Breathing

and contract the chest (figs. 2.5 and 2.9). Two sets of these muscles, one under the other, act on the rib cage. The external intercostal muscles run between the ribs in the same direction as the most external sheet of abdominal muscles (figs. 2.7, 2.9, 3.11-13, and 8.8); they lift and expand the rib cage for inhalation, like the movement of an old-fashioned pump handle as it is lifted up from its resting position. The internal intercostal muscles run at right angles to the external layer; they pull the ribs closer together as well as down and in for exhalation (usually a forced exhalation). If >'ou place your hands on your chest with the fingers pointed down and medially (toward the midline of the body), this approximates the orientation of the external intercostal muscles, and if you place your hands on your chest with the fingers pointing up and medially, this approximates the orientation of the internal intercostal muscles (fig. 2.5). The external intercostal muscles do not always act concentrically to lift the rib cage; during quiet breathing they first thoracic first rib entrance to chest cavity sternum internai intercostal muscles run down and laterally costal cartilages for fifth, sixth, seventh, and eighth ribs on right side of chest

4th Rib Down

fifth rib internal intercostal muscles floating ribs: eleventh (tip) twelfth (tip)

costal cartilages for second, third, and fourth ribs on left side external intercostal muscles first lumbar vertebra lower border of rib cage to which respiratory diaphragm (not shown) attaches

Figure 2.5. Surface view of chest. The internal intercostal muscles are visible in front near the sternum where they are not overlain by the external interccistals, and they are also visible laterally where the external intercostals have been dissected away (between the fifth and sixth ribs). As a group, the external intercostal muscles lift the rib cage up and out to support inhalation, and the internal intercostal muscles pull it down and in to complete a full exhalation (from Morris).

fifth rib internal intercostal muscles floating ribs: eleventh (tip) twelfth (tip)

first lumbar vertebra first thoracic first rib costal cartilages for second, third, and fourth ribs on left side external intercostal muscles external intercostal muscles run down and medially internai intercostal muscles run down and laterally entrance to chest cavity sternum costal cartilages for fifth, sixth, seventh, and eighth ribs on right side of chest lower border of rib cage to which respiratory diaphragm (not shown) attaches

Figure 2.5. Surface view of chest. The internal intercostal muscles are visible in front near the sternum where they are not overlain by the external interccistals, and they are also visible laterally where the external intercostals have been dissected away (between the fifth and sixth ribs). As a group, the external intercostal muscles lift the rib cage up and out to support inhalation, and the internal intercostal muscles pull it down and in to complete a full exhalation (from Morris).

7<S ANATUMi Ot- HATHA VOCA

also act isometrically to keep the rib cage from collapsing inward when the respiratory diaphragm (see below) creates the vacuum that draws air into the lungs.

the abdominal muscles

In breathing, the abdominal muscles (figs. 3.11-13, 8.8, 8.11, and 8.13-14) function mainly in deep and forced exhalations, as when you try to blow up a balloon in one breath. For that task the muscles shorten concentrically, pressing the abdominal wall inward, which in turn pushes the abdominal organs up against the relaxed (or relaxing) diaphragm. In combination with the action of the internal intercostal muscles, this forcibly decreases the size of the chest cavity and pushes air out of the lungs. You can also feel the action of the abdominal muscles by pursing the lips and forcing the breath out through the tiny opening. In yoga the abdominal muscles are important for what yogis refer to as even breathing, and they are also key elements for many breathing exercises.

the anatomy of the diaphragm

Because the respiratory diaphragm is completely hidden inside the torso, most people have only a rudimentary notion of what it looks like or how it operates. The simplest way to describe it is to say that it is a domed sheet of combined muscle and tendon that spans the entire torso and separates the chest cavity from the abdominal cavity (figs. 2.6-9). Its rim is attached to the base of the rib cage and to the lumbar spine in the rear.

The diaphragm is shaped like an umbrella, or an upside-down cup, except that it is deeply indented to accommodate the vertebral column. It consists of a central tendon, a costal portion, and a crural portion. The central tendon forms the top surface of the dome, which floats there freely, attached only to the muscle fibers of the costal and crural portions of the diaphragm. It is thus the only "tendon" in the body which does not attach directly to the skeleton. The largest part of the diaphragm is its costal component, whose muscle fibers fan down from the central tendon and attach all around to the lower rim of the rib cage (figs. 2.7-9). The crural portion of the diaphragm consists of the right crus and left crus, which attach to the forward arch of the lumbar spine (figs. 2.7-8). These are separated from one another by the aorta as it passes from the thoracic cavity into the abdominal cavity. The architecture of the diaphragm thus permits it to move the central tendon of the dome, the base of the rib cage, the lumbar spine, or any combination of the three.

You can note the site of the costal attachment of the diaphragm by hooking your fingers under the rib cage and tracing its lower margin. It is high in front where it attaches to the sternum, and lower where you trace it laterally (to the

2 BREA-nmC TI

side), but you can't feel it behind because the deep back muscles are in the way. You can also occasionally feel the region where the crura (plural form) of the diaphragm attach to the lumbar vertebrae, especially in someone slender who is lying flat on the floor, because the lumbar region sometimes arches forward to within an inch or so of the surface of the abdominal wall. This vividly illustrates how far forwar d the diaphragm can be indented by the spinal column.

The diaphragm has to be one of the most interesting and complex muscles in the body. Because it is a thin sheet, its shape bears the impressions of its immediate surroundings—the rib cage, the heart and lungs, and the abdominal organs, and it is dependent on the existence and anatómica] arrangements of these structures for its function. The diaphragm's extensive relationship with trachea right phrenic nerve (white profile)

superior vena cava nght atrium right lung

Relation Heart Lungs

left clavicle (cut)

left phrenic nerve (white profile)

pulmonary arterial trunk left pleural cavity (thin white space)

left fifth rib left ventricle fibrous pericardium where it sits on top of diaphragm abdominal muscles (tranversus abdominis)

Figure 2.6. Front view of the chest, with the first six ribs, clavicles, and sternum cut away to reveal the internal organs, which include: the larynx, trachea, lungs and Pleural cavities; the heart great vessels (aorta, vena cava, pulmonary artery, and Pulmonary vein, not all shown), pericardial cavity, and fibrous pericardium; the upper front portion of the respiratory diaphragm; and the right and left phrenic nerves. The pleural cavities are represented by the thin white spaces between the ,u«igs and the body wall, and between the lungs and diaphragm (Sappey).

left clavicle (cut)

trachea left phrenic nerve (white profile)

right phrenic nerve (white profile)

superior vena cava nght atrium right lung pulmonary arterial trunk left pleural cavity (thin white space)

left fifth rib left ventricle pericardial cavity surrounding heart fibrous pericardium where it sits on top of diaphragm abdominal muscles (tranversus abdominis)

right ventncle right pleural cavity between nght lung and diaphragm right seventh rib, and costal cartilage

Figure 2.6. Front view of the chest, with the first six ribs, clavicles, and sternum cut away to reveal the internal organs, which include: the larynx, trachea, lungs and Pleural cavities; the heart great vessels (aorta, vena cava, pulmonary artery, and Pulmonary vein, not all shown), pericardial cavity, and fibrous pericardium; the upper front portion of the respiratory diaphragm; and the right and left phrenic nerves. The pleural cavities are represented by the thin white spaces between the ,u«igs and the body wall, and between the lungs and diaphragm (Sappey).

the chest wall is a case in point. Even though the costal portion of the diaphragm extends to the base of the rib cage, the lungs are never pulled that far inferiorly (toward the feet), and for much of its area the costal portion of the diaphragm is in direct contact with the inner surface of the rib cage, with only the potential space of the pleural cavity separating the two. This region into which the lungs never descend is called the zone of apposition (fig. 2.9); without its slippery interfaces, the outer surface of the diaphragm could not slide easily against the inner aspect of the rib cage, and the dome of the diaphragm could not move up and down smoothly when we breathe.

esophagus and its hiatus in the respiratory diaphragm aorta hiatus tor vena cava costal fibers of the diaphragm attaching to cartilage at the base of the sternum right crus of diaphragm three layers of abdominal muscles: external abdominal internal abdominal central tendon of diaphragm (right side)

Costal And Crural Diaphragm

left crus of diaphragm left quadratu?

lumborum muscle left psoas muscle transversus abdominis vertebra eleventh ril (floating)

Figure 2.7. A view of the respiratory diaphragm looking at its underneath side from below. It's like a rejected upside-down bowl that a potter pushed in on one side. The pushed-in place is the indentation for the vertebral column, and the bottom of the bowl contains hiatuses (openings) for the esophagus, aorta, and inferior vena cava. The central tendon of the diaphragm is represented by the large, lightly contrasted central arch. The muscle fibers of the diaphragm are disposed radially from the central tendon: the costal fibers attach to the base of the rib cage most of the way around (approaching the viewer in the third dimension); and the right and left crura attach to the lumbar vertebrae below (between and in front of the origins of the psoas muscles), (from Morris)

right crus of diaphragm costal fibers of the diaphragm attaching to the base of the rib cage on the left side left psoas muscle three layers of abdominal muscles: external abdominal internal abdominal transversus abdominis vertebra esophagus and its hiatus in the respiratory diaphragm central tendon of diaphragm (right side)

aorta lower border of cartilages left crus of diaphragm intercostal muscles:

and external eleventh ril (floating)

left quadratu?

lumborum muscle hiatus tor vena cava costal fibers of the diaphragm attaching to cartilage at the base of the sternum

Figure 2.7. A view of the respiratory diaphragm looking at its underneath side from below. It's like a rejected upside-down bowl that a potter pushed in on one side. The pushed-in place is the indentation for the vertebral column, and the bottom of the bowl contains hiatuses (openings) for the esophagus, aorta, and inferior vena cava. The central tendon of the diaphragm is represented by the large, lightly contrasted central arch. The muscle fibers of the diaphragm are disposed radially from the central tendon: the costal fibers attach to the base of the rib cage most of the way around (approaching the viewer in the third dimension); and the right and left crura attach to the lumbar vertebrae below (between and in front of the origins of the psoas muscles), (from Morris)

How To Get Perfect Abs

How To Get Perfect Abs

The Complete Guide To How to Get Perfect Abs is Here. While other books gear you towards buying a product or a service, this book actually tells you exactly what you need to do to get the abs of your dreams. Getting a six pack and looking good is easier than ever if you follow the instructions in this book. This book does not just tell you what workout machines to use, but how to think, what to eat, what not to eat and how to exercise to get the six pack abs that you have longed for but never thought that you would get.

Get My Free Ebook


Responses

  • Pentti
    What muscles are on front left side below rib cage?
    7 years ago
  • ELELETA
    How do the intercostal muscles run?
    7 years ago
  • yolanda
    Where is the twelfth rib?
    7 years ago

Post a comment