Histology of Respiratory System

Question 1

T/F: mucosa includes lamina/tunica propria

Answer 1

TRUE: mucosa (mucous membranes) include adjacent connective tissue

lamina propria is relatively loose connective tissue with abundant vessels/nerves/lymphatic vessels

Question 2

T/F: MALT can be just a small group of lymphocytes or a developed lymphatic nodule complete with a germinal center

Answer 2

TRUE: mucosal associated lymphoid tissue can be small group of lymphocytes/plasma cells/neutrophils or developed lymphatic nodule with germinal center

Question 3

what makes up the conduction portion of the respiratory system?

Answer 3

conduction portion: no gas exchange, warms/moistens inspired air

nasal cavity —> nasopharynx —> pharynx —> larynx —> trachea —> primary, secondary, tertiary (segmental) bronchi —> terminal bronchioles

Question 4

what makes up the respiratory portion of the respiratory system?

Answer 4

respiratory portion: where gas exchange occurs

respiratory bronchioles —> alveolar ducts —> alveolar sacs —> alveoli

Question 5

the nasal cavity warms/moistens inspired air by passing it over the _____

Answer 5

nasal conchae (turbinate bones)

Question 6

what type of epithelium is found in the mucosa of the nasal cavity?

Answer 6

pseudostratified columnar with goblet cells and cilia (“respiratory epithelium”)

lamina propria is highly vascular (think of how easy it is to get a nose bleed!) - “swell body”

Question 7

what nerves (3) are found in the nasal cavity?

Answer 7

1. olfactory bulb/nerve
2. ophthalmic division of trigeminal
3. maxillary division of trigeminal

Question 8

olfactory receptor cells are ____ neurons with ciliated dendritic processes that are bathed in serous secretion from ________ in the lamina propria

Answer 8

olfactory receptor cells are BIPOLAR neurons with ciliated dendritic processes that are bathed in serous secretion from BOWMAN’s GLANDS in the lamina propria

Question 9

how do olfactory receptor cells become depolarized?

Answer 9

olfactory receptor cells: bipolar neurons with ciliated dendritic processes (bathed by Bowman’s glands)

odor molecules dissolve in serous fluid, bind to odorant binding proteins which trigger GPCR on the cilia —> adenyl cyclase-cAMP pathway causes ion channels to open —> depolarization

axons carry impulse to olfactory nerves and on to CNS

Question 10

after olfactory receptor cells (bipolar neurons) are depolarized, what do the axons have to traverse to reach the olfactory bulb? (in order)

Answer 10

1. olfactory epithelium
2. ethmoid bone
3. dura mater
4. arachnoid mater
5. pia mater

Question 11

what is the role of sustentacular cells in olfactory mucosa?

Answer 11

sustentacular cells: nourish olfactory receptor cells

*note that basal cells (stem cells) replace both receptor cells and sustentacular cells

Question 12

what are the key differences between the respiratory epithelium of the nasal cavity and the olfactory mucosa?

Answer 12

respiratory epithelium - contains goblet cells

olfactory mucosa - contains sustentacular cells and receptor cells, thicker

Question 13

what are the 3 layers found in both the trachea and bronchi?

Answer 13

1. mucosa (respiratory epithelium + lamina propria): abundant BALT
2. submucosa: serous and mucous glands
3. adventitia: hyaline cartilage and smooth muscle

Question 14

explain why patients with cystic fibrosis cannot clear mucus

Answer 14

mutation in CFTR (cystic fibrosis transmembrane regulator) —> cannot excrete chloride (component of salt) —> water is not attracted to cell surface —> mucus is too sticky to be cleared by mucociliary escalator

Question 15

DNES cells in the respiratory epithelium do what?

Answer 15

DNES cells (diffuse neuroendocrine system cells), aka small granule cells or Kulchitsky cells/ K cells

secrete neuropeptides and vasoactive substances into lamina propria

Question 16

what is different histologically about the pulmonary arteries relative to other arteries?

Answer 16

relatively thin wall

Question 17

where are Clara cells found and what do they do (3)?

Answer 17

Clara cells: dome-shaped, non-ciliated cells in the smallest bronchioles

secrete lipoprotein to reduce surface tension in the airways, metabolize foreign materials, serve as stem cells

Question 18

how does the epithelium change from terminal bronchioles to respiratory bronchioles, the first element to participate in gas exchange?

Answer 18

transition from ciliated cells to Clara cells

Question 19

Type I vs Type II pneumocytes

Answer 19

Type I pneumocytes (95%): squamous cells, gas exchange, joined by tight junctions

Type II pneumocytes: dome shaped, lamellar bodies contain surfactant

Question 20

what is the blood-air barrier in the lungs composed of (3)?

Answer 20

1. type I pneumocytes
2. continuous capillary endothelium
3. shared basement membrane

Question 21

what causes respiratory distress syndrome in premature infants?

Answer 21

aka Hyaline Membrane Disease

premature infants do not have enough mature Type II pneumocytes - too little surfactant hinders respiratory function

Question 22

disease characterized by destruction of tissue distal to the terminal bronchioles

Answer 22

emphysema

elastic fibers esp. affected

(tissue distal to terminal bronchioles is beginning of respiratory portion)

Question 23

what causes airways to collapse during expiration in emphysema?

Answer 23

low level of alpha1-antitrypsin function or elastase (produced by neutrophils) overproduction —> connective tissue damage

small bronchioles/alveoli not supported, pressure changes during expiration cause collapse (obstructive disease)

Question 24

how does lung tissue with emphysema appear histologically?

Answer 24

larggggggge huuuugggeee spaces between alveoli

just lots of air, can’t stress it enough