Larynx, Trachea, Lungs - Comparative Anatomy Practical Flashcards
why is the horse an obligate nasal breather
soft palate is very long in this species
caudal pillars (palatopharyngeal arch) of soft palate form cuff around larynx cause it to be positioned high up within nasopharynx
Give two anatomical adaptations which allow the horse to increase the airflow to the lungs when it is doing vigorous exercise.
1) nostrils dilate
2) glottis abducts
3) blood flow to nasal cavity reduced
The structures which form the laryngeal aditus are labelled in this specimen 1-3. Identify and list these.
- epiglottis
- corniculate process of arytenoid cartilages
- aryepiglottic fold
Which cartilage(s) articulate directly with the hyoid apparatus?
Only the thyroid cartilage which articulates with the thyrohyoid bones
What functional role is played by 1) the epiglottis and 2) the glottis during swallowing?
Epiglottis tips caudally and partially covers entrance to the aditus, the glottis is closed by the action of the lateral cricoarytenoid muscles during swallowing – this inhibits inspiration.
The position of the dorsal cricoarytenoid muscles are indicated [1]. What is the function of these muscles and give their innervation
Abduction or opening of the glottis- caudal or recurrent laryngeal nerves
identify the structures of the hyoid apparatus
identify the structures of the laryngeal skeleton
identify the structures of the laryngeal cartilages
identify the larynx structures
identify the intrinsic muscles of equine larynx
identify the structures of the equine larynx
identify the structures of the pharnyx and larynx
identify the structures of the larynx
what is the shape of the larynx
leaf like shape of epiglottis
what are the comparative features of the larynx
identify the structures
A: epiglottis
B: corniculate process of arytenoid cartilages
C: aryepiglottic fold
identify the labelled structures
A: arytenoid cartilage (with corniculate process)
B: aryepiglottic fold
C: epiglottis
D: thyroid cartilage (in horse the majority of the ventral floor of the thyroid cartilage is membranous and that this feature allows good surgical access to interior of the larynx in this species)
E: sectioned cricoid
Which cartilage(s) articulate directly with the hyoid apparatus?
Only the thyroid cartilage which articulates with the thyrohyoid bones
What functional role is played by 1) the epiglottis and 2) the glottis during swallowing?
Epiglottis tips caudally and partially covers entrance to the aditus, the glottis is closed by the action of the lateral cricoarytenoid muscles during swallowing – this inhibits inspiration.
The position of the dorsal cricoarytenoid muscles are indicated [2]. What is the function of these muscles and give their innervation
Abduction or opening of the glottis- caudal or recurrent laryngeal nerves
One of the lateral cricoarytenoid muscles [3] can be seen on the deeper dissection. This muscle lies medial to the thyroid lamina. What is the action and innervation of this muscle?
Adduction or closure of the glottis- caudal or recurrent laryngeal nerves
what are the vocalis and ventricularis muscles separated by
the lateral ventricle –> an out pocketing of the mucosa
where do the lateral ventricles project
laterally and lie medial to the lateral lamina of the thyroid cartilage
uncertain of the function –> may modify the voice sound produced by the vocal chords
what type of joint is the cricothyroid joint
synovial
how do each laryngeal joints attach
anchored to the cricoid cartilage and rotate about the cricothyroid joint
why are the tracheal rings C shaped and what controls this action
allows for some change in diameter of trachea
action is controlled by trachealis muscle
Where is the trachealis muscle located in the horse- dorsal or ventral to the open ends of the cartilage?
ventral (dorsal only in carnivores)
what is the action of the transverse arytenoid muscle
helps adduct (close) glottis
identify the vestibular folds, lateral recesses or ventricles, vocal folds, and vocal process of the arytenoid cartilages
- vocal fold
- vocal process
- dorsal surface of thyroids cartilage
- vestibular fold (false cord)
Identify the larynx and the main laryngeal cartilages visible in this specimen.
Does this species have lateral recesses or ventricles?.
no
Describe where the laryngeal aditus sit in relation to the nasopharynx/ common pharynx in this species?
Sits on the ventral floor of the laryngo-pharynx or common pharynx
can cows breath through its mouth
yes
where does the esophagus lie relative to the larynx
dorsal
what is the epiglottis shape in the bovine
spade and has rounded tip/apex whereas in horse the epiglottis is more pointed
what is the difference between the larynx in the horse and bovine
lack of ventricle and medial recess and short deep shape of vestibule
what is the most distinguishing feature in the pig larynx
bifid corniculate processes (double) on each arytenoid cartilage
has lateral ventricles and a median recess present
what does the cat lack
a corniculate process on the arytenoid cartilages
lateral ventricles are reduced to being a slight like depression
why is it more difficult to intubate a cat than a dog
The mucosa of the laryngeal vestibule in the cat is particularly sensitive. It is therefore more difficult to intubate a cat than a dog.
locate the larynx and identify the individual cartilages which are visible in this specimen
- lateral ventricle
- median recess (characteristic features of the larynx in this species)
- each arytenoid cartilage
- corniculate process (prominent)
- vocal process of arytenoid cartilage
equine larynx –> deep lateral view with thyroid lamina cut and reflected
equine larynx anatomy
equine larynx
pharynx
pig larynx
bovine larynx
dog larynx
Each arytenoid cartilage has a prominent corniculate process which is positioned rostral to the main part of each arytenoid cartilage
Lateral ventricles are present but there is no median recess in this species. Identify the laryngeal cartilages and the vestibular and vocal folds.
corniculate and cuneform processes of arytenoid cartilages, the vestibular, lateral ventricles or recesses and vocal folds and the aryepiglottic folds
cat tongue and pharynx
cat lacks a corniculate process on the arytenoid cartilages, and that the lateral ventricles are reduced to being just a slight like depression.
The mucosa of the laryngeal vestibule in the cat is particularly sensitive. It is therefore more difficult to intubate a cat than a dog.
dog tongue and pharynx
red = trachea
green = esophagus
blue = aorta
identify and name the individual lobes of each lung
right = cranial, middle, caudal and accessory
left = cranial-cranial crania-caudal, and caudal
what are the lobes in this species
horse, slab like in appearance
left = cranial and caudal
right = cranial caudal and accessory
this species doesn’t have a tracheal bronchus
identify the structure, what species is this and what are the major lobes
A = larynx
B = esophagus
C = trachea
D = tracheal bronchus
E = tracheal bifurcation into right and left primary bronchi
right: cranial (cranial and caudal), middle, caudal and accessory
left: cranial (cranial and caudal), caudal lobes
bovine –> The visceral pleura is particularly thick in the large ruminant . This gives the surface of each lung a very lobulated appearance.
identify the species, lobes and how you would distinguish this
pig
right: cranial, middle, accessory and caudal lobes
left: cranial (cranial and caudal), caudal lobes
lobulation is much less obvious than large ruminant
right lung is not divided in pig (it is in sheep/asymmetry in sheep as right lung divided and projects more cranially than left)
ventral neck region
- Common carotid artery
2 Vagosympathetic trunk
3 Internal jugular vein (relatively unimportant)
4 External jugular vein
5 Sternocephalic m
6 Sternohyoid m
7 Sternothyroid m
8 Thyroid gland
9 Cricothyroid m
10 Thyroid cartilage
11 Thyrohyoid m
Which major vessels and nerves lie within the carotid sheath and which major nerve lies just out with the carotid sheath?
Common carotid a.
Vagosympathetic trunk
Int. jugular v.
Recurrent laryngeal n. lies outwith
fresh ventral neck dissection
A Common carotid artery
B Vago sympathetic trunk
C Internal jugular vein (relatively unimportant)
D External jugular vein
1 Sternocephalic m
2 Sternohyoid m
3 Sternothyroid m
4 Thyroid gland
5 Cricothyroid m
6 Thyroid cartilage
7 Thyrohyoid m
what is this structure
D External jugular vein
identify the structures (blue, red and green)
BLUE:
- Epiglottis.
- Arytenoid cartilages.
- Thyroid cartilage.
- Lateral ventricle.
- Cricoid cartilage.
RED:
- Hard palate.
- Soft palate. (Note the relationship between the soft palate and the epiglottis; in quiet nasal breathing the latter should rest above the soft palate, to establish continuity of the respiratory passageway between the nasopharynx and the aditus).
- Nasopharynx.
- Oropharynx. (Usually containing some air, and therefore visible).
- Root of the tongue. (Visible as the soft tissue density on the floor of the oropharynx).
- Oesophageal lumen. (May be visible if some gas is trapped proximally).
GREEN:
- Thyrohyoid bone. (Although only one bone is identified in this radiograph, all the hyoid bones are paired, with the exception of the basihyoid bone).
- Basihyoid bone. (This single hyoid bone is viewed end-on in lateral radiographs, and therefore appears more radiopaque than the others).
- Ceratohyoid bone.
- Epihyoid bone.
- Stylohyoid bone.
what are the 4 standard radiographic views to assess the thorax of dog and cat
- right lateral (RLat)
- left lateral (LLAT)
- dorsoventral (DV)
- ventrodorsal (VD)
what does a complete exam of the lungfield require
- right lateral view
- left lateral view
- either dorsoventral or ventrodorsal view
What do you think the different options might be for restraining animals for thoracic radiography? (4)
- Unconscious – general anesthesia
- Conscious – sedation / un-sedated is animal quiet or sick
- Physical restraint - positioning aids eg sandbags, ropes etc
- Manual restraint – held by person in protective lead lined clothing
Why do you think the Dorsoventral view is more commonly used in practice that the Ventrodorsal view? Why is this particularly the case in dogs with respiratory problems?
Because conscious dogs tolerate this position better and it is easier to position.
Also dogs breath better when in sternal recumbency rather than dorsal recumbency which is a an important consideration when imaging dogs with respiratory problems.
What shape does the diaphragm have in each of these views? Note that recognizing this is a really easy way to work out what view you are looking at!
Right lateral – crura are parallel with R crus cranial to L
Left lateral – crura form Y shape with L crus cranial to R
What shape does the diaphragm have in each of these views? Note that recognizing this is a really easy way to work out what view you are looking at!
Dorsoventral – 2 bumps as abdominal contents push cupola cranially and crura not visible.
Also large area of contact with the heart
Ventrodorsal – 3 subtle bumps as abdominal contents push crurae cranially so superimposed onto cupula.
Also much smaller area of contact with the heart
The ventral margin of the lung field looks different in the right and left lateral views – why do you think this is the case?
The size and shape of the cardiac notch differs between the right and left lungs and this difference is visible in these radiographs.
what structures can be seen in lateral radiographs of thorax in normal animals
- trachea
- heart
- cranial vena cava
- cranial mediastinal structures
- diaphragm
- caudal vena cava
- pulmonary vessels
- bronchial tree
- aorta
where is the trachea in lateral radiographs
Clearly visible as a dark radiolucent band for its whole course in both neck and thorax. The tracheal bifurcation is visible as a radiolucent oval, due to a lateral radiograph showing a partial end-on view of the two principal bronchi diverging from the trachea at this point. Note that this oval is positioned between the aortic arch and the base of the heart,. it provides an important landmark for interpreting the position of structures in thoracic radiographs. Note also the acute angle (open caudally) between the trachea and vertebral column at the level of the tracheal bifurcation: this angle is diagnostically important as cardiac enlargement displaces the trachea
dorsally and closes this angle
where is the heart in lateral radiograps
With a dog in lateral recumbency, the heart makes contact with the diaphragm if the animal is lying on its right side, but not if it is lying on its left side. In the cat, the heart often fails to contact the cupola; in addition, the obliqueness of the long axis of the heart is greater in the cat than in the dog
where is the cranial vena cava in lateral radiographs
Although obscured by other cranial Mediastinal structures, the ventral edge of the cranial vena cava may just be visible
where is the cranial mediastinal structures in lateral radiograph
A dense but vague shadow formed by the superimposed brachiocephalic vessels and oesophagus. In young animals the thymus may be large and dense enough to be visible
where is the diaphragm seen in lateral radiograph
Although the diaphragmatic profile in lateral radiographs varies greatly, it always shows at least three lines, formed by the left crus, the right crus and the cupola. The presence of (radiolucent) gas in the stomach, caudal to the diaphragmatic line, may be seen in some radiographs
where is the caudal vena cava seen in lateral radiographs
Normally visible in both dog and cat as a radiopaque band, ascending slightly caudodorsally, between the heart and diaphragm
where are the pulmonary vessels seen in the lateral radiographs
In good radiographs, branches of the pulmonary arteries and veins may be visible as radiopaque streaks accompanying the bronchi, particularly in the caudodorsal region between the heart and diaphragm
where is the bronchial tree on lateral radiographs
Bronchial branches may be visible as longitudinal or circular radiolucent (dark) shadows, often bordered by fine radiopaque lines representing the bronchial walls. However, due to the superimposition of many of the bronchial and vascular structures within the lung field; it may be necessary to look closely, and search for, clear examples of each. The main lobar bronchi are sometimes the easiest to see. Good quality radiographs aid such identification
where is the aorta seen on the lateral radiographs
The aorta is clearly visible for most of its thoracic course). Note: Neither the tracheobronchial lymph nodes nor the oesophagus are normally visible in lateral thoracic radiographs of the normal dog and cat. (Tracheobronchial lymph nodes may become visible if pathologically enlarged or dense, however, and occasionally a bubble of gas may be seen, as an unexpected radiolucent area, caught in transit down the normal oesophagus. The oesophagus can be demonstrated by giving a barium sulphate (radiopaque) meal). The pleural cavity is also not usually visible in radiographs
identify the structures in the lateral radiograph
How does the appearance of the diaphragm differ depending on whether the animal is in right or left lateral recumbency?
Right lateral- viscera weight forces right crus cranial to the left
Left lateral- the left crus is forced cranial to the right crus
what structures can be seen in ventrodorsal/dorsoventral radiographs of thorax
- heart
- cranial vena cava
- cranial mediastinal structures
- diaphragm
- caudal vena cava
- bronchi and pulmonary blood vessels
- aorta
where is the heart in VD/DV radiographs
Note the apex substantially to the left of midline
where is cranial vena cava seen in DV/VD radiographs
Largely obscured by the general shadow of the cranial ) mediastinal structures, but its right lateral border should be visible in well-exposed radiographs
where is the cranial mediastinal structures seen in DV/VD structures
A broad but undetailed shadow formed by the superimposed brachiocephalic and subclavian vessels, and the oesophagus. Will include the thymus in young animals
where is the diaphragm seen in DV/VD radiographs
The caudal mediastinum (4a), probably reinforced by the phrenicopericardial ligament, is commonly seen passing from the fibrous pericardium to the left side of the diaphragmatic cupola
where is the caudal vena cava seen in DV/VD radiographs
Nearly always distinguishable on the right side, passing between the caudal surface of the heart and the right aspect of the diaphragmatic cupola
where is the bronchi and pulmonary trunk on VD/DV radiographs
Visible in good radiographs as vague branching shadows, often forming a sort of herring-bone pattern. Superimposition of these structures, however, which often accompany each other within the lung, make distinctions between blood vessels and bronchi difficult
where is the aorta on VD/DV radiographs
Difficult to see in this view. In good radiographs may be faintly visible passing the apex of the heart, approaching the diaphragmatic cupola to the left of midline. Similar structures are seen in the cat, but less detail is visible compared to the dog; the aorta and caudal vena cava are difficult or impossible to see, and the heart may be virtually in the midline.
what are structures not normally seen in dorsoventral radiographs
- trachea
- tracheobronchial lymph nodes
- esophagus
- crura of diaphragm
identify the structures on the VD/DV radiographs
