anatomy of the heart and organisation of nerves in the thorax Flashcards
where is the mediastinum located
in between the two pleural cavities of the lungs
sections of the mediastinum
anterior, posterior, superior, inferior, middle
what is the pericardium within the middle of the mediastinum
fibroserous sac surrounding heart and its great vessels
what 2 layers does the pericardium consist of
fibrous and serous
what 2 parts does the serous section consist of
parietal and visceral
what does the parietal section line
fibrous
what does the visceral section adhere to
heart
what are the two pericardial sinuses - important clinically to limit outflow of heart
transverse and oblique (where serous visceral reflects back on itself to become parietal layer)
what does the transverse pericardial sinus do
separates arteries from veins
what is the oblique pericardial sinus formed by
reflection onto pulmonary veins of heart
stages of pericardial sinuses formation - from vertical to bending in 2
primordial heart tube in pericardial sac → primordial tansverse pericardial sinus → heart loops ventrally → primordial arterial and venous ends of the developing heart brough together, forming transverse pericardial sinus; veins expand and pericardial reflection carried out around them to form oblique pericardial sinus
what are the two circuits of the heart
pulmonary and systemic
inflow of right atrium
blood returns bia superior and inferior venae cavae (body) and coronary sinus (heart)
inflow of left atrium
blood returns via pulmonary veins
outflow of right ventricle
outflow to pulmonary trunk
outflow of left ventricle
outflow to ascending aorta
significance of right atrium
AVN tricuspid valve, crista terminalis, musculi pectinati, valve of IVC, valve of coronary sinus (main drainage veins from coronary to heart), opening of coronary sinus
significance of left atrium
mitral valve, small window between right atrium - bypassed in foetus; left auricle, pulmonary veins, valve of foramen (fossa) ovale (permits blood to go right atrium to left atrium and bypass lungs in foetus)
siginificance of right ventricle
conus arteriosus, septal papillary muscle, septomarginal trabecula, posterior papillary muscle, trabeculae carneae, anterior papillary muscle, chordae tendineae (heart strings, embedded by papillary muscles - stops backflow), pulmonary valve
significance of left ventricle
mitral valve anterior cusp, chordae tendineae, anterior papillary muscle, trabeculae carneae (net), posterior papillary muscle, mitral valve posterior cusp; 2 aortic sinuses have holes (coronary aortic sinuses) for coronary arteries
more common variation in coronary arteries; MI - blood issue causing ischaemia; cardiac arrest: not due to ischaemic - electrical
right dominant coronary artery; posterior interventricular branch arises from right coronary artery; marginal; circumflex
less common variation in coronary arteries
left dominant coronary artery; posterior interventricular branch arises from left coronary artery
coronary veins
follow arteries, drain into coronary sinus (IVC of heart - bringing back deoxygenated blood from heart)
sections of the conducting system
SAN, Bachmann’s bundle, AVN, His bundle, left posterior bundle, right bundle, Purkinje fibres
pathway of conduction
excitation begins in SAN → spreads across atria causing contraction → concurrently wave stimulates AVN → travels through bundle of His → travels along bundle branches, through Purkinje fibres, causing ventricular contraction
MRI of heart
braciocephalic vein → SVC → right atrium → pulmonary artery → pulmonary vein → left heart → aorta
functional divisions of CNS
somatic (skin and skeletal muscles), autonomic (organs, smooth muscle, glands)
somatic spinal nerves: wher do motor go
only to skeletal muscle - cannot function without them
somatic spinal nerves: where do sensory go
body wall, not viscera
somatic spinal nerves: what might segmental nerves combine to form
plexi, supplying specialised areas (cervical, brachial, lumbosacral)
structure of plexi
diagram from slide 24; ventral (efferent), dorsal horn, grey, white matter, ramus (division of mixed spinal cord of back and everything else) vs root (not mixed)
define dermatome
area of skin supplied by single spinal nerve on one side or from single spinal cord level (not vertebral levels) (segmented); T4 is nipple
define myotome
part of skeletal muscle supplied by single spinal nerve on one side or from single spinal cord level
how many pairs on intercostal nerves are there
11 (+ 1 subcostal)
what types of nerves are present in intercostal nerves
mixed, so sensory and motor
what do intercostal nerves supply
intercostal spaces
spinal/segmental nerves
anterior primary rami
lateral cutaneous branch
anterior and posterior
anterior cutaneous branch
medial and lateral
where are phrenic nerves (in front of lung root (vagus behind), motor to diaphragm, sensory to pleura, diaphragm, peritoneum, pericardium) derived from
anterior rami of spinal nerves C3, 4, 5
what type of nerve are phrenic nerves
somatic, so no autonomic function or visceral distribution
what do phrenic motor fibres supply
skeletal muscle of diaphragm
what do phrenic sensory fibres supply
central diaphragm, its plueral covering, mediastinal pleura, pericardium, peritoneum on inferior surfacr of central diaphragm
what to motor autonomic nerves innovate
cardiac muscle, smooth muscle, glands
what do sensory autonomic nerves innovate
visceral organs
what 2 divisions are autonomic nerves divided into
sympathetic (T1 to L2) and parasympathetic (cranial nerves 3, 7, 9, 10 and S2 to S4)
sympathetic outflow from spinal cord
emerge from spinal cord at sympathetic ganglia; follow somatic nerves to periphery; eosophagus plexus (heart) and prevertebral plexus (abdominal and pelvic viscera)
what sections of neurone do all autonomic motor pathways involve
preganglionic and postganglionic neurones; intermediolateral horn present T1 to L2 as sympathetic cell bodies present there)
where do pathways to body wall synapse
in ganglia of sympathetic trunk; can go up or down before synapsing depending where going to; postganglionic neurones to heart not in chain
where do pathways to viscera synapse
in unpaired ganglia
what does the trunk do
takes fibres up or down; rami (grey-unmyelinated, white-myelinated); won’t synapse will synapse outside of chain in heart; to brain synapse in chain but not same level
function of sympathetic trunks (T1 to L2)
distribute sympathetic nerves to smooth muscle and glands, body wall synapse in ganglia of trunks, viscera synapse in unpaired ganglia, bring pain fibres back to CNS from viscera
significance of fibres from lower T5-T12
reach abdomen in bundles called spanchnic nerves
5 sets of nerves containing parasympathetic fibres
oculomotor (III) cranial nerves, facial (VII) cranial nerves, glossopharyngeal (IX) cranial nerves (all head and neck), vagus (X) cranial nerves (most important as supplies viscera of thorax and most of abdomen), sacral (S2-S4) spinal nerves
sympathetic nerves to lungs and heart
mainly from T2-T4, passing through cervical and upper thoracic ganglia or sympathetic trunk
where are many of the synapses of sympathetic nerves to lungs and heart
in micro-ganglia in pulmonary and cardiac plexuses rather than in trunk ganglia
pulmonary plexuses
left vagus nerve, right vagus nerve, anterior pulmonary plexus, posterior pulmonary plexus
effect on bronchioles of sympathetic nerves
dilate
effect on bronchioles of parasympathetic (vagus) nerves
constrict
cardiac plexuses
superficial cardiac plexus, deep cardiac plexus
effect of sympathetic efferents on heart rate and force of contraction
increase heart rate and force of contraction
effect of parasympathetic efferents (vagus) on heart rate and diameter of coronary arteries
decrease heart rate via pacemaker tissue and constrict coronary arteries
what do sympathetic afferents relay
pain sensations from heart
what do parasympathetic afferents (vagus) relay
blood pressure and chemistry information from heart
where does vagus nerve arise from and leave skull through
arises from medulla and leaves skull through jugular foramina
where does the vagus nerve descend in the neck
posterolateral to common carotid artery
where does left vagus cross
anterior to aortic arch then posterior to left lung root
where does right vagus pass
posterior to right lung root
where do both vagi form a plexus
round oesophagus
what do the vagi separate to form
anterior and posterior oesophageal/gastric nerves
oesophageal plexus: sympathetic afferents relay
pain sensations from oesophagus
oesophageal plexus: parasympathetic afferents (vagus) sense
normal physiological information from oesophagus
what are the branches to chest and abdomen
parasympathetic, with large sensory (enteroceptor) content from gut and lungs
difference between parasympathetic and sympathetic
parasympathetic provide no autonomic supply to body wall (e.g. arterioles and sweat glands)
recurrent laryngeal branch of vagus nerve
not parasympathetic - runs back up neck to supply most skeletal muscles of larynx
vagi in posterior mediastinum
mainly right vagus contributes to oesophageal plexus; nerves also acquire many sympathetic fibres
vagi in posterior mediastinum: inferior continuation
posterior oesophageal nerve, taking right vagal fibres through diaphragm to abdominal viscera
vagi in posterior mediastinum: left vagus
provides fibres to oesophageal plexus then continues as anterior oesophageal nerve
intrinsic nerves of oesophagus
plexus of ganglia and axons within oesophageal wall coordinates activity; can be up/down regulated by autonomic nerves; part of enteric nervous system
positions of phrenic and vagus nerves and sympathetic trunks in superior mediastinum
slide 42
