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

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

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

31

Describe the content of alveolar interstitium

- Capillaries

- Elastic fibers

- Myofibroblasts (support alveolar framework) 

32

What is the alveolar-capillary barrier?

Thinnest point for gas diffusion (0.2-2.5 um)

33

What is this?

Type I pneumocyte

34

What is this? 

Type II pneumocyte

35

What are Pores of Kohn?

Develop after birth; connect adjacent alveoli

- Involved in collateral ventilation

- 13-21 per alveolus 

36

What are Lambert's canals?

Direct communication between airway (bronchiole) and adjacent alveoli

- Involved in collateral ventilation 

37

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

True

38

What are pulmonary arteries?

Where do they come from? Where do the go?

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

What are bronchial arteries?

Where do they come from? Where do the go?

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

What are pulmonary veins? (where do they go)

Return oxygenated blood to the heart

- Travel with interlobular septa

- Single elastic lamina

41

What are bronchial veins? (where do they go)

Deoxygenated blood to systemic circulation via azygos and intercostal veins

42

What is seen here? 

Membranous bronchiole with accompanying arteriole

- "Bronchovascular channel"

- Observe that they're about the same size

43

How to distinguish between pulmonary artery and vein?

Artery has two elastic lamina

44

What is seen here? 

Left: pulmonary artery

Right; pulmonary vein

45

Describe the lymphatics of the lung

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

What is seen here? 

Membranous bronchiole with pulmonary artery (bronchovascular channel)

- Can see lymphatic channels (intraparenchymal)

47

What is seen here? 

Lymphatic channels (filled with metastatic cancer)

48

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