Lec 15/16 - Respiratory System Flashcards
whats in the upper vs lower resp tract
upper = nasal cavities, sinuses, pharynx
lower = trachea, bronchi, lungs
two functional componenets and what is included in them
conduction portion:
-nasal cavities
-sinuses
-pharynx
-larynx
-trachea
-bronchi
-bronchioles
-terminal bronchioles
respiratory portion:
-respiratory bronchioles
-alveolar ducts
-alveoli
three principal functions and other functions
air conduction
* passage across olfactory mucosa in nasal cavity carries stimuli for smell
* passage through larynx used for vocalization
air filtration
* occurs in nasal passages & lungs
gas exchange (respiration)
* occurs in the alveoli of lungs
Other Functions:
- thermoregulation; acid-base balance; metabolism; protection; communication, etc.
layers and details of the resp tract
Mucosa/Submucosa
* epithelium varies by location
- pseudostratified ciliated with goblet cells
- simple columnar with cilia
- simple cuboidal
* lamina propria/submucosa (combined)
- irregular CT with elastic fibers
- serous or mucous glands
- sometimes venous sinuses (enlarged venules); lymphoid tissue
* cartilage/bone with perichondrium or periosteum
- bone for sinuses/turbinates (chonchae)
- elsewhere, cartilagenous rings & plates
Muscularis: smooth muscle; complete layers or just a few cells
Adventitia/Serosa: variable depending on location
how is air conditioned in the conducting portion, what does the nasal cavity projection, why is there increased surface area
conducting portion of respiratory system conditions air:
* warmed: by vascular plexus & moistened by mucous & serous glands
* filtered: particles removed by hairs & mucus
* immune response: to inhaled
antigens and microorganisms (e.g. pharyngeal tonsil)
* nasal cavity has projecting turbinate bones (also known as conchae)
* increased surface area, blood sinuses for ‘air conditioning’
vestibule, resp mucosa, olfactory mucosa; type of epithelium and what is present
Vestibule
* transition from integument to nasal epithelium
* stratified squamous keratinized epithelium
Respiratory mucosa
* most of the nasal cavity
* respiratory epithelium: ciliated pseudostratified columnar epithelium with goblet cells
Olfactory mucosa
* olfactory epithelium: very tall ciliated pseudostratified columnar
epithelium with bipolar neurons no goblet cells
respiratory epithelium; classification of epith, abundant cells, other cells present, functions
- pseudostratified columnar epithelium with several cell types; all
contact basal lamina/basement membrane - ciliated columnar cells most abundant; hundreds of long cilia on
apical surface - small rounded/pyramidal cells at basement membrane are mostly
stem cells (~30% of cells) - columnar cells (brush cells) with small apical surfaces bearing tuft
of short, blunt microvilli: sensory? - mucus-secreting goblet cells
- intraepithelial lymphocytes & dendritic cells also present in
respiratory epithelium: immune surveillance
olfactory epithelium; where is it, what does the epithelium contain, secretions, flow
- patch of epithelium at top of nasal cavity associated with sense of smell
- pseudostratified columnar epithelium contains:
-bipolar neurons with long sensory cilia
-columnar epithelial supporting cells
-basal cells - neuron fibres pierce skull through
cribiform plate to reach olfactory bulb (cranial nerve I) - basal/stem cells replace both olfactory neurons (every 2-3 months) and epithelial support cells
- serous olfactory glands secrete watery product to dissolve olfactory molecules
- continuous flow of secretions washes older odors away
larynx; where is it, epithelium, interconnections, vocal sounds
- short air passage between pharynx and trachea; lined with stratified squamous or respiratory epithelium
- rigid wall reinforced by hyaline cartilage and smaller elastic cartilages (e.g. epiglottis)
- laryngeal cartilages interconnected by ligaments
- vocal folds or ‘cords’ covered by stratified squamous epithelium
- movement of cartilages by striated
volcalis muscle (VM) responsible for vocal sounds
trachea; what makes up the bronchial tree, where is it located, bifurcation
- bronchiole tree consists of trachea, bronchi & bronchioles
- passageways conducting, conditioning & distributing air into lungs
- generally similar plan with cartilage
components to keep airways open - trachea largest component, located in mediastinum
- extends from larynx to bifurcation
point where gives rise to paired primary bronchi - supported by C-shaped hyaline cartilage rings stacked along length
- smooth muscle & fibroelastic CT bridges gap between ends of cartilage
trachea histology, layers
Mucosa/Submucosa
* respiratory epithelium
* lamina propria of loose/elastic CT
* seromucous glands producing watery mucus
Muscularis
* smooth muscle of trachealis muscle
(Cartilagenous layer with perichondrium)
Adventitia
bronchial tree - dividing, lung lobe division
- trachea divides into two primary
bronchi that enter each lung at the hilum, along with arteries, veins and
lymphatic vessels - primary bronchi branch into several secondary bronchi; each supplies one lung lobe
- secondary bronchi branch into tertiary and then into smaller bronchi within each lung lobe
- lung lobes divided into multiple segments, each with bronchus, blood supply & CT septum
bronchus histology; why is there folding, what is discontinous, glands
- respiratory epithelium & mucosa folded due to contraction of smooth
muscle - wall surrounded by discontinuous plates of hyaline cartilage
- contains seromucous glands in submucosa which drain into the lumen
bronchus wall; epithelium, lamina propria contains, whats in the submucosa and adventitia, what directly surrounds the adventitia
- epithelial lining of pseudostratified ciliated columnar cells; a few goblet cells
- lamina propria contains distinct layer of smooth muscle surrounding entire bronchus
- submucosa site of supporting cartilage
- adventitia includes blood vessels & nerves
- lung tissue directly surrounds adventitia of bronchi
- in smaller bronchi epithelium is primarily columnar cells with cilia
- fewer goblet cells
- lamina propria has both smooth muscle & small serous glands near cartilage
bronchioles; what are they, what does it contain and epithelium in each
- bronchioles are airways with small diameters (~1 mm or less)
- they have no mucosal glands or cartilage
- dense connective tissue associated with smooth muscle
- large bronchioles: ciliated pseudostratified columnar epithelium
- small bronchioles: ciliated simple columnar epithelium
- smallest (terminal) bronchioles: ciliated simple cuboidal epithelium
terminal bronchioles; last part of what, layers, cells
- terminal bronchioles: last parts of air conducting system before the sites of gas exchange
- only one or two layers of smooth muscle surrounded by connective tissue
- epithelial layer contains ciliated cuboidal cells and many low columnar nonciliated cells: Club cells
club cells; other name, characterized by what, functions
Club cells (Clara cells) are also called
exocrine bronchiolar cells
* characterized by non-ciliated, dome-
shaped apical regions with secretory
granules
Functions:
* secretion of surfactant components,
cytokines, anti-inflammatory peptides & anti-microbial lysozymes
* detoxification of inhaled xenobiotic
compounds by cytochrome p450 enzymes of SER
mucocilliary clearance (escalator); where does it begin, what is it important for, action
- begins at ciliated epithelial lining of bronchioles & continues upward
- important for clearing debris & mucus by upward movement along bronchial tree & trachea
- similar action sweeps mucus & debris down from nasopharynx
what is the respiratory portion involved in, what is it characterized by, acinus, alveolar ducts, alveolar sacs
Respiratory portion involved in:
* exchange of O 2/CO 2
* removal of particles
* immune defense
* control of air flow- regulates
inspiration & expiration
Characterized by alveoli:
* sacs with extremely thin walls containing mostly blood vessels
* lined by a simple squamous
epithelium = sites of gas exchange
- terminal bronchiole begins functional respiratory unit called acinus
- within acinus, terminal bronchiole subdivides into two or more
respiratory bronchioles with occasional alveoli in walls - alveolar ducts are at distal end of respiratory bronchiole; consist of linear series of alveoli, each with smooth muscle fibers around the opening
- alveolar duct ends at terminal alveolar sac, surrounded by alveoli it supplies
resp bronchiole; what gives rise to it, epithelium, muscle
-longitudinal section through terminal bronchiole (B) giving rise to respiratory bronchioles (RB) with alveoli in their walls cross section through respiratory bronchiole with alveoli (a) opening into wall of RB
- respiratory bronchioles still have a layer of smooth muscle
- primarily simple cuboidal epithelium (and simple squamous epithelium in connected alveoli)
alveolar ducts and sacs; what does each consist of, where do alveoli open into
- alveolar ducts (AD) consist of linear series of alveoli, each with smooth
muscle fibers around opening - end in two or more
alveolar sacs (AS) - individual alveoli (A) all open either to the alveolar sacs or alveolar ducts
alveoli - what are they, function, how are alveolar air spaces separated
- small, rounded pouches that open on one side to a respiratory bronchiole, alveolar duct, or alveolar sac
- alveolar function is exchange of O2
contained from air inside them with the CO 2 contained in blood carried by surrounding capillaries (C) - alveoli air spaces separated from one another by alveolar septa (septal walls)
- neighbouring alveoli interconnected by alveolar pores: balance air pressure
- septal walls contain continuous
capillaries, macrophages, fibroblasts covered by alveolar epithelium
alveolar epithelium; vulnerable interface between what, formed by what cell types, cell % and their function
- alveolar epithelium is vulnerable biological interphase between air & blood: exposed to destabilizing forces, inhaled particles, pathogens & toxins
Formed by two cell types:
Type I alveolar cells (type I pneumocytes):
* 40 % of alveolar epithelial cells; cover 95 % of alveolar surface
* thin squamous cells joined by occluding junctions; barrier function
* incapable of cell division.
Type II alveolar cells (type II pneumocytes or septal cells):
* 60 % of the alveolar epithelial cells; cover only 5 % of alveolar surface.
* cuboidal cells that bulge into air space; protective & stem cell function (similar to Club cells)
* apical cytoplasm filled with typical granules known as lamellar bodies, contain surfactant
blood air barrier; other name, components, gas exchange
- also called respiratory membrane; three-component layer that separates air in alveoli from capillary blood
Components of the barrier:
a) single layer of type I cells lining the alveolus
b) basal lamina of these cells and of the capillary endothelial cells; sometimes fused
c) thin continuous (non-fenestrated) endothelial cells of the capillaries
Gas exchange:
* O 2 from alveolar air diffuses through the blood-air barrier
* H 2CO 3 inside erythrocytes is converted to CO 2 in lung capillaries
* CO 2 diffuses to the air inside the alveoli & is exhaled
type 2 cells; what are they, what do they do, formed by what, secreted by what, facilitates respiration by what
- complex lipoprotein surface agent that lines alveolar interior
- reduces surface tension and prevents luminal adhesion should wall of the airway collapse on itself, particularly during expiration
- formed by combination of phospholipids, neutral lipids & proteins
- secreted by alveolar type II cells via exocytosis of specific storage granules called lamellar bodies
- facilitates respiration by:
- preventing alveolar collapse at exhalation
- permitting alveolar inflation with less inspiration force
- modulates alveolar immune response
alveolar macrophages (dust cells); derived from what, present where, function, migration
derived from the blood monocytes (mononuclear phagocytic system)
* present in both connective tissue of septum and air space of alveolus
* phagocytize inhaled particles (dust, pollen, silica, carbon, etc.) in air space
* most migrate to bronchioles, are carried up by the mucociliary apparatus and disposed of by swallowing at the pharynx
* some macrophages may remain in septal connective tissue for a lifetime as septal macrophages
pleural membranes; serous layers, epithelium, facilitates what
- serous layers that cover internal wall of thoracic cavity (parietal pleura) and outer surface of lung (visceral pleura)
- simple squamous epithelium (mesothelial cells) on thin layer of CT
containing collagen & elastin fibers - pleural cavity lies between parietal and visceral pleura
- both surfaces (lung and thoracic wall) covered by thin layer of serous fluid; facilitates sliding of surfaces during respiration
pulmonary circulation in the lung; what happens here
Supplies alveoli; for gas exchange:
* enters lung O 2-depleted and leaves O 2-rich
* arteries/arterioles run parallel to bronchial tree:
- starts with branches of pulmonary artery that leave right ventricle
- arterioles branch into capillaries (blood-air barrier) at level of alveolar
duct
* blood collected by alveolar venules,
then veins, then returned to left atrium
bronchial circulation in the lung; what does it supply, blood, branching, drainage
Supplies lung tissue other than alveoli
* carries systemic, nutrient- rich blood
* bronchial arteries branch from aorta
* bronchial arterioles drain into pulmonary capillaries at junction between conducting & respiratory passages
* most blood from bronchial circulation leaves lung via pulmonary circulation, rather than in bronchial veins
control of lung function; nerve supply, ventilation … where they are found, what they include and do
Nerve Supply
* usually found in connective tissue surrounding larger elements of bronchial tree
* both parasympathetic and sympathetic autonomic fibers;
regulate smooth muscle contraction in bronchial tree (air flow)
* visceral afferent fibers also present- pain sensation
Ventilation
* involuntary control of respiration is central (CNS)
* based on levels of arterial blood gasses
- aortic & carotid bodies sense partial pressure of blood O 2
- regions in brainstem sense pH and partial pressure of CSF CO 2 (reflective of arterial blood CO 2 levels)
* this information is carried to respiratory centres in brain, coordinated & then efferent signals sent to diaphragm and intercostal muscles
