respiratory and cardiovascular

sternum

three bones, from top to bottom:

• manubrium (jugular notch above this)

• body

• xiphoid process (xiphisternum)

ribs

• 12 pairs

• true ribes (1-7)

• flase ribs (8-10)

• floating ribs (11-12)

• all attach to vertebrae at the back (all thoracic)

true rib

direct attachment to sternum via on costal cartilage

false ribs

• indirect attachment via cartilage above (join up to the cartilage of other ribs)

floating ribs

no anterior attachment

costal margin

• formed by costal cartilages of ribs 7-10

• upside don v shape

• diaphragm attaches here

• boundary beteen thoracic cage and abdomen

• made of hyaline cartilage

thoracic vertebrae

• 12, joined together by intervertebral discs

• secondary fibrocartilaginous joints: hyaline on either side of the vertebral bodies and a disc in the middle

• thoracic vertebrae articulate with ribs to form thoracic cage stability

apertures in the sternum

• superior thoracic aperture (trachea and oesophagus pass through, arteries pass through)

• inferior thoracic aperture (sealed by diaphragm, but diaphragm has holes)

intercostal spaces

• gaps beteen the ribs

costal cartilage

hyaline cartilage that joins ribs to sternum

typical ribs

• 3-9

• head

• neck

• tubercle

• shaft (body)

atypical ribs

• 1, 2, 10-12

• modified shape or articulation based on function

head of a rib

articulates ith the thoracic vertebra

tubercle

• bump close to the thoracic vertebrae

• articular part: facet for transverse process of corresponding vertebra

• non-articular part: attachment for costotransverse ligament

• joint important for breathing

costal groove

• groove in the inferior side of the shaft

• vein, artery and nerve run through here on the inner surface of the bone

clinical applications of the costal groove

• fluid sometimes pools in the lung, have to be careful here the aspirator needle goes to avoid the vein, artery and nerve here, clinicians ill alays put the needle at the top of the rib

head

• edge shaped

• to articular facets:

  • superior facet —> vertebra above

  • inferior facet —> corresponding vertebra

• middle of the head joins to the disc

neck

narro region beteen head and tubercle

shaft

• long, curved main portion of rib

costal angle

• point of greatest curvature of the shaft

thoracic vertebrae

• vertebral body

  • heart shaped

  • to costal demifacets

• transverse processes

  • contain a transverse costal facet

  • articulate ith tubercle of corresponding rib

• spinous process points don

costal demifacets

• articulate ith head of a typical rib

• inferior and superior, join to to different ribs

hy does the transverse process of the thoracic vertebrae point don?

• rotation alloed

• bending backards is restricted to avoid compression of lungs and heart

joints of the thoracic cage

• sternal joints

• sternocostal joints

• costochondral joints

• interchondral joints

• costovertebral & costotransverse joints

sternal joints

• manubriosternal joint

• xiphisternal joint

manubriosternal joint

• secondary cartilaginous (symphysis): hyaline on either side of the joint and a disc in the middle

• slightly mobile

• forms the sternal angle (transverse thoracic plane/angle of Louis) at T4-5 intervertebral level

importance of the transverse thoracic plane

• arch of aorta, trachea bifurcates into the bronchi

xiphisternal joint

• primary cartilaginous (synchondrosis)

• slightly mobile in youth

• ossifies in adulthood —> becomes a synostosis (usually after 4th decade)

• becomes one bone

sternocostal joints

• rib 1

• ribs 2-7

rib 1 sternocostal joints

• costal cartilage —> manubrium

• primary cartilaginous joint (synchondrosis)

• almost immobile, protect important vessels and trachea, etc

ribs 2-7 sternocostal joints

• synovial plane joints

• costal cartilages —> sternum

• permit small gliding movements during respiration

• supported by anterior and posterior sternochondral ligaments

costochondral joints

• junction beteen rib and its costal cartialge

• primary cartilaginous (synchondrosis)

• immobile

interchondral joints

• here false ribs join true ribs

interchondral joints of costal cartilages 6-9

• synovial plane joints

• beteen costal cartilages of ribs 6-7, 7-8, 8-9

  • allo small gliding movements

interchondral joints of costal cartilages 9-10

• fibrous joint

• more rigid connection

• minimal to no movement

costovertebral joints

• red crosses: here rib 5 joints vertebral body 4, vertebral body 5 and intervertebral disc

• synovial plane joints

• head of rib articulates ith thoracic vertebrae

• allo small gliding movements for espiration

• ribs 1, 10, 11, 12 —> single vertebral articulation

costotransverse joins

• synovial plane joints

• tubercle of rib ←→ transverse process of corresponding vertebra

• present in ribs 1-10 (absent 11-12)

• allow small gliding movements

• bottom red circle (the top red circle is the costovertebral joint)

thoracic cage movement

• different shape sof costotransverse joints allo rib movments that expand the thoracic cage in different direcitons during inspiration

movement in ribs 2-7

• shape of costotransverse joint is rounded

• pump handle movement

• elevation of ribs and sternum

• increases antero-posterior (AP) diameter

• sternum moves upard and forard

movement in ribs 8-10

• shape of costotransverse joint is flat

• bucket handle movement

• elevation of lateral rib shafts

• increases transverse (lateral) diameter

• ribs move outard and upard

muscles of the thoracic cage

• exctinsic muscles

• intrinsic muscles (intercostal)

• diaphragm

extrinsic muscles

• ith attachments to ribs

• come from somewhere that is not the thoracic cage

• recruited during exercise

pectoralis minor

from scapula to ribs

pectoralis major

• to the sternum

sternomastoid

to the manubrium

examples of extrinsic muscles

• abdominal muscles

• pectoralis minor and major

• sternomastoid

intercostal muscles

external, internal, innermost

external intercostal

• donard and forard direction

• external intercostal membrane anteriorly, external is see-through (aponeurosis) anteriorly

• elevate ribs = muscles of inspiration

internal intercostal

• perpendicular to external intercostal

• internal intercostal membranes (aponeurosis) posteriorly

• depress ribs = muscles of expiration

innermost intercostal

• same direction as internal intercostal

• not a continuous sheet of muscle

here are the vein artery and nerve in comparison to the intercostal muscles?

in beteen the internal and innermost intercostal

diaphragm

• double dome-shaped muscle forming the floor of the thoracic cage and separation the thorax from the abdomen

• right dome higher due to underlying liver

• attaches to xyphoid process anteriorly (T9) and L1-3 posteriorly (therefore the back is a bit lower don)

• muscle fibres radiate from the peripheral margins of the thoracic cage and converge into a central tendon

central tendon

• heart sits on central tendon

• rigid structure that can’t contract, avoids movement of the shape of the heart

• muscles surrounding this tendon contract

attachments of the diaphragm

• sternal (anterior)

• costal (lateral)

• lumbar (posterior)

sternal attachment of the diaphragm

• xiphoid process

costal attachment of the diaphragm

• internal surfaces of ribs 7-12 and their costal cartialges (costal margin for ribs 7-10)

lumbar attachment of the diaphragm

• lumbar vertebrae via left and right crura and arcuate ligaments

contraction of the diaphragm

• diaphragm goes flat during inspiration (concentric contraction)

• natural recoil for breathing out

mechanism of inspiration

• create a low pressure environment in lungs so that air rushes in

• do this by increasing volume by stretching thoracic cage

• pump handle increases front-to-back diameter

• bucket handle increases side-to-side diameter

• diaphragm contracts to increase top-to-bottom diameter

forced breathing

• inspiration: sternocleidomastoid, scalenes, pectoralis minor

• expiration: abdominal muscles, internal intercostals

three major diaphragmatic openings

• caval opening (blue)

• oesophageal hiatus (middle)

• aortic hiatus (red)

caval opening

• inferior vena cava

• through the central tendon

• T8

oesophageal hiatus

• oesophagus goes through the right cruus (in the muscle, functional sphincter)

• therefore, hen the muscle contracts, the oesophagus is closed to prevent food regurgitating

• T10

aortic hiatus

• abdominal aorta

• T12

• not a true hole, passes next to the vertebrae and the diaphragm pins it to the lumbar vertebrae

intercostal neurovascular bundle

• located in costal groove beteen internal and innermost intercostal muscles

• intecostal vein (superior)

• intercostal artery (middle)

• intercostal nerve (inferior)

• supplies thoraacic all (muscle, skin and pleura)

arteries of the thoracic cage

• artery gives off posterior intercostal arteries

• anastomoses ith anterior intercostal arteries, hich are given off by internal thoracic artery

veins of the thoracic cage

• anterior intercostal veins

  • drain into the internal thoracic vein, then brachiocephalic vein, then SVC

• posterior intercostal veins

  • drain into the azygos system (vein next to aorta)

azygos venous system

• variable

• azygos vein

• hemiazygos

• accessory hemiazygos

• drains posterior thoracic all and abdomen

azygos vein

• right

• T12→T5

• drains into SVC, hich drains into right atrium

• receives right hand side of posterior intercostal veins

hemiazygos

• left loer

• T12→T9

• crosses to azygos at T9

• drains loer posterior intercostal veins on the left

accessory hemiazygos

• left upper

• T5→T8

• crosses to azygos at T8

• drains top fe posterior intercostal veins on the left

innervation of the thoracic cage

• intercostal nerves

• most superior structure of the intercostal bundle is vein, then arteries, then nerves

• no posterior/anterior distinction

intercostal nerves

• arise from ventral rami T1-T11

• T12 = subcostal nerve

functions of intercostal nerves

• motor → intercostal muscles

• sensory → skin of thoracic all + parietal pleura

• contribution to peripheral diaphragm sensation

innervation of the diaphragm

• motor: phrenic nerve (C3-5 ventral rami), pierces the diaphragm and pierces it from underneath

• sensory: phrenic nerve (central diaphragm - central tendon) and intercostal nerves (peripheral diaphragm - muscular part)

• heart pain can be referred to ja and neck area as C3-5 innervation

compartments of the thoracic cavity

• pleural cavities (right and left)

• mediastinum (centrally)

mediastinum

• the heart lies ithin the fibrous pericardium in the middle mediastinum (space in the midde)

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subdivisions of the mediastinum

• superior + inferior → (anterior, middle, posterior)

• heart occupies the largest part (middle mediastinum)

• anterior mediastinum is the gap in the front, posterior mediastinum contains the oesophagus, etc

middle mediastinum

• pericardiac sac & heart lies obliquely, 1/3 to the right of the midsternal line and 2/3 to the left

• 2nd rib to 5th intercostal space (apex of heart)

pericardium

• layer 1: fibrous pericardium

• layer 2: serous pericardium

fibrous pericardium

• tough external layer, continuous with diaphragm, anchors and protects the heart

serous pericardium

• thin double-layered membrane (parietal and visceral layers), lines fibrous pericardium and covers the heart, secretes serous fluid into pericardial cavity to reduce friction during cardiac movement

• parietal (right image): somatic innervation, continuous over the heart and the vesels of the heart, stuck to fibrous layer

• visceral: autonomic innervation (left image lining heart), continuous ith parietal layer at the great vessels

pericardial cavity

the space beteen parietal and visceral layers, contains serous fluid, enables heart to beat in a frictionless environment

in image can see ho parietal and visceral layer are continuous

close up of pericardium

serous fluid secreted into the pericardial cavity

development of the heart and pericardium

• heart starts as a tube and then bends

• red: right chambers, blue: left chambers

• front of the heart is predominantly right chamebrs

shape of the heart

• apex should line up ith mid clavicle on the left

external features of the heart

• atrioventricular groove

• interventricular grooves

atrioventricular groove

• coronary sulcus

• separates atria from ventricles

interventricular grooves

• separate right and left ventricles

• anterior and posterior

• arteries and veins run through them

right atrium

• SVC - blood from upper body

• IVC - loer limb, pelvis, gut

• pectinate muscles: run parallel

• crista terminalis:

• fossa ovalis

• atrioventricular orifice

• right auricle

• coronary sinus

fossa ovalis

• open in a foetus (foramen ovalis), direct connection between atria, as foetus’s don’t need to send their blood to pulmonary circulation as it’s already oxygenated

crista terminalis

• bump corresponding to demarcator beteen rough pectinate muscles and smooth muscles

right auricle

• gives more room for the chamber to expand hen blood enters

• extension of the chamber

coronary sinus

• receives deoxygenated blood from the heart itself

• drained from cardiac veins

right ventricle

• atrioventricular valve

• trabeculae carnae

• pulmonary valve

right atrioventricular valve

• cusps (3)

• chordae tendinae

• papillary muscle (3)

• called the tricuspid valve

trabeculae carnae

• irregular muscle hich the papillary muscles are connected to

pulmonary valve

• semilunar valve

• three cusps

• no chordae tendinae or papillary muscles

right atrioventricular valve

• cusps (2)

• chordae tendinae

• papillary muscle (2)

• called the bicuspid valve