The Thoracic cage Anatomy.pptx

Dr. NDAYISABA CORNEILLE
CEO of CHG
MBChB,DCM,BCSIT,CCNA
Supported BY
THE THORACIC CAGE
ANATOMY

objective
• To describe the structure of the thorax, cutaneous
innervations of thorax (concept of the myotomes and
dermatomes) and of bony framework that forms part of
the thorax, and how it is adapted to their functions
• To define the thorax, rib cage and thoracic wall.
• To describe the structures that form the boundary of the
rib cage i.e ribs, sternum, vertebrae.
• To outline the clinical importance of the structures that
form the rib cage.
Dr Ndayisaba Corneille

Introduction
• The rib cage is a bony cartilaginous frame
work that has protects the heart, lungs and
other thoracic organs; provides attachment
for muscles and aids in respiration.
• It is flattened anteriorly and posteriorly but
rounded on the sides
• It is located in the thorax btn the neck and the
abdomen

Boundaries
• Anteriorly; the sternum and costal cartilages
• Posteriorly: the thoracic vertebrae
• Laterally: the ribs
• Superiorly: the thoracic inlet
• Inferiorly: the thoracic outlet

Sternum
• A flat bone located in the anterior part of the
rib cage. It is a midline bone
• Has three parts: manubrium sternum, the
body and the xiphoid process
• The manubrium sternum lies opposite T3 and
T4. It articulates with the first and second
ribs(synovial joints). Meets the body at the
sternal angle(angle of Luis), a
fibrocartilaginous joint.

• Body of the sternum: forms middle part of the
sternum
• Articulates with 2nd to 7th coastal cartilages
• Meets the manubrium at manubriosternal joint,
and xiphoid process at xiphisternal joint.(opposite
T9)
• Xiphoid process: forms lower part. Doesn’t
articulate with any ribs. Cartilaginous in young
individuals but ossifies at proximal end in the
elderly.
CLINICAL USES OF THE STERNUM
• Median thoracotomy
• Bone marrow biopsies

Congenital anomalies: Pectus carinatum
Anterior protrusion of the sternum – pigeon chest

A-Cup-shaped deformity B-Saucer-shaped C-Horns-of-steer
deformity

Anatomical happenings at sternal
angle
1) Lies btn manubrium sternum and body of the sternum
2) Lies btn T4 and T5
3) Its where the trachea ends
4) Its at the level of the second rib
5) At the level of ligamentum arteriosum
6) Its where the azygos vein drains into the SVC
7) Its where the ascending aorta ends and descending aorta
starts
8) Where the left recurrent laryngeal nerve curves around the
ligamentum arteriosum
9) separates the superior and inferior mediastinum

Ribs
• Long horizontal bones located in the thoracic
region
• Have a number of functions
• In man, main function is respiration, not so
important in protection. Thoracic organs equally
valunerable with or without ribs
• In snakes, locomotion(inside feet)
• In fish, protection against hydrostatic pressure
• Muscle attachment

CATEGORIZATION
ACCORDING TO
FEATURES
1. Typical ribs: 3rd-9th.
2. Atypical ribs: 1st, 2nd, 10th, 11th, and 12th.
The normal ribs have same general features, on the other hand the atypical
ribs have special features and thus can be discerned from the rest of the ribs.
ACCORDING TO
RELATIONSHIP
WITH THE
STERNUM
1. True ribs: lst-7th (i.e., upper 7 ribs).
2. False ribs: 8th-12th (i.e., lower 5 ribs).
True ribs articulate with the sternum anteriorly, on the other hand false ribs
don’t articulate with the sternum anteriorly.
ACCORDING TO
ARTICULATION
1. Vertebrosternal ribs: lst-7th.
The vertebrosternal ribs joint posteriorly with vertebrae and anteriorly with
the sternum.
2. Vertebrochondral ribs: 8th-10th.
The vertebrochondral ribs joint posteriorly with vertebrae and anteriorly
their cartilages join the cartilage of the higher rib.
3. Vertebral (floating) ribs: 11th and 12th.
The vertebral or floating ribs joint posteriorly with the vertebrae but their
anterior ends are free.Dr Ndayisaba Corneille

ARRANGEMENT AND GENERAL OUTLINE
The ribs are arranged one below the other and the gaps between the
adjacent ribs are termed intercostals spaces.
The length of ribs increases from 1st to 7th rib and after that slowly falls;
therefore, seventh rib is the longest rib
The transverse diameter of thorax increases progressively from 1st to
8th rib, thus 8th rib has the best lateral projection.
The ribs are arranged obliquely, i.e., their anterior ends be located at
lower level than their posterior ends.
The obliquity of ribs rises progressively from 1st to 9th rib, for this
reason 9th rib is most obliquely set.
The width of ribs slowly reduced from above downward.

Classification of ribs
12 pairs of ribs, classified in 2 ways
1) true and false ribs
2) typical and atypical ribs
True ribs: articulate with the sternum using their
own coastal cartilages, 1 to 7 true
False ribs: articulate with sternum using 7th coastal
cartilage. E.g 8,9 and 10
Floating ribs: don’t articulate with the sternum. 11
and 12

• Note: The 1st, 10th, 11th and 12th ribs have only
one articular facet on their heads for
articulation with the side of the body of the
corresponding vertebra.
• The tubercles of the 11th and 12th ribs make
no synovial joints with the respective
transverse processes, only being attached to it
by ligaments

Typical vs atypical
• Typical rib has the following features
1) A head with 2 articular facets, one for articulation
with the side of the body of the corresponding
vertebra and one for vertebra above
2) Neck, part below the head
3) Tubercle: an outer prominence for articulation with
transverse process of corresponding vertebra
4) Angle: most curved part or rib
5) Shaft: smooth superiorly, sharp inferiorly with a costal
groove for passage of intercostal vein, artery and
nerve. Anterior end of shaft articulates with coastal
cartilage

Typical ribs

• Atypical ribs: rib one atypical, shortest and
most curved rib, flattened superiorly and
inferiorly, has one facet on its head, has a
scalene tubercle on medial surface for
attachment of scalenous anterior muscle. Ant
to the tubercle is a groove for subclavian vein.
Post to the tubercle is a groove for the
subclavian artery and the brachial plexus.

Atypical ribs

Other atypical ribs
•2nd rib
•Tuberosity for serratus anterior on external
surface
•10th One facet
•11th and 12th One facet on head no neck or
tubercle

Clinical notes on ribs
1) Flail chest: result from fractures of many ribs
in more than one place. Part of chest is
sucked in during inspiration and sucked out
during expiration.
2) Rib grafts: can be used to replace mandible
following mandibulectomy
3) Rib contusion: secondary to trauma. Small
heamorrhage below peritoneum

Vertebrae
• Irregular bones found in the back
• Divided into different types: cervical 7, thoracic 12,
lumbar 5, sacral 5, coccygeal 4
• Each vertebra has a an anterior arch, and a posterior
body
• Btn the arch and body are seven processes namely
• One spine
• 2 transverse processes
• 2 superior articular facets
• 2 inferior articular facets

Features of thoracic vertebrae
• 12 in number
• Body medium sized and heart shaped
• Small circular vertebral foramen
• Long spine that is inclined downwards
• Have coastal facets on their transverse processes
for articulation with tubercles of the ribs
• Have articular facets on their bodies for
articulation with heads of the ribs.

JOINTS OF STERNUM
1. MANUBRIOSTERNAL JOINT:
.
.
cartilaginous joint, symphysis
between Manubrium and body of Sternum
2.
.
.
.
XIPHISTERNAL JOINT
cartilaginous joint
between Xiphoid process and body of Sternum
The Xiphoid process usually fuses with the body of the
Sternum during middle age

JOINTS OF RIBS
1. COSTOVERTEBRAL JOINTS:
2 joints between heads of the Ribs and bodies of
Vertebrae (corresponding and upper)- Synovial joints
1st, 10th, 11th 12th
and rib has 1 synovial joint with the
corresponding vertebra, the rest have 2 each; one for the
corresponding vertebra and the other for the vertebra
above it
1 joint between tubercle of Ribs and transverse
process of Vertebra (corresponding) - Synovial joint (1st-
10th Rib)
Intra articular ligament connects head of Rib to the
intervertebral disc

.,.,
,1.......-- body of ve
T4
ib ..... 1----
interver
head of rib
...
sternum
b
facet for tuberde of rib
' rtebra
·
r
.
lubercle of tebral disc
angle of rib
•
cross section of ri costal cartllago
costal groove

2.
.
COSTOCHONDRAL JOINTS:
Joints of the Ribs with costal cartilages
Cartilaginous joints
3.
.
.
.
STERNOCOSTAL JOINTS:
Joints between Sternum and costal cartilages
1st : Cartilaginous joint
2nd 10th
– : Synovial joints=
2nd-7th costal cartilages with Sternum
8th-10th costal cartilages with each other
(11th and 12th costal cartilages are embedded in muscles)

~ternal JOll'II
l~l
lnterchondral Joinfs -...!.--'---'--'

MOVEMENTS
1st
. Cartilaginous joints are immobile (thus rib and
all costochondral joints do not move during
respiration)
. Synovial joints are slightly mobile (due to
movements in both the joints between head,
tubercle and vertebrae, necks of Ribs rotate along
their axis, helping in raising and lowering of ribs
during respiration)

Intercoastal muscles
Arranged in three groups:
1) External intercoastals
2) Internal intercoastals
3) Transversus thoracis group of muscles:
Subcostales, Intercostales Intimi,
Sternocostalis

External intercostal muscles
• Fibers pass obliquely downwards and
forwards from the lower border of the rib
above to the upper border of the rib below.
• The muscle extends from the superior
costotransverse ligament at the back of the
intercostal space as far as the costo chondral
junction. Here it is replaced by the external
intercostal membrane that extends as far as
the sternum.

Internal intercoastal muscle
• The fibers run downwards and backwards
from the subcostal groove to the upper border
of the rib below.it is replaced posteriorly by
the internal intercoastal membrane which
extends from the angle of the rib to the
superior costal transverse ligament at the
posterior limit of the space.

Transversus thoracis
• Cross more than one intercostal space.
• Poorly developed.
• Action is depression of ribs

Anatomy of a typical intercostal space
• Composed of an intercoastal nerve, intercostal
arteries and interocstal veins.
• Each space contains
• 1 intercostal nerve
• One posterior and 2 anterior intercostal veins
• Corresponding intercostal arteries

Intercostal nerves
• Mixed nerve, emerges from intervertebral
foramen and enters intercostal space btn
internal intercostal muscle and transversus
thoracis gp
• Gives off a collateral branch that supplies
muscles in the particular space, the parietal
pleura and periosteum of ribs
• A lateral cutaneous branch that peirces
muscles to supply overlying skin

• An anterior terminal branch that pieces
muscles to reach the skin which it supplies
• The lower five intercostals and the subcostal
nerve slope downwards into the anterior
abdominal wall which they supply.

Intercostal arteries
Posterior intercostals:
• Upper two spaces supplied by superior
intercostal artery, branch of the costal cervical
trunk from 2nd part of subclavian.
• The remaining nine are branches of thoracic
aorta.
Anterior intercostals: upper 6 arise from
internal thoracic, lower 6 from musculophrenc
artery,branch of internal thoracic

Intercostal veins
• Correspond to arteries
• Each space has one posterior intercostal and 2
anterior intecostal veins
• Anterior intercostal veins drain into internal
thoracic and musculophrenic veins
• 1st superior intercostal drains into vertebral or
brachiocephalic, 2nd and 3rd to superior
intercostal, rest to azygos superior and inferior
hemiazygos veins

Thoracic inlet
• An oblique space btn the neck and thorax
• Allows entry of structures from the neck to the
thorax
Boundaries:
• Anteriorly: sternal notch
• Laterally: medial borders of first ribs
• Posteriorly: upper border of T1
The inlet is covered by the suprapleural membrane.

Thoracic inlet syndrome
• Presence of a cervical rib can compress on the
subclavian artery, vein and brachial plexus
• Patients present with ischeamic pain of the
upper limb due to blockage of blood supply.

Suprapleural membrane
• Dense fascial layer attached to the medial
border of the first rib and costal cartilage. Not
attached to neck of 1st rib.
• Posterior attachment is to C7
• Medially it is thin and fades out into the
mediastinal pleura.
• It is flat and lies in the oblique plane of the
thoracic inlet

• The cervical dome of pleura is attached to its
undersurface
• The subclavian vessels and related structures
run on its outersurface.
• Fxn: gives rigidity to the thoracic inlet
preventing distortion during respiratory
changes of intrathoracic pressure.

Thoracic outlet
• Located on the inferior aspect of the rib cage
• Lies btn the thorax and abdomen
• Boundaries
• Anteriorly: xiphoid process
• Posteriorly: T12
• Laterally: subcostal margin
• It is covered by the diaphragm that provides a
passage for structures from the abdomen to the
thorax and vice verser.

Diaphragm
• A thin sheet of muscle found diatal to the
lungs.
• Found only in placentalia.
• Composed of a peripheral muscle part and a
central tendon.
• Essential function is respiration.
• Composed of a right and left domes, the
former higher than the later due to larger size
of right lobe of the liver.

Origin:
• By means of right and left crura, and medial
and lateral arcuate ligaments.
• The right crus arises from L1, L2 and L3, plus
intervening intervetebral discs. Left crus arises
from L1 and L2 plus intervening intervertebral
disc.
• The medial arcuate ligament is a thickening of
fascia over psoas muscle

• It extends from the body of L2 to the
transverse process of L1, at the lateral margin
of psoas.
• The lateral arcuate ligament is a thickening of
fascia over quadratus lumborum.
• Insertion: in a central tendon. Shaped like a
rounded leaf, nearer to the front than the
back. Inseparable from fibrous pericardium.
Btn right and left leaves is caval arpeture

Action
• Respiration
• Forcefull expiration: sneezing and coughing
• Defeacation
• Urination
• Parturition
• Weight lifting
• Thoracoabdominal pump.
• Nerve supply: phrenic nerve.

CLINICAL CORRELATES
• ANOMALIES
• TRAUMATIC TEAR
• PARALYSIS

END
THANKS FOR LISTENING
By
DR NDAYISABA CORNEILLE
MBChB,DCM,BCSIT,CCNA
Contact us:
amentalhealths@gmail.com/
ndayicoll@gmail.com
whatsaps :+256772497591
/+250788958241

The Thoracic cage Anatomy.pptx

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