9/11- Lung Embryology, Histology, Anatomy Flashcards Preview

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Flashcards in 9/11- Lung Embryology, Histology, Anatomy Deck (48)
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1

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

- Embryonic (26 d - 5 wks)

- Pseudoglandular (6 - 16 wks)

- Canalicular (17-28 wks)

- Saccular (29 wks - birth)

- Alveolar (36 wks - 4 yrs)

2

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

MAJOR AIRWAYS

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

3

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

TERMINAL BRONCHIOLE

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

4

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

PULMONARY ACINUS

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

5

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

DISTAL AIRSPACES

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

6

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

MATURE ALVEOLI

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

7

When does surfactant reach adequate/functional levels?

2 weeks before birth

8

What is seen here?

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

9

What is seen here? 

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

10

What is seen here?

4 day old infant; resembles adult lung

11

What are the functions of the airways?

- Conduits for air

- Moisturizing and warming functions

- Evacuation of foreign material via mucociliary escalator

12

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

Carina

- T4 - T5

13

Which main bronchi is longer/narrower? more vertical?

Left: longer, narrower

Right: more vertical

14

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

False! More into right (fatter, straighter)

15

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

Lobar bronchi: 3 on right, 2 on left

Segmental bronchi- 10 bronchopulmonary segments per lung

16

Describe bronchi histology

- 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 

17

Describe bronchiole histology

- < 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

18

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

True

19

Which lobe does the lingula stem from?

Left upper lobe

20

Lungs are covered by what?

Visceral pleura

- Parietal pleura covers the thoracic wall

21

Define:

- Pneumonectomy

- Lobectomy

- Segmentectomy

- Wedge

Resection of:

- Pneumonectomy: entire lung

- Lobectomy: single lobe

- Segmentectomy: bronchopulmonary segment

- Wedge: less than a segment

22

What is a pulmonary lobule?

- Shape

- Airway components

- Clinical correlations

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

What is seen here? 

Can easily see polygonal pulmonary lobules

- Can see pleural puckering from metastatic carcinoma

- Anthracosis (carbon pigment deposition)- especially around these septal units

24

What is seen here? 

Normal lung

- Alveolar septa

- Clear alveolar spaces

25

Describe the trachea histology

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

What is the pulmonary acinus?

Functional unit of gas transfer (because lined by alveoli)

- Pulmonary acinus = R.B. + A.D. + Alveoli

27

Which epithelium is shown on the left? right? 

Left: bronchiole epithelium

Right: tracheal and bronchi epithelium

28

Pick out the:

- Membranous bronchioles

- Respiratory bronchioles

- Alveolar ducts 

29

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

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

What is surfactant?

Phospholipid that decreases alveolar surface tension; facilitating alveolar expansion