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MS2 Respiratory > 9/11- Lung Embryology, Histology, Anatomy > Flashcards

9/11- Lung Embryology, Histology, Anatomy Flashcards

1
Q

What are the main phases of lung development with their time periods?

A
  • Embryonic (26 d - 5 wks)
  • Pseudoglandular (6 - 16 wks)
  • Canalicular (17-28 wks)
  • Saccular (29 wks - birth)
  • Alveolar (36 wks - 4 yrs)
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2
Q

What happens during the Embryonic phase (26 d - 5 wks)?

A

MAJOR AIRWAYS

LRT begins as a laryngotracheal diverticulum from primitive pharynx; major airways begin to form

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3
Q

What happens during the Pseudoglandular phase (6 - 16 wks)?

A

TERMINAL BRONCHIOLE

Major airways to the level of the terminal (membranous) bronchi

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4
Q

What happens during the Canalicular phase (17-28 wks) ?

A

PULMONARY ACINUS

Pulmonary acini and vascularization develop; by week 24 respiratory bronchioles form & respiration is possible, but chances of survival are slim

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5
Q

What happens during the Saccular phase (29 wks - birth)?

A

DISTAL AIRSPACES

Terminal sacs (alveolar ducts, alveoli) & adjacent lymphatic/capillary network develop, lined by type I & II pneumocytes; type II

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6
Q

What happens during the Alveolar phase (36 wks - 4 yrs)?

A

MATURE ALVEOLI

Newborn infant has only 1/6 to 1/8 of the adult number of alveoli; 95% of alveoli maturing after birth

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7
Q

When does surfactant reach adequate/functional levels?

A

2 weeks before birth

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8
Q

What is seen here?

A

7 week fetus (pseudoglandular): three lobes (left) & primitive tubular structure (right)

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9
Q

What is seen here?

A

18 week fetus (canalicular): pulmonary acini and vascular system form

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10
Q

What is seen here?

A

4 day old infant; resembles adult lung

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11
Q

What are the functions of the airways?

A
  • Conduits for air
  • Moisturizing and warming functions
  • Evacuation of foreign material via mucociliary escalator
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12
Q

Where (what vertebral level) does the trachea branch into R/L main stem bronchi? What is this called?

A

Carina

  • T4 - T5
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13
Q

Which main bronchi is longer/narrower? more vertical?

A

Left: longer, narrower

Right: more vertical

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14
Q

T/F: Aspirate material more frequently enters left vs. right lung

A

False! More into right (fatter, straighter)

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15
Q

How many lobar branches are there off the bronchi? Segmental bronchi?

A

Lobar bronchi: 3 on right, 2 on left

Segmental bronchi- 10 bronchopulmonary segments per lung

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16
Q

Describe bronchi histology

A
  • Cartilaginous airways
  • > 2 mm in diameter
  • Cartilage in walls that prevent their collapse (circumferential rings/plates)

Adventitia: Cartilagionous plates (as opposed to C-shaped cartilage in trachea) Submucosa: mucous glands

Muscular mucosa

Mucosa

1. Lamina propria

2. Respiratory epithelium: pseudostratified, ciliated columnar epithelium (90%) and goblet cells, neurosecretory (Kulchitsky) cells, clara, basal, and brush cells

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17
Q

Describe bronchiole histology

A
  • < 2mm in diameter
  • Lack cartilage and submucosal glands
  • No goblet cells
  • Lined by simple rather than pseudostratified epithelium

Membranous (terminal) bronchioles:

  • 0.5 - 1 mm
  • smooth muscle wall
  • lamina propria
  • Ciliated cuboidal cells and nonciliated secretory (Clara) cells

Respiratory bronchioles:

  • 0.15-0.2 mm
  • have alveolar ducts and alveoli budding from their walls
  • Cuboidal cells
  • Epithelium and alveoli; no smooth muscle!
  • +/- cilia along one side; alveoli along the other
  • Give rise to alveolar ducts (composed only of alveoli)
  • Forms part of pulmonary acinus
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18
Q

T/F: The right lung has 3 lobes while the left has 2

A

True

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19
Q

Which lobe does the lingula stem from?

A

Left upper lobe

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20
Q

Lungs are covered by what?

A

Visceral pleura

  • Parietal pleura covers the thoracic wall
21
Q

Define:

  • Pneumonectomy
  • Lobectomy
  • Segmentectomy
  • Wedge
A

Resection of:

  • Pneumonectomy: entire lung
  • Lobectomy: single lobe
  • Segmentectomy: bronchopulmonary segment
  • Wedge: less than a segment
22
Q

What is a pulmonary lobule?

  • Shape
  • Airway components
  • Clinical correlations
A

Smallest gross anatomic component

  • Polygonal shape, 1-2 cm diameter
  • Best visualized along pleural surface, bounded by connective tissue interlobular septa
  • Each lobule contains 3-5 terminal bronchioles and up to 30 pulmonary acini
  • Lobular architecture important for distinguishing major forms of emphysema
23
Q

What is seen here?

A

Can easily see polygonal pulmonary lobules

  • Can see pleural puckering from metastatic carcinoma
  • Anthracosis (carbon pigment deposition)- especially around these septal units
24
Q

What is seen here?

A

Normal lung

  • Alveolar septa
  • Clear alveolar spaces
25
Q

Describe the trachea histology

A

Adventitia: C-shaped cartilage

Submucosa: mucous glands Muscular mucosa

Mucosa

  1. Lamina propria
  2. Respiratory epithelium: pseudostratified, ciliated columnar epithelium (90%) and goblet cells, neurosecretory (Kulchitsky) cells, clara, basal, and brush cells
26
Q

What is the pulmonary acinus?

A

Functional unit of gas transfer (because lined by alveoli)

  • Pulmonary acinus = R.B. + A.D. + Alveoli
27
Q

Which epithelium is shown on the left? right?

A

Left: bronchiole epithelium

Right: tracheal and bronchi epithelium

28
Q

Pick out the:

  • Membranous bronchioles
  • Respiratory bronchioles
  • Alveolar ducts
A
29
Q

What are the cells of the alveoli (and their histological characteristics/functions)?

A

Type I pneumocytes

  • Flat squamous cells
  • Cover ~ 95% of alvoelar surface

Type II pneumocytes

  • Cuboidal cells that serve two functions:
    1. main cell type involved in alveolar repair
    2. source of surfactant

Alveolar macrophages

  • Loosely attached to epithelial surface or free in alveolar space
  • Phagocytic function
30
Q

What is surfactant?

A

Phospholipid that decreases alveolar surface tension; facilitating alveolar expansion

31
Q

Describe the content of alveolar interstitium

A
  • Capillaries
  • Elastic fibers
  • Myofibroblasts (support alveolar framework)
32
Q

What is the alveolar-capillary barrier?

A

Thinnest point for gas diffusion (0.2-2.5 um)

33
Q

What is this?

A

Type I pneumocyte

34
Q

What is this?

A

Type II pneumocyte

35
Q

What are Pores of Kohn?

A

Develop after birth; connect adjacent alveoli

  • Involved in collateral ventilation
  • 13-21 per alveolus
36
Q

What are Lambert’s canals?

A

Direct communication between airway (bronchiole) and adjacent alveoli

  • Involved in collateral ventilation
37
Q

T/F: the lung has a dual vascular supply?

A

True

38
Q

What are pulmonary arteries?

Where do they come from? Where do the go?

A

Accompany airways to lung periphery

  • Form capillary network around alveoli
  • Bring deoxygenated blood from right side of heart
  • About the same size of adjacent bronchiole
  • Dual elastic lamina
39
Q

What are bronchial arteries?

Where do they come from? Where do the go?

A

Systemic in origin arising from intercostal arteries and aorta

  • Form plexus around trachea and bronchial wall as far as respiratory bronchioles
  • Also supplies visceral pleura (supply nutrition to airways/lung)
40
Q

What are pulmonary veins? (where do they go)

A

Return oxygenated blood to the heart

  • Travel with interlobular septa
  • Single elastic lamina
41
Q

What are bronchial veins? (where do they go)

A

Deoxygenated blood to systemic circulation via azygos and intercostal veins

42
Q

What is seen here?

A

Membranous bronchiole with accompanying arteriole

  • “Bronchovascular channel”
  • Observe that they’re about the same size
43
Q

How to distinguish between pulmonary artery and vein?

A

Artery has two elastic lamina

44
Q

What is seen here?

A

Left: pulmonary artery

Right; pulmonary vein

45
Q

Describe the lymphatics of the lung

A

Two systems:

1. Superficial lymphatic drainage

  • Present along pleural surface

2. Deep (intrapulmonary) lymphatic drainage

  • Present adjacent to bronchovascular bundle and along interlobular septa

Connections exist between both forms of lymphatic drainage

46
Q

What is seen here?

A

Membranous bronchiole with pulmonary artery (bronchovascular channel)

  • Can see lymphatic channels (intraparenchymal)
47
Q

What is seen here?

A

Lymphatic channels (filled with metastatic cancer)

48
Q
A

(:

MS2 Respiratory (26 decks)

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