The thorax is the region of the body between the neck and the abdomen, also known as the chest. It contains vital organs such as the heart and lungs, as well as other structures like the ribs, sternum (breastbone), and thoracic vertebrae.

1. The Thorax
5/7/2024

2. Outline
 Introduction
 Thoracic wall
 Skeleton of thorax
 Muscles of the thoracic wall
 Nerves of the thoracic wall
 Vasculature of the thoracic wall
 Thoracic cavity
 Pleurae
 Lungs
 Mediastinum
 pericardium
 Heart
 Great vessels
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3. 5/7/2024

4. Introduction
 Thorax is the superior part of trunk between neck and
abdomen
 Contains heart and great vessels, lungs, thymus, trachea
and esophagus
 Clinical examination of chest requires a good knowledge of
its structure and vital organs it contains
Function
 Provides a protective cage around the vital organs (heart,
lungs, great blood vessels)
 Provides support for the shoulder girdles
 Bony attachment points for muscles of the back, chest and
shoulders
 Helps for breathing to happen
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5. Thoracic wall
 The thoracic wall consists of skin, fascia, nerves, vessels,
muscles, and bones
 The superior thoracic aperture bordered by vertebra TI, 1st
rib, and the manubrium of sternum
 The inferior thoracic aperture bordered by vertebra T12,
12th rib, the end of rib 11, the costal margin, and the xiphoid
process of sternum
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6. Skeleton of thorax
 Forms:
osteocartilaginous
thoracic cage
 Includes:
12 pairs of ribs and
costal cartilages :-
Form lateral boundaries
12 thoracic vertebrae
and intervertebral
discs
 Sternum:- form
anterior boundary
with costal cartilages
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7. Skeleton of thorax: The Sternum
 Flat bone
 lies in the anterior midline
of the thorax
 It consists of three fused
bones
Manubrium
Body
Xiphoid process
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8. The Sternum
 Manubrium
 Located at level of T3-T4
 Has Jugular (sternal) notch
 Articulate with clavicle at Clavicular
facets
 Sternal Angle –articulate 2nd rib
which is a major surface landmark
used by clinicians
 Lies opposite 2nd costal cartilage:
guide to numbering of ribs
 Body
 Articulates with ribs 2-7
 Located at level of T5-T9
 Xiphoid process
• Sword-shaped
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9. The Ribs
 12 pairs
 1-7th (True ribs)- have
direct attachment to
sternum
 Ribs 8-10th - (False ribs)– have
indirect attachment to
sternum
 Ribs 11-12th- have no
anterior
attachments - floating ribs
Structurally:
 Typical Ribs
 Ribs # 3-9
 Atypical Ribs
 Ribs #1, 2, 10, 11, 12
Intercostal spaces lie between
adjacent ribs and are filled by
intercostal muscles
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10. Rib Anatomy
 Typical Ribs have
 Head (2 facets)
 Neck
 Tubercle
 Angle
 Shaft
 Costal Groove:-
on inferior border
 Costal cartilages
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11.  Atypical Ribs
 #1-short, wider,
posses
subclavian groove
, no angle
 2nd rib- has
tuberosity for
serratus anterior
 1st ,10th &12th ribs
have only one
facet on their
heads and
articulate with a
single vertebra
 rib 11, 12- are
short and have no
neck or tubercle 5/7/2024

12. Thoracic Vertebrae
The thoracic vertebrae have the following features
 Body= heart shaped
 Vertebral arch (neural arch)=around vertebral
foramen: composed of
1-pedicle (joining body to transverse process)
2-transverse process (lateral projection of arch)
3-lamina (joining transverse and spinous process )
4- the spinous process (posterior projection ,point
inferiorly)
5. Articular process
 Transverse Costal Facets :on the transverse
process.
 vertebral foramen: circular passage enclosed in
Vertebral arch and contains spinal cord 5/7/2024

13. 5/7/2024

14. Muscles of the thoracic wall
 Intercostal spaces contain 3 layers of muscles:
External intercostal muscles
Internal intercostal muscles
Innermost intercostal muscles
All are innervated by intercostal nerve
All arise from inferior border of the rib above and inserted in
to superior border of the rib below
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15. Thoracic Muscles
External Intercostals
Not complete anteriorly
(anterior intercostal
membrane replaces at
Costochondral joints)
Fibers run OBLIQUE
(downward and forward)
Aid in Inspiration (lift
ribcage, increase
dimensions)
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16. Internal intercostals
 Occupy intercostal
spaces from sternum to
angles of ribs
 posteriorly replaced by
internal intercostal
membranes
 Action - draws ribs
together aids in
respiration
 Muscle fibers project
superiorly in a posterior
to anterior direction
(perpendicular to fibers of
external intercostals) 5/7/2024

17. Innermost intercostal
 Similar to internal
intercostal; deep
portions of them
 Separated from
internal intercostals by
intercostal nerves and
vessels
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18. Subcostal muscles
 Variable in size and
shape
 Extend from internal
surface of angle of
ribs to internal surface
of the rib below
crossing one or two
intercostal spaces
 Act as internal
intercostal mm
5/7/2024

19. Transversus thoracis
 Origin - from the
back of the sternum
and the xiphoid
process
 Insertion – on to
costochondral
junctions of ribs 3-6
 Weakly depress ribs
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20. Thoracic Muscles cont’ed
 Serratus posterior:- innervated by intercostal nerve
 Serratus posterior superior
 O-Spinous process of C6 ---T2
 I- Rib 2—5 (lateral to angle of rib)
 A- elevate ribs
 Serratus posterior inferior
 O-spinous process of T11---L 2
 I- Rib 9—12 (lateral to angle of rib)
 A- depress ribs
 Levator costarum (innervated by posterior rami)
 O-tip of transverse process of C7---T11
 I-lateral to tubercle of rib below
 elevate ribs
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21. 5/7/2024

22. Nerves of thoracic wall
 12 pairs of thoracic spinal nerves
 Leave spinal cord through corresponding intervertebral
foramina and divide into 2 branches
Posterior (dorsal) rami: innervate muscles, bones, joints
and skin of the back
Anterior (ventral) rami: innervate intercostal
musculature, periosteum of the ribs and skin of the thorax
 Ventral rami of T1-T11=intercostal nerves
 Ventral ramus of T12 = subcostal nerve
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23. Branches
• Muscular branch
• Collateral
 supply intercostal
muscles
• Cutaneous
 anterior + lateral
• Communicating
 connect each nerve to
sympathetic trunk
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24. Vasculature of thoracic wall Intercostal arteries
 Intercostal vessels run in the costal groove
 Posterior intercostal arteries
1st & 2nd - arise from superior/supreme intercostal
artery (a branch of costocervical trunk of subclavian
artery)
3rd -11th - branches of the thoracic aorta
Accompanies intercostal nerve
Accompany dorsal ramus to supply spinal cord, vertebrae,
muscles and skin
 Anterior intercostal arteries
1st – 6th – from internal thoracic
7th- 9th – from musculophrenic
10th & 11th – have no anterior intercostal
Anastomose with the posterior vessels in the
intercostal spaces around the midclavicular line
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25. 5/7/2024

26. 5/7/2024

27. Intercostal veins
 Anterior intercostal veins are tributaries of internal
thoracic veins
 The posterior intercostal veins drain into azygos and
hemiazygos system
 The superior veins drain into the brachiocephalic veins
 Right
1st – right brachiocephalic vein
2nd , 3rd & 4th - join to form superior intercostal which
drain into azygos vein
5th - 11th & subcostal – drain to azygos vein
 Left
1st – left brachiocephalic vein
2nd , 3rd & 4th – join to form superior intercostal which
drain into left brachiocephalic
5th - 8th – drain into accessory hemiazygos vein
9th -11th & subcostal – drain into hemiazygos vein
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28. 5/7/2024

29. 5/7/2024

30. Lymph drainage
 Follows arteries of intercostal space
 Anterior vessels drain to parasternal lymph node
(anterior IC node)
 Posterior vessels drain to paravertebral lymph
node (posterior IC node)
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31. The Thoracic Cavity
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32. Thoracic cavity
 Cone shaped space enclosed by the thoracic walls
 Has narrow superior aperture (thoracic inlet) and wide
inferior aperture (thoracic outlet)
 Thoracic cavity is divided into 3 divisions
• Two pleural cavities: occupy lateral part and
contain the lungs
• The mediastinum: the space between lungs and
pleurae
 The mediastinum contains
• the pericardium & the heart and associated great
vessels
• trachea, esophagus, vagus nerves, phrenic nerves,
thoracic duct, azygos veins, thymus, sympathetic
trunk, etc 5/7/2024

33. 5/7/2024

34. 5/7/2024

35. Pleurae and
Lungs
Pleurae
 Each lung is invested by a
pleura
 The pleural has two parts
The visceral pleura :- it is
adherent to all surfaces of
the lung. Insensitive to
pain
The parietal pleura:- lines
the pulmonary cavities,
adhering to the thoracic
wall, the mediastinum,
and the diaphragm
 The two layers are
continuous around hilum 5/7/2024

36. 1-Pleural Cavities
Inferior margin =
adjacent to T12 in
Posterior Midline
At Rib 10 at Midaxillary
line
At Rib 8 at Midclavicular
line
To Xiphosternal joint
anteriorly
Superior margin=
transverse process of T1
posteriorly i.e. do not
extend above rib 1 due to
obliquity of thoracic inlet.
Anterolateraly in cervix
about 2.5 cm above
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37. Innervation and blood supply of the pleura
 Parietal pleura
Cervical, costal and peripheral diaphragmatic portion -
intercostal nerves and vessels
Central portion of diaphragmatic and mediastinal – phrenic
nerve and internal thoracic & musculophrenic vessels
Sensitive to pain
Venous drainage - intercostal veins, internal thoracic and
azygos
Lymphatics – intercostal, internal mammary, diaphragmatic
& posterior mediastinal lymph nodes
 Visceral pleura
Sympathetic nerves derived from T4 & T5
insensitive to pain
vasculature and lymphatics are similar to lung
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38. Clinical correlates
 Pneumothorax – presence of air in the pleural
cavity
 Haemothorax - when blood accumulates
 Hydrothorax - when fluid accumulates
 Pleurisy – inflammation of the pleura  rough
surface  rubbing  sound
5/7/2024

39. Pleuricentesis (pleural tap)
• Aspiration of fluid from the
pleural cavity
• Mostly done in the 6th
intercostal space at mid
axillary line
•The needle should be
inserted through middle part of
intercostal space to avoid
injury to neurovascular bundle
5/7/2024

40. LUNG
 The lungs are the vital
organs of respiration
 Located in Pleural
Compartments
 Lateral to Mediastinum
 Spongy in texture and
pink in color in young
but mottled black by
carbon particles in
adults
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41. LUNG
Has :
Apex= posterior to
clavicle
 Three surface
 Diaphragmatic
 Costal Surface
 Mediastinal surface
 Three border
 Anterior, posterior &
inferior border
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42. The base (diaphragmatic surface)
Semilunar and concave
Rests on diaphragm which separates the right lung from
right lobe of liver and left lung from fundus of stomach
It is found at the level of
 the 6th costal cartilage in the mid-clavicular line
 the 8th costal cartilage in the mid-axillary line
 rib 10 dorsally
 Due to the position of the liver, the base of the right lung is
broader than that of the left lung
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43. Lungs: anterior view
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44. The root of the lung
 The root of the lung is formed by the structures entering and emerging
from the lung at its hilum
 Lie at level of T5-T7
 Pulmonary vessel
 Bronchopulmonary lymph nodes
 Bronchus
 Pulmonary plexus
 The hilum of the lung is the area on the medial surface of each lung.
5/7/2024

45. LUNG LOBES
 The right lung has three
lobes, the left lung has
two
For right lung horizontal
fissure divide superior
and middle lobe and
oblique fissure between
middle and inferior
lobes
Left lung has a superior
and inferior lobe divided
by an oblique fissure
 The right lung is larger
and heavier than the
left, but it is shorter and
wider because the right
dome of the diaphragm
is higher and the heart
5/7/2024

46. LUNG
 The anterior margin of
the right lung is
relatively straight,
whereas this margin of
the left lung has a
cardiac notch
 Examination of the
superior lobe is done on
the anterior chest wall,
whereas examination of
the inferior lobe is done
posteriorly below the
scapula
5/7/2024

47. Right lung Left lung
Size Larger and heavier
(700gm)
Small and lighter
(600gm)
Length and width Shorter & broader Longer and narrower
Anterior border Straight Cardiac notch &
lingula
Lobes and fissures Three lobes & two
fissures
Two lobes & one
fissure
Arterial supply One bronchial
artery
Two bronchial
arteries
Differences between right and left lung
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48. 5/7/2024

49. 5/7/2024

50. 5/7/2024

51. Trachea and Bronchi
 The trachea bifurcate in to two main bronchi (primary
bronchi), at the level of the sternal angle
 The right main bronchus is wider, shorter, and runs
more vertically than the left main bronchus
 Inhaled particles tend to pass more frequently to
the right lung
5/7/2024

52. 5/7/2024

53. Bronchial Tree
 Primary (main) Bronchi
 Bifurcation of trachea at
the level of T4
 Cartilage plates replace
rings
 Posterior to pulmonary
vessels
 Right is wider, vertical,
shorter
 Secondary (lobar) Bronchi
 Divisions of each primary
bronchi
 Right lung has 3, Left has
2
 Tertiary (segmental) 5/7/2024

54. Bronchial Tree cont’ed
 Bronchioles
 Terminal
Bronchioles
 Respiratory
Bronchioles
 Alveolar Ducts
 Alveolar Sacs is
 Alveoli
5/7/2024

55. 5/7/2024

56. Bronchopulmonary segments
 pyramidal section of a lung served with one tertiary
bronchus
 base toward visceral pleura & apex toward hilum
 The right lung has 10 bronchopulmonary segments and
the left lung has 9
 Each segment is surrounded by connective tissue;
independent respiratory units
 Limit the spread of some diseases within the lung, because
infections do not easily cross the connective tissue partitions
between them
5/7/2024

57. Bronchopulmonary segments
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58. Bronchopulmonary segments
Right lung
I. Upper
I. Apical
II. Anterior
III. Posterior
II. Middle
I. Medial
II. Lateral
III. Lower
I. Apical
II. Anterior basal
III. Posterior basal
IV. Medial basal
V. Lateral basal
Left lung
I. Upper
I. Apicoposterior
II. Anterior
III. Superior lingular
IV. Inferior lingular
II. Lower
I. Apical
II. Anterior basal
III. Posterior basal
IV. Medial basal
V. Lateral basal
5/7/2024

59. Vasculature and Nerves of Lungs and
Pleurae
 Each lung has a large pulmonary artery supplying blood
to it and two pulmonary veins draining blood from it.
5/7/2024

60. Pulmonary artery
 Two in number; one for
each lung
 derived from the bifurcated
pulmonary trunk
 Carry poorly oxygenated
blood to lungs for
oxygenation
 divide into lobar branches
and then tertiary
branches
5/7/2024

61. Pulmonary veins
 Four in number; two for
each lung
 Carry well-oxygenated
blood
 Begin from pulmonary
capillaries
5/7/2024

62. Bronchial Vasculature
The bronchial arteries
 a single right bronchial
artery normally arises from
the third posterior intercostal
artery
 two left bronchial arteries
arise from thoracic aorta
 supply blood to the
structures making up the root
of the lungs, the supporting
tissues of the lung, and the
visceral pleura
The bronchial veins
drain into:
 either the pulmonary
veins
 Or into the azygos
vein on the right or
into hemiazygos vein
on the left
Lymphatic
 are extensive and follow
the vascular tree
 At the hilus of the lung,
they are filtered by the
pulmonary lymph nodes
and then enter the right
lymphatic duct, on the
5/7/2024

63. Nerves of the Lungs
• Supplied by bronchopulmonary plexus
 Parasympathetic fibers – from vagus
 motor to the smooth muscle of the bronchial tree
(bronchoconstrictor)
 inhibitory to the pulmonary vessels (vasodilator)
 secretory to the glands of the bronchial tree
(secretomotor).
 Sympathetic fibers - from T2-T5
 vasomotor to arterial system (vasoconstriction)
 Bronchodilator
 Inhibitory to bronchial glands
5/7/2024

64. surface marking of the lung
Lungs inferior margin is 2 ribs superior to pleural
cavity (T10-posteriorly, rib 8 –mid axillary and rib 6-
mid clavicle)
Apex superior and posterior to the clavicles
5/7/2024

65. The Mediastinum
 between the two pleural
sacs-
 Division
 Superior:- from superior
thoracic aperture to
sternal angle
 Thymus , great
vessels , thoracic
duct, trachea,
esophagus, vagus
nerves, left recurrent
laryngeal nerve and
phrenic nerves.
 Inferior :- from sternal
angle to diaphragm 5/7/2024

66. Contents of superior mediastinum
5/7/2024

67. Mediastinum continued
Inferior mediastinum
 Anterior mediastinum –
b/n pericardial sac and
sternum
 contains thymus,
lymph nodes, fat, and
connective tissue
 Middle mediastinum – occupied
by pericardial sac, heart and
roots of great vessels
 Posterior mediastinum –b/n
lower eight thoracic vertebral
bodies and pericardial sac ,
posterior portion of diaphragm
inferiorly
 esophagus, thoracic aorta,
azygos and hemiazygos
veins, thoracic duct, vagus
5/7/2024

68. Thymus
 The most anterior structure of the superior mediastinum
 Prominent in children, steadily grows until puberty (reach
maximum size), after puberty involutes (fat and fibrous
tissues)
 From lower part of the thyroid gland to the 4th costal
cartilage
 Has two lobes
 Site of proliferation of T-lymphocytes
 Arterial supply – inferior thyroid, internal thoracic, anterior
intercostal
 Venous drainage – to left brachiocephalic, internal thoracic &
anterior intercostal
 Lymphatics – parasternal, brachiocephalic & trachiobronchial
 Nerves – sympathetic – vasomotor
5/7/2024

69. Great blood vessels
Brachiocephalic vein
 Formed by union of internal
jugular vein and subclavian
vein behind sternoclavicular
joint
 Left brachiocephalic vein is
two times longer than the
right because it passes from
the left to the right side
Tributaries of BCV
 both right & left –
internal thoracic vein,
inferior thyroid vein
 Left only – left superior
intercostal vein, thoracic
duct
 Right only – right
5/7/2024

70. 5/7/2024

71. Superior vena cava (SVC)
• Formed by union of
right and left
brachiocephalic veins
behind the right first
costal cartilage near
to the sternum
• Returns blood from all
structures superior to
the diaphragm,
except the lungs and
heart
• Ends at the level of
the 3rd costal
cartilage, where it 5/7/2024

72. Aorta
• Three parts –
ascending aorta, arch
of aorta & descending
aorta
Ascending aorta
• covered in the pericardium
 Begin behind left half
of sternum at the level
of 3rd costal cartilage
 Ends at the level of
right 2nd costal
cartilage
The right and left
5/7/2024

73. Arch of aorta
• Begin in the right
2nd costal cartilage,
directs upward,
back ward and to
the left
• Ends at the lower
border of T4 to be
continuous with the
descending aorta
Branches
 Brachiocephalic
trunk
 Left common
carotid
 left subclavian 5/7/2024

74. Thoracic aorta
 Continuation of arch of aorta
 Branches
 Posterior intercostal
 Subcostal
 Phrenic arteries
 Esophageal
 Bronchial
 Pericardial
5/7/2024

75. Trachea
 Begins below the
larynx (cricoid
cartilage) at the level
of C6
 About 10 cm long
and 2.5 cm wide
 Partly in the neck and
partly in the superior
mediastinum
 bifurcates at the level
of T4/5 (sternal
angle)
 lies in the median
plane and inferiorly it
is displaced to the
right by the aortic
5/7/2024

76. Neurovasculature
Blood supply - branches from inferior thyroid artery &
bronchial artery
Venous drainage – left brachiocephalic through inferior
thyroid vein
Lymphatic – pretracheal and paratracheal lymph nodes
Nerve supply
 Parasympathetic - vagus through recurrent laryngeal nerve;
secretomotor to glands and bronchoconstrictors
 Sympathetic trunk – bronchodilator and vasoconstrictors
5/7/2024

77. Phrenic nerve
 Got branch from cervical
plexus
 Root - ventral rami of C3,
C4 & C5
 Mixed nerve
 Motor - to diaphragm
 Sensory – to fibrous and
parietal layer of serous
pericardium, mediastinal
& diaphragmatic pleura,
diaphragmatic
peritoneum & abdominal
viscera (liver, gall
bladder & suprarenal
gland)
5/7/2024

78. Vagus nerve
 The tenth cranial nerve
originating from medulla
oblongata
 Enters superior mediastinum
posterior to sternoclavicular
joint and brachiocephalic vein
 gives rise to recurrent
laryngeal nerve and continues
into abdomen
 Give branch to pulmonary
plexus, esophageal plexus,
and cardiac plexus
 Recurrent laryngeal nerve
innervate trachea , esophagus
and larynx
5/7/2024

79. 5/7/2024

80. Middle mediastinum
Boundary
• superior - imaginary line
• Inferior- diaphragm
• Right and left lateral –
corresponding Mediastinal
surfaces of pleura
• Anterior – anterior mediastinum
and part of pleura
• Posterior – posterior
mediastinum
Contents
• The heart and the pericardium
• Great vessels – SVC, IVC,
Pulmonary trunk & veins, part of
aorta, parts of the phrenic nerve
5/7/2024

81. Pericardium
 A double-walled fibroserous sac that encloses the heart
and roots of great vessels
 Parts: two
 fibrous pericardium
 The loose fitting outer layer of the sac
 This tough, dense connective tissue layer protects the heart;
anchors the heart; and prevents sudden overfilling
 Serous pericardium
 Internal double-layered serous membrane
 a closed sac sandwiched between the fibrous pericardium
and the heart
 Has two layers are
 Parietal layer
 Visceral layer
 The pericardial cavity is the potential space between
parietal and visceral layers . It contains a thin film of
serous fluid that enables the heart to move and beat in a
frictionless environment
5/7/2024

82. Blood supply and innervation
A. Fibrous and Parietal pericardium
A. Arteries – pericardiophrenic (main), musculophrenic art.
B. Veins – to pericardiophrenic & azygos vein
C. Nerve – phrenic; sensitive to pain
B. Visceral pericardium
A. Artery – coronary
B. Vein – coronary
C. Nerve – autonomic nerves of heart; not sensitive to pain
5/7/2024

83. Clinical correlates
 Pericarditis - inflammation of the pericardium
 hinders production of serous fluid causing the heart to
rub
 Cardiac tamponade - inflammatory fluid seep into
the pericardial cavity
 since fibrous pericardium is tough and inelastic it
compress the heart and limit its ability to pump blood
 Pericardial effusion – collection of fluid in
pericardial cavity
 Pericardiocentesis - removal of fluid
 puncture is at left 5th/6th intercostal space or between
xiphoid process and left side of infrasternal angle,
needle inserted superoposteriorly
5/7/2024

84. The Heart
 The heart is a muscular
pumping organ with two
functions:-
o Its right side receives
oxygen poor blood from
the body tissues and then
pumps it to the lungs
o Its left side receives
oxygenated blood from
the lungs and then pumps
it to the body
5/7/2024

85. Size, location and position of heart
 The heart is about the size
of a fist
 It weighs between 250 - 350
grams
 Located in the middle
mediastinum, anterior to the
vertebral column & posterior
to the sternum
 It extends from the 2nd rib to
5th intercostal space
 Two thirds of the heart lies
to the left of the mid- sternal
line
5/7/2024

86. Heart Chambers
 The heart has four
chambers
 Two atria
 Two ventricles
 The atria lie above and
behind ventricles
 Upper part of each atrium
has an appendage called
auricle
 The chambers are
separated by
 Interatrial septum
 Interventricular septum
Atria
Ventricles Septum
5/7/2024

87. Heart cont’ed
Shape
• 3 sided pyramid with
apex, base and 4 borders
and 4 surfaces
 The apex
• lies in left 5th intercostal
space just medial to
midclavicular line
• formed by left ventricle
 The base
• At vertebral levels of T6 –
T9
• Forms the posterior
surface
• Formed mainly by left
atrium and small part of
5/7/2024

88. Heart cont’ed
Borders
Right – formed by right
atrium
Left –formed mainly by
left ventricle and
partly by left auricle
Inferior – formed mainly
by right ventricle
Superior – formed by
two atria
5/7/2024

89. Surfaces
 Diaphragmatic (inferior)
surface
• Rests on central tendon
of diaphragm
• formed by left ventricle
(left 2/3) and right
ventricle (right 1/3)
 Sternocostal (anterior)
surface
• Formed mainly by right
atrium and right ventricle;
and partly by left ventricle
and left auricle
 Pulmonary surface
• Formed by left and right
ventricle
5/7/2024

90. Right atrium
 Receives venous blood from
the body through SVC, IVC
and coronary sinus and pumps
it to right ventricle
 Upper end is prolonged to left
to form right auricles
 Sulcus terminalis - a shallow
groove along right border run
from SVC to IVC vertically
 Produced by internal muscular
elevation (cristae terminalis )
 Upper end is land mark of SA
node
IVC
5/7/2024

91. Right atrium: internal features
 The interior of the right
atrium is divided into two
continuous spaces.
 The smooth posterior part
(sinus venarum)
 SVC & IVC opens into
it
 Coronary sinus opens
between IVC orifice and
right AV orifice
 The rough anterior part
(pectinate part)
 A series pectinate
muscles
 Arise from crista
terminalis and run
towards AV orifice
5/7/2024

92. Right atrium: internal features
 The Interatrial septum
 Separate the atria
 Presents, fossa ovalis
 Remnant of foramen
ovale of the fetal
heart
 limbus fossa ovalis a
prominent margin of
fossa ovalis
5/7/2024

93. Right ventricle
 Receive blood from right
atrium and pump into
pulmonary trunk
 Superiorly tapers into a
cone, conus arteriosus
(infundibulum)
 Internal structure
 Outflow part – smooth,
pulmonary trunk arise,
separated from inflow part
by supraventricular crest
 Inflow part – rough due to
muscular ridges called
trabeculae carneae
5/7/2024

94. Right ventricle
 Papillary muscles
• Conical projections
arise from ventricular
wall whose free ends
are for chordae
tendineae
• Three: anterior,
posterior & septal
• Contract before
contraction of ventricle,
tightening tendinous
cords and drawing
cusps together
5/7/2024

95. Interventricular septum
• Partition between
ventricles
• Composed of
membranous and
muscular parts
• Membranous –
superoposterior,
thin, continuous with
fibrous skeleton
• Muscular part –
thick, bulges to the
right
5/7/2024

96. Septo marginal band (moderator band)
• Muscular bundle
runs from
interventricular
septum to base of
anterior papillary
muscle
• Carries part of the
right bundle of the
AV bundle of
conducting system
• Facilitate
conduction time
allowing
contraction of the
papillary muscle
before contraction
of ventricle wall
5/7/2024

97. Left atrium
 Blood enters the left
atrium via four veins
 2 Right and 2 left
pulmonary veins
 Thicker than right
 Interior
 large smooth part and
small muscular part
 pectinate muscles are
found in the auricle
Left
pulmonary
veins
5/7/2024

98. Posterior aspect of heart
5/7/2024

99. Left Ventricle
 Receive blood from
left atrium & pumps
into the aorta
 The walls of the left
ventricle are 2-3
times thicker than
that of the right
ventricle
 Due to the work load
5/7/2024

100. Internal structure
 The cavity is circular
and longer than the
right
 smooth upper part and
rough lower part
 trabeculae carneae are
finer and more
numerous than the right
 Papillary muscles: two;
anterior and posterior
 Smooth walled
posterosuperior part –
aortic vestibule, leads to
aortic orifice
Left Ventricle: Internal structure
5/7/2024

101. Heart Valves
 Heart valves maintain a
one-way flow of blood
 Type:- two main type
 Atrioventricular
 Semilunar
 Valves open and close in
response to differences in
blood pressure
Bicuspid
(mitral)
valve
Tricuspid
valve
Aortic
valve
Pulmonary
valve
5/7/2024

102. Heart Valves
5/7/2024

103. Atrioventricular (AV) Valves
 located at each atrio-
ventricular junction
A. The right AV valve
(tricuspid) has three
flexible cusps
- anterior, posterior &
septal
B. The left AV valve
(bicuspid) has two flexible
cusps
- anterior and posterior
 The cusps are flaps of
endocardium reinforced by
connective tissue
 Attached to each of the AV
valve flaps are tiny cords 5/7/2024

104. 5/7/2024

105. Components of the AV valve
 Fibrous ring – part of the fibrous skeleton of the
heart surrounding AV orifice; resist dilation
 Cusps – projection of the endocardium
• has attached (to fibrous ring) and free border
• two surfaces
• atrial – smooth
• ventricular – rough
 Chordae tendineae - connect the free ventricular
ends of cusps with the apex of papillary muscles
• Prevents separation and inversion of the cusps
during systole
 Papillary muscles – projection of the myocardium of
the ventricle
5/7/2024

106. The AV valve
 Blood flows into the atria
& then through the open
AV valves into the
ventricles
 When the atria contract,
force additional blood
into the ventricles
through open AV valve
 When the ventricles
begin to contract, intra-
ventricular pressure
rises forcing blood
superiorly against the
valve flaps
 The chordae tendonae
and the papillary
muscles anchor the
5/7/2024

107. Semilunar (SL) Valves
 Found at the bases of the large arteries exiting the
ventricles
 The aortic and pulmonary semilunar valves
 pulmonary valve is B/n pulmonary trunk into the right
ventricle.
 aortic valve- B/n aorta and the left ventricle
 Each semilunar valve is made up of three pocket like
cusps
Anterior/posterior, right & left
 Concave superiorly
 Spaces between dilated wall of the vessel and each cusp
– sinuses (pulmonary & aortic)
 Blood in sinuses prevents cusps from sticking to wall of
the vessel
5/7/2024

108. Semilunar (SL) Valves
5/7/2024

109. Heart Sounds
 The closing of the heart valves causes vibrations in the
adjacent blood and heart walls that account for the familiar
“lub-dub” sounds of the heartbeat
 The “lub” is produced by the closing of the AV valves at
ventricle contract
 The “dup” is produced by the closing of the semilunar
valves at ventricle relax
 Sounds are heard away from the valves in the direction of
the blood flow
5/7/2024

110. Surface markings of the valves and auscultation
areas
Valve (diameter) Surface marking auscultation area
Pulmonary (2.5 cm) Upper border of 3rd left
costal cart. near sternum
sternal end of 2nd right
intercostal space
Aortic
(2.5 cm)
Behind left half of
sternum at the level of
medial end of 3rd
intercostal space
Sternal end of 2nd right
intercostal space
Mitral
(3 cm)
Behind the left half of
sternum opposite to 4th
costal cartilage
5th left intercostal space
(cardiac apex) at
midclavicular line
Tricuspid
(4 cm)
Behind the right half of
sternum opposite to 4th
and 5th intercostal
space
5th right intercostal
space near sternal
body
5/7/2024

111. Surface markings of the valves
and auscultation areas
5/7/2024

112. Fibrous Skeleton of the heart
 Is a complex framework of dense collagen forming
four fibrous rings that surround the orifices of the
valves
 Lies in the plane between the atria and the
ventricles surrounding the four valves
 Composed of dense connective tissue
 Function
 Anchors the valve cusps
 Prevents over dilation of the valve openings
 Insertion for the bundles of cardiac muscle in the atria and
ventricles
 Blocks the direct spread of electrical impulses from the
5/7/2024

113. Layers of the Heart Wall
 The heart wall is composed of three layers (superficial to deep)
o Epicardium
o Myocardium
o Endocardium
 All three layers are richly supplied with blood vessels
Epicardium – outer layer
 is the visceral layer of the serous pericardium
 often infiltrated with fat, especially in older people
Myocardium – middle layer
 Layer of cardiac muscle forming the bulk of the heart
 Elongated, circularly and spirally arranged muscle
cells squeeze the blood though the heart
5/7/2024

114. The endocardium – inner layer
 Is a glistening white sheet of endothelium (squamous
epithelium) resting on a thin layer of connective tissue
 Located on the inner myocardial surface, it lines the
heart chambers and covers the connective tissue
skeleton of the valves
 The endocardium is continuous with the endothelial
linings of the blood vessels leaving and entering the
heart
5/7/2024

115. Conducting System of the Heart
Contains specialized cardiac muscle cells and
highly specialized conducting fibers
coordinates the cardiac cycle
5/7/2024

116. The components of the conducting system
 Sinoatrial (SA) node
 Location:-below the entrance of the SVC
 Initiates and regulates the impulses for contraction
 The heart’s own pacemaker
 generate 70-80 impulses per minute
 Atrioventricular (AV) node
 Located in the interatrial septum near the
opening of the coronary sinus
Transmit action potential to the
atrioventricular AV) bundle
5/7/2024

117.  Atrioventricular bundle (AV bundle):-
The only pathway for impulses from the atria to the
ventricles,
Also called the bundle of His.
Located in upper interventricular septum
It transmits impulses to the right and left bundle
branches
 Purkinje fibers:-
Transmit impulses to the
papillary muscles and
walls of the ventricles
5/7/2024

118. Blood supply of the heart
Arterial supply
Coronary aa Supply myocardium and epicardium of the
heart, The endocardium receives oxygen and nutrients
directly from the chambers of the heart.
 Arise from ascending aorta
Right coronary artery:-
branches
posterior IV branch
SA & AV nodal branch
right marginal branch
Left coronary artery:-
branches
anterior IV branch
SA nodal branch
circumflex branch
Left marginal branch
5/7/2024

119. Right coronary artery supplies
 The whole of right atrium
 Most of the right ventricle
 Part of left ventricle (diaphragmatic surface)
 Part of interventricular septum (posterior third)
 SA node (in 60% of people)
 AV node (in 80% of people)
5/7/2024

120. 5/7/2024

121. Left coronary artery supplies
 The left atrium
 Most of the left ventricle
 Part of right ventricle
 Most of interventricular septum (anterior two
third)
 SA node (in 40% of people)
5/7/2024

122. Veins of the heart
 the heart is drained mainly by veins that drain into
coronary sinus which empties into the right atrium
Coronary sinus
 It receives
• Great cardiac vein
• Middle cardiac vein
• Small cardiac vein
• Oblique vein
• Left posterior ventricular vein
• Left marginal vein
Anterior cardiac vein
• from the anterior aspect of right atrium
• empty directly to right atrium
Smallest cardiac veins (venae cordis minimae)
• begin in myocardium and open directly into all chambers
5/7/2024

123. Coronary veins
5/7/2024

124. 5/7/2024

125. Innervation of the heart
 Although the heart’s inherent rate of contraction is set by the SA
node, this rate can be altered by extrinsic neural controls
Parasympathetic nerve supply
 From Vagus nerve
 Parasympathetic stimulation slows the heart rate, reduces force
of contraction and constricts coronary arteries
Sympathetic nerves
 from the cervical and upper thoracic sympathetic trunks
 Sympathetic stimulation increases the rate and force of heart
contractions and produce dilation of coronary arteries
5/7/2024

126. 5/7/2024

127. Posterior mediastinum
 A space behind the
pericardium and diaphragm
 Boundaries
 Posteriorly – thoracic
vertebrae
( T5- T12)
 Anteriorly
o pericardium and
diaphragm
5/7/2024

128. Contents
• Esophagus
• Descending thoracic aorta and its branches
• Thoracic duct
• Azygos system of veins
• Thoracic sympathetic trunk and splanchnic
nerves
• Vagus nerve
5/7/2024

129. Contents
5/7/2024

130. The azygos & Hemiazygos venous systems
Azygos vein
 Drain the posterior thoracic wall and upper lumbar region
 Connects superior and inferior venae cavae
Formation
• Originate in the abdomen by union of lumbar azygos, right
ascending lumbar and right subcostal veins
Course
 Enter thoracic cavity through aortic opening or pierce right
crus of diaphragm
 Ascends on the right side of the vertebral column and
arches over the right bronchus to enter the posterior
aspect of the SVC at the level of T4
5/7/2024

131. 5/7/2024

132. Tributaries
1. Right superior
intercostal vein
2. Right 4 – 11
intercostal veins
3. Right subcostal
vein and right
ascending lumbar
4. Right bronchial
vein
5. Esophageal,
Mediastinal &
pericardial veins
6. Hemiazygos vein
7. Accessory 5/7/2024

133. Hemiazygos vein
 Origin
 In the abdomen by union of left ascending
lumbar and left subcostal or from left renal vein
 Course
 Enter thoracic cavity piercing the left crus of
diaphragm  at T9 crosses to the right behind
thoracic aorta, esophagus & thoracic duct 
end in azygos vein
 Tributaries
1. 9th – 11th left intercostal
2. Left subcostal
3. Left ascending lumbar 5/7/2024

134. The azygos and hemiazygos venous
systems
5/7/2024

135. Accessory Hemiazygos vein
 Originate at medial end of 4th and 5th
intercostal space on the left of the vertebral
column
 Crosses to the right at T8 behind aorta,
esophagus and join azygos vein
Tributaries
 Left 5th - 8th intercostal veins
 Left bronchial vein
5/7/2024

136. The azygos and hemiazygos venous
systems
5/7/2024

137. Esophagus
 Muscular tube, food
passage between
pharynx and
stomach
 extends from the
level of C6 to the
stomach (T11),
below the left dome
of the diaphragm
(25cm)
 Three parts –
cervical, thoracic &
abdominal
 Pierces the 5/7/2024

138. Esophagus
 Constrictions - in 4
regions
 C6 (at beginning)
 T2/3 (crossing of
aortic arch)
 T4/5 (crossing of left
primary bronchus)
 T10 (diaphragm)
 Obstructions may
occur at these
levels. These levels
are respectively 15,
22, 27 and 40 cm
from the incisor
5/7/2024

139. Sphincters
• superior esophageal sphincter - at junction with
pharynx ;voluntary
• inferior esophageal sphincter – at junction with
stomach; under the control of vagal (opener) and
sympathetic fibers (closer)
5/7/2024

140. Blood supply of Esophagus
Arterial supply
1. Cervical part up to arch of aorta – inferior thyroid
arteries
2. Thoracic part – esophageal branches of thoracic
aorta
3. Abdominal part – esophageal branches of left gastric
artery
Venous drainage
1. Upper part – brachiocephalic veins
2. Middle part – azygos veins( systemic vein)
3. Lower end – left gastric vein (portal drainage)
 Lower end of esophagus is one of the sites of
anastomosis between systemic and portal veins 
porto-systemic anastomosis 5/7/2024

141. Nerve supply -autonomic
Parasympathetic
Upper ½ - recurrent laryngeal nerve
Lower ½- esophageal plexus (formed by the two vagi)
Function – sensory, motor to muscles and mucus
secreting glands
Sympathetic
upper ½ - middle cervical ganglion
Lower ½- upper 4 thoracic ganglia (esophageal plexus)
Function – vasomotor
Lymphatic drainage
• Cervical – deep cervical lymph nodes
• Thoracic- posterior mediastinal lymph nodes
• Abdominal – left gastric lymph nodes 5/7/2024

142. The thoracic duct
 Largest lymphatic
vessel
 Begins at the
cisterna chyli (L1),
posterior to the
abdominal aorta,
inferior to the
diaphragm
 Enters the thorax
through aortic
opening posterior to
the aorta
 Ascends on the right 5/7/2024

143. The thoracic duct
 In the root of the
neck it arches
laterally (C7)
 terminate at the
junction between
the left subclavian
and left internal
jugular veins
5/7/2024

144. Tributaries of thoracic duct
 Posterior mediastinal nodes
 Intercostal nodes
 Left jugular trunk
 Left subclavian trunk
 Left mediastinal trunk
 It drains all the lymph of the body except for the right
thorax, right upper limb and right side of the head and
neck
 These remaining areas drain into the right lymphatic
duct which joins the junction of the right internal jugular
and right subclavian veins
5/7/2024

145. Thoracic
duct draining
into
brachioceph
alic V
Thoracic
duct
Cistrena
chyli
Accessory
Azygos
Hemiazygos
Azygos
Intercostal lymph
nodes
Right lymphatic duct
5/7/2024

146. The thoracic duct
5/7/2024

147. Sympathetic trunk
Is gaglionated chain on each side of the thoracic
vertebral column
Continues
superiorly with cervical sympathetic chain
inferiorly with lumbar chain
Contain 12 ganglia, but often 10 or 11 due to fusion
of adjacent ganglia
 The ganglia are connected to adjacent thoracic spinal
nerves by white and gray rami communicantes and are
numbered according to the thoracic spinal nerve with which
they are associated.
 The first is commonly fused with inferior cervical ganglion to
form cervicothoracic or stellate ganglion
 Lie at levels of corresponding intervertebral discs
5/7/2024

148. 5/7/2024

149. 5/7/2024

150. Branches - two groups
1. Lateral branches – for limbs & body wall
• Communicate with spinal nerve by two
rami
 White ramus – from spinal nerve to the
ganglia (preganglionic fiber)
 Grey ramus - from ganglia to spinal
nerves (postganglionic
fibers)
• Function
 Piloerection – arrector pili muscle of
skin
5/7/2024

151. 2. Medial branches – to thoracic and abdominal
viscera
A. Upper five ganglia – supply
A. Heart – cardiac plexus
B. Great vessels – aortic plexus
C. Lung – pulmonary plexus
D. Esophagus – esophageal plexus
B. Lower seven ganglia – from three splachnic
nerves which supply abdominal viscera
A. Greater splanchnic – 5th – 9th; ends in
coeliac, aorticorenal or suprarenal
B. Lesser splanchnic – 10th & 11th; ends in
coeliac ganglion
C. Lowest (least ) splanchnic – 12th; ends in
5/7/2024

152. Diaphragm
• Dome-shaped musculotendinous partition between
thoracic and abdominal cavities
• Principal muscle of respiration
• Composed of two portions: muscular (peripheral part)
and aponeurotic (central part)
Muscular part
• Fibers converge radially to central tendon
3 parts based on origin
• Sternal – back of xiphoid process
• Costal – inner surface of lower six costal cartilage
• Vertebral –lumbar vertebrae by two crura
• Right – superior 3
• Left – superior 2
• Crura are united superiorly at T12 by narrow arch called median
arcuate ligament
5/7/2024

153. 5/7/2024

154. Diaphragm
Central tendon
• Aponeurotic tendon formed by fibers of different
direction
• Has three lobes (right, left & median)
5/7/2024

155. Major openings
 Aortic – T12 median
plane, transmits
descending aorta,
thoracic duct, azygos
vein
 Esophageal – T10 left
of the median plane,
transmits esophagus,
vagi (anterior &
posterior), esophageal
branch of left gastric
artery
 Vena caval -– T8 right
of the median plane
with in the central
tendon, transmits IVC,
branch of right
phrenic, lymph vessels
5/7/2024

156. Other structures passing through diaphragm
1. Superior epigastric vessels – b/n sternal & costal
origins
2. Musculophrenic nerve– pierce at 7 or 8 costal
cartilage
3. Lower five intercostal nerves - b/n two slips of
costal origin
4. Subcostal nerves and vessels - behind lateral
arcuate ligament
5. Quadratus lumborum - behind lateral arcuate
ligament
6. Sympathetic trunk - behind medial arcuate
ligament
7. Psoas major – behind medial arcuate ligament
5/7/2024

157. Nerve supply:
Phrenic (motor and sensory)
lower six intercostal and sub costal for peripheral part
(sensory)
Blood supply:
Arteries
•Superior surface
Superior phrenic (thoracic aorta)
Musculophrenic and pericardiophrenic (internal
thoracic artery)
•Inferior surface: inferior phrenic(abd aorta)
Veins: same
Lymphatic drainage
•Thoracic surface to phrenic nodes
•Abdominal surface to lateral aortic nodes
•The two surfaces communicate freely 5/7/2024

158. 5/7/2024