Human rib cage

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Human rib cage
The human rib cage. (Source: Gray's Anatomy of the Human Body, 20th ed. 1918.)
Dorlands/Elsevier c_01/12204262

The human rib cage is a part of the human skeleton within the thoracic area. A typical human ribcage consists of 24 ribs, 12 on each side of the thoracic cavity, the sternum and the 12 thoracic vertebrae in both males and females.

Contents

[edit] Number of ribs

The number of ribs was noted by the Flemish anatomist Vesalius in 1543, setting off a wave of controversy, as it was traditionally assumed from the Biblical story of Adam and Eve that men's ribs would number one fewer than women's. (De humani corporis fabrica[1]) A small proportion of people have one pair more or fewer but this is unrelated to sex. Humans have seven rows of true ribs, each with its own connection to the sternum. Humans also have three rows of false ribs which connect to the ones above it. The last two rows, which don't connect to the sternum, are called floating ribs. In the front, the upper 7 ribs are attached to the sternum by means of costal cartilage. Due to their elasticity they allow movement when inhaling and exhaling. The 8th, 9th, and 10th ribs join with the costal cartilages of the ribs above. The 11th and 12th ribs are known as floating ribs, as they do not have any anterior connection.

[edit] Function

The Human rib cage is a component of the human respiratory system. It encloses the thoracic cavity, which contains the lungs. An inhalation is accomplished when the muscular diaphragm, at the floor of the thoracic cavity, contracts and flattens, while contraction of intercostal muscles lift the rib cage up and out. These actions produce an increase in volume, and a resulting partial vacuum, or negative pressure, in the thoracic cavity, resulting in atmospheric pressure pushing air into the lungs, inflating them. An exhalation results when the diaphragm and intercostal muscles relax, and elastic recoil of the rib cage and lungs expels the air.

[edit] Rib anatomy

The human rib parts:

  • The head is the end of a rib closest to the vertebral column.
  • The neck is the flattened portion which extends lateralward from the head.
  • The tubercle is an eminence on the posterior surface.
  • The angle is a bending part.
  • The Costal groove is a groove between the ridge of the internal surface of the rib and the inferior border.

[edit] Types of ribs

Anterior surface of sternum and costal cartilages.
Anterior surface of sternum and costal cartilages.
  • The first seven pairs of ribs are connected to the sternum in front and are known as true ribs or vertebrosternal ribs (costae verae, I-VII).
  • The eighth, ninth, and tenth attached in front to the cartilaginous portion of the next rib above and are known as false ribs or vertebrochondral ribs (costae spuriae, VIII-X).
  • The lower two, that is the eleventh and twelfth, are not attached in front and are called floating ribs or vertebral ribs (costae fluitantes, XI-XII).
  • In some humans, the rib remnant of the 7th cervical vertebra on one or both sides is replaced by a free extra rib called a cervical rib, which can cause problems in the nerves going to the arm.

The spaces between the ribs are known as intercostal spaces; they contain the intercostal muscles, nerves, and arteries. The rib cage allows for breathing due to its elasticity.

[edit] Atypical ribs

The atypical ribs are the 1st, 2nd, and 10th to 12th.

  • The first rib has a shaft that is wide and nearly horizontal, and has the sharpest curve of the seven true ribs. Its head has a single facet to articulate with the first thoracic vertebra (T1). It also has two grooves for the subclavian vessels, which are separated by the scalene tubercle.
  • The second rib is thinner, less curved, and longer than the first rib. It has two facets to articulate with T2 and T1, and a tubercle for muscles to attach to.
  • The 10th to 12th ribs have only one facet on their head; the 11th and 12th ribs are short with no necks or tubercles and terminate in the abdominal wall before fusing with the costal cartilages.

[edit] Medical conditions

  • Rib fractures can occur. These most frequently affect the middle ribs. When several ribs are injured, this can result in a flail chest.

[edit] Additional images

X-ray image of human chest, with ribs labeled.

[edit] See also

[edit] References

  1. ^ Chapter 19 On the Bones of the Thorax. Retrieved on 2007-08-23.
  • Clinically Oriented Anatomy, 4th ed. Keith L. Moore and Robert F. Dalley. pp. 62-64
  • Tortora GJ and Derrickson B. PRINCIPLES OF ANATOMY PHYSIOLOGY, 11th ED. John Wiley and Sons, 2006. ISBN-10: 0-471-68934-3
v • d • e
Bones of torso
Sternum
Rib
specific ribs (1, 2, 9, 10, 11, 12, false - 8-12, floating - 11-12) - parts (Angle, Tubercle, Costal groove, Neck, Head)
General vertebral structures
Cervical vertebrae
Thoracic vertebrae
T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12
costal facets (superior, inferior, transverse)
Lumbar vertebrae
Sacrum
v • d • e
Human anatomical features
Head
Skull · Forehead · Eye · Ear · Nose · Mouth · Tongue · Teeth · Jaw · Face · Cheek · Chin
Neck
Torso
Shoulders · Spine · Breast (Tail of Spence) · Chest · Ribcage · Abdomen · Navel
Sex organs (Clitoris · Vagina · Penis · Scrotum · Testicle) – Hip · Anus · Buttocks
Limbs
Arm · Elbow · Forearm · Wrist · Hand · Finger (Thumb · Index · Middle · Ring · Little) · Leg · Lap · Thigh · Knee · Calf · Heel · Ankle · Foot · Toe (Hallux)
Skin