anatomy of thorax.ppt

2
Contents
 Introduction
 Thoracic wall
– Skeleton of thorax
– Joints of thoracic wall
– Movements of thoracic wall
– breasts
– Muscles of the thoracic wall
– Nerves of the thoracic wall
– Vasculature of the thoracic wall
– Surface anatomy of the thoracic wall
 Thoracic cavity
– Pleurae
– Lungs
– Mediastinum
– pericardium
– Heart
– Great vessels

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Introduction
 Thorax is the superior part of trunk between
neck and abdomen
 Contains heart and great vessels, lungs,
thymus, trachea and esophagus
 Organs are constantly moving; dynamic region
 Clinical examination of chest requires a good
knowledge of its structure and vital organs it
contains

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Functions
 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

6
Skeleton of thorax
 Forms:
osteocartilaginous
thoracic cage
 Includes:
12 pairs of ribs
and costal
cartilages
12 thoracic
vertebrae and
intervertebral
discs
Sternum

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Skeleton of thorax: Ribs and costal cartilages
 Twelve pairs
 Ribs 1-7 attach directly to sternum by separate
costal cartilages - true ribs (vertebrosternal)
 Ribs 8-10 attach indirectly to sternum by
attaching to costal cartilages immediately above
(vertebrochondral)
 Ribs 11-12 have no anterior attachments -
floating ribs

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Skeleton of thorax: typical ribs (3rd-9th)
 Ribs are bowed flat bones
with long shaft
 Head: has 2 facets to
articulate with its vertebrae
and the one above
 Tubercle: articulates with
transverse process of
corresponding vertebra
 Neck: between head and
tubercle
 Shaft (body): flat, curved
 Angle of rib: point of greatest
change in curvature
 Costal groove: on inferior
border, protect intercostal
nerve and vessels
 Costal cartilages attach rib to
sternum

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Skeleton of thorax: Atypical ribs (1st, 2nd, 10th, 11th & 12th)
 First rib
• broadest and most curved
• flat, has scalene tubercle
• many structures cross it: clinically important
• subclavian vein and artery
• inferior trunk of brachial plexus
• difficult to palpate because of clavicle
 Second rib
• thinner and less curved
• has tuberosity for serratus anterior

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Skeleton of thorax: Atypical ribs (1st, 2nd, 10th, 11th & 12th)
 10th rib
• articulates with T10 vertebra only
 11th and 12th ribs
• short
• have single facet on their head
• have no neck or tubercle

12
Applied anatomy
 Variation of ribs
• Number: increased by development of cervical
or lumbar ribs or decreased by failure of the
12th rib to develop
• Shape: bifid ribs
 Angle of ribs are their weakest point

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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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 Manubrium
• Located at level of T3-T4
• Wide superiorly and narrow inferiorly
• Superior surface is indented by jugular notch
• Clavicular notch articulate with clavicle
• First rib articulate with lateral margin
• Inferior border articulate with body; forms
projection – sternal angle
Lies opposite 2nd costal cartilage: guide to
numbering of ribs

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 Body
• Located at level of T5-T9
• Lateral wall has costal notches
• Marked by 3 transverse ridges – line of fusion
 Xiphoid process
• Sword-shaped
• Cartilaginous at birth
• Landmark: inferior limit of thoracic cavity,
inferior border of heart

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Skeleton of thorax: Thoracic Vertebrae
 Typical: T4-T8
 Body is larger than
cervical; heart
shaped
 Spinous process is
long and sharp,
projects inferiorly
 Vertebral foramen is
circular
 T1: has long,
horizontal spinous
process

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Skeleton of thorax: Thoracic Vertebrae
 Transverse processes
project posteriorly and
bear costal facets for
ribs (T1-T10)
 Body bears two costal
demifacets (T2-T9)
• superior – articulate
with head of its own rib
• inferior- articulate with
head of the rib inferior
to it
 T1: has complete facet
superiorly
 T10-T12: one facet

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Joints of thoracic wall
 Intervertebral joint
Joints of vertebral bodies
Joints of vertebral arches
 Costovertebral joint
Joints of head of the ribs
Costotransverse joints
 Sternocostal joint
 Sternoclavicular joint
 Costochondral joint
 Interchondral joint
 Manubrosternal joint
 Xiphisternal joint

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Intervertebral joint: Joints of vertebral bodies
 Symphysis: articulating surfaces are
covered by cartilage and connected by
fibrocartilagenous intervertebral discs and
ligaments

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Intervertebral joint: Intervertebral discs
 Intervertebral discs are cushion like
pads interposed between vertebrae
 The discs play a leading role in weight
bearing
 Discs vary in size and thickness in
different regions
 Thinnest in thoracic region and thickest
in lumbar

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Intervertebral joint: Intervertebral discs
 Composed of
 Annulus fibrosus
surrounds the outer
margin
composed of
concentric lamellae
of fibrocartilage
 Nucleus pulposus
central core
semi fluid substance
shock absorber Herniation
of disk

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Intervertebral joint: Ligaments
 Ligaments hold the
vertebral column in
an upright position
the broad Anterior
longitudinal
ligament
the cord like
Posterior
longitudinal
ligament

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Intervertebral joint: Ligaments
 Ligaments
connect
specific
vertebra and
support disc
position
Supraspinous
ligament
Ligamentum
flavum
Interspinous
ligament

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Costovertebral joint
 Joints of head of the ribs
head of the rib articulates
with the sides of bodies of
2 vertebrae (at the same
and superior levels;
except for rib 1,10, 11,
and 12)
 Costotransverse joints
tubercle of rib articulates
with transverse process of
vertebra at the same level

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 Sternocostal joint
 1st – 7th ribs articulate with lateral border of sternum
 1st – synchondrosis
 2nd – 7th – synovial
 Strengthened by radiate sternocostal ligaments
 Costochondral joint
 Rib with costal cartilage
 Each rib has a cup-shaped depression in its anterior end into which
its costal cartilage fits
 Interchondral joint
 Plane synovial joints exist between the costal cartilages of ribs 7,
8, and 9
 Manubrosternal joint
 Manubrium with body
 symphysis
 Xiphisternal joint
 Xiphoid process with body
 synchondrosis

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Skeleton of thorax: thoracic apertures
 thoracic inlet
superiorly, the site of
entrance of the viscera &
vessels from the head,
neck and upper limbs into
the thorax
kidney shaped
 thoracic outlet
closed by the diaphragm,
pierced by the inferior
vena cava (T8), aorta
(T12) and esophagus
(T10)

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Breasts
 Present in both sexes, but they function in
females
 Anterior to the pectoral muscles of the thorax
 Contains mammary glands; modified sweat
glands that produce milk to nourish a newborn
baby

28
Breasts: external anatomy
 Base: 2nd to 6th ribs
and sternum to
midaxillary line
 Slightly below the
center of each breast
is a ring of pigmented
skin, the areola,
which surrounds the
central conical
protruding nipple
 Nipple is located at
4th intercostal space
in nulliparous

29
Breasts: internal anatomy
 Lies in superficial fascia
 Between breast and deep
fascia on pectoral muscle
is retromammary space;
allows breast to move
freely
 each mammary gland
consists of 15 to 25 lobes
that radiate around and
open at the nipple
 The lobes are separated
by fat and fibrous
connective tissue

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The Mammary Glands
 The interlobar
connective tissue
forms suspensory
ligaments that attach
the breast to the
underlying muscle
fascia and to the
overlying skin
 The suspensory
ligaments provide
natural support for
the breasts

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The Mammary Glands
 Within the lobes are smaller units
called lobules which contain
glandular alveoli that produce
milk when lactating
 These compound alveolar glands
pass milk into the lactiferous
ducts, which open to the outside
at the nipple
 Just deep to the areola,
each lactiferous duct has a
dilated region called a
lactiferous sinus
 Milk accumulates in these
sinuses during nursing

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 Arterial supply: internal thoracic artery, axillary
artery and intercostal arteries
 Venous drainage: axillary, internal thoracic,
lateral thoracic and intercostal veins
 Lymphatic drainage: from subareolar lymphatic
plexus most lymph drains to axillary lymph
nodes and some lymph from medial and inferior
part drains to parasternal and abdominal lymph
nodes
 Innervation: lateral and anterior cutaneous
branches of 4th to 6th intercostal nerves

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Clinical correlates
 Breast cancer
Interference of lymphatic drainage by cancer may
cause lymphedema, which results in deviation of
nipple and thickening of skin
Prominent skin between dimpled pores may develop
due to involvement of suspensory ligaments
 Congenital anomalies
Polymastia and polythelia – breasts and nipples
exceeding two
 Usually rudimentary
 Appear along the line from axilla to groin
(embryonic mammary ridge)

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Muscles of the thoracic wall
 Muscles related to thoracic wall
 Pectoral muscles
 Muscles of abdomen
 Muscles of the back
 Muscles of thorax proper
 Serratus posterior
 Levator costarum
 Intercostals
 Subcostals
 Transversus thoracic

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Muscles of the Anterior Thorax

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Muscles of the Posterior Thorax

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Muscles of thorax proper: Serratus posterior
 Serratus posterior superior
Origin - ligamentum nuchae and spines of C7-T3
Insertion - superior border of 2-4 ribs
Action - elevates superior ribs
 Serratus posterior inferior
Origin - spines of T11-L2
Insertion - inferior border of inferior 3 or 4 ribs
Action - depress inferior ribs

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Muscles of thorax proper: levator costarum
 12 fan-shaped muscles
 Origin – transverse processes of C7 –T11
 Insertion - ribs
 Action - elevates ribs

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Muscles of thorax proper: Intercostal muscles
 Intercostal spaces contain 3 layers of
muscles:
External intercostal muscles
Internal intercostal muscles
Innermost intercostal muscles

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External
Intercostals
 Origin - inferior border of rib
above
 Insertion - superior border of
rib below
 Occupy intercostal spaces from
tubercles of ribs to
costochondral junction
 Anteriorly replaced by external
intercostal membranes
 Action - pulls ribs upward to
aid in respiration
 Muscle fibers project inferiorly in
a posterior to anterior direction

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Internal
intercostals
 Origin - superior border of
rib below
 Insertion - inferior border of
rib above
 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)

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Innermost intercostal
 Similar to
internal
intercostal;
deep portions
of them
 Separated
from internal
intercostals by
intercostal
nerves and
vessels

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Muscles of thorax proper: 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

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Muscles of thorax proper: Transversus thoracis
 Origin - from the back
of the sternum and the
xiphoid process
 Insertion - onto
costochondral junctions
of ribs 3-6
 Can bridge more than
one intercostal space

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Respiratory movements
 Breathing or pulmonary ventilation consists of
two phases
Inspiration: the period when air flows into the lungs
Expiration: the period when gases exit the lungs
 Lungs expand during inspiration and retract
during expiration.
 These movements are governed by:
movements of thoracic wall to increase the volume of
thoracic cavity
Elastic recoil of lungs and thoracic wall

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Principles of movement
 Each rib is considered as a lever, with the
fulcrum lies lateral to tubercle
 Anterior end of the rib is lower than posterior
end. Thus, when elevated anterior end also
moves forwards (pump handle movement)
 The middle of the body of the rib lies at lower
level than the two ends. Thus, when elevated it
also moves outwards (bucket handle movement)

48
Inspiration
 During inspiration the lungs increase in volume
by enlarging in all dimensions
 Inspiration lowers the air pressure within the
lungs
 Air flows from areas of high pressure to areas of
low pressure to equalize the pressure within the
lung to that outside the lung
 During normal quiet inspiration, the diaphragm
and external intercostal muscles produce the
muscle movement

49
Inspiration: action of diaphragm
 When the dome
shaped
diaphragm
contracts, it
moves inferiorly
and flattens
 As a result the
vertical dimension
of the thoracic
cavity increases

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Inspiration: action of intercostals
 The external
intercostal muscles
contract to raise the
ribs
 Because the ribs
normally extend
anterioinferiorly
from the vertebral
column, lifting them
enlarges both the
lateral and anterior
dimensions

52
Deep inspiration
 During deep or forced inspiration, additional
muscles contract and further increase thoracic
volume
 The rib cage is elevated by the scaleni and sterno-
cleidomastoid
 Scapulae are elevated and fixed by trapezius,
levator scapulae, rhomboids so that serratus
anterior and pectoralis minor act on ribs

53
Expiration
 As the respiratory muscles
relax, the rib cage drops
under the force of gravity
and the relaxing diaphragm
moves superiorly
 At the same time, the
many elastic fibers within
the lungs recoil
 The result is the volume of
the thorax and lungs
decrease simultaneously,
which pushes air from the
lungs

54
Forced expiration
 Quiet expiration in healthy people is a passive
process
 Forced expiration is an active process produced
by the contraction of muscles in the abdominal
wall, primarily the oblique and transverse
abdominis muscles
 These contractions
Increase the intrabdominal pressure which forces the
diaphragm superiorly
Sharply depresses the rib cage and thus decreases
thoracic volume
 The internal intercostal muscles, quadratus
lumborum and the latissimus dorsi also help to
depress the rib cage

55
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 (dermatome)
 Ventral rami of T1-T11=intercostal nerves
 Ventral ramus of T12 = subcostal nerve

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Intercostal Nerves
 Enters intercostal space between pleura and internal intercostal membrane
 run in middle of intercostal space between internal intercostal membrane
and muscle
 near the angle of the rib enter intercostal groove between internal
intercostal and innermost intercostal muscles
 Give branches to the muscles and lateral cutaneous branch
 Near sternum turns anteriorly and ends as anterior cutaneous branch
 Supply successive segments of thoracoabdominal wall (dermatome and
myotome)
 T1–T2 : also supply upper limb
 T3 - T6: only intercostal region, typical
 T7-T11: intercostal region + abdominal wall

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Branches
• Muscular to
 Subcostal
 Transversus thoracis
 levator costarum
 Serratus posterior
• Collateral
 supply intercostal
muscles
• Cutaneous
 anterior + lateral
• Communicating
 connect each nerve
to sympathetic trunk

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Vasculature of thoracic wall
Intercostal arteries
 Intercostal vessels run in the costal groove
 Posterior intercostal arteries (1)
 1st & 2nd - arise from superior intercostal artery (a branch of
costocervical trunk of subclavian artery)
 3rd -11th - branches of the thoracic aorta
 Accompanies intercostal nerve
 Branches
 Posterior: accompany dorsal ramus to supply spinal cord, vertebrae,
muscles and skin
 collateral branches: run along superior border of subjacent rib
 Anterior intercostal arteries (2)
 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

62
Intercostal veins
 One posterior and two anterior
 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

65
The internal thoracic artery
 Origin – from the subclavian artery
 runs between the transverse thoracis and the
sternum
 Termination - dividing around the xiphisternal
joint into the superior epigastric artery (which
enters the rectus sheath inferiorly) and the
musculophrenic artery (which follows the
attachment of the diaphragm to the ribs)
 also sends branches to the thymus, bronchi and
pericardium

66
Internal
Intercostal m
Transversus
Thoracis
Internal thoracic A
Muscolophrenic

67
Branches
• Pericardiopherenic – accompany phrenic nerve
• Mediastinal – supply anterior pericardium, fat and
thymus
• Perforating
• Anterior intercostals
• Superior epigastric
• Musculophrenic

69
The internal thoracic veins
 Accompany the
arteries (venae
comitantes)
 Unite in upper
three intercostal
space and drain
into brachiocephalic
vein

70
V
A
N
 Intercostal vein,
artery & nerve form a
neurovascular bundle
lying between internal
intercostals and
innermost intercostals
in costal groove

71
Surface anatomy of thoracic wall

72
Surface anatomy of thoracic wall

74
Thoracic cavity
 Cone shaped
 Has narrow superior aperture (thoracic inlet) and wide
inferior aperture (thoracic outlet)
 Boundary of inlet
 Anterior- superior border of manubrium of sternum
 Posterior – upper part of T1 vertebra
 Sides – internal upper border of 1st rib and cartilage
 Inferiorly - diaphragm in the form of two halves with a cleft
called sibsons fascia (suprapleural membrane)
 Boundary of outlet
 Anterior – infrasternal angle between the costal margins
 Posterior – inferior part of T12 vertebra
 Lateral- costal margin of 7th - 10th ribs
 Inferiorly- completely closed with thoracoabdominal diaphragm

76
Parts of the thoracic cavity
 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

79
The Pleurae
 Double layered serous
membrane lined with
mesothelium (simple
squamous epithelium)
1. parietal pleura (outer) –
adherent to body wall
2. visceral pleura (inner) -
attached with lung and
its fissures
 The two layers are
continuous around hilum
 A potential space
between the two layers
is called pleural cavity

80
The parietal pleura
 Attached to the costal, diaphragmatic, cervical
and mediastinal surfaces of thoracic wall by the
endothoracic fascia
 Parts of the parietal pleura
Diaphragmatic
Mediastinal
Costal
Cervical (copula)
 It also encloses the great vessels running to the
lung root
 projects into the root of the neck as the copula

81
The visceral pleura
 Covers surfaces and fissures of lungs
 Firmly adherent to lung
 Insensitive to pain
 Provides a moistened and lubricated surface for
lung movement
 Adhesions with the parietal pleura may result
from infections, inflammatory reactions and lung
immobility

82
 Visceral and parietal pleurae are
continuous at the root of the lungs,
where pulmonary artery and vein, and
bronchus penetrate the lung
 The continuity between parietal and
visceral pleurae surrounding the root of
the lung extends downwards as a fold
called pulmonary ligament
– It provides a space into which pulmonary
veins can expand

84
The Pleural cavity
 A slit like potential space between the parietal
and visceral pleurae
 Filled with a thin layer of pleural fluid secreted
by the pleurae
– lubricating fluid allows the lungs to glide without
friction over the thoracic wall during breathing
movements
– holds the parietal and visceral pleurae together

85
Pleural recesses
 Cavity not occupied by the
lung
 Reserve spaces for lung to
expand
Costodiaphragmatic recesses
 inferiorly between costal and
diaphragmatic pleura
 5cm vertically, extends from 6-10
ribs
 first part of pleural cavity to be
filled with effusion
Costomediastinal recesses
 anteriorly between costal and
mediastinal pleura

86
Surface marking of the pleura
 Cervical pleura
 curved line from sternoclavicular joint to the
junction of medial and middle third of clavicle
 2.5 cm above clavicle
 Anterior margin
 sternoclavicular joint to midpoint of sternal angle
 Right – descends to 6th rib in the mid sternal line
 Left – descend to the 4th rib on the mid sternal line
then deviates to the sternal margin to make cardiac
notch

87
 Inferior margin
Passes laterally from anterior margin
Crosses 8th rib in the midclavicular line; 10th rib in
the midaxillary line and rib 12 dorsally
 Posterior margin
Passes from a point 2 cm lateral to 12th thoracic
spine to 7th cervical spine

89
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

90
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
 Regions of the pleura not protected by ribs –
cupula, right infrasternal, right and left
costovertebral angles

91
Pleuricentesis (pleural tab)
• 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

93
The Lungs
 The lungs occupy all of the thoracic cavity
except the mediastinum
 Each cone shaped lung is suspended in its own
pleural cavity and connected to the mediastinum
External anatomy
 Spongy in texture and pink in colour in young
but mottled black by carbon particles in adults
 Has
 An apex
 A base
 Three borders: anterior, posterior and inferior
 Two surfaces: costal and medial

96
Apex
 Blunt, lie above anterior end of first rib
 Projects into the root of neck through the
thoracic inlet extending 1 inch above the
medial 1/3 of clavicle
 Anteriorly grooved with subclavian artery
 Covered by cervical pleura and suprapleural
membrane

97
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

98
Borders
Inferior
Separates the base from costal and medial surfaces
Anterior
Thin and short
Right vertical
Left shows wide cardiac notch
Posterior
Thick and ill defined
Correspond to medial margins of head of ribs
Extends from 7 cervical spine to 10 thoracic spine

99
Surfaces
Medial surface
• has vertebral and mediastinal parts
 The vertebral part: posterior; round
occupying the thoracic gutters
 The mediastinal part: lies anterior to the
vertebral column. It contains the hilum of
the lung
Costal surface
• Adjacent to sternum, costal cartilages and
ribs

100
Impressions on mediastinal surface
 Anterior to the hilum – cardiac on both
lungs but more pronounced on the left
 Posterior to the hilum – esophagus and
thoracic aorta on the right and left
respectively
 Superior to the hilum – azygos and arch
of aorta for right and left lungs
respectively

101
The root of the lung
• Short broad pedicle which connects medial surface of lung
with mediastinum
• Formed by structures which leave or enter the lung at hilum
• Lie at level of T5-T7
Contents
A. Bronchus – posterior
 Left – divide after entering, only one
 Right - divide before entering: epiarterial & hyparterial
B. Pulmonary artery
 On the left – more anterior and higher
 On the right – between eparterial and hyparterial

102
C. Pulmonary veins – two in each, superior and inferior
A. Superior – anterior and inferior to pulmonary artery and
bronchus
B. Inferior – the most inferior
D. Bronchopulmonary lymph nodes
E. Bronchial vessels
A. Bronchial artery - left two (braches of descending aorta) &
right one (upper left bronchial artery/3rd posterior
intercostal)
B. Bronchial veins - right to azygos and left to accessory
azygos and hemiazygos
F. Pulmonary plexus – parasympathetic + sympathetic
G. Lymphatics of lung
H. Areolar tissue

103
The right lung
 The right lung has 3 lobes and 2 fissures
Horizontal fissure
From anterior border of right lung at 4th costal
cartilage to meet the oblique fissure at mid axillary
line
divide the superior from the middle lobe
Oblique fissure
between middle and inferior lobes
from posterior border 6 cm below the apex (at
third thoracic spine) to the inferior border 5cm from
median plane
Examination of the superior lobe is done on the
anterior chest wall, whereas examination of the
inferior lobe is done posteriorly below the scapula

105
Mediastinal relation of right lung
 Pericardial impression – anterior to the hilum by
right atrium
 IVC impression – posterior to pericardial mark
 SVC – anterior and superior to hilum
 Esophageal - large vertical groove behind the
hilum and impression of trachea
 Trachea – behind SVC
 Azygos groove – behind esophageal
 Ascending aorta and thymus – anterior to hilum

106
The left lung
 has a superior and inferior lobe divided by an
oblique fissure
 large cardiac notch found on the mediastinal
surface
 The lingula - an anterior projection of the
superior lobe below cardiac notch overlies the
anterior aspect of the heart

107
Mediastinal impression of left lung
A. Pericardial – left ventricle
B. Arch of aorta – above the root
C. Thymus – above the root anterior to the
groove for arch of aorta
D. Descending aorta – posterior to the hilum
E. Left subclavian artery - superior to the
groove for arch of aorta

108
Mediastinal relation of the lungs

111
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
Arrangement in
the hilum
PA; higher, 1
bronchus
PA; between bronchi, 2
bronchi
Differences between right and left lung

112
The Conducting Zone of the Bronchial tree
The primary bronchus
• The right and left primary
bronchi are formed by the
division of the trachea at
the level of T4 in the
mediastinum
• The right is shorter, wider
and more vertical than
left
 Inhaled particles tend to
pass more frequently to
the right lung (the
posterior basal segment
is most likely)

113
The lobar bronchi
• Each primary bronchus enters the hilus of the lung
and divides into secondary or lobar bronchi
– Right – 3; upper, middle & lower
– Left - 2; upper & lower
• divide into the tertiary or segmental bronchi which
supply bronchopulmonary segments of the lung
• The tertiary bronchus is joined by a tertiary division
of the pulmonary artery

114
Tertiary (segmental) bronchi
 Right (10) and Left (9)
 Right superior lobar bronchi - apical, posterior
and anterior tertiary bronchi
 Left superior lobar- apicoposterior, anterior,
superior lingular and inferior lingular
segmental bronchi
 Right middle lobar - medial and lateral tertiary
bronchi
 Right and left inferior lobar- superior, medial
basal, lateral basal, anterior basal and
posterior basal segmental bronchi

117
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

118
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

120
Clinical significances of bronchopulmonary
segments
 Limit the spread of some diseases within the
lung, because infections do not easily cross the
connective tissue partitions between them
 Because only small veins span these partitions,
surgeons can neatly remove segments without
cutting any major blood vessel

121
Histology of the bronchi
 Layers - mucosa, lamina propria, submucosa,
adventitia
– Mucosa – pseudostratified ciliated columnar
epithelium with goblet cells
– Lamina propria – connective tissue and smooth
muscle layer
– Submucosa – contains mucus and mucoserous
glands
– Adventitia – contains hyaline cartilage

122
Bronchioles
• 5mm diameter or less
• terminal branches of tertiary bronchi
• have neither cartilage nor glands in their mucosa
• epithelium is a respiratory epithelium changing to
ciliated simple columnar or cuboidal
• increased smooth muscle
Terminal bronchioles
• the distal part of the conducting portion
• lined by simple cuboidal epithelium containing
clara cells, no goblet cells
• Clara cells - ciliated cells, secrete surfactant and
metabolize air bone toxins

123
The Respiratory Zone
 Consists of respiratory bronchioles, alveolar duct &
alveolar sacs
 Respiratory bronchioles
– Transitional zone between the conducting and
respiratory part
– Contain dispersed alveoli
– Lined by ciliated cuboidal epithelium that
becomes continuous with squamous alveolar
lining cells
– Each give 2-11 alveolar ducts

125
Alveolar ducts
 The ducts lead into
terminal clusters of
alveoli called alveolar
sacs
 Each alveolar duct gives
5-6 alveolar sacs which
give rise to alveoli
 Wall: smooth muscle cells +
collagen and elastic fibers
 Lined by squamous alveolar
cells

126
Alveolus
 Saclike evagination
 Lined by flattened epithelial cells
 Fibers around openings merge to form a supporting
framework for lung parenchyma
 Alveolar wall
– Consists of 3 components: epithelium, supporting tissue and
blood vessels
 Cells of the alveoli
– Pneumocyte type I cells - form the alveoli walls
– Pneumocyte type II cells - secrete a phospholipid called surfactant
that coats the alveolar surfaces which prevents collapse of alveoli
walls
– Alveolar macrophages – phagocytic cells, trap dust particles, carry
to bronchioles for ciliary action

127
 Lung alveoli have three other features
– Surrounded by fine elastic fibers
– pores connect adjacent alveoli
 Allow for pressure equalization
 Alternative air routes for blocked bronchi
– The external surfaces of the alveoli are densely covered
with a web of pulmonary capillaries

130
The Respiratory Membrane
 Gaseous diffusion barrier between
blood and alveolar air
 Capillaries form plexus around
alveoli
 Basement membrane of capillaries
fuses with that of epithelium
which provide interface of minimal
thickness
 Gas exchange occurs by simple
diffusion across the respiratory
membrane
 respiratory epithelium at thinnest
site consists of
– Cytoplasm of type I cells
– Common basement membrane
– Cytoplasm of capillary endothelial
cells

131
Blood supply of the Lungs
Pulmonary arteries
 Two in number; one for each lung
 derived from the bifurcated pulmonary trunk
 Carry poorly oxygenated blood to lungs for
oxygenation
 Give off branch to superior lobe before entering hilum
 The right pulmonary artery is crossed over by the
azygos vein whereas the left pulmonary artery is
crossed over by the arch of the aorta at T5
 Within the lung, divide into lobar branches and then
segmental branches which have a close relationship
with the tertiary bronchi in the bronchopulmonary
segments

133
Bronchial arteries
• Supply blood to root of lungs, supporting tissue
and visceral pleura
• Origin
Right – one; 3rd right posterior intercostal /
upper left bronchial / superior posterior
intercostal
Left – two; thoracic aorta
• Posterior to bronchi
• Give branch to esophagus
• Supply bronchial tree to respiratory bronchioles
• Distal branches anastomose with branches of
pulmonary arteries

134
Bronchial veins
• Drain only regions supplied by bronchial
arteries; the rest is drained by pulmonary
veins
• Termination
Right – azygos
Left – accessory hemiazygos/ left
superior intercostal vein

135
Pulmonary veins
 Four in number; two for each lung
 Carry well-oxygenated blood
 Begin from pulmonary capillaries as small veins;
join into larger veins and drain into
intersegmental veins in the septa which join to
form pulmonary veins
 2 lower veins - from the inferior lobe of each lung
 Upper right vein - from the superior and middle
lobe of the right lung
 Upper left vein - from the superior lobe of the left
lung
 The pulmonary veins also drain oxygenated blood
supplied to the lungs by the bronchial arteries

136
Lymphatic drainage of the Lungs
 Bronchopulmonary lymph nodes - two sets of lymphatics
drain into bronchopulmonary lymph nodes at the hilum
– Superficial: from the superficial part of the lung
– Deep: drain bronchial tree, vessels and lung tissue
 Tracheo-bronchial lymph nodes – two groups; superior and
inferior located at the bifurcation of trachea
 both nodes drains into broncho-mediastinal lymphatic duct
– Right – right lymphatic duct
– Left – thoracic duct

138
Nerves of the Lungs
• The bronchopulmonary plexus supplies both
parasympathetic & sympathetic nerves to the
bronchial and vascular trees
– Parasympathetic fibers are preganglionic vagal
 Secretomotor to glands in the bronchial mucosa
 Motor to bronchial smooth muscles – spasm
 Sensory
 Vasodilator to bronchial and pulmonary vessels
– Sympathetic fibers are postganglionic fibers from T2-T5
 vasomotor to arterial system (vasoconstriction)
 Bronchodilator
 Inhibitory to bronchial glands

139
The Mediastinum
 Median region between the two pleural sacs-
from superior thoracic aperture to
diaphragm and from sternum to thoracic
vertebral bodies
 Divided into superior and inferior by
imaginary plane passing through sternal
angle anteriorly to lower border of T4
posteriorly
Superior mediastinum
• Superior thoracic aperture to imaginary plane
b/n sternal angle and lower border of T4

141
Inferior mediastinum
• Imaginary plane to diaphragm
• Divided into anterior, middle and posterior
A. Anterior mediastinum – b/n pericardial sac and
sternum; contains thymus, sternopericardial
ligaments, parasternal lymph nodes and
transverse thoracis muscle
B. Middle mediastinum – occupied by pericardial sac,
heart and roots of great vessels (aorta, pulmonary
trunk , SVC, IVC and four pulmonary veins)
C. Posterior mediastinum –b/n lower eight thoracic
vertebral bodies and pericardial sac , posterior portion of
diaphragm inferiorly; contains esophagus, thoracic aorta &
thoracic duct

142
Superior
Inferior
Anterior
Posterior
Divisions of the Mediastinum
Middle

143
Superior mediastinum
 Boundary
– Anterior – manubrium of sternum
– Posterior – upper four thoracic vertebrae
– Superior – inlet of thoracic cavity
– Inferior – imaginary line passing from sternal angle to lower border
of T4
 Contents – from anterior to posterior
– Thymus
– Great vessels
 Arteries – arch of aorta, brachiocephalic trunk, left common carotid and
left subclavian
 Veins – left brachiocephalic, upper half of SVC & left superior intercostal
vein
 Nerves - phernic nerve, Vagus nerve, Cardiac plexus, Left recurrent
laryngeal nerve
 Trachea
 Esophagus (thoracic part)
 Thoracic duct
 Muscles

144
Contents of superior mediastinum

145
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
 Arterial supply – inferior thyroid, internal thoracic, anterior
intercostal
 Venous drainage – to left brachiocephalic, internal thoracic
& anterior intercostal
 Lymphatics – parasternal, brachiocephalic &
trachiobronchial
 Nerves – sympathetic – vasomotor

146
Histology of thymus
 Is lymphoepithelial organ
 Connective tissue capsule, penetrate the
parenchyma to divide into lobules
 Each lobule has
– Cortex- composed of T- lymphocytes, epithelial
reticular cells, few macrophages
 Site of proliferation of lymphocytes
– Medulla – contain Hassall’s corpuscle
(concentrically arranged, flattened epithelial
reticular cells & filled with keratin filament)

147
Blood thymus barrier
 sheath of epithelial reticular cells surrounding small
vessels of the cortical parenchyma; made up of
– Pericytes, capillary basal lamina, basal lamina of epithelial
reticular cells, cells of the capillary & epithelial reticular
cells
– Used to prevent T-lymphocytes from circulating antigens
Neonatal thymus stained with H&E

148
Great blood vessels
Brachiocephalic vein (innominate vein)
• Formed by union of internal jugular vein and subclavian vein behind
sternoclavicular joint
• Tributaries
 both right & left – internal thoracic vein, inferior thyroid vein
 Left only – left superior intercostal vein, thoracic duct
 Right only – right lymphatic duct
Right brachiocephalic vein
• Short & vertical
• Located lateral to brachiocephalic artery & right vagus lies between
them while right phrenic is on the posterolateral aspect of the vein
Left brachiocephalic vein
• Two times longer than the right
• Passes from left to right posterior to the upper part of the manubrium
of the sternum crossing left phernic, right common carotid and
brachiocephalic anteriorly

151
Superior vena cava (SVC)
• Formed by union of right and left brachiocephalic
veins behind the right first costal cartilage near to
the sternum
• Located in the right part of superior mediastinum
and middle mediastinum
 Lateral to the descending aorta
 Anterior to the root of the lung
 Anterolateral to trachea
– Pierce the pericardium – opposite to right 2nd
costal cartilage
– End into the upper aspect of the right atrium at
the left 3rd costal cartilage
– Average length – 7cm

152
Aorta
• Three parts – ascending aorta, arch of aorta &
descending aorta
Ascending aorta
• 5 cm long, covered in the pericardium
 Begin behind left half of sternum at the level of 3rd
costal cartilage
 Directs fore ward to the right to become continuous
with the arch of aorta
 Ends at the level of right 2nd costal cartilage
 Has three dilations – anterior, right posterior & left
posterior aortic sinuses
The right and left coronary arteries arise from
anterior & left posterior aortic sinuses respectively

153
Arch of aorta
• exclusively located in the superior mediastinum
• Begin in the right 2nd costal cartilage, directs upward, back
ward and to the left
• Ends at the lower border of the T4 to be continuous with
the descending aorta
• Curves above the root of lung behind left primary bronchus
Relations
Anterior to the left aspect
• nerves – left phrenic, upper & inferior cervical cardiac
branch of left vagus
• Left superior intercostal vein
• Left pleura
• Thymus

154
Posterior right aspect
• Trachea
• Esophagus
• Left recurrent laryngeal
• Thoracic duct
Superior aspect
• Brachiocephalic trunk
• Left common carotid
• Left subclavian
• Thyroid ima
Inferior aspect
• Bifurcation of pulmonary trunk into pulmonary arteries
• Ligamentum arteriosum, remnant of ductus arteriosis
• Left recurrent laryngeal nerve, posterior to the ligamentum arteriosum
• Left principal bronchus

156
 Branches
– brachiocephalic
trunk
– Left common
carotid
– left subclavian
– Thyroid ima
(variable)

157
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 arch

158
Relations
 Thoracic - in the superior
mediastinum, 5-6 cm
– Anteriorly -
brachiocephalic artery &
left common carotid artery
– Posteriorly – esophagus
and recurrent laryngeal
nerves
– Left – arch of aorta, left
common carotid and left
subclavian arteries, left
recurrent and pleura
– Right - vagus, azgos vein
and pleura

159
Tracheal Wall
 consists of mucosa,
submucosa, and
adventitia
1. The mucosa is
pseudostratified
columnar (respiratory
epithelium); contains
goblet cells
– Its cilia continually
propel mucus, loaded
with dust particles and
other debris, toward the
larynx
– Smoking destroys the
cilia

160
2. The submucosa - a connective tissue layer,
contains seromucous glands that help produce
the mucus “sheets” within the trachea
3. The adventitia - a connective tissue layer that is
reinforced by 16 to 20 C- shaped rings of hyaline
cartilage, prevents it from collapse
• Posterior part – incomplete lined by trachealis muscle,
for extending esophagus
• Last tracheal ring – forms carina, project posteriorly

161
 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
– Sympathetic (T1-T4) – smooth muscles (dilator)
and blood vessels (vasoconstrictors)
Neurovasculature

162
Phernic nerve
 Branches of 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)
 Right phernic
 enter the thoracic cavity behind right subclavian and descends close
to the right brachiocephalic vein and to the right of the SVC
 Leave the thoracic cavity through the caval opening on the
diaphragm with IVC
 Accompanied by right pericardiophernic vessels
 Left phernic
 Anterior to left subclavian and crosses the arch of aorta anteriorly

164
Vagus nerve
 The tenth cranial nerve originating from
medulla oblongata
 Each of them passes behind the root of the
lung giving large contribution to the
pulmonary plexuses
 Below the hilum of the lung join esophageal
plexus, become mixed, after leaving the
plexus, right & left vagal trunk contain fiber
from each vagus

165
 On the arch of aorta the left nerve gives off
left recurrent laryngeal nerve that hooks
around the ligamentum arteriosum, passing
upward on the right side of the arch of aorta,
ascending between esophagus and trachea
 The right recurrent laryngeal nerve is given
off in the root of the neck and hooks around
the right subclavian artery

166
Course of left vagus
 Enter thorax behind the left Brachiocephalic V
 between L common carotid A and L
subclavian A  anterior to the arch of aorta 
give left recurrent laryngeal nerve  posterior
to L primary bronchus  posterior to the root
of the L lung and give braches to pulmonary
plexus  form esophageal plexus with right
nerve  L vagal trunk  passes through the
esophageal hiatus

167
Course of right vagus
 Enter thorax crossing the first part of right
subclavian artery anteriorly and gives right
recurrent laryngeal nerve which hook the
artery and ascend between trachea &
esophagus  posterior to Right
Brachiocephalic V  right border of trachea
posterior to R principal bronchus 
behind the root of the R lung  branches
join esophageal plexus  R Vagal trunk
formed  esophageal opening of diaphragm

169
Branches of vagus in the thorax
1. Cardiac – to superficial and deep cardiac
plexuses
2. Left recurrent
3. Anterior pulmonary
4. Posterior pulmonary
5. Esophageal branch to esophageal plexus

171
Cardiac plexuses
 Two – superficial and deep
 Lie anterior to the bifurcation of trachea and
posterior to ascending aorta
 Branches - enter pericardium accompanying
coronary arteries (vasomotor) reach to SA, AV
nodes and bundles
 Parasympathetic are preganglionic that relay at
SA node; cardioinhibitory
 Sympathetic are postganglionic relayed in the
cervical and thoracic ganglia; cardioacceletory

172
Deep cardiac plexus
 Located in front of the bifurcation of trachea and
behind the arch of aorta
 Formed by
Cardiac branches of vagus and recurrent laryngeal nerves
All cardiac branches of cervical and upper thoracic ganglia of
sympathetic chain
Superficial cardiac plexus
 Located below arch of aorta in front of right
pulmonary artery
 Formed by
 inferior cervical cardiac branches of left vagus
 superior cervical cardiac branch of left sympathetic chain

175
Anterior mediastinum
 Lies between the pericardium and sternum
 Become continuous with the superior
mediastinum through the pretracheal space
 Contents
– Thymus
– sternopericardial ligaments
– parasternal lymph nodes
– transverse thoracis muscle

176
Middle mediastinum
Boundary
• superior - imaginary line
• Inferior- diaphragm ( where the pericardium rests)
• 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 phernic nerve

177
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

179
The fibrous pericardium
 Conical in shape having base and apex
 Fused with great vessels and attached to the central
tendon of the diaphragm
– Influenced by movements of heart and great vessels,
sternum, and diaphragm
A. Apex – directs upward, lies at the level of sternal
angle, fused with roots of great vessels and
pretracheal fascia
B. Base - attached to the central tendon of diaphragm
C. Anteriorly – attached to the upper and lower end of body of
sternum by sternopericardial ligaments

180
The Serous pericardium
 Double layered serous membrane
– Outer layer – parietal pericardium; fused with fibrous
– Inner layer –visceral pericardium (epicardium ); attached to
the heart
 At the superior reflection of the heart, the parietal
layer is continuous with the visceral layer of the
serous pericardium or epicardium
 Between the two layers of serous pericardium is the
slit like pericardial cavity
– The cavity contain thin films of seruos fluid
 The serous membranes, lubricated by fluid, glide
smoothly against one another during heart activity,
creating a relatively friction-free environment

181
Pericardial sinuses
 pericardial reflection from the parietal to
visceral forms sinuses on the posterior part of
the heart
– Oblique sinus – bounded by IVC and four
pulmonary veins , forms a resses between the left
atrium and the pericardium
– Transverse sinus – between the superior vena cava
and pulmonary trunk and aorta
 Used for legating large vessels during cardiac surgery

182
Blood supply and innervation
A. Fibrous and Parietal pericardium
A. Arteries – pericardiophrenic (main),
musculophrenic, branches of descending aorta
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

183
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

185
Introduction
 The heart is a muscular double pump with two
functions
– Its right side receives oxygen poor blood from the
body tissues and then pumps it to the lungs
– Its left side receives oxygenated blood from the
lungs and then pumps it to the body
 The cardiovascular system provides the
transport system of the body

186
Pathway of Blood
Pulmonary circulation
• The blood vessels that carry blood to and from the lungs
form the pulmonary circulation
• The right side of the heart is part of the pulmonary
circulation
• Blood returning from the body enters the right atrium
through superior and inferior venae canae and passes into
the right ventricle which pumps the blood to the lungs via
the pulmonary trunk
• oxygenated blood is carried to the heart by the pulmonary
veins
• The pulmonary circulation, served by the right ventricle, is a
low pressure circulation

187
Systemic circulation
• The vessels that carry blood to and from all the body tissues
form the systemic circulation
• The left side of the heart is the systemic pump
• Oxygenated blood enters the left atrium and passes
into the left ventricle
• The left ventricle pumps blood into the aorta and
from there into many distributing arteries and to
capillaries
• Blood then returns to the right atrium of the heart via
systemic veins and the cycle continues
• The systemic circulation, served by the left ventricle,
circulates through the entire body and encounters
about five times as much resistance to blood flow

189
Size, location and position of heart
 The heart is about the size of a fist
 It weighs between 250 - 350 grams
 Located in the medial cavity of the thorax, the
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

191
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 longitudinal wall
separating the chambers is
called septum
– Interatrial septum
 Between atria
– Interventricular septum
 Between ventricles
Atria
Septum
Ventricles

192
Grooves
– indicate the boundaries of its
four chambers and carry
coronary vessels
 Atrioventricular groove or
coronary sulcus
– encircles the junction of the
atria and ventricle
 Anterior and posterior inter-
ventricular sulcus
– separates the right and left
ventricles
Anterior
Interventricular
Sulcus
Coronary
Sulcus

193
Shape
• 3 sided pyramid with apex, base and 4 borders and 4
surfaces
 The apex
• points downwards, forwards and to the left
• lies in left 5th intercostal space just medial to
midclavicular line
• formed by left ventricle
 The base
• directs to right shoulder
• At vertebral levels of T6 –T9
• Between bifurcation of pulmonary trunk and coronary
groove
• Forms the posterior surface
• Formed mainly by left atrium and small part of right
atrium

194
Borders
• Right – vertical, formed by right atrium; in line
with SVC and IVC
• Left – oblique and curved; formed mainly by
left ventricle and partly by left auricle
• Inferior – horizontal, formed mainly by right
ventricle; left ventricle near the apex
• Superior – slightly oblique, formed by two
atria

195
Surfaces
 Diaphragmatic (inferior) surface
• Rests on central tendon of diaphragm
• Directed downwards and slightly backwards
• formed by left ventricle (left 2/3) and right ventricle
(right 1/3)
 Sternocostal (anterior) surface
• Faces anteriorly, superiorly and to the left
• Formed mainly by right atrium and right ventricle;
and partly by left ventricle and left auricle
 Left pulmonary surface
• Formed by left ventricle
 Right pulmonary surface
• Formed by right atrium

196
Surface marking of the heart
 Upper border – a line
joining a point at 2nd left
costal cartilage 1.2 cm
from sternal edge to a
point at 3rd right costal
cartilage 1.2 cm from
sternal edge
 Lower border – a line
joining a point at 6th rig
ht costal cartilage 1.2 cm
from the sternal edge to
a point at apex in 5th
intercostal space 9cm
from the midline
 Right and Left borders –
slightly convex lines
joining upper and lower
borders

197
Surface marking of the heart

198
Right atrium
 Receives venous blood from
the body through SVC, IVC
and coronary sinus and
pumps it to right ventricle
through right AV orifice
 Forms the right border, the
sternocostal surface and
base of heart
Auricles
Atria
SVC
IVC

199
Right atrium: external features
 Elongated vertically, receiving
SVC at upper end and IVC at
lower end
 Upper end is prolonged to left
to form right auricles
– ear like appendages, increase the
atrial capacity slightly
– represent primordial atrium
 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

200
The right
atrioventricular groove
separate it from right
ventricle
– Vertical
– Lodges right coronary
artery and small cardiac
vein

202
Right atrium: internal features
 The interior has 3 parts
 The smooth posterior part (sinus
venarum)
– Derived from embryonic sinus
venosus
– SVC (upper end) & IVC (lower end)
opens into it
– Coronary sinus opens between IVC
orifice and right AV orifice
 The rough anterior part
(pectinate part)
– Present a series of transverse
muscular ridges, pectinate muscles
 Arise from crista terminalis and
run towards AV orifice
Coronary
sinus
Pectinate
Muscle

203
Right atrium: internal features
 Inlets of the right atrium
 Major
– SVC
– IVC
– Coronary sinus
 Smaller
– Anterior cardiac veins
– Venae cordis minimi
– sometimes right marginal
vein

204
 The Interatrial septum
– Separate the atria
– Presents a shallow
depression, fossa ovalis
 Remnant of the opening,
foramen ovale, existed in
the fetal heart
– limbus fossa ovalis: a
prominent margin of fossa
ovalis; valve of foramen
ovale
Fovea
Ovalis

205
Trabeculae
carneae
Papillary
muscles
Right ventricle
 The right ventricle forms most of
the anterior surface of the heart, a
small part of diaphragmatic
surface and entire inferior border
 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

206
 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

207
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
Septomarginal trabecula (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

208
Right ventricle: internal structures

209
 Forms most of the base
 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
Right
Pulmonary
veins
Left atrium

211
Left Ventricle
 forms the apex of the
heart, most of
diaphragmatic surface
and left border
 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

212
 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

213
Left Ventricle: Internal structure

214
Contraction and relaxation of the heart
 The two atria contract together, followed by the
simultaneous contraction of the two ventricles
 The synchronous pumping action of the heart two
pumps constitute cardiac cycle
 The cycle begins with ventricular elongation
(relaxing) and filling with blood termed as diastole
and ends with a period of ventricular shortening
(contraction) and emptying called a systole
 Systole and diastole refers to the ventricles which
are the dominant heart chambers

215
Heart Valves
 Blood flows through the heart and other parts
of the circulatory system in one direction
– Right atrium  right ventricle  pulmonary
arteries  lungs
– Lungs  pulmonary veins  left atrium 
left ventricle  body
 This one way flow of blood is controlled by four
heart valves

216
Heart Valves
 Heart valves are
positioned between
the atria and the
ventricles and
between the
ventricles and the
large arteries that
leave the heart
 Valves open and
close in response to
differences in blood
pressure
Bicuspid
(mitral)
valve
Aortic
valve
Pulmonary
valve
Tricuspid
valve

218
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 called chordae tendinae
– The cords anchor the cusps to the
papillary muscles

219
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

220
 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 flaps in their
closed position

221
Semilunar (SL) Valves
 Found at the bases of the large arteries exiting the
ventricles
– The aortic and pulmonary semilunar valves
 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

223
Heart Sounds
 The closing of the heart valves causes
vibrations in the adjacent blood and heart walls
that account for the familiar “lub-dup” sounds
of the heartbeat
 The “lub” is produced by the closing of the AV
valves at the start of ventricular systole
 The “dup” is produced by the closing of the
semilunar valves at the end of ventricular
systole
 Sounds are heard away from the valves in the
direction of the blood flow

224
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
left 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

226
Fibrous Skeleton of the heart
 The fibrous skeleton of the heart lies in the plane
between the atria and the ventricles surrounding the
four valves
 Four fibrous rings of collagen
 Composed of dense connective tissue
 Function
– anchors the valve cusps
– prevents overdilation 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 atria
to the ventricles

227
Layers of the Heart Wall
 The heart wall is composed of three layers (superficial to
deep)
– epicardium
– myocardium
– 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

228
 Within the myocardium, the branching cardiac muscle cells
are tethered to each other by crisscrossing connective tissue
fibers also arranged in spiral or circular bundles
– These interlacing bundles effectively link all parts of the heart
together
 The connective tissue forms a dense network called the
internal skeleton of the heart
– It reinforces the myocardium internally and anchors the cardiac
muscle
– This network of fibers is thicker in some areas than in others to
reinforce valves and where the major vessels exit
– The internal skeleton prevents over dilation of vessels due to the
continual stress of blood pressure
– Additionally, since connective tissue is not electrically excitable, it
limits action potentials across the heart to specific pathways

229
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

230
Conducting System of the heart
 Cardiac muscle cells have an intrinsic ability to generate and
conduct impulses that signal them to contract rhythmically
 These properties are intrinsic to the heart muscle itself and do
not depend on extrinsic nerve impulses
 Even if all nerve connections to the heart are severed, the
heart continues to beat rhythmically
 The conducting system of the heart is a series of specialized
cardiac muscle cells that carries impulses throughout the
heart musculature, signaling the heart chambers to contract
in proper sequence
 The components of the conducting system are:
– Sinoatrial (SA) node
– Internodal fibers
– Atrioventricular (AV) node
– Atrioventricular bundle
– Right and left branches
– Purkinje fibers

231
SA (Sinoatrial) node
 Crescent shaped mass of muscle cells located
anterolaterally deep to epicardium in the wall of
the right atrium, below the entrance of the SVC
near superior end of sulcus terminalis
 Initiates and regulates the impulses for contraction
 The heart’s own pacemaker, sets the basic heart
rate by generating 70-80 impulses per minute
 Impulses from the SA node spread in a wave
along the cardiac muscle fibers of the atria
signaling the atria to contract

233
AV (atrioventricular) node
 Collection of nodal tissue located in the posteroinferior part
of the interatrial septum near opening of coronary sinus
 Some impulses travel along the internodal pathway to the
(AV) node, where they are delayed for a fraction of a
second
 After this delay, the impulses race through the atrio-
ventricular bundle which enters the interventricular septum
and divides into right and left bundle branches
 The brief delay of the contraction signaling impulses at the
AV node enables the ventricles to fill completely before they
start to contract
 Because the fibrous skeleton between the atria and
ventricles is non conducting, it prevents impulses in the
atrial wall from proceeding directly on to the ventricular
wall
 As a result, only those signals that go through the AV node
can continue on

234
Atrio-ventricular (AV) bundle
 Is the only bridge of conduction between atrial and
ventricular myocardium
 Passes through fibrous skeleton of heart and along
membranous part of interventricular septum
 At junction of membranous and muscular parts of the
septum it divides into right and left bundle branches
 The bundles proceed on each side of muscular septum and
ramify into subendocardial branches called Purkinje fibers
which approach the apex of the heart, then turn superiorly
into the ventricular walls
– This arrangement of conducting structures ensures that the
contraction of the ventricles begins at the apex of the heart and
travels superiorly, so that the ventricular blood is ejected superiorly
into the great arteries

235
Summary of conduction
 SA node initiate impulse
 Conduct to cardiac muscle fibers in atria
causing them to contract
 Impulse reach AV node
 Distribute through AV bundle and
branches to purkinje fibers to papillary
muscles and walls of the ventricles

236
Histology of the heart
Endocardium (tunica intima)
– Single layer of endothelial cells + thin subendothelium
– Between endocardium and myocardium is subendocardial
layer
– Subendothelial layer of collagenous and elastic fibers,
fibroblasts and some smooth muscle cells
– Subendocardial layer of connective tissue with blood
and lymphatic vessels, nerve fibers, and Purkinje fibers
of the heart's conducting system
Myocardium – (tunica media)
– Cardiac muscle fibers, bundled in spiraling sheets,
thickest in the left ventricle, thinnest in the atria
– Blood vessels and lymphatics and fine connective tissue

237
Epicardium (tunica adventitia)
– Serous covering (visceral pericardium)
– Covered externally by mesothelium
– Subepicardial layer between epi and myocardium
 Layer of adipose tissue
 loose subepicardial CT of fat cells and collagen
fibers with blood vessels (coronary), lymphatics
and nerves to the heart nodes

238
Cardiac Muscle Tissue
 Cardiac muscle occur only in the heart
 is striated but involuntary
 fibers are short, fat, branched and interconnected
 Two or three centrally located nuclei
 Cardiac muscle cells are interlocked by intercalated
discs and function as a single unit
– These gap junctions allow action potentials to spread
easily from one cardiac muscle fiber to the next
– can contract synchronously so each chamber of the heart
can pump blood effectively
 Have T-tubule associated with one sarcoplasmic
reticulum forming diad
 Only hypertrophy

239
Purkinje myocytes and nodal cells
 the cells of the nodes and AV bundle are small,
but otherwise typical cardiac muscle cells
 Each Purkinje fiber, by contrast, is a long row of
special, large-diameter cells called Purkinje
myocytes
 Purkinje myocytes are cardiac muscle cells
containing relatively few myofilaments because
they are adapted more for conduction than
contraction
 Their large diameter maximizes the speed of
impulse conduction

241
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
 arise as branches of the Vagus nerve in the neck and thorax
 Postsynaptic cell bodies are located near SA and AV nodes and
along coronary arteries
 Parasympathetic stimulation slows the heart rate, reduces force
of contraction and constricts coronary arteries
Sympathetic nerves
 from the cervical and upper thoracic chain ganglia
 Postsynaptic fibers end in SA and AV nodes and along coronary
arteries
 Sympathetic stimulation increases the rate and force of heart
contractions and produce dilation of coronary arteries

242
 All nerves serving the heart pass through the
cardiac plexus on the trachea before entering the
heart
 They project most heavily to the SA, AV nodes
and the coronary arteries and some to cardiac
muscles
 Cardiac centers in the reticular formation of the
medulla of the brain control these fibers
– cardioinhibitory center influences parasympathetic
neurons
– cardioacceleratory center influences sympathetic
neurons
– Cardiac centers are influenced by higher brain regions;
hypothalamus, periaqueductal gray matter, amygdala,
and insular cortex

244
Parasympathetic innervation

246
Coronary Circulation
 The blood supply of the heart
 the shortest circulation in the body
 There are anastomosis between blood vessels
 Consume 1/20 of the whole blood supply to the body
 Course just deep to epicardium, embedded in fat
 The right and left coronary arteries arise from aortic
sinuses at proximal part of ascending aorta

248
Right coronary artery
 Arise from right aortic sinus and runs in coronary groove
 Near its origin it gives off SA nodal branch that supply SA
node
 It then courses to the right side of the heart in coronary
groove where it gives off the right marginal branch which
supplies the lateral part of the right side of the heart
 Then it turns to the left and continues in posterior part of
coronary groove
 At crux of heart (junction of septa and walls of heart
chambers) it gives rise to AV nodal branch
 Then gives off posterior inter-ventricular branch that runs in
posterior interventricular groove to the apex of the heart
– Supplies both ventricles and sends interventricular septal
branches
 Terminal branch continues for short distance in coronary
groove

249
 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)

250
The left coronary artery
 Arise from left aortic sinus and passes between left
auricle and pulmonary trunk in coronary groove
 Near its origin it gives off SA nodal branch that supply SA
node
 At left end of coronary groove where it divides into its
major branches
– Anterior interventricular branch
– Circumflex branch
 Anterior interventricular branch passes along the
interventricular groove to the apex
– It turns around and anastomose with posterior interventricular
branch of the right
– Supplies both ventricles and interventricular septum
– It also gives lateral (diagonal) branch
 The circumflex branch follows coronary groove to
posterior surface
– In 40% of people SA nodal branch arises from it
– It also gives left marginal artery which supplies left ventricle

251
 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)

252
Veins of the heart
 the heart is drained mainly by veins that drain into
coronary sinus which empties into the right atrium
Coronary sinus
 Wide venous channel that lies in the left part of coronary
sulcus
 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

255
Lymphatic drainage of heart
 Lymphatic vessels in myocardium and
subendocarial tissue pass to subepicardial
lymphatic plexus
 Vessels from the plexus follow coronary
arteries
 A single vessel ascends between
pulmonary trunk and left atrium and ends
in inferior trachiobronchial lymph nodes

256
Posterior mediastinum
 A space behind the pericardium
and diaphragm
 Boundaries
– Posteriorly – thoracic
vertebrae ( T5- T12)
– Anteriorly
 Above – pericardium (left
atrium), bifurcation of
trachea, pulmonary
vessels
 Inferiorly – posterior part
of diaphragm
 Laterally – mediastinal
pleura

257
Contents
• Esophagus
• Descending thoracic aorta and its branches
• Thoracic duct
• Right lymphatic duct
• Azygos system of veins
• Thoracic sympathetic trunk and splanchnic nerves
• Vagus nerve
• Lymph nodes

260
Clinical importance
 Posterior mediastinum is continuous through superior
mediastinum with neck between the pretracheal fascia
and prevertebral fascia which includes:
 retropharyngeal space
 lateral spaces to trachea and esophagus
 spaces between the two tubes (esophagus & trachea) and
carotid sheaths
 Infection from these spaces can spread to superior and
posterior mediastina

261
Descending thoracic aorta
 Course
– Begins on the left side of the lower border of the body
of T4
– Descends with inclination to the right
– Terminates at lower border of T12 where it passes
through the aortic hiatus
 Relations
– Anterior: root of left lung, pericardium and heart,
esophagus, diaphragm
– Posterior: vertebral column, hemiazygos vein
– To the right side: esophagus, azygos vein, thoracic duct,
right lung and pleura
– To the left side: left lung and pleura
– The greater splanchnic nerve from the sympathetic trunk
joins the descending aorta and enters the abdomen with
it

263
Branches
• two left bronchial arteries
• esophageal arteries – supplying middle 1/3 of
esophagus
• Pericardial branches
• Mediastinal branches
• Right & left posterior intercostal arteries for 3rd -11th
intercostal spaces
• Right and left subcostal
• Right and left superior phrenic

265
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 superior vena cava at the level of T4

266
Tributaries
1. Right superior intercostal vein
2. Right 5 – 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 hemiazygos azygos vein

267
Hemiazgos 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

268
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

269
Remember
 The right superior intercostal vein joins the
azygos after draining the 2nd, 3rd, 4th right
intercostal spaces
 The left superior intercostal vein joins the left
brachiocephalic vein by crossing the anterior
aspect of the aortic arch
 The highest posterior intercostal veins drain the
1st intercostal space and join the
brachiocephalic veins
 The anterior intercostal veins drain into the
internal thoracic veins

271
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 diaphragm at the level of the rib 7 costal
cartilage (T10)
 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
teeth

272
Relations
 Anterior : trachea, right pulmonary artery, left
bronchus, base of the heart (left atrium) and
diaphragm
 Posterior: vertebral column, thoracic duct, right
posterior intercostal arteries, azygos and
hemiazygos systems, thoracic aorta, diaphragm
 To the right: right lung and pleura, azygos vein,
right vagus
 To the left: aortic arch, left subclavian artery,
thoracic duct, left lung and pleura, left
recurrent laryngeal nerve, thoracic aorta

274
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)

275
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
 In portal hypertension, dilation of lower esophageal veins called
esophageal varicose  rapture of these veins result in vomiting of
blood

276
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

277
1. Mucosa contains lymphoid structures
A. Stratified squamous epithelium
B. Lamina propria
C. Muscularis mucosae - longitudinal smooth muscle
• Cardiac glands - make neutral mucus, in the mucosa
near the stomach and upper esophagus
2. Sub mucosa
• esophageal glands - acidic mucus, less numerous in
the middle segment of the esophagus
3. Circular (inner) and longitudinal (external)
• skeletal muscle in the upper & smooth muscle in the
lower half
4. Outermost coat
• is adventitia except on a small piece below the
diaphragm; replaced by serosa
Histology of esophagus

278
Epithelium
Lamina
propria
Muscularis mucosae
Submucosa
Circular muscle
Longitudinal
muscle
adventitia
Mucosa
Submucosa
Muscularis Externa
Adventitia

279
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 of the vertebral column
 At T5 cross to left side
 In the root of the neck it arches laterally (C7)
 terminate at the junction between the left subclavian
and left internal jugular veins

280
 Tributaries
– 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

281
Thoracic
duct draining
into
brachioceph
alic V
Thoracic
duct
Cistrena
chyli
Accessory
Azygos
Hemiazygos
Azygos
Intercostal lymph
nodes
Right lymphatic duct

283
Lymph nodes
 Pre-aortic lymph node – anterior aorta and drain the visceral
structures of the mediastinum
 Para-aortic – located along the side of aorta draining the
body wall
• Extend in the posterior intercostal space and then named
as posterior intercostal lymph nodes
• Upper members of posterior intercostal lymph nodes
drain into thoracic duct/right lymphatic duct
• Lower members ( intercostal and diaphragmatic) drain
into the descending intercostal trunk to join the cisterna
chyli

284
 The anterior ends of the intercostal space is
drained through anterior intercostal lymph
nodes (commonly involved in cancer of the
breast)  brachiocephalic veins
 Lower group of paraortic lies on the diaphragm
 Middle Mediastinal group – on the doom of
diaphragm, drain extra peritoneal tissue
beneath diaphragm & bare area of the liver

285
Sympathetic trunk
 Is gaglionated chain one 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 first is commonly fused with inferior cervical ganglion
to form cervicothoracic or stellate ganglion
 Lie at levels of corresponding intervertebral discs and
intercostal nerves
 Approaches to midline as descending downwards
 Lies on
 the neck of first rib
 Head of the ribs 2nd - 10th
 Bodies of 11th & 12th thoracic vertebra

286
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
 Vasomotor – blood vessels
 Secretomotor – sweat glands

287
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 – form 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 renal plexus

289
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

290
Central tendon
• aponeurotic tendon formed by fibers of different
direction
• has three lobes (right, left & median)
Relations of the lobes
• Left – left pleura
• Right – right pleura
• Median – pericardium

291
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 from liver

292
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
8. Splanchnic nerves – pierce the corresponding crus of
diaphragm
9. Hemiazygos vein - pierce the left crus of diaphragm

293
Nerve supply: phrenic (motor and sensory) & lower six
intercostal and subcostal for peripheral part (sensory)
Blood supply:
Arteries
•Superior surface
superior phrenic (thoracic aorta)
musculophrenic and pericardiophrenic (internal
thoracic artery)
•Inferior surface: inferior phrenic
Veins: same
Lymphatic drainage
•Thoracic surface to phrenic nodes
•Abdominal surface to lateral aortic nodes
•The two surfaces communicate freely

anatomy of thorax.ppt

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