Respiratory Anatomy

Question 1

What is the anatomical position of the tongue?

Answer 1

The tongue fills the floor of the mouth and is attached to the posterior of the ramus of the mandible and hyoid bone

Question 2

What are the boundaries of the oral cavity?

Answer 2

It is bound anteriorly by the lips, laterally by the cheeks, superiorly by the palate and inferiorly by the tongue.

Question 3

Where would one find the palatine tonsil?

Answer 3

you should be able to identify the tonsil on the lateral wall of the oropharynx beyond the posterior third of the tongue.

Question 4

What are the positions of the palatoglossal and palatopharyngeal folds?

Answer 4

· The palatoglossal and palatopharyngeal folds lie in front and behind the tonsillar fossa respectively. These folds are produced by the palatoglossal and the palatopharyngeal muscles.

Question 5

Which constrictor of the pharynx does the tonsil sit on?

Answer 5

The super constrictor

Question 6

What is the tonsil?

Answer 6

· The tonsil is a consolidation of lymphoid tissue which samples organisms which may try to enter the body via the mouth or nose.

Question 7

What is the function of the adenoids and where are they?

Answer 7

They perform a similar function to the tonsil and they lie posterior pharyngeal wall just above the level of the soft palate

Question 8

Describe the palate?

Answer 8

· The roof of the mouth is the palate, it separates the oral and nasal cavities.
· The anterior two thirds of the palate is formed by the palatine processes of the maxillary bones anteriorly and the horizontal plates of the palatine bones posteriorly. This is the hard palate, the bones can be identified on a dry skull.
· The posterior third of the palate, the soft palate, is muscular.
· Examine the soft palate in the living and on the cadaver. Centrally at the posterior border of the soft palate there is a soft conical projection, the uvula. The tensor palatine, levator palatine, musculus uvuli, palatoglossus and palatopharyngeus form the soft palate.
· The function of the soft palate is to control the orifice between the nasal and oral parts of the pharynx. Elevation of the soft palate closes the orifice and this occurs during swallowing to stop reflux of food into the nasopharynx and during phonation to allow the production of explosive consonants
· Both the tensor and levator palatine in their upper parts are attached to the cartilaginous Eustachian tube. Contraction of these muscles opens the Eustachian tube and allows air to enter the middle ear from the nasopharynx

Question 9

What three structures all join the nasal cavity?

Answer 9

The bony sinuses, middle ear and tear duct all join the nasal cavity.

Question 10

Where would one find the openings of the Eustachian tubes?

Answer 10

On the lateral wall of the nasopharynx, in the living there is usually a slight bulge on the pharyngeal wall and the opening is anterior to this

Question 11

What is the nasal septum covered with?

Answer 11

The septum is covered with muco-periosteum, a combination of mucous membrane (respiratory mucosa) attached to the periosteum and perichondrium of the bones and cartilage of the septum

Question 12

What is the bony septum formed from?

Answer 12

The bony septum is mainly formed by the vomer and vertical plate of the ethmoid bones.

Question 13

What lies at the most superior part of the nasal cavity?

Answer 13

At the most superior part of the cavity is the spheno-ethmoidal recess which is adjacent to the cribriform plate

Question 14

What structure passes through the spheno-ethmoidal recess?

Answer 14

Fibres of the first cranial nerve, the olfactory (smell) nerve, pass from the spheno-ethmoidal recess into the cranium and to the brain.

Question 15

Which nerve carries general sensation from the nasal cavity?

Answer 15

General sensation from the nasal cavity is carried in the trigeminal (fifth) cranial nerve. Above the line formed from the opening of the nasal sinus to the spheno-ethmoidal recess is supplied by the ophthalmic division of the trigeminal cranial nerve and anything below is supplied by the maxillary division of the trigeminal cranial nerve

Question 16

What duct drains into the inferior meatus?

Answer 16

Under the inferior concha is a channel, the inferior meatus, and draining into the most anterior part of this meatus is the nasolacrimal duct, it is tiny

Question 17

What structures exist in the middle meatus?

Answer 17

Under the middle concha is the middle meatus; within the middle meatus is a channel, the hiatus semilunaris, and a bulge, the bulla ethmoidalis.
Within the hiatus semilunaris there are three openings, the frontal sinus, most anteriorly, the anterior ethmoidal sinuses, most posteriorly and the maxillary sinus, centrally.

Question 18

What makes the maxillary sinus unique?

Answer 18

Most of the nasal sinuses communicate with the nasal cavity from the lowest part of the sinus, this aids drainage of mucus (and infection).

However, the maxillary sinus drains from near the top of the sinus, this makes it more prone to filling with mucus and sinusitis

Question 19

What drains into the superior meatus?

Answer 19

draining into this are the posterior ethmoid sinuses

Question 20

Where does the sphenoid sinus drain?

Answer 20

The sphenoid sinus drains directly into the spheno-ethmoidal recess

Question 21

What is the connection between dental infection and the maxillary sinus?

Answer 21

Immediately above the maxillary sinus is the orbit and round the lower edge the roots for the upper teeth.
Infection can spread from the teeth to the sinus and disease in the sinus can cause tooth pain.

Question 22

Why can maxillary sinus disease cause pain in the cheek?

Answer 22

Identify a nerve running in the roof of the sinus, this is a branch of the maxillary division of the trigeminal nerve and supplies the cheek.
Disease of the sinus can affect the nerve and cause pain in the cheek.

Question 23

Which nerve runs posteriorly to the maxillary sinus?

Answer 23

Just posterior to the maxillary sinus the greater palatine nerve (Maxillary division of the V cranial nerve) runs in a bony canal to supply the roof of the mouth

Question 24

Why do children born with cleft palate have common ear infections?

Answer 24

Children born with a cleft palate may not have function in the soft palate muscles to open the Eustachian tube during swallowing. They will be at risk of recurrent middle ear infections and conductive deafness.

Question 25

What is a grommet and what is it used to treat?

Answer 25

In children adenoids are close to the opening of the Eustachian tube and persistent enlargement of the adenoids due to repeated throat infections often leads to middle ear infection and conductive deafness. The treatment is to remove the adenoids and create an artificial passage into the middle ear to ‘bypass’ the diseased Eustachian tube. This is done by placing a tiny plastic tube through the ear drum directly into the middle ear cavity; a grommet.

Question 26

What is the function of the Eustachian Tube?

Answer 26

To carry air into the middle ear from the nasopharnyx. This allows pressure to remain equal either side of the ear drum which is essential for hearing and regular function.

Question 27

What are the three structures of the pharynx?

Answer 27

Nasopharynx, oropharnyx, laryngealpharnx/hypopharnx

Question 28

Where does the superior constrictor take origin?

Answer 28

The superior constrictor takes origin from the medial pterygoid plate and the pterygomandibular raphe, which extends from the medial pterygoid plate to the mandible

Question 29

Where does the middle constrictor take origin?

Answer 29

The middle constrictor takes origin from the hyoid bone and stylohyoid ligament and the inferior constrictor from the thyroid cartilage (the thyropharyngeus) and the cricoid cartilage (the cricopharyngeus)

Question 30

What lines the inner aspect of the constrictors?

Answer 30

The inner aspect of the constrictors are lined by the thick pharyngobasilar fascia which is attached to the pharyngeal tubercle, the auditory (Eustachian) tube and the medial pterygoid plate
The fascia bridges the gap between the superior constrictor and the base of the skull.

Question 31

Which nerves may be encountered on the back of the pharnx?

Answer 31

On the back of the pharynx you may encounter some fine nerves on the surface of the muscles which form the pharyngeal plexus formed by the vagus and glossopharyngeal nerves (cranial nerves X and IX).

Question 32

Where is the weakest part of the pharyngeal wall?

Answer 32

The weakest part of the pharyngeal wall is the lower part of the pharynx in the midline. This weakness lies between the diverging fibres of the thyro-pharyngeal part of the inferior constrictor and is known as Killian’s dehiscence

Question 33

Describe the cervical sympathetic chain?

Answer 33

Running up the neck posterior to the carotid sheath is the cervical sympathetic chain. It has three ganglia in the neck, a prominent superior cervical ganglion just below the skull, a smaller middle cervical ganglion and a larger inferior ganglion, which is often fused with the first thoracic ganglion to form the stellate ganglion. The Stellate ganglion is situated at a level between the neck of the first rib and the transverse process of the seventh cervical vertebrae

Question 34

What is the pathway of the vagus nerve in the neck?

Answer 34

• The vagus nerve has a sensory ganglia on it just before it enters the skull so it will get wider as you follow it upwards.
  
  • Towards the top of the neck the vagus has a large branch which passes down and medially, the superior laryngeal nerve.

Question 35

What is the pathway of the superior laryngeal nerve?

Answer 35

The superior laryngeal nerve passes over the carotid artery and disappears in the gap between the middle and inferior constrictor. It gives two branches, the internal laryngeal nerve which is a sensory nerve to the larynx above the vocal cords and the external laryngeal nerve which supplies the crico-thyroid muscle and the crico-pharyngeal part of the inferior constrictor

Question 36

Where would one find the carotid sinus?

Answer 36

At the origin of the internal carotid artery there is a swelling, the carotid sinus, which is innervated by the glossopharyngeal nerve

Question 37

Where is it most possible to see the trunk of the glossopharyngeal nerve?

Answer 37

the main trunk of the glossopharyngeal nerve as it leaves the skull through the jugular foramina.

Question 38

What innervation is provided by the glossopharyngeal nerve?

Answer 38

• The glossopharyngeal nerve (IX cranial nerve) gives sensory fibres to the posterior third of the tongue (both general sensation and taste) and to the oropharynx (general sensation). It also has a tympanic branch which supplies the middle ear and the Eustachian tube. It also supplies stylopharyngeus muscle.

Question 39

Where does the stylopharyngeus muscle take origin?

Answer 39

On the styloid process

Question 40

How can a pharyngeal pouch develop?

Answer 40

During swallowing the high pressure in the pharynx can cause the mucosa to bulge out through Killian’s dehiscence causing a pharyngeal pouch. Food then enters the pouch causing swelling and difficulty swallowing and decomposes causing very bad breath!!

Question 41

What is the role of the carotid sinus and what does applying pressure achieve?

Answer 41

The carotid sinus measures blood pressure. Pressure on the carotid sinus fools the sensory receptors into thinking the blood pressure is too high. The sensory signal is sent to the brain via the glossopharyngeal nerve and a return signal, through the vagus nerve, slows the heart rate. It can be used on patients with certain fast heart rates.

Question 42

What is the effect of a stroke on the glossopharyngeal nerve?

Answer 42

Some patients with a stroke (death of part of the brain) lose the sensation from the glossopharyngeal nerve. When they swallow they cannot detect any fluid passing down into the larynx and this will lead to fluid entering the lung and causing infection.

Question 43

Which structures lie immediately behind the pharyngeal wall?

Answer 43

A thin layer of loose areolar tissue and then the cervical vertebral bodies

Question 44

What is the role of the two cricothyroid muscles?

Answer 44

alter the length and tension of the vocal cords by tilting the thyroid cartilage forward on the cricoid cartilage

Question 45

What are the margins between the 3 structures of the pharynx?

Answer 45

· The lower margin of the soft palate marks the border between the naso-pharynx above and the oropharynx below.
· The aryepiglottic folds mark the laryngeal inlet and posterior to the laryngeal inlet is the hypopharynx (sometimes called the laryngo-pharynx).

Question 46

Describe the structures around the superior and inferior horns of the thyroid?

Answer 46

· When palpating the superior and inferior horns of the thyroid; the slit like gap lateral to them is the piriform fossa, malignant tumours arising in the piriform fossa may be ‘silent’ until locally advanced. This is because the tumour grows to fill the fossa before symptoms develop. Palpate the cricoid cartilage and the arytenoid cartilages. Note that the inferior horn of the thyroid cartilage forms a synovial joint with the cricoid cartilage.

Question 47

What is the laryngeal sinus?

Answer 47

Define the laryngeal inlet formed by the aryepiglottic fold and the smooth walled upper larynx. Identify two folds of mucosa separated by a deep cleft, the laryngeal sinus

Question 48

What is the structure of the vocal chords?

Answer 48

· The upper fold is the superior vestibular (or false vocal) fold, it covers a group of mucous glands.
· The lower fold is the ‘true’ vocal fold (or cord) and is formed by connective tissue and a muscle, the vocalis muscle.
· The vocalis muscle can be seen on some of the prosections where the mucosa has been stripped from the vocal folds. The space between the (right and left) vocal folds is the rima glottidis and it can be closed or varied in shape to produce different speech sounds.

Question 49

What is the innervation in the larynx?

Answer 49

· Externally, find the superior laryngeal nerve and trace it down until it enters the laryngopharynx above the thyroid cartilage. You may find a small branch, the external laryngeal nerve which passes to innervate the cricothyroid muscle. The superior laryngeal nerve innervates the mucosa of the larynx above the vocal folds, via the internal laryngeal nerve and is the afferent nerve of the cough reflex.
· the recurrent laryngeal nerves. These nerves innervate all the muscles of the larynx except the cricothyroid.

Question 50

Which structure stops liquid refluxing into the back of the nose during swallowing?

Answer 50

Soft Palate

Question 51

Which nerve carries sensation from the larynx below the vocal cords?

Answer 51

The recurrent laryngeal nerves

Question 52

Which nerve travels through the parotid gland?

Answer 52

The facial nerve

Question 53

Where does the pharynx begin and end?

Answer 53

It begins at the base of the skull, and ends at the inferior border of thecricoid cartilage(C6)

Question 54

What is Waldeyer’s Ring?

Answer 54

Waldeyer’s ringis the ring of lymphoid tissue in the naso- and oropharynx formed by the paired palatine tonsils, the adenoid tonsils and lingual tonsil.

Question 55

What are the two groups of pharyngeal muscles?

Answer 55

There are two main groups ofpharyngeal muscles;longitudinal and circular.
The muscles of the pharynx are mostly innervated by thevagus nerve– the only exception being thestylopharyngeus (glossopharyngeal nerve).

Question 56

Describe the superior pharyngeal constrictor?

Answer 56

the uppermost pharyngeal constrictor. It is located in the oropharynx.
· Originates from the pterygomandibular ligament, alveolar process of mandible and medial pterygoid plate and pterygoid hamulus of the sphenoid bone.
· Inserts posteriorly into to the pharyngeal tubercle of the occiput and themedian pharyngeal raphe.

Question 57

Describe the middle pharyngeal constrictor?

Answer 57

locatedin the laryngopharynx.
· Originates from the stylohyoid ligament and the horns of the hyoid bone.
Inserts posteriorly into the pharyngeal raphe

Question 58

Describe the inferior pharyngeal constrictor?

Answer 58

located in the laryngopharynx. It has two components:
· Superior component (thyropharyngeus) has oblique fibres that attach to the thyroid cartilage.
· Inferior component (cricopharyngeus) has horizontal fibres that attach to the cricoid cartilage.
All pharyngeal constrictors are innervated by thevagus nerve(CN X).

Question 59

Describe the longitudinal muscles of the pharynx?

Answer 59

They act to shorten and widen the pharynx, and elevate the larynx during swallowing.
· Stylopharyngeus– arises from the styloid process of the temporal bone, inserts into the pharynx.
· Unlike the other pharyngeal muscles, it is innervated by the glossopharyngeal nerve (CN IX).
· Palatopharyngeus–arises from hard palate of the oral cavity, inserts into the pharynx.
· Innervated by the vagus nerve (CN X).
· Salpingopharyngeus–arises from the Eustachian tube, inserts into the pharynx.
· Innervated by the vagus nerve (CN X).
· In addition to contributing to swallowing, it also opens the Eustachian tube to equalise the pressure in the middle ear.

Question 60

What is the arterial supply to the pharynx?

Answer 60

Arterial supply to the pharynx is via branches of theexternal carotidartery:
• Ascending pharyngeal artery
• Branches of the facial artery
• Branches of the lingual and maxillary arteries.
Venous drainage is achieved by thepharyngeal venous plexus, which drains into the internal jugular vein.

Question 61

What is the larynx and what is its purpose?

Answer 61

Thelarynx(voice box) is an organ located in the anterior neck. It is a component of the respiratory tract, and has several important functions, includingphonation, the cough reflex, and protection of the lower respiratory tract.

Question 62

What is the arterial supply to the larynx?

Answer 62

The arterial supply to the larynx is via the superior and inferior laryngeal arteries:
· Superior laryngeal artery– a branch of the superior thyroid artery (derived from the external carotid). It follows the internal branch of the superior laryngeal nerve into the larynx.
· Inferior laryngeal artery– a branch of the inferior thyroid artery (derived from the thyrocervical trunk). It follows the recurrent laryngeal nerve into the larynx.
Venous drainage is by thesuperior and inferior laryngeal veins. The superior laryngeal vein drains to the internal jugular vein via the superior thyroid, whereas the inferior laryngeal vein drains to the left brachiocephalic vein via the inferior thyroid vein.

Question 63

Describe the three unpaired cartilages of the larynx?

Answer 63

Thyroid Cartilage
The thyroid cartilage is a large, prominent structure which is easily visible in adult males. It is composed of two sheets (laminae), which join anteriorly to form thelaryngeal prominence(Adam’s apple).
The posterior border of each sheet projectsuperiorly and inferiorly to form thesuperiorandinferior horns(also known as cornu).The superior hornsare connected to the hyoid bone via the lateral thyrohyoid ligament, while the inferior horns articulate with the cricoid cartilage.

Cricoid Cartilage
The cricoid cartilage is a complete ring ofhyalinecartilage, consisting of abroad sheet posteriorly and a muchnarrowerarch anteriorly (said to resemble a signet ring in shape).
The cartilage completelyencircles the airway, marking the inferior border of the larynx at the level of C6. It articulates with the pairedarytenoid cartilagesposteriorly,as well as providing an attachment for the inferior horns of the thyroid cartilage.
The cricoid is the onlycompletecircle of cartilage in the larynx or trachea.This is of clinical relevance during emergency intubation – as pressure can be applied to the cricoid to occlude the oesophagus, and thus prevent regurgitation of gastric contents (known as cricoid pressure or Sellick’s manoeuvre).

Epiglottis
The epiglottis is aleaf shapedplate ofelastic cartilagewhich marks the entrance to the larynx. Its ‘stalk’ is attached to the back of the anterior aspect of the thyroid cartilage.During swallowing, the epiglottis flattens and moves posteriorly to close off the larynx and prevent aspiration.

Question 64

Describe the three paired cartilages of the larynx?

Answer 64

Arytenoid Cartilages
The arytenoid cartilages are pyramidal shaped structures that sit on thecricoidcartilage. They consist of an apex, base, three sides and two processes, and provides an attachment point for various key structures in the larynx:
• Apex– articulates with the corniculate cartilage.
• Base– articulates with the superior border of the cricoid cartilage.
• Vocal process– provides attachment for the vocal ligament.
• Muscular process– provides attachment for the posterior and lateral cricoarytenoid muscles.

Corniculate Cartilages
The corniculate cartilages are minor cartilaginousstructures. They articulate with the apices of the arytenoid cartilages.

Cuneiform Cartilages
The cuneiform cartilages are located within the aryepiglottic folds. They have no direct attachment, but act to strengthen the folds.

Question 65

What is the path of the oesophagus in the mediastinum?

Answer 65

The oesophagus runs alongside the descending aorta and thoracic vertebrae and passes through the diaphragm to enter the abdomen level with the 10th thoracic vertebra

Question 66

Where is the thoracic duct and what is its function?

Answer 66

posterior to the oesophagus. The thoracic duct drains all the lymph from the lower half of the body and bowel back into the blood stream. It drains into the confluence of the left subclavian vein and internal jugular vein in the left side of the neck

Question 67

Where are the intercostal vessels?

Answer 67

• As you look for the thoracic duct you will find arteries and veins running horizontally lying over the vertebral bodies, these are the intercostal vessels.

Question 68

What is the azygous system?

Answer 68

The azygos (venous) system is a collective term given to the H-shaped configuration of the azygos, hemiazygos, accessory hemiazygos veins and left superior intercostal vein. It is responsible for draining the thoracic wall and upper lumbar region via the lumbar veins and posterior intercostal veins
• The veins on the right side are called the azygous system and on the left the hemi-azygous system, there will be at least one connecting vein between them.

Question 69

What is the structure of the sympathetic chain in the thorax?

Answer 69

• Unlike the nerves which you have looked at so far the sympathetic chain is formed from a series of ganglia (neuron cell bodies) connected by nerve fibres (axons and dendrites). In the thorax there are twelve ganglia, one for each vertebra; in the neck there are three and in the abdomen and pelvis there is one per vertebra

Question 70

How are the splanchnic nerves formed and what does it innervate?

Answer 70

•Thesplanchnic nervesare paired visceralnerves(nervesthat contribute to the innervation of the internal organs), carrying fibers of the autonomicnervoussystem (visceral efferent fibers) as well as sensory fibers from the organs (visceral afferent fibers).

From the fifth to the twelfth thoracic ganglia there will be a nerves running forwards over the vertebral bodies these form 3 splanchnic nerves.
• The splanchnic nerves supply the bowel; the greater splanchnic nerve arises from T5 to T9 and supplies the foregut. The lesser splanchnic nerve arises from T10 and T11 and supplies the mid-gut and the least splanchnic nerve from T12 supplies the hind gut.

Question 71

How is a CT scan to be interpreted?

Answer 71

By convention when looking at a CT scan imagine you are standing at the foot of the patient’s bed and you are looking at them lying in the bed with their feet closest to you. This is the view that the scan is presented in. Right sided structures are on the left of the scan and left sided structures on the right. The back is at the bottom of the scan and the front of the body at the top

Question 72

Are the right and left main bronchi different? Is this clinically important?

Answer 72

The right main bronchus is more vertical and wider than the left. In patients who have inhaled a foreign body (eg. peanut) it more often travels into the right lung

Question 73

What is a transosophageal echo?

Answer 73

• Mitral valve disease is difficult to assess because the valve lies at the back of the heart. Just behind the heart is the oesophagus. An ultrasound probe can be placed in the oesophagus and provides exceptional images and measurements of the function of the mitral valve. This is called a trans-oesophageal echo (TOE).

Question 74

What pathology is caused by damage to the stellate ganglion?

Answer 74

All of the sympathetic nerve supply to the head and neck travels through the thoracic 1 ganglia of the sympathetic chain. Pathology damaging the (stellate) ganglia will cause loss of sympathetic innervation to the face and eye. The result is no facial sweating, a drooping eye lid, a constricted pupil and an eye slightly drawn in; this is Horner’s syndrome.

Question 75

What structures drain blood into the azygous system?

Answer 75

The superior intercostal veins

Question 76

Why is the left recurrent laryngeal nerve at risk from thoracic disease but not the right?

Answer 76

The left recurrent laryngeal nerve runs underneath and around the aorta therefore thoracic disease can place pressure on the nerve and causes damage or blockage. However, the right recurrent laryngeal nerve runs lateral to the heart and therefore remains away from risk

Question 77

Where do the sympathetic nerves attach to the central nervous system?

Answer 77

Sympathetic nerve fibers originatein the intermediolateral horns of the gray matter of the spinal cord between segments T-1 and L-3

Question 78

What is the arrangement of the sternocleidomastoid muscle?

Answer 78

sternocleidomastoid muscle it takes origin from the sternum (sterno) and the clavicle (cleido) and is inserted into the mastoid process just behind the ear (mastoid).
• The sternocleidomastoid muscle forms a triangle with the midline and lower part of the mandible, this is the anterior triangle of the neck

Question 79

Where may the accessory nerve be identified during an anterior triangle dissection?

Answer 79

Near the top of the dissection it may be possible to identify the branch of the accessory nerve (Cranial nerve XI) entering its deep surface

Question 80

What small muscles lie between the two sternocleidomastoid muscles and run vertically?

Answer 80

The infra-hyoid muscles

Question 81

What are the attachments of the sternohyoid muscle?

Answer 81

from Sternum to the hyoid bone

Question 82

Where would one find the omohyoid muscle and what are its attachments?

Answer 82

Lateral to the sternohyoid attachment to the hyoid find the superior belly of omohyoid, this muscle arises on the scapula (omo) and attaches onto the hyoid.

Question 83

What action must be taken to reveal the deeper sternothyroid and thyrohyoid muscles?

Answer 83

Fold sternohyoid upwards

Question 84

Where would one find branches of ansa cervicalis (nerve) in the anterior triangle?

Answer 84

passing to the strap muscles from behind the carotid sheath

Question 85

What must be reflected to reveal the thyroid gland?

Answer 85

reflect sternothyroid muscle superiorly

Question 86

What is the brief structure of the thyroid gland?

Answer 86

• The thyroid gland has two lobes sitting either side of the trachea with a narrow isthmus attaching the lobes across the front of the trachea.
• In some cadavers there may be a pyramidal lobe lying just above the left side of the isthmus, this is an embryological remnant.

Question 87

What would be found at the superior and inferior poles of the thyroid?

Answer 87

At the top of the superior pole find the superior thyroid artery and vein

At the lower pole look for the inferior thyroid artery and vein.

Question 88

What lies on the posterior surface of the thyroid gland?

Answer 88

Lying on the posterior surface of the thyroid gland are four glands; a pair of superior and a pair of inferior parathyroid glands

Question 89

What is the carotid sheath and where is it?

Answer 89

• Either side of the larynx and trachea is the carotid sheath; this is a tube of fascia containing the carotid artery, jugular vein and the vagus nerve (cranial nerve X).

Question 90

Where is the carotid sinus?

Answer 90

Just distal to the carotid bifurcation there is a swelling of the internal carotid artery, this is the carotid sinus and is an important baroreceptor which feeds into blood pressure control.

Question 91

Where is the carotid body?

Answer 91

Just in the ‘v’ of the bifurcation is the carotid body, a chemoreceptor which measures blood pH and feeds into the control of breathing

Question 92

Give three examples of the clinical relevance of the thyroid gland?

Answer 92

The thyroid gland is very closely applied to the trachea and lateral parts of the larynx; the larynx rises during swallowing. Lumps in the neck are common, lumps in the thyroid will elevate with swallowing but lumps in the lymph nodes will not.

The thyroid surrounds the trachea on three sides. Enlargement of the thyroid gland can compress the trachea.

The inferior pole of the thyroid is very close to the recurrent laryngeal nerves. The nerves are at risk of damage from thyroid pathology and surgery.

Question 93

What is the function of the extrinsic laryngeal muscles (sternothyroid, thyrohyoid etc?)

Answer 93

act to move the larynx superiorly and inferiorly

Question 94

Where can you create an emergency airway?

Answer 94

In the cricothyroid membrane

Question 95

Why does the thyroid have such a good blood supply?

Answer 95

It secretes hormones directly into the blood supply therefore is highly vascularised

Question 96

Which structure may be compressed by an enlarged thyroid gland?

Answer 96

The trachea

Question 97

What is the only complete cartilage ring around the airway?

Answer 97

Cricoid cartilage

Question 98

A patient may develop hypocalcaemia after thyroid surgery,why?

Answer 98

The parathyroid glands are damaged or are not functioning

Parathyroid disorders develop when parathyroid glands (normally four glands located near, or attached to, the back surface of the thyroid) release inappropriate levels of PTH​ hormone which controls calcium levels in the body. Hyperparathyroidism is a condition caused by higher than normal calcium levels (parathyroid glands producing too much PTH​) and can lead to negative effects like osteoporosis, kidney stones, chronic fatigue and others. The opposite problem, hypoparathyroidism, occurs when parathyroid glands do not produce enough PTH, leading to low blood calcium levels and adversely affecting muscles, nerves and other functions.

Question 99

What is the arterial supply and venous drainage of the thyroid gland?

Answer 99

Arterial Supply
The arterial supply to the thyroid gland is via two main arteries:
• Superior thyroid artery– arises as the first branch of the external carotid artery. It lies in close proximity to the external branch of the superior laryngeal nerve (innervates the larynx).
• Inferior thyroid artery– arises from the thyrocervical trunk (a branch of the subclavian artery). It lies in close proximity to the recurrent laryngeal nerve (innervates the larynx).
In a small proportion of people (around 10%) there is an additional artery present – thethyroid ima artery. It arises from the brachiocephalic trunk and supplies the anterior surface and isthmus of the thyroid gland.
Venous Drainage
Venous drainage is carried by the superior, middle, and inferior thyroid veins, which form avenous plexusaround the thyroid gland.
The superior and middle veins drain into the internal jugular vein and the inferior empties into the brachiocephalic vein.

Question 100

What are the boundaries of the carotid triangle?

Answer 100

· Superior– posterior belly of the digastric muscle.
· Lateral– medial border of the sternocleidomastoid muscle.
· Inferior– superior belly of the omohyoid muscle.
The main contents of the carotid triangle are thecommon carotid artery(which bifurcates within the carotid triangle into the external and internal carotid arteries), theinternal jugular vein, and thehypoglossalandvagus nerves

Question 101

What are the boundaries of the submental triangle?

Answer 101

· Inferiorly– hyoid bone.
· Medially– midline of the neck.
· Laterally– anterior belly of the digastric
The base of the submental triangle is formed by themylohyoid muscle, which runs from the mandible to the hyoid bone.

Question 102

What are the boundaries of the submandibular triangle?

Answer 102

· Superiorly– body of the mandible.
· Anteriorly– anterior belly of the digastric muscle.
· Posteriorly– posterior belly of the digastric muscle.

Question 103

What are the boundaries of the muscular triangle?

Answer 103

· Superiorly–hyoid bone.
· Medially– imaginary midline of the neck.
· Supero-laterally– superior belly of the omohyoid muscle.
· Infero-laterally– inferior portion of the sternocleidomastoid muscle.

Question 104

What is the path of the thoracic aorta and what are its branches?

Answer 104

The thoracic (descending) aorta is a continuation of thearch of the aorta, beginning at the lower edge of the T4 vertebra. It descends through the posterior mediastinum to the left of the vertebrae, becoming more medially located as it moves. At the inferior border of T12, thethoracic aorta becomes the abdominal aorta, and passes through theaortic hiatusof the diaphragm.
A number of branches arise from the thoracic aorta in the posterior mediastinum. These tend to arise in three vascular planes; unpaired branches to viscera extendanteriorly, paired branches to viscera extendlaterally, and paired segmental parietal branches extend mostlyposterolaterally.The major branches are:
· Posterior intercostal arteries– Paired parietal branches. Nine such pairs branch from the posterior aspect of the aorta, supplying the intercostal spaces (except the first two). Pass posteriorly and laterally, in parallel with the ribs (Supply 3rd-11th intercostal space)
· Bronchial arteries– Paired visceral branches, usually one or two. The left bronchial arteries always arise directly from the thoracic aorta, while those on the right usually branch indirectly from a right posterior intercostal artery. They go on to supply the tracheobronchial tree.
· Oesophageal arteries– Unpaired visceral branches, arising from the anterior aspect of the aorta. In most individuals there are two, but there can up to five. As the name suggests, these branches go on to supply the oesophagus.
· Superior phrenic arteries– Arise from the anterior aspect of the thoracic aorta at the aortic hiatus, varying in number. They supply the superior aspect of the diaphragm.

Question 105

What is the typical structure of a rib and give examples of typical ribs?

Answer 105

The typical rib consists of a head, neck and body:
Theheadis wedge shaped, and has two articular facets separated by a wedge of bone. One facet articulates with the numerically corresponding vertebrae, and the other articulates with the vertebrae above.
Theneckcontains no bonyprominences, but simply connects the head with the body. Where the neck meets the body there is a roughed tubercle, with a facet for articulation with the transverse process of the corresponding vertebrae.
The body, orshaftof the rib is flat and curved. The internal surface of the shaft has a groove for the neurovascular supply of the thorax, protecting the vessels and nerves from damage.

Ribs 3-9 are typical ribs

Question 106

Which ribs are atypical and why?

Answer 106

1, 2, 10, 11, and 12

Rib 1is shorter and wider than the other ribs. It only has one facet on its head for articulation with its corresponding vertebrae (there isn’t a thoracic vertebra above it). The superior surface is marked by two grooves, which make way for the subclavian vessels.

Rib 2is thinner and longer than rib 1, and has two articular facets on the head as normal. It has a roughened area on its upper surface, from which theserratus anteriormuscle originates.

Rib 10only has one facet – for articulation with its numerically corresponding vertebrae.

Ribs 11and12have no neck,and only contain one facet, which is for articulation with their corresponding vertebrae.

Question 107

What is the posterior articulation for the ribs?

Answer 107

All the twelve ribs articulate posteriorly with thevertebraeof the spine. Each rib forms two joints:
Costotransverse joint– Between the tubercle of the rib, and the transverse costal facet of the corresponding vertebrae.
Costovertebral joint– Between the head of the rib, superior costal facet of the corresponding vertebrae, and the inferior costal facet of the vertebrae above.

Question 108

What are the anterior attachment for the ribs?

Answer 108

The anterior attachment of the ribs vary:
• Ribs 1-7attach independently to the sternum.
• Ribs 8 – 10attach to the costal cartilages superior to them.
Ribs 11 and 12do not have an anterior attachment and end in the abdominal musculature. Because of this, they are sometimes called ‘floating ribs’.

Question 109

Where does the mammary gland lie and what is its structure?

Answer 109

within the subcutaneous layer, an accessory gland of the female reproductive system. The mammary glands are the key structures involved in lactation.

Question 110

Is the breast attached to the deep fascia over pectoralis major?

Answer 110

breast is not attached to the deep fascia over the pectoralis major muscle

Question 111

What is the structure and the surface markings of the breasts?

Answer 111

• The breast is located on the anterior thoracic wall. It extends horizontally from the lateral border of the sternum to themid-axillary line. Vertically, it spans between the 2nd and 6thcostal cartilages. It lies superficially to the pectoralis major and serratus anterior muscles.
• The breast can be considered to be composed of two regions:
• Circular body– largest and most prominent part of the breast.
• Axillary tail– smaller part,runs along the inferior lateral edge of the pectoralis major towards the axillary fossa.
• At the centre of the breast is thenipple, composed mostly of smooth muscle fibres. Surrounding the nipple is a pigmented area of skin termed theareolae. There are numeroussebaceous glandswithin the areolae – these enlarge during pregnancy, secreting an oily substance that acts as a protective lubricant for the nipple.
• The breast is composed of mammary glands surrounded by aconnective tissue stroma.

Question 112

What is the arterial supply of the breasts?

Answer 112

• Arterial supply to the medial aspect of the breast is via theinternal thoracic artery(also known as internal mammary artery) –a branch ofthe subclavian artery.
• The lateral part of the breast receives blood from four vessels:
• Lateral thoracicand thoracoacromial branches–originate from the axillary artery.
• Lateral mammarybranches– originate from theposterior intercostal arteries (derived from the aorta). They supply the lateral aspect of the breast in the 2nd3rdand 4thintercostal spaces.
• Mammary branch– originates from the anterior intercostal artery.
• The veins of the breast correspond with the arteries, draining into theaxillaryandinternal thoracic veins.

Question 113

What is the lymphatic drainage in the breasts?

Answer 113

• The lymphatic drainage of the breast is of great clinical importance due to its role in themetastasisof breast cancer cells.
• There are three groups of lymph nodes that receive lymph from breast tissue – the axillary nodes (75%), parasternal nodes (20%) and posterior intercostal nodes (5%).
• The skin of the breast also receives lymphatic drainage:
• Skin– drains to the axillary, inferior deep cervical and infraclavicular nodes.
Nipple and areola– drains to the subareolar lymphatic plexus.

Question 114

What is the innervation of the breast?

Answer 114

• The breast is innervated by theanteriorandlateral cutaneous branchesof the 4th to 6th intercostal nerves. These nerves contain both sensory and autonomic nerve fibres (the autonomic fibres regulate smooth muscle and blood vessel tone).
• It should be noted that these nerves do not control the production and secretion of milk. This is regulated by the hormones prolactin and oxytocin, which are secreted from thepituitary gland.

Question 115

What are the attachments and structure of pectoralis major?

Answer 115

origin of the pectoralis major muscle on the clavicle, costal cartilages and sternum and observe that it has a fan shape with the fibres converging to attach to the humerus.
• Lateral to the attachment of pectoralis major on the clavicle is the deltoid muscle, a large muscle covering the shoulder region.
The lower border of the pectoralis muscle forms the anterior axillary fold and inferior to it there is a ‘step’ down to a deeper layer of muscles.

Question 116

What structure runs in the groove between the deltoid muscle and pectoralis major?

Answer 116

The cephalic vein

Question 117

Name the two neurovascular bundles visible when pectoralis major is retracted?

Answer 117

the medial and lateral pectoral nerves

Question 118

What are the origins of pectoralis minor?

Answer 118

its origins on the 3rd, 4th and 5th ribs

Question 119

Describe the structure of serratus anterior?

Answer 119

• Follow the ribs laterally and you will notice that the ribs give rise to a muscle which passes backwards over the ribs and deep to the scapula; the serratus anterior muscle.
• Serratus anterior takes origin from the upper eight ribs

Question 120

What is the external oblique muscle?

Answer 120

Notice that the lower ribs (5th to 8th) also give rise to a muscle which runs down and medially to form the outer layer of the abdominal wall muscles, the external oblique muscle.

Question 121

How does contraction of pectoralis major assist in breathing?

Answer 121

The two pectoralis muscles form part of a ring of muscles which encircle the thoracic cage; the other muscles forming the ring are the scapula muscles. When the ring contracts the thoracic pressure rises to assist exhalation. This only occurs in disease and during exercise; normal exhalation is a passive process.

Question 122

Which bony structures lie subcutaneously in the anterior chest wall?

Answer 122

Clavicle and sternum

Question 123

What are the articulations of the clavicle?

Answer 123

The sternoclavicular joint, the acroclavicular joint

Question 124

What forms the anterior axillary fold?

Answer 124

The lowest and most lateral part of pectoralis major.

Question 125

What lies deep to pectoralis minor muscle?

Answer 125

Part of the axilla

Question 126

The majority of breast tissue is in the upper outer quadrant of the breast. Where does lymph from this part of the breast drain?

Answer 126

It drains into the lymph nodes in the axilla (the axillary lymph nodes)

Question 127

Which costal cartilage connects to the sternum at the sternal angle?

Answer 127

2nd rib costal cartilage

Question 128

Describe the appearance of the intercostal muscles?

Answer 128

• The gap between adjacent ribs is closed by two intercostal muscles, an external and internal intercostal. The external intercostal muscles are only attached to the ribs and form a sheet from the most anterior end of the ribs round to the articulation with the vertebra at the back.
  
  • Where the rib articulates with the costal cartilage the cartilages are connected by the anterior intercostal membrane.
  • Look at the direction of the muscle fibres of the external intercostal muscle (and membrane) and notice that they run in the same direction as the external oblique muscle of the abdominal wall.
  • Deep to the (very thin) anterior intercostal membrane you may be able to see muscle fibres running at 90 degrees to the external intercostal fibres; these are the internal intercostal muscles.
  • In one or two intercostal spaces, on one side, the anterior intercostal membrane has been detached from the upper border of the costal cartilages and this will allow you to fold the membrane and muscle up to expose the deeper internal intercostal muscle.
  Notice that the direction of the internal intercostal fibres run at ninety degrees to the external intercostal fibres.

Question 129

Where do the intercostal nerves run?

Answer 129

They run deep to the internal intercostal muscles in a groove just below the rib

Question 130

What is the hilum and what can be located there?

Answer 130

• In a normal thorax, the lung is ‘connected’ to the mediastinum at the hilum of the lung. This is where all structures pass into and out of the lung and is the only connection between the lung and the rest of the body.
  
  • Find one pulmonary artery, two pulmonary veins and a bronchus, and hilar lymph nodes(usually black with carbon deposits in cadavar)

Question 131

What is the difference between visceral and parietal pleura?

Answer 131

• All of the pleura lining the thoracic cavity is parietal pleura and is supplied by somatic nerves. Pain from these two layers feels different to the patient and is helpful is making a diagnosis
• Having removed the lungs, look for the interlobular (horizontal and oblique) fissures and lobes of left and right lungs.
The visceral pleura, which adheres closely to the surface of the lung extends into these fissures.

Question 132

what are the four pleurae and two recesses that may be identifed?

Answer 132

cervical, mediastinal, diaphragmatic and costal parietal pleurae, and also the costo-diaphragmatic and costo-mediastinal recesses

Question 133

What nerve supplies the diaphragm for both motor and sensory innervation?

Answer 133

the phrenic nerve for both motor and sensory function and arises from the 3rd, 4th and 5th cervical spinal nerves.

Question 134

What happens when the diaphragm contracts?

Answer 134

causes the dome of the diaphragm to descend decreasing the pressure in the thoracic cavity. This has two affects, (i) if the glottis is open air is drawn into the lungs and (ii) blood is drawn from the inferior vena cava into the right atrium.
• In the adult diaphragmatic descent is the main mechanism of breathing

Question 135

What breathing involves accessory muscles?

Answer 135

• Patients with extreme breathlessness may need to use many accessory muscles to generate much lower pressure within the thorax during inspiration and higher pressures during expiration. The main role of the intercostal muscles it to contract just enough so that they don’t get ‘sucked in’ by the negative pressure or ‘blown out’ by the positive pressure whilst allowing the thorax to be flexible. In some patients the pressures needed to support breathing overcome the intercostal muscles and we can observe ‘intercostal recession’; the intercostal spaces suck in during inspiration. It is an important sign of advance respiratory distress, particularly in the first six months of life.

Question 136

How does the internal mammary artery relate to coronary artery disease?

Answer 136

The left internal mammary artery (IMA) runs very close to the left anterior descending (LAD) coronary artery and grafting of the IMA to LAD is routine

Question 137

Which nerves carry sensation from the parietal and visceral pleura?

Answer 137

The parietal pleura lines the inside of the thoracic wall and is supplied by the same nerves as the tissue of the thoracic wall; the spinal nerves, thoracic 1 to thoracic 12. The visceral pleura covers the surface of the lung and is supplied by the same nerves as the lung; the vagus and sympathetic nerves

Question 138

What is a bronchopulmonary segment?

Answer 138

bronchopulmonary segmentis a portion oflungsupplied by its own bronchus and artery. Eachsegmentis functionally and anatomically discrete allowing a singlesegmentto be surgically resected without affecting its neighbouringsegments.

Question 139

What is the surface markings of the lowest extent of the lungs?

Answer 139

At the midclavicular line to lowest part of the lung lies at the tip of the 6th rib, at the midaxillary line the 8th rib and posteriorly the 10th rib

Question 140

What is intercostal recession?

Answer 140

When you have a partial blockage in your upper airway or the small airways in your lungs, air can’t flow freely and the pressure in this part of your body decreases. As a result, yourintercostalmuscles pull sharply inward. These movements are known asintercostalretractions, also calledintercostal recession.

Question 141

Describe the surface anatomy of the lungs?

Answer 141

• On both sides the oblique fissures start at the 4th rib at the back, travel deep to the 5th rib and end at the 6th costal cartilage at the front.
  
  • They separate the lower lobe from the upper lobe on the left and on the right separate the lower lobe from both the upper and middle lobe.
  • On the right there is a horizontal fissure, at the level of the 4th costal cartilage, which separates the upper lobe from the middle lobe of the right lung
  • The inferior extent of the lungs is at the 6th rib anteriorly, the 8th rib laterally and the 10th rib posteriorly.
  • The pleura extends below the lungs and forms the costo-diaphragmatic recesses.
  • The recess extends to the 8th rib anteriorly, the 10th laterally and the 12th posteriorly. This recess is needed for the lungs to expand into during deep inspiration.
  • Note that the lung extends above the clavicle into the base of the neck, and is at risk from stab wounds in the neck.
  • The oblique fissure of both lungs starts at the 4th rib at the back and follows the 5th rib to end at the anterior end of the 6th rib at the front. This means that if you want to listen to the upper lobe of the lung the stethoscope needs to be placed above this surface marking, and the lower lobe below this surface marking

Question 142

How many terminal bronchioles are there?

Answer 142

40 million

Question 143

How many alveoli are there?

Answer 143

around 300 million

Question 144

How many lobes, fissures, and bronchopulmonary segements does each lobe have?

Answer 144

Right: 3 lobes (upper, middle, lower), 2 fissures (horizontal and oblique), and 10 bronchopulmonary segments

Left: 2 lobes (upper and lower), 1 fissure (oblique), 9-10 bronchopulmonary segments

Question 145

What is the arterial supply and venous drainage for the lungs?

Answer 145

Bronchial artery (oxygenated blood) 
2x pulmonary arteries (deoxygenated blood)

Bronchial vein (drain to azygous vein deoxygenated blood) 
Pulmonary vein (drain into left atrium oxygenated blood)

Question 146

What are the two movements of breathing?

Answer 146

pump handle movement and bucket handle movement

Question 147

Describe the mechanism of breathing?

Answer 147

The inferior of the thoracic cage is closed with a large domed sheet of muscle called the diaphragm. The peripheral fibres of the diaphragm are attached to the lower ribs, costal margin and the xiphisternum. When these fibres contract the diaphragm will move down due to muscle contraction, creating a negative pressure in the thorax and air will be drawn into the lungs. Incidentally blood will also be drawn into the thorax to aid venous return to the right atrium. Breathing due to action of the diaphragm is called abdominal breathing because it relies on displacement of the abdomen. During quiet breathing the majority of the change in thoracic volume is due to the action of the diaphragm. However, during exercise and pregnancy when increased gas exchange is needed or there is a lack of diaphragmatic movement other mechanisms come into play. This is where movement of the ribs becomes important. Action of the intercostal muscles will pull the ribs closer together, as the first rib is relatively fixed the result is that the other ribs get pulled upwards increasing the lateral and anterior-posterior diameters of the chest. This is called thoracic breathing. This can be further enhanced by using powerful neck and shoulder muscles to pull up on the ribs, patients with severe asthma attacks often use these “Accessory muscles of breathing”

Question 148

What are the divisions of the sternum?

Answer 148

Manubrium, body, and xiphisternum

Question 149

Describe the manubrium sternum?

Answer 149

Manubrium
Themanubriumis the most superior portion of the sternum. It istrapezoidin shape.
The superior aspect of the manubrium is concave, producing a depression known as thejugular notch– this is visible underneath the skin. Either side of the jugular notch, there is a large fossa lined with cartilage. These fossae articulate with the medial ends of the clavicles, forming thesternoclavicular joints.
On the lateral edges of the manubrium, there is afacet(cartilage lined depression in the bone),for articulation with the costal cartilage of the 1st rib, and ademifacet(half-facet) for articulation with part of the costal cartilage of the 2nd rib.
Inferiorly, the manubrium articulates with the body of the sternum, forming thesternal angle. This can be felt as a transverse ridge of bone on the anterior aspect of the sternum. The sternal angle is commonly used as an aid to count ribs, as it marks the level of the 2nd costal cartilage.

Question 150

Describe the body of the sternum?

Answer 150

Body
Thebodyis flat and elongated – the largest part of the sternum. It articulates with the manubrium superiorly (manubriosternal joint) and the xiphoid process inferiorly (xiphisternal joint).
The lateral edges of the body are marked by numerousarticular facets(cartilage lined depressions in the bone). These articular facets articulate with the costal cartilages of ribs 3-6. There are smaller facets for articulation with parts of the second and seventh ribs – known as demifacets.

Question 151

Describe the xiphoid process/ xiphisternum?

Answer 151

Xiphoid Process
Thexiphoid processis the most inferior and smallest part of the sternum. It is variable in shape and size, with its tip located at the level of the T10 vertebrae. The xiphoid process is largely cartilaginous in structure, and completely ossifies late in life – around the age of 40.
In some individuals, the xiphoid process articulates with part of the costal cartilage of the seventh rib.

Question 152

What structures pierce the diaphragm at the caval hiatus (T8)?

Answer 152

Inferior Vena Cava and terminal branches of right phrenic nerve

Question 153

What structures pierce the diaphragm at the oesophageal hiatus (T10)?

Answer 153

Oesophagus, right and left vagus nerves, oesophageal branches of left gastric artery/ vein

Question 154

What structures pierce the diaphragm at the aortic hiatus (T12)?

Answer 154

Aorta, Thoracic Duct, and Azygous Vein

Question 155

What is the structure of the thymus gland?

Answer 155

The thymus gland has an asymmetrical flat shape, with a lobular structure. The lobules are comprised of a series of follicles, which have a medullary and cortical component:
• Cortical portion– Located peripherally within each follicle. It is largelycomposed of lymphocytes, supported epithelial reticular cells.
• Medullary portion– Located centrally within each follicle. It contains fewer lymphocytes than the cortex, and an increased number of epithelial cells.Hassall’s corpuscles are also present – these are concentric arrangements ofepithelial reticular cells. Their function is unclear.
The gland is mainly located within the thoracicsuperior mediastinum,posterior to the manubrium of the sternum. However, in some individuals, it can extend superiorly into the neck (reaching thethyroid gland), and inferiorly into theanterior mediastinum(lying in front of the fibrouspericardium).

The arterial supply to the thymus gland is via the anterior intercostal arteries and small branches from theinternal thoracic arteries. Venous blood drains into theleft brachiocephalicand internal thoracic veins.

Question 156

What is the structure of the lungs?

Answer 156

The lungs are roughlyconeshaped, with an apex, base, three surfaces and three borders. The left lung is slightly smaller than the right – this is due to the presence of the heart.
Each lung consists of:
• Apex– The blunt superior end of the lung. It projects upwards, above the level of the 1st rib and into the floor of the neck.
• Base– The inferior surface of the lung, which sits on the diaphragm.
• Lobes(two or three) – These are separated by fissures within the lung.
• Surfaces(three) – These correspond to the area of the thorax that they face. They are named costal, mediastinal and diaphragmatic.
• Borders(three) – The edges of the lungs, named the anterior, inferior and posterior borders.

Question 157

What is the lung root?

Answer 157

The lungrootis a collection of structures that suspends the lung from the mediastinum. Each root contains a bronchus, pulmonary artery, two pulmonary veins, bronchial vessels, pulmonaryplexus of nerves and lymphatic vessels.

Question 158

What is the innervation of the lungs?

Answer 158

The nerves of the lungs are derived from thepulmonary plexuses. Theyfeature sympathetic, parasympathetic and visceral afferent fibres:
Parasympathetic– derived from the vagus nerve. They stimulate secretion from the bronchial glands, contraction of the bronchial smooth muscle, and vasodilation of the pulmonary vessels.
Sympathetic– derived from the sympathetic trunks. They stimulate relaxation of the bronchial smooth muscle, and vasoconstriction of the pulmonary vessels.
Visceral afferent– conduct pain impulses to the sensory ganglion of the vagus nerve.

Question 159

What is the lymphatic drainage in the lungs?

Answer 159

The lymphatic vessels of the lung arise from two lymphatic plexuses:
Superficial (subpleural)– drains the lung parenchyma.
Deep– drains the structures of the lung root.
Both these plexuses empty into thetrachebronchial nodes–located around the bifurcation of the trachea and the main bronchi. From here, lymph passes into the right and left bronchomediastinal trunks.

Question 160

What is the structure of the trachea?

Answer 160

The trachea, like all of the larger respiratory airways, is held open by cartilage – here inC-shapedrings. The free ends of these rings are supported by thetrachealis muscle.
The trachea and bronchi are lined by ciliated pseudostratified columnar epithelium, interspersed bygoblet cells, which produce mucus. The combination of sweeping movements by the cilia and mucus from the goblet cells forms the functionalmucociliary escalator. This acts to trap inhaled particles and pathogens, moving them up out of the airways to be swallowed and destroyed.
At the bifurcation of the primary bronchi, a ridge of cartilage called thecarinaruns anteroposteriorly between theopenings of the two bronchi.

The trachea receives sensory innervation from therecurrent laryngeal nerve.
Arterial supply comes from the tracheal branches of theinferior thyroid artery, while venous drainage is viathe brachiocephalic, azygos and accessory hemiazygos veins.

At the level of the sternal angle, the trachea bifurcates into the right and left main bronchi.

Question 161

What is the innervation of the bronchi?

Answer 161

The bronchi derive innervation from pulmonary branches of thevagus nerve(CN X)

Question 162

What is the origin, insertion, innervation, and primary action of pectoralis major?

Answer 162

Origin:
• Medial clavicle
• Sternum
• Superior 6 costal cartilages and aponeurosis of external oblique

Insertion: Lateral lip of bicipital groove of Humerus

Innervation: Medial and Lateral Pectoral Nerves

Primary Action(s):
Flexion, Adduction & Internal Rotation of the Humerus
Also assists with inspiration when humerus is fixed.

Question 163

What is the origin, insertion, innervation, and primary action of pectoralis minor?

Answer 163

Origin: Anterior aspect of ribs 3, 4 & 5

Insertion: Coracoid Process of Scapula

Innervation: Medial Pectoral Nerve
Primary Action(s): Stabilise the Scapula against the thoracic wall Also assists with inspiration when scapula is fixed

Question 164

What is the origin, insertion, innervation, and primary action of Serratus Anterior?

Answer 164

Origin: Lateral aspect of ribs 1 to 8, 9 or 10
Insertion: Anterior surface of medial border of Scapula
Innervation: Long Thoracic Nerve
Primary Action(s): Protraction of the Scapula, Also assists with inspiration when scapula is fixed.

Question 165

What is origin and course of the internal mammary (thoracic) artery and what does it supply?

Answer 165

Origin: Subclavian Artery
Course: Runs inferiorly from its origin, immediately deep to the anterior thoracic wall, just lateral to the sternum (bilaterally).
Supplies: Mediastinum, pericardium, anterior ribs and intercostal muscles. Continues into the abdomen as the Superior Epigastric Artery.

Question 166

What structures are in the lung hila and what is the orientation?

Answer 166

Structures (8): Main Bronchus, Pulmonary Artery, Pulmonary Veins (x2), Bronchial Artery,
pulmonary branches of the Vagus Nerve, Sympathetic nerves and Lymph vessels.
Orientation: RALS: Right Anterior Left Superior: in the right hilum, the pulmonary artery is anterior to the bronchus; in the left hilum, it is superior.

Question 167

What is the lung pleura innervation?

Answer 167

Parietal: • Intercostal Nerves
• Phrenic Nerve (for the diaphragmatic surface of the pleura)
Visceral: Autonomic fibres only, via branches of the Vagus Nerve (parasympathetic) and Sympathetic nerves

Question 168

What are the surface markings for the lungs and the pleural cavity?

Answer 168

Due to the shape of the lungs and pleural cavities, they extend further down at
the back than they do at the front.
• Lung anteriorly: 6th rib, laterally: 8th rib, posteriorly: 10th rib.
• Cavity anteriorly: 8th rib, laterally: 10th rib, posteriorly: 12th rib.

Question 169

Describe the intercostal neurovascular bundles?

Answer 169

The individual intercostal vessels and nerves are oriented from superior to inferior in the order VAN (vein, artery, nerve).
• They are located immediately inferior to each rib.
• This is important to know when inserting a chest drain, as it must be inserted
immediately superior to a rib to avoid damaging the neurovascular bundle.

Question 170

What is the origin, course, function and clinical notes for the recurrent laryngeal nerve?

Answer 170

Origin: Branch of the Vagus nerve.
Course:
• LEFT: loops underneath the Arch of the Aorta, then comes back up to
reach the larynx.
• RIGHT: only loops underneath the Right Subclavian Artery (so doesn’t
travel as deep into the thorax).
• Runs very close to the Inferior Thyroid Artery.

Function:
• Sensation to the larynx below the vocal cords.
• Motor to all internal laryngeal muscles except Cricothyroid.

Clinical Notes:
• Due to its long course, it is vulnerable to damage from lung/neck cancers and during thoracic or thyroid surgery.
• If damaged, this will cause paralysis of half of the larynx, giving the patient a hoarse voice.

Question 171

What is the origin, course, function and clinical notes for the sympathetic chain?

Answer 171

Origin: Spinal nerves of T1 to L2.

Course:
• Located just lateral to the vertebral column on the posterior thoracic wall.
• It runs the entire length of the vertebral column on both sides, all the way
up into the skull and down to the coccyx.
• Along its length are collections of sympathetic nerve cell bodies, called
‘ganglia’.

Function: Distribute sympathetic nerve fibres to the entire body.

Clinical Notes:
• As there are no sympathetic fibres originating from the cervical spinal nerves, if the sympathetic chain is damaged as it ascends into the neck, then sympathetic supply to the head is lost. Clinically, this presents as
‘Horner’s Syndrome’ on the affected side: constricted pupil, droopy eyelid, dry face.
• The lower cervical ganglion (C7) and the upper thoracic ganglion (T1) are so close together that they often fuse into one larger ganglion called the
‘Stellate Ganglion’.

Question 172

What are the splanchnic nerves?

Answer 172

Description: Branches of the Sympathetic Chain at specific levels that carry sympathetic
fibres to distant organs.

‘Greater’: From T5-T9, supplies the foregut with sympathetic supply and pain fibres.

‘Lesser’: From T10-T11, supplies the midgut with sympathetic supply and pain fibres.

‘Least’: From T12, supplies the hindgut with sympathetic supply and pain fibres

Question 173

What is the origin, course, function, and clinical notes for the thoracic duct?

Answer 173

Origin: Confluence of lymph vessels called the ‘Cisterna Chyli’ at around T12 level.
• Note, there is only one thoracic duct.

Course:
• Travels upwards through the diaphragm with the aorta, often located on
the anterior surface of descending aorta.
• Terminates and deposits the lymph at the junction of the LEFT internal jugular vein and LEFT subclavian vein, where they become the left brachiocephalic vein.

Function: Transmits lymph fluid from the lower part of the body and deposits it into the
bloodstream.

Clinical Notes: If damaged, lymph leaks into the thorax and this is called a ‘Chylothorax’.

Question 174

Describe the superficial neck muscles?

Answer 174

Platysma: • Thin sheet-like muscle that encapsulates the anterior neck.
• Just deep to the skin.

Sternocleidomastoid:
• Long muscle on both sides of the neck, allows turning and nodding of the head.
• Innervated by the Accessory Nerve (cranial nerve XI).
• Divides the neck into the ‘Anterior’ and ‘Posterior Triangles’.

‘Strap Muscles’
• Superficial layer: Sternohyoid (medial) & Omohyoid (lateral).
• Deeper layer: Sternothyroid (inferior) & Thyrohyoid (superior).
• Motor innervation to these muscles (except Thyrohyoid) is via the ‘Ansa
Cervicalis’ (a loop of nerves originating from C1 to C3).

Question 175

What is the location, function, blood supply and drainage, and clinical notes for the thyroid gland?

Answer 175

Location: H-shaped gland, with the central ‘isthmus’ located just below the cricoidcartilage of the larynx.

Function: Produce thyroid hormones (Triiodothyronine, T3, and Thyroxine, T4).

Blood Supply & Drainage:
• Arteries:
• Superior Thyroid Artery (branch of the External Carotid).
• Inferior Thyroid Artery (branch of the Thyrocervical Trunk, which is a branch of the Subclavian Artery).
• Veins:
• Superior Thyroid Vein (drains into Internal Jugular).
• Middle Thyroid Vein (drains into Internal Jugular).
• Inferior Thyroid Vein (drains directly into Brachiocephalic Vein).

Clinical Notes:
• Thyroid hormones require iodine for their production, but the blood concentration of iodine is very low. Therefore, the thyroid gland needs a very good blood supply to deliver the required quantity of iodine for
hormone production.
• The Recurrent Laryngeal Nerve is very close to the Inferior Thyroid Artery so can be mistakenly damaged during a thyroidectomy.
• The 4 Parathyroid Glands are found on the back of each pole of the thyroid gland. They may be inadvertently removed during a thyroidectomy due to
their position. The hormone they produce (Parathyroid Hormone, or ‘PTH’) is responsible for increasing blood calcium levels. Without the Parathyroid Glands, patients may develop hypocalcaemia

Question 176

Describe the pharyngeal constrictors?

Answer 176

Function:
• Form the posterior wall of the pharynx and propel food down into the oesophagus.
• Overlap and fit into each other.
• All innervated by the Pharyngeal Plexus of the Vagus nerve.

Superior: Forms the posterior wall of the nasopharynx.

Middle: Forms the posterior wall of the oropharynx.

Inferior:• Forms the posterior wall of the laryngopharynx.
• Formed by two distinct muscle parts: Thyropharyngeus and Cricopharyngeus, originating from the thyroid and cricoid cartilages respectively.

Clinical Notes:
• Between the two parts of the inferior constrictor, there is an inherent weakness in the wall of the pharynx known as ‘Killian’s Dehiscence’. If there is excess pressure in the laryngopharynx, food can get pushed out through this weakness and form a ‘pharyngeal pouch’. This can lead to impaired swallowing, regurgitation of food and infection.

Question 177

What is the hyoid bone?

Answer 177

• Horseshoe-shaped bone at the top of the larynx.

Question 178

What is the thyroid cartilage?

Answer 178

Main, large cartilage of the larynx, below the Hyoid bone.

• Anterior prominence commonly known as the ‘Adam’s Apple’.

Question 179

What is the cricoid cartilage?

Answer 179

Signet-ring shaped cartilage below the thyroid cartilage.
• Short at the front, tall at the back.
• Only complete cartilaginous ring of the airway

Question 180

What is the epiglottis?

Answer 180

• Leaf-shaped cartilage that can ‘fold’ down to cover the glottis when swallowing.

Question 181

What are the arytenoid cartilages?

Answer 181

• Pyramid-shaped cartilages sitting atop the back of the Cricoid cartilage.
• Attached to the vocal cords. Responsible for opening and closing the vocal
cords when moved by intrinsic laryngeal muscles.

Question 182

What are the Aryepiglottic Folds?

Answer 182

Sheets of membrane that attach the lateral aspects of the epiglottis to the Arytenoid cartilages.

Question 183

What is the vallecula?

Answer 183

Anterior space at the base of the epiglottis where it meets the thyroid cartilage.
• Food can get stuck here, causing an uncomfortable sensation

Question 184

What are the piriform recesses?

Answer 184

Lateral spaces at the sides of the epiglottis, between the aryepiglottic folds and the thyroid cartilage.
• Food can get stuck here, causing an uncomfortable sensation

Question 185

What is the cricothyorid membrane?

Answer 185

Membrane at the front of the larynx between the thyroid cartilage and cricoid cartilage.
• Punctured to establish an emergency airway; this is called an ‘Emergency Cricothyroidotomy’

Question 186

What is the cricothyorid muscle?

Answer 186

On the outside of the front of the larynx.
• Pulls the thyroid cartilage down and forward on the cricoid cartilage to
tense the vocal cords, increasing voice pitch.
• Only muscle innervated by the Superior Laryngeal Nerve (external branch)

Question 187

What is the posterior cricoarytenoid muscle?

Answer 187

On the back of the larynx.
• Opens (abducts) the vocal cords.
• Only muscle that opens the vocal cords.

Question 188

What are the Transverse and

Oblique InterArytenoids muscles?

Answer 188

• On the back of the larynx.

* Closes (adducts) the vocal cords.

Question 189

What is the Lateral

Cricoarytenoid muscle?

Answer 189

On the inside at the sides of the larynx.

• Closes (adducts) the vocal cords.

Question 190

Describe the innervation of the larynx?

Answer 190

Sensation: • Above the vocal cords: Superior Laryngeal Nerve (Internal Branch).
• Below the vocal cords: Recurrent Laryngeal Nerve.

Motor: • Cricothyroid muscle: Superior Laryngeal Nerve (External Branch)
• All other intrinsic laryngeal muscles: Recurrent Laryngeal Nerve.

Note: all nerves that supply the larynx are branches of the Vagus nerve.

Question 191

Describe the salivary glands?

Answer 191

Parotid:
• The largest salivary gland. Located just in front of the ear.
• Parotid Duct opens in the oral cavity on the buccal side (cheek-side) next
to the upper 2nd premolar.
• Facial nerve passes through the Parotid Gland, may be damaged in Parotid
cancer or surgery.

Submandibular:
• Grape-sized. Located below the mandible bilaterally.
• Submandibular Duct opens in the oral cavity on both sides of the lingual
frenulum below the tongue.

Sublingual:
• The smallest salivary gland. Located underneath the floor of the mouth,
below the front of the tongue.
• Sublingual Ducts opens in the oral cavity in the floor of the mouth below the tongue.

Question 192

What are the palatine arches?

Answer 192

Also knows as ‘Folds’, they are the 2 thin sheets of muscle that look like 2
sets of curtains as the back of the oral cavity, separating it from the
oropharynx.
• Palatoglossus is the most anterior arch.
• Palatopharyngeus is the most posterior arch.
• The palatine tonsils are located between the two arches.

Question 193

What is the lingual frenulum?

Answer 193

Fold of mucosa on the underside of the tongue at the front that tethers the
tongue to the floor of the oral cavity
• The submandibular salivary ducts drain into the mouth on both sides of the
base of the lingual frenulum.

Question 194

What are the paranasal sinuses?

Answer 194

Cavities within the anterior skull with several functions: to lighten the skull,
humidify inhaled air, increase vocal resonance and act as ‘crumple-zones’
in facial trauma.
• Frontal Sinuses: located above the orbits superomedially.
• Maxillary Sinuses: located inferior to the orbits, lateral to the nasal cavity.
• Ethmoid Sinuses: collection of numerous smaller cavities located deep in
the face, medial to the orbits and superior to the posterior nasal cavity.
• Sphenoid Sinuses: located behind the ethmoid sinuses, underneath the
pituitary gland

Question 195

What is the cribriform plate?

Answer 195

Sieve-like sheet of bone at the very top of the nasal cavity.
• Fibres of the Olfactory Nerve (responsible for the sense of smell) pass
through this bone

Question 196

What are nasal conchae?

Answer 196

Also known as ‘Turbinates’, they are 3 curled shelves of bone protruding
from the lateral walls of the nasal cavity.
• They are covered in mucosa and their purpose is to increase surface area
in the nasal cavity to warm and humidify inhaled air.
• They anatomically divide the nasal cavity into 4 spaces

Question 197

What is the sphenoethmoidal recess?

Answer 197

• Space above the superior concha, but below the base of the skull.
• The sphenoid sinus and posterior ethmoid sinus drain into this space.

Question 198

What is the superior meatus?

Answer 198

Space below the superior concha, but above the middle concha.
• Some sources state that the posterior ethmoid sinus drains into this space

Question 199

What is the middle meatus?

Answer 199

Space below the middle concha, but above the inferior concha.
• The frontal, maxillary and anterior & middle ethmoid sinuses drain into this
space.

Question 200

What is the inferior meatus?

Answer 200

Space below the inferior concha, above the floor of the nasal cavity.
• The Nasolacrimal duct (carrying tears) drains into this space.

Question 201

What is the Eustachian Tube?

Answer 201

Tube between the nasal cavity and middle ear cavity.
• Allows air pressure to equalise on either side of the tympanic membrane
(eardrum).
• Can get blocked by nasal oedema or mucus (e.g. in respiratory tract
infections like the common cold).
• Drains into the posterior aspect of the nasal cavity, roughly in line with the
inferior meatus

Question 202

What is the infra-orbital nerve?

Answer 202

• Nerve that supplies sensation to the skin over the cheek.

* Runs in a groove in the superolateral wall of the maxillary sinus.