Respiratory System

Question 1

What does the respiratory system do?

Answer 1

bring oxygen to blood in lungs or gills and expel CO2 from the blood

Question 2

Characteristics that make lungs able to exchange gases.

Answer 2

contains large surface area by folding and refolding upon itself; also exhibits:

steep diffusion gradient for O2 and CO2
short diffusion distances (thin walls)
high degree of vascularization
coordinated air and blood movement

Question 3

Where does diffusion of gas occur

Answer 3

across 2 layers of thin simple squamous epithelium with basal lamina

gases must be dissolved in fluid in respiratory tract to diffuse (causes water loss problems in tetrapods)

Question 4

max distance of diffusion barrier

Answer 4

2.5 microns

Question 5

respiratory structures in terrestrial, aquatic, and amphibious crawlers

Answer 5

terrestrial: lungs
aquatic: gills. In some fish buccal cavity and anterior stomach serve as accessory respiratory structures (also some fish possess lungs)

skin (cutaneous) is also a respiratory structure in amphibians (especially lungless salamanders)

Question 6

What is the respiratory “terrestrial situation”

Answer 6

bidirectional flow (expired and inspired air over some surfaces), except in birds (unidirectional crosscurrent system)

Question 7

What is the respiratory “aquatic situation”

Answer 7

water flow over gills is unidirectional countercurrent exchange= blood and water pass in opposite directions.

Question 8

Why is countercurrent exchange better than unidirectional or crosscurrent?

Answer 8

in unidirectional flow, all we can do is equilibrate the O2 concentration

when the flow is in the opposite direction, the creature can extract more than ‘equilibrium’ levels of oxygen.

Question 9

Describe the terrestrial respiratory system (basic)

Answer 9

consists of paired lungs and branching system of airways bringing air to respiratory surface for gas exchange

Question 10

Sequence the terrestrial respiratory system for mammals.

Answer 10

Nasal cavity
pharynx
larynx
trachea
bronchi
bronchial tree:
secondary bronchus
tertriary bronchus
bronchiole
terminal bronchiole
respiratory bronchiole
alveolar duct
alveolar sac
alveolus

Question 11

extrapulmonary vs intrapulmonary

Answer 11

the point where the bronchi penetrate the lungs (between primary and secondary bronchus)

Question 12

Describe the nasal cavities

Answer 12

paired, divided by nasal septum

open to outside via external (anterior) nares. open interiorly to nasopharynx via internal nares =choanae)

walls of nasal vacuities of hyaline cartilage and bone to keep them open

Question 13

3 regions of the nasal cavities

Answer 13

vestibule= lined by stratified squamous with filtering hairs, sweat and sebaceous glands present. mostly same as outside.

nasal passages: olfactory region
contains olfactory mucosa, dorsally situated (superior)

respiratory region: contains respiratory mucosa, ventrally situated.

Question 14

Describe olfactory epithelium

Answer 14

pseudo stratified columnar containing:

olfactory receptor cells
sustentacular cells
basal cells

no goblet cells present
nuclear-free border 1/5 height of epithelium
L. propria with serous bowman’s glands to rinse away stimulus molecules and dissolve incoming stimulus molecules
thicker than respiratory epithelium

Question 15

olfactory receptor cells

Answer 15

modified bipolar neurons with dendrite that extends to free surface with olfactory cilia and axons extending into lamina propria; large spherical nucleus found in middle of epithelium

Question 16

Describe respiratory epithelium

Answer 16

ciliated PSC with goblet cells

nuclear free border 1/3 of epithelial height

located ventrally in nasal cavity and lines larger respiratory tubes

Question 17

Describe nasal cavity respiratory epithelial lamina propria.

Answer 17

in nasal cavity, lamina propria composed of cavernous (erectile) tissue- swelling gives plugged nose.

l. propria also contains mucoserous glands

Question 18

Nasal conchae

Answer 18

turbinates

shelves of bone projecting medially from lateral walls of nasal cavity

covered by a mucous membrane

act to increase surface area of nasal cavity

function as countercurrent heat exchanger: exhaled air temperature is less than body temperature and therefore decrease respiratory water loss (since cold air holds less water than warm air)

Question 19

Describe the larynx

Answer 19

connects pharynx to trachea

consists of a tube supported by cartilage interconnected by dense CT and skeletal muscle; functions to guard respiratory tract from possible food entry and produces voice

Question 20

Vestibular folds

Answer 20

of mucous membrane, extend from lateral walls (false vocal cords)

they lie above and protect the vocal folds (cords) beneath.

lined by respiratory epithelium

Question 21

vocal ligaments

Answer 21

elastic fiebrs in vocal cord with skeletal muscle at core.

contraction of muscle changes tension and length of cords and opening between them, thereby creating changes in voice.

vocal folds lined by stratified squamous epithelium

Question 22

epiglottis

Answer 22

extension of anterior wall of larynx, supported by elastic cartilage plate; covers opening to larynx to keep food out

Question 23

Describe the trachea

Answer 23

Shares a large number of characteristics with lesser ducts

Contains mucosa, submucosa, fibro-cartilaginous coat (tunic) of adventitia and cartilage

Mucosa and submucosa separated by an elastic membrane

SEE HANDOUT FOR CROSS-SECTIONAL STRUCTURE OF RESPIRATORY TUBES

Question 24

5 cell types of the respiratory tract

Answer 24

ciliated columnar cells
goblet cells
basal cells
brush cells (need EM to see)
small granule cells (need EM to see)

Question 25

What is a unique feature of the primary bronchus?

Answer 25

M, mucosae is in circular configuration around bronchus

Question 26

What is a unique feature of the tertiary bronchi?

Answer 26

there are no goblet cells at this level or below.

Question 27

What is a unique feature of the bronchiole?

Answer 27

the mucosal lining is simple columnar instead of PSC

there is no cartilage in the submucosa

Question 28

What is a unique feature of the respiratory bronchiole?

Answer 28

simple columnar becoming perforated simple squamous

Question 29

What is a unique feature of the alveolar duct?

Answer 29

sphincters present as duct opens into atrium

Question 30

What is unique about the muscle of the trachea?

Answer 30

no muscular mucosa, instead the trachealis is present.

Question 31

What general trend is seen in the cartilage as you go deeper into the lungs?

Answer 31

decreases

Question 32

What’s the use of the trachealis muscle?

Answer 32

it contracts when bad things get into the trachea

results in a decreased air space to surface space ratio to increase the amount of junk that the mucous can attract.

Question 33

Describe an alveolus.

Answer 33

Terminal division of respiratory system where gas exchange occurs;

Alveoli are tightly packed, partitions (interalveolar septa) separate individual alveoli.
These septa are composed of basement membrane + delicate elastic and reticular fibers and numerous capillaries.

Question 34

What are the spaces that an alveolus can open into?

Answer 34

open into alveolar sac, atrium, alveolar duct or respiratory bronchiole.

Question 35

What type of cells line the alveoli?

Answer 35

Alveoli lined primarily by extremely flat simple squamous epithelial cells (Type 1 Pneumocytes)

part of the diffusion barrier

Question 36

alveolar-capillary barrier

Answer 36

simple squamous pneumocyte + fused basement membrane + simple squamous endothelial cell lining capillary

varies from .2-2.5 um thickness

Question 37

type 2 pneumocytes

Answer 37

scattered along alveolar walls

These are rounded cells incorporated into simple squamous epithelium.

Secrete surfactant = phospholipid film that counteracts surface tension forces on alveoli preventing their collapse on expiration.

Question 38

What cell types can be present in inter alveolar septa?

Answer 38

fibroblasts and macrophages

“septa cells”; can cross lining and get into the alveolus to clean it up