Respiratory System Flashcards
Function and composition of the Respiratory system
Respiratory system
- Provides exchange of O2 & CO2 to and from the blood
- Air is moved through the lungs by a ventilating mechanism:
- thoracic cage, intercostal muscles, diaphragm, elastic component of lung tissue
- 2 functional components:
-
Conducting portion
- provides continuous passageway for air to move in and out of the lungs
- nasal cavities, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles
-
Respiratory portion-
- system’s main function of gas exchange occurs here
- Respiratory bronchioles, alveolar ducts, alveoli
-
Conducting portion
2 components of left and right nasal cavities
2 components of left and right nasal cavities:
- external dilated Vestibule
- skin of nose, sweat glands, sebaceous glands, moist vibrissae (hairs)- filter out particulate matter from inspired air
- epithelium loses its keratinized nature and undergoes a transition to ciliated pseudostratified columnar epithelium (lines the nasal cavities)
- cilia’s base structure is axoneme which has of 9X2 microtubules + 2 pairs in the center
- cilia create current to move particles outside the respiratory tract
- Internal nasal cavities
- lie within the skull as 2 cavernous chambers
- nasal septum- separates nasal cavities
-
conchae (turbinate bones)- 3 bony shelf-like projections that extends from each lateral wall
-
superior conchae- specialized olfactory epithelium (ciliated pseudostratified columnar epithelium with bipolar receptor neurons)
- Bowman’s gland specific to this part
- middles & inferior conchae- respiratory epithelium
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superior conchae- specialized olfactory epithelium (ciliated pseudostratified columnar epithelium with bipolar receptor neurons)
- mucosa has lamina propia to condition inhaled air
- capillaries carry blood in general direction counter to the flow of inspired air & release heat toward air while it is humidified by water secreted from small seromucous glands
- Mucus produced serves to trap particulate & gaseous air impurities
- also contain IgA from plasma cells in lamina propia
Identify parts
Identify the letters
(V) vascularization of the (BM) basal lamina
(C) cilia
Mucus-secreting goblet cells (G) and
- intraepithelial lymphocytes and dendritic cells are also present in respiratory epithelium
(B) brush cells
Identify
Identify letters
Only a thin basement membrane separates the olfactory
basal cells (B) from the underlying lamina propria (LP). Nuclei
of the bipolar olfactory neurons (ON) lie in the middle of the
pseudostratified olfactory epithelium, with a zone of supporting
cell (S) nuclei above it. At the apical end of the cells
are the nonmotile cilia (C), or olfactory hairs, and a layer of
mucus (M)
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The larynx is a short air passage between the pharynx and
trachea. Its wall contains skeletal muscles and pieces of cartilage,
all of which make the larynx specialized for sound production,
or phonation.
Laryngeal vestibule (LV), which is surrounded by seromucous glands (G). The lateral walls of this region bulge as a pair of vestibular folds (VF).
These also contain seromucous glands and areolar tissue often with lymphoid nodules (L) and are largely covered by respiratory epithelium, with regions near the epiglottis having stratified squamous epithelium.
Below each large vestibular fold is a narrow space or ventricle
(V), below which is another pair of lateral folds, the vocal folds or
cords (VC). These are covered by stratified squamous epithelium
and project more sharply into the lumen. Each contains a large
striated vocalis muscle (VM) and nearer the surface a small ligament,
which is cut transversely and therefore difficult to see here.
Variable tension of these ligaments caused by the muscles produces
different sounds as air is expelled across the vocal cords. All
the structures and spaces above these folds add resonance to the
sounds, assisting phonation.
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The trachea is lined by typical respiratory epithelium (RE)
underlain by connective tissue of the lamina propria (LP) and
seromucous glands (G) in the lamina propria and submucosa.
Adjacent to the submucosa are the C-shaped rings of hyaline
cartilage (C) covered by perichondrium (P)
State histologic features of the upper respiratory tract, larynx, and trachea by indicating the types of epithelium, glands, musculoskeletal support, and other features and major function
Identify
State Features of airways within the lungs in terms of epithelium, muscle and skeletal support, and other features and major functions
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In a cross section of a large bronchus, the lining of respiratory
epithelium (E) and the mucosa are folded due to contraction of
its smooth muscle (SM). At this stage in the bronchial tree, the
wall is also surrounded by many pieces of hyaline cartilage (C)
and contains many seromucous glands (G) in the submucosa
which drain into the lumen. In the connective tissue surrounding
the bronchi can be seen arteries and veins (V), which are
also branching as smaller and smaller vessels in the approach
to the respiratory bronchioles. All bronchi are surrounded by
distinctive lung tissue (LT) showing the many empty spaces of
pulmonary alveoli.
5 major types of Respiratory Epithelium
Respiratory Epithelium
- Ciliated pseudostratified columnar epithelium that lines most of nasal cavities & conducting portion of the respiratory system
- 5 major cell types:
-
Ciliated columnar cells
- most abundant
- each with 250-300 cilia on its apical surface
-
Goblet cells
- numerous & predominant in some areas
- basal nuclei & apical domains filled with granules of mucus glycoproteins
-
Brush cells
- less numerous
- columnar cell types- small, apical surface bears sparse, blunt microvilli
- chemosensory receptors- like gustatory cells that form synaptic contact with afferent nerve endings on their basal surface
-
Small granule cells (Kulchitsky cells)
- numerous dense core granules
- part of the diffuse neruoendocrine system (DNES)
- 3% of the cells in respiratory epithelium
-
Basal cells
- mitotically active stem & progenitor cells that give rise to other epithelial cell types
-
Ciliated columnar cells
Squamous metaplasia
Squamous metaplasia
- benign noncancerous change (metaplasia) of pseudostratified ciliated columnar epithelium to stratified squamous epithelium
- can occur in the mucosa of bronchi
- immobilization of the cilia causes failure to clear mucus containing filtered material from accumulation of toxin from pollution or smoking
- can produce precancerous cell dysplasia (abnormal growth)
Olfactory epithelium
Olfactory epithelium
- where olfactory chemoreceptors for the sense of smell are located
- Ciliated pseudostratified columnar epithelium with bipolar neurons
-
Olfactory glands (of Bowman)- large serous glands in the lamina propia of the olfactory epithelium
- produce constant flow of fluid surrounding the olfactory cilia facilitating access of new odoriferous substances
- 3 major cell types:
-
Olfactory neurons
- bipolar neurons
- best neurons to be replaced regularly d/t its regenerative activity of the epithelial stem cells
- nucleus form an irregular row near the middle of the thick epithelium
- laminal-> dendrite
- cilia-> nonmotile axonemes that provide large surface area for transmembrane chemoreceptors
- process: odoriferous substance- receptors- action potential along the axon- foramina in the cribriform plate of the ethmoid bone- olfactory nerve (CN 1)- synapse with neurons in the olfactory bulb of the brain
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Supporting cells
- columnar well-developed junctional complexes
- abundant in channels that help maintain a microenvironment conducive to olfactory function & survival
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Basal cells
- small, spherical, or cone-shaped cells near the basal lamina
- stem cells for the other 2 types (replace olfactory neurons every 2-3 months & support cells less frequently
-
Olfactory neurons
Anosmia and Hyposmia
Anosmia- loss of the sense of ability to smell
Hyposmia- reduction of the ability to smell
These are caused by traumatic damage to the ethmoid bone that severs olfactory nerve axons or damage to the olfactory epithelium by intranasal drug use.
Paranasal sinuses
Paranasal sinuses
- bilateral cavities in the frontal, maxillary, ethmoid, & sphenoid bone of the skull
- lined with thinner respiratory epithelium having fewer goblet cells
- lamina propia contains only a few small glands & continuous with the underlying periosteum
- communicate with the nasal cavities through small openings
Sinusitis and Primary ciliary dyskinesia (Kartagener syndrome)
Sinusitis - inflammatory process of the sinuses d/t obstruction of the drainage orifices
Primary ciliary dyskinesia (Kartagener syndrome) - inherited genetic disorder characterized by defective ciliary action that can lead to chronic sinusitis & bronchitis
Pharynx
Pharynx
-
Nasopharynx
- 1st part of the pharynx
- Respiratory epithelium, seromucus, loose CT
-
Laryngopharynx
- 2nd part
- Nonkeratatinized stratified squmaous epithelium to protect from dessication
-
Oropharynx (throat)
- 3rd part
- Nonkeratinized stratified squamous epithelium d/t contact with food & protect from dessication
Larynx
Larynx
- short passage of air between the pharynx & the trachea
- rigid wall is reinforced hyaline cartilage (in the thyroid, cricoid, and the inferior arytenoid cartilages)
& smaller elastic cartilage (in the epiglottis, cuneiform, corniculate, and the superior arytenoid cartilages) which are connected by ligaments - movements of the cartilages by the skeletal muscles participate in sound production during phonation
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Epiglottis:
- flattened structure projections from the rim of the larynx
- serves to prevent swallowed food or fluid from entering the larynx
- Elastic cartilage
- upper surface- nonkeratinized stratified squamous epithelium transitions
- laryngeal portion- ciliated pseudostratified columnar epithelium
- mixed mucus and serous glands are found in the lamina propia beneath the epithelium
2 pairs of folds below the epiglottis
2 pairs of folds below the epiglottis:
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Vestibular folds (false vocal cords)
- upper pair
- immovable
- partly covered with respiratory epithelium overlying seromucus glands & lymphoid nodules
- not involved in
- False vocal cords has lots of seromucus phonation
-
Vocal folds (true vocal cords)
- important for phonation & sound production
- convered with nonkeratinized stratified squamous epithelium that protects from abrasion & dessication from rapid air movement
- True vocal cords has lots of skeletal muscles
- vocal ligament- dense regular bundle of elastic CT that supports the free edge of each vocal fold
- vocalis muscle- large bundles of striated fibrous deep to the mucosa which allow each vocal fold to be moved
- rima glottidis- opening between vocal cords that narrows during phonation & air from the lungs causes the adducted vocal cords to vibrate & produce sound
Laryngitis and Singer’s nodules
Laryngitis- inflammation of the larynx accompanied by edema or swelling of the organ’s lamina propia that produces hoarseness or complete loss of voice
Singer’s nodules- benign reactive polyps frequent in stratified squamous epithelium of true vocal cords affecting the voice
Trachea
Trachea
- Lined with typical respiratory mucosa (respiratory epithelium)
- lamina propia contains seromucus glands producing watery mucus
- submucosa (loose to dense CT) which house BALT (Bronchus associated lymphoid tissue)
- dozen C-shaped rings of hyaline cartilage
- adventitia (carry vessels and nerves) which reinforces the wall & keeps the tracheal lumen open
-
trachealis muscle
- bundles of smooth muscle that bridged the gap between the free ends of the C-shaped rings of cartilage at the posterior border of the trachea
- relaxes during swallowing to facilitate the passage of food by allowing the esophagus to bulge into the lumen of the trachea
- with elastic layer to prevent excessive distention of the lumen
Bronchial Tree
- Trachea divides into 2 Primary brochi
- series of aurway branches of progressively decreasing size:
- Mucosa (Respiratory epithelium, lamina propia), Smooth muscle layer, Submucosa (loose CT), Cartilage layers (hyaline cartilage that fully encircle the lumen), Adventitia (loose to dense CT)
- Primary bronchi give rise to:
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3 Secondary Lobar bronchi (Right lung)
- each supplies a pulmonary lobe
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2 Secondary Lobar bronchi (Left lung)
- each supplies a pulmonary lobe
- to make space for the heart
- Lobar bronchi form Tertiary Segmental bronchi
- bronchopulmonary segment
- 10-12% of each lung with its own CT capsule & blood supply that help facilitate surgical resection of diseased lung without affecting nearby healthy tissues
- small mucus & serous glands are abundant with ducts opening into the bronchial lumen
- spirally arranged smooth mucle & elastic fiber
- numerous lymph (lamina propia & epithelial cells)
- abundant MALT (mucosa-associated lymphoid tissue)
- Tertiary bronchi give rise to Bronchioles
- Series of smalller branches from bronchi
- Lacks mucosal glands & cartilage
- Smooth muscle helps the bronchioles open
- Ciliated pseudostratified columnar epithlelium (large bronchioles) decreases in height & complexitiy in smallest terminal bronchioles & becomes Ciliated simple columnar epithelium or Simple cuboidal epithelium
- consists of club cells (bronchioles exocrine glands or clara cells)
- nonciliated dome-shaped apical ends containing secretory granules
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functions:
- secretion of surfactant
- detoxification of inhaled xenobiotic compounds by SER enzymes
- secretion of antimicrobial peptides & cytokines for immune defense
- also contains chemosensory brush cells & DNES small granule cells
- ciliary epithelial lining of bronchioles begins the mucociliary apparatus or escalator which is important in clearing debris & mucus by moving it upward along the bronchial tree & trachea
- smooth muscle layer, adventitia
- Bronchioles enter a pulmonary lobule and branch to form 5-7 Terminal Bronchioles
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Pulmonary lobule
- pyramid-shaped
- apex aimed at the pulmonary hilum
- delineated with thin layer of CT (frequently incomplete in adults)
- Last part of air conducting system
- Simple cuboidal epithelium, club cells, smooth muscle layer, adventitia
- Terminal ducts subdivides into 2 or more Respiratory Bronchioles
- 1st part of the system’s r_espiratory region_
- smooth muscle & elastic CT comprise the lamina propia
- epithelium consists of club cells & Ciliated simple cuboidal cells with apical domelike projections at the alveolar openings & extending into the alveolus
- Distal ends of respiratory bronchioles branch into Alveolar Ducts
- completely lined by openings of alveoli
- cuboidal epithelium
- smooth muscle cells surround each alveolus opening
- network of elastic & collagen fibers support duct & alveoli
- Alveolar Sac
- clusters of alveoli
- form ends of alveolar ducts
- extremely thin lamina propia with elastic & reticular fibers
- network of capillaries surrounds each alveolus
- Alveoli
- saclike evaginations from respiratory bronchioles, alveolar ducts, & alveolar sacs
- lined with extremely attenuated squamous cells- type I pneumocytes
- has underlying CT & lamina propia
- responsible for the spongy structure of the lungs
- air in these structures exchange O2 & CO2 with blood in surrounding capillaries through thin walls for diffusion
- Interalveolar septa lie between neigboring alveoli
- O2 from alveloar air diffuse through BAB into capillary blood to bind hgb
- CO2 diffuses to alveolar air from pulmonary blood (H2CO3)
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(a) The epithelial lining (E) of bronchi is mainly pseudostratified
ciliated columnar cells with a few goblet cells. The lamina propria
(LP) contains the distinct layer of smooth muscle (SM) surrounding
the entire bronchus. The submucosa is the site of the supporting
cartilage (C) and the adventitia includes blood vessels (V) and
nerves (N). Lung tissue (LT) directly surrounds the adventitia of
bronchi.
(b) In the smaller bronchi the epithelium is primarily of columnar
cells with cilia (arrows), with fewer goblet cells. The lamina propria
has both smooth muscle (SM) and small serous glands (G) near
cartilage (C).
Identify letters
The smallest branches of the bronchial tree are the bronchioles,
which lack supporting cartilage and glands.
(a) A large bronchiole has the characteristically folded respiratory
epithelium (E) and prominent smooth muscle (arrows),
but it is supported only by fibrous connective tissue (CT).
(b) Staining for elastic fibers reveals the high elastic content of
the smooth muscle (arrowhead) associated with the muscle of
a smaller bronchiole in which the epithelium is simple columnar
but still ciliated. Darkly stained elastic fibers are also present in the
tunica media of a large arteriole (A) nearby and to a lesser extent in
the accompanying venule (V). The connective tissue includes many
lymphocytes (L) of diffuse MALT and lymphoid nodules.
(c) In very small bronchioles the epithelium (E) is reduced to simple
cuboidal cells with cilia. Several layers of smooth muscle cells
(arrows) comprise a high proportion of the wall.
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The last parts of the air conducting system before the sites of gas
exchange appear are called the terminal bronchioles.
(a) A terminal bronchiole has a mucosa with nonciliated cuboidal
or low columnar epithelium (E), surrounded by only one or two
layers of smooth muscle (SM) embedded in connective tissue
(CT). Alveoli (A) are seen in the surrounding lung tissue.
(b) Most of the epithelium consists of exocrine club cells (C) with
bulging domes of apical cytoplasm contain granules, as shown
here in a plastic section.
- These cells have several important functions. They secrete components of surfactant which reduces surface tension and helps prevent collapse of the bronchioles.
- The P450 enzyme system of their smooth ER detoxifies potentially harmful compounds in air.
- In other defensive functions the cells also produce the secretory component for the transfer of IgA into the bronchiolar lumen; lysozyme and other enzymes active against bacteria and viruses; and several cytokines that regulate local inflammatory responses.
- Also included among the cuboidal cells are stem cells that give rise to all of the cells within the bronchiolar epithelium.
Identify
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Terminal bronchioles branch into respiratory bronchioles, which
then branch further into alveolar ducts and individual alveoli.
Respiratory bronchioles are similar in most respects to terminal bronchioles except for the presence of scattered alveoli along their length.
(b) The micrograph shows the branching nature of the air passages
in two dimensions: respiratory bronchiole (RB), alveolar ducts (AD),
alveolar sacs (AS), and individual alveoli (A).
(c) SEM shows in three dimensions the relationship of a terminal
bronchiole (TB), respiratory bronchiole (RB), alveolar duct (AD),
alveolar sacs (AS), and individual alveoli (A).
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Lung tissue has a spongy structure because of the abundant air
passages and pockets called alveoli.
(a) Typical section of lung tissue includes many bronchioles,
some of which are respiratory bronchioles (RB) cut lengthwise,
and shows the branching continuity with alveolar ducts (AD) and
sacs (AS). Respiratory bronchioles still have a layer of smooth
muscle and some regions of cuboidal epithelium, but alveolar
ducts consist of a linear series of alveoli, each with smooth
muscle fibers around the opening. Individual alveoli (A) all open
to the sacs or ducts. The respiratory bronchiole runs along a
thin-walled branch of the pulmonary artery (PA), while branches
of the pulmonary vein (V) course elsewhere in the parenchyma.
(b) Higher magnification shows the relationship of the many
rounded, thin-walled alveoli (A) to alveolar ducts (AD). Alveolar
ducts end in two or more clusters of alveoli called alveolar sacs
(AS). Smooth muscle around the alveolar openings appears as
eosinophilic “knobs” between adjacent alveoli. The alveoli here
that do not show openings to the ducts or the sacs have their connections
in planes of adjacent sections.
Identify
Gas exchange between air and blood occurs at a membranous barrier between each alveolus and the capillaries surrounding it.
(a) This diagram shows the relationship between capillaries in
the interalveolar septa and the saclike alveoli. The alveolar pores
(of Kohn) allow air pressure to equilibrate and air to circulate
between alveoli on different ducts or sacs if the local airway
becomes blocked.
Identify
(b) The air-blood barrier consists of an alveolar type I cell, a capillary endothelial cell, and their fused basement membranes. Oxygen diffuses from alveolar air into capillary blood and carbon dioxide moves in the opposite direction. The inner lining of alveoli is covered by a layer of surfactant (not shown) which lowers fluid surface tension and helps prevent collapse of alveoli.
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The septa between alveoli (A) contain several cell types.
As seen here, the capillaries (C) include erythrocytes and leukocytes.
The alveoli are lined mainly by squamous type I alveolar cells (I), which line almost the entire alveolus surface and across which gas exchange occurs. Type II alveolar cells line a bit of each alveolus and are large rounded cells, often bulging into the alveolus (II).
These type II cells have many functions of club cells, including production of surfactant. Also present are alveolar macrophages (M), sometimes called dust cells, which may be in the alveoli or in the interalveolar septa.
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TEM of a capillary (C) in an interalveolar septum shows areas for gas exchange between blood and air in three alveoli (A).
The endothelium is continuous but extremely thin, and its basal lamina (B) fuses with that of the type I alveolar cells (I) and type II cells.
A fibroblast (F) can be seen in the septum, and the thickened nuclear regions of two endothelial cells (E) are also included.
The nucleus at the bottom belongs to an endothelial cell or a circulating leukocyte.
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TEM of a type II alveolar cell protruding into the alveolar lumen shows unusual lamellar bodies (L) that contain newly synthesized pulmonary surfactant after processing of its components in rough ER (RER) and the Golgi apparatus (G).
Smaller multivesicular bodies (MVB) with intralumenal vesicles are also present.
Short microvilli (M) cover the apical cell surface at the alveolus (A) lumen.
The type II cell is attached via junctional complexes (JC) to the neighboring type I cell (I).
Reticular fibers (RF) are prominent in the ECM.
Identify
Identify letters
The pleura are serous membranes (serosa) associated with each
lung and thoracic cavity.
(b) Both layers are similar histogically and consist of a simple squamous
mesothelium (M) on a thin layer of connective tissue, as shown here for visceral pleura covering alveoli (A).
The connective tissue is rich in both collagen and elastic fibers and contains both blood vessels (V) and lymphatics (L).
Interalveolar septa
Interalveolar septa
- lie between neighboring alveoli
- 2 neighboring type I pneumocytes & underlying CT of each cell
- consist of scattered fibroblasts & sparse ECM
- notable elastic & reticular fibers
- elastic fibers- enable alveoli to expand with inspiration & contract with expiration
- reticular fibers- prevent collapse & excessive distention of alveoli
- vascularized with richest capillary network in the body
- macrophages & other leukocytes can be found here
Alveolar Blood Air Barrier (BAB)
Alveolar Blood Air Barrier (BAB)
- 2 or 3 highly attenuated thin cells lining the alveoli
- fused basal lamina & endothelial cells of capillaries
- thin continuous capillary edothelial cells
Alveolar pores (of Kohn)
Alveolar pores (of Kohn)
- penetrate the interalveolar septa & connect neighboring alveoli that open to different bronchioles
- equalize air pressure in alveoli & permit collateral circulation of air if a bronchiole becomes obstructed
Type I and Type II Alveolar cells
Type I Alveolar cells
- Type I pneumocytes
- extremely attenuated cells that line the alveolar surface
- constitute the alveolar side of BAB
- make up 95% of alveolar lining
- desmosomes & tight junction help prevent leakage of tissue fluid into alveolar air space
- involve in gas exchange
Type II Alveolar cells
- Type II pneumocytes
- Septal cells
- cuboidal cells that bulge into air space intersperesed among the type I alveolar cells bound with tight junctions & desmosomes
- often occur in groups of 2 or 3
- nuclei are rounded & may have nucleoli
- lightly-stained sytoplasm with many vesicles (lamellar bodies)
-
lamellar bodies secrete lipids, phospholipids, & proteins that act as pulmonary surfactant to lower surface tension at the air-epithelium surface to prevent alveolar collapse
- DPPC, cholesterol, & Surfactant Protein-A (hydrophilic glycoprotein), SP-B (innate immune protection), SP-P & SP-C (hydrophobic membrane proteins required for proper orientation of DPPC)
-
lamellar bodies secrete lipids, phospholipids, & proteins that act as pulmonary surfactant to lower surface tension at the air-epithelium surface to prevent alveolar collapse
Pleura
Pleura
- serous membrane that covers the lung’s outer surface & internal walls of the thoracic cavity
- composed of simple squamous mesothelial cells on a thin CT layer containing collagen & elastic fibers
- visceral pleura- membrane attached to lung tissue- lymphatics and blood will be found here
- parietal peura- membrane lining the thoracic walls
- pleural cavity- entirely lined with mesothelial cells that produces a thin film of serous fluid as lubricant
Respiratory movements
Inhalation->
contraction of internal intercostal muscles->
elevation of ribs & contraction of diaphragm->
lowers bottom of thoracic cavity increasing its diameter->
pulmonary expansion->
bronchi & bronchioles increase in length & diameter->
expansion of alveolar duct->
respiratory portion enlarges:
- alveoli enlarges only slightly
- elastic fibers of of the pulmonary parenchyma are stretched
Anthracosis
Anthracosis
- Coal workers’ pneumoconiosis (CWP), also known as black lung disease or black lung, is caused by long-term exposure to coal dust.
- Inhaled coal dust progressively builds up in the lungs and leads to inflammation, fibrosis, and in worse cases, necrosis.
