vena cava (Fig. 10-9), and the roots of two lungs (Fig. 5-20).

 

 

Fig. 10-7.

 

Because the anterior mediastinum is very narrow, the heart is almost in contact with the body of sternum (Fig. 10-5). If you push the body of sternum hard, the heart will be compressed (Fig. 1-18).

 

 

Fig. 10-8.

 

The heart is located not only behind the body of sternum but also left-sided to it. In the heart, the apex is the inferior left vertex, where beating is palpable (Fig. 10-9).

 

Fig. 10-9. Heart with four chambers, big blood vessels.

 

Opposite to the apex, the base (not labeled in the above figure) is the superior border where the superior vena cava (Fig. 10-16), ascending aorta (Fig. 10-20), and pulmonary trunk (Fig. 10-17) are connected.

 

Fig. 10-10.

 

Human heart is composed of two atria and two ventricles unlike fish heart (Fig. 8-39).

 

Fig. 10-11.

 

During development, the heart is rotated along two axes (Fig. 10-9).

 

 

Fig. 10-12.

 

The ventricle requires thick wall, mainly composed of cardiac muscles.

 

 

Fig. 10-13.

 

A job of the left ventricle to supply blood to the brain against gravity is arduous (Fig. 10-32).

 

 

Fig. 10-14.

 

The mitral and tricuspid valves are closed together; at the same time, the aortic and pulmonary valves are opened together. Then the reverse situation happens.

 

 

Fig. 10-15.

 

Closing sound of the mitral and tricuspid valves is heard. Then that of the aortic and pulmonary valves is heard.

 

 

Fig. 10-16. Inside of right atrium with wall reflected.

 

The inside of the atria and ventricles are divided into smooth and rough areas. The smooth area conveys blood, while the rough area pumps blood. The smooth area of the right atrium is where the superior vena cava, inferior vena cava (Fig. 10-9), and coronary sinus (Fig. 10-22) open. The rough area possesses pectinate (meaning comb) muscles that are the cardiac muscles for pumping (Fig. 16-30).

 

10-17. Interior of right ventricle.

 

In the right ventricle, the smooth area is between the tricuspid valve and pulmonary valve (Fig. 10-14). The pulmonary valve is structurally complete like a venous valve (Fig. 10-73). However, the tricuspid valve is not; thus, its cusps may move into the right atrium when the right ventricle contracts (Fig. 10-13). In order to prevent blood from regurgitating, the tricuspid valve is held in place by the tendinous cords which arise from the papillary muscles.

In the right ventricle, the rough area includes the trabeculae carneae as well as the papillary muscles. They, formed by cardiac muscles, are equivalent to pectinate muscles in the right atrium (Fig. 10-16).

 

Fig. 10-18.

 

To put the pulmonary artery in detail, the pulmonary trunk bifurcates into the right and left pulmonary arteries for the right and left lungs (Fig. 5-20) (Fig. 10-9).

 

 

Fig. 10-19. Inside of left atrium with wall reflected.

The smooth area of the left atrium receives blood from four pulmonary veins (Fig. 5-20). Its rough area is equipped with the pectinate muscles too.

 

Fig. 10-20. Inside of left ventricle.

 

In the left ventricle, the smooth area is between the mitral and aortic valves. Since the word “left” has one less letter than the word “right,” the left mitral valve has one less cusp than the right tricuspid valve (Fig. 10-17).

The rough area of the left ventricle also contains the papillary muscles and the trabeculae carneae.

 

 

Fig. 10-21.

 

The first branch from the ascending aorta (Fig. 10-20) is the coronary artery (in fact, the right and left coronary arteries) (Fig. 10-22).

 

Fig. 10-22. Coronary arteries.

 

The right coronary artery passes between the right atrium and right ventricle. On the posterior side of heart, the right coronary artery gives off the posterior interventricular branch (Fig. 10-9).

On the other hand, left coronary artery divides into the anterior interventricular branch and the circumflex branch passing between the left atrium and left ventricle (Fig. 10-9).

 

Fig. 10-23.

 

The right coronary artery and the circumflex branch resemble a crown.

 

  

Fig. 10-24. Cardiac veins.

 

Blood supplied by the coronary arteries drains into the cardiac veins. The three cardiac veins are pretty different from the coronary arteries (Fig. 10-22). The destination of all three cardiac veins is the coronary sinus that empties into the right atrium (Fig. 10-16).

 

 

Fig. 10-25.

 

The heart has its own nerves that keep it beating (Fig. 6-33).

 

 

Fig. 10-26.

 

An electrocardiogram is a test that measures the electrical impulse of the sinuatrial node, atrioventricular node, and atrioventricular bundle. The impulse is depicted as a graph.

The first nerve, the sinuatrial node, makes an impulse by itself. The impulse induces the contraction of the two atria. The second nerve, the atrioventricular node relays the impulse to the atrioventricular bundle, so as to make the two ventricles contract (Fig. 10-12).

 

Fig. 10-27.

 

In the cardiac plexus influencing the sinuatrial node, the sympathetic nerve is from the sympathetic ganglia (Fig. 13-62); the parasympathetic nerve is from X (Fig. 13-63).

 

 

Fig. 10-28.

 

The sympathetic and parasympathetic impulses make the heart beat faster and slower, alternatively (Fig. 13-61).

 


< Artery >

 

Fig. 10-29. Main arteries.

 

The aorta coming from the left ventricle is as thick as a thumb. The four successive aortas are ascending aorta, aortic arch (Fig. 10-30), thoracic aorta (Fig. 10-49), and abdominal aorta (Fig. 10-52). The thoracic and abdominal aortae are together called descending aorta.

 

Fig. 10-30. Three branches from aortic arch.

 

From the aortic arch, the brachiocephalic trunk, left common carotid artery, and left subclavian artery branch off. Since the heart and aortic arch are deviated to the left side (Fig. 10-6), the right side needs the brachiocephalic trunk before branching into the right common carotid artery (Fig. 10-31) and right subclavian artery (Fig. 10-40).

 

 

Fig. 10-31. Bifurcation of common carotid artery.

 

In each side, the common carotid artery bifurcates into the external and internal carotid arteries. The bifurcation point’s pulse can be definitely noticed in front of the sternocleidomastoid muscle (Fig. 3-16).

 

Fig. 10-31a.

 

As another branch of the external carotid artery, the facial artery proceeds inside the mandible, and exits the mandible to approach the eye. The facial artery’s pulse is faintly palpable on the mandible’s inferior border.

 

Fig. 10-32. Anterior, middle, and posterior cerebral arteries.

 

The internal carotid artery enters the cranial cavity and divides into the anterior and middle cerebral arteries. Concurrently, the vertebral artery from the subclavian artery (Fig. 10-30) enters the cranial cavity through the foramen magnum (Fig. 13-77). The bilateral vertebral arteries meet and divide to form the basilar artery, cerebellar arteries, and posterior cerebral artery. The cerebral arteries make anastomoses (Fig. 10-48) to perfectly feed the precious cerebrum.

 

Fig. 10-33. Cerebral artery in subarachnoid space.

 

The cerebral artery is in the subarachnoid space (Fig. 13-43). If the cerebral artery is ruptured, subarachnoid hemorrhage will occur.

 

Fig. 10-34.

 

Unfortunately, the cerebral artery is easily plugged or ruptured.

 

Fig. 10-35.

 

The brain takes much blood pumped out from the heart. If breathing stops, deoxygenated blood flows throughout the entire body. Unlike other organs of the body, the brain cannot stand the deoxygenated state and is irreversibly damaged.

There are several branches of the external carotid artery that supply the head and neck outside the cranial cavity. The terminal branch, superficial temporal artery, can be palpated on the temporal muscle (Fig. 3-14).

 

 

Fig. 10-39. Subclavian artery.

 

We come back to the subclavian artery (Fig. 10-30). Behind the clavicle (Fig. 1-20), try to touch pulsation of the subclavian artery.

 

 

Fig. 10-40. Border of axillary artery (left) and axilla (right).

 

The most significant branch of the subclavian artery is the vertebral artery which ascends along the cervical vertebrae (Fig. 1-15) for the cranial cavity (Fig. 10-32).

The subclavian, axillary, and brachial arteries run in the neck, axilla, and arm, in sequence. The boundaries of the axillary artery are the lateral border of R1 and the inferior border of teres major (Fig. 3-42) which are also the boundaries of the axilla.

 

Fig. 10-41. Axillary artery.

 

The axillary artery’ pulse can be sensed by touching the lateral wall of axilla (Fig. 10-40).

 

Fig. 10-42.

 

The pulse of brachial artery can be detected at the medial side of the biceps brachii (Fig. 3-48).

 

Fig. 10-42a.

 

Pulse of the arteries not covered by the muscles or others can be easily palpated.

 

Fig. 10-43.

 

The palpable pulse of the brachial artery is used to measure the blood pressure. The blood pressure is usually expressed in unit of millimeters of mercury (mmHg).

 

Fig. 10-44. Bifurcation of brachial artery in cubital fossa.

 

In the cubital fossa anterior to the elbow joint, the brachial artery bifurcates into radial and ulnar arteries. The cubital fossa is equivalent with the popliteal fossa (Fig. 3-79).

 

Fig. 10-45. Radial artery palpable in wrist.

 

One can easily feel pulse of the radial artery between the flexor carpi radialis (Fig. 3-55) and the styloid process of radius (Fig. 1-23). The two reference structures are also palpable.

 

Fig. 10-46. Radial artery palpable in anatomical snuffbox.

 

When the thumb is hyperextended (Fig. 2-25), the tendons of two muscles become prominent. The depression between two tendons is called the anatomical snuffbox because the depression could be used to sniff finely powdered tobacco.

The radial artery (Fig. 10-45) passing the wrist joint is curved dorsally, so one can palpate the artery’ pulse in the anatomical snuffbox.

 

Fig. 10-47.

 

The ulnar artery’ pulse is palpable lateral to the flexor carpi ulnaris that is heading for the pisiform (Fig. 3-56).

 

  

Fig. 10-48. Arteries of hand.

 

In the hand, the ulnar artery encounters the radial artery twice to form double anastomoses (superficial and deep palmar arches). These anastomoses protect the important hand from necrosis. The blood circulation through the anastomosis is called collateral circulation.

 

Fig. 10-49. Intercostal arteries.

 

The thoracic aorta, continuation of the aortic arch (Fig. 10-29), gives off the posterior intercostal arteries to feed the intercostal muscles (Fig. 3-23). There are also the anterior intercostal arteries that anastomose with the posterior intercostal arteries.

 

Fig. 10-50.

 

Each intercostal artery is accompanied by the intercostal vein (Fig. 10-66) and intercostal nerve (Fig. 13-96).

 

Fig. 10-51.

 

The head and trunk of the man in above cartoon resemble the abdominal aorta, whereas his partner’s head and trunk resemble the inferior vena cava (Fig. 10-68). Their upper limbs are equivalent to the renal arteries and veins (Fig. 6-5), while their lower limbs are comparable to the common iliac arteries (Fig. 10-29) (Fig. 10-53) and veins.

 

Fig. 10-52. Branches of abdominal aorta.

 

Successively, the man’s nose is the celiac trunk, mouth is the superior mesenteric artery, and umbilicus is the inferior mesenteric artery. The celiac trunk, superior and inferior mesenteric arteries feed the gastrointestinal tract (Fig. 8-32) and other abdominal organs such as liver, spleen (Fig. 4-40).

 

Fig. 10-53. Iliac arteries.

 

Like the common carotid artery dividing into the internal and external carotid arteries (Fig. 10-31), the common iliac artery divides into the internal and external iliac arteries.

 

Fig. 10-54. Branches of internal iliac artery to pelvic cavity.

 

The internal iliac artery gives off many branches to supply the pelvic cavity, pelvic wall, and perineum (Fig. 1-35) with blood. The above figure does not show the branches to the pelvic wall and perineum.

Meanwhile, the inguinal ligament (Fig. 7-3) is the border between the external iliac artery and the femoral artery (Fig. 10-56).

 

Fig. 10-55.

 

Below the inguinal ligament (Fig. 7-3), the femoral nerve (Fig. 13-100), femoral artery (Fig. 10-56), and femoral vein exist. The intervening femoral artery’s pulse is readily palpable (Fig. 10-42a), so we can imagine the location of the nearby femoral nerve and vein in a living person.

 

Fig. 10-56. Femoral artery.

 

One remarkable branch of the femoral artery is the deep femoral artery like the deep brachial artery (Fig. 10-40). Through the adductor hiatus of the adductor magnus (Fig. 3-69), the femoral artery enters the “popliteal” fossa (Fig. 3-75) to become the “popliteal” artery.

 

Fig. 10-57. Division of popliteal artery.

 

In the popliteal fossa (Fig. 3-79) posterior to the knee joint (Fig. 2-37), the popliteal artery divides into the anterior and posterior tibial arteries. The anterior tibial artery passes the interosseous membrane (Fig. 3-83) to feed the anterior leg muscles; the posterior tibial artery feeds the posterior leg muscles; the fibular artery, a branch of the posterior tibial artery, feeds the lateral leg muscles (Fig. 3-76).

 

Fig. 10-58. Dorsal artery of foot.

 

The anterior tibial artery becomes the dorsal artery of foot once it passes the ankle joint (Fig. 1-48). Try to cautiously feel the pulse of your dorsal artery of foot. The artery bifurcates into the 1st dorsal metatarsal artery and the deep plantar artery.

 

Fig. 10-59. Lateral and medial plantar arteries.

 

The posterior tibial artery passes just posterior to the medial malleolus (Fig. 1-49), where the arterial pulse is easily touched. The artery soon divides into the lateral and medial plantar arteries. The deep plantar artery (Fig. 10-58) and the lateral plantar artery meet to form an anastomosis (plantar arch) like anastomosis in the hand (Fig. 10-48).

 


< Vein >

 

 

Fig. 10-60. Vein, different from artery.

 

The vein has have lower blood pressure and slow blood flow due to the following two reasons: First, the vein is farther from the pumping ventricle than the artery (Fig. 10-1). Second, the vein has thicker lumen than the corresponding artery because the vein has less smooth muscle in its wall; moreover, there are the accompanying veins (Fig. 10-65) and the additional cutaneous veins (Fig. 10-70) (Fig. 10-70a) (Fig. 10-74).

 

Fig. 10-61.

 

Even if the cutaneous veins (Fig. 10-60) are excluded, a vein is usually closer to the skin than the corresponding artery.

 

Fig. 10-62.

 

Usually, a tributary of vein and a branch of artery run along with each other (Fig. 10-61). The authors will only introduce the unusual veins that are not in companion with the arteries, and so have different patterns from the arteries. The cardiac veins are an example (Fig. 10-24).

 

Fig. 10-63. Dural venous sinuses.

 

The cerebral veins are dissimilar to the cerebral arteries (Fig. 10-32). Like the cerebrospinal fluid, the blood in the cerebral veins flows to the dural venous sinuses such as the superior sagittal sinus (Fig. 13-43). Above figure shows the direction of the blood flow in the dural venous sinuses. Eventually, all the blood gets into the internal jugular vein (Fig. 10-64).

 

Fig. 10-64. Tributaries of the superior vena cava.

 

On each side, the internal jugular vein meets the subclavian vein to form the brachiocephalic vein. The bilateral brachiocephalic veins join to become the superior vena cava (Fig. 10-9) (Fig. 10-16). The brachiocephalic veins differ from the brachiocephalic trunk that exists only on the right side (Fig. 10-30).

 

Fig. 10-65. Brachial veins as accompanying veins.

 

Unlike the single axillary vein, the double brachial veins surround the brachial artery (Fig. 10-40). Duplicated veins like these are called the accompanying veins (Fig. 10-60). The accompanying veins are commonly found in the upper and lower limbs since the quantity of venous return from bulky limb muscles is enormous.

 

Fig. 10-66. Azygos veins for posterior intercostal veins.

 

The posterior intercostal veins (Fig. 10-50) follow a different route from the posterior intercostal arteries, since there is no corresponding vein to the thoracic aorta (Fig. 10-49). An alternative route is the azygos vein which eventually empties blood into the superior vena cava (Fig. 10-64). The hemiazygos vein and accessory hemiazygos veins join the azygos vein.

 

  

Fig. 10-67.

 

From the viewpoint of the gastrointestinal tract, this portal vein is a vein leaving the capillary of the gastrointestinal tract (Fig. 4-45); however, from the viewpoint of the liver, it is an artery coming to the capillary of the liver. Therefore, the portal vein is both a vein and an artery.

However, it is named the portal “vein” because it has the features of a “vein”: thin wall, thick lumen, and lower blood pressure (Fig. 10-60).

 

Fig. 10-68. Hepatic veins.

 

Emptying blood in the liver into the inferior vena cava is accomplished by the three hepatic veins. The hepatic veins only exist inside the liver since the inferior vena cava is attached directly to the liver (Fig. 4-48).

 

Fig. 10-69.

 

The cutaneous veins in the subcutaneous tissue are easily visible through the skin (epidermis, dermis) (Fig. 15-18).

Fig. 10-70. External jugular vein.

 

In the neck, the anterior jugular vein is a tributary of the external jugular vein. The two veins are prominent in surface anatomy. The external jugular vein is a tributary of the subclavian vein (Fig. 10-64).

 

 

Fig. 10-70a. Cutaneous veins in upper limb.

 

The two main cutaneous veins of the upper limb are the cephalic and basilic veins that originate from the dorsal venous network of the hand. The two cutaneous veins anastomose via the median cubital vein in front of the cubital fossa (Fig. 10-44).

 

Fig. 10-71.

 

Drawing blood from or injecting drug into the blood stream are usually performed through the cutaneous veins of the upper limb.

The cephalic vein passes the deltopectoral triangle (Fig. 10-70a) and goes into the axillary vein. The basilic vein drains into the border between the brachial and axillary veins. Consequently, the axillary vein collects two Brachial and one Basilic (three Bs) veins (Fig. 10-65).

 

Fig. 10-72.

 

The dark red color of blood in the cutaneous veins appears bluish in living persons.

 

 

Fig. 10-73.

 

The cutaneous veins of the upper limb have the venous valves.

 

Fig. 10-74. Cutaneous veins in lower limb.

 

Cutaneous veins in the lower limb start with the dorsal venous arch which is homologous with the dorsal venous network of hand (Fig. 8-27) (Fig. 10-70a). From the arch, the great and small saphenous veins ascend.

The great saphenous vein passing anterior to the medial malleolus (Fig. 1-43) is observable in one’s foot. On the other hand, the small saphenous vein passes posterior to the lateral malleolus (Fig. 1-43). Eventually, the “great” saphenous vein reaches the femoral vein (which is a “great” vein on anterior side) (Fig. 10-55), whereas the “small” saphenous vein reaches the popliteal vein (which is a “small” vein on posterior side)

 

Fig. 10-75.

 

Unlike the saphenous vein, deep vein runs along deep artery; for instance, the femoral vein (as a deep vein) travels with the femoral artery (Fig. 10-56). Some blood in the saphenous vein flows to the deep vein through the perforating vein; this is a kind of anastomosis (Fig. 10-48). In fact, the “perforating” vein “perforate” the lower limb muscle (Fig. 3-65) (Fig. 3-76).

Venous valves are located in the saphenous and perforating veins like those in the upper limb (Fig. 10-73).

 


< Capillary >

 

Fig. 10-76.

Capillary is the thinnest blood vessel that makes up the microcirculation (Fig. 10-1).

 

 

Fig. 10-77.

 

Lumina of the entire capillaries is thicker than those of the arteries or veins.

 

 

Fig. 10-78.

 

Anastomosis also exists between the corresponding artery and vein. Autonomic nerve closes and opens the arteriovenous anastomosis to control the amount of blood supply in the capillaries of an individual organ.

 

 

Fig. 10-78a.

 

For instance, after dining, blood supply in the brain decreases; that in the gastrointestinal tract increases.

 

 

Fig. 10-79.

 

In the cold weather, blood supply of the skin is reduced (Fig. 15-18).



 

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