anatomy, lecture 3, the thoracic wall (lecture notes)

The Thoracic Wall 29-10-2010 By: Nada Nammas


The Thoracic Wall ……What is the thorax? … Where is it located in the body?


It’s the region located between the neck and the abdomen … its composed of many layers … first we have the skin … then the superficial fascia or (subcutaneous tissue)... then we have the deep fascia... Which covers the muscles, and muscles are attached to bones … and in between these structures we have blood vessels and nerves.

The function of the thoracic wall:

1. Protection of thoracic viscera.

2. Provides the mechanical function of breathing.


Usually when we study anatomy we start from the superficial to the deep but here we will start with the deepest part of the wall which is the skeletal part...


as you can see "slide 3" the skeletal part forms a cage and this cage is mainly composed of 12 pairs of ribs (a curved flat bones as you can see in the pic), they are attached to the manubrium and sterni " which is the anterior portion of this cage by the costal cartilages " and they are united posteriorly by the thoracic segments of the vertebral column which is 12 thoracic vertebrae.


Each rib is a flat curved bone, and this curve adds to it resilience... you know when we have a straight object and a force is applied to it the force will be concentrated... this curve decreases the stress and increases the resilience of bones and it forms a greater portion of the thoracic cage.

"Slide 4" we have 3 types of ribs:

1. True (1st – 7th)

2. False (8th – 10th)

3. Floating (11th & 12th)


Based on ….. ?!

Depending on how they are attached to the sternum … if they're attached by their own costal cartilages we call them true... & they are (1, 2, 3,4,5,6 and 7).

If they are attached through merging with the costal cartilage on top like the 10th 9th and 8th their costal

cartilages are merged together and then merging with the costal cartilage of the 7th so we call them false.

Or they don't make any attachment anteriorly like 11th and the 12th we call them floating they end up in the abdominal muscles "in kids we can actually feel those".


We have typical ribs and atypical " a: for negation (no typical)"

Typical ribs: they share common features...

They have a head which is a wedge-shaped so it's pointed, it has two articular facets {facet means a flat

surface}... It has a Neck which is a constriction that occurs just before the head...


We have a tubercle it's an elevation on the bone surface this tubercle has 2 parts:

1- Articulated part that articulates with something else.

2- Anda non-articulated part.

Then we have a Shaft (Body) which is the longest portion of the rib.

If we look at "slide 6" we can see a sharp curve in each rib we call it the angle. The top border is rounded it's not sharp, the inferior border is sharp and it over hangs ( حافه له ) , this is essential for housing the costal vein artery and nerve we call it the "costal groove".


So ribs from 3-9 are considered typical and they share these features … "slide 6" {tubercle has 2 numbers to indicate that we have Articular part and non-articular part}.

Let's talk about atypical ribs now:

They are special each has something that prevents us to say that it's typical …


The first rib: 1st … its flat, it's not rounded... it has a tubercle it's called a scalene tubercle... Whenever a muscle attaches to a bone there should be something there a process for this attachment,


And one of the neck muscles the scalenus muscle it attaches to the 1st rib, and it has a tubercle there,

So its exclusive for the 1st rib, also it (1st rib) has grooves for subclavian vein, "whenever blood vessels pass on top or under bones it leaves marks and this what we are talking about the grooves are marks for the subclavian artery".

The second rib 2nd which is also atypical it makes an attachment for the serratus anterior muscle.

The tenth rib 10th it has only one facet on the head {usually when we have a rib articulating with the vertebral column it will articulate with the corresponding vertebrae and the one on top of it so it will make articulation with


two vertebral bodies, so they have two facets}, but the tenth it has only one facet because it makes articulation with only the tenth vertebra.

Now:

11th and 12th they are different from the others, they are floating, with one facet on the head like the 10th because they just articulate with one vertebra and no neck or tubercle.

Slide # 8 is just to summary what we said about the 1st rib.


There are some people they are unlucky they have an extra rib we call it the Cervical Rib it articulates with the last cervical vertebra, why they are unlucky because this rib compress the nerves and blood vessels that pass on


top of the first rib


Q: can it be surgically removed?

A: yeah we can remove it.

Actually they make condition that happens almost in 1% of people, and the Complication as you can see when press on arteries the blood supply will be decreased to the muscle so we start having an ischemic pain, it is a visceral pain that we feel when there is lose of blood supply, it will also press on nerves so you will have Tingling sensations, and sometimes you will lose sensations in the respective area innervated by the compressed nerve, one of the treatments is to have the rib surgically removed.

So if u see slide # 10 the 1st rib is the flat one... and the cervical rib is clear on the left side.


Another medical condition related to the anatomy of the thoracic cage and it happens sometimes in violence

activity and accidents which is rib fractures most commonly the most affected the most prominent ones which are the middle ones {from 5 to10} and like anything else it will break at the weakest area which the angle it will Present as a sever localized pain, a serious complication that accompany the fracture is "pneumothorax" When the rib penetrates through the pleural cavity that surrounds the lungs and allows the air to enter that cavity ..


And this is serious because you can't empty your lungs as hard as you try to blow air out of your mouth, because your lungs are surrounded with negative pressure that keeps sucking air the negative pressure is the pressure within the pleural membrane if you tear this membrane and allow air to go inside you will lose this negative pressure and you might end up with a collapsed lung ore lung segment.

We talked about the ribs... because they make the major part of the thoracic cage.

Now we will talk about the thoracic vertebrae:


Slide #12 it’s the anatomical position we are looking from a superior view, the vertebra is composed of a body which is in the case of thoracic vertebrae is heart shaped, it's is also composed of the vertebral arch, or we call it the neural arch .. The neural arch is composed of two pedicles and two lamina... The bone between the body


and the transverse process we call it pedicle, the one between the transverse process and the spinous process we call it lamina... so two lamina and two pedicles they make the vertebral arch...

And it has 7 processes let's count them together :)

We have spinous process going posteriorly that’s usually very long and inclined inferiorly if we looked from a sagittal view we will see that...

We have two transverse processes, two superior articular facets, and two inferior articular facets.

Q: assume that a vertebra is t5 the superior articular facets what are they going to articulate with?


A: with t4 …

Q: which part of t4?

A: the inferior articular facets.

Once again …

Q: the inferior articular facets of t5 will articulate with what vertebra?

A: t6 …. The superior articular facets.


You should be able in the lab to distinguish between thoracic, lumbar, and cervical vertebrae.

The cervical vertebrae are very easy to be distinguished which has special features … they have two transverse foramina... these are only present in the cervical vertebrae.

Now if we look at the thoracic and the lumbar vertebrae you will see the spinous process in the thoracic is longer and inclined inferiorly, where as in the lumbar its very blunt, short, and straighter … it's not inclined inferiorly.


If you look at the arch you see that the vertebral arch looks like a part of a circle which center is in the middle of the vertebral body but in the lumbar it's something different.

It's time for the interior portion of the thoracic cage "w b3deen bet7ebo n9eer en6ale3 barah !! ele 7ka ah yetfadal :P "

The interior portion it’s a flat bone we call it the Manubrium sterni, the sternum which is composed of 3 parts:


The top part we call it the Manubrium sterni … the body … "slide 14" and here we have a piece of hyaline cartilage that gets ossified during age we call it the xiphoid process.

Slide 15 >> the Manubrium (1st part) it has several notches {and in the lab you should be able to determine them}, we have on top the Jugular notch, on the sides we have Clavicular notch {for articulation with the clavicle} … there is a part that articulates with the first rib >> first costal cartilage, and with part of the 2nd rib.


The joint between the manubrium and the body of the sternum we call it Manubriosternal Joint it’s a fibrocartilaginous joint, if we take a side view we notice that the manubrium and the body they are not on a straight line they make an angle we call it the sternal angle …this is important for clinicians when you need to make an injection in the thorax or you want to know where are you in the thorax?! You start counting the ribs from the angle; the angle opposes the second rib, so you pass your finger through the Jugular notch until you reach an elevation this is the angle and you move laterally then you start counting it’s the second rib …this angle is opposite to the t4 and t5 or the intervertebral disk between those two. This also something during your study


you need to pay attention to you have a structure and the position of this structure is related to the vertebral column you need to memories that.


The body of the sternum opposes t5 – t9 it has several notches here we call them the costal notches, its several costal notches corresponds to costal cartilage from 3rd- to 7th .

The last part the xiphoid process it opposes t10 ,

The joint the external joint it opposes t9 it a hyaline cartilage as we said and it gets ossified with age.

"Slide18" the cage has two openings or in anatomy apertures :

We have a superior aperture and an inferior aperture, the boundary for the superior one we have thoracic vertebra #1, the 1st rib, the costal cartilage, and the manubrium … the boundaries for the inferior


aperture {which we call the outlet} are t12, the 11th & the 12th ribs, and from 7-10 costal cartilages .. They make a great portion of the boundary plus the xiphisternal joint.

And if you notice this cage is inclined anteriorly so some of the structures inside this cage will appear through the superior aperture like the apex of the lung.

Thoracic Outlet Syndrome: (Costoclavicular syndrome)

Its where the blood vessels and the nerves are squeezed between the clavicle & 1st rib, usually the therapy for that is conservative physical therapy 50-90% of people they end up doing surgery to remove the 1st rib to relief this pain.


Please from your grand atlas study the thoracic wall for the lab the supervisor of the lab will not be walking with you telling you which is which most of the lab is self learning.


Good luck for all


It's just our spirits :P :P ((

Your sister: Nada Nammas.

anatomy, lecture 3, the thoracic wall (lecture notes)

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