Download Respiratory System

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Divisions:
o Conducting (upper) Pathway
 Conduction requires rigidity & flexibility provided by:
 Cartilage
 Elastic fibers
 Smooth muscle fibers
 Function: transmit air to lower division while warming moistening and
removing particulate matter carried out by:
 Large blood vessels
 Goblet cells
 Extensive surface area
 Coordinated cilia beating
 Components:
 Nasal Cavity
o Vestibule – inside nostrils
 Stratified squamous keratinized (slightly)
 Some sebaceous & sweat glands
 Some hair follicles
 Underlying CT blends w/ nasal cartilage
perichondrium
o Respiratory Portion – main area
 Respiratory Epithelium = PCCG
 PCCG = characteristic of maj. of conducting pthwy
 Pseudostatified
 Columnar
 Ciliated – beat synchronously in a posterior
direction
 Goblet cells – produce & secrete mucus
which traps particulate matter (muco-ciliary
escalator system)
 Basal Cells – precursors of other cell types
 Lamina Propria
 Mucous & serous glands
 Thin-walled veins to warm air
 CT blends w/ periosteum or perichondrium
of nasal cavity
 Paranasal Sinuses
 Continuous w/nasal cavity
 Lining is slightly thinner (than nasal cavity)
o
Olfactory Mucosa – roof of nasal cavity
 Exceptionally tall Pseudostratified columnar
 LACKS goblet cells
 Four types of cells:
 Supporting (sustentacular) Cells
o Tall, cylindrical
o Broad apex, narrow base
o Apical microvilli
o Fxn: metabolic & physical support
for olfactory cells
 Sensory Cells (ciliated)
o B/w substentacular cells
o Somas in middle epithelial layer
o Spindle shaped
o Bipolar Neurons (continuously
replaced every 30-60 days)
o Apical dendrite
 Extends to surface
 Olfactory vesicle or knob
w/ 10-20 modified cilia
(nonmotile)
 Cilia > 100 types of
receptor molecules for
diff’t odors (degree of
intensity + range of odors)
 Recptors linked to Gproteins (2o messenger
inside cell—cAMP)
o Proximal cell axon
 Extends to LP to olfactory
bulb of brain
 Unmyelinated bundles by
glial ensheathing cells
 Brush Cells
o Apical microvilli
o Fxn in sensation
o Presynaptic to afferent fibers
 Basal Cells
o Only cell that does NOT touch
apical surface
o Small conical cells with dark ovoid
nuclei
o Mitotically active; able to
regenerate (few weeks)
 Lamina Propria
 Olfactory glands (or glands of Bowman)
o Branched tubuloalveolar glands
o Watery secretion
 Traps odoarants
 Moisten/cleanse surface
o Also secrete
 Lysozyme
 Secretory IgA
o Short ducts – run thru olfactory epi
 Lg. unmyelinated olfactory NN  cribiform
plate  olfactory bulb
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Nasopharynx
o Mostly PCCG (Str. Sq. in some areas of abrasion)
o Cilia propel material toward oropharynx
o LP contains glands (mostly mucous)
o Abundant lymphatic tissue (including nasopharyngeal tonsils
= adenoids)
o Muslces = pharyngeal constrictors
Oropharynx
Laryngopharynx
Larynx
o Phonation
o Respiratory conduction
o Ventricular (false vocal) folds
o True vocal folds (w/vocalis m)
o Functions
 Passageway b/w pharynx & trachea
 Swallowing – mvmts close laryngeal entrance so that
food & water cannot enter
o Walls:
 Supporting cartilages (hyaline & elastic)
 Interconnecting ligaments
 Intrinsic muscles (skeletal)
 Extrinsic muscles (skeletal)
 CT
 Mucosal lining
o Mucosa
 Abrasive areas: SSNK (vocal folds)
 Other areas: PCCG (ventricular folds)
o Submucosa
 Mostly mucous glands
 Vocal folds:
 Supporting ligament of fibroelastic CT
 Skeletal muscle (vocalis)
Trachea
o 10 cm conducting tube maintained open by cartilaginous rings
o Mucosa
 PCCG w/ distinct BM & underlying LP
 Cells:
 Ciliated columnar
 Goblet cells
 Brush cells: nonciliated columnar w/ μ-villi
 Basal cells
 Endocrine (small granule) cells – contractile
role
o Submucosa
 LCT with “mixed” glands
 Band of elastic tissue separates it from mucosa
 Lymphatic tissue
o Cartilagenous layer
 Fxn: patency (stability) of tube
 ~ 20 “c”-shaped hyaline cartilages
 “c” opens posteriorly
 “c” connected by bundles of smooth mm
 Adj. rings connected by fibroelastic CT
which blends w/ ring perichondrium
o Adventitia – external to cartilages (consists of CT, bv’s & NN)
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Bronchi: 1o (extrapulmonary)  2o (intrapulmonary)  3o (segmental)
o 10 total generations of branching
o Extrapulmonary bronchi differ from trachea only in diameter
o Intrapulmonary bronchi
 Right = 3; Left = 2
 Similar to trachea/Extrapulmonary bronchi except:
 Initially PCCG  gradually  SCCG
 Ciliated: move material up & out
 Goblet: mucous typically protective, but
excess secretion may occlude airway
 Basal & endocrine cells also present
 Mucosamuscularissubmucosa
(w/glands)cartilagenous layeradventitia
 c-shaped cartilage replaced by irregular
plates of hyaline cartilage of ↓ size
Bronchioles
o 1 mm or less in diameter
o 10 more generations of branching
o Characterized by:
 Thin walls (relative)
 No cartilage
 No submucosal glands
 More smooth muscle (relative)
o Epithelium:
 Simple columnar ciliated  simple cuboidal ciliated
 Goblet cells replaced by Clara Cells (CC)
 Clara Cells (nonciliated bronchiolar cells)
 Dome-shaped apical margin
 Typical protein-secretory cell morphology
o rER
o Golgi
o Secretory granules
 Fxn:
o Secrete substances to break down
noxious material
o Secrete component of surfactant
(prevents luminal adhesion)
o Make CC16
 Clara Cell protein
 Measurable pulmonary
marker
o Involved in Cl- transport into lumen
 Water follows
 Aids in moistening
luminal surface
 Clinical Correlation: lack
of Cl- transport is a factor
in Cystic Fibrosis
o Lamina Propria contains elastic fibers
o Muscularis Mucosa
 Increases
 Surrounded by Adventitia CT
 No glands
 No cartilage
o
o
Terminations
 Terminal Bronchiole
 Smallest branch of conducting pthwy
 Defines pulmonary lobule
 Divides into 3 generations or respiratory
bronchioles (& associated alveolar ducts)
 Respiratory Bronchiole is a termination in the
respiratory pathway (see below)
Respiratory (lower)
 Respiratory Bronchiole (pulmonary acinus)
 Smallest fxn’l unit of lung -- 1st site of gas XΔ
 Form in groups of 2 or more by terminal bronchiole division
 Cuboidal w/ mostly Clara Cells (occasionally ciliated)
 Alveoli (few) appear as dicerticula of the bronchiole
 LP contains elastic fibers
o Vulnerable to destruction by elastases & proteases
o Elasticity loss = emphysema
o CT surrounded by circumferential smooth mm layer
 Alveolar ducts, sacs & alveoli (gas XΔ b/w air & blood)
 Aveolar Ducts
o Thin-walled tubes lined w/ bronchiolar cells
o External wall
 Fibroelastic CT
 Intermittent bundles of smooth muscle
o Termination:
 Branch to 2 to 4 chambers (atria)
 Atria branch into
 Alveoli cluster = alveolar sac (double door)
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Alveoli (single door)
 Alveoli
o Termainal air space
o Site of gas XΔ b/w air & blood
 Alveolar Lining Cells (lines interalveolar septae & alveolar membrane)
o Squamous Alveolar Cells
 a.k.a. Type I alveolar cells or Type I pneumocytes
 Form lining of alveolus
 Freely permeable to gases
 Covers 95% of the surface (very thin cytoplasm)
o Great Alveolar Cells – no active role in gas XΔ
 a.k.a. Type II alveolar cells or Type II pneumocytes
 Intermingled w/ small alveolar cells & joined by O.Z.
 Same # of cells as Type I, but cover 5% of surface
 Able to proliferate & give rise to both Type I & II
 Lamellar body secretions:
 Surfactant components:
o Multilamellar bodies or (10%)
 Rich in phospholipids
 Discharged into lumen
 Fxns in surfactant system
o Choline (40%)
 Reduces tension
 Essential for maintaining
patency of alveoli
o Cholesterol (50%)
 Four Proteins (SP-A, SP-B, SP-C & SP-D)
o Stabilize surfactant/immune fxn
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Clinical Correlation
Atelactasis
o Collapsed alveoli
 Due to surfactnat
deficiency in premature
infants
 Complicated by seepage
of fibrin and other proteins
from the capillaries into
are spaces, forming a
hyaline membrane
Other Cells
o Dust Cells (alveolar macrophages)
 Highly phagoscytic
 Very motile
 Within interaveolar septum & migrating on surface
 Continuously prduce lysosomal enzymes
 Many become multinucleate giant cells
 Usually repopulate from monocytes
 Can migrate up the respiratory tree, to ultimately be
swallowed or may re-enter the CT of the interalveolar
septum
o Fibroblasts – a few in the septum produce collagenous and
elastic fibers
Interalveolar Septae (internal walls)
o Delicate CT
 Collagen
 Elastic
 Reticular fibers
o Capillaries (major structural element - scaffolding)
 2 layers of epithelium w/ BM’s
 enmeshed in elastin & fine collagen fibers
o Alveolar pores (pores of Kohn)
 Allow air to pass b/w alveoli
 Equalization of pressure b/w alveoli
 Provide collateral air circulation if another bronchiole
becomes obstructed
Alveoli Membrane (external walls)
o Gas XΔ occurs at thinnest portion:
 Surfactant
 Type I alveolar cell
 BL of Type I (sometimes fused)
 BL of capillary endothelial cell (sometimes fused)
 Capillary endothelial cell
Pleura, blood vessels & lymphatics:
o Pleura – mesothelium covering lungs
o Arteries:
 Pulmonary & bronchial arteries accompany the
branches of the bronchial tree
 Arteries give rise to capillary plexus at level of
alveolar duct
o Veins course in the septae
o Lymphatic vessels also present