Histology of the Respiratory system week 5

Question 1

What are the general components of the respiratory system?

Answer 1

airways

lungs

blood/lymphatic vessels

nerves

Question 2

What are the 3 functions associated with the respiratory system?

Answer 2

gas exchange: O2/CO2 exchange, pH regulation, excretion

phonation (speech)

olfaction (smell)

Question 3

What are the 2 major divisions of the respiratory system? Give definitions.

Answer 3

Conducting portions (airways): moves air in and out of terminal structures (phonation and olfaction are associated with these structures)

Respiratory portion: structures where gas exchange occurs

Question 4

What structures composed the conducting portion of the respiratory system? Which are cartilage containing and which are not? Why is this important?

Answer 4

Question 5

What are the 3 parts of the nasal cavity and what are their components?

Answer 5

1. vestibule: lined by skin
2. respiratory region: conchae-creates turbulence in air so that it is warmed and moistened before reaching alveoli. lined by respiratory mucosa. mucus and hairs trap particles
3. olfacotry region: lined by olfactory mucosa (sense of smell)

Question 6

What type of epithelium is found in the respiratory region of the nasal cavity? What are the cell types found in the respiratory region?

Answer 6

respiratory epithelium: pseudostratified, ciliated columnar epithelium

Epithelial cell types:

• cilated cells:move mucus over epithelium
• goblet cells: produce and secrete mucus
  
  • above are main 2 cell types
• brush cells: have blunt microvilli, synapse with afferent nerve fibers (CN V); general sensory stimulation of mucosa
• granule cells: enteroendocrine cells. release factors into the local environment
• basal cells: stem cells. located in bottom layer

lamina propria: has a rich vascular network to warm and moisten inspired air

Question 7

What type of epithelium is found in the olfactory region of the nasal cavity? What are the cell types found in the olfactory region?

Answer 7

olfactory epithelium: specialized pseudostratified, cilated columnar epithelium. note it is thicker than respiratory epithelium

Epithelial cell types: (note: will not have to ID cell types in lab but must know for written and must ID olfactory epithelium as a whole)

• olfactory receptor cells: bipolar neurons
• sustenacular cells: supporting cells
• basal cells: stem cells
• brush cells: have blunt microvilli; synapse with afferent nerve fibers (CN V); general sensory stimulation of mucosa

Lamina propria:

• olfactory glands (Bowman’s glands): serous secretions act as a solvent to clear mucosa of odiferous substances
• olfactory nerves
• vasculature

Question 8

What is the function of the pharynx? What are its parts and what are their functions?

What is the function of the larynx? What are its parts and what are their functions?

Answer 8

Pharynx (behind nasal and oral cavities)

Functions:

• connects nasal/oral cavities to larynx and esophagus
• passage for air, food, and phonation

Parts:

• nasopharynx: connects to middle ear via Eustacian tubes, pharyngeal tonsils (AKA adenoids)
  oropharynx: palatine tonsils (can see when open mouth)

Larynx

• air passage btwn oropharynx and trachea
  phonation: vocal folds/vocal cords at boundary of larynx and trachea

Question 9

What are the 4 layers of the trachea? What are their functions/components?

Answer 9

1. Mucosa: (mucosa=epithelium + lamina propia)

• epithelial lining: barrier function (pseudostratified, ciliated columnar)
• lamina propria: immune cells, blood vessels

2. Submucosa: glands, nerves, blood vessels. is somewhat contiguous with mucosa
3. Cartilage layer: C-shaped rings of hyaline cartilage, trachealis muscle (smooth muscle). keeps airway open
4. Adventitia: CT, blood vessels, nerves

Question 10

What are the epithelial cell types of the trachea? What are their functions?

Answer 10

Epithelial cell types:
• Ciliated cells: move mucus over epithelium
• Goblet cells: produce and secrete mucus
• Brush cells – receptor cell – sparse
• Granule cells: enteroendocrine cells (catecholamine, serotonin, calcitonin, gastrin-releasing peptide)
• Basal cells: stem cells

Question 11

Brush cells and granule cells are involved in the local control of……? Through what mechanism do they exert this control?

Answer 11

brush cells and granule cells are involved in the local control of macrophage and mucocilary functions through cholinergic signaling mechanisms.

brush cells: sit in lumen and act as sensors. can send signals through basement membrane to effect local environment

granule cells: secrete factors across basal lamina into CT space. may get into bloodstream and effect distant cells

Question 12

What are the 5 layers of bronchi? What epithelial cell types do they contain?

Answer 12

1. Mucosa: Epithelia (pseudostratified, ciliated columnar) + lamina propria
2. Muscularis (smooth muscle layer)
3. Submucosa: blood vessels, nerves, glands
4. Cartilage layer – discontinuous cartilage plates
5. Adventitia (CT, vessels, nerves)

Epithelial cell types: same as trachea (ciliated, goblet, brush, granule, basal)

Question 13

What are bronchioles? How may they be told apart from other airways histologically?

What are the 3 layers of bronchioles?

What are the epithelial cell types of bronchioles?

Answer 13

Bronchioles:

• Are airways of 1 mm or less in diameter
• Lack cartilage!

if you see an area without cartilage and it does not have gas exchange portions (alveoli)=bronchioles

1. Mucosa: Epithelial lining -pseudostratified, ciliated columnar to low columnar in smallest bronchioles
   Lamina propria – scant
2. Smooth muscle - regulates airway diameter
3. Adventitia (CT, blood vessels, nerves)

Epithelial cell types:
Ciliated cells (very sparse)
Goblet cells
Clara cells
Granule cells
Stem cells

Question 14

What do clara cells look like? What is their function?

Answer 14

non-cilated, dome shaped apical surface

Secrete surfactant-like material (lipoprotein) to keep bronchioles from collapsing. Also secrete Clara cell protein CC16 which is a useful diagnostic marker for lung injury.

Question 15

True or false: As you go down the airway, there are less cilated cells and more clara cells. The height of epithelia also decreases and get more smooth muscle as you go down the airway.

Answer 15

True.

Question 16

What are terminal bronchioles? What type of epithelium do they have? What epithelial cell is abundant in terminal bronchioles?

Answer 16

• smallest portion of conducting system
• contain simple cuboidal epithelium
• have many clara cells

Question 17

_____ production is a problem in COPD.

Answer 17

mucus

Question 18

Where is mucus produced? How does the amount of mucus change as you go down the airway?

What are the functions of mucus?

Answer 18

Epithelial cells (goblet cells) and Sub-epithelial glands make mucus (see attached pic). Have less and less mucus as go down airway. Bronchioles do not have many/any mucus glands

functions:

• Protects and moistens airway
• Traps inhaled particles and pathogens
– Contains anti-inflammatory and anti-bacterial compounds and mucin proteins (these lend viscosity)

Question 19

Question 20

When do goblet cells normally secrete mucus?

Answer 20

Goblet cells make mucus constitutively and also upon stimualtion (sensory input)

An irritant may be sensed by brush cells (such as eating spicy food). The CNS then tells goblet cells to secrete more mucus. Cilia always beat upward to move mucus up the airway and into esophagus where it is swallowed.

Question 21

Inflammation from a variety of sources (infection, allergy, cigarette smoke) can alter mucus production in several ways. Name 3 of these ways.

What 2 genetic causes can lead to mucus blockage of airways?

Answer 21

1. Interleukin stimulated hyperplasia of goblet cells (more goblet cells)
2. Interleukin stimulated hyperproduction of mucus (stimulation of already existing goblet cells to secrete more mucus)
3. Interleukin stimulated loss of cilia function: mucus is not moved along properly

Genetic causes of mucus blockage of airways:

Primary ciliary dyskinesia

Cystic fibrosis

Question 22

Answer 22

As these 2 figures show, inflammation causes mucus accumulation and airway blockage through various lymphocyte/interleukin mediated mechanisms.

Question 23

In attached figure of cilia of a COPD pt, there is only one dynein arm on each microtubule pair. Why is this problematic?

Answer 23

Note how each microtubule doublet only has one dynein arm. should have 2 dynein arms on each doublet. otherwise they do not slide past each other and cilia do not beat. mucus stays static, becomes thick, and blocks airway.

Question 24

What is the cause of primary ciliary dyskinesia? What results as it relates to mucus and conditions/diseases that develop?

Answer 24

In primary ciliary dyskinesia, the dynein arms on microtubules of cilia are congenitally absent. Ciliary beat is compromised and mucus stasis occurs. Cilia do not beat at all. Pts have constant respiratory infections, COPD. Males are infertile due to immotile sperm.

Question 25

Why does mucus accumulate in pts with cystic fibrosis?

Answer 25

Altered chloride channel function leads to increased mucus viscosity, impaired mucus clearance and mucus stasis occurs. Mucus is produced normally but channel function is altered. Normally, mucus is hydrated. In CF, Cl- channel function leads to dehydrated mucus which is viscous. No matter how hard cilia beat, they are unable to move it along enough to combat mucus stasis.

Question 26

In pts with asthma, there are longterm changes in the alveolar wall. Describe the 2 main changes and how these changes come about as well as the effects they have.

Answer 26

1. Increased thickness of the smooth muscle layer (via mast cell and eosinophil stimulation) -- This results in increased constriction of the airway 2. Increased mucus secretion through CNS stimulaiton and chronic inflammation through effects of mast cells. Increased smooth muscle with no cartilage in bronchioles: smooth muscle contracts closing airway and there is no cartilage to keep it open. Reason for wheezing

Question 27

Describe in detail the roles of mast cells and eosinophils in asthma.

Answer 27

Mast cells: responsible for vasodilation and edema which maintains chronic inflammation. stimulate eosinophils which in turn stimulate smooth muscle hypertrophy. also stimulate CNS pathways that trigger increased mucus production Eosinophils: responsible (with mast cells) for smooth muscle hypertrophy, secretion of Major Basic Protein is associated with epithelial cell damage

Question 28

True or false: In pts with long-term asthma, ariway remodeling may occur. This results in chronic airflow obstruction (COPD). Usually the airway remodeling occurs when severe asthma is not well controlled (over a long period of time).

Answer 28

True.

Question 29

What structures are considered to be a part the respiratory portion (gas exchange portion) of the respiratory system?

Answer 29

Respiratory bronchioles Alveolar ducts Alveoli Capillaries

Question 30

What are _respiratory_ bronchioles composed of? What cell types exist in respiratory bronchioles?

Answer 30

Have a wall that is comprised of both conducting system elements and respiratory elements -- i.e. they contain at least 1 alveolus. Have a cuboidal epithelium with smooth muscle in conducting areas and alveoli in gas exchange areas. Also have clara cells. Regular bronchioles only have conducting system portions.

Question 31

What are alveolar ducts?

Answer 31

Question 32

What is an alveolar sac?

Answer 32

Question 33

Exchange of CO2 and O2 occurs between alveoli (air space) and capillaries (blood space). What cells and other structures form the barrier btwn air and blood?

Answer 33

Type I pneumocytes: only constitute a small fraction of the alveolar cell population but occupy most of the surface since they are large extremely thin pancake shaped squamous cells. They form a critically important interface for gas exchange. These cells also have energy-dependent membrane associated pumps that are important in transport and normal removal of vascular exudates or fluid that would otherwise accumulate in the alveolar compartment and compromise respiratory exchange. Type II pneumocytes: are about twice as abundant at Type I cells, but occupy only about 5% of the surface area. These cells can sometimes be ID'd by their more rounded appearance (LM) and by the presence of lamellar bodies (EM). They have two very important functions. Type II cells contain _lamellar bodies_ which are the source of a choline derived phospholipid that is secreted onto the surface of the alveolus. This surface active agent called surfactant, reduces surface tension and prevents collapse of the alveolar spaces. Since Type I cells cannot divide when they are damaged or die, the Type II cells provide a precursor population that proliferates and differentiates to replace Type I cells. This normal process of alveolar cell turnover can be altered in disease. Alveolar macrophages (dust cells): sit on top of the alveolar wall. They scavenge particulate matter, virus, and bacteria. Normally these cells migrate upwards in the bronchial system where they are swept out in the mucous layer. They may also leave alveoli to enter interstitial spaces and form black deposits in the septae and at the pleural surface. Capillary endothelial cells: like Type 1 Pneumocytes, also have flattened nuclei and can sometimes be identified by the profile of a capillary or a red blood cell. Most definitive way to ID is with EM.

Question 34

Answer 34

Question 35

Question 36

What is the definition of emphysema? In emphysema, what changes occur to alveoli? (as seen in attached pic). What events lead to these changes?

Answer 36

Emphysema: loss of gas exhcnage, but not due to airway blockage as in asthma. Macrophages secrete factors that stimulate eoisinophils which release proteases and elastases. Proteases and elastases degrade the alveolar wall and reduces surface area for gas exchange. Reason why COPD pts have hard time breathing. Proteolysis of CT fibers leads to the opening of the alveolar walls and subsequent rearrangement of the cell layers and greatly expanded alveolar sacs with little elasticity. (see pg 24 of course notes)

Question 37

What is the tissue repair response that results in alveolar damage in emphysema pts?

Answer 37

Tissue repair response involves excessive CT formation which results in fibrosis. Space btwn capillaries and air becomes larger: decreased diffusion.

Question 38