Prac 7 CVRS - Respiratory Tract Flashcards
How can the tract be divided
The tract can be divided into
1 conducting airways where the air is filtered, warmed and humidified and
2 alveolar sacs where gaseous exchange takes place.
Most of the conducting airways are lined by a
ciliated respiratory epithelium
air sacs are lined
by a thin squamous epithelium composed mainly of Type I pneumocytes.
The conducting airways are lined by a respiratory epithelium. This includes
This includes the nose, nasopharynx, larynx. trachea, bronchi and bronchioles. No significant gaseous exchange takes place in these parts of the tract.
What does the resp epithelium consist of
The epithelium consists of a simple or pseudo-stratified columnar ciliated epithelium punctuated by mucus-secreting goblet cells.
It also contains non-ciliated (basal and intermediate cells) that probably represent a stem cell population important for the renewal of the epithelium. Also present are neuro-endocrine cells that are particularly numerous in the smaller bronchi. These play and important part in monitoring the inspired air for allergens and other potentially harmful elements.
Purpose of neuroendocrine cells in resp epithelium
These play and important part in monitoring the inspired air for allergens and other potentially harmful elements.
The underlying connective tissue often contains
a rich plexus of thin-walled blood vessels that help to warm the incoming air and additional sero-mucous (mixed) glands that secrete via ducts adding to the protective mucous layer that covers the surface.
rich plexus of thin-walled blood vessels help to
warm the incoming air
sero-mucous (mixed) glands do what
secrete via ducts adding to the protective mucous layer that covers the surface.
protective mucous layer does what
This mucus prevents dehydration of the epithelium and traps particulate matter that is removed from the system by the beating of the cilia. The cilia beat towards the throat and contaminated mucous is swallowed or expectorated.
The cilia beat towards
the throat and contaminated mucous is swallowed or expectorated.
Except at its opening (covered by hairy skin), the nose is lined by
simple ciliated respiratory epithelium.
Three bony projections extend from the lateral walls of nose (concha) and these too are covered by
respiratory epithelium.
what epithelium lines the nasal sinuses
respiratory epithelium.
what lies deep to the epithelium in the nose
A rich plexus of thin-walled arterioles and venules
source of many nose bleeds. Purpose of these
A rich plexus of thin-walled arterioles and venules lie deep to the epithelium (swell bodies).
They help to warm and humidify the inspired air.
A small area of epithelium about the size of a 1 pence piece is adapted for the detection of odours. It is located
in the roof of the nose below the cribriform plate.
Unmyelinated olfactory nerves pass
from the epithelium through holes in the cribriform plate to the olfactory bulbs of the brain.
he columnar pseudostratified epithelium of the olfactory mucosa consists of
basal and sustentacular (supporting) cells
Embedded within the olfactory basal and sustentacular (supporting) cells
are bipolar neurones whose dendritic processes reach the surface of the epithelium.
Deep to the epithelium are serous glands whose ducts open
on to the epithelial surface to produce a watery secretion
The watery secretion that serous glands produce acts as
solvent for odorous substances. They also irrigate the surface and help to refresh the epithelium.
Olfactory epithelium is
The epithelium is a pseudostratified columnar epithelium.
Immotile stereocilia protrude from the surface of
olfactory epithelium
Most of the cells in olfactory epithelium are supporting cells but between them
sensory cells capable of detecting odours
The basal cells contain
pigment granules
The larynx is lined by
respiratory epithelium
The larynx is lined by a respiratory epithelium except for
the vocal folds that are covered by a stratified squamous epithelium
why are the vocal folds are covered by a stratified squamous epithelium
This type of epithelium is more robust, is accustomed to wear and can withstand the vibrations of the folds.
what do the vocal chords contain and whats it called
The folds contain the free upper margin of a cone of elastic tissue (conus elasticus)
what This cone is tensioned by
the voluntary (skeletal) muscle fibres of the vocalis muscle.
Further manipulation of the folds is undertaken by
the extrinsic muscles of the larynx including the crico-thyroid muscle.
The larynx contains several plates of
hyaline cartilage and a complex arrangment of striated muscles embedded in fibrous connective tissue.
The trachea is lined by
seudo-stratified cilated epithelium (respiratory epithelium).
It is held open by
12-15 incomplete (‘C’ shaped) rings of hyaline cartilage.
The ends of the ‘C’ lie posteriorly, towards the oesophagus and are joined by
an involuntary smooth muscle (trachealis muscle).
Deep to the epithelium are
are numerous sero-mucous (mixed) glands and lymph nodules.
Bronchi are lined by
pseudostratified cilated epithelium (respiratory epithelium).
the bronchi are held open by
an external framework of hyaline cartilage. This often appears as isolated islands of cartilage in thin section but these are part of a network of interconnecting meshwork of struts.
A band of smooth muscle underlies the epithelium in the
bronchi
MALT
mucosa associated lymph tissue
bronchi Lymph nodules that are part of MALT (mucosa associated lymph tissue) lie in the
underlying connective tissue close to the epithelium.
Bronchioles divide repeatedly and are typically less than 1 mm in diameter. They are lined by
a simple ciliated epithelium (respiratory epithelium).
Are bronchioles supported by hyaline cartilage
They are not supported by hyaline cartilage but display a prominent band of smooth muscle in their wall.
Where do lymph nodules lie in bronchioles
Lymph nodules lie in the underlying connective tissue.
The conducting system of the lungs (bronchial tree) ends with
small diameter terminal bronchioles.
Terminal bronchioles are lines y and include what cells
a simple cuboidal epithelium that is only sparsely ciliated. But it includes Clara cells whose precise role remains unresolved.
What surrounds the airway at the terminal bronchioles and is able to regulate the ventilation of the alveoli distal to it.
A prominent sphincter-like ring of smooth muscle
respiratory bronchioles. These are lined by
similar epithelium to terminal, but these bronchioles are usually larger in diameter than terminal ones. They mark the beginning of the respiratory portion of the lung.
Alveoli account for most of the volume of the lung. They consist of
delicate air-filled sacks, the walls which are a delicate nextwork of blood capillaries sandwiched between the simple squamous epithelia that line the air sacks themselves.
The simple squamous epithelium of alveoli is composed of extremely thin
Type I cells and globular Type II cells
The Type I pneumoctyes cells cover
cover most of the surface
Type II pneumoctyes are distributed
at intervals around the magins
What do Type II pneumoctyes do
synthesize and secrete surfactant that spreads out over the whole lining of the air sacs and facilitates inflation of the air sacs during inspiration
Embedded within the alveolar walls are fibroblasts that produce
a framework of reticulin (collagen III) and substantial amounts of elastic tissue that is important for the elastic recoil of the lungs during exhalation.
About 70% of the surface area of the alveolar sacs is less than 1 micrometre thick (between air sac and capillary lumen) allowing
rapid diffusion of gases across this air blood barrier (see later). Elsewhere cell nuclei and connective tissue elements add to the thickness of the walls of the aveoli.
Adjoining alveoli that arise from the same terminal bronchiole are interconnected by
pores that ensure equal inflation.
Macrophages have black specks have
engulfed carbon particles
How thick is the air blood barrier
0.2 and 0.6 micrometres thick
The barrier consists of a flattened
Type I cell (pneumocyte) on the alveolar side
and a flattened capillary endothelial cell on the capillary side.
What two cells are fused to an intervening basement membrane
Type I cell (pneumocyte) on the alveolar side and a flattened capillary endothelial cell on the capillary side.
The surface of the Type I pneumocytes is covered by a thin layer
lipid-rich surfactant that is synthesized and secreted by the Type II cells.
Oxygen and carbon dioxide diffuse across five layers:
(i) surfactant,
(ii) alveolar cell,
(iii) basement membrane,
(iv) capillary endothelium
(v) red cell membrane.
Type II pneumocytes are
globular cells that are interspersed with the flattened Type I pneumocytes of the alveolar wall.
What does evidence suggest about Type II pneumocytes
Evidence suggests that they are stem cells from which Type I pneumocytes arise.
purpose Type II pneumocytes
They synthesise, store and secrete surfactant, a phospholipid-based secretion that spreads out over the whole lining of the alveolus.
Why do Type II pneumocytes secrete surfactant, a phospholipid-based secretion that spreads out over the whole lining of the alveolus.
. It reduces surface tension within the alveolus, facilitating expansion and collapse of the air sacs during respiration.
It also helps to prevent desiccation of the air sacs by forming a lipid-like insulating layer over the surface of the alveolus.
Macrophages roam freely within the alveoli doing what
phagocytosing particulate material and cell debris.
macrophages differentiate from
monocytes that migrate from the blood stream.
Other resident macrophages remain within the substance of the lung and
engulf material that penetrates the alveolar wall.
Large pulmonary blood vessels accompany the bronchi. Many are indistinguishable from their systemic counterparts. However large pulmonary arteries have
longitudinally running elastic fibres in their walls
Large pulmonary veins often have a clearly defined medial layer consisting of
muscle and elastic fibres and a well marked internal elastic lamina.
Smaller pulmonary veins that accompany the bronchioles are difficult to distinguish from their equivalent arteries since they often have
similar amounts of smooth muscle in their walls probably due to the fact that the pressure in pulmonary arteries and veins is very similar.
What lines the bronchi
Resp epthlium
The alveoli are lined by
pneumocytes.
The nares are lined by
stratified squamous keratinising epithelium
The vocal cords are lined by
non-keratinising stratified squamous epithelium.
The apex of the nasopharynx is lined by
olfactory epithelium.
What type of tissue holds open the larynx and trachea?
The larynx and trachea are supported by hyaline cartilage (present as C-rings in the trachea). This holds the airways open against negative pressure during inspiration.
What tissue bridges the gap between the free ends of C-shapedcartilages in the trachea?
Between the free ends of the hyaline cartilaginous rings in the trachea there is a smooth muscle called trachealis.
what is present within the walls of bronchi but not bronchioles?
Bronchioles are small conducting airways. They have similar histological features, but bronchioles do not contain cartilage within their walls.
Where is Reinke’s space?
Reinke’s space is occupied by the loose irregular fibrous tissue in the vocal cords
Reinke’s space lies between the vocal epithelium and the vocal ligament. Beneath that is the vocalis muscle
Which cells secrete surfactant?
Type II pneumocytes
Goblet cells produce what
mucus`
Clara cells secrete what
lipoproteins that prevent luminal adhesion
Type 1 pneumocytes form what
the air/blood barrier.
How many cell layers are there in the air blood barrier?
Two: type 1 pneumocyte (T1P) and vascular endothelial cell (VEC).
How thick is the air-blood barrier?
only 600-800 nm!
Where are the pores of Kohn?
Pores of Kohn are small (1-12 μm) holes in the walls of alveoli, connecting adjacent alveoli to each other. They allow rapid even distribution of air through the lung on inhalation, but they also permit microbes passage from one alveolus to another, and this can result in lobar pneumonia.
