HSF$Histology$Lab$5:$Respiratory$System$
Introduction$
• Respiratory+system+is+divided+into:+
o Conducting+division+(warms,+moistens+and+filters+the+particulate+
matter+from+air):+
! Nose+
! Nasal+cavity+
! Nasopharynx+
! Oropharynx+(conducts+food+as+well)+
! Surface+epithelium+(respiratory+epithelium)+
! Sero@mucous+glands+
! Intrinsic+lymphoid+cells+(protect+against+airborne+infections)+
o Respiratory+division+(specialized+for+exchange+between+the+air+and+
blood):+
! Respiratory+bronchioles+
! Alveolar+ducts+
! Alveolar+sacs+
! Alveoli+
Conducting$division$
Trachea:$
• Hollow+tube+that+is+approximately+10+cm+long+
• Supported+by+multiple+C+–+shaped+cartilaginous+rings+
• Contains+pseudo+stratified+ciliated+columnar+epithelium+
• Wall+consists+of+3+layers:+
• Mucosa:+
o Luminal+surface+is+lined+by+respiratory+epithelium+which+contains:+
! Ciliated(columnar(cells:+most+numerous+and+they+take+up+the+
full+thickness+of+the+epithelium.+Their+cilia+propel+the+mucus+
towards+the+mouth+to+dispose+of+the+entrapped+foreign+
particles.+
! Muscous/goblet(cells:+interspersed+between+the+ciliated+cells+
! Brush(cells:+sensory+cells+(small+numbers+and+cannot+be+
seen+in+H/E+stain)+
! Endocrine+cells+
! Basal+cells+
o Lamina+propria+(basal+surface)+of+the+mucosa+is+vascular+loose+
connective+tissues+that+contain+elastic+fibers+and+lymphoid+cells.+
Elastic+fibers+can+be+seen+better+in+the+deeper+zone+of+the+lamina+
propria+and+they+form+an+internal+elastic+membrane+(division+
between+the+mucosa+and+submucosa)+
• Submucosa:+
o Loose+connective+tissue+
, o Has+an+abundance+of+sero@mucous+glands+that+have+serous+and+
mucous+producing+cells.+(mucous+producing+stain+more+deeply+
than+serous+producing+in+H/E+stain)+
o The+gland+secretes+into+the+ducts+that+transverse+through+the+
submucosa+and+the+mucosa+to+open+up+into+the+lumen+of+the+
trachea.++
• C+shaped+hyaline+cartilage+lines+the+trachea.+They+open+posteriorly+and+
their+open+ends+are+connected+by+fibroelastic+connective+tissue+and+bands+
of+smooth+muscle+called+the+trachealis+muscle.++
• Fibrous+adventitia+lies+exterior+to+the+cartilage.+
Duct+of+the+seromucosal+gland:+
Transverses+the+submucosa+to+
open+into+the+lumen+of+the+
trachea.+Lined+by+cuboidal+ Acinii+of+the+seromucous+
glands.+More+than+one+gland+
epithelial+cells+++
can+empty+into+a+duct++
, +
+ +
Internal+elastic+membrane+
(lowest+portion)+
Introduction$
• Respiratory+system+is+divided+into:+
o Conducting+division+(warms,+moistens+and+filters+the+particulate+
matter+from+air):+
! Nose+
! Nasal+cavity+
! Nasopharynx+
! Oropharynx+(conducts+food+as+well)+
! Surface+epithelium+(respiratory+epithelium)+
! Sero@mucous+glands+
! Intrinsic+lymphoid+cells+(protect+against+airborne+infections)+
o Respiratory+division+(specialized+for+exchange+between+the+air+and+
blood):+
! Respiratory+bronchioles+
! Alveolar+ducts+
! Alveolar+sacs+
! Alveoli+
Conducting$division$
Trachea:$
• Hollow+tube+that+is+approximately+10+cm+long+
• Supported+by+multiple+C+–+shaped+cartilaginous+rings+
• Contains+pseudo+stratified+ciliated+columnar+epithelium+
• Wall+consists+of+3+layers:+
• Mucosa:+
o Luminal+surface+is+lined+by+respiratory+epithelium+which+contains:+
! Ciliated(columnar(cells:+most+numerous+and+they+take+up+the+
full+thickness+of+the+epithelium.+Their+cilia+propel+the+mucus+
towards+the+mouth+to+dispose+of+the+entrapped+foreign+
particles.+
! Muscous/goblet(cells:+interspersed+between+the+ciliated+cells+
! Brush(cells:+sensory+cells+(small+numbers+and+cannot+be+
seen+in+H/E+stain)+
! Endocrine+cells+
! Basal+cells+
o Lamina+propria+(basal+surface)+of+the+mucosa+is+vascular+loose+
connective+tissues+that+contain+elastic+fibers+and+lymphoid+cells.+
Elastic+fibers+can+be+seen+better+in+the+deeper+zone+of+the+lamina+
propria+and+they+form+an+internal+elastic+membrane+(division+
between+the+mucosa+and+submucosa)+
• Submucosa:+
o Loose+connective+tissue+
, o Has+an+abundance+of+sero@mucous+glands+that+have+serous+and+
mucous+producing+cells.+(mucous+producing+stain+more+deeply+
than+serous+producing+in+H/E+stain)+
o The+gland+secretes+into+the+ducts+that+transverse+through+the+
submucosa+and+the+mucosa+to+open+up+into+the+lumen+of+the+
trachea.++
• C+shaped+hyaline+cartilage+lines+the+trachea.+They+open+posteriorly+and+
their+open+ends+are+connected+by+fibroelastic+connective+tissue+and+bands+
of+smooth+muscle+called+the+trachealis+muscle.++
• Fibrous+adventitia+lies+exterior+to+the+cartilage.+
Duct+of+the+seromucosal+gland:+
Transverses+the+submucosa+to+
open+into+the+lumen+of+the+
trachea.+Lined+by+cuboidal+ Acinii+of+the+seromucous+
glands.+More+than+one+gland+
epithelial+cells+++
can+empty+into+a+duct++
, +
+ +
Internal+elastic+membrane+
(lowest+portion)+
