lesson 4 thorax

human anatomy and embryology

what does the thorax consist of (4)

• a wall

• 2 pleural cavities

• the lungs

• the mediastinum

functions of the thorax (4)

• houses and protects the heart lungs and greater vessels

• allows structures to pass between neck and abdomen

• critical role in breathing

• support to the upper limbs

what skeletal elements and muscles does the thorax contain POSTERIORLY 

12 thoracic vertebra and their intervertebral discs 

what skeletal elements and muscles does the thorax contain LATERALY 

ribs (12 on each side) + muscles 

what skeletal elements and muscles does the thorax contain ANTERIORLY

sternum (manubrium, body and xiphoid process)

what is this

superior thoracic aperture

what is the superior thoracic aperture

• body of the T1

• the medial margin of  rib 1 

• manubrium of the sternum

the inferior thoracic aperture is what part of the rib cage 

the bottom        

inferior thoracic aperture contains what 

POSTERIOR (back rim)

• the body of the TXII (main part of 12th thoracic vertebra) 

• Rib XII and distal end of XI (floating ribs at the very bottom and attach to that TXII)

inferior thoracic aperture contains what 

ANTEROLATERAL 

(sides and front )

• Distal cartilaginous ends of ribs VII(7) to X(10)(fancy way of saying costal margins - the arch of cartilage)

• Xiphoid process ( points but at the bottom of the sternum)

• diaphragm

ribs Vii (7) and X (10) are 

false ribs 

what is the thoracic walls skeletal frame work

• thoracic vertebrae

• intervertebral discs 

• ribs 

• sternum 

how many sites of articulation to ribs a typical thoracic vertebra have

3

what facets are located o a typical thoracic vertebra

• 2 demifacets located

• oval facet 

what are demi facets

half facets

2 demi facets types

superior costal face and inferior costal facet

what does the superior costal facet articulate with

part of the head of its own rib

what does the inferior costal facet articulate with

part of the head of the rib bellow

what is the oval facet

transverse costal facet

where is the oval facet and what does it articulate with

at the end of the transverse process and articulates with the tubercle of its own rib

…… has a vertebra with demi facets on the body and facets on the transverse process 

thoracic vertebra 

what are the atypical thoracic vertebrae

• T1 

• TX

• TXI

• TXII

T1

complete superior costal facets on the body to articulate rib 1 

TX

lacks inferior demi-facets and articulates only with its own ribs

TXI and TXII

lack transverse costal facet

articulate only with the head of their own ribs 

how many pairs of ribs

12

how many pairs of true ribs

7

how many pairs of false ribs

5

what do the 7 true ribs articulate directly with

the sternum

what do the 5 pairs of false ribs articulate with

VII-X and XI and XII

• ribs VII-X articulate with the costal cartaliges of the ribs above 

• ribs XI and XII have no anterior connection with other ribs or sternum (floating ribs)

which ribs are floating ribs

XI

XII

do the flashcards of the ribs 

done 

the posterior end articulates with …

the vertebral column and is characterised by a head neck and tubercle

the head of the rib has two articular facets (+size)

inferior costal facet (larger )

superior costal facet (smaller)

what does the inferior costal facet articulate with

the superior costal facet on the body of its own corresponding vertebra (rib 5 with T5)

what does the superior costal facet articulate with 

the inferior costal facet on the vertebra above (rib 5 with T4) 

what happens at the crest between these 2 facets on a rib

intra-articular ligaments attach - locking rib head into place

the neck of the rib

short region of bone that separates head from the tubercle

the tubercle of the rib consists of 2 regions

• articular part 

• non-articular part 

in the tubercle what is the articular part 

is medial and has an oval facet for articulation with a corresponding facet on the transverse process of the associated vertebra 

in the tubercle what is the non articular part

• raised part

• roughened by ligament attachments 

shaft of the tubercle

• has internal and external surfaces

superior margin?

• superior margin = smooth and rounded

inferior margin?

• inferior margin = sharp, marked by a distinct costal groove

the manubrium of the sternum has on its superior surface

• jugular notch

the jugular notch on the manubrium has on either side

• on either side there is a large oval fossa for articulation with the clavicle

the jugular notch on the manubrium has underneath 

• facet for the attachment of the first costal cartilage (rib

1

articular site for clavicle 

2

jugular notch

3

manubrium of sterunm

4

sternal angle

5

attachment site of rib 1

6

articular demi facets for rib II

7

articular facets for rib III-VI

8

transverse ridges

9

body of sternum

10

articular facet for rib VII

11

xiphoid process

rib 1 articulates with sternum 

directly to the manubrium (full facet)

rib 2 articulates with sternum 

sternal angel (demifacets on both manubrium and body)

rib 3-6 articulates with the sternum

directly to the body ( full facets)

rib 7 articulates with the sternum

junction of Body and Xiphoid process (demi facets)

ribs 8-9 articulates with the sternum

false ribs - articulate with costal cartilage of the rib above not directly to the sternum 

ribs 11-12 articulates with the sternum

floating ribs - No

what are sternocostal joints and where 

articulation between costal cartilage of a rib and the sternum

upper 7 costa cartilages + sternum 

what are the 2 sternocostal joints

1. Fibrocartilaginous joint 

2. Synovial joint (2 compartments )

joint between rib 1 and sternum =

fibrocartilaginous joint 

joints between rib II through VII and sternum =

synovial joints

why are synovial joints in 2 compartments

because of intraarticular ligaments

interchondral joints

are articulations between the costal cartilages of adjacent ribs 

specially ribs 6-9 (sometimes 10)

what do the interchodral joints provide to the sternum

anchorage

what do interchondral joints form

inferior costal margin

what type of joint is an intercondral joint

synovial joint

Manubriosternal and xiphisternal joints are classified as

Symphysis (type of cartilaginous joint)

what is the manubriosternal joint

junction between the manubrium and the body of the sternum

what is the Xiphisternal joint 

junction between the body of the sternum and the xyphoid process

what happends to Xiphisternal joints wit age 

become ossified (fibrocartilage turns to bone - fusing the xiphoid process to the body of the sternum)

Manubriosternal and xiphisterna allow for

slight movement during respiration

the sternal angel passes through … ?

the intervertebral disc between TIV and TV

what is the intercostal space

space between 2 adjacent ribs (filled with muscles, nerves, and blood vessels)

1

serratus anterior muscle

2,3,4

2. external intercostal muscle

3. internal intercostal muscle 

4. innermost intercostal muscle 

5,6

5. skin 

6. superficial fascia 

7

lung

8,9,10

8. pleural cavity

9. visceral pleura

10. parietal pleura

11,12,13

11. intercostal vein

12. intercostal artery

13. intercostal nerve

14

collateral branches

15

endothoracic fascia

where are intercostal muscles found 

in each intercostal space (pass between adjacent ribs)

what do intercostal muscles do t the intercostal space

fill and support it

what are the types of intercostal muscles and how are they named

• external (closest to the skin (superficial))

• internal (in the middle (intermediate))

• innermost (furthest away from skin (deep))

primary function of external intercostal muscles and how 

• inspiration (breathing in)

• they contract 

• pulling ribcage up 

• increasing volume of the thorax 

primary function of internal intercostal muscles and how

• expiration (breathing out )

• rib cage moved down when they contract

• decreasing thoracic volume 

primary function of innermost intercostal muscles

• assists the internal intercostal with forced expiration 

where are the subcostal muscles and transversus thoracis muscles in relation to the internal and innermost intercostal muscles 

deeper 

Transversus Thoracis muscle is located

inner surface of the anterior thoracic wall

(deep to the sternum and costal cartilages)

function of Transversus Thoracis muscle

• depress costal cartilage

• when is contracts - it pulls costal cartilage downwards 

• contributes to forced expiration  

Subcostal muscle location

inner surface of the posterior thoracic wall

function of subcostal muscles

• depress the ribs

• contract it helps depress the ribs

• during forced expiration

1

serratus posterior superior