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gross anatomy unit 2 > mediastinum > Flashcards

mediastinum Flashcards

1
Q

mediastinum

A

the region in the middle of the thorax that includes all contents of the thoracic cavity except the lungs and pleura

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2
Q

mediastinum boundaries

A

thoracic inlet, superiorly

diaphram, inferiorly

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3
Q

superior mediastinum

A

lies above the transverse thoracic plane

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4
Q

inferior mediastinum

A

lies below this plane and is subdivided into 3 regions - anterior, middle, and posterior mediastina

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5
Q

middle mediastinum

A

centrally located within the thoracic cavity and contains the pericardium, phrenic nerves, heart and roots of the great vessels

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6
Q

pericardium

A

consists of a fibrous portion and a serous portion

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7
Q

fibrous pericardium

A

tough and anchors the heart and great vessels by a number of attachments

anteriorly - attached to the posterior surface of the sternum by small sternopericardial ligaments

inferiorly - it is fused to the central tendon of the diaphragm

superiorly - it is continuous with the adventitia of the great vessels

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8
Q

serous pericardium (parieta pericardium)

A

thin layers that lines the fibrous portion on the deep (inner surface)

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9
Q

heart muscle

A

myocardium

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10
Q

visceral pericardium/epicardium

A

a thin layer of serous pericardium that lines the mycocardium

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11
Q

pericardial cavity

A

between parietal and visceral layers of serous pericardium

the space contains only a thin film of fluid that allows the 2 layers of serous pericardium to slide easily on each other when the heart contracts

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12
Q

anatomical position of the pericardium

A

pericardium (and therefore the heart_ lies posterior to the sternum and the 2nd-6th costal cartilages; approximately 1/3 lies to the right of the midsternal line and 2/3 lies to the left

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13
Q

oblique pericardial sinus

A

area if reflection between the veins and the base of the heart forms a cul-de-sac of the pericardial cavity

a hand placed under the heart’s apex and moved superiorly slips into the oblique pericardial sinus

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14
Q

transverse pericardial sinus

A

the slit-like passageway of the pericardial cavity between the 2 sites of reflected serous pericardium

the sinus lies anterior to the superior vena cava and posterior to the aorta and pulmonary trunk so a finger placed in the transverse sinus separates the arteries and veins

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15
Q

pericardial sinus development

A

during development, the longitudinal embryonic heart tube invaginates the double-layered pericardial sac (some-what like placing a hot dog in a hot dog bun); the primordial heart tube then “loops” ventrally, bringing the primordial arterial and venous ends of the heart together and creating the primordial transverse pericardial sinus between them; with the growth of the embryo, the veins expand and spread apart, inferiorly and laterally; the pericardium reflected around them forms the boundaries of the oblique pericardial sinus

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16
Q

what supplies most arterial blood to the fibrous and parietal pericardia

A

pericardiacophrenic arteries

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17
Q

pericardiacophrenic arteries

A

branches of the internal thoracic arteries

run with the phrenic nerves anterior to the roots of the lungs

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18
Q

visceral pericardium (epicardium)

A

shares its arterial blood supply with the myocardium via the coronary arteries

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19
Q

phrenic nerves

A

carry sensory fibers from the fibrous and parietal percardia

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20
Q

anterior (sternocostal) heart surface

A

right ventricle

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21
Q

left heart surface

A

left ventricle

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22
Q

right heart surface

A

right atrium

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23
Q

posterior heart surface (base)

A

left atrium

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24
Q

inferir (diaphragamatic_ heart surface

A

left ventricle and a portion of the right ventricle

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25
Q

arterial supply of the heart

A

myocardium (heart muscle) receives its arterial blood supply from the most oxygenated blood in the body directly from the first 2 branches of the aorta, the right and left coronary arteries

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26
Q

right coronary artery

A

passes between the right auricle and the pulmonary trunk to run along the coronary sulcus (atrioventricular sulcus)

gives off the sinuatrial nodal artery which supplies the SA node (part of the heart’s conduction system)

gives off a small right marginal artery, which runs along the surface of the right ventricle

continues along the coronary sulcus providing blood to the right atrium

when it reaches the posterior interventricular sulcus it descends towards the apex of the heart as the posterior interventricular artery

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27
Q

coronary sulcus

A

the groove between the atria and ventricles that encircles the entire heart

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28
Q

posterior interventricular artery

A

gives off the atrioventricular (AV) nodal artery which supplies the AV node (part of the heart’s conduction system)

also supplies both ventricles, posterior 1/3 of interventricular septum, and the atiroventricular (AV) bundle (part of the heart’s conduction system)

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29
Q

left coronary artery

A

very short and upond entering the coronary sulcus, bifurcates into the anterior interventricular artery and the circumflex branch

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30
Q

anterior interventricular artery (left anterior descending of LAD)

A

runs along the anterior interventricular sulcus between the two ventricles, providing blood to both ventricles (anteriorly) and the anterior /3 of the interventricular septum

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31
Q

circumflex artery

A

runs along the coronary sulcus between the left ventricle and atrium, giving off a left marginal branch that supplies the left atrium and posterior aspect of left ventricle

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32
Q

when does most blood flow into the coronary arteries

A

during ventricular relaxation (diastole)

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33
Q

myocardial bridge

A

a band of heart muscle that lies superficial to a coronary artery, istead of deep to it; with a mycocardial bridge, part of a caronary artery dips into and partially deep to the heart muscle and then comes back out again

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34
Q

coronary sinus

A

a wide venous channel running from left to right in the psterior part of the coronary sulcus; it empties directly into the right atrium

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35
Q

great cardiac vein

A

accompanies the anterior interventricular artery and drains the apex, left aspect of the right ventricle and the interventricular septum; the great cardiac vein becomes continuous with the coronary sinus (where the oblique vein of the left atrium enters it)

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36
Q

left marginal and left posterior ventricular veins

A

drain the areas supplied by left marginal and circumflex arteries (all supplied by left coronary artery); the left marginal and left posterior ventricular veins drain into the coronary sinus

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37
Q

middle cardiac vein

A

runs in the posterior interventricular sulcus; the small cardiac vein accompanies the right marginal artery and then runs along the coronary sulcus with the right coronary artery;both veins drain areas supplied by the right coronary artery and empty into the coronary sinus

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38
Q

60-70% of the venous blood drained is returned to the heart via

A

coronary sinus

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39
Q

remaining 30-40% of venous blood from the myocardium either drains into

A

the right atrium or other heart chambers

40
Q

anterior cardiac veins

A

from the anterior surface of the right ventricle cross over the coronary sulcus and enter the right atrium

41
Q

least cardiac veins (or Thebesian veins, or venae cordis minimae)

A

are small (not visible) veins in the wall of the heart that drain diredctly int thee right atrium or any chamber.

42
Q

arteriosclerosis

A

any hardening and loss of elasticity of medium or large arteries

43
Q

atherosclerosis

A

a type of arteriosclerosis but names are someitmes used interchangeably; hardeningof theartery is specifically due to a buildup of fats and cholesterol in and on artery walls, forming plaques that may restrict blood flow

44
Q

cardiac ischema

A

a reduction in blood supply to myocardium usually resulting from atherosclerosis; it may be asymptomacticor may cause chest pain (angina pectoralis)

45
Q

myocardial infaction

A

commonly called a heart attack - death of cardiomyocytes is due to obstruction of myocardium’s blood supply and usually occurs as a result of blockage of a coronary artery or ruptureof an atheroscleoritc plaque

46
Q

right atrium

A

low pressure chamber receiving venous (poorly oxygenated) blood from the SVC, IVC, and coronary sinus

47
Q

pectinate muscle

A

ridges of myocardium in the atrium and auricle

48
Q

crista terminalis

A

band of tissue extending from roof of right atrium to inferior vena cava; is the demarcation between the ridged portion (more anterior and has pectinate muscles) and the sinus venarum (more posterior and smooth)

its superiorend marks the lcoation of the sinuatrial (SA) node

49
Q

coronary sinus

A

small opening on the inner wall; lies just inferior to the location of the atrioventricular (AV) node

50
Q

valve of the IVC (valve of the coronary sinus)

A

remnants of the valve of the sinus venosus in the embryo

51
Q

fossa ovalis

A

depression in the interatrial septum (between left and right atria)

marks the locationof the foramen ovale, which permit oxygenated blood to flow from the right atrium to the left atrium

closure of membranous portion at birth is due to increased pressure in the left atrium

sometimes still patent in adult (congenital atrial septal defect)

52
Q

right ventricle

A

deoxygenated blood fills the right ventricle during ventricular diastole passing through the right AV valve (tricuspid valve - 3 cusps, or “leaflets); most blood passes into the ventricle passively; the reamining blood is forced in by atrium contraction

53
Q

trabeculae carneae

A

elevated ridges of myocardium on the inflow part of the ventricle

54
Q

papillary muscles

A

present in both ventricles, their contraction maintains tension on the chordae tenineae; usually 3 in the right ventricle: anterior (most prominent), septal (small could be absent), and posterior (several small ones, or even absent0

55
Q

chordae tenineae

A

attach to the cusps of the tricuspid valve (bicuspid in left ventricle) to prevent prolapse (eversion) of the valve into the atria during ventricular contraction

56
Q

conus arteriosus

A

smooth outflow tract of right ventricle

57
Q

interventricular septum

A

small upper portion in membranous and larger lower portion is muscular

58
Q

septomarginal trabecula (moderator band)

A

elevation of trabeculae carnae that forms a bridge betwen the interventricular septum and the anterior papullary muscle; only in the right ventricle; bridges conducting system

59
Q

left atrium

A

receives oxygenated blood from the lungs via the 4 pulmonary veins; like the right atrium, it has a smooth part and a ridged part with pectinate muscle

60
Q

left ventricle

A

high pressure chamber receiving highly oxygenated blood from the left atrium as it passes through the left AV valve; similar arrangement ot he right ventricle except that the myocardium is thicker and the left AV valve has 2 cusps (bicuspid or mitral valve); two papillary muscles - anterior and posterior; trabeculae carnae are present on the inflow part of the ventricle

61
Q

blood flow through the heart

A
  1. blood enters the right atrium from the SVC, IVC, and coronary sinus.
  2. blood in the right atrium flows through the right AV valve into the right ventricle.
  3. contraction of the right ventricle forces the pulmonary valve open.
  4. blood flows through the pulmonary valve into the the pulmonary trunk
  5. blood is distributed by the right and left pulmonary arteries to the lungs, where it unloads CO2, and loads O2
  6. blood retruns from the lungs via the pulmonary veins to left atrium.
  7. blood in the left atrium flows through the left AV valve into the left ventricle
  8. contraction of the left ventricle (simultaneous with step 3 above) forces the aortic valve open
  9. blood flows through the aortic valve into the ascending aorta
  10. blood in the aorta is distributed to every organ in the body, where it unloads O2 and loads CO2
  11. . blood returns to the heart via the SVC, IVC, and coronary sinus
62
Q

pulmonary and aortic (semilunar) valves

A

each valce has 3 thin, concave cusps that oppose each other at closure

63
Q

aortic valve

A

has posterior, right and left cusps; coronary arteries arise from the right and left aortic sinuses between the cusps and wall of the ascending aorta

64
Q

pulmonary valve

A

has anterior, right and left cusps

closure of these valves depends on backflow of blood after ventricular ejection

65
Q

normal heart sounds

A

first heard sound “lubb” occurs when the atrioventricular valves close. the second heart sound “dubb” occurs when the aortic and pulmonary semilunar valves close

66
Q

auscultation sites

A

to distinguish an individual valve sounds, listen at a site where the sound is projected by the direction of blood flow:

aortic semilunar valve = right 2nd intercostal space

pulmonary semilunar valve = left 2nd intercostal space

tricuspid valve = left or inferior end of sternum at 5th intervostal space

bicuspid valve = at heart apex in 5th intercostal space

67
Q

conducting system

A

SA node –> AV node –> right and left bundle branches –> purkinje fibers

68
Q

initiation of contraction occurs

A

in the sinuatrial (SA) node (at junction of SVC and right atrium wall); specialized cells have a lower threshold for depolarization and normally depolarize at a rate of ~70 times/min

69
Q

what causes atrial contraction

A

impulse is transmited along muscle fibers of right and left atria

70
Q

what happens after atrial contraction

A

impulse is transmitted to the atroventricular (AV) node located in the interatrial septum, superior to the coronary sinus opening

71
Q

what happens after AV node receives impulse

A

impulse from AV nodes passes through the AV bundle in the membranous part of interventricular septum; AV bundle splits into right and left bundle branches once it reaches the muscular part of the septum

72
Q

how do bundle branches run

A

both bundle branches run inferiorly within the interventricular septum beneath the endocardium to first reach the papillary muscles of each respective ventricle

right bundle branch runs through the septomarginal trabecula (moderator band), to the papillary muscles

left bundle branch runs directly to anterior and poterior papillary muscles

73
Q

what happens with each bundle

A

each bundle divides into a plexus of purkine fibers to direct impulses through the muscular walls of each ventricle for contraction of myocardial cells

74
Q

myocaridal muscle fibers

A

are arranges within the walls of chambers in a swirling manner so contraction occurs in a manner similar to wringing water out of a wash cloth

75
Q

problems resulting from decreasing coronary blood supply to the areas of the conducting system

A

compromise of the coronary artery serving AV node, resulting in anoxia to this region and damage to this node will not permit transmittal of impulses from the atria (“hear block”) - ventricles will contract independently at slower rate than atria

what might happen if areas served by left coronary artery are compromised? left coronary artery will supply the anterior 2/3 of the interventricular septum with bundle branches possibly being affected - asynchronous contraction

76
Q

sympathetic innervation

A

increases heart rate and force of contraction, cuases dilation of coronary arteries

77
Q

parasympathetic innervation

A

decreases heart rate

78
Q

superior mediastinum

A

is bounded superiorly by the thoracic inlet, inferiorly by the transverse thoracic plane, anteriorly by the manubrium of the sternum and posteriorly by vertebral bodies T1-T4

79
Q

from anterior to posterior structure of the superior mediastinum

A
  1. endocrine layer - thymus
  2. vascular layer - veins - brachiocephallic veins and superior part of the SVC; arteries (posterior to veins) - aoritc arch and roots of its major branches (bacriocephalic trunk, left common carotid artery, and left subclavian artery)
  3. respiratory layer - trachea
  4. digestive layer - esophagus
  5. lymphatic layer - thoracic duct

the nervous system does not have its own layer but it is integrated with the vascular, respiratory, and digestive layers; nerves within these layers are th vagus nerves, phreni nerves, and the cardiac plexus

80
Q

thymus

A

a lymphoid gland located posterior to the manubrium; secretes hormones that stimulate the development of T cells; continues to grown until about 5 years of age and then progressively atrophies/involutes

81
Q

brachiocephalic vein

A

are formed in the neck posterior to sternoclavicular joints by union of internal jugular and subclavian veins; left braciocephalic v. - runs obliquely down and behind the manubrium; crosses roots of 3 branches of aortic arch; right brachiocephalic vein unites with the left brachicephalic cein to form the superior vena cava (SVC)

82
Q

superior vena cava (SVC)

A

is formed by union of the right and left brachicephalic veins posterior to the right 1st costal cartilage
returns blood to heart from all structures above diaphragm except for the heart and lungs

descends vertically and ends in the right atrium

lies to the right of the ascending aorta and to the left of right phrenic nerve

receives the azygos vein before piercing the fibrous pericardium

83
Q

aortic arch

A

the continuation of the ascending aorta at the sternal angle; gives off 3 arteries superiorly (brachiocephalic trunk, left common carotid artery, and the left subclavian artery); lies superior to the right pulmonary artery and anterior to the tracheal bifurcation; ligamentum arteriosum (a remnant of ductus arteriosus in the fetus) is between its inferior surface and the left pulmonary artery; during fetal life, the ductus arteriosus shunts blood from the pulmonary trunk directly into the aortic arch, thus bypassing the lungs; passes over the root of th eleft lung; its distal portion lies to the left of the trachea and esophagus; ends as the thoracic (descending) aorta at the sternal angle

84
Q

vagus nerve

A

provide parasympathetic innervation to all thoraci and most abdominal viscera

85
Q

right vagus nerve

A

enters superior mediastinum anterior to right subclavian artery; descends on the right side of the trachea; passes posterior to the right braciocephalic vein and the SVC; enter the middle mediastinum posterior to the root of the right lung

86
Q

left vagus nerve

A

enters superior mediastinum between the left common carotid and left subclavian arteries; descends to left side of aoritc arch; gives off the left recurrent laryngeal nerves just below the aortic arch; enters the middle mediastinum posterior ot the root of the left lung

87
Q

left recurrent laryngeal nerve

A

loops around the aortic arch; ascends in the tracheoesophageal groove between the trachea and esophagus to reach the layrnx in the neck; note that the right recurrent laryngeal nerve is not located in the mediastinum; it is formed as the right vagus nerve passes anterior to the right subclavian artery in the neck

88
Q

phrenic nerves

A

ventral rami of C3-C5 spinal cord segments

89
Q

right phrenic nerve

A

enters superior mediastinum lateral to the right brachiocephalic vein; lies on the right side of SVC; enters middle mediastinum on pericardial surface of right atrium and runs anterior to the root of the right lung

90
Q

left phrenic nerve

A

enters superior mediastinum adjacent to the left subclavian artery; lies posterior to the left brachiocephalic vein; crosses the left side of the aortic arch, anterior to vagus nerve; enters the middle mediastinum anterior to the root of the left lung and runs on the pericardial surface of the left ventricle

91
Q

superficial and deep plexuses

A

are autonomic and both receive fibers from the vagus nerves and sympathetic trunks

92
Q

superficial plexus

A

lies on the concave inferior surface of the aortic arch and is the smaller of the 2 plexuses

93
Q

deep plexus

A

lies on the anterior surface of the tracheal bifurcation

94
Q

components of the cardiac plexus

A

parasympathetic from vagus nerve are preganglionic fibers, which synapse with postganglionic cells bodies in the heart; visceral afferents from chemo- and baroreceptors in aortic arch follow parasympathics of the vagus nerve (CN X) back to the brain

sympathetic from cervical and thoracic cardia nerves are postganglionic fibers; preganglionics are from 4 upper thoracic spinal segments; synapse occurs with postganglionic neurons in the sympathetic trunk (superior cervical through T4 chain ganglia); visceral afferents carrying pain sensation from the heart follow sympagthetics back to T1-T4 spinal cord levels; pain is referred by the CNS to somatic regions innervated by the same spinal cord levels

95
Q

trachea

A

lies anterior to the esophagus
bifurcates into right and left main bronchi at the sternal angle; proximal part of aortic arch lies anterior to trachea, but distal part lies to left; brachiocephalic trunk crosses the trachea anteriorly to the right and the left common carotid crosses to the left, forming a V-shape

96
Q

esophagus

A

enters superior mediastinum posterior to the trachea and anterior to the vertebral bodies; left surface is related to the aortic arch; thoracic duct lies at its left posterior surface

97
Q

thoracic duct

A

lies posteriorly and to left of the esophagus; begins in abdomen as the cisterna chyli; drains lymph from the body regions below the diaphragm and the left side of body above the diaphragm; ends in the neck at the venous angle between the left internal jugular vein and the left subclavian vein.

gross anatomy unit 2 (8 decks)

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