Lecture/Lab: Respiratory System

Question 1

What makes up the respiratory system?

Answer 1

• Paired lungs
• A series of air passages that lead to and from the lungs
• Ventilation mechanism (diaphragm creates a low pressure environment)

Question 2

What are the 3 principle functions of the respiratory system?

Answer 2

air conduction: bringing in air from external environment
air filtration: cleans the air
gas exchange (respiration): site of gas exchange. brining O2 into your blood stream

Question 3

What is the function of serous fluid?

Answer 3

Serous fluid allows for the coupling of visceral and parietal pleurae

Result: free and rapid movement of the lung in relation to the chest wall. Able to pull the lungs open when you expand rib cage

Lubrication, not much friction as it moves

Question 4

Conducting portion

Answer 4

Structure: varying levels of wall thickness
* Location: portions outside and inside the
lung
* Function: conduct and condition
* Conducting portion has regions outside and
inside of the lung
* Outside lung:
- Nasal cavity to primary bronchi
* Inside lung:
- Bronchi
- Bronchioles
- Terminal bronchioles

Question 5

Respiratory portion

Answer 5

Structure: thin wall for efficient gas exchange
* Location: only in the lungs
* Function: gas exchange
* Includes respiratory bronchioles, alveolar
ducts and sacs

Question 6

Two types of blood circulation in the lungs

Answer 6

Pulmonary circulation and bronchial circulation

Question 7

Pulmonary circulation

Answer 7

Carrying O2-depleted blood to lungs for gas exchange - returns to heart as well oxygenated blood

Question 8

What are the vessels within the pulmonary circulation and where are they located?

Answer 8

The pulmonary arteries and veins are the
functional vessels of the respiratory system:

Pulmonary arteries
* Carry deoxygenated blood
* Travel with the branches of the bronchi and bronchioles down to the capillary level

Pulmonary veins
* Carry oxygenated blood
* Located in connective tissue septum (do NOT run with the pulmonary artery)

Usually, arteries and veins are side by side. But in the pulmonary system, arteries are adjacent to the bronchioles as it reaches the alveoli, pulmonary veins are situated away with the CT septa of lungs

Question 9

Bronchial circulation

Answer 9

Carrying oxygen rich blood to supply the tissues of the lung and airway

Bronchial circulation (nutrient arteries)
Nourish the tissues of the lung:
* Bronchial arteries are branches of the aorta
* Nourish connective tissues including the
walls of the bronchi and bronchioles, and pleura
* Found within the walls of the tissue
* Venous return of bronchial circulation can happen through the systemic system or anastomose with the pulmonary circulation

Question 10

What type of capillaries are in the lungs?

Answer 10

continuous
because it needs to be the most selective so as to not get fluid or other things in the lungs
Lungs are the largest continuous capillary bed in the body.

Question 11

What are the different materials in the RS and what so they do?

Answer 11

Cartilage
Hyaline cartilage
* C-shaped rings in trachea
* Plates become smaller at the level of the bronchi
(absent in the bronchioles)
Smooth muscle
* Regulates diameter of the airway
* Absent at the level of the alveolar sacs
Collagen fibers
* Primarily type I in upper regions
* Reticular fibers (type III) support capillary network
Elastic fibers
* Form a network that allow expansion (limited)
and recoil of the lung
* Increased in the distal aspect of the lungs

Too much collagen = not able to expand lungs
Too little elastic fibers = lungs can’t recoil = emphysema

Question 12

Nasal cavity

Answer 12

Nasal Cavity
- Bony cavity that is divided into three regions
(meatus) by turbinates (concha)
- Majority is made up of respiratory epithelium:
ciliated pseudostratified epithelium
- Small portion in the upper concha is made up of
olfactory epithelium (specialized pseudostratified
columnar epithelium)
* Olfactory sensory neurons
* Sustentacular (support) cells
* Microvillar cells
* In the lamina propria: small olfactory
(Bowman’s) glands that produce specialized
mucous

Question 13

Trachea

Answer 13

The wall of the trachea consists of the
following layers:
- Mucosa (pseudostratified epithelium, elastic rich lamina propria, no muscularis mucosae)
- Submucosa – glands present “Tracheal submucosa glands”
- Adventitia with C-shaped cartilage ring facing posteriorly

Question 14

Tracheal epithelium

Answer 14

pseudo-stratified with 5 cell types

Question 15

Ciliated cells

Answer 15

9+2 microtubules

• Maintain level of periciliary fluid in the periciliary layer (PCL) (layer of water and electrolytes)
• Forms a “mucociliary escalator” that clears mucous away from the airways (toward oral cavity; mucous can’t be too thick and inundate cilia, otherwise cilia can’t beat)

Question 16

Mucous cells

Answer 16

• Mucinogen granules in cytoplasm
• The mucus floats on a serous fluid
• Cilia moves both serous and mucus toward the oral cavity

Question 17

Brush cells

Answer 17

• Columnar cells with blunt microvilli
• Basal surface in synaptic contact with afferent nerve ending
• General sensory receptor cells

Brush cells are very difficult to observe in all but thin sections. They are recognized by their lack of cilia and mucus inclusions

Question 18

Small granule cells

Answer 18

• Difficult to distinguish in light microscopy without special techniques
• Contain secretory granules
• May function in reflexes regulating the airway or vascular diameter

Basal and small granule cells are indistinguishable from each other without special stains

Question 19

Basal cell

Answer 19

Stem cell for individual cell replacement in the epithelium

Basal and small granule cells are indistinguishable from each other without special stains

Question 20

Where and how does metaplasia happen in the RS? What pathologies are associated with metaplasia?

Answer 20

Pseudostratified respiratory epithelium changes
to stratified squamous non-keratinized
epithelium

Removal of mucous impaired

Marked increase in the size of the mucus secreting glands of the submucosa in the trachea and large bronchi

Individuals must cough to clear secretions

Pathogenesis:
Inhaled irritants such as smoking
Reversible - if irritant eliminated

Question 21

Bronchi

Answer 21

Starts at the bifurcation of trachea

The bronchus has the following layers:
- Mucosa - same epithelium, cells as trachea
- ***Muscularis - regulates diameter of airway, allows us to keep airways open
- Submucosa - glands present “BRONCHIAL SUBMUCOSA GLANDS”
- Adventitia/cartilage - plates smaller with decreasing diameter

Question 22

What changes happen as you go from the trachea to the bronchi?

Answer 22

• Plates of cartilage that become smaller toward the bronchioles
• Layer of smooth muscle (muscularis) is found immediately below the mucosa layer
• Increase in elastic fibers

Question 23

Bronchioles

Answer 23

No more cartilage

Airways that measure 1mm or less

Diameter increases/decrease with lung volume

Subdivided dependent on function:
- Terminal bronchioles - nonrespiratory (conducting airways)
- Respiratory bronchioles - function as sites of
gas exchange

Simple cuboidal epithelium

Gradual changes - no abrupt changes in this
system

From lab:
The last airway completely lined with a conducting (club cell) epithelium

Question 24

What changes happen as you go from bronchi to bronchiole?

Answer 24

changes at the level of the bronchioles:
1. Bronchioles lack cartilage
2. Bronchioles lack submucosal glands
3. Note the thick layer of smooth muscle (organized in a spiral fashion)
4. Simple cuboidal epithelium: ciliated cells decrease in number and club cells increase distally

Question 25

Club cells

Answer 25

Club cells manufacture “club cell secretory protein” that protects the epithelial lining as well as a surfactant-like substance that helps prevent collapse by reducing surface tension.
- Structure: Non-ciliated, dome-shaped apical aspect
projects into lumen
- Function: Detoxify harmful compounds in the air. Secrete a lipoprotein that prevents luminal adhesion. Mitotically active stem cell
- Location: Bronchioles

Outlined cell is a club cell. See the characteristic dome-shape apical surface and granules.

Question 26

Terminal bronchiole

Answer 26

Most distal region of the conducting portion
Club cells with some ciliated cells

Question 27

Respiratory bronchioles

Answer 27

• First region of gas exchange
• Wall is interrupted with alveoli
• Club cells (dominate) and some ciliated cells

From lab:
a passageway lined both with patches of club cell epithelium and patches of alveolar epithelium

Question 28

Alveolar duct

Answer 28

Lined by type I and type II pneumocytes (AT1 & AT2 cells)

a passageway connecting adjacent alveolar sacs. Its outline is formed by the terminations of the alveolar walls

Question 29

Alveolar sacs

Answer 29

Groups of alveoli clustered around a common air space

Epithelium: * type I pneumocyte (AT1 cells) * type II pneumocytes (AT2 cells)

the distal end of an alveolar duct, consisting of 8-12 alveoli

Question 30

Type I pneumocytes (AT1 cells)

Answer 30

Structure:
- Thin, squamous cells with occluding junctions
Function:
- Provide a barrier optimal for gas exchange
Location:
- Cover 95% of the surface area of the alveolus

Question 31

Type II pneumocytes (AT2 cell)

Answer 31

(also called septal cells)

Structure:
- Cuboidal secretory cells with apical cytoplasm that contains lamellar bodies
Location:
- Typically found at junctions and occupy 5% of the surface area
Function:
- Stem cell: type I and type II pneumocytes
- Continuously produce surfactant to prevent collapse of alveoli by reducing surface tension

Their location is most often at corners of the alveolar walls, where they can arrange themselves so as to take up the least amount of lumenal space possible.

Question 32

Interalveolar septum

Answer 32

Thin region:
- Site of air-blood barrier, gas exchange areas
- Capillaries function in gas exchange
Thick region (pulmonary interstitium)
Composed of
- Collagen and elastic fibers
- Capillaries and lymphatic vessels
- Fibroblasts and immune cells
- Macrophages

Question 33

Blood-Air Barrier (respiratory membrane)

Answer 33

Four components make up the blood air barrier:
- Thin layer of surfactant, 1st thing air comes iin contact with
- Alveolar epithelium (type I pneumocyte cytoplasm) –>thin squamous cell
- Fused basement membranes of the alveolar cell and the endothelial cell. Usually, under the basement membrane epithelium is CT. But here, you fuse the BM with the capillary underneath. Basal lamina of A1 cell is fused with the epithelial of the capillary
- Endothelial cell – specialized type for gas exchange and leukocyte diapedesis called aerocytes

Question 34

Alveolar Pores

Answer 34

(pores of Kohn)
Functions include:
- Equalizing pressure in the alveoli
- Enable collateral ventilation, so that air doesn’t go only in one alveolus
- Allow macrophage migration

Question 35

What are the two types of macrophages?

Answer 35

Alveolar macrophages and Interstitial macrophages

Question 36

Alveolar Macrophages

Answer 36

• Function in luminal and airspaces of alveoli
• Some pass up the bronchial tree in mucus to
  reach the pharynx
• Some migrate to connective tissue where they
  may stay with particles for the life of the
  individual (dust cells)
• Particles in the interstitium increase the
  likelihood of lung damage
• Less effective at stimulating an immune
  response

From lab:
Alveolar macrophages crawl along the surfactant layer by extending pseudopodia, and thus are not permanently attached to the epithelium

Question 37

Interstitial Macrophage

Answer 37

• Exist in the connective tissue
• Stimulates and coordinates with local and
  systemic immune response

Question 38

MALT/BALT

Answer 38

mucosa associated lymphoid tissue/bronchial associated lymphoid tissue.

lymphocytes in the trachea

Dense accumulations cells seen in the lamina propria and submucosa.

Though these cells are motile, they tend to congregate in areas where they are likely to encounter foreign antigen

Question 39

Alveoli

Answer 39

the terminal cup-shaped passageways of the lung, lined with alveolar epithelium

Question 40

Intrapulmonary bronchi vs extrapulmonary bronchi

Answer 40

Intrapulmonary bronchi retain some of the cartilage in their wall in the form of plates

can tell it’s intrapulmonary by looking at the alveolar tissue surrounding the bronchus

Question 41

lamellar bodies

Answer 41

The intracellular surfactant, stored in lamellar bodies, gives the AT2 a bubbly appearance that may unfortunately be sometimes similar to macrophages

producing surfactant, a material that coats the apical surface of the alveolar epithelium and reduces the surface tension for gases, allowing them to better diffuse through to and from the circulation

Question 42

Emphysema

Answer 42

Emphysema is any air-filled enlargement in the body’s tissues. Most commonly emphysema refers to the permanent enlargement of air spaces in the lungs, and is also known as pulmonary emphysema (From Google)

Too little elastic fibers = lungs can’t recoil = emphysema
(from lecture)

Key to recognizing this pathology is to note that alveoli in a normal lung are are always the same volume. A normal lung contains 100 millions of alveoli that, together with the other structures you have learned, should occupy the entire space.[2] To the extent that portions of the lung consist of larger spaces, capacity for gas exchange is lost.