Sternum: Difference between revisions

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'''Original Editor''' - [[User:Vaibhav Panchal]
'''Original Editor''' - [[User:Grace Barla|Grace Barla]]


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== Description  ==
== Introduction ==
The sternum (Colored part of figure shown below) is a Sword like flat bone that forms the thoracic skeleton's anterior median section. (BD CHAURASIA:BD_Chaurasia’s_Human_Anatomy, Volume 1 - Upper Limb Thorax, 6th Edition.pdf (archive.org))
The sternum completes the anterior chest wall as the ventral breastplate. The sternum is a flat cancellous [[bone]] with a compact cortex, it is slightly convex anteriorly, with multiple indentations along its lateral borders (costal notches). <ref name=":2">Radiopedia Sternum Available:https://radiopaedia.org/articles/sternum?lang=gb (accessed 28.9.2022)</ref><ref name=":0">Chaurasia BD. [https://worldofmedicalsaviours.com/bd-chaurasia-human-anatomy-pdf/ Human anatomy]. CBS Publisher; 2004. 8th Edition. Vol.1. Pg 224.</ref><ref>Drake R, Vogl AW, Mitchell AW, Tibbitts R, Richardson P. [https://books.google.co.in/books?hl=en&lr=&id=Di_TDwAAQBAJ&oi=fnd&pg=PP1&dq=Drake+R,+Vogl+AW,+Mitchell+AW,+Tibbitts+R,+Richardson+P.+Gray%27s+Atlas+of+Anatomy+E-Book.+Elsevier+Health+Sciences%3B+2020+Feb+27.&ots=1nOpd5gfYs&sig=0cLBj-amKtlYqTF950sLqnxDexE&redir_esc=y#v=onepage&q&f=false Gray's Atlas of Anatomy E-Book]. Elsevier Health Sciences; 2020 Feb 27.</ref>
 
Length of the bone: 17 cm  {Size of sternum in males is longer than in females}
[[File:Sternum composition.png|center|thumb|150x150px|Figure: Sternum]]


=== Structure  ===
=== Structure  ===
The sternum has 3 anatomical parts:
[[File:Parts of sternum.jpg|alt=|thumb|Parts of sternum]]
 
The sternum develops as three distinct parts:
# Manubrium
# Body of the sternum
# Xiphoid process
 
 
'''1) Manubrium:'''
 
* Quadrilateral in shape.
* Thickest and Strongest part
* Surfaces:
** Anterior surface:Convex from side to side; concave from above downwards.
** Posterior Surface:Concave; it forms the anterior boundary of the superior mediastrernum.
 
* Borders:
** Superior border: Thick,rounded and concave
*** marked by the suprasternalnotch or jugular notch or interclavicular notch in the median part
*** The clavicular notch on each side
** Inferior border: It forms  the secondary cartilaginous joint with the body of the sternum.
*** The manubrium makes a slight angle with the body, convex forwards, called the sternal angle of Louis.
** Two lateral borders: It forms the primary cartilaginous joint with the first costal cartilage.
 
 
2) '''Body of the sternum''':
 
*  The body of the sternum is longer, narrower and thinner than the manubrium
* It is the widest close to its lower end opposite the articulation with the fifth costal cartilage.
*  Surfaces:
** Anterior surface: It is flat, directed forward and slightly upwards.
** Posterior surface: slightly concave.
** 2 lateral borders, upper end and lower end.
 
 
3) '''Xiphoid process:'''
 
* The smallest part of the sternum
* It is at first cartilaginous, but later in the adult, it becomes ossified near its upper end.
* It varies in shape: It May be bifid or perforated.
* Surfaces:  
** Anterior surface
** Posterior surface
** Lateral border


== Muscle attachments ==
# The manubrium is flat and four-sided, wider superiorly
'''Manubrium:'''
# The body is a flat rectangular bone that has facets on its lateral border for articulation with the [[ribs]]. It is: approximately 20 cm long; 3-4 cm wide; 1 cm thick
# The xiphoid process is a thin bony projection inferiorly


* Anterior surface:It gives origin on either side to:
They articulate via secondary cartilaginous joints via hyaline cartilage with a fibrocartilaginous intervening disc. <ref name=":2" />{{#ev:youtube|kxKoFcfDVYM|600}}
** The [[pectoralis major]]
== Function  ==
** The sternal head of the [[sternocleidomastoid]]
Changes in the position of the skeletal components of the chest wall cause the changes in the dimensions of the chest. Two very different types of motion of the ribs and sternum create these changes in diameter. 


* Posterior Surface: It gives origin to:
# Anteriorly, the ribs are connected to the sternum, which can be viewed as a handle on a mechanical water pump that is activated manually. The manubrium (the ‘‘handle’’) has little motion, so its upward and anterior excursion is relatively limited. The joint between the manubrium and the body of the sternum allows the body and the xiphoid process to have a greater anterior and cephalad excursion, which causes the lower ribs to move more cephalad and anterior than the upper ribs, resulting in a greater increase in diameter in the lower chest.
** The sternohyoid in the upper part
# The accessory [[Muscles of Respiration|muscles of inspiration]] cause these increases in thoracic diameter, which result in forced inspiration. Conversely, the accessory muscles of expiration cause the sternum to move downward and inward, decreasing these diameters and causing forced expiration<ref name=":1">Graeber GM, Nazim M. [https://www.sciencedirect.com/science/article/abs/pii/S154741270600106X The anatomy of the ribs and the sternum and their relationship to chest wall structure and function]. Thoracic surgery clinics. 2007 Nov 1;17(4):473-89.</ref>
** The sternothyroid in the lower part
{{#ev:youtube|dxEDGK4nAZM|600}}<ref>Medical Lecture. Learn Movement in respiration,Pump handle & Bucket handle movement.  Available from: https://www.youtube.com/watch?v=dxEDGK4nAZM [last accessed 11/28/2021]</ref>
** The lower part of this surface  is related to the arch of the [[aorta]].
== Articulations ==
** The upper half is related to the left brachiocephalic vein, the brachiocephalic artery, the left common carotid artery and the left subclavian artery.
** The lateral portion of this surface is related to the corresponding [[Lung Anatomy|lung]] and pleura.


* suprasternal notch:
# [[File:Rib Cage.jpg|right|frameless|500x300px]] Superiorly the manubrium attaches to the neck where the two deep layers of cervical investing fascia insert
** It gives attachment to the lower fibres of the interclavicular ligament
# The manubrium: articulates with the first rib (primary cartilaginous), clavicle (atypical synovial), and body of the sternum (secondary or primary cartilaginous joint).
** Two subdivisions of the investing layer of cervical fascia.
# The body: articulates with the second rib at the sternomanubrial angle and the 3rd to 7th rib and costal cartilages
# Inferiorly articulates with xiphisternal joint, a secondary cartilaginous joint (symphysis)
# Muscle attachments


* Clavicular notch:
[[File:Sternum muscle attachment.png|alt=|thumb|Sternum muscle attachment]]
** The clavicular notch articulates with the medial end of the [[Clavicula|clavicle]] to form the sternoclavicular joint.
** Margins of clavicular notch give attachment to the capsule of the corresponding sternoclavicular joint.


2) '''Body of the sternum''':
== Musculotendinous Attachments ==
Muscle attachments: [[sternocleidomastoid]], intercostal, [[pectoralis major]], sternohyoid, and sternothyroid muscles


* Anterior surface: It gives origin on either side to the [[Pectoralis major|pectoralis major muscles]]
Transversus thoracis muscle arises from the posterior surface of the body
* Posterior surface: Lower part of the posterior surface gives origin on either side to the sternocostalis muscle.
* Upper end: it forms a secondary cartilaginous joint with the manubrium at the sternal angle
* Lower end: It is narrow and forms a primary cartilaginous joint with the xiphisternum.


3) '''Xiphoid process:'''
The xiphisternum attaches to [[Linea Alba|linea alba]]<ref name=":2" />


* Anterior surface: it provides insertion to the medial fibres of the [[Rectus Abdominis|rectus abdminis]] and the aponeuroses of the abdomen's [[External Abdominal Oblique|external]] and [[Internal Abdominal Oblique|internal]] [[Abdominal Muscles|oblique muscles.]]
=== Blood and Nerve Supply ===
* Posterior surface: it gives origin to the [[Diaphragm Anatomy and Differential Diagnosis|diaphragm.]] It is related to the anterior surface of the liver.
* Lateral border: it gives attachment to the aponeuroses of the internal oblique and transversus abdominis muscles.
* Upper end: it forms a primary cartilaginous joint with the body of the sternum
* Lower end: It affords attachment to the linea alba.


== Clinical relevance  ==
# Arterial supply: nutrient branches from internal thoracic (mammary) artery; deep to the sternum is the internal thoracic artery laterally
# Venous drainage: tributaries of the internal thoracic veins, posterolateral to the sternum
# Nerve supply is via intercostal nerves which arise from the anterior rami of thoracic spinal nerves


# Bone marrow for examination is usually obtained by manubriosternal puncture. It is done in its upper half to prevent injury to the arch of the aorta, which lies behind its lower half.
== Clinical relevance ==
# The slight movement that takes place at the manubriosternal joint is essential for the direction of the [[Ribs|ribs.]]
# Funnel chest: The sternum is depressed.
# Pigeon chest: Forward projection of the sternum like the keel of the boat and the flattening of the chest wall on either side
# The sternum is protected from injury by attachment of elastic costal cartilages. Indirect violence may lead to fracture of the sternum.
# Ectopia Cordis: Non-fusion of the sternal plates causes this condition, in which the heart lies uncovered on the surface.
# Sternal foramina, bifid xiphoid processes are results of the partial fusion of the sternal plates.


== Resources ==
* The slight movements that take place at the manubriosternal joint are essential for movements of the ribs.
[https://medicostimes.com/bd-chaurasia-anatomy-pdf/ BD chaurasiya Human Anatomy Volume 1]
* In the anomaly called ‘funnel chest’, the sternum is depressed in another anomaly called ‘[[Pectus Carinatum (pigeon chest )|pigeon chest]]’, there is forward projection of the sternum like the keel of a boat, and flattening of the chest wall on either side.
* For cardiac surgery, the manubrium and/or body of sternum need to be splitted in midline and the incision is closed with stainless steel wires. See [[Sternal Precautions]]
* [[Sternal fracture]] are associated with severe blunt trauma to the chest, such as in a vehicular accident.
* [[Costochondritis]] is the most common cause of [[Sternal Pain - Different Causes|sternal pain]] and occurs when the cartilage between the sternum and ribs become inflammed and/ or irritated.
* Sternum pain is pain or discomfort in the area of the chest that contains the sternum and the cartilage connecting it to the ribs. See [[Sternal Pain - Different Causes]]


= References =
== References ==


<references />  
<references />  


[[Category:Anatomy]] [[Category:Bones]]
[[Category:Anatomy]] [[Category:Bones]]

Latest revision as of 12:23, 29 September 2022

Original Editor - Grace Barla

Top Contributors - Grace Barla, Kim Jackson, Vaibhav Panchal, Lucinda hampton and Vidya Acharya

Introduction[edit | edit source]

The sternum completes the anterior chest wall as the ventral breastplate. The sternum is a flat cancellous bone with a compact cortex, it is slightly convex anteriorly, with multiple indentations along its lateral borders (costal notches). [1][2][3]

Structure[edit | edit source]

Parts of sternum

The sternum develops as three distinct parts:

  1. The manubrium is flat and four-sided, wider superiorly
  2. The body is a flat rectangular bone that has facets on its lateral border for articulation with the ribs. It is: approximately 20 cm long; 3-4 cm wide; 1 cm thick
  3. The xiphoid process is a thin bony projection inferiorly

They articulate via secondary cartilaginous joints via hyaline cartilage with a fibrocartilaginous intervening disc. [1]

Function[edit | edit source]

Changes in the position of the skeletal components of the chest wall cause the changes in the dimensions of the chest. Two very different types of motion of the ribs and sternum create these changes in diameter.

  1. Anteriorly, the ribs are connected to the sternum, which can be viewed as a handle on a mechanical water pump that is activated manually. The manubrium (the ‘‘handle’’) has little motion, so its upward and anterior excursion is relatively limited. The joint between the manubrium and the body of the sternum allows the body and the xiphoid process to have a greater anterior and cephalad excursion, which causes the lower ribs to move more cephalad and anterior than the upper ribs, resulting in a greater increase in diameter in the lower chest.
  2. The accessory muscles of inspiration cause these increases in thoracic diameter, which result in forced inspiration. Conversely, the accessory muscles of expiration cause the sternum to move downward and inward, decreasing these diameters and causing forced expiration[4]

[5]

Articulations[edit | edit source]

  1. Rib Cage.jpg
    Superiorly the manubrium attaches to the neck where the two deep layers of cervical investing fascia insert
  2. The manubrium: articulates with the first rib (primary cartilaginous), clavicle (atypical synovial), and body of the sternum (secondary or primary cartilaginous joint).
  3. The body: articulates with the second rib at the sternomanubrial angle and the 3rd to 7th rib and costal cartilages
  4. Inferiorly articulates with xiphisternal joint, a secondary cartilaginous joint (symphysis)
  5. Muscle attachments
Sternum muscle attachment

Musculotendinous Attachments[edit | edit source]

Muscle attachments: sternocleidomastoid, intercostal, pectoralis major, sternohyoid, and sternothyroid muscles

Transversus thoracis muscle arises from the posterior surface of the body

The xiphisternum attaches to linea alba[1]

Blood and Nerve Supply[edit | edit source]

  1. Arterial supply: nutrient branches from internal thoracic (mammary) artery; deep to the sternum is the internal thoracic artery laterally
  2. Venous drainage: tributaries of the internal thoracic veins, posterolateral to the sternum
  3. Nerve supply is via intercostal nerves which arise from the anterior rami of thoracic spinal nerves

Clinical relevance[edit | edit source]

  • The slight movements that take place at the manubriosternal joint are essential for movements of the ribs.
  • In the anomaly called ‘funnel chest’, the sternum is depressed in another anomaly called ‘pigeon chest’, there is forward projection of the sternum like the keel of a boat, and flattening of the chest wall on either side.
  • For cardiac surgery, the manubrium and/or body of sternum need to be splitted in midline and the incision is closed with stainless steel wires. See Sternal Precautions
  • Sternal fracture are associated with severe blunt trauma to the chest, such as in a vehicular accident.
  • Costochondritis is the most common cause of sternal pain and occurs when the cartilage between the sternum and ribs become inflammed and/ or irritated.
  • Sternum pain is pain or discomfort in the area of the chest that contains the sternum and the cartilage connecting it to the ribs. See Sternal Pain - Different Causes

References[edit | edit source]

  1. ↑ 1.0 1.1 1.2 Radiopedia Sternum Available:https://radiopaedia.org/articles/sternum?lang=gb (accessed 28.9.2022)
  2. ↑ Chaurasia BD. Human anatomy. CBS Publisher; 2004. 8th Edition. Vol.1. Pg 224.
  3. ↑ Drake R, Vogl AW, Mitchell AW, Tibbitts R, Richardson P. Gray's Atlas of Anatomy E-Book. Elsevier Health Sciences; 2020 Feb 27.
  4. ↑ Graeber GM, Nazim M. The anatomy of the ribs and the sternum and their relationship to chest wall structure and function. Thoracic surgery clinics. 2007 Nov 1;17(4):473-89.
  5. ↑ Medical Lecture. Learn Movement in respiration,Pump handle & Bucket handle movement. Available from: https://www.youtube.com/watch?v=dxEDGK4nAZM [last accessed 11/28/2021]
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