ANAT: Heart + Thoracic Cage Flashcards
1
Q
4 main stages of the embryonic period
A
- tri-laminar disc: cleavage, implantation, gastrulation
- embryonic: organs developing, heart and limbs complete
- foetal period: organs maturing
- post-birth: CNS & lungs still developing
2
Q
describe foetal circulation including shunting
A
- umbilical vein carries oxygenated blood (from placenta) to liver, h/w not functioning yet so need to shunt/bypass: ductus venosus goes from liver > RA
- h/w lungs also not functioning yet so need to shunt again
- ductus arteriosus (RA > RV > PT > aorta) OR foramen ovale (RA > LA > LV > aorta)
- blood distributed to head then rest of body (therefore brain develops earlier than rest of body)
3
Q
describe pressure in the heart (foetal vs adult)
A
- foetal: high on R side b/c lungs don’t function (have to shunt blood to the L side)
- adult: high on L side b/c lungs work and the L side pumps to the rest of the body
4
Q
which adult structures are formed by the 3 foetal shunts
A
- ductus venosus (liver) - forms ligamentum venosum
- foramen ovale (atria) - forms fossa ovalis
- ductus arteriosus (between PT and aorta) - forms ligamentum arteriosum
5
Q
2 functions of a DEVELOPING heart
A
- support foetal circulation
- prepare to support circulation after birth
6
Q
which embryonic layer becomes the heart?
A
- mesoderm
7
Q
general formation process of the heart
A
- formation of a single cardiac tube which starts beating and loops around
- formation of septa (atrial and ventricular) and valves
- outflow tract (truncus arteriosus) partitions into pulmonary trunk + aorta
8
Q
describe how the heart moves from the cervical region to the thoracic cavity
A
- cranial-caudal folding
- brain grows very quickly > causes forward tilt > foetal position
- middle region contains rigid somites which don’t move > flat region
- tail curls
- forces heart and diaphragm into thorax
9
Q
which embryological structure gives rise to the diaphragm?
A
- septum transversum
10
Q
which type of folding results in a single heart tube?
A
- lateral folding: 2 tubes merge into 1
11
Q
describe anatomical indications of the heart’s relationship w/ the diaphragm and liver
A
- pericardium and liver attached to diaphragm
- diaphragm innervated by C3-5 (phrenic n.) = must have dragged down cervical nerve roots when it moved from cervical region > thorax
12
Q
what are A, B, C and what do they form?
A
- A = outflow tract (truncus arteriosus: aorta, pulmonary trunk, semilunar valves)
- B = bulbus cordis: forms smooth parts of ventricles
- C = primitive ventricle: forms rough (trabecular) muscles in ventricles
13
Q
what are D, E, F and what do they form?
A
- D = primitive atria: forms rough (pectinate) muscles in atria
- E = sinus venosus: forms smooth parts of atria
- F = inflow tract
14
Q
describe how the single heart tube moves into different positioning
A
- outflow was superior > moves anterior and inferior (ventricles)
- inflow was inferior > moves more posterior and superior (atria)
15
Q
what are the endocardial cushions?
A
- located in the middle of the heart (dorsal and ventral)
- gives signals for heart septation and valve formation
16
Q
describe the process of atrial septation
A
- 1) septum primum grows b/n atria
- 2) foramen primum grows in septum primum
- 3) septum primum reaches endocardial cushion > closes off foramen primum
- 4) ostium (foramen) secundum forms (superior to primum)
- 5) septum secundum forms to the right of primum - thicker wall, rigid
- 6) foramen ovale forms (inferior to ostium secundum)
- 7) FINALLY - when blood flows from R > L, it opens the flexible septum primum. As pressure gets higher on the L side, it closes. this should actually fuse a few weeks after birth, but in some ppl does not close > ‘probe patent’
17
Q
what is the septum secundum defect?
A
- when foramen ovale or foramen secundum are too large and overlap
- doesn’t close after birth
18
Q
atrial septal defect - probe patent foramen ovale
A
- when the septum primum does not fuse into the septum secundum
- may never lead to any Sx b/c pressure is high on L side so keeps septum secundum closed
- becomes an issue during pulmonary stenosis > increased pressure on R side which opens the foramen ovale
- mixing of oxygenated and deoxygenated blood
19
Q
ventricular septation
A
- septum simply grows towards endocardial cushion
20
Q
how are the papillary muscles formed?
A
- from heart tissue itself
21
Q
ventricular septal defect
- is this harmful in a foetus?
A
- when ventricular septum doesn’t form properly
- not harmful in utero b/c pressure is higher on R side so shunting occurs anyway
- when born: pressure increases on L side = mixing of blood
22
Q
endocardial cushion defect and is this an issue in a foetus?
A
- ECC doesn’t grow properly > atrial and ventricular septa dont develop
- mixing of blood in all 4 chambers
- not an issue in FOETUS b/c they get their oxygenation from mother
23
Q
describe what happens during outflow septation
A
- truncus arteriosus splits into aorta and pulmonary trunk ( > 2 pulmonary arteries), which twist around
- from regular anatomical view: aorta is posterior and right
- pulmonary trunk is anterior and left
24
Q
describe the semilunar valve structure
A
- aortic valve: posterior cusp
- pulmonary trunk valve: anterior cusp
- both still have a R and L cusp but kinda twisted
25
how to tell L and R side of heart using coronary arteries
- LCA splits into 2 (LAD and circumflex)
- RCA is just one
26
auscultation position for 4 heart valves
- pulmonary and aortic valves are right behind the sternum so not useful
- All Patients Take Medicine
- aortic valve: 2nd R parasternal
- pulmonary valve: 2nd L parasternal
- tricuspid: 4th L parasternal
- mitral: 5th L midclavicular
27
describe where the recurrent laryngeal nerves run
- vagus nerve gives off L and R recurrent laryngeal nerves
- R: hooks around subclavian artery
- L: hooks under arch of aorta
28
what happens when the truncus arteriosus doesn't develop properly?
- persistent truncus arteriosus: aorta and PT don't divide > mixing of blood
- transposition of great vessels: linear formation instead of twisting > each vessel comes out of the wrong ventricle
- due to endocardial cushion defect
29
treatment for transposition of great vessels
- give prostaglandins to maintain ductus arteriosus
- since pressure is higher on L side than R side, this will force blood the other way thru the right vessel
30
which conditions will lead to cyanosis?
- basically anything that involves deoxygenated blood entering systemic circuit
- tetralogy of fallot (pulmonary stenosis, VSD, overriding aorta, R ventricular hypertrophy) - these don't cause cyanosis on their own, but because of the overriding aorta sitting over the VSD, mixed blood enters systemic circuit
- transposition of great vessels
- persistent truncus arteriosus
- probe patent foramen ovale
31
which conditions will not lead to cyanosis?
- conditions where oxygenated blood still reaches systemic circuit
- ASD, VSD
- patent ductus arteriosus
- aortic or pulmonary stenosis, aortic coarctation (narrowing), mitral stenosis
32
functions of the thoracic cage
- protect organs from injury
- aids in respiration by providing space, decreasing friction and coordinating movement
33
components of the thoracic cage
- ribs
- vertebra
- sternum
- intercostal muscles
34
what are A, B, C, D, E?
- A = clavicles
- B = suprasternal/jugular notch
- C = xiphisternal junction
- D = sternal angle/ angle of Louis
- E = costal margin and xiphoid process
35
what are A, B, C, D, E?
- A = level of nipple shows 4th intercostal space (ideally)
- B = anterior median line
- C = parasternal lines
- D = midclavicular lines
- E = mammillary lines
36
why is the nipple a bad surface landmark for a physical exam?
- its position can vary a lot based on breast size, pregnancy, gender etc
37
what are A, B, C?
- A = anterior axillary line
- B = mid axillary line
- C = posterior axillary line
38
what is the thorax directly connected to and what is the significance of this?
- head and neck
- upper limbs
- abdomen
- therefore chest pain can be referred from any of these regions
39
why is the diaphragm innervated by the phrenic nerve?
- originated in cervical region and migrated down into thorax
- therefore brought down C3-C5 with it
40
why do newborns have shallow breathing?
- their liver is so big and takes up some of the room of the diaphragm
41
3 parts of sternum
- manubrium
- body
- xiphoid process
42
types of ribs
- true ribs (1-7): articulate w/ sternum via costal cartilage
- false ribs (8-10): articulate via costal arches
- floating ribs (11-12): not connected to sternum at all, slope downward
43
typical vs atypical ribs
- typical (3-9): ribs that have same components - head, neck, tubercle, body
- atypical (all others): ribs that have unique structures
44
what important things does the sternal angle indicate?
- RATPLANT (T4/T5)
- Rib (2nd)
- Arch of aorta
- Tracheal bifurcation
- Pulmonary trunk
- Left recurrent laryngeal nerve + Ligamentum arteriosum
- Azygos vein drains to SVC
- Nerves - cardiac plexus
- Thoracic Duct
- (transthoracic plane - division of superior/inferior mediastinum)
45
what happens re: CPR with kids vs adults?
- kids have a very flexible thoracic cage whereas adults have brittle costal cartilage
- therefore in kids = risk of compression of heart etc whereas adults = lungs @ risk of puncture
46
2 thoracic apertures
- superior (inlet/outlet) = connection to upper limb, head and neck
- inferior = abdominal cavity + pelvis
47
which structures travel through the superior thoracic aperture?
- oesophagus
- trachea
- great vessels and nerves of head/neck and upper limbs
- apex of lungs
- L subclavian artery
- both common carotid a.
- both brachiocephalic v.
- both subclavian v.
48
boundaries of the superior thoracic aperture
- posterior, middle and anterior scalenes (connect neck to thoracic cage) - accessory muscles of breathing
- sternal/jugular notch
- suprapleural membranes
49
boundaries of the inferior aperture
- diaphragm
50
3 spaces inside the thoracic cavity
- pericardial cavity
- pleural cavity
- mediastinum
51
describe the dome shape of the diaphragm
- anteriorly and R, it is superior
- posteriorly and L, it is inferior
52
what are the 3 apertures in the bottom of the diaphragm and what structures pass through them?
- T8 (caval hiatus): inferior vena cava and R phrenic n.
- T10 (oesophageal hiatus): oesophagus and vagus n.
- T12 (aortic hiatus): aorta and thoracic duct
- I ate 10 Eggs At 12pm
53
which muscles help w/ breathing in the various dimensions?
- vertical: diaphragm
- AP/transverse: intercostals
54
functions of intercostal muscles
- fix the ribs
- maintain or increase tone of intercostal space
- resist pressure changes
- assist w/ respiration by elevating ribs
55
external intercostals:
- location
- fibre orientation
- when are they replaced by a membrane?
- when are they most active
- more lateral
- fibres run along inferoanteriorly ('hands in pockets')
- replaced anteriorly by external intercostal membrane, approximately @ midclavicular line
- most active during forced inspiration - elevate ribs
56
internal intercostals:
- location
- fibre orientation
- when are they replaced by a membrane?
- when are they most active
- more medial (deep to externals)
- fibres run inferoposteriorly ('hands on chest')
- replaced posteriorly by internal intercostal membrane, approximately @ midscapular line
- most active on forced expiration (interosseous portions depress ribs, interchondral portions elevate ribs)
57
innermost intercostals location + fibre orientation
- deep to internal intercostals and neurovascular bundle
- similar fibre orientation to internal intercostals (hands on heart)
58
subcostal muscles
- form bridges across the INTERNAL SURFACES from one rib to 2-3 ribs below
- (whereas intercostals only bridge two adjacent ribs)
59
transverse thoracic muscles
- location
- function
- attach internal surfaces of costal cartilages 2-6 to POSTERIOR sternum
- accessory muscles to respiration when bent over
- aid in proprioception
60
what is the lung hilum?
- where the bronchi attach to the lungs
61
what is the pleura?
- simple epithelial layer (mesothelium - comes from mesoderm)
- double layered sac (technically one layer that doubles on itself)
- the pleural cavity (between the layers) contains fluid to decrease friction during breathing
62
why is the pleural cavity called a potential space?
- as lungs continue to grow, pleural cavity gets smaller and there is basically no space
- if lung collapses or there is a haemothorax or pneumothorax, this space can get bigger
- can use X-ray to guide thoracentesis
63
pulmonary ligament
- connects visceral and parietal pleura
64
what is a point of reflection
- when visceral pleura turns into parietal (b/c it wraps around itself)
65
describe the difference between the serous membrane surrounding the heart vs lungs
- heart has visceral, parietal and then fibrous pericardium (superficial to parietal)
- lungs only have visceral and parietal
66
intercostal neurovascular bundle
- run within subcostal groove (between internal and innermost intercostals)
- collateral branches run more inferiorly in the intercostal space, just above the rib BELOW
- from superior to inferior: vein, artery, nerve
- vein is most protected due to rib, nerve is least protected
67
where should you inject an intercostal nerve block?
- pick an intercostal space
- do the injection below the superior rib, but closer to the inferior rib
- doesn't matter if we damage the collateral neuromuscular bundle but we want to avoid damaging the main ones
68
where do the intercostal arteries arise from?
ANTERIOR
- 1-6: internal thoracic a.
- 7-9: musculophrenic a.
POSTERIOR
- 1-2: subclavian a.
- 3-11: thoracic aorta
69
where does the intercostal nerves arise from?
- T1-T11: ventral rami
- T12 is subcostal n.
70
where do the anterior intercostal veins drain into?
- drain into internal thoracic v. > L/R brachiocephalic v. > SVC
71
where do the left posterior intercostal veins drain into?
- 1: L brachiocephalic v. > SVC
- 2-3: L superior intercostal v. > L brachiocephalic v. > SVC
- 4-8: accessory hemiazygos v. > azygos v. > SVC
- 9-12: hemiazygos v. > azygos v. > SVC
72
where do the right posterior intercostal veins drain into?
- 1: R brachiocephalic v. > SVC
- 2-4: R superior intercostal v. > azygos v > SVC.
- 5-12: azygos v. > SVC
73
when would anterior and posterior intercostal arteries anastomose?
- increase in demand for blood
- blockage or narrowing of arteries
74
how to know whether layers of back muscles originated at the front or back of the embryo?
- 'true'/intrinsic back muscles are innervated by dorsal rami of mixed spinal nerves, usually deeper
- superficial, extrinsic back muscles are innervated by branches of brachial plexus (anterior rami)
75
what structures do the intercostal nerves innervate in order?
- muscle, then skin, then pleura
76
what is the cardiophrenic angle?
- the angle formed b/n the diaphragm and the RA on an X-ray
77
what is the costophrenic angle?
- the angle formed b/n the diaphragm and the ribs on an X-ray
78
why does the heart have a fibrous pericardium (extra parietal layer?)
- visceral and parietal (serous) pericardium are formed when the heart migrates into the thorax
- fibrous pericardium is formed when lungs expand and push their parietal pleura into the heart > 3rd layer
79
which layer of the pericardium is more sensitive to pain?
- parietal and fibrous b/c comes into contact w/ somatic nerve
- visceral has no pain receptors
80
innervation of pericardium
- sensory: phrenic n. (parietal and fibrous only)
- vagus nerve (unknown function)
- sympathetic trunk (T1-4) = control blood supply to pericardium
81
branches of right coronary artery
- SA nodal a. (60% )
- AV nodal a.
- R marginal a. (RV)
- PDA (RV, LV, posterior 1/3 IVS) if R dominant, anastomoses w/ LAD
82
what parts of the heart does the RCA and LCA supply?
- RCA: RA, RV, posterior 1/3 of interventricular septum
- LCA: LV, LA, anterior 2/3 of septum
83
branches of left coronary artery
- LCx gives off L marginal a. and SA nodal a. (40%)
- LAD (LA, LV, anterior 2/3 IVS)
84
what happens re: vasculature in a LEFT dominant heart?
- PDA is given off by LCx = entire L ventricle and septum are perfused by LCA
- 'widowmaker artery' b/c if blocked you completely lose blood supply to everything except the R ventricle (you're fucked lol)
85
key venous drainage of the heart
- coronary veins (great, middle and small cardiac veins) drain into coronary sinus > drains into R atrium
- coronary sinus sits in groove b/n atria and ventricles posteriorly
86
coronary artery and vein pairings
- great cardiac vein: LAD
- middle cardiac vein: PDA
- small cardiac vein: R marginal branch (RCA)
87
where do the coronary arteries originate
- from the root of the aorta, just superior to the aortic valve leaflets
88
which parts of the cardiac conduction system does the RCA supply?
- SA node + AV node
89
how do the coronary arteries fill up?
- blood collects in the concave leaflets of the aortic and pulmonary valves
- coronary vessels fill during diastole (rest)
90
what are A, B, C
- A = LCA
- B = LAD
- C = RCA
91
what are D, E, F
- D = LCx
- E = 1st marginal artery
- F = 2nd marginal artery
92
what are G, H?
- G = acute marginal artery
- H = PDA
93
clinical relevance of filling of coronary arteries via cusps of valves
- if valves don't work then arteries won't fill up > poorer perfusion of heart even tho arteries themselves may be working fine
94
what is the cardiac plexus made of?
- presynaptic parasympathetic nerves
- postsynaptic sympathetic nerves
95
autonomic innervation of the heart
- sympathetic: originate from T1-T5, synapse in cervical ganglia
- parasympathetic: originate from medulla, travel thru vagus nerve and synapse in cardiac ganglia
96
3 layers of the heart
- endocardium: tunica intima - endothelium inc valves and inner lining
- myocardium
- epicardium (visceral pericardium)
97
structure of cardiac muscle cells
- branched cells w/ one nucleus (sometimes two)
- striated (involuntary)
- has sarcomeres between Z lines with A (dark) and I (light) bands
- T tubules and only one associated piece of sarcoplasmic reticulum form dyads (not triads) @ Z lines
- cardial muscle cells joined end-to-end via intercalated discs (gap junctions, fascia (zonula) adherens + desmosomes) - physical and electrical connection for contraction
- many mitochondria
98
what is cardiac tamponade?
- accumulation of fluid in pericardial cavity = pressure on ventricles = decreased preload and CO
- leads to beck's triad: muffled heart sounds, JVD, hypotension
99
2 pericardial sinuses
- transverse: separates aorta and pulmonary trunk (outflow) from superior vena cava (inflow)
- oblique: behind left atrium , between R and L pulmonary veins
100
tetraology of fallot
- pulmonary stenosis
- right ventricular hypertrophy
- ventricular septal defect
- overriding aorta
101
where are the papillary muscles and chordae tendineae?
- L and R ventricles
102
where is the Triangle of Koch?
- R atrium
- indicates location of AV node
- borders: IVC, coronary sinus and tricuspid valve
103
what is the most common congenital malformation of the great vessels?
- coarctation (narrowing) of the aorta
- reduced blood flow to lower body and high pressure in upper body
104
how do Purkinje fibres stain differently to cardiomyocytes?
- Purkinje fibres stain lighter due to high glycogen content
105
describe the structure of the aortic arch
- 3 branches
- R branch is called brachiocephalic trunk. bifurcates into subclavian artery (lateral) and R common carotid (medial)
- middle branch is L common carotid
- L branch is L subclavian artery
106
structural differences b/n atria and ventricles
- atria have crista terminalis and pectinate muscles (irregular ridges/muscles), fossa ovalis
- ventricles have papillary muscle, chordae tendineae and septomarginal trabecula (moderator band)
107
causes for systolic vs diastolic murmur
- systolic (b/n S1/S2): semilunar stenosis, AV regurgitation (due to chordinae tendineae rupture)
- diastolic (b/n S2/S1): AV stenosis, semilunar regurgitation
108
what do the diff murmur sounds indicate
- crescendo/decrescendo: due to semilunar stenosis
- blowing: regurgitation
- rumbling: stenosis
- harsh: turbulent flow thru narrowed area e.g. VSD
- systolic click: regurgitation
- diastolic click: stenosis
109
thoracic outlet syndrome
- can be compressed due to having an extra rib, physical trauma, pregnant or pancoast tumour (tumour of lung apex)
- pancoast tumour can compress inferior trunk of brachial plexus = ulnar nerve
110
describe the contents of the mediastinum
- superior: thymus, SVC, brachiocephalic v, ascending aorta, vagus + phrenic n, thoracic duct, trachea, oesophagus
- anterior: thymus + phrenic nerve
- middle: heart + great vessels
- posterior: thoracic aorta, thoracic duct, azygos system, oesophagus, sympathetic trunk, vagus nerve
111
what 3 heart defects would prevent cyanosis in a Pt with transposition of the great vessels?
- ASD
- VSD
- patent ductus arteriosus
112
3 main Sx of aortic stenosis
- angina
- syncope
- dyspnoea
