thorax anatomy
DESCRIPTION
A brief review of thorax anaotmyTRANSCRIPT
Slide 1
Thoracic wall
Skeleteon of thoracic wall
Ribs, costal cartilages and interocstal spaces
Thoracic vertebre
Sternum
Thoracic apertures
Superior thoracic aperture
Inferior thoracic aperture
Joints of thoraic wall
Costovertebral joints
Sternocostal joints
Movements of thoracic wall
Muscles of thoracic wall
Fascia of thoracic wall
Nerves of thoracic wall
Typical intercostal nerves
Atypical intercostal nerves
Vasculature of thoracic wall
Arteries of thoracic wall
Veins of thoracic wall
Breasts
Vasculator
Nerves of breast
Surface anatomy
Viscera of thoracic cavity
Pleurae, lungs and trahcobronchial tree
Pleurae
Lungs
Trachobronchial tree
Vasculator of lungs and pleura
Nerves of lungs and plearua
Mediastinum
Superior mediastnum
Inferior mediastnum
Posteiror mediastinum
Anteiror mediastnum
Thoracic wall
Structural function of thoracic cage. Because of its shape it allows us to: (protect, pressure, attachment)
Protect vital thoracic and abdominal organs form ext forces
Resist the negative sub atmospheric internal pressure generated by elastic recoil of lungs and inspiratory movements
Provide attachment for and support weight of upper limbs
Provide anchoring attachment of many of muscles for upper limb, muscles of abdomen, neck back and respiration
Flexibility of its joint + flexibility allow:
Absorb external blows and compression without fracture
Change shape for repsiraiton
Skeleton of thoracic walls
12 pairs of ribs + associated cartilages
12 thoracic vertebra + intervertebral disks in between
Sternum
Ribs, costal cartilages, intercostal spaces
Ribs:
Each rib has hematopoetic tissue. 3 types of ribs:
1-7 = true vertebrocostal ribs. Attach to sternum
8-10 = false vertebrochandral ribs. Connected to cartilage of rib above them. Connection to sternum is indirect
11,12 free verebral ribs
End in posterior abdominal musculature
Ribs:
Typical 3rd-9th
Atypical
Typical 3rd-9th
Head
Wedge shaped
2 facets sep by crest of head
1 facet for articulation with corrposneidng verbra
1 facet for vertebra superior to it
Neck
Connects the head of rib with body at level of tubercle
Tubercle
Located at junciton of neck and body.
2 articular parts:
Smooth articular part articulates with corresponding transverse process of vertebre
Rough non articular provides attachment for costotransevrse ligament
Body
Flat, curved, mostly markedly at costal angle
Demarcates the lateral limit of attachment for deep back mucles of ribs
Has the costal groove
Weakest part of rib is just anterior to its angle
Fractures of lower ribs may tear the diaphgram and reuslt in diaphragmatic hernia
Atypical ribs:
1st rib
a) broadest, shortest, most sharply curved of the seven true ribs
b) Single facet on head to articulate with T1 vertebra only
c) Two transversely directed grooves crossing its superior surface from subclavian vessels
d) Groovezs seperated by scalene tuercle and ridge, to which anterior scale muscles attach
Clinical:
Posterior inferior to clavicles
Rarely fracture because of protected position
You cannot palpate Rib 1
When broken structures crossting its superior aspect may be injured:
Brachial plexus of nerves
Subclavian vessels that serve uppe rlimb
Atypical ribs:
2nd rib
a)Thinner
b)less curved body
c)substantially longer than 1st rib
d)Head has two facets for articulation with bodies of T1 and T2 veretbrae
e)main atypical feature is a rought area on upper sraface, the tuberosity for serratus anterior, from which part the muscle originates
Atypical ribs:
10-12th ribs, like 1st rib, one fate on head. Articulate with single vertebra
11-12th ribs, short and have no neck or tubercle
Flail rib
Costal cartilages:
Function
1) length the ribs anteriorly
2) contribute to elasticity of thoracic walls
Costal cartilages 1-7:
Attach direct and independently to sternum
Costal cartilages 8,9,10th:
Articulate with costal cartilages superior to them- form a continuous articulate cartilaginous costal margin.
Costal cartilges 11,12:
Caps on anterior ends of corresponding ribs and do not reach or attach any other bone or cartialge
Clinical pearls:
The very young
Very elastic injury to thorax can be prsesent even in asbence of rib fracture
The eldelry:
Costal cartilges lose elastaicity under go calcification making them radiopaque
Intercostal spaces
11 intercostal spaces
11 intercostal nerves
Intercostal spaces occoupied by inctercostal muscles and membranes and two sets (main and ocllateral) of intercostal blood vessels and nerves
Space below 12th rib = rubcostal sapce = anterior ramus branch of spinal nerve T12
ICS is widest anterolaterlaly and widen further with inspiration
Can also be widd by extension/and or lateral flexion of thoracic verebtral column of contra lateral side.
Thoracic Vertebrae
Typical vertebra:
Independent
Have bodies, vertebral arches and seven processes for muscles and articular connections
Characteristics:
Bilateral costal facets (demifacets) on vertebral bodies for articulation with heads of ribs
Can be divided into superior and inferior costal facets small demifacets. Will be covere din more detail next slide
Costal facets on trasverse processes for articulation with tubercles of ribs
Exception: inferior 2 or 3 thoracic vertebrae
Long inferiorly slating spinous processes
Facets of typical ribs
Superior and inferior costal facets:
Occur as bilaterally paired, planar surfaces on superior and inferior posterolateral margins of bodies of typical thoracic vertebrae (T2-T9)
Arranged in pairs on adjacent vertebra, flanking an interposed IV disc:
Typically two demifacets paired in this manner and the posterolateral marign of IV disc between them form a single psocket to receive head of rib of the same number as superior rib
e.g Head of rib 6 with superior costal facet of vertebra T6
Exceptions to facets
Vertebra T1
Superior costal facets of T 1 are not demifacet because there are no demifacets on C7 vertebra above
Rib 1 only articulates with vertebre T1
T1 has a typical inerior costal demi facet
T10
Only one bilateral pair of costal facets located parlty on its body and partily on pedicle
T11,T12:
Only a single pair of costal facets located on pedicles
Sternum:
Manubrium:
Thickest, widest
Easily palpated concave center of superior border of manubrium - jugular nothc
Inferolateral to calvicular notch, there is the synchondrosis of first rib
Manibrium and body of sternum not in same plane.
Sternal angle
Body:
Longer, narrower
Located level of T5-T9
Younger people: 4 sternebrae are obvious. Articulat with each other at primary cartiligouns joints (sternal synchondrosis)
These joints fuse and form from inferior end between buperty and age 25.
Nearly flat anterior surface of body of stenrum is marked in adults by 3 veriable transverse reiddgs.
Xyhpoid process
Inferior end lies at level of T10 vertebre
Can be blunt
Can be biifid
Can be cuved
can be deflected to onside or other
Impt landmark:
a) junction with sternal body indicates inferior limit of central part of thoracic cavity
b) midle marker for the superior limit of liver, the central tendon of diaphgragm, infeiror border of heart
Describing costoverebtral joint i.e ribs to thoracic spine. 2 parts:
Joints of head and ribs:
Head of rib articulates with the following:
superior costal facet of corrosponding vertebre
Infeiror costal facet of vertebre superior to it
Adjacent iv disc uniting the two vertebrae
Head of ribs crest attached to IV disc by an intraarticular ligameent of head of rib wihtin joint, this divides the enclosed space into two synovical caivities
Fibrous layer of joint capsule:
Strongest anteriorly where it forms the radiate ligament of head of rib that found out form anterior marign of head of rib to sides of bodies of two vertebre and IV disc between them.
Very tight connection
Almost no movement
Costotransverse joint
Describing costoverebtral joint i.e ribs to thoracic spine. 2 parts:
Joints of head and ribs:
Costotransverse joint
Tubercle of rib with transverse process of vertebre of same number
Very little movement at these joints and only have thin capsules
Few ligmaents:
Strengthening the anterior part: Costotransvgerse ligament passing from neck of rib to transverse process
Strengethinging the posterior part Lateral costotransverse liagment passing form tubercle of rib to tip of transverse process.
Superior costcotransverse ligaement is a broad band that joins the crest of neck to rib to transverse process supieror to it:
Apertur ebetweeh this ligament and vrebtre permits passage of spinal nerve and posteiror branch of intercostal artery
Movement of thoracic wall
Changes from ribs 1-7 vs 8-10th
Upper ribs move in a pump handle movement
Lower ribs move in a buck handle movement
Pump handle:
Ribs 1-6
Very storng costcotransverse ligametns binding these joints and limiting their mogvements to slight gliding.
However, articualr surfaces on tubercles of superior 6 ribs are convex and fit into concatvities of the transverse process.
So rotaiton mostly at the transverse axis that transverses intrarticular ligamenet and head and neck of rib.
This results in elevation and depression movements of sternal ends of ribs and sternum in saggital plane
Bucket handle:
Ribs 7-10
Flat articular surfaces of tubercles and transverse processes of 7-10th ribs allow gliding allowing in elevation and dperssion of lateral most portions of these ribs
Sternal fractures
Not common any more thanks to airbags
Fracture of sternal body is usually a comminuted fracture (several pieces)
Displacement uncommon because :
Sternum invested by deep fascia (fibrous continuities of radiate sternocostal ligaments)
Sternal attachement of pectoralis major muscles.
Most common site of sternal fracture in eldelry people is at sternal angle i.e fusion of manubriosternal joint which results in dislocaiton of joint
Mortality 25-45% due to high likelhood of myocardial contusion, cardiac rupture, tamponade or lung injyr.
Even in cases of soft tissue sternal injjruy they should be eval for visceral injury.
Muscles of thoracic wall:
Axioappendicular muscles:
Pec major
Pec minor
Inferior part of serratus anterior
Scalene muscle
True muscles of thoracic wall:
Serratus posterior
Levatores costarum
Intercostal muscles
Subcostal muscles
Transverse muscles
Controversial role of serratous posterior
Perviously described as inspiratory muscles;
Serratous post sup was supposed to elevate the superior 4 ribs - thus increasing AP diamter of thorax and raising sternum
Serratous post inferior was supposed to depress the ifnerior irbs preventing from being pulled superiroly by diaphgram.
Recent studies show they do not have a primary motor function - important for prioperceptive fucniton -particualry serratus posterior sup has been implicated in chornic pain im yofascial pain syndrome
Some random points
External intecostal membranes are continous inferiorly with external oblique muscles in the anterolateral abdominal wall. More active during inspiration
Internal intercostal muscles most active during expiration
Innermost intercostal musces
Seperated from internal intercostals by intercostal nerves and vessel
External and internal intercostals
External active during inspiratoin
Internal expiration
Most activity is isometric increases tonus without producing movement mainly during forced respiration.
Main role is to support rigidity of intercostal space, resistent paradoxical movement espically during inspiration when intercostal thoracic pressures are lowst most negative
Clinical example:
High spinal cord injury initial flaccid paralysis of entire trunk but diaphgram remains active.
Here teh vatial capicty is markedly redcued by paraoxical incursion of thoracic wall during inspiration
When paralysis spastic thoracic wall stiffens and vital capicty rises
Nerves of thoracic wall
12 pairs of thoraic spinal nerves supply thoracic wal
Typical vs atypical intercostal nerves
As soon as they leave IV formina divided itno anterior and posterior rami or branches
Anterior
T1-T11 anterior rami forms the intercostal nerves which rund along extent of intercostal spaces
Anterior rami of Nerve T12 is the sucbostal nerve and is nefrior to 12th rib
Posterior:
Go lateral to the articular process of vertebre, to supply joints, deep back muscles and skin of back in thoracic region
Typical intercostal nerves:
Atypical intercostal nerves
Blood supply
Vertebre T6
gets tubercle of which rib?
Gets head of which rib
Tubercle of rib 6
Head of rib 6s inferior facet and rib 7s superior facet
33
Head of 6th rib articulates with?
Superior costal facet of body of T6 vertebrae
Inferio costalf acet of T6
IV disc between these verebtre
34
Very basic physiology
In healthy individuals, GFR remains stable despite changes in volume and blood pressure.
Overload
When overload of sodium and volume -> rise in atrial pressure -> release of natruietic peptides -> renal sodium secretion via direct ubular effects -> rise in GFR
RAAS is suppressed -> systemic vasodilatation and renal sodium excretion by inhibiting tubular effects of AGII and aldosterone
Volume depletion:
Increased RAAs -> systemic vasoconstrict and renal sodium absorption.
Angiotensin II induced renal effecert vasoconstriction, helping to maintain renal filling pressure and GFR despite decreased arterial pressure.
Interaction of cardiorenal system + osmoregulation
Normal physiological conditions-
High plasma osmolarity -> Release of arginine vasopresion (ADH) -> renal water retention -> Normal osmolarity
During pronounced water volume disturbances:
responses to volume depletion or overload can overcome osmotic triggers, contribute to restoration of volume status at expense of osmoregulation.
Basic mechanisms in play during AHF
Acute heart failure:
Decreased cardiac function -> Reduced CO + arterial underfilling -> decreased activation of arterial strech R -> compensatory systemic and intrarenal vasocnstriction
Decreased strech of glomeural afferent arteriole -> renin -> AGII
AGII -> afferent and efferent vasconstricion -> sodium retenion in proximal tuble + rls of aldosterone
Aldosterone -> increased sodium reabsorpiton in collecting duct -> ECF expansion and systemic congestion
Aldosterone escape mechanism
Protective effect of natruiretic peptides in AHF pt
Protective effect of natriuretic peptides is diminished in patients with AHF due to:
renal vasocontriction,
reduced sodium delivery,
fewer active formsof natriuretic peptides
and down reuglation of their receptors.
Decreased protective effect of natreretic peptides + adenisone
In addition, adenosine (which is released in reposnse to increased renal work load and high sodium concentration in distal tubule):
further reducedsrenal blood flow,
stimulates proximal sodium reabsorpaiton and through tubuloglomeural feedback futher decreased GFR via adenosine Areceptor.
In a typical heart failure patient kidneys get smashed
Pump failure
Neurohorminal activation
Usually on Ace I and ARB which overcome kideny`s capacity to comepnsate for reduced perfusion
Increased renal interstitium pressure + reduced transrenal perfusion
ANother hit to kindey:
increased vnous filling + abdo pressure ->
ascities -> increased renal afterload and intranreal pressure
reduce transrenal perfusion gardient
increased renal insteritum pressure (directly opposing pressure)
futher contirpute to renal insuff
Tx them with diuretics
Mechanisms of resistance
1) orally admin diuretics must be absorbed in gut - in presence of GI oedema or gut hypoperfusion, absorpiton of orally admin diuretics is impaired. IV admin can overcome impaired absorption.
2) Hypoalbuminemia:
Most diuretics are bound to plasma albumin:
thiazide diuretics
metolazone
acetazolamide
LOOP DIURETICS.
Hypoaluminemia common in ahf
Impairs uptake and secretionof active fursemide and enhances conversion to active form.
Coadmin of albumin and frusomide improved diuretic repsonse in patients with cirrhosis, nephrtic syndrome or chornic kindey disease but no date on hf.
3) Elevated BUN
reduces diuretic availaibility by competitively inhibiting the organic anion transporter
Furthermore, there is increased urea actively retains sodium itself.
This happens because RAAS and SNS lead to follow dependent passive resporation of urea in distal tubule; a concen trationg raident created by increasd sodium adn water resport in proximal tubule results in diminished distal aflow and increased reabsopriton.
How does it happen
1) Initially natriuretic effect results in intended negative sodium balance
2) Resulting decrease in ECF volume triggers a hoemostatic response (RAAS and SNS triggereD) increased sodium reteion at tubular sites
3) After several days, homeostatic resposne counterbalances diuretic effect fo drug creating a new steady state with lower Ecf
4) In patients with hyperaldosteronism, this phenomenon is pronouced cuasing rapid and abundand sodium reabsopriotn
5) Aslo you have hypertorphy of distal tubular cells due to rapid and abundant sodium reabsroption
Braking phenomenon appropriate homeostatic repsosne that prevents excessie volume depletion during continued diuretic therapy
Defn of diuretic resistance
Persistent congestion despite adequate adn eslcate doses of diuretics with > 80 mg lasix pre day
Amount of sodium excreted as a percentage of filtered load