9.1 - Respiratory System

Question 1

Conducting Portion

Answer 1

= air passages that lead to the sites of respiration with the lung (where gas exchange takes place)

FXN: conditions the air that is traveling within these passages

Question 2

Respiratory Portion

Answer 2

= portion of the respiratory tract in which gas exchange takes place

includes:

• respiratory bronchioles
• alveolar ducts
• alveolar sacs
• alveoli

Question 3

Ciliated Cells

Answer 3

= tall columnar cells with approximately 250 cilia each

FXN: to sweep the mucous coat from the level of the bronchioles to the upper respiratory tract

Question 4

Mucous Cells

Answer 4

• similar to intestinal goblet cells
• found interspersed among the ciliated cells

morphology: have large mucinogen granules in their cytoplasm

FXN: synthesize and secrete mucous from the nasal cavity to the level of the most distal bronchi

Question 5

Brush Cells

Answer 5

= columnar shaped cells with blunt microvilli on the apical aspect
- brush cells are often associated with a sensory receptor
FNX: is thus a general sensory role in the respiratory epithelium

Question 6

Small Granule Cells

Answer 6

• contain secretory granules
• considered to be part of the enteroendocrine cells of the gut + gut derivatives
• can occur singly or in groups
• when found in groups, are often associated with a sensory receptor –> called neuroepithelial cells

Question 7

Basal Cell

Answer 7

= stem cell that serves as a reserve population that maintains cell replacement of the epithelium from
nasal cavity –> distal bronchi

Question 8

Mucociliary escalator

Answer 8

= coordinated movement of mucous by the ciliated cells of the respiratory tract

• movement is from distal to proximal
• movement is considered an important protective mechanism in the lung

Question 9

Bronchus Associated Lymphatic Tissue (BALT)

Answer 9

= cellular region located in the lamina propria of the respiratory tract

• is considered lymphatic tissue
• includes cells: lymphocytes, plasma cells, eosinophils

Question 10

Trachea

Answer 10

= short, flexible air tube that serves as a conduit for air

• has c-shaped rings that maintain the potency of the airway
• originates at larynx –> extends down neck region to the thorax –> divides into 2 primary bronchi

Question 11

Bronchus

Answer 11

= air passage that divides into lobar and segmental branches
- conducts air to the distal lung

Morphology: bronchi can be identified by cartilage plates and a layer of smooth muscle

Question 12

Terminal Bronchioles

Answer 12

= smallest of conducting bronchioles

• lead to the respiratory zone
• lines by ciliated cells + clara cells
• Gas exchange does NOT take place at the level of the terminal bronchiole

Question 13

Respiratory Bronchioles

Answer 13

= constitute a transitional zone in the respiratory system

• are involved in conducting air and gas exchange
• along the walls contain thin walled out-pocketings = alveoli

Question 14

Clara Cells

Answer 14

FXN:

• Secrete surface-active agent
• stem cells that maintain bronchiole epithelium

Morphology
= non-ciliated cells
= dome-shaped apical aspect that projects into lumen of the bronchiole

Question 15

Alveoli

Answer 15

= terminal air spaces of the respiratory system

• stie of gas exchange between air and blood
• each alveolus is surrounded by a capillary network
• surface is lined by Type I and Type II pneumocytes

Question 16

Type I pneumocytes

Answer 16

= Type I alveolar cells
FXN: gas exchange typically takes place across the type I pneumocyte

Morphology: extremely thin squamous cells joined together by tight junctions

Question 17

Type II pneumocytes

Answer 17

= Type II alveolar cells
= Septal cells
FXN
- secretory cell responsible for the synthesis and realse of the surface active agent, surfactant
- stem cell for both Type I and Type II pneumocytes

Question 18

Alveolar Septum

Answer 18

= wall that lies between two neighboring alveoli

• lined by cells and connective tissue
• thin wall surrounding passageways
• very small structure - hard to see even in EM
• Typically divided into thick and thin parts

Thick Part contains:
- fibroblasts, macrophages, eosinophils + ECM

Thinnest part:
- air-blood barrier

Question 19

Air-Blood Barrier

Answer 19

• found at the thinnest part of the alveolar septum
• consists of (lumen–>blood):
  a thin layer of surfactant, type I epithelial cells (pneumocyte), fused basal lamina of the type I pneumocyte and capillary endothelial cell, capillary endothelial cell

Question 20

Alveolar Macrophages

Answer 20

• Found in both CT and air-space - can migrate across epithelium - mostly crawl along surface of epithelial lumen
• is the resident macrophage of respiratory system
• functions to remove inhaled particles + keep surface of surfactant area clear of debris
  EM morphology: see inclusions (more with a smoker)
  LM morphology: typically see clear/dark/black material in inclusions

Question 21

Alveolar pores

Answer 21

= openings in the alveolar septum

- allow for collateral air circulation between alveoli

Question 22

Pulmonar Circulation

Answer 22

• supplies the capillaries of the alveolar septum and arises from the pulmonary trunk that leaves the RV for the heart

Question 23

Bronchial Circulation

Answer 23

• Arises from the branches of the aorta
• bronchial arteries provide oxygenated blood to the tissues of the lung including: pleura, CT (except alveolar wall septum), walls of the bronchi and bronchioles

Question 24

During the 4th week of development body folding gives rise to fore/mid/hindgut. What structures does the foregut region of the gut tube give rise to?

Answer 24

• pharynx
• esophagus
• stomach
• superior duodenum

Question 25

What day of development does the lung bud appear and from where?

Answer 25

- the foregut (endoderm) gives rise to a ventral evagination --> called the respiratorydiverticulum also known as the lung bud - this occurs on day 22 of development

Question 26

True/False. As the lung bud grows into the developing pleural cavities it remains covered by splanchnic mesoderm.

Answer 26

True

Question 27

Which of the three embryonic layers derives the internal lining (epithelium) of the respiratory system (distal to the pharynx).

Answer 27

- the endoderm

Question 28

From which embryonic developmental layer (be specific) are the cartilage, muscle, vascular, and CT components derived?

Answer 28

- the splanchnic mesoderm.

Question 29

What is Hyaline Membrane disease? What is another name for it? What are the effects of the disease?

Answer 29

- occurs due to insufficient surfactant production. - named for its histological appearance - equivalent to respiratory distress syndrome - lack of surfactant prevents normal FXN in developing type I pneumocytes --> they become necrotic and leave their residue along the air-blood interface - further preventing lung FXN

Question 30

What is Fibrosis?

Answer 30

- CT scarring that occurs due to insults to the lung | - limits the capability of affected alveoli to develop

Question 31

What is bronchopulmonary dysplasia?

Answer 31

- alternate patterns of fibrosis and alveolar hyperplasia | - evident of a lung that has adapted to focal loss of function

Question 32

What are the three layers of the wall of the trachea?

Answer 32

1) Muscosa 2) Submucosal Layer 3) Adventitial Layer

Question 33

Describe the mucosa of the wall of the trachea

Answer 33

- pseudostratified epithelium | - rich elastic lamina propria

Question 34

Describe the submucosal layer of the wall of the trachea

Answer 34

- contains submucosal glands --> "tracheal seromuscous glands" - also called tracheal submucosal glands

Question 35

Describe the adventitial layer of the wall of the trachea

Answer 35

- binds trachea to adjacent structures - has C-shaped cartilage rings - trachealis muscle spans between the ends of the c-shaped rings

Question 36

What is the tracheal is muscle

Answer 36

- spans between the ends of the c-shaped rings of cartilage in the trachea

Question 37

What are the five cell types of the respiratory epithelium? (In the order of most prominent to least prominent)

Answer 37

1) Ciliated Cells - principle cell type 2) Mucous Cells - principle cell type 3) Basal Cells - principle cell type 4) Brush Cells - minor cell type (present in small #s) 5) Small Granule Cells - minor cell type (present in small #s and only viewable with specific stain)

Question 38

Describe the ciliated cells of the respiratory epithelium

Answer 38

- most numerous type - extend from the BM-->Lumen - each has ~250 cilia - FXN: beat in one direction to push mucous upward

Question 39

Describe the mucous cells of the respiratory epithelium

Answer 39

- almost as common as ciliated cells - similar to goblet cells of the intestine - extend from BM-->Lumen - mucous typically is washed out in H&E - work with ciliated cells to move particles from air

Question 40

Describe the basal cells of the respiratory epithelium

Answer 40

- stem cell of all tracheal epithelium - short cells - nuclei: prominent + near level of BM

Question 41

Describe the Brush cells of the respiratory epithelium

Answer 41

- columnar cells with microvilli - extend form BM-->Lumen - basal surface in contact with sensory nerve ending = also called receptor cells due to their general sensory role

Question 42

Describe the small granule cells of the respiratory epithelium

Answer 42

- hard to see without a special stain - have role in lung development - store hormones in membrane bound granules - associated with nerve fibers - may have role in regulating diameter of airway

Question 43

Surfactant

Answer 43

- reduces surface tension and facilitates the movement of air into cells - looks like a fuzzy line on airway lumenal side - made by Type II pneumocyte

Question 44

Describe the Organization of the alveolar septum (from the airway lumen to blood)

Answer 44

- Surfactant - Alveolar macrophage - Alveolar epithelium - Basement membrane - CT --> Elastic fibers + smooth muscle + dust cells - Basement membrane - Endothelium

Question 45

Describe the alveolar epithelium

Answer 45

- made up by type I pneumocytes (mostly), which are jointed together by tight JXNs and occluding JXNs - Also contains type II pneumocytes - simple squamous epithelum

Question 46

Describe the elastic fiber component of the CT in the alveolar septum and respiratory system

Answer 46

- surrounds larger blood vessels (pulmonary circulation) - found at tips of septa - to regulate opening of alveolar sac - essentially absent in the alveolar septa

Question 47

Describe the Smooth Muscle component of the CT in the alveolar septum and respiratory system

Answer 47

- Colocalizes with elastin | - will not see it with majority of alveolar septa

Question 48

Describe the Dust Cell component of the CT in the alveolar septum and respiratory system

Answer 48

- alveolar macrophages accumulate and move to the CT in larger airways when life span is finished - often will see ingested particles inside them - they can remain there throughout the life of the person

Question 49

Describe Type II Pneumocytes

Answer 49

- rounder/less squamous cell than the type I pneumocytes - tends to sit at the corners of where alveolar septa come together (because it is hardest to have a thin layer there and thus have gas exchange) - recognizable by intracellular structures called LAMELLAR BODIES - showing surfactant is being produced

Question 50

Describe the morphology of Type II pneumocytes in EM and LM

Answer 50

EM: - lamellar bodies with characteristic appearance (lines across them) - lamellar body extravation produces swirling characteristic appearance LM: - see rounder cells with clear dots - representing lamellar bodies - open nucleus - look similar to macrophage but use location to recognize them in LM