By

DARE SAMUEL SUNDAY

Department of Human Anatomy, KABSOM
 The chest is Region between the neck and abdomen.
 Flattened in front & behind but rounded at the sides
 Framework is called thoracic cage

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 Covered on the outside by skin and muscles attaching the
shoulder girdle to the trunk.
 Lined with parietal pleural on the inside.

Walls
 Anteriorly: Sternum & costal cartilages

 Posteriorly: Thoracic part of vertebral column

 Laterally: Ribs & intercostal spaces

 Superiorly: Suprapleural membrane

 Inferiorly: Diaphragm

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 A flat bone in the midline of the anterior chest wall
 Divided into: manubrium sterni, body & xiphoid process
 Relatively shorter and thinner in the female

 Sternal angle (Angle of Louis): formed by articulation of the

manubrium with the body of the sternum

 Joints:
◦ Manubriosternal – level of disc btw T4 & T5
◦ Xiphisternal – opposite the body of T9
◦ Manubrium articulates with clavicle and 1st rib
◦ Body of sternum articulates with 2nd to 7th costal cartilages.

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 Sternum and Marrow Biopsy
Since the sternum possesses red hematopoietic marrow throughout
life, it is a common site for marrow biopsy.

 Under a local anesthetic, a wide-bore needle is introduced into the

marrow cavity through the anterior surface of the bone.

 The sternum may also be split at operation to allow the surgeon to

gain easy access to the heart, great vessels, and thymus.

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Consist of 12 pairs of bones that form the main part of the
thoracic cage

Structure:
 Typical rib: long twisted flatbone and has head, neck, tubercule
angle & body (e.g 3rd to 9th ribs)
 Atypical rib: are dissimilar (1st, 2nd, 10th, 11th & 12th ribs)

Classification:
 True ribs: are ribs attached to their costal cartilages
 False ribs: ribs 8th, 9th, 10th attached to costal cartilage of the 7th
rib.
 Floating ribs: 11th & 12th, has no attachment anteriorly.

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First Rib
 Is the broadest and shortest of the true ribs.

 Has a single articular facet on its head, which articulates with

the first thoracic vertebra.
 Has a scalene tubercle for the insertion of the anterior scalene
muscle and two grooves for the subclavian artery and vein.

Second Rib
 Has two articular facets on its head, which articulate with the
bodies of the first and second thoracic vertebrae.
 Is about twice as long as the first rib.

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Tenth Rib
 Has a single articular facet on its head, which articulates with
the 10th thoracic vertebra.

Eleventh and Twelfth Ribs

 Have a single articular facet on their heads.

 Have no neck or tubercle.

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 Joints of the Sternum
 Joints of the ribs
◦ Head
◦ Tubercules
◦ Costal cartilages
◦ Sternum

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Sternoclavicular Joint
 Saddle-type synovial joint with two separate synovial cavities

 Provides the only bony attachment between the appendicular

and axial skeletons.

Sternocostal (Sternochondral) Joints

 Articulates the sternum with the first seven cartilages.

 Articulation of manubrium with first costal cartilage is

synchondrosis (cartilaginous)
 Second to seventh costal cartilages form synovial plane joints
with the sternum.

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Costochondral Joints
 Articulation of ribs with their respective costal cartilages

 Are synchondroses.

Manubriosternal Joint
 Between manubrium and body of the sternum.

 Is symphysis (secondary cartilaginous joint)

Xiphisternal Joint
 Articulation between xiphoid process and body of the sternum
is synchondrosis

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Costovertebral Joints
 Synovial plane joints of heads of ribs with corresponding and
supraadjacent vertebral bodies.

Costotransverse Joint
 Synovial plane joint of tubercle of rib with transverse process
of corresponding vertebra.

Interchondral Joints
 Synovial plane joints between 6th and 10th costal cartilages of
ribs.

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Boundaries
 Anteriorly: Superior border
of manubrium sterni

 Posteriorly: First thoracic

verterbra

 Laterally: Medial border of

first ribs and their costal
cartilages

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 The Thoracic Outlet Syndrome
The brachial plexus of nerves (C5, 6, 7, and 8 and T1) and the
subclavian artery and vein are closely related to the upper
surface of the first rib and the clavicle as they enter the upper
limb.

 It is here that the nerves or blood vessels may be compressed

between the bones. Most of the symptoms are caused by
pressure on the lower trunk of the plexus producing pain down
the medial side of the forearm and hand and wasting of the
small muscles of the hand. Pressure on the blood vessels may
compromise the circulation of the upper limb.

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Muscle Origin Insertion Nerve Action
External Lower border of ribs Upper border of Intercostal Elevate ribs in
intercostals rib below inspiration
Internal Lower border of ribs Upper border of Intercostal Depress ribs (costal
intercostals rib below part);
elevate ribs
(interchondral
part)
Innermost Lower border of ribs Upper border of Intercostal Elevate ribs
intercostals rib below
Transversus Posterior surface of Inner surface of Intercostal Depresses ribs
thoracis lower sternum and costal
xiphoid cartilages 2–6
Subcostalis Inner surface of lower Upper borders of Intercostal Elevates ribs
ribs near their angles ribs 2 or
3 below
Levator Transverse processes Subjacent ribs Dorsal Elevates ribs
costarum of T7–T11 between primary
tubercle and angle rami
of C8–T11 16
 Spaces between the ribs
contaning:
◦ External intercostal muscle
◦ Internal intercostal muscle
◦ Innermost intercostal muscle
(*endothoracic fascia and
pleural)

◦ Neurovascular bundles:
Intercostal nerves and blood
vessels (VAN)

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 Structures penetrated by a needle when it passes from skin surface to
pleural cavity.
 Depending on the site of penetration, the pectoral muscles will be
pierced in addition to the serratus anterior muscle.

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 Skin
 Subcutaneous tissue
 Pectoral muscles
 Serratus anterior muscle
 External Intercostal muscle
 Anterior Intercostal membrane
 Internal Intercostal muscle
 Innermost Intercostal muscle
 Endothoracic fascia
 Parietal pleura

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 Intercostal arteries and Veins

Each intercostal space contains a large single posterior intercostal artery

(PIA) and two small anterior intercostal arteries (AIA).

◦ PIAs of intercostal space 1 & 2 are branches from superior

intercostal artery, a branch of the costocervical trunk of the
subclavian artery.

◦ PIAs arteries of the lower nine spaces are branches of the

descending thoracic aorta.

◦ AIAs of the first six spaces are branches of the internal

thoracic artery, which arises from the first part of the
subclavian artery.

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 AIAs of lower spaces are
branches of the
musculophrenic artery, one of
the terminal branches of the
internal thoracic artery

 Posterior intercostal veins

drain backward into the
azygos or hemiazygos veins,
and the anterior intercostal
veins drain forward into the
internal thoracic and
musculophrenic veins.

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Intercostal nerves

 Anterior rami of the first 11 thoracic spinal nerves.

 Anterior ramus of the 12th thoracic nerve lies in the abdomen

and runs forward in the abdominal wall as the subcostal nerve.

Note: The first six nerves are distributed within their intercostal
spaces.

o 7th to 9th intercostal nerves leave the anterior ends of their

intercostal spaces by passing deep to the costal cartilages,
to enter the anterior abdominal wall.

o The 10th and 11th nerves, since the corresponding ribs are
floating, pass directly into the abdominal wall
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Branches
• Rami communicates
• Collateral branch
• Anterior cutaneous branch
• Muscular branch
• Pleural sensory branches
• Peritoneal sensory branches

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 First intercostal nerve
◦ Joined to the brachial plexus by a large branch that is equivalent to
the lateral cutaneous branch of typical intercostal nerves.
◦ The remainder of the first intercostal nerve is small, and there is no
anterior cutaneous branch.

 Second intercostal nerve

◦ Is joined to the medial cutaneous nerve of the arm by a branch called
the intercostobrachial nerve
◦ supplies the skin of the armpit and the upper medial side of the arm.

 In coronary artery disease, pain is referred along this nerve to the

medial side of the arm

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 A thin muscular and tendinous septum that separates the chest
cavity above from the abdominal cavity below. It is pierced by
the structures that pass between the chest and the abdomen

 Parts of the origin

◦ Sternal part: from the posterior surface of the xiphoid
process.
◦ Costal part: from the deep surfaces of the lower six ribs and
their costal cartilages.
◦ Vertebral part: by vertical columns or crura and from the
arcuate ligaments.

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Branch of the first part of subclavian artery supplying the anterior
wall of the body from the clavicle to the umbilicus.

Branches
 2 anterior intercostal arteries (supply upper 6 ICS)

 Perforating arteries

 Pericardiacophrenic artery

 Superior epigastric artery

 Musculophrenic artery

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Internal Thoracic Vein
 Formed by the confluence of the superior epigastric and
musculophrenic veins,
 Ascends on the medial side of the artery

 Receives the upper six anterior intercostal and

pericardiacophrenic veins
 Ends in the brachiocephalic vein.

Thoracoepigastric Vein
 Is a venous connection between the lateral thoracic vein and the
superficial epigastric vein.

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Sternal or Parasternal (Internal Thoracic) Nodes
 Are placed along the internal thoracic artery.

 Receive lymph from the medial portion of the breast, intercostal spaces,
diaphragm, and supraumbilical region of the abdominal wall.
 Drain into the junction of the internal jugular and subclavian veins.

Intercostal Nodes
 Lie near the heads of the ribs.

 Receive lymph from the intercostal spaces and the pleura.

 Drain into the cisterna chyli or the thoracic duct.

Phrenic Nodes
 Lie on the thoracic surface of the diaphragm.

 Receive lymph from the pericardium, diaphragm, and liver.

 Drain into the sternal and posterior mediastinal nodes.

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 Suprasternal notch:
Is the superior margin of the manubrium sterni and is easily
felt between the prominent medial ends of the clavicles in the
midline. It lies opposite the lower border of the body of the
second thoracic vertebra.

 The sternal angle (angle of Louis):

Angle made between the manubrium and body of the sternum.
It lies opposite the intervertebral disc between the fourth and
fifth thoracic vertebrae.

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 Xiphisternal Joint:
is the joint between the xiphoid process of the sternum and the
body of the sternum. It lies opposite the body of the ninth
thoracic vertebra.

 The subcostal angle:

is situated at the inferior end of the sternum, between the
sternal attachments of the seventh costal cartilages.

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 Costal Margin
 Lower boundary of the thorax and is formed by the cartilages
of the 7th, 8th, 9th, and 10th ribs and the ends of the 11th and
12th cartilages.

 Lowest part of the costal margin is formed by the 10th rib and
lies at the level of the third lumbar vertebra (L3).

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 1. Clavicle
2. Suprasternal notch
3. Manubrium
4. Sternoclavicular joint
5. Body of sternum
6. Xiphisternum
7. Coracoid process
8. True ribs (1–7)
9. False ribs (8–10)
10. Costal cartilages
11. Costal margin

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 1. Clavicle
2. Ribs
3. Left dome of diaphragm
4. Right costophrenic angle
5 Right border of heart
6 Left border of heart
7 Pulmonary conus
8 Aortic knuckle

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 1. Midline sternotomy approach to
the mediastinum
2. Left anterolateral thoracotomy
through bed of fifth rib
3. Posterolateral thoracotomy
through bed of fourth rib
4. Thoraco-abdominal incision
5. Point for insertion of a needle
into ventricles
6. Point for insertion of a needle
into pericardial cavity for
emergency pericardiocentesis

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Anatomic and Physiologic Changes in the Thorax with Aging
 The rib cage becomes more rigid and loses its elasticity as the result
of calcification and even ossification of the costal cartilages.
 The stooped posture (kyphosis), so often seen in the old because of
degeneration of the intervertebral discs, decreases the chest capacity.
 Disuse atrophy of the thoracic and abdominal muscles can result in
poor respiratory movements.
 Degeneration of the elastic tissue in the lungs and bronchi results in
impairment of the movement of expiration.
 These changes, when severe, diminish the efficiency of respiratory
movements and impair the ability of the individual to withstand
respiratory disease.

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Read up the followings:
 Surface markings of the lungs and heart

 The pleural

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