Respiratory Anatomy Flashcards
(202 cards)
1
Q
What is the anatomical position of the tongue?
A
The tongue fills the floor of the mouth and is attached to the posterior of the ramus of the mandible and hyoid bone
2
Q
What are the boundaries of the oral cavity?
A
It is bound anteriorly by the lips, laterally by the cheeks, superiorly by the palate and inferiorly by the tongue.
3
Q
Where would one find the palatine tonsil?
A
you should be able to identify the tonsil on the lateral wall of the oropharynx beyond the posterior third of the tongue.
4
Q
What are the positions of the palatoglossal and palatopharyngeal folds?
A
· 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.
5
Q
Which constrictor of the pharynx does the tonsil sit on?
A
The super constrictor
6
Q
What is the tonsil?
A
· The tonsil is a consolidation of lymphoid tissue which samples organisms which may try to enter the body via the mouth or nose.
7
Q
What is the function of the adenoids and where are they?
A
They perform a similar function to the tonsil and they lie posterior pharyngeal wall just above the level of the soft palate
8
Q
Describe the palate?
A
· 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
9
Q
What three structures all join the nasal cavity?
A
The bony sinuses, middle ear and tear duct all join the nasal cavity.
10
Q
Where would one find the openings of the Eustachian tubes?
A
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
11
Q
What is the nasal septum covered with?
A
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
12
Q
What is the bony septum formed from?
A
The bony septum is mainly formed by the vomer and vertical plate of the ethmoid bones.
13
Q
What lies at the most superior part of the nasal cavity?
A
At the most superior part of the cavity is the spheno-ethmoidal recess which is adjacent to the cribriform plate
14
Q
What structure passes through the spheno-ethmoidal recess?
A
Fibres of the first cranial nerve, the olfactory (smell) nerve, pass from the spheno-ethmoidal recess into the cranium and to the brain.
15
Q
Which nerve carries general sensation from the nasal cavity?
A
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
16
Q
What duct drains into the inferior meatus?
A
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
17
Q
What structures exist in the middle meatus?
A
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.
18
Q
What makes the maxillary sinus unique?
A
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
19
Q
What drains into the superior meatus?
A
draining into this are the posterior ethmoid sinuses
20
Q
Where does the sphenoid sinus drain?
A
The sphenoid sinus drains directly into the spheno-ethmoidal recess
21
Q
What is the connection between dental infection and the maxillary sinus?
A
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.
22
Q
Why can maxillary sinus disease cause pain in the cheek?
A
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.
23
Q
Which nerve runs posteriorly to the maxillary sinus?
A
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
24
Q
Why do children born with cleft palate have common ear infections?
A
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.
25
What is a grommet and what is it used to treat?
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.
26
What is the function of the Eustachian Tube?
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.
27
What are the three structures of the pharynx?
Nasopharynx, oropharnyx, laryngealpharnx/hypopharnx
28
Where does the superior constrictor take origin?
The superior constrictor takes origin from the medial pterygoid plate and the pterygomandibular raphe, which extends from the medial pterygoid plate to the mandible
29
Where does the middle constrictor take origin?
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)
30
What lines the inner aspect of the constrictors?
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.
31
Which nerves may be encountered on the back of the pharnx?
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).
32
Where is the weakest part of the pharyngeal wall?
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
33
Describe the cervical sympathetic chain?
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
34
What is the pathway of the vagus nerve in the neck?
* 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.
35
What is the pathway of the superior laryngeal nerve?
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
36
Where would one find the carotid sinus?
At the origin of the internal carotid artery there is a swelling, the carotid sinus, which is innervated by the glossopharyngeal nerve
37
Where is it most possible to see the trunk of the glossopharyngeal nerve?
the main trunk of the glossopharyngeal nerve as it leaves the skull through the jugular foramina.
38
What innervation is provided by the glossopharyngeal nerve?
• 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.
39
Where does the stylopharyngeus muscle take origin?
On the styloid process
40
How can a pharyngeal pouch develop?
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!!
41
What is the role of the carotid sinus and what does applying pressure achieve?
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.
42
What is the effect of a stroke on the glossopharyngeal nerve?
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.
43
Which structures lie immediately behind the pharyngeal wall?
A thin layer of loose areolar tissue and then the cervical vertebral bodies
44
What is the role of the two cricothyroid muscles?
alter the length and tension of the vocal cords by tilting the thyroid cartilage forward on the cricoid cartilage
45
What are the margins between the 3 structures of the pharynx?
· 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).
46
Describe the structures around the superior and inferior horns of the thyroid?
· 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.
47
What is the laryngeal sinus?
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
48
What is the structure of the vocal chords?
· 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.
49
What is the innervation in the larynx?
· 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.
50
Which structure stops liquid refluxing into the back of the nose during swallowing?
Soft Palate
51
Which nerve carries sensation from the larynx below the vocal cords?
The recurrent laryngeal nerves
52
Which nerve travels through the parotid gland?
The facial nerve
53
Where does the pharynx begin and end?
It begins at the base of the skull, and ends at the inferior border of the cricoid cartilage (C6)
54
What is Waldeyer's Ring?
Waldeyer’s ring is the ring of lymphoid tissue in the naso- and oropharynx formed by the paired palatine tonsils, the adenoid tonsils and lingual tonsil.
55
What are the two groups of pharyngeal muscles?
There are two main groups of pharyngeal muscles; longitudinal and circular.
The muscles of the pharynx are mostly innervated by the vagus nerve – the only exception being the stylopharyngeus (glossopharyngeal nerve).
56
Describe the superior pharyngeal constrictor?
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 the median pharyngeal raphe.
57
Describe the middle pharyngeal constrictor?
located in the laryngopharynx.
· Originates from the stylohyoid ligament and the horns of the hyoid bone.
Inserts posteriorly into the pharyngeal raphe
58
Describe the inferior pharyngeal constrictor?
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 the vagus nerve (CN X).
59
Describe the longitudinal muscles of the pharynx?
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.
60
What is the arterial supply to the pharynx?
Arterial supply to the pharynx is via branches of the external carotid artery:
• Ascending pharyngeal artery
• Branches of the facial artery
• Branches of the lingual and maxillary arteries.
Venous drainage is achieved by the pharyngeal venous plexus, which drains into the internal jugular vein.
61
What is the larynx and what is its purpose?
The larynx (voice box) is an organ located in the anterior neck. It is a component of the respiratory tract, and has several important functions, including phonation, the cough reflex, and protection of the lower respiratory tract.
62
What is the arterial supply to the larynx?
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 the superior 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.
63
Describe the three unpaired cartilages of the larynx?
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 the laryngeal prominence (Adam’s apple).
The posterior border of each sheet project superiorly and inferiorly to form the superior and inferior horns (also known as cornu). The superior horns are 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 of hyaline cartilage, consisting of a broad sheet posteriorly and a much narrower arch anteriorly (said to resemble a signet ring in shape).
The cartilage completely encircles the airway, marking the inferior border of the larynx at the level of C6. It articulates with the paired arytenoid cartilages posteriorly, as well as providing an attachment for the inferior horns of the thyroid cartilage.
The cricoid is the only complete circle 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 a leaf shaped plate of elastic cartilage which 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.
64
Describe the three paired cartilages of the larynx?
Arytenoid Cartilages
The arytenoid cartilages are pyramidal shaped structures that sit on the cricoid cartilage. 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 cartilaginous structures. 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.
65
What is the path of the oesophagus in the mediastinum?
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
66
Where is the thoracic duct and what is its function?
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
67
Where are the intercostal vessels?
• 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.
68
What is the azygous system?
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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.
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69
What is the structure of the sympathetic chain in the thorax?
• 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
70
How are the splanchnic nerves formed and what does it innervate?
•The splanchnic nerves are paired visceral nerves (nerves that contribute to the innervation of the internal organs), carrying fibers of the autonomic nervous system (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.
71
How is a CT scan to be interpreted?
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
72
Are the right and left main bronchi different? Is this clinically important?
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
73
What is a transosophageal echo?
• 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).
74
What pathology is caused by damage to the stellate ganglion?
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.
75
What structures drain blood into the azygous system?
The superior intercostal veins
76
Why is the left recurrent laryngeal nerve at risk from thoracic disease but not the right?
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
77
Where do the sympathetic nerves attach to the central nervous system?
Sympathetic nerve fibers originate in the intermediolateral horns of the gray matter of the spinal cord between segments T-1 and L-3
78
What is the arrangement of the sternocleidomastoid muscle?
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
79
Where may the accessory nerve be identified during an anterior triangle dissection?
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
80
What small muscles lie between the two sternocleidomastoid muscles and run vertically?
The infra-hyoid muscles
81
What are the attachments of the sternohyoid muscle?
from Sternum to the hyoid bone
82
Where would one find the omohyoid muscle and what are its attachments?
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.
83
What action must be taken to reveal the deeper sternothyroid and thyrohyoid muscles?
Fold sternohyoid upwards
84
Where would one find branches of ansa cervicalis (nerve) in the anterior triangle?
passing to the strap muscles from behind the carotid sheath
85
What must be reflected to reveal the thyroid gland?
reflect sternothyroid muscle superiorly
86
What is the brief structure of the thyroid gland?
* 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.
87
What would be found at the superior and inferior poles of the thyroid?
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.
88
What lies on the posterior surface of the thyroid gland?
Lying on the posterior surface of the thyroid gland are four glands; a pair of superior and a pair of inferior parathyroid glands
89
What is the carotid sheath and where is it?
• 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).
90
Where is the carotid sinus?
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.
91
Where is the carotid body?
Just in the ‘v’ of the bifurcation is the carotid body, a chemoreceptor which measures blood pH and feeds into the control of breathing
92
Give three examples of the clinical relevance of the thyroid gland?
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.
93
What is the function of the extrinsic laryngeal muscles (sternothyroid, thyrohyoid etc?)
act to move the larynx superiorly and inferiorly
94
Where can you create an emergency airway?
In the cricothyroid membrane
95
Why does the thyroid have such a good blood supply?
It secretes hormones directly into the blood supply therefore is highly vascularised
96
Which structure may be compressed by an enlarged thyroid gland?
The trachea
97
What is the only complete cartilage ring around the airway?
Cricoid cartilage
98
A patient may develop hypocalcaemia after thyroid surgery,why?
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.
99
What is the arterial supply and venous drainage of the thyroid gland?
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 – the thyroid 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 a venous plexus around the thyroid gland.
The superior and middle veins drain into the internal jugular vein and the inferior empties into the brachiocephalic vein.
100
What are the boundaries of the carotid triangle?
· 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 the common carotid artery (which bifurcates within the carotid triangle into the external and internal carotid arteries), the internal jugular vein, and the hypoglossal and vagus nerves
101
What are the boundaries of the submental triangle?
· Inferiorly – hyoid bone.
· Medially – midline of the neck.
· Laterally – anterior belly of the digastric
The base of the submental triangle is formed by the mylohyoid muscle, which runs from the mandible to the hyoid bone.
102
What are the boundaries of the submandibular triangle?
· Superiorly – body of the mandible.
· Anteriorly – anterior belly of the digastric muscle.
· Posteriorly – posterior belly of the digastric muscle.
103
What are the boundaries of the muscular triangle?
· 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.
104
What is the path of the thoracic aorta and what are its branches?
The thoracic (descending) aorta is a continuation of the arch 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, the thoracic aorta becomes the abdominal aorta, and passes through the aortic hiatus of 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 extend anteriorly, paired branches to viscera extend laterally, and paired segmental parietal branches extend mostly posterolaterally. 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.
105
What is the typical structure of a rib and give examples of typical ribs?
The typical rib consists of a head, neck and body:
The head is 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.
The neck contains no bony prominences, 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, or shaft of 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
106
Which ribs are atypical and why?
1, 2, 10, 11, and 12
Rib 1 is 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 2 is 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 the serratus anterior muscle originates.
Rib 10 only has one facet – for articulation with its numerically corresponding vertebrae.
Ribs 11 and 12 have no neck, and only contain one facet, which is for articulation with their corresponding vertebrae.
107
What is the posterior articulation for the ribs?
All the twelve ribs articulate posteriorly with the vertebrae of 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.
108
What are the anterior attachment for the ribs?
The anterior attachment of the ribs vary:
• Ribs 1-7 attach independently to the sternum.
• Ribs 8 – 10 attach to the costal cartilages superior to them.
Ribs 11 and 12 do not have an anterior attachment and end in the abdominal musculature. Because of this, they are sometimes called ‘floating ribs’.
109
Where does the mammary gland lie and what is its structure?
within the subcutaneous layer, an accessory gland of the female reproductive system. The mammary glands are the key structures involved in lactation.
110
Is the breast attached to the deep fascia over pectoralis major?
breast is not attached to the deep fascia over the pectoralis major muscle
111
What is the structure and the surface markings of the breasts?
* The breast is located on the anterior thoracic wall. It extends horizontally from the lateral border of the sternum to the mid-axillary line. Vertically, it spans between the 2nd and 6th costal 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 the nipple, composed mostly of smooth muscle fibres. Surrounding the nipple is a pigmented area of skin termed the areolae. There are numerous sebaceous glands within 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 a connective tissue stroma.
112
What is the arterial supply of the breasts?
* Arterial supply to the medial aspect of the breast is via the internal thoracic artery (also known as internal mammary artery) – a branch of the subclavian artery.
* The lateral part of the breast receives blood from four vessels:
* Lateral thoracic and thoracoacromial branches – originate from the axillary artery.
* Lateral mammary branches – originate from the posterior intercostal arteries (derived from the aorta). They supply the lateral aspect of the breast in the 2nd 3rd and 4th intercostal spaces.
* Mammary branch – originates from the anterior intercostal artery.
* The veins of the breast correspond with the arteries, draining into the axillary and internal thoracic veins.
113
What is the lymphatic drainage in the breasts?
• The lymphatic drainage of the breast is of great clinical importance due to its role in the metastasis of 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.
114
What is the innervation of the breast?
* The breast is innervated by the anterior and lateral cutaneous branches of 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 the pituitary gland.
115
What are the attachments and structure of pectoralis major?
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.
116
What structure runs in the groove between the deltoid muscle and pectoralis major?
The cephalic vein
117
Name the two neurovascular bundles visible when pectoralis major is retracted?
the medial and lateral pectoral nerves
118
What are the origins of pectoralis minor?
its origins on the 3rd, 4th and 5th ribs
119
Describe the structure of serratus anterior?
* 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
120
What is the external oblique muscle?
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.
121
How does contraction of pectoralis major assist in breathing?
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.
122
Which bony structures lie subcutaneously in the anterior chest wall?
Clavicle and sternum
123
What are the articulations of the clavicle?
The sternoclavicular joint, the acroclavicular joint
124
What forms the anterior axillary fold?
The lowest and most lateral part of pectoralis major.
125
What lies deep to pectoralis minor muscle?
Part of the axilla
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?
It drains into the lymph nodes in the axilla (the axillary lymph nodes)
127
Which costal cartilage connects to the sternum at the sternal angle?
2nd rib costal cartilage
128
Describe the appearance of the intercostal muscles?
* 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.
129
Where do the intercostal nerves run?
They run deep to the internal intercostal muscles in a groove just below the rib
130
What is the hilum and what can be located there?
* 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)
131
What is the difference between visceral and parietal pleura?
• 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.
132
what are the four pleurae and two recesses that may be identifed?
cervical, mediastinal, diaphragmatic and costal parietal pleurae, and also the costo-diaphragmatic and costo-mediastinal recesses
133
What nerve supplies the diaphragm for both motor and sensory innervation?
the phrenic nerve for both motor and sensory function and arises from the 3rd, 4th and 5th cervical spinal nerves.
134
What happens when the diaphragm contracts?
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
135
What breathing involves accessory muscles?
• 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.
136
How does the internal mammary artery relate to coronary artery disease?
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
137
Which nerves carry sensation from the parietal and visceral pleura?
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
138
What is a bronchopulmonary segment?
bronchopulmonary segment is a portion of lung supplied by its own bronchus and artery. Each segment is functionally and anatomically discrete allowing a single segment to be surgically resected without affecting its neighbouring segments.
139
What is the surface markings of the lowest extent of the lungs?
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
140
What is intercostal recession?
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, your intercostal muscles pull sharply inward. These movements are known as intercostal retractions, also called intercostal recession.
141
Describe the surface anatomy of the lungs?
* 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
142
How many terminal bronchioles are there?
40 million
143
How many alveoli are there?
around 300 million
144
How many lobes, fissures, and bronchopulmonary segements does each lobe have?
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
145
What is the arterial supply and venous drainage for the lungs?
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Bronchial artery (oxygenated blood)
2x pulmonary arteries (deoxygenated blood)
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Bronchial vein (drain to azygous vein deoxygenated blood)
Pulmonary vein (drain into left atrium oxygenated blood)
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146
What are the two movements of breathing?
pump handle movement and bucket handle movement
147
Describe the mechanism of breathing?
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”
148
What are the divisions of the sternum?
Manubrium, body, and xiphisternum
149
Describe the manubrium sternum?
Manubrium
The manubrium is the most superior portion of the sternum. It is trapezoid in shape.
The superior aspect of the manubrium is concave, producing a depression known as the jugular 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 the sternoclavicular joints.
On the lateral edges of the manubrium, there is a facet (cartilage lined depression in the bone), for articulation with the costal cartilage of the 1st rib, and a demifacet (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 the sternal 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.
150
Describe the body of the sternum?
Body
The body is 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 numerous articular 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.
151
Describe the xiphoid process/ xiphisternum?
Xiphoid Process
The xiphoid process is 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.
152
What structures pierce the diaphragm at the caval hiatus (T8)?
Inferior Vena Cava and terminal branches of right phrenic nerve
153
What structures pierce the diaphragm at the oesophageal hiatus (T10)?
Oesophagus, right and left vagus nerves, oesophageal branches of left gastric artery/ vein
154
What structures pierce the diaphragm at the aortic hiatus (T12)?
Aorta, Thoracic Duct, and Azygous Vein
155
What is the structure of the thymus gland?
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 largely composed 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 of epithelial reticular cells. Their function is unclear.
The gland is mainly located within the thoracic superior mediastinum, posterior to the manubrium of the sternum. However, in some individuals, it can extend superiorly into the neck (reaching the thyroid gland), and inferiorly into the anterior mediastinum (lying in front of the fibrous pericardium).
The arterial supply to the thymus gland is via the anterior intercostal arteries and small branches from the internal thoracic arteries. Venous blood drains into the left brachiocephalic and internal thoracic veins.
156
What is the structure of the lungs?
The lungs are roughly cone shaped, 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.
157
What is the lung root?
The lung root is a collection of structures that suspends the lung from the mediastinum. Each root contains a bronchus, pulmonary artery, two pulmonary veins, bronchial vessels, pulmonary plexus of nerves and lymphatic vessels.
158
What is the innervation of the lungs?
The nerves of the lungs are derived from the pulmonary plexuses. They feature 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.
159
What is the lymphatic drainage in the lungs?
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 the trachebronchial nodes – located around the bifurcation of the trachea and the main bronchi. From here, lymph passes into the right and left bronchomediastinal trunks.
160
What is the structure of the trachea?
The trachea, like all of the larger respiratory airways, is held open by cartilage – here in C-shaped rings. The free ends of these rings are supported by the trachealis muscle.
The trachea and bronchi are lined by ciliated pseudostratified columnar epithelium, interspersed by goblet cells, which produce mucus. The combination of sweeping movements by the cilia and mucus from the goblet cells forms the functional mucociliary 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 the carina runs anteroposteriorly between the openings of the two bronchi.
The trachea receives sensory innervation from the recurrent laryngeal nerve.
Arterial supply comes from the tracheal branches of the inferior thyroid artery, while venous drainage is via the brachiocephalic, azygos and accessory hemiazygos veins.
At the level of the sternal angle, the trachea bifurcates into the right and left main bronchi.
161
What is the innervation of the bronchi?
The bronchi derive innervation from pulmonary branches of the vagus nerve (CN X)
162
What is the origin, insertion, innervation, and primary action of pectoralis major?
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.
163
What is the origin, insertion, innervation, and primary action of pectoralis minor?
Origin: Anterior aspect of ribs 3, 4 & 5
Insertion: Coracoid Process of Scapula
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Innervation: Medial Pectoral Nerve
Primary Action(s): Stabilise the Scapula against the thoracic wall Also assists with inspiration when scapula is fixed
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164
What is the origin, insertion, innervation, and primary action of Serratus Anterior?
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.
165
What is origin and course of the internal mammary (thoracic) artery and what does it supply?
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.
166
What structures are in the lung hila and what is the orientation?
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.
167
What is the lung pleura innervation?
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
168
What are the surface markings for the lungs and the pleural cavity?
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.
169
Describe the intercostal neurovascular bundles?
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.
170
What is the origin, course, function and clinical notes for the recurrent laryngeal nerve?
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.
171
What is the origin, course, function and clinical notes for the sympathetic chain?
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’.
172
What are the splanchnic nerves?
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
173
What is the origin, course, function, and clinical notes for the thoracic duct?
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’.
174
Describe the superficial neck muscles?
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).
175
What is the location, function, blood supply and drainage, and clinical notes for the thyroid gland?
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
176
Describe the pharyngeal constrictors?
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.
177
What is the hyoid bone?
• Horseshoe-shaped bone at the top of the larynx.
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What is the thyroid cartilage?
Main, large cartilage of the larynx, below the Hyoid bone.
| • Anterior prominence commonly known as the ‘Adam’s Apple’.
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What is the cricoid cartilage?
Signet-ring shaped cartilage below the thyroid cartilage.
• Short at the front, tall at the back.
• Only complete cartilaginous ring of the airway
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What is the epiglottis?
• Leaf-shaped cartilage that can ‘fold’ down to cover the glottis when swallowing.
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What are the arytenoid cartilages?
• 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.
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What are the Aryepiglottic Folds?
Sheets of membrane that attach the lateral aspects of the epiglottis to the Arytenoid cartilages.
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What is the vallecula?
Anterior space at the base of the epiglottis where it meets the thyroid cartilage.
• Food can get stuck here, causing an uncomfortable sensation
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What are the piriform recesses?
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
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What is the cricothyorid membrane?
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’
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What is the cricothyorid muscle?
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)
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What is the posterior cricoarytenoid muscle?
On the back of the larynx.
• Opens (abducts) the vocal cords.
• Only muscle that opens the vocal cords.
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What are the Transverse and
| Oblique InterArytenoids muscles?
* On the back of the larynx.
| * Closes (adducts) the vocal cords.
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What is the Lateral
| Cricoarytenoid muscle?
On the inside at the sides of the larynx.
| • Closes (adducts) the vocal cords.
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Describe the innervation of the larynx?
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.
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Describe the salivary glands?
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.
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What are the palatine arches?
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.
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What is the lingual frenulum?
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.
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What are the paranasal sinuses?
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
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What is the cribriform plate?
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
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What are nasal conchae?
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
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What is the sphenoethmoidal recess?
* Space above the superior concha, but below the base of the skull.
* The sphenoid sinus and posterior ethmoid sinus drain into this space.
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What is the superior meatus?
Space below the superior concha, but above the middle concha.
• Some sources state that the posterior ethmoid sinus drains into this space
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What is the middle meatus?
Space below the middle concha, but above the inferior concha.
• The frontal, maxillary and anterior & middle ethmoid sinuses drain into this
space.
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What is the inferior meatus?
Space below the inferior concha, above the floor of the nasal cavity.
• The Nasolacrimal duct (carrying tears) drains into this space.
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What is the Eustachian Tube?
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
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What is the infra-orbital nerve?
* Nerve that supplies sensation to the skin over the cheek.
| * Runs in a groove in the superolateral wall of the maxillary sinus.
