Respiratory System Flashcards
what does the respiratory tract originate from embryologically
as outgrowth of GI tract
what is the respiratory system derived from in the GI tract
laryngeotracheal groove
where does the respiratory system develop from and when
along ventral midline of posterior pharynx at the 4th week of development -> develops into respiratory diverticulum, an outgrowth of the esophagus -> grows and interacts with surrounding mesoderm
what is the primary function of the respiratory system
air conduction, filtration and gas exchange
what are the secondary functions of respiratory system
oflaction in nasal cavity and phonation from larynx
what is respiration divided into
mechanical respiration and cellular respiration
what is mechanical respiration
associated with the lungs and functions in gas exchange
what is cellular respiration
O2 is carried to the tissues for cellular respiration (oxidative metabolism -> ATP/energy
what is the diaphragm
thin, dome shaped muscle, separates thoracic cavity from abdominal cavity in mammals
what happens in inspiration
intercostal muscles contract, raise ribs; diaphragm contacts (lowers) which increases intrathoracic volume and causes negative pressure in thorax
what happens in expiration
intercostal muscles relax, lower ribs
-diaphragm relaxes (raises) which decreases intrathoracic volume and increases intrathoracic pressure
what are pleural cavities lined by
simple, squamous to cuboidal mesothelium that overlays thin layer of connective tissue containing elastic fibers
what layers make up the pleura
mesothelium and CT layer
what does the parietal pleura line
thoracic wall
what does the visceral pleura line
outer surfaces of lung
what separates the visceral and parietal pleura and what is its function
pleural space containing pleural fluid which acts as lubricant to decrease friction
what does the pleural space contain that assists with inspiration
a partial vacuum that results in negative intrathoracic pressure
what is a pneumothorax
breach of pleural space
what does a pneumothorax cause
- positive intrathoracic pressure, difficulty breathing from collapsed lung
how does the pneumothorax remain unilateral
due to mediastinum which is a loose CT layer separating L and R hemithoraces
where does air enter the upper respiratory tract
at nostrils which open into the vestibule
what does the vestibule contain
hairs to help filter and trap particulate matter
what are vibrissae
“sinus hairs”
-the hair follicle is surrounded by a blood-filled sinus
- large sensory hairs (whiskers) in cats and dogs
where does the air go after the nares and vestibule
nasal cavity
what does the nasal cavity contain
thin, scroll shaped bones called nasal turbinates/conchae
what are nasal turbinates/conchae lined with
moist, pseudostratified columbar epithelium covered by mucous
what receptors does the nasal cavity contain
olfactory receptors
what do olfactory receptors synapse with
olfactory nerve (CN I)
what do olfactory epithelium contain
small number of brush cells
what are brush cells and what is their function
- columnar cells with apical microvilli
-function: generalized sensory cells of olfactory and respiratory epithelia
where does air travel after the nasal cavity
paranasal sinuses and nasopharynx
what do paranasal sinuses do
filter, humidify, and warm inspired air
what does the nasopharynx connect to and how
middle ear via auditory (eustacian) tubes
what do auditory (eustacian) tubes do
allows equilibrium of air pressure
what is the entire upper respiratory tract lined by
pseudostratified ciliated columnar epithelium with numerous goblet cells
- aka “respiratory epithelium”
what is respiratory epithelium supported by
underlying lamina propria of loose CT
what glands does the upper respiratory tract contain
sero-mucus glands
what is the mucociliary ladder
cilia in respiratory epithelium of trachea and bronchi synchronously beat in metachronal rhythm
what is the purpose of the metachronal rhythm in the mucociliary ladder
moves surface mucus towards larynx at a rate of ~1 cm/min
what triggers the sneeze reflex
irritation to upper airways (nasal passages)
what triggers the cough reflex
irritation to lower airways (trachea and bronchi)
where does the lower respiratory tract begin
at larynx
where does the digestive system intersect with respiratory system
where upper and lower respiratory tracts meet at larynx
where is the opening of the esophagus
directly behind the trachea
what is the function of the epiglottis
protects trachea during swallowing by covering the opening of the larynx
what is a tracheostomy
sharp object in jugular/suprasternal notch
what are the 3 single cartilages in the larynx
thyroid, cricoid, and epiglottic
what are the 3 paired cartilages in the larynx
arytenoid, corniculate, and cuneiform
what cartilages make up the larynx
hyaline or elastic
where are the false and true vocal cords located
below glottis and covered by epiglottis
where are false vocal cords located
superior and lateral
where are true vocal cords locatedd
inferior and medial
what are the functions of vocal cords
- speech
- vocal folds protect lower respiratory tract from entry of foreign bodies
what are false vocal cords covered by
respiratory epithelium with seromucus glands
what are epiglottis and true vocal cords covered by
stratified squamous nonkeratinized epithelium
what does the true vocal cords contain
vocalis muscle and ligament
what do the larynx and epiglottis develop from
the 4th and 6th pharyngeal pouches
what is the larynx innervated by
branches of the vagus nerve
what innervates the portion of the larynx derived from the 4th arch
superior laryngeal nerve
what innervates the portion of the larynx derived from the 6th arch
recurrent laryngeal nerve
what is inferior to the larynx
the trachea
what lines the trachea
respiratory epithelium with numerous goblet cells and seromucus glands
what is the trachea supported by
C-shaped rings of hyaline cartilage that face caudally to facilitate swallowing
what do caudal openings contain
connective tissue membrane and smooth muscle, trachealis muscle
how do the bronchi divide after the trachea
primary bronchi -> secondary bronchi -> tertiary bronchi
what are the other names for primary, secondary, and tertiary bronchi?
primary - mainstem
secondary - lobar
tertiary - segmental
how do you identify bronchi
presence or absence of cartilage rings or plates and accompanying layer of smooth muscle with or without seromucus glands
what does cartilage provide support for
larynx, trachea, and bronchi to prevent collapse during inspiration
where does cartilage become absent in bronchi
beyond tertiary bronchi
what are all bronchi lined with
respiratory epithelium with goblet cells and submucosal seromucus glands
what is the anatomical dead space
air in upper respiratory tract, trachea and bronchi not used for gas exchange
what is the size of the anatomical dead space
about 150 mL
what is the order of bronchioles
tertiary bronchi -> bronchioles -> terminal bronchioles -> respiratory bronchioles -> alveolar ducts -> alveolar sacs/alveoli
where is the site for gas exchange
alveoli
describe what makes up bronchioles
lacks cartilage and seromucus glands; smooth muscles performs support function instead
what is the trend as bronchioles get smaller
thinning of epithelium with loss of goblet cells
what is the epithelium of terminal bronchioles
tall, pseudostratified ciliated columnar epithelium
what is the epithelium of respiratory bronchioles
simple, cuboidal to columnar ciliated and non-ciliated epithelium with occasional alveoli
where does gas exchange begin
at the level of respiratory bronchioles
what do alveolar ducts contain
numerous alveoli lined with simple squamous epithelium
where are clara cells located
in terminal and respiratory bronchioles, they replace goblet cells
describe clara cells
non-ciliated dome-shaped cuboidal to columnar cells
what do clara cells produce
lipoproteins, primary components of surfactant within airways
what surfactant do
prevents sticking together of bronchiole walls
what do clara cells do
function as reserve stem cells capable of differentiation into other respiratory cells following damage
where are K cells located
scattered throughout respiratory tract
what is the function of K cells
secrete various GI hormones
what are K cells
historical remnants of evolutionary origins from gut
what are brush cells
generalized sensory cells (columnar with apical microvilli)
what are MALT
throughout respiratory tract lymphoid aggregates - BALT or MALT
where is MALT found
in lamina propria
what is the lamina propria
layer of subepithelial connective tissue
what is the primary function of MALT
to secrete IgA onto mucosal surface to provide protection from micro-organisms
what is deep to mucosa
smooth smooth muscle layer called muscularis mucosae
where are muscularis mucosae prominent
smaller airway of respiratory bronchioles and alveolar ducts as alveolar rings
what is the function of alveolar rings
controls luminal diameter of airways and resistance to airflow, regulates alveolar air movement, takes over support function of cartilage
what are alveolar ducts and alveoli lined by
simple squamous epithelium
what are alveoli
thin- walled structures surrounded by rich capillary network supplied by pulmonary artery
what are alveolar septa
walls between alveoli
what do septa contain
alveolar pores
what are type 1 pneumocytes
flattened epithelial cells modified for gas exchange
what covers 95% if alveolar surface area
simple squamous epithelium consisting of type 1 pneumocytes
what is the air blood barrier
2 cell layers that separate air within alveolus from blood
what does the air blood barrier consist of
type 1 pneumocytes of alveoli
- endothelial cells lining capillaries and shared, fused BM
what are type 2 pneumocytes
larger, rounded dome-shaped cells
what can type 2 cells differentiate into
type 1 cells
what do type 2 pneumocytes posses
intracytoplasmic granules, called lamellar bodies containing phospholipid
what do type 2 pneumocytes secrete and what does it do
surfactant which decreases surface tension and keeps cells moist for gas exchange
what is the cause of respiratory distress syndrome in premature infants
lack of surfactant
what are dust cells and where are they located
throughout lungs they are alveolar macrophages
what do dust cells do
phagocytize particulate matter and microorganisms
how often are dust cells eliminated and how
eliminated from lung at rate of ~50 million/day via mucocilliary ladder
how is lymph drained from alveoli
no direct drainage, only indirect via interstitium of interalveolar septa
what drains the pleural space
second system of pleural lymphatic within visceral pleura
what can lymphatic obstruction lead to
pleural effusion or pulmonary edema
what is pleural effusion vs pulmonary edema?
pleural effusion- fluid within pleural space
pulmonary edema- fluid within alveoli of lungs
what is common with pneumonia
pleural effusion and pulmonary edema
what is a pneumonia
bacterial and or viral infection of lung with increased inflammatory cell infiltrate (especially neutrophils and macrophages)
what do infections associated with pneumonia cause
decreased production of pleural fluid -> damage to pleura (pleurisy)
what are connective tissue tags
adhesions between visceral and parietal pleura
what is anthracosis
originally seen in coal miners from inhaling anthracite coal dust, now common in urban environments
what is silicosis
from inhlaed silica particles primary source, coal dust and asbesots
how does silicosis occur
sharp crystals, difficult to phagocytose -> pulmonary fibrosis due to accumulation of silicic acid in lungs which stimulates fibroblast proliferation and collagen production
what causes mesothelioma
asbestos inhalation
what is tuberculosis
formation of multifocal nodules or tubercles
- bacterial foci surrounded by inflammatory cells, especially macrophages walled off by fibrotic capsule
what happens in the lungs in response to smoking
mucus production increased -> smokers hack
- cilia lose synchronicity then die
what is bronchitis
fibrosis, thickening of airways
what is metaplasia
replacement of one tissue type by another
what is the metaplasia that occurs with smoking
pseudostratified ciliated columbar epithelium of URT replaced by stratified squamous epithelium
what can metaplasia in the lungs be incited by
physical trauma (chronic coughing), chemical, or thermal insult (smoking)
what can metaplasia be the first step in
neoplasia (cancer)
what is emphysema characterized by
permanent enlargement of alveoli -> bulla formation
what is emphysema caused by
chronic obstruction of air flow -> destruction of alveolar septa and decreased surface area for gas exchange
what is emphysema initiated by
chronic inhalation of smoke and particulate matter (dust, smoke), mucus accumulation -> destruction of alveolar wall
what is the destruction of alveolar wall due to
release of lysosomal enzymes from neutrophils and macrohpages
what is COPD
bronchitis, asthma and emphysema
what is asthma characterized by
chronic airway obstruction, inflammation or irritation and increased responsiveness -> exaggerated bronchoconstriction
what is asthma initiated by
formation of antigen-antibody complexes on cell membranes, requires phagocytosis
what cells are present in large numbers in submucosa in asthmatics
mast cells and eosinophils
what does irritation in asthma cause
mast cells to release histamine and SRS that causes smooth muscel contraction of bronchioles and vasodilation ->acute asthma attack
how do eosinophils counteract effects of histamine
with histaminase and eosinophil derived inhibitor that inhibits mast cell degranulation
