S1M3 Histology of Respiratory System
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4 functions of the the Conducting System of your respiratory system?
- 1) Conduct Air: so it can reach the gas exchange area the alveoli
- 2) Condition Air: warm, moisten and remove particulate matter from the air
- 3) Produce speech from air passing through the larynx
- 4) Smell- air passing over olfactory mucosa in nose carry stimuli for sense of smell
What are the 3 parts of the Nasal Cavity?
- 1.) Vestibule
- 2.) Respiratory Segment
- 3.) Olfactory Segment
What sort of epithelium lines the vestibule of your nasal cavity?
- Stratified squamous epithelium
- CONTINUOUS with external skin of face
- Has stiff hairs called Vibrissae that entrap particulate matter
What is another name for nasal conchae and what is their FUNCTION in the vestibule of the nasal cavity?
they are three thin bony shelves, also called turbinates because the conchae act as turbines that churn the air as it passes through the nasal cavity.
Respiratory epithelium is unique, and is the epithelium for the majority of the respiratory system from the nose all the way to what level?
all the way to the Small Bronchioles!
What are the 5 cell types that make up respiratory epithelium?
- 1) Cilliated Columnar Cells (most abundant) each has 300 cilia, lots of mitochondria to provide ATP for the cilia beating
- 2) Goblet cells (secrete mucous)
- 3) Brush Cells
- 4) Basal Cells
- 5) Small Granule Cells
Respiratory epithelium is what sort of epithelium?
- Pseudostratified Columnar Epithelium!...made of 5 cell types!
- all cells touch that basal lamina, but not all touch the apical surface!
Kartagener's syndrome is?
- Also known as Immotile Cilia Syndrome
- inherited condition where all cilia lining airways fail to function
- Due to lack of dynein in cilia (sperm's flagella also affected so sterile males)Can't clear mucous, so can't clear airways and sinuses
- Promotes growth of bacteria/infection.
Brush cells are one of the five cell types of respiratory system epithelium....what is unique about them?
- Produce your COUGH reflex.
- Called Brush Cells because they have lots of microvilli on their apical surface
- Have AFFERENT nerve endings on their basal surfaces, considered sensory receptors!
What cell gives you sensation in the respiratory tract?
- Brush cells
- have afferent nerve endings on their basal surface!
Basal cells are one of the five cell types of respiratory system epithelium....what is unique about them?
They can DIFFERENTIATE into other cells types.
Small granule cells are one of the five cell types of respiratory system epithelium....what do they SECRETE?
- which controls functioning of other cells on the respiratory epithelium
warms the air that passes into the nasal cavity?
- The extensive BLOOD VESSELS under the nasal epithelium
What three cells do you find in the olfactory epithelium?
- 1) Olfactory receptor cells (neurons)
- 2) Supporting cells (sustentacular)
- 3) Basal Cells (our cells that can differentiate!)
What are three segments of your Nasal Cavity?
- 1) Vestibule
- 2) Respiratory Segment
- 3) Olfactory Segment
If you pick your nose what part of the nasal cavity are you picking at?
When you expire does air travel over your olfactory epithelium?
When you breathe in, air flows over what specialized epithelium in the nasal cavity?
olfactory epithelium which has olfactory receptor cells neurons that give you the sense of smell.
What two factors does an odorant have to have in order to be detected?
- MUST BE:
- 1) Volatile
- 2) In high enough concentration to interact with olfactory receptors.
Odor receptors can bind one or many odors?
MANY! they're permiscuous.
odor receptors are tuned to be activated by many different receptors.
Odor receptors are linked to and activate what?
Olfactory-type G proteins on inside of the olfactory receptor neuron
Purpose of basal cells in the olfactory epithelium?
to generate replacement olfactory neurons or sustentacular cells because they only last 1 month.
What is the only place where the nervous system is exposed directly to the external environment?
- olfactory receptor cells!
- bipolar neurons span the breadth of the epithelium
What's weird about the cilia on the surface of olfactory epithelium?
they are modified, they are immotile they respond to ODORS.
What is the purpose of the sustentacular cells (supporting cells) of the olfactory epithelium??
provide physical and metabolic support to olfactory cells.
_________are replicating cells that can replace both sustentacular and olfactory cells (neurons)
Bowman's glands are exclusive to what epithelium?
- olfactory epithelium!
- secrete serous fluid
What is the purpose of bowman's glands?
- a solvent to dissolve and transport odorants away from the olfactory epithelium, to get ready for a new intake of breath (new odorants)
Olfactory receptors are what type of receptors?
GPCR that act on ION channels (have 7 transmembrane domains)
Axons of your olfactory neurons synapse and excite what cells that are part of your olfactory bulb?
mitral cells which are part of the glomerulus of the olfactory bulb
How many different types of olfactory receptors do you have?
400 different kinds
What's the one weak part of your olfactory receptors?
serves as a pathway of entry to the brain from outside for certain micro-organisms
How would micro-organisms gain entry through your olfactory receptors?
Through holes in the cribriform plate of the ethmoid bone (where the olfactory nerves pass through)
brain eating amoeba Naegleria fowleri uses this pathway to gain access to the brain.
Three sections of your Pharynx?
- Superior: Nasopharynx
- Middle: Oropharynx
- Inferior: Laryngeal pharynx
The most superior portion of the pharynx, the nasopharynx, is covered by what sort of epithelium?
Inferior section of the pharynx, the laryngeal pharynx + oropharynx (middle), is covered with what sort of epithelium?
stratified squamous epithelium (toughest type of epitelium)
What is the purpose of the epiglottis?
When breathing in, it is open and permits the passage of air, but when swallowing food it is closed, so the food goes down the esophagus.
Epiglottis has a core made of what?
What is the purpose of the Larynx?
- also called the voice box
- responsible for phonation and preventing food from going down into respiratory system.
What type of cartilage makes up and reinforces the wall of the larynx?
- hyaline + elastic cartilage
What forms the cylindrical support for the larynx?
thyroid and cricoid cartilages
Two functions of the larynx?
- 1) phonation (sounds for speech)
- 2) control air flow (prevent food from entering respiratory passages.
What cells in your respiratory epithelium produce the cough reflex?
BRUSH cells which have afferent nerve endings in them and microvilli
What seperates your false vocal cords (upper) from your true vocal cords (lower)
- laryngeal ventricle
What are the two types of vocal cords?
Moveable and immovable vocal cords
- 1)false vocal cords (immovable) superior
- 2)true vocal cords (movable) inferior
seperated by the laryngeal ventricle
The vocalis muscle is attached to the vocal ligament and helps the other muscles of the larynx in doing what?
altering the tension of the vocal cords
(making the sounds for speech) the vocal folds are?
strongly adducted (pulled towards each other)
The true volcal cords consist of what?
- 1) Statified squamous epithelium
- 2) vocal ligament
- 3) vocal muscle
True vocal cords do not have what?
False vocal cords consist of what components?
- 1) Respiratory Epithelium
- 2) Lamina Propria with many exocrine glands (true vocal cords dont' have glands!
Smokers can have metaplasia of their respiratory epithelium (pseudostatified columnar epithelium). What cell type does their epithelium change to?
Stratified Squamous Epithelium
Metaplasia is what?
the reversible replacement of one differentiated cell type with another mature cells type.
(in this case we have metaplasia of the respiratory epithelium to stratified squamous epithelium in smokers)
Why does metaplasia occur in smokers?
- An abnormal stimulus (this case the cig. smoke) the normal cells aren't robust enough to withstand that environment and as a result change to simple squamous which is better suited
- The epithelium will revert back to the normal pseudostratified columnar epithelium
Dysplasia is what?
- expansion of immature cells
- decrease in number of mature cells
- indicated an early neoplastic process!
Compare metaplasia and dysplasia.
Metaplasia = one mature differentiated cell is replace with another mature cell
Dysplasia- indicates early neoplastic process, involves immature cells.
Where is the trachea found?
extends from the larynx (inferior portion of pharynx) to the begining of the two primary bronchii
The trachea is lined by what type of epithelium?
Respiratory Epithelium (pseudostratified columnar epithelium)
The trachea is made of 20 C shaped cartlaginous rings (hyaline) . The posterior open ends are connected by what?
Smooth Muscle and dense fibroelastic ligament
What is posteior to the trachea?
Why do we have the fibroelastic ligament?
- covers the open ends of the C shaped cartilage rings of our trachea and they prevent distention of the lumen
- so if we swallow a bolus of food and it expands the esophagus, this ligament allows us to accomodate this big bolus of food.
3 layers of the trachea?
- 1) Mucosa (pseudostat. with goblet cells)
- 2) Submucosa (has seromucous glands)
- 3) Adventitia (fibroelastic CT)
As we go down the bronchiole tree..... from the trachea to the primary bronchus > secondary bronchus > bronchiole > terminal bronchiole > respiratory bronchiole >alveolar duct >alveolar sac what trend do we see histologically?
- Smaller size progressively
- Decrease in the amount of cartilage
- Decrease in # of glands
- Decrease in # goblet cells
- Decrease in height of epithelium
- Increase in amount of smooth muscle & elastic tissue.
The trachea divides into two primary bronchi which enter the lung at the ?
How many secondary bronchi do you have in your right lung vs left lung?
- right lung we have 3 primary bronchi
- left lung we have 2 primary bronchi
Extrapulmonary bronchi look similar to what histologically?
Intrapulmonary bronchi (lobar) bronci have?
- have irregular plates of hyaline cartilage (instead of c rings)
- Think I = Intrapulmonary = Irregular plates of hyaline!
When do primary bronchi become intrapulmonary bronchi?
When they enter the lungs
Secondary bronchus are also know as?
Does a bronchiole have any cartilage?
NO! When the cartilage plates disappear is where the bronchioles begin.
At the point when the bronchus enters the lung (through the hilum) the cartilage rings become what?
cartilage plates that are discontinuous
When the cartilage plates of the bronchus disappear and the size of the bronchus is around 1mm what part of the lung are we in?
Sympathetic stimulation of the bronchus results in?
relaxation of the smooth muscle
Parasympathetic, vagal stimulation of the smooth muscle of the bronchus results in?
constriction of the smooth muscle of the bronchus
No cartilage in this respiratory structure. What am I?
Bronchioles are defined as?
distal airways between the cartilage walled bronchus and the site where cilliated epithelium ceases.
Do bronchioles have cartilaginous support?
they are between the cartilage walled bronchus and where the ciliated epithelium ceases.
What is the sequence from lobar (secondary) bronchus on?
bronchus > bronchiole > terminal bronchioles > respiratory bronchioles (which contain alveoli)
What bronchiole is before you get to respiratory bronchioles?
- terminal bronchiole
- wrapped in smooth muscle!
What is the last section of the conducting division of the respiratory system before you transition into the respiratory bronchioles?
When does a bronchiole become an alveolar duct?
When the bronchiole consists of only alveoli no bronchiole wall
What is the MALT of the LUNG?
Bronchus-associated lymphoid tissue
A bronchial disorder associated with airway obstruction, attacks of spasmi dyspnea whith wheezing due to spasmodic contraction of the bronchi?
What is Asthma
When you think of asthma think what?
Prolonged contraction of the smooth muscle surrounding bronchioles.
What are Clara Cells?
- Exclusive to respiratory bronchioles
- dome-shaped cells with short microvilli
- Buldge into the lumen of bronchioles!
What are the cells buldging into the middle of the lumen?
Clara cells, found in the epithelium of terminal bronchioles
**As you decrease in size (bronchus--bronchiole--terminal bronchioles) you decrease the number of cilliated cells and increase the number of CLARA cells.
As you decrease in size from bronchi to alveoli what decreases?
Decrease amount of cartilage, number of glands, goblet cells, height of epithelial cells
Increase the amount of smooth muscle, increase number of Clara cells
What are the 3 Functions of Clara Cells?
- 1) Protect bronchiolar epithelium (secrete variety of products)
- 2) Detox harmful substances, have lots of cytochrome p450s3) divide and differentiate to form cilliated and non-cilliated epithelial cells.
What two things do Clara Cells secrete?
- Clara cell secretory protein (CCSP) = surfactant
- GAGs = prevent adhesion of bad guys
have a lot of what inside of them?
to hold cytochrome p450s!
What does the Respiratory Portion of the respiratory system consist of?
- Respiratory Bronchioles (remember have more alveoli that terminal bronchioles)
- Alveolar ducts
- Alveolar sacs
What is the difference between an alveolar duct and an respiratory bronchiole?
- alveolar duct is just alveoli (totally involved in gas exchange)
- terminal bronchioles are just transition zonesboth are involved in gas exchange though!
How can you differentiate between a terminal bronchiole and a respiratory bronchiole histologically?
Respiratory bronchioles have breaks, they're interrupted by alveoli
The number of alveoli as your travel distally in a respiratory bronchiole increases or decreases?
What are the arrows pointing to?
those buldges are Clara cells!
Memorize this picture going from terminal bronchiole to alveolar sac
Do bronchioles have any cartilage support?
What sort of epithelium makes up alveolar duct?
simple squamous with smooth muscle knobs
Is there smooth muscle in the alveolar sacs (smallest + most distal)
Easy Question: Alveoli are the site of what?
what is the function of type I alveolar cells (pneumocytes)
What is the function of type II alveolar cells (pneumocytes)?
Type I alveolar cells come from?
type II cells
Do Type I alveolar cells have mitotic activity?
NO. They arise from Type II alveolar cells.
Make sure you can identify what the type I/II alveolar cells look like and what their purpose
Type II alveolar cells secrete what?
Type I alveolar cells function?
What is the purpose of the surfactant that the type II alveolar cells secrete?
- reduce surface tension at blood/air barrier preventing collapse!
- prevent the alveoli from sticking together
What if you don't produce enough pulmonary surfactant?
Can lung macrophages move?
YES, they can move btw air and liquid spaces, crawling around.
Life cycle of a Alveolar Macrophage:
- 1) begin as monocytes in bloodstream that exit through walls of pulmonary capollaries into interalveolar septa
- 2) mature and and divide in the lung and enter alveolar free space
- 3)after removing debris from alveoli move up bronchial tree where they are carried by cilia and are eventually swallowed or expectorated with mucus
What are the purpose of alveolar pores?
- also known as Pores of Kohn
- found in interalveolar septum
- EQUALIZE pressure within the alveoli
What is involved in passive expiration?
Elastic fibers of your lungs....!
Where do you need to focus your attention when you look at the alveolar section?
the walls! that's where the capillaries where gas exchange occur, elastic fibers, and the type I cells reside.
- chronic lung disease (gradual progression)
- enlargement of air space distal to bronchioles with destruction of the interaveolar wall
- decreases surface area = decreased ability absorb oxygen and exude carbon dioxide by diffusion
- Major cause is cigarette smoking
- long term lung disease usually caused by smoking
- COPD includes chronic bronchitis/emphysema
- many people have both
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