Where is rib 1 located?

The rib cage is an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels.

The sternum, together known as the thoracic cage, is a semi-rigid bony and cartilaginous structure which surrounds the thoracic cavity and supports the shoulder girdle to form the core part of the human skeleton. A typical human thoracic cage consists of 12 pairs of ribs and the adjoining costal cartilages, the sternum (along with the manubrium and xiphoid process), and the 12 thoracic vertebrae articulating with the ribs. Together with the skin and associated fascia and muscles, the thoracic cage makes up the thoracic wall and provides attachments for extrinsic skeletal muscles of the neck, upper limbs, upper abdomen and back.

The rib cage intrinsically holds the muscles of respiration (diaphragm, intercostal muscles, etc.) that are crucial for active inhalation and forced exhalation, and therefore has a major ventilatory function in the respiratory system.

There are thirty-three vertebrae in the human vertebral column. The rib cage is associated with TH1−TH12. Ribs are described based on their location and connection with the sternum. All ribs are attached posteriorly to the thoracic vertebrae and are numbered accordingly one to twelve. Ribs that articulate directly with the sternum are called true ribs, whereas those that do not articulate directly are termed false ribs. The false ribs include the floating ribs (eleven and twelve) that are not attached to the sternum at all.

The terms true ribs and false ribs describe rib pairs that are directly or indirectly attached to the sternum respectively. The first seven rib pairs known as the fixed or vertebrosternal ribs are the true ribs (Latin: costae verae) as they connect directly to the sternum; the next five pairs (eighth to twelfth) are the false ribs (Latin: costae spuriae). The false ribs include both vertebrochondral ribs and vertebral ribs. There are three pairs of vertebrochondral ribs (eighth to tenth) that connect indirectly to the sternum via the costal cartilages of the ribs above them. Their elasticity allows rib cage movement for respiratory activity.

The phrase floating rib or vertebral rib (Latin: costae fluctuantes) refers to the two lowermost, the eleventh and twelfth rib pairs; so-called because they are attached only to the vertebrae–and not to the sternum or cartilage of the sternum. These ribs are relatively small and delicate, and include a cartilaginous tip.

The spaces between the ribs are known as intercostal spaces; they contain the intercostal muscles, and neurovascular bundles containing nerves, arteries, and veins.

Each rib consists of a head, neck, and a shaft. All ribs are attached posteriorly to the thoracic vertebrae. They are numbered to match the vertebrae they attach to – one to twelve, from top (T1) to bottom. The head of the rib is the end part closest to the vertebra with which it articulates. It is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two articulating regions. The upper region articulates with the inferior costal facet on the vertebra above, and the larger region articulates with the superior costal facet on the vertebra with the same number. The transverse process of a thoracic vertebra also articulates at the transverse costal facet with the tubercle of the rib of the same number. The crest gives attachment to the intra-articular ligament.

The neck of the rib is the flattened part that extends laterally from the head. The neck is about 3 cm long. Its anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough, to give attachment to the ligament of the neck. Its upper border presents a rough crest (crista colli costae) for the attachment of the anterior costotransverse ligament; its lower border is rounded.

On the posterior surface at the neck, is an eminence—the tubercle that consists of an articular and a non-articular portion. The articular portion is the lower and more medial of the two and presents a small, oval surface for articulation with the transverse costal facet on the end of the transverse process of the lower of the two vertebrae to which the head is connected. The non-articular portion is a rough elevation and affords attachment to the ligament of the tubercle. The tubercle is much more prominent in the upper ribs than in the lower ribs.

The angle of a rib (costal angle) may both refer to the bending part of it, and a prominent line in this area, a little in front of the tubercle. This line is directed downward and laterally; this gives attachment to a tendon of the iliocostalis muscle. At this point, the rib is bent in two directions, and at the same time twisted on its long axis.

The distance between the angle and the tubercle is progressively greater from the second to the tenth ribs. The area between the angle and the tubercle is rounded, rough, and irregular, and serves for the attachment of the longissimus dorsi muscle.

The first rib (the topmost one) is the most curved and usually the shortest of all the ribs; it is broad and flat, its surfaces looking upward and downward, and its borders inward and outward.

The head is small and rounded, and possesses only a single articular facet, for articulation with the body of the first thoracic vertebra. The neck is narrow and rounded. The tubercle, thick and prominent, is placed on the outer border. It bears a small facet for articulation with the transverse costal facet on the transverse process of T1. There is no angle, but at the tubercle, the rib is slightly bent, with the convexity upward, so that the head of the bone is directed downward. The upper surface of the body is marked by two shallow grooves, separated from each other by a slight ridge prolonged internally into a tubercle, the scalene tubercle, for the attachment of the anterior scalene; the anterior groove transmits the subclavian vein, the posterior the subclavian artery and the lowest trunk of the brachial plexus. Behind the posterior groove is a rough area for the attachment of the medial scalene. The under surface is smooth and without a costal groove. The outer border is convex, thick, and rounded, and at its posterior part gives attachment to the first digitation of the serratus anterior. The inner border is concave, thin, and sharp, and marked about its center by the scalene tubercle. The anterior extremity is larger and thicker than that of any of the other ribs.

The second rib is the second uppermost rib in humans or second most frontal in animals that walk on four limbs. In humans, the second rib is defined as a true rib since it connects with the sternum through the intervention of the costal cartilage anteriorly (at the front). Posteriorly, the second rib is connected with the vertebral column by the second thoracic vertebra. The second rib is much longer than the first rib, but has a very similar curvature. The non-articular portion of the tubercle is occasionally only feebly marked. The angle is slight and situated close to the tubercle. The body is not twisted so that both ends touch any plane surface upon which it may be laid; but there is a bend, with its convexity upward, similar to, though smaller than that found in the first rib. The body is not flattened horizontally like that of the first rib. Its external surface is convex, and looks upward and a little outward; near the middle of it is a rough eminence for the origin of the lower part of the first and the whole of the second digitation of the serratus anterior; behind and above this is attached the posterior scalene. The internal surface, smooth, and concave, is directed downward and a little inward: on its posterior part there is a short costal groove between the ridge of the internal surface of the rib and the inferior border. It protects the intercostal space containing the intercostal veins, intercostal arteries, and intercostal nerves.

The ninth rib has a frontal part at the same level as the first lumbar vertebra. This level is called the transpyloric plane, since the pylorus is also at this level.

The tenth rib attaches directly to the body of vertebra T10 instead of between vertebrae like the second through ninth ribs. Due to this direct attachment, vertebra T10 has a complete costal facet on its body.

The eleventh and twelfth ribs, the floating ribs, have a single articular facet on the head, which is of rather large size. They have no necks or tubercles, and are pointed at their anterior ends. The eleventh has a slight angle and a shallow costal groove, whereas the twelfth does not. The twelfth rib is much shorter than the eleventh rib, and only has a one articular facet.

The sternum is a long, flat bone that forms the front of the rib cage. The cartilages of the top seven ribs (the true ribs) join with the sternum at the sternocostal joints. The costal cartilage of the second rib articulates with the sternum at the sternal angle making it easy to locate.

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. 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 transversus thoracis muscle is innervated by one of the intercostal nerves and superiorly attaches at the posterior surface of the lower sternum. Its inferior attachment is the internal surface of costal cartilages two through six and works to depress the ribs.

Expansion of the rib cage in males is caused by the effects of testosterone during puberty. Thus, males generally have broad shoulders and expanded chests, allowing them to inhale more air to supply their muscles with oxygen.

Variations in the number of ribs occur. About 1 in 200–500 people have an additional cervical rib, and there is a female predominance. Intrathoracic supernumerary ribs are extremely rare. The rib remnant of the 7th cervical vertebra on one or both sides is occasionally replaced by a free extra rib called a cervical rib, which can mechanically interfere with the nerves (brachial plexus) going to the arm.

In several ethnic groups, most significantly the Japanese, the tenth rib is sometimes a floating rib, as it lacks a cartilaginous connection to the seventh rib.

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 the contraction of intercostal muscles lift the rib cage up and out.

Expansion of the thoracic cavity is driven in three planes; the vertical, the anteroposterior and the transverse. The vertical plane is extended by the help of the diaphragm contracting and the abdominal muscles relaxing to accommodate the downward pressure that is supplied to the abdominal viscera by the diaphragm contracting. A greater extension can be achieved by the diaphragm itself moving down, rather than simply the domes flattening. The second plane is the anteroposterior and this is expanded by a movement known as the 'pump handle'. The downward sloping nature of the upper ribs are as such because they enable this to occur. When the external intercostal muscles contract and lift the ribs, the upper ribs are able also to push the sternum up and out. This movement increases the anteroposterior diameter of the thoracic cavity, and hence aids breathing further. The third, transverse, plane is primarily expanded by the lower ribs (some say it is the 7th to 10th ribs in particular), with the diaphragm's central tendon acting as a fixed point. When the diaphragm contracts, the ribs are able to evert (meaning turn outwards or inside out) and produce what is known as the bucket handle movement, facilitated by gliding at the costovertebral joints. In this way, the transverse diameter is expanded and the lungs can fill.

The circumference of the normal adult human rib cage expands by 3 to 5 cm during inhalation.

Rib fractures are the most common injury to the rib cage. These most frequently affect the middle ribs. When several adjacent ribs incur two or more fractures each, this can result in a flail chest which is a life-threatening condition.

A dislocated rib can be painful and can be caused simply by coughing, or for example by trauma or lifting heavy weights.

One or more costal cartilages can become inflamed – a condition known as costochondritis; the resulting pain is similar to that of a heart attack.

Abnormalities of the rib cage include pectus excavatum ("sunken chest") and pectus carinatum ("pigeon chest"). A bifid rib is a bifurcated rib, split towards the sternal end, and usually just affecting one of the ribs of a pair. It is a congenital defect affecting about 1.2% of the population. It is often without symptoms though respiratory difficulties and other problems can arise.

Rib removal is the surgical removal of one or more ribs for therapeutic or cosmetic reasons.

Rib resection is the removal of part of a rib.

Since the early part of the 20th century, the ability of the human rib to regenerate itself has been appreciated. However, scientific reports demonstrating repair have been sporadic and anecdotal. Currently, this phenomenon is best taken advantage of by craniomaxillofacial surgeons, who use both cartilage and bone material from the rib for jaw, face, and ear reconstruction.

The perichondrium is a fibrous sheath of vascular connective tissue surrounding the rib cartilage, containing a source of progenitor stem cells required for rib regeneration.

The position of ribs can be permanently altered by a form of body modification called tightlacing, which uses a corset to compress and move the ribs.

The ribs, particularly their sternal ends, are used as a way of estimating age in forensic pathology due to their progressive ossification.

The number of ribs as 24 (12 pairs) was noted by the Flemish anatomist Vesalius in his key work of anatomy De humani corporis fabrica 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. However, thirteenth or “cervical rib” occurs in 1% of humans and this is more common in females than in males.

In herpetology, costal grooves refer to lateral indents along the integument of salamanders. The grooves run between the axilla to the groin. Each groove overlies the myotomal septa to mark the position of the internal rib.

Birds and reptiles have bony uncinate processes on their ribs that project caudally from the vertical section of each rib. These serve to attach sacral muscles and also aid in allowing greater inspiration. Crocodiles have cartilaginous uncinate processes.

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

The first rib is the most superior of the twelve ribs. It is an atypical rib and is an important anatomical landmark. It is one of the borders of the superior thoracic aperture.

When compared to a typical rib, the first rib is

It has two tubercles:

Arterial blood supply arises from the internal thoracic and superior intercostal arteries.

The first rib is innervated by the first intercostal nerve.

The first rib has several attachments which are listed below;

The first rib is often noted as the most difficult rib to palpate. To palpate the first rib, find the superior border of the upper trapezius muscle and then drop off it anteriorly and direct your palpatory pressure inferiorly against the first rib. Asking a patient to take in a deep breath will elevate the first rib up against your palpating fingers and make palpation easier

First Rib Assessment on hypomobility in Supine:

Assessing Rib Mobility - Lindgren's Test:

The first rib, in particular is involved in thoracic outlet syndrome and Pancoast tumour.

Thoracic Outlet Syndrome

The term ‘thoracic outlet syndrome’ describes compression of the neurovascular structures as they exit through the thoracic outlet (cervicothoracobrachial region). The thoracic outlet is marked by the anterior scalene muscle anteriorly, the middle scalene posteriorly, and the first rib inferiorly. The term ‘TOS’ does not specify the structure being compressed. TOS affects approximately 8% of the population and is 3-4 times as frequent In woman as in men between the age of 20 and 50 years. Females have less-developed muscles, a greater tendency for drooping shoulders owing to additional breast tissue, a narrowed thoracic outlet and an anatomical lower sternum, these factors change the angle between the scalene muscles and consequently cause a higher prevalence in women. Signs and symptoms of thoracic outlet syndrome vary from patient to patient due to the location of nerve and/or vessel involvement. Symptoms range from mild pain and sensory changes to limb threatening complications in severe cases.

Pancoast tumour

Or otherwise known as superior sulcus tumour, refers to a relatively uncommon situation where a primary bronchogenic carcinoma arises in the lung apex at the superior pulmonary sulcus and invades the surrounding soft tissues. Although classically superior sulcus tumours present with Pancoast syndrome, this is only the case in approximately 25% of cases. The missing element is usually Horner syndrome. The most common symptoms at presentation are chest and/or shoulder pain, with arm pain being also common. Weight loss is frequently present.

The first rib os also affect by pathology common to all ribs;

The first rib is the most superior of the twelve ribs. It is an atypical rib and is an important anatomical landmark. It is one of the borders of the superior thoracic aperture. The ribs form the main structure of the thoracic cage that protects the thoracic organs.

There is one last component of the axial skeleton we did not cover last lab: the thoracic cage, also called the rib cage. The thoracic cage surrounds and protects the heart and lungs in the thoracic cavity. It consists of the ribs, the sternum, and the thoracic vertebrae, to which the ribs articulate.

We examined the thoracic vertebrae last lab, so here we will only examine the ribs and sternum.

There are twelve pairs of ribs. The number is the same in both males and females. Each pair articulates with a different thoracic vertebra on the posterior side of the body. The most superior rib is designated rib 1 and it articulates with the T1 thoracic vertebrae. The rib below that is rib 2, and it connects to the T2 thoracic vertebra, and so on. Ten of the twelve ribs connect to strips of hyaline cartilage on the anterior side of the body. The cartilage strips are called costal cartilage (“costal” is the anatomical adjective that refers to the rib) and connect on their other end to the sternum.

On an individual rib, one end has various processes, facets, and bumps. This is the end that articulates with the vertebra. The other end is blunt and smooth. This is the end that connects to costal cartilage (unless it is a floating rib. See below.)

Ribs 1-7 are called the true ribs. Each true rib connects to its own strip of costal cartilage, which in turn connects to the sternum. Ribs 8-12 are called the false ribs. Ribs 8, 9, and 10 do connect to the sternum, but the costal cartilage of each of these ribs connects to the costal cartilage of the rib above it, rather than directly to the sternum. Ribs 11 and 12 do not have any costal cartilage connected to them at all, and in addition to being grouped in the false ribs, these two are also called floating ribs, to reflect that fact.

The sternum has three parts. The manubrium, at the superior end of the sternum, and wider than the rest of the bone, provides articulation points for the clavicles and for the costal cartilage extending from rib 1. The central, thin body provides articulation points for costal cartilage from ribs 2 through 7. The xiphoid process which hangs down at the inferior end of the process (“xiphoid” is from the Greek for sword), starts out as cartilage, and does not typically ossify into bone until an individual is about 40 years old.

As part of the bony thorax, the ribs protect the internal thoracic organs. They also have a role in ventilation; moving during chest expansion to enable lung inflation.

In this article, we shall look at the anatomy of the ribs  - their bony landmarks, articulations and clinical correlations.

There are two classifications of ribs - atypical and typical. The typical ribs have a generalised structure, while the atypical ribs have variations on this structure.

The typical rib consists of a head, neck and body:

The head is wedge shaped, and has two articular facets separated by a wedge of bone. One facet articulates with the numerically corresponding vertebra, and the other articulates with the vertebra above.

The neck contains no bony prominences, but simply connects the head with the body. Where the neck meets the body there is a roughed tubercle, with a facet for articulation with the transverse process of the corresponding vertebra.

The body, or shaft of the rib is flat and curved. The internal surface of the shaft has a groove for the neurovascular supply of the thorax, protecting the vessels and nerves from damage.

Ribs 1, 2, 10 11 and 12 can be described as 'atypical' - they have features that are not common to all the ribs.

Rib 1 is shorter and wider than the other ribs. It only has one facet on its head for articulation with its corresponding vertebra (there isn't a thoracic vertebra above it). The superior surface is marked by two grooves, which make way for the subclavian vessels.

Rib 2 is thinner and longer than rib 1, and has two articular facets on the head as normal. It has a roughened area on its upper surface, from which the serratus anterior muscle originates.

Rib 10 only has one facet - for articulation with its numerically corresponding vertebra.

Ribs 11 and 12 have no neck, and only contain one facet, which is for articulation with their corresponding vertebra.

The majority of the ribs have an anterior and posterior articulation.

All the twelve ribs articulate posteriorly with the vertebra of the spine. Each rib forms two joints:

The anterior attachment of the ribs vary:

Rib fractures most commonly occur in the middle ribs, as a consequence of crushing injuries or direct trauma. A common complication of a rib fracture is further soft tissue injury from the broken fragments. Structures most at risk of damage are the lungs, spleen or diaphragm.

If two or more fractures occur in two or more adjacent ribs, the affected area is no longer under control of the thoracic muscles. It displays a paradoxical movement during lung inflation and deflation. This condition is known as flail chest. It impairs full expansion of the ribcage, thus affecting the oxygen content of the blood. Flail chest is treated by fixing the affected ribs, preventing their paradoxical movement.

The first rib is the most superior of the twelve ribs. It is an atypical rib and is an important anatomical landmark. It is one of the borders of the superior thoracic aperture.

When compared to a typical rib, the first rib is

It has two tubercles:

Arterial blood supply arises from the internal thoracic and superior intercostal arteries.

The first rib is innervated by the first intercostal nerve.

The first rib has several attachments which are listed below;

The first rib is often noted as the most difficult rib to palpate. To palpate the first rib, find the superior border of the upper trapezius muscle and then drop off it anteriorly and direct your palpatory pressure inferiorly against the first rib. Asking a patient to take in a deep breath will elevate the first rib up against your palpating fingers and make palpation easier

First Rib Assessment on hypomobility in Supine:

Assessing Rib Mobility - Lindgren's Test:

The first rib, in particular is involved in thoracic outlet syndrome and Pancoast tumour.

Thoracic Outlet Syndrome

The term ‘thoracic outlet syndrome’ describes compression of the neurovascular structures as they exit through the thoracic outlet (cervicothoracobrachial region). The thoracic outlet is marked by the anterior scalene muscle anteriorly, the middle scalene posteriorly, and the first rib inferiorly. The term ‘TOS’ does not specify the structure being compressed. TOS affects approximately 8% of the population and is 3-4 times as frequent In woman as in men between the age of 20 and 50 years. Females have less-developed muscles, a greater tendency for drooping shoulders owing to additional breast tissue, a narrowed thoracic outlet and an anatomical lower sternum, these factors change the angle between the scalene muscles and consequently cause a higher prevalence in women. Signs and symptoms of thoracic outlet syndrome vary from patient to patient due to the location of nerve and/or vessel involvement. Symptoms range from mild pain and sensory changes to limb threatening complications in severe cases.

Pancoast tumour

Or otherwise known as superior sulcus tumour, refers to a relatively uncommon situation where a primary bronchogenic carcinoma arises in the lung apex at the superior pulmonary sulcus and invades the surrounding soft tissues. Although classically superior sulcus tumours present with Pancoast syndrome, this is only the case in approximately 25% of cases. The missing element is usually Horner syndrome. The most common symptoms at presentation are chest and/or shoulder pain, with arm pain being also common. Weight loss is frequently present.