torso - thorax overview - cherchi - 1999

8/7/2019 Torso - Thorax Overview - Cherchi - 1999

http://slidepdf.com/reader/full/torso-thorax-overview-cherchi-1999 1/17

Marcello Cherchi’s notes for Gross Anatomy

THORAX Last updated: 12/17/99

(Please let me know of any errors! [email protected])

References:

CH CHUNG, Kyung Won, Gross Anatomy, 3rd ed. Baltimore: Williams & Wilkins, 1995.

CIBA NETTER, Frank H., The CIBA Collection of Medical Illustrations. Volume 5: Heart. New York: CIBA, 1981.

CL CLEMENTE, Carmine, Anatomy: A Regional Atlas of the Human Body, 4th ed. Baltimore: Williams & Wilkins, 1997.

GR WILLIAMS, Peter L. and Roger WARWICK (eds.), Gray’s Anatomy, 36th British ed. Philadelphia: W.B. Saunders Co., 1980.

MA MOORE, Keith L. and Anne M. R. AGUR, Essential Clinical Anatomy. Baltimore: Williams & Wilkins, 1995.

NE NETTER, Frank H., Atlas of Human Anatomy, 2nd ed. East Hanover, New Jersey: Novartis, 1998.

Sapan http://www.uic.edu/~sdesai4/

SA SADLER, Thomas W., Langman’s Medical Embryology, 7th ed. Baltimore: Williams & Wilkins, 1995.

SH JACOBS, John J., Shearer’s Manual of Human Dissection, 7th ed. New York: McGraw-Hill, Inc., 1989.

Also see:

The M1 home page for anatomy: http://www2.uic.edu/stud_orgs/prof/M1/

ANTERIOR THORACIC WALL

Muscle Innervations Blood supplies Origins Insertions Actions

External intercostal Intercostal n. Anterior intercostal

aa. (from internal

thoracic a.)

Inferior border of rib Superior border of rib

below

Elevate ribs

Internal intercostal Ditto Ditto Ditto Ditto Depress ribs

Innermost

intercostal

Ditto Ditto Ditto Ditto Probably elevates ribs



2

Transversus thoracis Ditto (?) Posterior surface of

lower sternum

Internal surface of

costal cartilages 2-6

Depress ribs

Subcostal Ditto (?) Internal surface of lower ribs near their

angles

Superior borders of 2ndor 3rd ribs below Elevate ribs

Levator costarum Dorsal primary rami

of C8-T11

(?) Transverse

processes of T7-T11

Subjacent ribs between

tubercle and angle

Elevate ribs

Serratus posterior

superior

2nd to 5th

intercostal nn.

(?) Ligamentum

nuchae, spinous

processes of C7 to

T3 vertebrae

Superior borders of 2nd

to 4th ribs

Elevate ribs

Serratus posterior

inferior

Ventral rami of 9th

to 12th thoracic

spinal nn.

(?) Spinous processes

of T11 to L2

vertebrae

Inferior borders of 8th

to 12th ribs near their

angles

Depress ribs

Notes

The external intercostal mm. run from the vertebral column around the rib cage up to the costal ligaments. The direction of their

fibers is like the orientation of your forearms when you put your hands in your front pockets.

The internal intercostal mm. run from the sternum around the rib cage to the back, but not up to the vertebral column. The

direction of their fibers is like the orientation of your forearms when you put your hands in your back pockets.

The innermost intercostal mm. are only present in the anterior portion of the thoracic wall. Their fibers are nearly horizontal,

but angled slightly inferomedially.

Clinical correlations

The weakest part of the rib is just anterior to its angle (MA 34). Broken ribs may puncture the pleurae.

In order to avoid damage to the intercostal nerve and vessels (when conducting procedures such as thoracocentesis), the needleis inserted superior to the rib, high enough to avoid the collateral branches (MA 44).

Fascia

Just deep to the muscles of the thoracic wall is endothoracic fascia (CL 92, 154).

Nerves

Left and right phrenic nerves (from C3, 4, 5), innervate the diaphragm (MA 132).



3

Dermatomes are from T1 through T12 (MA 44).

Arteries The internal thoracic a. usually arises from the first part of the subclavian a. (CH 114). It courses superficial to the transversus

thoracis m. and deep to the innermost intercostal m. The internal thoracic a. gives rise to: (MA 57; CL 171).

1. Pericardiacophrenic a.: supplies pleura and pericardium and then accompanies the phrenic n. down to the diaphragm (CH

114).

2. In the first six intercostal spaces, anterior intercostal aa. branch off of the internal thoracic a. These anastomose with the

posterior intercostal aa. (which are branches off the thoracic aorta).

3. At the sixth intercostal space, the internal thoracic a. terminates by branching into (CH 114):

a. Superior epigastric a., which anastomoses with the inferior epigastric a.

b. Musculophrenic a.: a terminal br. of the internal thoracic a. Supplies the pericardium (MA 57) and diaphragm (MA 132).

Veins

Internal thoracic v. (MA 37).

Osteology There are three types of ribs: (MA 32)

• True (vertebrosternal) ribs (ribs 1-7) attach the vertebrae to the sternum through their costal cartilages.

• False (vertebrochondral) ribs (8-10) have cartilages which attach to the cartilage of the rib above.

• Floating ribs (11 and 12) have cartilages which end in the posterior abdominal musculature.

The 1st rib is called “atypical.” It is “the broadest, shortest, and most sharply curved of the seven true ribs” (MA 33). It is more shelf-

like, and has no angle and no twist. It has a scalene tubercle, which is the insertion point for the scalene m.

The manubrium is at the level of the T3 and T4 vertebrae (MA 34).

Lymphatics

Parasternal lymph nodes (MA 36).



4

Landmarks

The sternal angle, also called the “angle of Louis” or the manubriosternal joint (formed between the planes of the manubrium and

sternum) is at the level of the second pair of costal cartilages (MA 39) and at the level of the intervertebral disc between Tv4 and Tv5(MA 54).

Mnemonics

Spinal nerve origin of phrenic nerves: “C3, 4, 5 keep the diaphragm alive.”

Order of vessels in the subcostal groove from superior to inferior: VAN = vein, artery, nerve.

PLEURAE, LUNGS and BRONCHI

Notes

Concerning respiration (NE 183).

• Passive inspiration relies upon the external intercostals and the diaphragm.

• Forceful inspiration recruits the sternocleidomastoid mm. and the scalenes.

• Passive expiration results from passive recoil of lungs and rib cage.• Forceful expiration recruits the internal intercostal mm. and abdominal mm. (specifically, the rectus abdominis, external

oblique, internal oblique and transversus abdominis mm.).

Dr. Lieska says that generally the intercostal mm. are responsible for maintaining a constant intercostal space during rib elevation and

depression.

Respiration is aided by the following mechanisms:

• Upward and downward “excursion” (movement) of the diaphragm changes the vertical dimension of the thorax.• The “bucket handle” motion of the ribs changes the transverse lateral diameter of the thorax.

• The “pump-handle” motion of the sternum changes the anteroposterior diameter of the thorax.

The root of the lung is the initial branching off from the trachea, and is the area of continuity between the parietal and visceral

layers of pleura (MA 47).



6

The carina is a ridge produced by the last tracheal cartilage. It runs anteroposteriorly between the orifices of the two main

bronchi (MA 77; NE 525; GR 1247).

In the right lung the upper lobar bronchus branches from the primary bronchus almost immediately, even above the pulmonaryartery (and is thus called “eparterial”), while the bronchus directed toward the middle and lower lobes branches below the main stem

of the pulmonary artery (and is thus called “hyparterial” (CL 111).

Clinical correlations

Air, water, blood or lymph entering the pleurae causes pneumothorax, hydrothorax, hemothorax or chylothorax, respectively (MA 47);

these conditions compromise the lungs’ ability to expand. Atelactasis is the generic term for any condition which causes the collapse

of the lung.

When the diaphragm contracts, it pulls downwards and expands the pleurae, thereby helping inspiration. The two sides of thediaphragm are separately innervated: the left half is innervated by the left phrenic n., while the right half is innervated by the right

phrenic n. Thus, it is possible to have hemiparalysis of the diaphragm (MA 42).

Fascia

Between the muscles of the thoracic wall and the pleura there is endothoracic fascia (loose areolar tissue) (CL 92, 154).

Arteries There are two separate arterial systems to the lungs:

1. The bronchial arteries (which arise from the thoracic aorta) supply the parenchyma of the lungs. Usually there is one

bronchial artery for the right lung and two for the left lung (CH 121).

2. The pulmonary arteries (which arise from the pulmonary trunk exiting the right ventricle) send poorly-oxygenated blood to

the lungs in order for gas exchange to occur. The arteries to the individual bronchopulmonary segments are intersegmental

(i.e. within the segments).

Veins There are two separate venous systems from the lungs:

1. The bronchial veins from the right lung are tributary to the azygos v.; the bronchial veins from the left lung are tributary to the

accessory hemiazygos v. (CH 121).

2. The pulmonary veins from the individual bronchopulmonary segments are intersegmental, i.e. they run between the

individual segments (CH 120). They bring oxygenated blood from the lungs to the left atrium.



7

Osteology

The expansion and contraction of the rib cage is facilitated by the fact that each rib articulates with each thoracic vertebra at three

points, thereby forming a sort of “hinge.” The three points of articulation are (NE 171; CL 96):

1. The inferior facet of the head of the rib articulates with superior costal facet of the subjacent thoracic vertebra (of the same

number as the rib)

2. The superior facet of the head of the rib articulates with the inferior costal facet of the suprajacent thoracic vertebra (one

number less than the rib)

3. The tubercle of the rib articulates with the transverse process of the subjacent thoracic vertebra (of the same number)

Landmarks (See MA 49; NE 184-5)

Inferior border of pleura Inferior border of lung

Midclavicular vertical line rib 8 rib 6

Midaxillary vertical line rib 10 rib 8

Midscapular line rib 12 rib 10

The oblique fissure of the right and left lungs extends from the level of the spinous processes of the Tv2 vertebra posteriorly to the6th costal cartilage anteriorly. The horizontal fissure of the right lung extends from the oblique fissure along the 4th rib and costal

cartilage anteriorly (MA 49).

MEDIASTINUM

Notes“It should be understood that the mediastinum is not a single anatomical entity. The term ‘mediastinum’ is applied to the entire

complex of structures that lie between the right and left mediastinal pleurae” (SH pp. 99-100).

The mediastinum is divided into the superior mediastinum and inferior mediastinum by the plane horizontal plane passing through

the sternal angle and the intervertebral disc between Tv4 and Tv5 (MA pp. 54, 68). The superior mediastinum extends superiorly

slightly into the neck. The inferior mediastinum extends inferiorly to the diaphragm.



8

The superior mediastinum (MA 68) contains the following structures:

• Phrenic and vagus nn.

• Cardiac plexus of nn.• Trachea

• Left recurrent laryngeal n.

• Esophagus

• Thoracic duct

• Prevertebral mm.

The inferior mediastinum is in turn divided into three compartments:

• Anterior mediastinum (between sternum and pericardium). Contains only fat (MA 79).• Middle mediastinum (pericardium)

• Posterior mediastinum (between pericardium and vertebral column)

The left primary bronchus crosses anteriorly to the esophagus (CH 117).

Nerves

The right phrenic n. passes anteriorly to the root of the right lung (MA pp. 70, 74; NE 182).The left phrenic n. passes anteriorly to the root of the left lung and runs along the pericardium (MA 74; NE 182) with the

pericardiacophrenic artery (MA 71).

The phrenic nn. carry motor input to all of the diaphragm, as well as sensory input from the central part of the diaphragm. Sensory

input from the peripheral regions of the diaphragm are carried by intercostal nn. (T5-T11) and subcostal nn. (T12) (MA 132).

The vagus n. (on each side) descends and passes posteriorly to the root of the lung. It gives of a branch called the recurrent

laryngeal n.1

Note that this branch is given off higher on the right than on the left.

Various plexuses: cardiac (CL 118, 152), esophageal (CL 152), pulmonary (CL 115, 151), tracheal, pharyngeal (CL 551).

1Claudius Galen (129 C.E. - ca. 215 C.E.) “discovered the function of the recurrent laryngeal nerve by dissection and ligation” (Robert AUDI [ed.], The

Cambridge Dictionary of Philosophy, Cambridge University Press, 1998, p. 291). We will learn in the anatomy of the head and neck that the great cerebral vein

bears the eponymous name of Galen (see NE 97-8).



9

Arteries

The pericardiacophrenic a. courses anteriorly to the root of the left lung and runs along the pericardium with the left phrenic n. (MA

71).

Veins

On the right side of the mediastinum, the azygos v. is a tributary to the superior vena cava (CL 115; MA 57) The arch of the azygos

v. passes superiorly (in a posterior to anterior direction) over the right bronchus (CH 117; CL 115).

On the left side of the vertebral column there ascends the hemiazygos v. which crosses the vertebral column at approximately

Tv9 and and is tributary to the azygos v. Also on the left side of the vertebral column there descends the accessory hemiazygos v.

which crosses the vertebral column at approximately Tv8 and is tributary to the azygos v. (CL 117; MA 53; CH 131).

Tributaries to the azygos v.:

• Bronchial vv. from right lung (CH 121)

• Hemiazygos v. (CL 117; MA 53; CH 131)

• Accessory hemiazygos v. (CL 117; MA 53; CH 131)

• Posterior intercostal vv. on the right side (CH 132)

• Right ascending lumbar v. (CL 148)

Landmarks

Several structures pierce the diaphragm through hiati at the following levels of thoracic vertebrae:

Inferior vena cava hiatus Tv8

Esophageal hiatus Tv10

Aortic hiatus Tv12

MIDDLE MEDIASTINUM is defined by the HEART (actually, by the pericardial sac)

Notes

The flattest part of the heart is its diaphragmatic surface.

The left margin of the heart is called oblique because of its relatively rounded angle.



10

The right margin of the heart is called acute because of its relatively sharp angle.

The most anterior coronal plane eclipsing the heart passes through the right ventricle.The middle coronal plane eclipsing the heart passes through the right atrium and left ventricle.

The most posterior coronal plane eclipsing the heart passes through the left atrium.

The heart consists of several layers (MA 55):

1. Fibrous pericardium

2. Serous pericardium, consisting of

a. Parietal layerb. Visceral layer (continuous with epicardium)

3. The heart proper

a. Epicardium (continuous with the visceral pericardium)

b. Myocardium

c. Endocardium

Blood flows through the heart as follows:

The blood returns from the venous system in a state of LOW OXYGENATION.

Through the vena cava

(There is no valve covering the orifice between the vena cava and the right atrium)

Into right atrium

Through tricuspid valve (=right AV valve) (which guards the right atrioventricular orifice)

Into right ventricle

Through the pulmonary valve (a semilunar valve with three cusps)Into the pulmonary trunk and the pulmonary arteries

Through the lungs. The blood is now OXYGENATED.

Back from the lungs through the pulmonary veins

(There is no valve covering the orifice between the pulmonary vein and the left atrium)

Into the left atrium

Through the mitral valve (=bicuspid valve or left AV valve) (which guards the left atrioventricular orifice)



11

Into the left ventricle

Through the aortic valve (a semilunar valve with three cusps)

Into the (ascending) aorta

Note that for the purposes of anatomical nomenclature, the terms “artery” and “vein” refer to whether the blood is flowing from or to

the heart, respectively; the terms do not refer to the blood’s state of oxygenation.

The atria are separated by the interatrial septum. On the right atrial side of this septum is a thumbprint sized fossa ovalis (which

embryonically was the foramen ovale) (MA 60). The rim of tissue around the foramen ovale is called the limbus (CL 130). The

ventricles are separated by the interventricular septum (MA 61).

Both atria have a rough muscular part with ridges called musculi pectinati (MA 60, 62).

Both ventricles have a rough muscular part with ridges called trabeculae carneae (MA 61).

The interior of the right atrium has a smooth, thin-walled posterior part called the sinus venarum, which receives the venae cavae and

coronary sinus. It also has a rough, more muscular anterior part with ridges (the musculi pectinati). These rough and smooth parts are

separated externally by a shallow vertical groove called the sulcus terminalis and internally by the crista terminalis (MA 59-60; CL

129-130).

The sulcus terminalis is the dividing line between the vascular tissue of the vena cava and the myocardial tissue of the heart (MA 60;

CL 120, 123, 125).

The part of the heart leading into the pulmonary trunk is called the conus arteriosus (MA 61).

The cusps of the valves are as follows (CL 122; NE 210):

Tricuspid valve (right AV valve)

1. Anterior cusp

2. Posterior cusp

3. Septal cusp

Mitral valve (left AV valve, bicuspid valve)

1. Anterior cusp

2. Posterior cusp



12

Pulmonary valve

1. Anterior semilunar cusp

2. Right semilunar cusp3. Left semilunar cusp

Aortic valve

1. Right semilunar cusp

2. Left semilunar cusp

3. Posterior semilunar cusp

Clinical correlations A valvular stenosis entails the valve becoming narrower and harder, making it harder to open. In aortic valve stenosis the left

ventricle must pump harder, and over time there will develop a ventricular hypertrophy (MA 62), which will show up on an EKG as a

left axis deviation.

A valvular insufficiency (or incompetence) entails a valve that does not close completely, resulting in retrograde flow or

regurgitation of blood during diastole. In left antrioventricular valvular incompetence blood flows backwards from the left ventricle

into the left atrium. This results in a heart murmur (MA 62).

A valvular prolapse means that upon closure the valve everts beyond normal, thereby permitting retrograde flow (like an

insufficiency).A small atrial septal defect (literally a hole) appears in the superior part of the fossa ovalis in up to 25% of people. Small

atrial septal defects are usually of no clinical significance, but large ones allow oxygenated blood from the lungs to be shunted from

the left atrium through the defect into the right atrium. This overloads the pulmonary system and causes enlargement of the right

atrium and ventricle (which will show up on an EKG as a right axis deviation) and dilation of the pulmonary trunk (MA 60).

Nerves

The sympathetic innervation to the heart is through nerves from the cardiac plexus. The parasympathetic innervation is through the

vagus nerve (CN X) (MA 67-8). When an impulse is initiated in the sinuatrial node, it courses along the following pathway (MA 66-

7; CL 137):

1. SA (sinuatrial) node

2. AV (atrioventricular) node

3. Bundle of His

4. Moderator band



13

5. Purkinje fibers

Arteries The left and right coronary aa. exit the aorta immediately through orifices just behind the left and right cusps, respectively, of the

aortic valve. The left and right arteries pass underneath the left and right auricles, respectively.

Veins

The right internal jugular v. and right subclavian v. are tributaries to the right brachiocephalic v.

The left internal jugular v. and left subclavian v. are tributaries to the left brachiocephalic v.

The right and left brachiocephalic vv. are tributaries to the superior vena cava.

Into the coronary sinus there empty the following veins (CIBA 16 is a great illustration; see also CL 130; MA 67):

• great cardiac v. (runs on the left side of the atrioventricular sulcus with the circumflex branch of the left coronary a., and then in

the anterior interventricular sulcus with the anterior interventricular a.)

• left marginal v.

• left posterior ventricular v.

• middle cardiac v. (runs in the posterior interventricular sulcus with the posterior interventricular a.)

• small cardiac v. (runs on the right side of the atrioventricular sulcus along with the right coronary a.)

The coronary sinus itself drains into the right atrium (CL 130) through an ostium (“little mouth”) which is covered by a small leaflet

(which functions as a valve).

The thebesian vv. (CL 130) are very small veins which transverse the myocardium perpendicular to its surface all over the heart,

though they are concentrated around the right atrium (CL 130).

Anastomoses See MA 65.

Ligaments

The ligamentum arteriosum runs between the left pulmonary artery and the aorta. It is the remnant of the fetal ductus arteriosus

which, before birth, served to shunt blood from the pulmonary trunk into the aorta for systemic distribution (CL 124, 140-1; MA 69;

NE 217), thereby bypassing the lungs. At birth, the enzyme bradykinin is released, which causes the constriction of the ductus

arteriosus (SA 226).



14

Landmarks

(See MA 63)

The valves all lie roughly behind the sternum in the following fashion (see CL 113; CH 127; CIBA 22):

Rib Valve More specific position

3 Pulmonary At sternochondral joint of 3rd left rib

3.5 Aortic At left part of sternum at the level of the 3rd intercostal space4 Mitral At sternochondral joint of left 4th rib

4.5 Tricuspid Behind midline of sternum at the level of the 4th intercostal space

Ascultation of the various valves must be done “downstream” from their anatomical location. The ascultatory areas of the normal

heart are roughly at the corners of a rectangle (traced on the left upper chest) whose medial border lies along the length of the sternum

and manubrium (see CIBA 74). More specifically (see MA 63):

STRUCTURE LOCATION IN RELATION TO SURFACE ANATOMY

Pericardial sac, generally Lies posterior to the body of the sternum and the 2nd to 6th costal

cartilages at the level of T5-T8 vertebrae (MA 55).

Pericardial sac, left side Related anteriorly to the sternum, costal cartilages and medial

ends of the 3rd to 5th ribs on the left side (MA 58).

Superior vena cava Opens into the superior part of the right atrium at the level of the

right 3rd costal cartilege (MA 60).

Inferior vena cava Opens into the inferior part of the right atrium almost in line withthe superior vena cava (MA 60).

Pulmonary valve Located at the apex of the conus arteriosus, which located at the

sternal end of the 3rd left costal cartilege (CL 113, MA 61).

Right atrioventricular orifice (and tricuspid valve) Located posterior to the body of the sternum at the level of the 4th

and 5th intercostal spaces (CL 113, MA 61).

Left atrioventricular orifice (and mitral valve) Located posterior to the 4th left sternocostal joint (CL 113, MA

62).



16

(1) The ascending aorta, exiting the left ventricle and proceeding up to the horizontal plane which eclipses the manubriosternal

joint.

(2) The aortic arch, which curves leftwards and posteriorly.(3) The descending aorta (or thoracic aorta), proceeding from the distal end of the aortic arch inferiorly.

The aortic arch gives off three branches superiorly in the following order:

(1) Brachiocephalic a., which later branches into

(1a) Right common carotid a.

(1b) Right subclavian a.

(2) Left common carotid a.

(3) Left subclavian a.

The aortic arch passes superiorly over the left primary bronchus (CL 146-7, 152).

The descending aorta (=thoracic aorta) gives off the following branches (CH 131):

• Esophageal aa. (CL 147)

• Bronchial aa. (CL 147) which supply the pulmonary parenchyma.

• Mediastinal aa. which supply the pulmonary pleurae.

• Nine pairs of posterior intercostal aa.; from each such a. there is also a collateral branch. The posterior intercostal aa.

anastomose with the anterior intercostal aa. (which are branches off the internal thoracic a.).

• One pair of subcostal aa.

• Superior phrenic a.

Veins

The posterior intercostal vv. on the right side are tributaries to the azygos v. Those on the left side are tributaries to the

brachiocephalic v. (CH 132).

Lymphatics

The intestinal lymphatic trunk and the right and left lumbar lymphatic trunks (CL 156) converge in the abdominal cavity (just

inferior to the diaphragm) and in the thoracic cavity (just superior to the diaphragm, after coming through the aortic hiatus) form the

cisterna chyli at Lv2 (CL 243). The cisterna chyli then leads into the thoracic duct at Lv1 (CL 149).

The cisterna chyli is the lower dialated end of the thoracic duct which lies posterior to and just to the right of the aorta, usually

between the two crura of the diaphragm; it is formed by the intestinal and lumbar lymph trunks (CH 176; CL 149).



17

The lymphatic tributaries to thoracic duct (MA 78; CL 151, 156; CH 132; NE 296) begin in the abdomen. The thoracic duct

collects the lymphatic drainage for all of the body except the right upper quadrant (CH 132-3). It enters the thorax through the aortic

hiatus, slightly to the right of the midline. It then ascends through the posterior mediastinum just ventral to the vertebral column,between the aorta and the azygos vein. It gradually crosses from the midline to the left. It ascends to the root of the neck and empties

into the junction of the left internal jugular vein and left subclavian vein (CL 156-7).

The right upper quadrant of the body is drained by the right lymphatic duct, which empties into the junction of the right

internal jugular and subclavian veins (CH 132-3; CL 156-7).

Landmarks

The sternal angle is an important landmark:

• At this level the trachea bifurcates.• Superior to this level is the arch of the aorta.

• Inferior to this level is the pericardial sac.

torso - thorax overview - cherchi - 1999

Documents