Anatomy of the thorax 4

Question 1

What is other name for the cardiac skeleton and what is the function of this skeleton?

Answer 1

annulus fibrosus

attachment of the valves

Question 2

What is the cardiac skeleton and what does it surround?

Answer 2

• A fibrous structural support for the chambers of the heart
• Collection of dense, fibrous tissue in the form of four rings which interconnect in a plane between the atria and ventricles
• It surrounds the AV orifices, aortic orifice and opening of pulmonary trunk

Question 3

What is the function of the cardiac skeleton?

Answer 3

• They help maintain the integrity of the openings and provides attachment for cusps and prevents them from malfunctioning. It also helps to provide a point of insertion for the bundles of heart muscle, separating the atria from the ventricles
• Separates the muscular wall of atria from ventricles, as well as electrically isolating the ventricles – the AV bundle is the single connection between these two groups of myocardium

Question 4

Label the fibrous rings of the valves

Answer 4

On image

Question 5

What does the AV do?

Answer 5

• We can see the AV bundle, part of the conduction system that allows the electrical activity to cross fibrous ring from atria to ventricle

Question 6

How many papillary muscles are in the right ventricle and how are they named?

Answer 6

papillary muscles in right ventricle
• Named relative to their point of origin
• Anterior: largest
• Posterior: may consist of 1-3 structures
• Septal: inconsistent (small or absent)

Question 7

Describe the path and function of the moderator band

Answer 7

• Septomarginal trabecula (moderator band) – useful landmark to differentiate between the ventricles (development congenital heart disease). Muscle extends from intraventricular septum to the margin of the right ventricle. Joins base of anterior papillary muscle. Transmits conduction to the anterior wall of the right ventricle, so we get contraction all over ventricle to apex
• Bridge between lower interventricular septum and base of anterior papillary muscle
• Carries a portion of the cardiac conduction system to anterior wall of right ventricle

Question 8

Name the papillary muscles within the left ventricle

Answer 8

On image

Question 9

What are the aortic sinuses?

Answer 9

• Cusps fill with blood, spaces behind cusps that filled with blood are called the aortic sinuses
• Within the aortic sinuses we have the origin of the coronary arteries

Question 10

What are cardiac Auscultation Points?

Answer 10

• Cardiac auscultation enables heart sounds to be listened to using a stethoscope for cardiac assessment
• Normal heart sounds (lub-dub) are produced by the closure of the valves during a contraction
• Valve sounds travel through the surrounding structures of the thoracic wall
• Placement of the stethoscope differs from the position of the valve being examined (downstream from flow of blood). We listen downstream of the valve to listen to the sound of it
• Palpation of the ribs is used to determine which level a stethoscope needs to be placed

Question 11

What are the 4 Auscultation Points and label them

Answer 11

• Aortic valve: medial end of the 2nd right intercostal space
• Pulmonary valve: medial end of the 2nd left intercostal space
• Tricuspid valve: 4th intercostal space at the lower left sternal border
• Mitral valve: 5th left intercostal space at the mid-clavicular line

Question 12

What part of the aorta lies in the pericardial sac?

Describe the path of the aorta and where it divides

Answer 12

• The ascending aorta lies within the pericardial sac
• The arch of the aorta arches posteriorly behind the manubrium of the sternum and anteriorly to the trachea, becomes the descending aorta at the level of the sternal angle (intervertebral disk between T4 and T5)

Question 13

What are the branches of the aorta?

Answer 13

o - Brachiocephalic trunk (divides into right subclavian and right common carotid
o - Left common carotid
o - Left subclavian

Question 14

Where dos the descending aorta begin and where does it pass?

What forms the medial archial ligament and where it it?

Answer 14

• Begins at sternal angle from the arch of aorta
• Passes down the posterior mediastinum and will then pass into the abdominal region
• Passes through the aortic hiatus of the diaphragm at T12
• Intercrural fibres which pass over the anterior surface of the aorta (medial archial ligament) at T12.

Question 15

Label the descending thoracic aorta

Answer 15

On image

Question 16

Describe the venous drainage of the head and how the brachiocephalic vein forms

Answer 16

• Internal jugular vein – brining blood down from the head, running within the carotid sheath, runs with common carotid artery and the vagus nerve.
• It will then meet the subclavian vein which brings blood from the upper limb
• They will join to form the brachiocephalic vein
• Behind the clavicle we have the subclavian vein joining the internal jugular
• We can also see the left and right brachiocephalic vein

Question 17

What forms the superior vena cava and what does it drain?

Answer 17

• The superior vena cava will be formed by the union of the brachiocephalic veins and ultimately all the body’s veins drain into the superior vena cava and inferior vena cava, except the cardiac veins
• The superior vena cava will receive blood from the head, neck, shoulders and upper limb

Question 18

What does the inferior vena cava drain?

Answer 18

• The inferior vena cava will receive blood from organs inferior to the diaphragm

Question 19

What is the benefit of the azygous venous drainage system?

Answer 19

• The inferior vena cava will receive blood from organs inferior to the diaphragm
• The azygous system of veins provides an alternative route for venous return back to the

Question 20

Label the venous drainage system

Answer 20

On image

Question 21

What does the azygous vein drain?

Answer 21

Receives lower 8 right posterior intercostal veins, right superior intercostal vein and hemizygous veins

Question 22

What does the:

left superior intercostal vein drain?

superior (accessory) hemizygous vein drain?

Inferior hemizygous vein drain?

Answer 22

On image

Question 23

What type of organ is the thymus and what is it involved in the development of?

Answer 23

• Essentially a lymphoid organ

* Involved in the early development of the immune system and is largest, relative to body size, in children

Question 24

Where is the thymus found?

Answer 24

• Found in the superior part of the thoracic cavity and into the neck
• Located in anterior portion of the superior mediastinum lying immediately posterior to the manubrium of the sternum
• Upper apex can reach as high up in the neck as the thyroid gland in infancy
• Lower apex typically extends into the anterior mediastinum over the pericardial sac
• Sits behind the manubrium of the sternum
• Extends into the root of the neck
• Upper apex can each as high into the anterior mediastinum over the pericardial sac

Question 25

What happens to the thymus during puberty?

Answer 25

• Undergoes involution after puberty – decreased in size and is replaced by fat

Question 26

What is the blood supply to the thymus?

Answer 26

• Blood supply is via the anterior intercostal arteries, and internal thoracic arteries. The venous blood will drain into the left brachiocephalic and internal thoracic veins

Question 27

Label the thymus

Answer 27

On image

Question 28

Describe the lymphatic system

Answer 28

• Consists of lymphatic tissues and lymphatic vessels. Collect and filter excess tissue fluid known as lymph
• Lymphatic tissues contain large numbers of lymphocytes e.g. the thymus, the spleen
• Lymphatic tissue is essential for the immunologic defences
• Lymphatic vessels are tubes that assist the cardiovascular system in the removal of tissue fluid from the tissue spaces of the body; the vessels then return the fluid to the blood. To maintain blood volume, important in maintain blood pressure.

Question 29

Describe the general path of a lymph vessel

Answer 29

• Before lymph is returned to the bloodstream, it passes through at least one lymph node
• Enters through the afferent channel into the thymus and leaves via the efferent ch annel
• T and B lymphocytes and other immune cells, and are exposed to fluid to detect pathogens
• Filter lymph
• Congregation of immune cells
• Often de-emphasized as it is difficult to see on a cadaver
• Important for spread of disease

Question 30

Where does the Anterior thoracic wall drain into?

Answer 30

• Anterior thoracic wall drain into parasternal nodes (nodes that run parallel to the sternum) and the diaphragmatic nodes

Question 31

Where does the posterior thoracic wall drain into?

Answer 31

• Posterior thoracic wall drain to intercostal nodes around the head and necks of the ribs

Question 32

What do the lungs drain into?

Answer 32

• Lungs drain into tracheobronchial nodes

* Which drain into the bronchomediastinal lymph trunks into main lymphatic ducts

Question 33

Label the lymph system

Answer 33

On image

Question 34

What is the major lymphatic vessel in the body?

Where does it start?

Where does it bring lymphatic fluid from?

Describe the path and label

Answer 34

• Major lymphatic vessel in the body
• Starts at cisterna chyli (L1) (dilation of the lymphatic channels located in relation to the abdominal aorta)
• Brings lymphatic fluid from abdominal region
• The thoracic duct will enter the thoracic cavity through the aortic hiatus in the posterior mediastinum (just to the right), ascends between aorta and azygous vein. Posterior to oesophagus. Crosses to the left of the midline (T4-T6) and continues superiorly through the superior thoracic aperture and receives a number of trunks to join and drain into it. The bronchomediastinal lymph trunks drain into the thoracic duct and its counterpart on the right
• Passes behind the arch of the aorta to enter the left brachiocephalic vein

Question 35

What are the divisions of the nervous system and what does it react to?

Answer 35

On image and Reacts to internal and external changes in actibity and regulates a number of functions in the body

Question 36

What does the autonomic, enteric and sympathetic and parasympathetic nervous system supply?

Answer 36

Autonomic nervous system is not under conscious control, contains motor nerves that control involuntary functions of the body organs and viscera (smooth and cardiac muscle)

Enteric – nervous system that is local to the GI tract

Sympathetic and parasympathetic nervous system – focus of the thorax

Question 37

Compare the parasympathetic nervous system and sympathetic nervous system

Answer 37

• Sympathetic division is active during periods of exertion, stress or emergency
• “Fight or Flight”
• Parasympathetic division active under resting conditions
• “Rest and Digest”

Question 38

What does it mean when the sympathetic nervous system has thoracolumbar outflow?

Where does the SNS originate?

What do some of these neurones pass out to form?

What does a pre-ganglionic neurone form?

Answer 38

• The SNS has a thoracolumbar outflow which means that the neurones are found in the spinal cord at levels T1-L2/L3. They originate from the lateral horn of grey matter of the spinal cord in the thoracolumbar region
• Some of these neurones then pass out and synapse in ganglia which are associated with either side of the vertebral column (paravertebral ganglia). The ganglia are connected, some of the nerves will come out and pass up to the head and neck or lower limb. We require sympathic innervation throughout the body. Ganglia are joined together to form the sympathetic chain on each side of the vertebral column
• Pre-ganglionic neurone -> synapse within ganglia to form the post-ganglionic neurone towards the target organ such as smooth muscle within the heart or bronchopulmonary tree, or GI tract.
• Some specialist nerves pass into the sympathetic ganglion and don’t synapse, they then pass through the sympathetic chain as pre-ganglionic fibres towards the target organs

Question 39

What are the Thoracic Splanchnic Nerves formed by?

What do they supply?

Describe there path

Answer 39

Nerves that don’t synapse in the sympathetic chain

• The lower 8 ganglia of the sympathetic chain mainly give pre-ganglionic fibres, which are grouped together to form thoracic splanchnic nerves and supply abdominal viscera. They originate within the thoracic region but supply abdominal organs.
• Preganglionic fibres pass through the sympathetic chain without synapsing
• Instead they synapse in separate prevertebral ganglia (located around the blood vessels of the aorta that supply the abdominal region (GI tract)). These run anterior to the vertebrae
• Postganglionic fibres leave ganglia to innervate visceral tissues and organs within abdominopelvic cavity

Question 40

What are the divisions of the thoracic splanchnic nerves?

Answer 40

• Greater Splanchnic nerve
o T5-T9
o Synapse in coeliac ganglion (follow artery) – organs of the foregut, superior part of GI tract
• Lesser Splanchnic nerve
o T9/- T12
o Synapse in superior mesenteric ganglion (follow artery) – organs of the midgut
• Least Splanchnic nerve
o T12
o Synapses in aorticorenal ganglion - kidneys
• Lumbar splanchnic nerves
o L1-L2
• Synapse in the inferior mesenteric ganglion - hindgut

Question 41

Describe the phrenic nerves

Answer 41

• Originates from the cervical plexus, descends through the neck to innervate the diaphragm, only source of motor innervation to the diaphragm
• Contains motor, sensory, and sympathetic nerve fibers
• Provides the only motor supply to the diaphragm (C3, 4, 5 keeps the diaphragm alive) as well as sensation to the central tendon. In the thorax, each phrenic nerve supplies sensation to the mediastinal pleura and pericardium
• The right phrenic nerve will pass over the lateral part of the right subclavian artery and will enter the thorax via the superior thoracic aperture and will descends anteriorly along the lung route across the pericardium of the heart and will enter diaphragm at the opening of the inferior vena cava. Innervates inferior surface of the diaphragm
• The left phrenic nerve will enter the superior thoracic aperture, it descends anterior to the left lung route and then will cross the aortic arch and bypass the vagus nerve and courses along the pericardium of the left ventricle and enters the diaphragm. The left provides motor innervation to diaphragm and brings sensory fibres for central diaphragm and pleura, membranous lining of abdominal region

Question 42

Describe the path of the phrenic nerves

Answer 42

• Enters the superior mediastinum lateral to vagus nerve and behind the brachiocephalic veins
• Passes anteriorly to the hilum of the lung and over the pericardium of the heart sending small pericardial branches to it

Question 43

What does the vagus nerve provide innervation to?

Answer 43

• Cranial Nerve 10 (X)
• Autonomic control of the heart and digestive tract
• Supplies motor parasympathetic fibers to all the organs except the suprarenal (adrenal) glands, from the neck down to the second segment of the transverse colon including the heart and lungs, gives of cardiac branches and also supplies GI tract
• Controls a few skeletal muscles
o Superior, middle and inferior pharyngeal constrictors
• Muscles of the larynx (Recall recurrent laryngeal)