Chapter 53

Cardiopulmonary Anatomyand Physiology

Objectives

1. Describe the gross and functional anatomy of

the heart and circulatory system.

2. Describe the gross and functional anatomy of

the respiratory system.

3. Describe the anatomy of the upper airway.

4. Describe the anatomy of the tracheobronchial

tree.

5. Discuss the relationship between the bony

elements of the thorax.

Objectives

6. Compare the roles of the diaphragm, accessory inspiratory muscles, and abdominal muscles.7. Discuss the pulmonary and bronchial circulations.8. Describe how breathing is controlled by the pons

and medulla.9. Describe innervation of the lungs.10. Describe the visceral pleura, parietal pleura, and

pleural space.

Objectives

11. Describe the anatomy of the mediastinum.

12. Describe the mucociliary apparatus.

13. Describe the smooth muscle function of the

airways and the pulmonary circulation.

14. Compare macrophages and dendritic cells

found within the respiratory system.

15. Compare alveolar type I and type II cells.

Objectives

16. Describe the interstitial space within the

lungs.

17. Describe the role of airway resistance and

respiratory system compliance on the

pressures generated during the respiratory

cycle.

18. Compare the distribution of ventilation and

blood flow within the lungs.

Objectives

19. Discuss the importance of the ventilation

perfusion ratio.

20. Describe oxygen uptake from the lungs.

21. State why diffusion capacity of the lungs is

evaluated.

The Heart

• The major function of the heart is to generate pressure that will propel blood through the lungs and the systemic circulation.

• The muscular structure consists of three parts:o Epicardium: a thin membrane that lines the outside of

the heart.o Myocardium: consists of cardiac muscle, serving as the

primary pumping function of the heart.o Endocardium: the innermost lining of the heart

composed of endothelial cells.

The Heart

• The heart is considered a single pump.• It functions as two pumps involving flow

through four chambers: the right atrium and ventricle and the left atrium and ventricle.

• The electrical conduction system of the heart consists of specialized cells and the major pacemaker of the heart is the sinoatrial (SA) node.

FIGURE 53–1 The heart and great vessels presented in a medial plane that slices the structures in half.

Circulatory System

• The circulatory system provides nutrients, particularly oxygen, to all of the cells in the body.

• The arterial system is a branching series of vessels that carries blood from the heart to the capillary beds and subsequently to the cells of the lungs and body.

Circulatory System

• Gross Anatomy of the Circulatory Systemo The heart muscleo Valves, chambers, and pressureso Arteries, veins, and capillarieso Conduction systemo Coronary circulationo Innervation

Circulatory System

• Arteries are thicker and flexible to withstand the higher pressures required to drive blood to and through major organs.

• Veins are thinner; their role is more passive as conduits for returning blood to the heart.

• The arterial system is vulnerable to disease as a result of consuming substances (high-cholesterol foods or cigarette smoke) that are associated with the formation of plaques on the inner walls of major arteries.

Circulatory System

• Arteries of the body tend to be deeper (see Figure 53-6).

• Normal arterial pressure is relatively uniform at about 120/80 mm Hg.

• Occlusions or strictures of the coronary arteries are extremely dangerous.

• The veins of the body tend to be near the surface of the skin and are more numerous than arteries (see Figure 53-7).

FIGURE 53–6 Arteries.

FIGURE 53–7 Veins.

Gross Anatomy of theRespiratory System

• The respiratory system can be divided into the upper and lower respiratory tracts.

• The upper respiratory system (tract) includes the nasal cavity, paranasal sinus, pharynx, tongue, epiglottis, soft and hard palates, oral cavities, laryngopharynx, and portions of the trachea.

• The lower respiratory tract extends from the trachea to the alveoli.

FIGURE 53–8

Anatomy of the upper

airway.

Anatomy of the Thorax

• The thorax contains an infrastructure composed of the chest wall and the vertebrae within which major organs reside.

• The chest wall (i.e., skin, ribs, intercostal muscles) protects the lungs from injury.

• Thoracic muscles such as the diaphragm perform the work of breathing.

Anatomy of the Thorax

• The thorax has three regions: o The mediastinumo A right pleural cavityo A left pleural cavity• The mediastinum contains major blood

vessels, the esophagus, and the heart. • The pleural cavities contain the lungs.

Anatomy of the Thorax

• The bony elements of the thorax include the:o Sternumo Ribso Thoracic vertebraeo Clavicleso Scapulae

Anatomy of the Thorax

• The diaphragm and external intercostals are the primary muscles of inspiration.

• During exhalation, the elastic recoil of the lungs and relaxation of the diaphragm allow the lungs to return to their end-expiratory volume and position.

• The diaphragm is a large muscle that provides the primary force for the work of breathing.

Anatomy of the Thorax

• Accessory muscles are coordinated with diaphragm movement during inspiration.

• The lungs are cone shaped, with a broad and concave base surrounded by the thoracic ribs and diaphragm.

• There are five lobes and 18 lung segments between the right and left lungs.

• See Table 53–1: Lobes and Segments of the Lungs.

Anatomy of the Thorax

• The lungs consist of two major anatomic divisions: the airways and the parenchyma.

• Within the lung parenchyma, adults have approximately 300 million alveoli.

• The lungs and their covering, the pleura, are well endowed with lymphatic circulation and lymph nodes.

Anatomy of the Thorax

• The lungs are well perfused, receiving nearly all of the cardiac output.

• The pulmonary arteries originate from the right ventricle and deliver deoxygenated blood to the lungs and the visceral pleura.

• Respiratory centers in the midbrain control ventilation in response to emotional, physical, and chemical changes or stimuli.

Anatomy of the Thorax

• The nerve supply of the lung involves all the organ’s components—the airways, parenchyma, and vasculature.

• Innervation of the Lungso Parasympathetic (cholinergic)o Sympathetic (adrenergic)

Anatomy of the Thorax

• Reflexes that influence breathing response include:

o Hering Breuer (inflation)o Irritanto Peripheral proprioceptoro Hypothalamic controlo Cortical controls

Anatomy of the Thorax

• Each lung is covered with a lining, the visceral pleura, which covers the surface of the lungs, extending into the fissures between the lobes.

• The chest wall is lined by the parietal pleura.• The pleural space is a cavity containing a

small amount of thin fluid.

Anatomy of the Thorax

• The fluid in the pleural space is vital in allowing frictionless sliding between the visceral and parietal pleurae.

• The mediastinum is the area between the two pleural sacs and all structures within the thorax, except the lungs and pleurae, are located in the mediastinum.

Microanatomy of theRespiratory System

• The main function of the lung is to provide adequate gas exchange.

• As air moves in and out of the lungs, gas exchange in the alveoli maintains adequate homeostasis in the body.

• Responses to foreign body inhalation can lead to respiratory compromise.

• The body reacts to these exposures by coughing, sneezing, bronchoconstriction, and increasing mucus production.

Microanatomy of theRespiratory System

• It is important for the mucociliary apparatus to maintain a fluid homeostasis.

• Mucociliary apparatus contains a mucous layer and cilia that move the mucous layer.

• Both the airways and pulmonary vasculature are lined with smooth muscle cells and smooth muscle control is involuntary.

Microanatomy of theRespiratory System

• Mast cells are cells that release mediators.• Dendrites are antigen presenting cells.• Macrophages are phagocytic cells.• Alveolar Cellso Type I: cover greatest surface areao Type II: produce surfactant• Absence of pulmonary surfactant can cause

collapse of the alveoli, resulting in atelectasis.

Microanatomy of theRespiratory System

• The pulmonary interstitium is the space between the alveolar epithelial and the endothelial cells lining the vasculature.

• The interstitium serves as mechanical support, containing various cell types associated with the maintenance of fluid balance in the lung.

• In pulmonary interstitial lung diseases there is an increase in the number of cells that reside in the interstitium increasing its thickness.

Functional Characteristics ofthe Respiratory System

• The major purpose of the lungs and the chest wall is to generate pressure gradients to allow air to flow into and from the lung.

• Two mechanical parameters, compliance and resistance, can be calculated when the pressure, volume, and flow characteristics of the respiratory system are known.

• Compliance is determined by measuring the change in lung volume divided by the corresponding change in pressure.

Functional Characteristics ofthe Respiratory System

• The resistance to airflow is associated with the size and patency of the airways as well as the relative turbulence of airflow.

• An inspired tidal volume is distributed to the conducting airways and alveoli.

• The volume of the conducting airways does not participate in gas exchange and is called dead space volume.

Functional Characteristics ofthe Respiratory System

• For optimal gas exchange, ventilation must be distributed to match perfusion throughout the lungs.

• Gas exchange in the lung depends not only on the distribution of ventilation but also on the distribution of pulmonary blood flow as well as whether ventilation and perfusion of various lung units are matched.

Functional Characteristics ofthe Respiratory System

• The ventilation-perfusion ratio ideally should be nearly equal to ensure the most effective gas exchange.

• Another factor that influences gas exchange is the time that a red blood cell (RBC) needs to transit the pulmonary capillary.