Thorax - Part 3

Thorax'3' Medias.num' Tracheo3bronchial'tree'  Lungs'

Mediastinum is the seperation b/w the left and right pleura. When they come together they sandwich some important things. Cranial part has esophagus and trachea. The middle part contains the heart. Caudal part contains the caudal vena cava

Medias.num'

Level of tracheal bifurcation!

Level of the heart!

Dorsal section at

Dorsal view at

Pleural cavity on this side is rather simple. On the other side (at the level of the heart) its alot more complex. On the right side the caudal mediastinum is pushed off to the left by the heart and the accessory lobe of the right lung.

1-3. parietal pleura1. costal pleura2. mediastinal pleura3. diaphragmatic pleura4. visceral pleura5. diaphgragm6. parietal and visceral pericardium7. cranial mediastinum8. caudal mediastinum9. plicae venae cavae10. costodiaphragmatic recess

In blue - outline of the parietal pleura - lines the wall of each pleural cavity. A portion of the parietal pleura is along the ribs : costal pleura. A portion along the diaphragm (diaphragmatic pleura) and along the mediastinum (mediastinal pleura).

Pleca venae cavae

Pleura'&'Medias.num'

Middle'medias.num' Caudal'medias.num'

9 - Pleca venae cavae.

Dog'3'diaphragm'

Characterised by a outer muscle and a middle aponeurosis (a tendon that is broad and flat). Diaphragm has a bundle of muscle that starts under L2 and L3 and comes forward and sandwich the two hiatuses (esophagus and aortic). The bundle of muscles then fan out to form the rest of the diaphragm. The rest of the diaphragm has peripheral muscle fibers and a central tendon. The central tendon can be very thin in some species but it is still very tough. The tendon in the middle is often referred to as having a trefoil shape (looks like a 3-leaf clover). The trefoil shape is because the esophagus/aortic hiatus to move around and the caudal vena cava foramen.

CRANIAL

1. Aorta2. Esophagus3. Caudal vena cava4. tendinous center5. Sternal and costal parts of diaphragm6. Attachment of plica venae cava7. Attachment of caudal mediastinum

Development'of'respiratory'apparatus'

•  Common'origin'of'larynx,'trachea'&'lungs''– Ventral'groove'/outgrowth'off'foregut'(pharynx)''

– Branching'(≥12)'con.nues'aLer'birth'

•  Lobes'named'on'basis'of'branching'

Samantha Bray

Starts out as a groove off the pharynx. Trachea develops ventral to the esophagus. Develops into two buds that branches (5 generations in rodents) in large animals (12 generations of branches). The branching is not complete at the time of birth. So in neonate the lungs are still continuing to grow. If born too early this is why they have tremendous respiratory distress.

Outward appearance of lobes are different among species (b/c of outward fissures). Branching though is rather consistant.

Tracheo3bronchial'tree'

Trachea:'•  Ventral'midline'from'larynx'to'thoracic'inlet'

•  Esophagus'dorsally'(±'leL)'

•  Sternocephalicus'ventrally'

DSW 3-29"

Esophagus is kinda towards the left.

1. Esophagus2. Trachea3. Pharyngeal musculature4. Sternocephalicus5. Nuchal ligament

dog!

Ox!

Trachea'Semi3rigid'tube:''•  bends,'extends,'and'won’t'

collapse'•  Inner'mucosa'(ciliated'epith.,'

mucous'glands)'•  Fibrocar.laginous'middle'layer''

–  Car.lage'“rings”'and'elas.c'c.t.'–  Tracheal'muscle'

•  Adven..a'(neck)'or'pleura'(thorax)'

C-shaped ring of cartilage in the trachea. The C-shaped allows the bore of the tube to be changed by the trachealis muscle. In animals this feature prevents tracheal collapse and also allows movement of the head - trachea can extend along is longitudinal axis. Whats on the outside of the trachea? Innermost layer = mucosa - ciliated with lots of mucous (elevates the mucous towards the pharynx). Deep to that is a fibroelastic layer of cartilage C-shaped. Outermost is adventitia (connective tissue) allows the trachea to move around a little bit. When it enters the thoracic cavity it is surrounded by the pleura!

1. Mucous membrane2. Tracheal cartilage3. Adventitia4. Tracheal muscle (external in dogs, internal in cattle).

DOG

OX

Tracheo3bronchial'tree'

•  Trachea'– Principal'(or'chief)'bronchi'

•  Lobar'bronchi'–  Segmental'bronchi'

»  Bronchioles'

'

pig"

1st division divides it into principal bronchi (left and right) AKA the chief bronchi. The pig has a branch (tracheal bronchus) that comes off before the major bifurcation. It goes towards the right cranial lobe in pigs/ruminants. Next branching goes to specific lobes (called lobar bronchi - cranial lobe, middle lobe, or caudal lobe on the right and on the left the cranial and caudal lobe). After that there are segmental bronchi that go to little bronchioles and then eventually the alveolia.

Tracheo-bronchial tree Trachea

Principal bronchi Left Right Lobar bronchi cran caud cran mid caud acc. Segmental bronchi cran caud Bronchioles ----- no cartilage, no glands, < 1 mm -----

Respiratory bronchioles Alveolar ducts Respiration Alveoli

The right lung is better than the left lung!

In some species there are cranial/caudal part of the cranial lobe on the left lung.

PaYern'of'loba.on'

' ''Cat ' ' '''''Dog ' ' ' 'Pig'

Tracheo-bronchial treeParenchyma (bronchial tree and alvoli)Interstitium (stroma) of elastic & cartilagenous tissue and smooth muscle, vessel and nerves.The elasticity allows the lungs to expand as much as they do and then passively contract. Broncho-pulmonary segment: seperated from another segment by stroma. If there is alot of stroma (connective tissue can be seen as marbelling appearance on the lungs (divides lung into lobules - very prominant in cattle not so much in horses/small ruminants).

A. trachea B. cranial lobar bronchusC. middle lobar bronchusD. caudal lobar bronchusE. accessory lobar bronchus.

Pulmones'(La.n)'Pneumon'(Greek)'

•  Color'•  Texture'•  Shape'•  Float'

Fresh lungs: looks smooth & shiny with an pink/tan colour. Lined by pulmonary pleura (single cell layer of mesothelium with a bit of CT underneath). No fibrin tags - there is an indication of pleuritis. Cattle and pigs vary in this - you may see a dark hemoraggic area - depending on how the animals die or how the lungs were set the blood will pool in a certain area.

Site'of'respira.on'

•  Disappearance'of'car.lage'

•  Increase'in'smooth'muscle'

•  Tall'columnar'to'cuboidal'epithelium'

•  Lobules'or'acini'='clumps'of'alveoli'

Samantha Bray

Broncho-pulmonary segments or lobules = clumps of bronchioli and associated alveoli separated by connective tissue.

basal border

ventral border

dorsal border

apex

basal border - lies against the diaphragm

lies near the sternum

along dorsal aspect

What would be peaking out in the circled area: the heart (called the cardiac notch)

COSTAL SURFACE

Left Lung of a Dog

costal surface

caudal lobe

Left Lung of a Dog

cranial lobe

cranial part

caudal part

Fissures between the lobes are deep and go to the hilus of the lung (root - where the lung is anchored down and receives its blood and nerve supply) in dogs and cats.

caudal lobe

Right Lung of a Dog

cranial lobe middle

lobe

Also has a accessory lobe medial to the middle lobe.

tracheal bronchus

accessory lobe

Bovine – right lung

More blood & trachea cuts sagitally. The tracheal bronchus goes to the cranial lobe!. Where the scissors pass through is where the caudal vena cava passes.

mediastinal surface

diaphragmatic surface

Bovine – right lung

Hilus'of'lung'

AKA the root of the lung.

cranial lobe

middle lobe

5) accessory lobe

caudal lobe

Root of the lung contains the chief bronchus, pulmonary artery and veins, lymphatics, and nerves within a covering of pleura provided by the reflection of mediastinal pleura onto the lung.

Vasculature'

•  Pulmonary'artery'(no'O2)'–  Single'vessel'leaving'the'right'ventricle''

•  Pulmonary'vein'(O2)'–  One'vessel'from'each'lobe'enters'leL'atrium'

'

pig"

Pulmonary artery - only artery in the body that pumps deoxygenated blood. Pulmonary vein is the only vein that carries deoxygenated blood.

Bronchial'artery'

2 or 3 come directly off the aorta. They supply the lungs and are independant of the pulmonary artery and the pulmonary vein.

Pair of bronchial arteries arise from aorta to supply the bronchi and assoc connective tissue partitions. Corresponding set of bronchial veins return to right atrium via the azygous vein.

1. Esophagus2. Trachea3. Tracheal bifurcation4. Aorta5. Bronchial artery6. Caudal lobe of left lung

LeL'lung'3'equine'

Equine lungs not very lobated (fissures are very suttle). They have a left cranial and caudal lung lobes and the same lobar bronchi.

aorta

esophagus

Right'lung'3'equine'

smooth and suttle lobes.

cranial

caudal

diaphragm

Species'comparisons'"" " " " " Eq " Ru " Por Carniv.""Lobulation "Smooth +++ " ++ " " "Smooth"Fissures" "None - Deep but not to hilus - To hilus"Trach. bronch. " "- " "+ " + " " " "-"Trach. ridge" " "- " "+ " "- " " " "- """"

Note: "–  Left cranial lobe is divided in all but horse (& man)"–  Right cranial lobe not divided except in ruminants"–  Middle lobe not present in right lung of horse"

Tracheal bronchus - goes to the right cranial lobe in cattle/pigs. Deep fissures in ruminant lungs - the left and right cranial lobes both have cranial and caudal segments!!

line of pleural reflection

Dog

caudal border of the triceps

Dorsally at last rib

Crosses at ~9th c-c junction

Zone of Auscultation (or percussion) for the Lungs. Most of the cranial part of the pleural cavity is covered by the forelimb. Landmarks - just above the point of the elbow is about the 5th space (behind the 5th rib - just above the costo-chondral junction) and then go straight up to the caudal angle of the scapula. Go the penultimate ribs (2nd last rib). Cant hear much near the ventral borders because this is where the lung thins out. The loudest sounds are where the biggest tubes are. The line of pleural reflection (AKA the site of attachment of the diaphragm) - marks the end of the pleural cavity. The pleural cavity does not extend all the way to the costal arch. It stops at the line of pleural reflection - called this because the pleura that lines the inside of the ribs (costal pleura) meets the diaphragmatic pleura and makes a recess called the costo-diaphragmatic recess. Nothing lives in the recess except a little bit of fluid. To do a thoracocentesis you need to know where the recess is because you do not want to puncture the lungs. There is also a costo-mediastinal recess down here (circled area).

Cow


caudal border of the triceps 8th costochondral

junction

Last rib

Zone of auscultation in the cow is smaller. The line of pleural reflection goes from the last rib down to the ziphoid process of the sternum ( or the costo-chondral junction of the 8th rib).


caudal border of the triceps

Horse

Last rib

8-9th costochondral junction

Basal'border'of'lung'

'' ' ' ' ' ' 'Dog ' 'Ox'''''' 'Horse''Dorsal'end'of'rib '''12 ' '11' ' '16'(~penul(mate,rib)'Middle'of'rib ' '''' ' '8 ' ''9 ' ' '11'(~2/3,of,way,caudal)'Costochond'jct. '''' ' '6 ' ''7 ' ' ''6''

Loca.on'of'cardiac'notch'

'' ' ' 'Dog ' 'Ox'''''''Horse'LeL'side '334 ' '335* '''' '336*'Right'side '435* ''' '334** '334'

'*''recommended'site'of'cardiac'puncture'**wholly'under'cover'of'forelimb'

Samantha Bray

Samantha Bray

Samantha Bray

Samantha Bray

Diaphragm

Crura of the diaphragm

trachea

tracheal bifurcation into principal bronchi(usually at level of 4th to 6th rib space).

Thorax - Part 3

Health & Medicine

Transcript of Thorax - Part 3