Middle mediastina Flashcards
The mediastinum is a
central compartment located in the the thoracic cavity
How many divisions does the mediastinum have?
- 2 divisions but 4 parts
- superior and inferior divisions
- anterior, middle, posterior and superior
Boundary between the superior and inferior mediastinum
T4-T5 transthoracic plane
Lateral boundary of the mediastinum
pulmonary cavities
Middle mediastinum diagram
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Boundaries of the middle mediastinum (5):
- between
- superiorly
- inferiorly
- laterally
- surface landmarks
- between anterior and posterior
mediastinum - superiorly: superior mediastinum
- inferiorly: diaphragm, T8-T9 supine, T9-T10
standing - laterally: pulmonary cavities
- surface landmarks: left costal cartilage and
anterior rib end III-V
Middle mediastinum Content (5):
- pericardium
- heart
- origin/root of great vessels: ascending
aorta, pulmonary trunk divides into PA, PV,
superior and inferior vena cava - right and left phrenic nerve
- right and left periocardiophrenic vessels
middle mediastinum content diagram
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What is the pericardium?
fibroserous membrane surrounding heat and root of great vessels
Fibrous pericardium
- tough, external layer
- dense, irregular CT
Serous pericardium
- serous membrane, internal layer
- mesothelium (lateral plate mesoderm)
Fibrous Pericardium: tough, external layer:
- function
- superiorly
- inferiorly
- anteriorly
- posteriorly
- prevent overfilling of heart
- superiorly: continuous with adventitia of
great vessels - inferiorly: adhered to the central tendon of
the diaphragm
“pericardiophrenic ligament” - anteriorly: attached to the sternum
“sternopericardial ligaments” - posteriorly: loosely adhered to the
posterior mediastinum content by loose
connective tissue
Serous Pericardium: serous membrane, internal layer: three parts:
- parietal layer
- pericardial cavity: potential space
containing fluid - viscera layer (epicardium)
Serous membrane of pericardium: site of reflection of parietal layer onto the visceral layer:
- aorta and pulmonary trunk (arterial)
- superior vena cava, inferior vena cava, and
pulmonary veins (venous) - reflections from pericardial sinuses
Cardiac Tamponade:
- excess fluid within the pericardial cavity
prevents filling of the heart - restricts contraction of the heart
- if there was no fibrous layer that would not
matter as the serous membrane would
expand along with systole
Pericardial Sinuses: State:
- reflection of parietal layer onto the visceral
layer of the serous pericardium - impressions found in the pericardial sac
found where the great vessels enter it - transverse pericardial sinus
- oblique pericardial sinus
Pericardium diagram
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Fibrous pericardium diagram
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Serous pericardium diagram
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Pericardial sinsuses diagram
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Transverse pericardial sinus:
- reflection between arterial and venous
group of great vessels - relevance: cross-clamp arterial group for
coronary bypass
Oblique Pericardial Sinus:
- reflection around venous group of great vessels
Pericardium blood supply diagram
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Blood supply to the pericardium and pericardial sinuses:
- pericardiophrenic artery
- musculophrenic artery
- coronary artery
- bronchial artery/ oesophageal artery/
superior phrenic artery directly from the
thoracic aorta
Venous drainage of the pericardium and pericardial sinuses:
- pericardiophrenic vein
- azygous venous system tributaries
Three layers of the hear:
- endocardium: inner layer of endothelium
and CT - myocardium: middle layer of myocytes
(cardiac muscle cells) - epicardium (visceral serous pericardium):
outer layer
layers of heart diagram
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Structure of the heart:
- 2 sides: right and left
- 4 chambers: right atrium, left atrium, right
ventricle, left ventricle - 4 valves: bicuspid = mitral, tricuspid = right,
pulmonary semilunar valve and
aortic semilunar valve - right side: receives venous blood, circulates
de-oxygenated blood to the
lungs - left side: receives arterial blood, circulates
oxygenated blood to the body
Heart structure diagram
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heart structure (lines) diagram
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Cardiac cycle: (graph)
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cardiac cycle diagram
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Orientation of the heart:
- trapezoid from anterior and posterior
views - apex: 5th intercostal space mid-clavicular
line, formed by inferolateral part of
the left ventricle - base: T6-T9, formed by left atrium (minor
contribution from right atrium) - 4 surfaces
- 4 borders
Orientation of the heart: 4 surfaces:
- anterior surface:
- inferior surface:
- right pulmonary surface:
- left pulmonary surface:
- anterior surface: (sternocostal) right
ventricle - inferior surface: (diaphragmatic) left
ventricle, part of right
ventricle - right pulmonary surface: right atrium
- left pulmonary surface: left ventricle
Orientation of the heart: 4 surfaces: diagram
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Orientation of the heart: 4 borders:
- right border: RA, between superior and
inferior vena cava - inferior border: RV, part LV
- left border: LV and left auricle
- superior border: RA, LA, right auricle, left
auricle, ascending aorta,
pulmonary trunk, superior
vena cava
Orientation of the heart: 4 borders: diagram:
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Right atrium anatomy:
- right auricle
- sinus venarum = smooth walled
- pectinate muscle
- crista terminalis (internal)
- sulcus terminalis (external)
- vessel opening: superior vena cava, inferior
vena cava, coronary sinus - fossa ovalis (foramen ovale)
Right atrium internal structure diagram
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Right ventricle Anatomy:
- conus arteriosus (infundibulum)
- trabeculae carneae
- supraventricular ridge
- tricupsid valve, cusps and orifice
- chordae tendineae
- 3 papillary muscles: anterior, septal,
posterior - pulmonary semilunar valve
- pulmonary sinus
What carries theright branch of the atrioventricular bundle?
- moderator band from the base of
interventricular septum to the anterior
papillary muscle - RV
Diagram of right ventricle of heart
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Left atrium anatomy:
- left auricle
- pectinate muscle
- fossa ovalis (foramen ovale)
Left atrium diagram:
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Left ventricle anatomy:
- trabecular carneae
- 2 papillary muscles: anterior and posterior
- mitral valve: cusps and orifice
- chordae tendineae
- aortic vestibule
- aortic valve: semilunar cusps and sinuses
- coronary artery orifices: right and left
left ventricle diagram
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break diagram 1
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break diagram 2
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The right and left coronary arteries arise from
aortic sinuses, coronary orifices
Pathway of the right coronary artery:
in coronary/sulcus/ atrioventricular sulcus/ groove
Pathway of the left coronary artery:
between the pulmonary trunk and left auricle in the coronary sulcus
Right and left coronary artery diagram
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Right coronary arteries:
- location
- branches
- supplies
- arise from right aortic sinus, coronary
orifice
Branches:
- sinoatrial node br. (60%)
- right marginal br.
- atrioventricular node br. (80%)
- posterior interventricular br. CARDIAC
DOMINANCE (67%) - supplies the right atrium, right ventricle, left
ventricle (diaphragmatic surface)
Heart diagram
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Left Coronary Artery:
- location
- branches
- supplies
- arises from the left aortic sinus, coronary orifice
Branches:
- anterior IV br.(left anterior descending LAD)
- diagonal br. (from the anterior IV br.)
- circumflex br.
- left marginal br. (from circumflex br.)
- supplies LA,LV, part RV
Where does the coronary sinus?
lies in the posterior coronary sulcus
Cardiac veins drain into
the coronary sinus
Coronary veins: tributaries:
- great cardiac vein (anterior IV br.)
- small cardiac vein (R marginal br.)
- middle cardiac vein (posterior IV br.)
- left posterior ventricular/cardiac vein
Coronary veins diagram
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coronary veins diagram
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Cardiac Development: what day does the paired heart tube develop? Which period of development is this in?
- Day 18
- embryonic period
Day 18: paired heart tube develops:
- from?
- why?
- from cardiac progenitor cells
- to meet the nutritional needs of the embryo
cardiac embryology development
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What happens on day 21/22 of cardiac development?
- heart tubes fuse in midline
- heart starts to beat (day 22/23)
- bubus cordis and truncus arteriosus
- ventricle
- primordial atrium
- sinus venosus
Day 21/22: what day of cardiac development is this?
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- What happens on day 22-28 of cardiac
development? - where does the atria and sinus lie in
relation to this
- dextral looping (heart tube folding)
“bulboventricular loop) - atria and sinus venosus lie dorsally to
truncus arteriosus, bulbus cordis and
ventricle
Day 22-28 image: what day is this?
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End of week 4 of cardiac development?
- endocardial cushions form to divide the
atrioventricular canal, primordial atrium
and ventricle
insert end week 4 cardiac development
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End week 5 cardiac development?
- truncus arteriosus partitioned and 180
degree spiralling - bulbus cordis incorporated into the
ventricle walls
End week 7 cardiac development?
IV septum closes
End week 5 development diagram
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Pre-natal circulation diagram
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Post-natal circulation: Remnants:
- foramen ovale > fossa ovalis
- ductus arteriosus > ligamentum arteriosum
- ductus venosus > ligamentum venosum
- left umbilical vein > ligamentum teres
hepatis - umbilical arteries > median umbilical
ligament
Conducting System of the heart:
- generates and transmits electrical impulses across cardiac myocytes (myogenic conduction)
- sinoatrial node = cardiac pacemaker:
- located at the superior end of the
sulcus terminalis - atrioventricular node:
- located near the opening of coronary
sulcus - Atrioventricular bundle
- bundles (left and right)
- Purkinje fibers (subendocardial branches)
Conducting system:
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conducting system
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Pericardium innervation:
- sensory: phrenic nerve (C3,C4,C5)
- autonomic somatic nervous system:
sympathetic trunk
superficial cardiac plexus diagram
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Heart Innervation:
- cardiac plexus
- sensory: follow SNS T1-T5/T6
- autonomic SNS: sympathetic trunk (T1-
T5/T6) - autonomic peripheral nervous system: Vagus Nerve (Cranial nerve X)
cardiac plexus diagram
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Referred pain: from viscera to a more distant site: somatic:
- skeletal muscle, bones, connective tissues
- sharp, localised pain
- follow dermatome or cutaneous mapping
Referred pain: from viscera to a more distant site: visceral:
- viscera of body cavitities and vessels
- dull, poorly localised pain
- often referred to a dermatome
- usually due to stretch, ischaemia, chemical
irritation
Cardiac Referred pain to
T1-T5/T6
Referred pain diagram
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Which part of the trilaminar disc is the serous membrane derived from?
Lateral plate mesoderm
Function of the pericardial cavity:
- friction free movement of the heat when contracting
