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By the end of this section, you will be able to:
  • Discuss the components that make up the thoracic cage
  • Identify the parts of the sternum and define the sternal angle
  • Discuss the parts of a rib and rib classifications

The thoracic cage (rib cage) forms the thorax (chest) portion of the body. It consists of the 12 pairs of ribs with their costal cartilages and the sternum ( [link] ). The ribs are anchored posteriorly to the 12 thoracic vertebrae (T1–T12). The thoracic cage protects the heart and lungs.

Thoracic cage

This figure shows the skeletal structure of the rib cage. The left panel shows the anterior view of the sternum and the right panel shows the anterior panel of the sternum including the entire rib cage.
The thoracic cage is formed by the (a) sternum and (b) 12 pairs of ribs with their costal cartilages. The ribs are anchored posteriorly to the 12 thoracic vertebrae. The sternum consists of the manubrium, body, and xiphoid process. The ribs are classified as true ribs (1–7) and false ribs (8–12). The last two pairs of false ribs are also known as floating ribs (11–12).


The sternum is the elongated bony structure that anchors the anterior thoracic cage. It consists of three parts: the manubrium, body, and xiphoid process. The manubrium    is the wider, superior portion of the sternum. The top of the manubrium has a shallow, U-shaped border called the jugular (suprasternal) notch    . This can be easily felt at the anterior base of the neck, between the medial ends of the clavicles. The clavicular notch    is the shallow depression located on either side at the superior-lateral margins of the manubrium. This is the site of the sternoclavicular joint, between the sternum and clavicle. The first ribs also attach to the manubrium.

The elongated, central portion of the sternum is the body. The manubrium and body join together at the sternal angle    , so called because the junction between these two components is not flat, but forms a slight bend. The second rib attaches to the sternum at the sternal angle. Since the first rib is hidden behind the clavicle, the second rib is the highest rib that can be identified by palpation. Thus, the sternal angle and second rib are important landmarks for the identification and counting of the lower ribs. Ribs 3–7 attach to the sternal body.

The inferior tip of the sternum is the xiphoid process    . This small structure is cartilaginous early in life, but gradually becomes ossified starting during middle age.


Each rib is a curved, flattened bone that contributes to the wall of the thorax. The ribs articulate posteriorly with the T1–T12 thoracic vertebrae, and most attach anteriorly via their costal cartilages to the sternum. There are 12 pairs of ribs. The ribs are numbered 1–12 in accordance with the thoracic vertebrae.

Parts of a typical rib

The posterior end of a typical rib is called the head of the rib    (see [link] ). This region articulates primarily with the costal facet located on the body of the same numbered thoracic vertebra and to a lesser degree, with the costal facet located on the body of the next higher vertebra. Lateral to the head is the narrowed neck of the rib    . A small bump on the posterior rib surface is the tubercle of the rib    , which articulates with the facet located on the transverse process of the same numbered vertebra. The remainder of the rib is the body of the rib    (shaft). Just lateral to the tubercle is the angle of the rib    , the point at which the rib has its greatest degree of curvature. The angles of the ribs form the most posterior extent of the thoracic cage. In the anatomical position, the angles align with the medial border of the scapula. A shallow costal groove    for the passage of blood vessels and a nerve is found along the inferior margin of each rib.

Rib classifications

The bony ribs do not extend anteriorly completely around to the sternum. Instead, each rib ends in a costal cartilage    . These cartilages are made of hyaline cartilage and can extend for several inches. Most ribs are then attached, either directly or indirectly, to the sternum via their costal cartilage (see [link] ). The ribs are classified into three groups based on their relationship to the sternum.

Ribs 1–7 are classified as true ribs    (vertebrosternal ribs). The costal cartilage from each of these ribs attaches directly to the sternum. Ribs 8–12 are called false ribs    (vertebrochondral ribs). The costal cartilages from these ribs do not attach directly to the sternum. For ribs 8–10, the costal cartilages are attached to the cartilage of the next higher rib. Thus, the cartilage of rib 10 attaches to the cartilage of rib 9, rib 9 then attaches to rib 8, and rib 8 is attached to rib 7. The last two false ribs (11–12) are also called floating ribs    (vertebral ribs). These are short ribs that do not attach to the sternum at all. Instead, their small costal cartilages terminate within the musculature of the lateral abdominal wall.

Chapter review

The thoracic cage protects the heart and lungs. It is composed of 12 pairs of ribs with their costal cartilages and the sternum. The ribs are anchored posteriorly to the 12 thoracic vertebrae. The sternum consists of the manubrium, body, and xiphoid process. The manubrium and body are joined at the sternal angle, which is also the site for attachment of the second ribs.

Ribs are flattened, curved bones and are numbered 1–12. Posteriorly, the head of the rib articulates with the costal facets located on the bodies of thoracic vertebrae and the rib tubercle articulates with the facet located on the vertebral transverse process. The angle of the ribs forms the most posterior portion of the thoracic cage. The costal groove in the inferior margin of each rib carries blood vessels and a nerve. Anteriorly, each rib ends in a costal cartilage. True ribs (1–7) attach directly to the sternum via their costal cartilage. The false ribs (8–12) either attach to the sternum indirectly or not at all. Ribs 8–10 have their costal cartilages attached to the cartilage of the next higher rib. The floating ribs (11–12) are short and do not attach to the sternum or to another rib.

Questions & Answers

what is the function of liver, small and large intestine?
Michalis Reply
small interstine helps with chemical digestion and reabsorption of food. liver is very important for chemical digestion because it releases bile to break down the fats you eat. large interstine absorbs water and some vitamins from chyme (food from the stomach) before it returns to feces.
Mechanical digestion begins from your mouth. our mouth has enzymes which help us break down food and change it into bolus. chemical digestion begins in the stomach. our stomach produces "pepsin" which breaks down proteins. Chemically broken down food will be reabsorbed in the small interstine.
chemical digestion also begins in our mouth since there are enzymes
what is vestegeal organ
Adam Reply
it is related with ear
An organ that is no longer necessary or needed and has degraded. The appendix (an organ on the alimentary canal) is considered vestigial as it's use is minimal, only controlling colon bacteria.
what is the other name of a cell?
Songe Reply
describe mast cells?
draw the diagram of bone cell and label the parts?
what is a treatment of cuncer
Tumwine Reply
in some cases cancer is untreated ....it can be minimized by using medicines.... or by cutting the abnormal growth of the cancerous cells if possible
what is pulse & it's normal range of adult man & woman?
nayan Reply
Pulse is the heart beat The normal range is 60 - 90 beat in a minutes for adult
what is itching
Vincent Reply
what are the types of anatomy?
Aniphu Reply
gross or macroscopic and microscopic
if a person is visiting Denver CO why may they need to increase the rate of ventilation until they adapt?
Amy Reply
pressure changes between the atmosphere and thoracic cavity will change creating more ventilation. Also there is less pressure of Oxygen and hemoglobin already has less affinity for it than CO2 so there is less to bind than your body might be used to, increasing CO2 build up.
To compensate for the CO2 build up we breathe faster to make our blood less acidic. Eventually EPO will kick in build more RBC to compensate for the lower O2 concentration.
what is the fuction of tostiriol glands
abdifitah Reply
It's tonsilar?
or tostiriol
what are some examples of muscles predominantly composed of Fast glycolytic fibers?
Rey Reply
what is cardinal signs, and pathophysiology of those cardinal signs. can anyone explain..
Richard Reply
cardinal signs of inflammation!
then they are rubor,tumor,calor,dolar,functio laesa
rubor is redness due to vasodilatation
tumor is swelling due exudation of plasma
calor is rise in temperature
dolar is pain due to stimulation of nerve ending
functio laesa is loss of function
why are tha bp
Dharm Reply
Kya puchna chahate ho
wrong question
blood pressure
means diastolic 85 up
whats is the cell cycle
Dharm Reply
The cell cycle is the series of events that take place in a cell leading to its division and duplication of its DNA to produce two daughter cells
formation of bone in calcium
Dharm Reply
which is the largest or smallest muscle of human body?
pankaj Reply
largest muscle is sartoreus
smallest is pyramedalis muscle
largest is Gluteus maximus
smallest muscle stapedius
smallest muscle of our body
Stapedius muscle
stapedius muscle

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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