HP 3003 Human Gross Anatomy
Fall 2001
Lecture 2 - Thorax
I. Trunk
Thoracic cavity
Abdominopelvic cavity
Divided by the diaphragm
Two diaphragms exist in the trunk:
1) between the abdominal cavity and thoracic cavity
2) low in the pelvic region, between the perineum and the
pelvic cavity-pelvic diaphragm
II. Thoracic wall:
a. Bones (Ribs, Sternum , vertebrae)
b. In addition to the bones there are a large number of
joints between these bones. The joints are critical for respiratory movements.
c. Muscles
d. Nerves
e. Blood vessels
III. Skeleton
a. forms an osteocartilaginous
thoracic cage that protects the heart and lungs, and some abdominal organs such
as the liver and spleen.
b. 12 thoracic vertebrae and the
intervertebral discs
will study
more with the back
1.costal facets on their bodies for articulation with the heads of ribs
2. costal facets on their transverse processes for articulation with
the tubercles of the ribs , except inferior two or three
3. long spinous processes
c. ribs - 12 pairs
1. first 7 ribs (sometimes 8) are true ribs (vertebrosternal) ribs - attach
vertebrae to sternum by their costal cartilages.
a.first ribs attach to the manubrium of sternum under theclavicle
b. very strong
c. synchondrosis - not synovial joint
2. 8-10 are
called false (vertebrochondral) ribbs because their cartilage attaches to the
cartilage of the rib superior to it.
3. 11 -12th
are free or floating ribs - their cartilages end in the posterior abdominal
musculature
4. costal
cartilages contribute to the elasticity of the thoracic wall - cart. of 7 -10
form infrasternal angle and costal margin
5. spaces
between ribs are the intercostal spaces, and are filled by muscles, nerves and
blood vessels.
6. Typical
rib:
a. head with two articular facets ( same # vert. & one superior)
facets separated by a crest - attaches to intervertebral disc by intra-articular
ligament - 3 point articulation : T of same #, T above, and
disc. #1 only T1, # 11 only T11; # 12 only T12
b. neck
c. tubercle - at junction of neck & shaft (body), has facet that articulates
with the transverse process of rib, and rough area for attachment of
costotransverse ligament.
d. shaft - thin, flat, curved. Angle is the point of greatest change in
curvature.
7. Atypical ribs- 1, 2, 10-12
1st is broadest, shortest and most sharply curved
forms a synchondrosis with sternum, not synovial jt.
body of ribs with cartilage of ribs forms costochondral jt.
chondrosternal jt. - between cart. of 2- 6 & sternum is a
synovial jt.
8-10 interchondral jt. - connected to each other by cart.
8. Sternum
a. forms the middle of the thoracic cage
b. 3 parts: manubrium, body, xiphoid process
c. manubrium- quadralateral - means "handle"
1. articulates with the 1st & 2nd ribs
2. sup. border - jugular or suprasternal notch
3. clavicular notch - articulation with clavicles
4. manubriosternal joint - manubrium & sternum lie in different planes -
form sternal angle or angle of Louis - important clinical landmark.- 2nd
cost. cart.
5. Body - originally 4 separate segements or sternebrae
6. Xiphoid process - in young is cartilage, mostly ossified by age of 40
IV.Thoracic apertures
A. Superior Thoracic aperture -
thoracic inlet
1. transverse diameter> A-P diameter in adults
2. almost circular in neonates
3. boundaries - T1, 1st pair of ribs & cart., sup. border of
manubrium
4. Find trachea, esophagus and apex of lungs
5. blood vessels to upper limb come through the inlet between clavicle & 1st
rib- subclavian v & a are the most important
B. Inferior Thoracic Aperture - Thoracic outlet
1.
communication with the abdomen - covered by the diaphragm
a. structures that pass through - inf. vena cava, esophagus
b. structures that pass behind - aorta
2.
boundaries - T12, 12th ribs, costal cart. of ribs 7-12, xiphisternal
jt.
V. Movements of Thorax
A. changes in A-P , vertical and
transverse diameters of thorax
1. Inspiration increases intrathoracic volume and decreases pressure
2. Expiration is usually a passive process of relaxation of muscles
3. Diaphragm contracts to increase vertical diameter.
4. transverse diameter is increased by action of external intercostals - raise
ribs like bucket handles.
a. accessory muscles of insp. are pect. major and scalenes.
5. Pump handle motion caused by contraction of external intercostals
increases A-P diameter.
VI. Muscles - concentrating only on those that affect the thorax- 11 muscles
each:
Intercostal muscles - 3 layers
A. superficial - external intercostal
muscles
1. muscle fibers run sup. lat. to inf. medial
2. end ant. at costal cartilages - replaced by external intercostal membranes-
fills space like a tendon or aponeurosis
B. middle - internal intercostals
1. muscle fibers run sup. med to inf. lateral
2. replaced post. by internal intercostal membrane
C. deepest - innermost intercostals -
fibers run like internal intercostals
Diaphragm
A. both
voluntary and involuntary muscle fibers
B. innervated
by the phrenic nerve (C3, C4, C5)
C. 3
orifices:
inferior vena cava (T8) (within central tendon)
esophageal orifice (T10) (hiatus hernia)
thoracic aorta (T12)
VII. Nerves
A 12 pairs of thoracic spinal nerves
pass through the intervertebral foramina and divide into ventral and dorsal
primary rami
1. ventral rami of T1-T11 form the intercostal nerves
2. dorsal rami supply the muscle, bones, joints and skin of
the back.
B.
superior
Vein
Artery
inferior
Nerve
C. Dermatomes and myotomes
VIII. Vasculature
Arterial supply:
subclavian
artery
axillary
artery
aorta through
the posterior intercostal and subcostal arteries
Veins accompany arteries
post.
intercostal vv anastamose with the anterior intercostal vein, and most end in
the azygos vein that enters the superior vena cava.
Thoracic Cavity
I. Pleurae - Each lung surrounded by a pleural sac
a. two serous membranes:
parietal pleura
visceral pleura - attaches to lung - inseparable
b. pleural cavity - potential space
between membranes - serous pleural fluid
c. Parietal pleura
costal , mediastinal, diaphragmatic, cervical pleura or cupula of pleura(extends
3 cm into neck)
at lung pedicle, the visceral and parietal pleura are continuous
posteriorly, double layer of parietal pleura called pulmonary ligament
d. Hilum or hilus - where the pedicle
attaches to the lung
e. pleural tap - midaxillary line at
rib 10 ( posterior risk hitting kidney)
II. Lungs
a. apex
b. base
c. root
d. hilum - main bronchus, pulmonary
vessels, bronchial vessels, lymph vessels & nerves
e. lobes - 3 right/ 2 left
f. fissures
1. oblique (from spinous process of T2 in the back to 6th
costochondral junction)
2. horizontal (rt. lung, from oblique fissure to 4th costal
cartilage)
g. surfaces:
1.costal surface
2. mediastinal surface
3. diphragmatic surface
h. borders
1. anterior - costal & mediastinal surfaces meet (on left cardiac notch)
2. inferior - around the diaphragm
3. posterior - costal & mediastinal surfaces meet
i. Primary bronchi -first branching
of the trachea - also c-shaped rings of cartilage
right main bronchus is wider and shorter and more vertical
left main bronchus - passes inferior to aortic arch and anterior to esophagus
carina- at bifurcation -strong cough reflex
Secondary (lobar) bronchi - divide
and pass to lobes of lungs - 3 rt -2 left
Tertiary (segmental) bronchi- supply
bronchopulmonary segments
Bronchioles
Alveoli
Vessels and nerves:
a. each lung has a single large
pulmonary artery - (98 %)branch of pulmonary trunk - deoxygenated blood - also
divides into lobar and segmental arteries.
b. bronchial arteries supply the lung
tissue itself and visceral pleura (2%)- us. arise from aorta
c. pulmonary veins - carry oxygenated
blood to left atrium
d. bronchial veins drain only part of
blood from bronchial arteries, some drains into pulmonary veins. Rt. bronchial
vein drains into the azygos vein, and left bronchial vein drains into accessory
hemiazygos vein or left superior intercostal vein.
Nerves:
1. from pulmonary plexes located anterior.
and posterior to root of lungs
2.Parasympathetic innervation from CN
X - vagus - bronchonstrictor, vasodilator, and cause glands of bronchial tree to
secrete.
3. Sympathetic innervation comes from the
paravertebral ganglia of the sympathetic trunks- effect is opposite to
parasympathetic.
Lung projection on the thoracic wall:
PTE(Pulmonary Thromboembolism):
A common cause of morbidity and mortality. An embolus is formed in far sites of the body such as legs(in the veins). This embolus is transferred to right atrium and eventually into pulmonary arteries. The outcome could be partial or complete obstruction of the blood flow to lung. In this condition the lung is ventilated but is not perfused (deprived from blood). Patient then undergoes acute respiratory distress and may die in a few minutes. This event usually happens when the embolus is very large.
Pleura and lungs:
The pleural cavity is a potential space, containing a small amount of
fluid. This fluid facilitate the movement of the lungs.This cavity is formed
between the parietal pleura and visceral layer of the pleura. The pressure in
this cavity is below the atmospheric pressure. Pleurectomy is a surgical removal
of the pleura. It has been reported that pleurectomy does have not serious
functional effects.
Pneumothorax:
Since the pressure inside the trachea and other respiratory ducts is
higher than the pressure in the pleural cavity, the lugs are normally expanded
by this pressure difference. In traumatic situation when for various reasons the
thoracic wall is peneterated by external objects air rushes into pleural cavity
to equalize the pressure of both sides of the pleural. When the preesure of the
pleural cavity increases the lung tissue collapses and respiration is
jeopardised. Because the two pleural cavities are seperated by mediastinum, each
of the two lungs can be collapsed independent from other side.
It must be understood that pneumothorax is not always because
of external sharp objects or open fracture in traumatic events. If lung tissue
is ruptured following diseases of the lung , there again the air might enters
the pleural cavity and pneumothorax occurs. The most common type of pneumothorax
is spontaneous pneumothorax, when the alveoli in the lung are ruptured.
Sucking pneumothorax or "blowing wound":
Pleural cupulae are above the first rib in the root of the neck. Following
stab wound in this region pleura and possibly the lung is injured. The result is
entering the air into the pleural cavity called open pneumothorax.
Possitive pressure pneumothorax:
In occasion when the lung tissue is as well as visceral pleurae are
ruptured air can enterd the pleural cavity during inspiration ,but can not leave
this space because of a flap closing the openning the amount of air within the
pleural cavity is increased with each cycle. This is considered a medical
emergency, because the increased pressure in the ruptured side will push the
mediastinum toward the opposite side. This compresses the opposite lung and
threatens the respiration.
Hydrothorax:
This is a similar condition to pneumothorax, except that fluid is
accumulated in the pleural cavity instead of air. One of the reasons for
hydrothorax is Pleuritis or pleurisy (inflammation of the pleura). In presence
of pleurisy the surfaces of the pleura become rough and produce a special noise
that can be heard with a stethoscope. This is known as pleural rub.
Hemothorax:
Accumulation of the blood in the pleural cavity is called hemothorax. This
usually occurs following chest wounds, and simply means blood enters and
accumulates in the cavity.
Chylothoarx:
A rare event that gives rise to enetring the lymph into the pleural
cavity.
Mediastinum - central portion of the thoracic cavity
a. from superior thoracic aperture to
diaphragm, and from sternum to thoracic vertebrae
b. divided into superior and inferior
parts:
superior - sup. thoracic aperture to plane passing
through inferior border of T4 and sternal angle. Contains trachea, ascending
aorta, phrenic n., vagus n., superior vena cava, and branches off aortic arch.
inferior - below above plane, and further divided into
ant, middle and post. parts.
middle - contains heart and great vessels, and
bifurcation of the trachea
anterior - thymus (larger in children) and
sternopericardial ligaments
posterior - esophagus
thoracic descending aorta
sympathetic trunks
azygos vein
hemiazygos vein & accessory hemiazygos vein
thoracic duct
beginning of intercostal vessels
Pericardium:
double walled fibroserous sac that encloses the heart
fused with the tunica adventitia of the great vessels
attached to post. sternum by sternopericardial ligaments
attached to diaphragm by the central tendon
Layers:
Outermost layer is fibrous pericardium - tough - protects
against overfilling
parietal pericardium
visceral pericardium (epicardium)
Pericardial cavity
Heart :
layers:
epicardium
myocardium
endocardium - continuous with
endothelium of vascular system
2 pumps in one:
pulmonary circulation
systemic circulation
Four chambers:
Right atrium
right auricle - pouch that overlaps the ascending aorta
divided by vertical ridge of muscle called the crista terminalis
post. - openings of sup. and inf. vena cavae, and coronary sinus, and fossa
ovalis in interatrial septum
ant. - rough wall with ridges - the pectinate muscles
Right ventricle - separated from
right atrium by rt. A/V valve - tricuspid valve
three papillary muscles attached to cusps by tendinous strands
- chordae tendineae
muscular ridges crossing and anastomosing - trabeculae carnae
tapers sup. into cone shaped pouch called conus arteriosus or infundibulum
pulmonary (semilunar) valve located at apex of conus arteriosus -
3 cusps ant., rt, and lft.
interventricular septum -
septomarginal trabecula, curved muscular band - contains right branch of the
atrioventricular bundle of conduction system
Left atrium -
left auricle
- has pectinate muscles
four
pulmonary veins
left
atrioventricular orifice
Left ventricle -
A/V valve is
the mitral or bicuspid valve
2 larger
papillary muscles
wall twice as
thick as rt. vent.
mesh of
trabeculae carnae - finer and more numerous than in rt.
aortic (semilunar)
valve - three cusps, no chordae tendineae
Heart surface-
divided by sulci containing cardiac
vessels
1. coronary sulcus- separation of
atria and ventricles - contains right coronary artery, circumflex branch of left
coronary artery, and coronary sinus.
2. Interventricular sulcus -indicates
separation of right and left ventricles
a.anterior interventricular sulcus contains anterior interventricular branch of
left coronary artery (left anterior descending artery) and great cardiac vein
b. posterior interventricular sulcus contains posterior interventricular branch
of right coronary artery and middle cardiac vein.
Conduction system:
1. sinoatrial node - pacemaker
2. atrioventricular node
3. Atrioventricular bundle
a. right branch - in septomarginal trabecula
b. left branch
Vessels of the Thorax
First branches off the aorta are the coronary arteries:
arise just superior to the aortic valve
supply the myocardium and the pericardium
Right coronary artery-
runs in the
atrioventricular (coronary) groove
usually gives
off a sinuatrial nodal artery to SA node
passes to
inferior border of the heart and gives off right marginal art.
turns to the
left and continues in the post. arterioventricular groove
gives off the
post. interventricular artery (PDA)
near the end
gives off the atrioventricular nodal artery that supplies AV node
Left coronary artery -
passes
between the left auricle and pulmonary trunk to ant. artrioventricular groove.
branches into
the anterior interventricular artery (ADA) runs along interventricular septum to
apex
circumflex
branch of LCA runs in atrioventricular groove, to posterior surface, gives off
marginal branch along left margin of heart
Cardiac veins tend to parallel paths of coronary arteries, and drain into
coronary sinus in post. atrioventricular groove.
Drains into right atrium
Ascending Aorta
Arch of Aorta
ligamentum artriosum - remnant of ductus arteriosus - connects left pulmonary
artery to inferior surface of the arch.
Branches of the arch are:
brachiocephalic trunk
divides into the right common carotid and right subclavian arteries
left common carotid artery - supplies the head
left subclavian artery - supplies the left arm
Thoracic aorta -begins at level of T4, as descends becomes
more medial
passes through the aortic hiatus at T12
Branches:
Bronchial
Esophageal
Pericardial
Mediastinal
Posterior intercostal arteries
9 pairs - 3rd -11th intercostal spaces
Subcostal
Superior phrenic
Internal Thoracic (also called internal mammary a.
runs parallel
to lateral margin of sternum , is larger in women because supplies the breast
tissue.
gives off
anterior intercostal aa.
at the sixth
ribs divides into two terminal branches:
musculophrenic a - goes around the diaphragm
superior epigastric a. - goes to abdominal region
Major Thoracic veins:
2 brachiocephalic veins form the
superior vena cava (only 1 brachiocephalic a.) formed by union of
jugular veins and subclavian veins
Azygous vein - found only on right side - drains into atrium
directly
posterior intercostal veins empty into it, also some from
hemiazygous
Hemiazygous
only on left
side
four lower
posterior intercostal veins drain into this vein
anastamoses
with azygous v on right side
Accessory hemiazygous vein
8 posterior
intercostal veins drain into this vein
only found on
left side, both accessory and hemiazygous veins cross midline and join azygous
as it drains to right atrium
Internal thoracic vein
drains into
the subclavian veins
at 7th
intercostal space the internal thoracic v. splits into
musculophrenic v.
superior epigastric v.