General Features And Attachments Of Typical Ribs & Atypical Ribs

DR. RASHIDA MEMON

General Features And Attachments Of Typical Ribs

Classification of Ribs  Twelve pairs of ribs, each terminating anteriorly in a

costal cartilage

Classification of RibsTrue Ribs: Costal cartilages of the upper seven ribs articulate

directly with the sternum, known as TRUE RIBS.

False Ribs: Costal cartilages lower five do not articulate directly to the sternum called as FALSE RIBS.

Floating ribs: Ribs 11th and 12th have no anterior connection with

other ribs or with the sternum

Costal Margin:

Costal cartilages of 8th to 10th ribs articulate anteriorly with costal cartilages of the ribs above, (like 8th articulates with 8th and so on) forming a continuous margin, Costal Margin.

Typical RibsThe Ribs 3rd to 9th or 10th have similar

features and called as TYPICAL RIBS

Consists of:Three parts :A curved shaft with anterior and posterior

ends. Anterior end is continuous with its costal

cartilage.Posterior end articulates with the vertebral

column and is characterized by a head, neck, and tubercle.

Head of RibHead is somewhat expanded. On its posterior end there are two articular

surfaces separated by crest. Smaller superior surface articulates with

inferior costal facet on body of vertebra aboveWhile larger inferior facet articulates with

superior costal facet of its own vertebra.

Neck of Rib Short flat region of bone. Separates the head from the tubercle.

Tubercle of ribProjects posteriorly from the junction of the

neck with the shaft.

Consists of two regions An articular part and A non-articular part.

1. Articular part: It is medial. Has an oval facet for articulation with a

corresponding facet on the transverse process of the associated vertebra

2. Non-articular part:Raised non-articular part is roughened by

ligament attachments.

Shaft of Rib Shaft is generally thin and flat.Has two borders.Two surfaces.

Borders: Upper Border Lower Border

Surfaces: Outer Surface Inner Surface  Superior margin is smooth and rounded, Inferior margin is sharp.Inferior margin of internal surface of shaft extends

beyond the limit of bone, called as costal groove.

Shaft of RibBeyond the tubercle the shaft of rib bends

on itself, known as costal angle. Along its long axis the shaft of ribs gently

twisted, this can be visible when rib placed on the table. This is helpful in respiration.

Attachments on Typical Ribs Provide attachment to intercostal muscles, Muscles between ribs

External Intercostal Muscles

Internal Intercostals Muscle

Innermost Intercostal Muscles

Innermost Intercostal Muscle

Transversus Thoracis

Subcostales

General Features and attachment of Atypical Ribs

Ribs having dissimilar features are the Atypical ribs.

These are 1st, 2nd, 10th, 11th and 12th.

1st Rib The 1st rib is: The broadest (i.e., Its body is widest and nearly

horizontal), Shortest, and Most sharply curved of the seven true ribs.Has a single facet on its head for articulation with

the t1 vertebra only.In comparison of typical rib the first rib has outer

and inner borders and superior and inferior surfaces

On its superior has two transversely directed grooves crossing for the subclavian vessels;

Grooves are separated by a scalene tubercle and ridge, to which the anterior scalene muscle is attached.

2nd Rib More typical Body is thinner, less curved, and

substantially longer than the 1st rib. Head has two facets for articulation with

the bodies of the T1 and T2 vertebraeMain atypical feature is a rough area on its

upper surface, The tuberosity for serratus anterior, from

which part of that muscle originates.

10th RibHead of rib tenth has a single facet for

articulation with its own vertebra.

11th & 12th Ribs 11 and 12 Ribs articulate only with the bodies of their own vertebrae and have no tubercles or necks.

Both ribs are short, have little curve, and are pointed anteriorly.

Anterior ends are free and covered with costal cartilages