HE 20 21: Lung

Question 1

Trends of Tracheobronchial Tree

Answer 1

Epithelium: pseudostrat column to simple cuboidal
-less cleaning cells

Walls: less layers
-no more mucosa or cartilage

Structure: (cartilage) (sm + cart) (sm + EF)

Question 2

trachealis muscle

Answer 2

smooth muscle bundle posterior to C rings of cartilage in trachea

Question 3

key features of Trachea

Answer 3

cartilage rings

thickest epithelium

Trachealis Muscle

No muscularis

high in mucus from two places

• mucosal epithelium
• submucosal glands

epithelium/LP/submucosa

Question 4

kulchitsky cell

Answer 4

signals and regulates

• secretes basally serotonin and peptide hormone
• may affect nerve endings, goblet, & ciliated cells
• regulated secretion
• related to enteroendocrine of the gut

Question 5

Four types of cells in tracheal epithelium

Answer 5

goblet: mucus in lumen
ciliated: move mucus

basal cell: regenerates epithelium

kulchitsky cell: signals and regulates, basally secretes serotonin and peptide hormone, affects goblet, ciliated cells

Question 6

mucocilliary escalator and dysfunction

Answer 6

combination of ciliated cells that sweep mucosa out of the airway (mucosa contains particles trapped)

Cystic Fibrosis caused by mutation of Cl- channel in respiratory epithelium. Ion gradient becomes unbalances and luminal mucus dehydrates. This thick mucus impedes mucocilliary escalator, making this area prone to infection

Question 7

Intrapulmonary Bronchi Characteristics

Answer 7

Lobar and segmental
-hyaline cartilage plates

-continuous muscularis (corresponds to increasing role of bronchioconstriction)

segmental bronchus >bronchiole> lobule

lobule: independent blood drainage)

Question 8

Bronchioles and dysfunction

Answer 8

NO cartilage

thick muscularis: throws epithelium into folds

• NO MUCUS PRODUCTION
• simple columnar or cuboidal
• ciliated cells present but gradually lost

ASTHMA: inflammation of bronchi and bronchioles
-mast cells degranulation cause sudden constrictions of muscularis, narrowing lumen

Question 9

epithelial cells of bronchioles

Answer 9

ciliated cells present but gradually lost

simple columnar or cuboidal

-clara cellsL bulge into lumen: secrete surfactant keeping lumen open

terminal bronchiole: mostly clara, few ciliated, no alveoli buds

Question 10

components and significance of bronchiolar unit

Answer 10

respiratory bronchiole
alveoli
alveolar duct
alveolar sac

most gas exchange here
-appear lacey with islands (resp bronch) in histo

Question 11

resp bronchiole

Answer 11

alveoli buds

cuboidal clara cells

bronkens islands of smooth muscle

(trunk part: beginning of gas exchange)

Question 12

alveolar duct:

Answer 12

leads to alveolar sac

lacks smooth muscle islands

walls composed of alveoli

has sacs as base

Question 13

alveolus

Answer 13

small air capsul

surrounded by thin continuous extremely tight capillaries

• Type I and Type II pneumocytes
• alveolar macrophages

alveolar wall: simple epithelium +BL

Question 14

Type I pneumocyte

Answer 14

flat wide cell

95% of SA of wall
cannot regenerate

part of blood/air barrier

look for flat cell with nucleus that bulges into space

Question 15

type II pneumocyte

Answer 15

bubbly look from lamellar bodies (secretory vescicles with surfactant)
-different surfactant than clara

more abundant but only 5% of surface area of wall.

CAPABLE OF REGENERATION

Question 16

blood/air barrier

Answer 16

thin: gas exchange- continuous with blood vessels along alveolar septum (two alveolar walls)

thick areas: contain fibroblasts/elastic fibers, macrophages- serve to support

Question 17

dust cells

Answer 17

alveolar macrophages, phagocytose particulate matter in lumen and septum

Question 18

emphysema

Answer 18

too many particulates

dust cells become overactive

dust cells release enzymes that break down alveolar septa

-less surface area, less gas exchange, less recoil to expire air

Question 19

week 3, 4, 5 conceptualization

Answer 19

3: lateral plate mesoderm splits into parietal and visceral

4. lateral body folding
   -creates gut tube in embryonic cavity (coelom)
   cephalocaudal folding: pushes thick plate (septum transversum) between thoracic cavity and yolk sac
   -creates large openings (pericardioperitoneal canals)

4&5
canals compressed by lung buds to make two pairs of folds
-pleurocardial membranes (fuse witheachother and root of lunch to form pericardial and two pleural cavities

-lung budding also causes pleuroperitoneal folds to extend btween thor and ab. cavities creating thoracic diaphragm

Question 20

congenital diaphragmatic hernia

Answer 20

incomplete closure of one or both pleuroperitoneal membranes.

abdominal gut tube herniates into the pleural cavity compressing the lungs and prevents full development in infants

Question 21

lung embryonic origin

Answer 21

endoderm: epithelium of resp system

visceral mesodermL lamina propria, muscularis, submucosa, cartilage, adventitia, visceral pleura

Question 22

Respiratory Diverticulum and dysfunction

Answer 22

buds off ventral aspect of foregut: is the beginning of trachea and esophagus

-driven by Retinoic acid expression of adjacent visceral mesoderm driving TBX4

Esophageal atresia/tracheoesophageal fistulae- incorrect partitioning of the trachea and esophagus

• choking and regurg of food, pneumonitis, polyhydramnios
• most common (90)-atretic esophagus

Question 23

week five to early post natal lung development

Answer 23

primary-secondary-tertiary

bronchopulmonary segmentation

-continues after birth (six more divisions)

Question 24

month 7 to prenatal (10yrs)

Answer 24

at seven months, TRUE barrier for gas exchange is formed. continue to develop to 10 yrs.

see figure of capillaries micrating to alveoli (month 6)