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Histology / Embryology Unit 3 > Respiratory System > Flashcards

Respiratory System Flashcards

1
Q

What are the two divisions of the respiratory system and their components?

A
  1. Conducting (upper) - nasal cavity, nasopharynx, oropharynx, laryngopharynx, larnyx, trachea, bronchi, and bronchioles through the level of terminal bronchioles
  2. Respiratory (lower) division - respiratory bronchioles, alveolar sacs, alveolar ducts, and alveoli
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2
Q

What is the function of the conducting (upper) division of the respiratory system?

A

transmit / conduct air to lower division while warming, moistening, and removing particulate matter

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3
Q

What is the function of the respiratory (lower) division of the respiratory system?

A

Serves as site of gas exchange between air and blood

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4
Q

What is the vestibule of the nasal cavity and what are the epithelia / CT?

A

The inside of the nostrils
Epithelium - stratified squamous, slightly keratinized. Has some sebaceous glands, sweat glands, and hair follicles
Connective tissue - blends with perichondrium of nasal cartilage

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5
Q

What are the five main types of cells in respiratory epithelium? What type of epithelium is it?

A

Pseudostratified columnar

  1. Ciliated cells - beat synchronously in a posterior direction
  2. Goblet cells - produce mucus to trap particulate matter
  3. Basal cells - precursors of other cell types
  4. Neuroendocrine cells - resemble basal cells but have secretory granules. Part of amine precursor uptake and decarboxylation system
  5. Brush cells - general name for cells that bear short blunt microvilli
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6
Q

What is the significance of the lamina propria underneath the respiratory epithelium of the nasal cavity?

A
  1. Contains both mucus and serous glands for entrapment of particulate matter
  2. Contains capillary loops - thin-walled venules to warm the air
  3. Connective tissue blends with periosteum / perichondrium
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7
Q

What are capillary loops of the lamina propria for? What can they cause?

A

They are thin-walled venules which near the surface warm the air. However, they can rupture and let fluid out during upper respiratory infection

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8
Q

How does the respiratory epithelial lining in the paranasal air sinuses differ?

A

It is slightly thinner

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9
Q

Where is the olfactory mucosa of the nasal cavity found?

A

In spheno-ethmoidal recess, also extends a short distance over superior choncha and adjacent nasal septum

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10
Q

What is the structure of the olfactory epithelium? What does it lack, in comparison to respiratory epithelium.

A

Exceptionally tall pseudostratified columnar epithelium which LACKS goblet cells

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11
Q

What are the four cell types of the olfactory epithelium + their general functions / structures?

A
  1. Supporting (sustentacular) - support olfactory cells physically and metabollically. Have apical microvilli, narrow at base, broad at apex
  2. Basal cells -Mitotically active cells regenerate olfactory function in a few weeks. Small, conical cells at base
  3. Brush cells - cells with apical microvilli which function in general sensation. They are presynaptic to afferent fibers
  4. Sensory cells - bipolar neurons with cell bodies in middle layers of epithelium, between the supporting cells
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12
Q

What is the shape of olfactory sensory cells on the apical surface? Basal surface?

A

They are spindle shaped cells which an apical process / dendrite which is bulb-like, known as the olfactory vesicle or knob.

There are 10-20 modified cilia on it

Basal surface: extends into lamina propria as an axon, which continues to the olfactory bulb of the brain. Schwann cells will organize them but not ensheath them (unmyelinated)

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13
Q

How are olfactory neurons unusual?

A

They are continuously replaced, and have a 30-60 day lifespan (by basal cells)

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14
Q

How do the cilia of the olfactory vesicle / knob work?

A

They contain 350 types of odorant receptors, which have different affinities for different chemicals. All cells can detect the full range of odorants, but have varying sensitivities. Signal is transduced by G-protein-linked receptors that use second messengers

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15
Q

What are olfactory / Bowman glands? What else do they secrete?

A

Branched tubuloalveolar glands which produce a watery secretion to trap odorants and moisten / cleanse the surface (much like serous gland of von Ebner for taste buds) (via ducts)

Also secrete: Lysozyme, sIgA

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16
Q

Where are the olfactory / Bowman glands?

A

The lamina propria of the olfactory epithelium, along with the unmyelinated axons of bipolar olfactory neurons before going through cribriform plate

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17
Q

Where does the respiratory epithelium of the nasopharynx propel material?

A

Towards the oropharynx. This epithelium may be stratified in areas of abrasion

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18
Q

What is contained in the lamina propria of the nasopharynx?

A

Contains mostly mucous glands, with abundant lymphatic tissue including adenoids

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19
Q

What is squamous metaplasia and how does it relate to the larynx?

A

A change of the respiratory epithelium from pseudostratified columnar to stratified squamous epithelium. It is generally reversible but persists in areas of altered air flow (i.e. chronic bronchitis)

Larynx: areas of mechanical stress will have stratified squamous

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20
Q

How do the vocal folds differ from the vestibular folds with respect to mucosa?

A

Vocal folds are under much more mechanical stress, moving all the time for phonation, so they will be covered with stratified squamous nonkeratinized epithelium.

Vestibular folds are typically covered with pseudostratified columnar respiratory epithelium

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21
Q

What are the components in the larynx submucosa?

A
  1. Few serous and many mucous glands

2. True vocal folds contain fibroelastic connective tissue and skeletal muscle of vocalis muscle

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22
Q

What makes up the wall of the larynx?

A

Supported by hyaline + elastic cartilages, as well as connective tissue and skeletal muscle.

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23
Q

What is special about the respiratory epithelium in the trachea?

A

Has a distinct basement membrane under the epithelium

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24
Q

What can happen if the ciliated epithelium of the trachea becomes damaged / loses cilia?

A

Mucus accumulation in the lungs, since it functions to move mucus to the pharynx.

25
Q

What is the cycle of chronic bronchitis?

A
  1. Irritation causes loss of cilia.
  2. Loss of cilia forces mucus to be ejected via coughing
  3. Coughing further irritates epithelium, causing squamous metaplasia
  4. Decreased number of ciliary cells from loss of ciliary epithelium leads to further coughing and worsening of condition
26
Q

What is the function of neuroendocrine cells (also found in trachea)?

A

They are small granule cells with granules that are released into underlying connective tissue and provide local regulatory control via a wide range of neuropeptides.

Cells can be part of the APUD system and release biogenic amines like serotonin, and are visualized via silver or dichromate stains

Function is based on control of smooth muscle contraction in blood vessel walls or bronchial tree

27
Q

What defines the mucosa of the trachea? What makes its border with the submucosa?

A

Respiratory epithelium + lamina propria - separated by submucosa by band of elastic tissue

28
Q

What are the other three layers of the trachea besides the mucosa?

A
  1. Submucosa - contains mixed serous + mucous glands + lymphatics
  2. Cartilaginous layer - 20 C-shaped hyaline cartilages which open posteriorly to a bundle of smooth muscle called the trachealis
  3. Adventitia - connective tissue, blood vessel, and nerves outside the cartilages
29
Q

What connects the adjacent cartilaginous rings of the trachea?

A

Fibroelastic connective tissue which blends with their perichondrium

30
Q

What are the extrapulmonary bronchi?

A

The right and left primary bronchi - they split outside the lung and vary from the trachea only by diameter

31
Q

What are intrapulmonary bronchi?

A

Bronchi splitting within the lungs.
Secondary - 3 on right, 2 on left, supplying lobes
Tertiary - 10 on right, 8-10 on left, supplying bronchopulmonary segments

32
Q

How do the intrapulmonary bronchi differ from the extrapulmonary bronchi / trachea?

A

Epithelium - gradually changes to simple columnar
Mucosal layer has added smooth muscle called muscularis mucosae, adding patency
C-shaped cartilages are replaced by irregular plates of hyaline cartilage of decreasing size

33
Q

What are bronchioles and how many generations of branching do they have?

A

They are air passageways of 1mm or less in diameter after the intrapulmonary bronchi. They have 10 generations of branching or more

34
Q

How do bronchioles differ from intrapulmonary bronchi?

A
  • Thin walls with no hyaline cartilage and no submucosal glands
  • MORE smooth muscle (muscularis mucosa)
  • ciliated cells continue throughout but is simple columnar or even simple cuboidal
  • Goblet cells will become more and more infrequent (replaced by Clara cells)
35
Q

What do Clara cells (nonciliated bronchiolar cells) look like?

A

They are dome-shaped on apical margin, and have appearance of typical protein-secretory cells with prominent rough ER, Golgi, and secretory granules

36
Q

What are the functions of Clara cells?

A
  1. Secrete one of the components of surfactant to prevent luminal adhesion (like goblet)
  2. Synthesis of Clara cell protein (CC16), a measureable pulmonary marker
  3. Transport chloride ions into the lumen, to keep mucus watery (in CF, Cl- channel is defective and mucus becomes hyperviscous)
  4. Reserve stem cells
  5. Contain enzymes which can detoxify noxious substances
37
Q

What is a distinct feature of the lamina propria of bronchioles?

A

Contain elastic fibers to allow patency / flexibility in movement

38
Q

What is a terminal bronchiole? How many subdivisions remain?

A

The smallest branch of the conducting division - defines pulmonary lobule

Further divides into 3 generations of respiratory bronchioles and their associated alveolar ducts (all site of gas exchange)

39
Q

What is a respiratory bronchiole?

A

Smallest functional unit of lung - pulmonary acinus. It is the first site of gas exchange and thus first part of lower division of respiratory system

40
Q

What type of epithelium lines respiratory bronchioles and what can be found in them?

A

They form in groups of 2 or more from terminal bronchioles, and are lined by occasionally ciliated but mostly Clara cells. They have a few alveoli in the outpouchings (first area of gas exchange)

41
Q

What causes emphysema?

A

Neutrophils release proteases and elastases which break down the lamina propria (many elastic fibers) of pulmonary acini, leading to enlarged interalveolar spaces. This significantly decreases area available for gas exchange.

42
Q

What are alveolar ducts?

A

Thin walled tubes lined with bronchiolar cells, external wall made of fibroelastic connective tissue and surrounded by smooth muscle.

They terminate by branching into 2-4 chambers which give rise to alveolar sacs (clusters of alveoli) or single alveoli

43
Q

What are alveoli and what is found between them?

A

They are terminal air spaces of the respiratory system, and the site of gas exchange between air and blood

-Separated by interalveolar septae made of collagen, elastic, and reticular fibers

44
Q

What is the major structural element of interalveolar septae?

A

Capillaries. They structure is made of collagen and elastin, plus some reticular fibers (produced by scarce fibroblasts)

45
Q

What are alveolar pores (pores of Kohn)? What is their function?

A

Pores allowing air to pass between alveoli (in interalveolar septae), they allow for equalization of pressure between alveoli and provide collateral air circulation should a bronchiole be obstructed

46
Q

What are the two types of alveolar lining cells?

A
  1. Squamous alveolar cells - Type I alveolar cells and Type I pneumocytes
  2. Great alveolar cells - Type II alveolar cells and Type II pneumocytes
47
Q

What are squamous alveolar cells + their function?

A

Cover 95% of surface and function to form lining of alveolus. They are freely permeable to gases

48
Q

What are great alveolar cells + their functions?

A

Cover 5% of surface but are equal in number to squamous cells. They form occluding zonules with them and are continuous

Functions:

  1. Produce surfactant
  2. Proliferate into both Type I and Type II cells (squamous cells do not regenerate when damaged)
49
Q

What are multilamellar bodies / cytosomes and what is their function?

A

They are the granules rich in phospholipids, especially phosphatidylcholine, that are secreted by great alveolar cells

50
Q

What is the function of the surfactant secreted by great alveolar cells?

A

Reduces surface tension, which is essential for maintaining patency of the alveoli

Surfactant deficiency in infants causes collapse of alveoli (atelectasis), complicated by seepage of fibrin and other proteins from capillaries into air spaces, which can form a hyaline membrane

51
Q

What are the major proteins of the lung surfactant?

A
  1. Phosphatidylcholine / phospholipids (40%) - from multilamellar bodies
  2. Cholesterol (50%)
  3. Surfactant proteins 1-4 - stabilized surfactant and contribute to immune response
52
Q

What are dust cells / their functions?

A

Alveolar macrophages found in the interalveolar septum + lumen of airway. They repopulate from monocytes

Functions -

  1. Continuously produce lysosomal enzymes + phagocytose
  2. Become multinucleate giant cells to encapsulate things
53
Q

What are the two fates of dust cells?

A
  1. Migrate up respiratory tree to be swallowed

2. Re-enter connective tissue of inter-alveolar septum

54
Q

What is the alveolar membrane? What are its components?

A

The barrier for gas exchange
1. Surfactant
2. Type 1 alveolar cell
3. Basal lamina of type 1 alveolar cell
4. Basal lamina of capillary endothelial cell
(3/4 are often fused - where gas exchange occurs)
5. Capillary endothelial cell

55
Q

Where does fluid exchange occur?

A

Across portions of alveolar membrane where cells are thicker + basal lamina are not fused

56
Q

What distinguishes a bronchi from a bronchiole?

A

Bronchi have hyaline cartilage, bronchioles do not

57
Q

What distinguishes a terminal bronchiole from a respiratory bronchiole?

A

Respiratory bronchiole does not have bronchiolar epithelium, it has alveolar epithelium. You don’t know it’s a terminal bronchiole unless it is attached to a respiratory bronchiole

58
Q

What distinguishes a respiratory bronchiole from an alveolar duct?

A

Alveolar ducts come off respiratory bronchioles, and have absolutely no bronchiolar epithelium -> they are not attached to a terminal bronchiole in any way. They will branch into alveolar sacs + individual alveoli

Histology / Embryology Unit 3 (9 decks)

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