Week 2: Thorax Flashcards
1
Q
LO: Identify the features of true, false and floating ribs and their attachments to the vertebral column/ sternum
A
- Bony thorax: 12 thoracic vertebrae, 12 rib pairs, sternum
- Typical rib:
o Costal groove runs along internal/ inferior border
o Rib facets articulate with vertebrae: 2 articular facets separated by crest on head, 3rd tubercular facet on tubercle (facing down, articulates with facing up costal facet of transverse process of numerically corresponding vertebra –> costotransverse joint)
o Crest articulates where intervertebral disc would be
o Bone –> end anteriorly with hyaline cartilage tip = costal cartilage - True ribs (1-7): articulate directly with sternum via costal cartilage
- False ribs (8-12): do not articulate directly with sternum;
o Ribs 8-10 articulate anteriorly with costal cartilage of rib 7 – thus articulate indirectly with sternum
o Floating ribs (11-12): no anterior articulation; cartilaginous tips end in thoracic wall musculature
2
Q
LO: Describe the clinical significance of the sternal angle
A
- sternal angle = Angle of Louis = manubriosternal joint
- important clinical landmark from which measure height of JVP (located 3 fingers/ 4-5cm below jugular notch)
- articular demifacets above/ below angle for rib II
3
Q
LO: Enumerate the ribs and intercostal spaces
A
- Intercostal spaces enumerated relative to rib above
- 5th ICS MCL = heart apex
- In life, ICSs closed by intercostal muscles joining adjacent ribs (move ribs to breathe; 3 layers from superficial to deep: external, internal, innermost) and contain lymphatics, veins, arteries, nerves (VAN = intercostal neurovascular bundles located between internal/ innermost intercostal muscles) supplying thoracic wall skin –> parietal pleura
4
Q
LO: Identify the superior/ inferior thoracic apertures and the structures that pass through them
A
- Superior thoracic aperture: aka thoracic outlet; formed by T1, 1st ribs, manubrium superior border
o If viscera are to pass between thorax/ head/ neck/ upper limbs – MUST pass through this opening BUT rigid
o Contains viscera: trachea, esophagus, R/L lung apices, great vessels (common carotid and subclavian arteries, internal jugular and subclavian veins), LVs draining head/ neck/ upper limbs, nerves
♣ If any become enlarged/ cervical rib –> compress others –> thoracic outlet syndrome (Sxs: pale/ swollen/ cold/ aching upper limb, weakness/ wasting muscles of hand, pain/ tingling upper limb) - Inferior thoracic aperture: formed by T12, 12th ribs, 11th ribs, costal margin, ziphisternal joint
o Origin of diaphragm (muscular sheet almost completely closing opening) – structures passing between thorax/ abdomen must pass behind (aorta) OR through openings (esophagus, IVC)
5
Q
Fascia
A
- a connective tissue layer as observed with the naked eye (ie. at the gross level, rather than under a microscope)
6
Q
Epi vs hypodermis
A
- epi = above/ superficial to; the epidermis is superficial to the dermis
- hypo = below/ deep to; the hypodermis is deep to the dermis of the skin
7
Q
Costal groove
A
- runs along inferior border of rib on its internal surface (so you can orient rib!)
8
Q
Bony thorax
A
- consists of 12 thoracic vertebrae, 12 pairs of ribs, sternum
9
Q
True ribs
A
- I-VII
- articulate directly with sternum via their costal cartilage
10
Q
False ribs
A
- VIII-XII
- do not directly articulate with sternum
- ribs VIII-X articulate anteriorly with costal cartilage of rib above, thus articulate indirectly with sternum
11
Q
Costal margin
A
- inferomedial border of ribcage, formed by connected cartilages of ribs VII-X and the xiphoid process
12
Q
Floating ribs
A
- XI-XII
- false ribs with no anterior articulation; cartilaginous tips end in musculature of thoracic body wall
13
Q
Supernumerary rib
A
- “Cervical rib”
- Present in 1% population either uni/ bilaterally
- Articulate with C7
- May –> thoracic outlet syndrome
14
Q
LO: Identify the features of the sternum
A
from superior to inferior:
- manubrium (handle); articulates with ribs I-II
o Manubrium has jugular/ suprasternal notch on top and articulates with clavicles/ rib 1/ rib2 at sternal angle (but cannot palpate manubrium/ rib articulations as clavicle covers)
- body; ribs II-VII
- xiphoid (sword-like) process; rib VII only
15
Q
Eponym
A
- name of a structure/ disease/ procedure derived from name of person who first described/ discovered it
16
Q
Superior thoracic aperture
A
- aperture = opening
- aka thoracic outlet
- formed by T1, ribs I, superior border of the manubrium
- if viscera are to pass between the thorax and head/ neck/ upper limbs, must pass through this opening
- composed of bone, thus rigid
- contains trachea, esophagus, lung apices, great vessels (common carotid/ subclavian arteries, internal jugular/ subclavian veins), lymphatics draining head/ neck/ upper limbs, major nerves
- thoracic outlet syndrome: if any of above structures become enlarged, will compress others due to rigidity of outlet; can also occur in patient with cervical rib
17
Q
Inferior thoracic aperture
A
- formed by T12, ribs XI-XII, costal margin, ziphisternal joint
- origin of diaphragm (muscular sheet that almost closes opening)
- structures that pass between thorax/ abdomen pass either behind diaphragm (aorta) OR through openings in diaphragm (esophagus, inferior vena cava)
18
Q
LO: Describe the innervation of the thoracic wall
A
- Thoracic body wall (all 5 layers) innervated by branches of dorsal/ ventral rami of thoracic spinal nerves T1-12 (contain somatic motor/ sensory, sympathetic postganglionic motor)
o Dorsal rami extend posteriorly –> innervate paraxial region (back muscles/ skin)
o Ventral rami continue between adjacent ribs as intercostal nerves; ventral ramus of T12 spinal nerve continues inferior to 12th rib as subcostal nerve
o As sweep anteriorly/ inferiorly, T7-T11 and subcostal nerve innervate abdo wall - Rami communicantes: connections between sympathetic chain/ ventral ramus/ intercostal nerve
o Convey sympathetic preganglionic fibres from SC cell bodies sympathetic chain ganglion –> sympathetic postganglionic fibres –> rami
19
Q
LO: Identify the structures within the posterior/ superior mediastinum
A
- Arteries
o Aortic arch 3 main branches: brachiocephalic trunk (branches into right common carotid, right subclavian), left common carotid artery, left subclavian artery
♣ Subclavians supply shoulders/ upper limbs, common carotids supply head/ neck - Veins
o Right venous angle: R IJV + R subclavian V –> R brachiocephalic V
o Left venous angle: L IJV + L subclavian V –> L brachiocephalic V
o R + L brachiocephalic veins –> SVC –> RA
20
Q
LO: Describe/ identify the blood supply to/ from the thoracic wall
A
- Posterial arterial supply – Thoracic aorta: o Parietal (“of the walls”) branches of thoracic aorta = posterior intercostal arteries (supply thoracic wall) o Visceral branches of thoracic aorta supply esophagus, bronchial tree, pericardium - Posterior venous supply – Posterior intercostal veins drain posterior thoracic body wall --> azygous venous system --> SVC --> RA o R posterior intercostal veins --> azygous vein (arches OVER R bronchus) --> SVC o L posterior intercostal veins --> hemiazygous V (lower) OR accessory hemizygous V --> cross over midline into azygous V --> SVC - Anterior arterial/ venous supply – Internal surface of chest plate: internal thoracic (mammary) arteries/ veins run vertically along lateral borders of sternum o R/ L subclavian arteries --> R/ L internal thoracic arteries --> anterior intercostal arteries --> arterial anastomoses with posterior intercostal arteries in thoracic wall along MCL o 1+ internal thoracic vein accompanies each internal thoracic artery ♣ Anterior intercostal veins drain intercostal spaces --> internal thoracic veins --> drain superiorly --> brachiocephalic veins --> SVC ♣ Anterior/ posterior intercostal veins form venous anastomoses along MCL - Summary: o Anterior/ posterior intercostal arteries arise from distinct arterial sources (internal thoracic arteries/ thoracic aorta) form arterial anastomosis o Anterior/ posterior intercostal veins drain into distinct venous networks (internal thoracic veins/ azygous venous system) – form venous anastomosis
21
Q
LO: Describe the lymphatic drainage of the body wall
A
- Lymph = excess interstitial fluid
- Blood plasma leaks out of capillaries –> interstitial fluid –> lymphatic capillaries as lymph with cells/ cell products/ pathogens –> lymph vessels –> lymph nodes (cleanse lymph of foreign/ transformed cancerous cells –> venous system
- Lymphatic drainage of thoracic wall follows venous drainage
o Lymph from chest wall drains posteriorly –> intercostal lymph nodes –> thoracic duct ON L SIDE –> L venous angle
o Lymph drains anteriorly –> parasternal lymph nodes –> R/ L bronchomediastinal trunks –> R/ L venous angles
22
Q
LO: Describe/ identify features of the autonomic innervation of the thoracic viscera
A
- ANS (sympathetic/ parasympathetic) innervates smooth muscle, cardiac muscle, glands
o Exception: muscle/ glands in body wall/ limbs ONLY controlled by sympathetic - Sympathetic output for all body targets arises from SC T1-L2 (ie. cell bodies of sympathetic PREganglionic neurons)
o Sympathetic output for thoracic viscera ONLY from T1-T4 –> postganglionic neuron cell bodies in sympathetic chain ganglia
o Rather than travelling back to spinal nerves as with body wall/ limbs, thoracic viscera postganglionic axons directly innervate viscera as sympathetic visceral nerves (ie. sympathetic cardiac nerves) - Parasympathetic output for most body targets arises from brainstem and travels with cranial nerves, remainder from SC S2-S4
o Thoracic viscera receive parasympathetic PREganglionic input from cranial nerve X (vagus nerve)
♣ Vagus nerves descend from brainstem through neck and recurrent branches turn back/ ascend on either side of trachea to innervate larynx
• R recurrent laryngeal nerve recurs around R subclavian artery
• L recurrent laryngeal nerve recurs around aortic arch - Sympathetic/ parasympathetic inputs to viscera overlap in autonomic plexi (ie. cardiac/ pulmonary/ esophageal plexi)
23
Q
Intercostal nerves
A
- ventral rami of thoracic spinal nerves continue between adjacent ribs as intercostal nerves
- T7-T11 intercostal (and subcostal) nerves sweep anteriorly/ inferiorly and innervate abdo wall
