L27: Lungs Flashcards
(33 cards)
1
Q
Origin, germ layer of the laryngotracheal diverticulum and tube
A
- Laryngotracheal diverticulum (pouch) forms at the ventral and caudal part of the forgegut. It develops from endodermal lining, which takes with it the splanchnic mesoderm as it grows
- Distal end enlarges to form respiratory bud
- It separates from primordial pharynx, but maintains communication via primordial laryngeal inlet
- The posteroinferior aspect of the laryngotracheal diverticulum has developing tracheoesophageal folds
- They approach each other and fuse to become the tracheoesophageal septum
- This septum divides ventrally into laryngotracheal tube and dorsally into oropharynx and esophagus
2
Q
Define and describe the structure which divides the laryngotracheal tube
A
- This structure is the tracheoesophageal septum
- Divides ventrally into laryngotracheal tube, which is primordium for larynx, trachea, bronchi and lungs
- Divides dorsally into oropharynx and esophagus
3
Q
Describe how the birth defect, tracheoesophageal fistula, develops
A
- Tracheoesophageal folds develop in the posteroinferior aspect of the laryngotracheal diverticulum, they fuse to become the tracheoesophageal septum
- This septum then divides ventrally into laryngotracheal tube and dorsally into oropharynx and esophagus
- Failure of this to occur, leads to tracheoesophageal fistula, esophagus and trachea are linked in some way – many variants.
4
Q
Describe the evolution of the respiratory (aka tracheal) and bronchial buds
A
- Respiratory bud arises when the distal end of the laryngotracheal tube (tracheal portion) differentiates at the ~ week 4.
- As the tracheal bud continues growing inferiorly, it forms two outpouchings known as primary bronchial (lung) buds
5
Q
Describe the adult derivatives of the endodermal tube and the overlying mesenchyme
A
- The endodermal lining of the laryngotracheal groove (caudal to 4th pharyngeal arch) develops into the epithelium and glands of larynx, trachea, bronchi and pulmonary epithelium
- Overlying splanchnic mesenchyme in these developing areas become cartilage, CT, muscles and visceral pleura (if any) associated with the lower respiratory structures
6
Q
Define and describe the space the body provides, in which, the bronchial (lung) buds grow into
A
- Bronchial buds grow laterally into mesenchyme surrounding pleuroperitoneal canals, which are the primordial of the pleural cavities. These cavities are always ahead to the growth of the lungs
7
Q
Discuss development of bronchi
A
- As tracheal bud grows inferiorly, it forms primary bronchial buds (endoderm)
- Bronchial buds grow laterally into mesenchyme surrounding
- Endodermal lining becomes epithelium and glands of bronchial branches, splanchnic mesenchyme overlying becomes cartilage, CT , muscles and visceral pleura
- Early in 5th week, mainstem bronchi form, these develop into secondary lobar bronchi
- Around 7th week, segmental bronchi develop with surrounding mesenchyme that separates bronchopulmonary segments
- By 24 weeks, there are 17 orders of branches, respiratory bronchioles have developed, additional 7 orders after birth
8
Q
Be able to describe the important developmental structures associated with the four stages in the maturation of the lungs. When do most mature alveoli form? Viability of fetus?
A
- ) Pseudoglandular period: 6-16 weeks
- early in this period, lungs resemble exocrine glands
- by 16 weeks, all major elements have formed except those necessary for gas exchange
- birth in this period not viable - ) Canalicular period: 16-26 weeks
- lumina of bronchi and terminal bronchi become larger, more highly vascularized
- by 24 weeks, terminal bronchiole have given rise to respiratory bronchioles each with alveolar ducts
- Some primordial alveoli (terminal saccules) may have developed
- Fetuses may survive with ICU, but this system with others are quite immature - ) Terminal sac period: 26 weeks-birth
- More terminal saccules develop, epithelium becomes thinner, capillaries starting moving in more
- Blood-air barrier better established
- By 26 weeks: type I pneumocytes (sq epi) and type II (surfactant producers) fully present - ) Alveolar period: 32 weeks-8 years
- about 95% of mature alveoli develop postnatally
- increase in size and number
- complete alveolar development by age 3, more may be added up to age 8
• most mature alveoli form in alveolar period 32 weeks to 8 years. In terms of viability, latter part of canalicular period with ICU ~ 26 weeks.
9
Q
Define relationship of tracheal bifurcation to the arch of the aorta and esophagus
A
- Trachea bifurcates at the carina, which is at the sternal angle (T4-5 vertebra)
- Trachea is behind the aorta, infront of the esophagus
- Trachea and esophagus are the structures furthest back
10
Q
What landmark indicates end of larynx and beginning of trachea? End of trachea?
A
- Cricoid cartilage at C6, C-shaped cartilages that open posteriorly after this
- End of trachea at sternal angle = carina
11
Q
Describe branching of the trachea and respiratory tree
A
- Trachea branches into the left and right main bronchi at the carina (sternal angle)
- Primary bronchi branch into secondary (lobar) bronchi (2 left to 2 lobes, 3 right to 3 lobes) and then into segmental, brochopulmonary segments)
- Bronchopulmonary segments divide segmental bronchi into terminal bronchioles, respiratory bronchioles, alveolar ducts and alveolar sacs
12
Q
What is the significance of the bronchopulmonary segments?
A
- These are the surgical units of the lungs that have own CT avascular septa that separate them from the larger lobes of the lungs. They have their own segmental arteries, bronchi and veins. As a result, these can be removed from the lung without disturbing function of other parts.
13
Q
Vasculature to the lungs
A
- Left bronchial arteries (two of them, inf and sup) come off aorta and run with left primary bronchus into left lung
- Right bronchial artery comes off aorta, then divides into two (inf and sup), which run with right primary bronchus into right lung
14
Q
Where are FB more likely to get lodged in the respiratory system? Why?
A
- In the right primary bronchus
- Right primary bronchus is wider, shorter and more vertical than left
15
Q
What vascular structure passes over the right primary bronchus? Over left primary bronchus?
A
- Over right: azygos arch connecting to the SVC
- Over left: aortic arch
16
Q
How many lobes does each lung have? Names of lobes. Fissures that divide each lung?
A
- 3 right, 2 left
- Right: upper(sup), middle, lower(inf)
- Left: upper(sup), lower(inf)
- Both have oblique(primary) fissures separating inf from sup lobes
- Right has horizontal(secondary or transverse) fissure separating sup from middle lobes
17
Q
Unique features of left lung
A
- Cardiac notch
- Cardiac fossa
- Lingula
18
Q
Lingula of left lung is projection from what lobe?
A
- Upper lobe of left lung
19
Q
Borders and margins of lungs
A
Borders and margins of lungs
20
Q
Surfaces of lung
A
- Cervical surface
- Costal surface
- Mediastinal
- Diaphragmatic
21
Q
Root vs hilum of lung
A
- Root = structures that go into lung
- Hilum = indentation of organ where structures go in and out from lung
22
Q
List the structures passing through the root of the lung
A
- Pulmonary ligament
- Pulmonary arteries and veins
- Bronchi
- Bronchial arteries and veins
- Nerves
- Lymphatics
23
Q
How to differentiate root structures of the lung in cadaver lab?
A
- Pulmonary artery is typically more thicker and more superior than pulmonary veins, even more so than bronchial arteries and veins
- Bronchi are thickest tubes in hilum
24
Q
List the margins of the lobes of the lung in relation to the ribs and the vertebral level
A
- ????
- Anteriorly: midclavicular line down 6th rib (T6 and T5) bilaterally = rib, below to rib 8 (T8 and T7) = pleura
- Posteriorly: scapular line down to 10th rib (T10 and T9) bilaterally = rib, below to rib 12 (T12 and T11) = pleura
25
List the subdivisions of the parietal pleura and their locations
1. ) Cervical surface = surface emerging through thoracic inlet
2. ) Costal surface = surface in contact with ribs
3. ) Mediastinal surface = surface in contact with mediastinal structures
4. ) Diaphragmatic surface = surface in contact with domes of diaphragm
26
Define: cardiac notch, cardiac fossa, pulmonary ligament and costodiaphragmatic recess
- Cardiac notch = anterior margin of left lung indentation as a result of heart placement
- Cardiac fossa = area in left lung where heart lives
- Pulmonary ligament = reflection of parietal pleura as it becomes visceral pleura
- Costodiaphragmatic recess = potential space where peripheral diaphragmatic pleura is in contact with the lowest part of the costal pleura.
* These are named for the surface they are on
27
What is the pleural cavity? What fluid is found here? Function?
- Space between two pleural membranes (visceral and parietal)
- Filled with serous fluid, which reduces friction between these layers as they move over each other
28
What attaches the parietal pleura to the thoracic wall?
- Endothoracic fascia
29
Two recesses found in thoracic cavity?
- Costodiaphragmatic recess
- Costomediastinal recess
- Reflections where specific pleural surface becomes another pleural surface
30
Describe the nerve supply to the parietal pleura
- Costal and cervical pleura = local intercostal nerves
- Mediastinal pleura = phrenic nerve
- Diaphragmatic pleura = central part (phrenic nerve) and peripheral part = local intercostal nerves
31
Which pleura is insensitive to pain and pressure?
- Visceral pleura
32
Nerve supply to lungs. Function?
- Via pulmonary plexus (ant and post) at carina. Post = main supply to lung.
- Sympathetics: vasoconstrictors and bronchodilators
- Parasympathetics: vasodilators, bronchoconstrictors, secretomotor and afferents (cough reflex/irritant receptor at carina, stretch receptors in bronchial tree for respiratory control and touch pain in respiratory epithelium)
33
Discuss lymphatic drainage of lung
- Two divisions: superficial lymphatic plexus and deep lymphatic plexus
1. ) superficial lie deep to visceral pleura (chicken wire): drain into superior and inferior tracheobronchial lymph nodes
2. ) deep lie within lamina propria of bronchi (none in alveoli) drain into pulmonary lymph nodes (within lung), then to bronchopulmonary (hilar) lymph nodes (outside lungs) into superior and inferior (carinal) tracheobronchial lymph nodes and then into bronchomediastinal lymph trunks, which respectively drain into thoracic duct (left side) and right lymphatic duct (right side)
