Embryology nose and paranasal sinuses
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Dec 06, 2010
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About This Presentation
This presentation discusses embryology of nose and paranasal sinuses
Slide Content
Embryology
of Nose & PNS
of Nose & PNS
Olfactory placode
a Nasal cavity is first
seen as nasal
placode in the 4"
week of IU life
a This is thickening of
ectoderm above
the stomadeum
artbalu's otolaryngology online
a Nasal cavity is first
seen as nasal
placode in the 4"
week of IU life
a This is thickening of
ectoderm above
the stomadeum
artbalu's otolaryngology online
Olfactory pit
o Olfactory placode thickens and sinks into
the mesenchymal tissue forming the
olfactory pit
o This pit lies between the proliferating
medial and lateral nasal folds of fronto
nasal process
o Olfactory pit deepens to form the nasal
sac by the 5' week of gestation
artbalu's otolaryngology online
o Olfactory placode thickens and sinks into
the mesenchymal tissue forming the
olfactory pit
o This pit lies between the proliferating
medial and lateral nasal folds of fronto
nasal process
o Olfactory pit deepens to form the nasal
sac by the 5' week of gestation
artbalu's otolaryngology online
12.5 mm embryo stage
o The maxillary process of 1% arch grows
medially and anteriorly
o Medially the maxillary processes fuse with
medial nasal folds and the fronto nasal
processes
o The nasal pits becomes a closed off to form
widely separated primitive nasal cavities
o The primitive nasal cavity and mouth are
separated by bucco nasal membrane
artbalu's otolaryngology online
o The maxillary process of 1% arch grows
medially and anteriorly
o Medially the maxillary processes fuse with
medial nasal folds and the fronto nasal
processes
o The nasal pits becomes a closed off to form
widely separated primitive nasal cavities
o The primitive nasal cavity and mouth are
separated by bucco nasal membrane
artbalu's otolaryngology online
15 mm stage
o The bucco nasal membrane thins as the
nasal sacs extend posteriorly & eventually
breaks down to form the choana
o The primitive choana is placed more
anteriorly than the definitive choana at
this stage
artbalu's otolaryngology online
o The bucco nasal membrane thins as the
nasal sacs extend posteriorly & eventually
breaks down to form the choana
o The primitive choana is placed more
anteriorly than the definitive choana at
this stage
artbalu's otolaryngology online
Premaxilla
o Floor of the nasal cavity anterior to the
primitive choana is formed by
mesenchymal extensions of medial nasal
folds
o These mesenchymal extensions give rise
to premaxilla, upper lip and medial crus of
lower lateral cartilages.
artbalu's otolaryngology online
o Floor of the nasal cavity anterior to the
primitive choana is formed by
mesenchymal extensions of medial nasal
folds
o These mesenchymal extensions give rise
to premaxilla, upper lip and medial crus of
lower lateral cartilages.
artbalu's otolaryngology online
Maxillary process
o
It develops from the dorsal
end of mandibular arch
Joins the lateral nasal fold
around the naso maxillary
groove
Ectoderm in the region of
naso maxillary groove
canalizes to form the naso
lacrimal duct
The lateral nasal fold of
fronto nasal process gives
rise to nasal bones, upper
lateral cartilages & lateral
crura of lower lateral
cartilages
o
It develops from the dorsal
end of mandibular arch
Joins the lateral nasal fold
around the naso maxillary
groove
Ectoderm in the region of
naso maxillary groove
canalizes to form the naso
lacrimal duct
The lateral nasal fold of
fronto nasal process gives
rise to nasal bones, upper
lateral cartilages & lateral
crura of lower lateral
cartilages
Nasal septum development
pedis by 13.5 mm
embryonic stage
Begins with the fusion of
maxillary and fronto nasal
processes
Midline ridge develops from
the posterior edge of fronto
nasal process in the roof of
the oral cavity
This ridge extends
ica up ie the
athke'spouch
This ridge gives rise to nasal
septum
artbalu's otolaryngology online
pedis by 13.5 mm
embryonic stage
Begins with the fusion of
maxillary and fronto nasal
processes
Midline ridge develops from
the posterior edge of fronto
nasal process in the roof of
the oral cavity
This ridge extends
ica up ie the
athke'spouch
This ridge gives rise to nasal
septum
artbalu's otolaryngology online
Development of palate
o Palate is derivedfrom lateral maxillary processes
o These processes grow medially towards each
other and the nasal septum
o Initially the palatalprocesses lie lateral to the
tongue
o Palatal processes swing medially and the fusion
starts horizontally
o Fusion begins along the posterior margin of
primitive palate
o Fusion separates the nasal from oral cavity
anteriorly
artbalu's otolaryngology online
o Palate is derivedfrom lateral maxillary processes
o These processes grow medially towards each
other and the nasal septum
o Initially the palatalprocesses lie lateral to the
tongue
o Palatal processes swing medially and the fusion
starts horizontally
o Fusion begins along the posterior margin of
primitive palate
o Fusion separates the nasal from oral cavity
anteriorly
artbalu's otolaryngology online
Vomero nasal organ
On either side of the anterior septum close to the
paraseptal Jacobson's cartilage invagination of
ectodermoccurs.
This invagination gives rise to the vomero nasal
organ
This disappears in humans leaving behind a blind
tubular pouch 2-6mm long
Jacobson's cartilage are longitudinal strips of
cartilage lying adjacent to the vomero nasal
organ on either side of the septal cartilage
They involute during later life leaving behind a
small cartilaginous bulge
dribalu's otolaryngology online
On either side of the anterior septum close to the
paraseptal Jacobson's cartilage invagination of
ectodermoccurs.
This invagination gives rise to the vomero nasal
organ
This disappears in humans leaving behind a blind
tubular pouch 2-6mm long
Jacobson's cartilage are longitudinal strips of
cartilage lying adjacent to the vomero nasal
organ on either side of the septal cartilage
They involute during later life leaving behind a
small cartilaginous bulge
dribalu's otolaryngology online
Primitive nasal septum
o The primitive nasal septum is entirely made of
cartilage
o The superior portion of this nasal septum ossifies to
form the perpendicular plate of ethmoid
o Posteriorlower portion of this cartilage ossifies to
form the vomer
© The antero inferior portion persists as the
quadrangular cartilage
o Two ossification centers appear in the region of
vomerwhich ossify to form a groove on which the
septal cartilage sits
o The primitive nasal septum is entirely made of
cartilage
o The superior portion of this nasal septum ossifies to
form the perpendicular plate of ethmoid
o Posteriorlower portion of this cartilage ossifies to
form the vomer
© The antero inferior portion persists as the
quadrangular cartilage
o Two ossification centers appear in the region of
vomerwhich ossify to form a groove on which the
septal cartilage sits
Nasal septum
Portion of nasal
septum forming
perpendicula plate of
ethmotd
Portion of nasal
septum
forming the vomer
artbalu's otolaryngology online
Portion of nasal
septum forming
perpendicula plate of
ethmotd
Portion of nasal
septum
forming the vomer
artbalu's otolaryngology online
25 weeks — 3 medial
projections from lateral
wall of nose
Diverticula occurs
between these
projections towards
the choana (forms the
meati of nose)
projections from lateral
wall of nose
Diverticula occurs
between these
projections towards
the choana (forms the
meati of nose)
Development of PNS (contd.)
o The anterior most projection - agger nasi
o Inferior maxillo turbinate projection —
Inferior turbinate & maxillary sinus
o Superior projection ethmoido turbinate —
superior turbinate, middle turbinate,
ethmoidal air cells & their drainage system
o Middle meatus develops between inferior
& middle turbinates
o The anterior most projection - agger nasi
o Inferior maxillo turbinate projection —
Inferior turbinate & maxillary sinus
o Superior projection ethmoido turbinate —
superior turbinate, middle turbinate,
ethmoidal air cells & their drainage system
o Middle meatus develops between inferior
& middle turbinates
Development of maxilla
o Maxilla develops during 6-7 weeks from 5
ossification centers
o These ossification centers give rise to alveolar,
palatine, zygomatic and frontal processes of
maxilla and the floor of orbit
o Ossification center in the medial floor of
pyriform aperture forms the premaxilla
o Premaxilla gives rise to upper incisors and
anterior nasal spine
o Maxilla develops during 6-7 weeks from 5
ossification centers
o These ossification centers give rise to alveolar,
palatine, zygomatic and frontal processes of
maxilla and the floor of orbit
o Ossification center in the medial floor of
pyriform aperture forms the premaxilla
o Premaxilla gives rise to upper incisors and
anterior nasal spine
Development of ethmoid
o Ethmoid ossifies in the cartilaginous nasal
capsule — 3 centers
o One center for each labyrinth and one for
the perpendicular plate
o These centers appear during 4-5 month of
intrauterine life
o Perpendicular plate and crista galli develop
from the same center during the 1 year of
life, fuses with the labyrinth during 2" year
artbalu's otolaryngology online
o Ethmoid ossifies in the cartilaginous nasal
capsule — 3 centers
o One center for each labyrinth and one for
the perpendicular plate
o These centers appear during 4-5 month of
intrauterine life
o Perpendicular plate and crista galli develop
from the same center during the 1 year of
life, fuses with the labyrinth during 2" year
artbalu's otolaryngology online
Development of frontal
o Develops from 2 centers - 8!" week
o Centers are present in supraciliary ridge
o At birth frontal bone - 2 halves separated
by frontal (metopic suture)
o Development completes by 8ï year
artbalu's otolaryngology online
o Develops from 2 centers - 8!" week
o Centers are present in supraciliary ridge
o At birth frontal bone - 2 halves separated
by frontal (metopic suture)
o Development completes by 8ï year
artbalu's otolaryngology online
Development of sphenoid
o Develops from presphenoidal & post
sphenoidal portions
o These portions fuse during the 8" intra uterine
month
o At birth sphenoid consists of three portions.
Central portion - body and lesser wings and
lateral portion — greater wing & pterygoid
process
o These portions fuse during the first year of life
artbalu's otolaryngology online
o Develops from presphenoidal & post
sphenoidal portions
o These portions fuse during the 8" intra uterine
month
o At birth sphenoid consists of three portions.
Central portion - body and lesser wings and
lateral portion — greater wing & pterygoid
process
o These portions fuse during the first year of life
artbalu's otolaryngology online
Pre sohenoidal portion
o Lies anterior to tuberculum sella
o Continuous with lesser wings of sohenoid
o Made of 6 ossification centers
artbalu's otolaryngology online
o Lies anterior to tuberculum sella
o Continuous with lesser wings of sohenoid
o Made of 6 ossification centers
artbalu's otolaryngology online
Post sohenoidal portion
o Composed of sella turcica and dorsum
sellae
o Gives rise to greater wings of sphenoid
and pterygoid processes
o This portion has 8 ossification centers
artbalu's otolaryngology online
o Composed of sella turcica and dorsum
sellae
o Gives rise to greater wings of sphenoid
and pterygoid processes
o This portion has 8 ossification centers
artbalu's otolaryngology online
Development of maxillary sinus
o First sinus to appear — 7
- 10 weeks
o Shallow groove
expanding from
primitive infundibulum
to the maxilla
o Enlarges by absorption
2 expansion
o Grows till 17 yrs of life
artbalu's otolaryngology online
o First sinus to appear — 7
- 10 weeks
o Shallow groove
expanding from
primitive infundibulum
to the maxilla
o Enlarges by absorption
2 expansion
o Grows till 17 yrs of life
artbalu's otolaryngology online
Development of ethmoid sinus
o Develops during 9-10 weeks of gestation
o 6-7 folds appear in the lateral wall of nasal
capsule
o These folds are separated by grooves
o These folds fuse to form 3-4 crests
o These crests have an anterior ascending
and posterior descending portions
o All ethmoidal structures develop from
these crests
o Develops during 9-10 weeks of gestation
o 6-7 folds appear in the lateral wall of nasal
capsule
o These folds are separated by grooves
o These folds fuse to form 3-4 crests
o These crests have an anterior ascending
and posterior descending portions
o All ethmoidal structures develop from
these crests
Development of ethmoid
sinuses
Ethmoid Lateral nasal wall in
development new born
sinuses
Ethmoid Lateral nasal wall in
development new born
Sphenoid sinus - Development
o Develops as evagination of spheno
ethmoidal recess - 3 IU month
o Presents as a small cavity at birth
o Reaches full size at the age of 7
o Pneumatization progresses at a rate of
0.25 mm / per year from the age of 4
o In extreme cases of Pneumatization the
optic nerve and internal carotid artery
may lie naked within the sinus cavity
o Develops as evagination of spheno
ethmoidal recess - 3 IU month
o Presents as a small cavity at birth
o Reaches full size at the age of 7
o Pneumatization progresses at a rate of
0.25 mm / per year from the age of 4
o In extreme cases of Pneumatization the
optic nerve and internal carotid artery
may lie naked within the sinus cavity
Frontal sinus - Development
o Most variable
o Erkuelpeigaly ¢ anterior
ethmoidal air cell
o Direct continuation of
infundibulum and frontal
recess
o Upward migration of
anterior ethmoidal air cells
o Remains as cul-de-sac
within the frontal bone at 2
years of age
o Most variable
o Erkuelpeigaly ¢ anterior
ethmoidal air cell
o Direct continuation of
infundibulum and frontal
recess
o Upward migration of
anterior ethmoidal air cells
o Remains as cul-de-sac
within the frontal bone at 2
years of age
Anomalies
Fusion of various process anterior — posterior
Failures of this fusion — bifid uvula to clefts of varying
degrees
Failure of fusion between maxillary processes and
premaxilla causes cleft lip
Failure of fusion between maxillary and lateral processes —
nasolacrimal furrow
Non fusion of palatine processes and septum - cleft palate
Failure of rupture of oronasal membrane - choanal atresia
Failure of olfactory placode development - complete /
partial absence of nose
artbalu's otolaryngology online
Fusion of various process anterior — posterior
Failures of this fusion — bifid uvula to clefts of varying
degrees
Failure of fusion between maxillary processes and
premaxilla causes cleft lip
Failure of fusion between maxillary and lateral processes —
nasolacrimal furrow
Non fusion of palatine processes and septum - cleft palate
Failure of rupture of oronasal membrane - choanal atresia
Failure of olfactory placode development - complete /
partial absence of nose
artbalu's otolaryngology online
Anomalies (contd)
o Unilateral maldevelopment of olfactory
placode - Proboscis lateralis
o Premature fusion of pre & post sohenoid
segments — depression of nasal bridge
(achondroplasia), hypertelorism
o Epithelial entrapment along fusion lines
causes cysts
artbalu's otolaryngology online
o Unilateral maldevelopment of olfactory
placode - Proboscis lateralis
o Premature fusion of pre & post sohenoid
segments — depression of nasal bridge
(achondroplasia), hypertelorism
o Epithelial entrapment along fusion lines
causes cysts
artbalu's otolaryngology online
Dermoid
o Commonest inclusion cyst
o It is a median lesion
o May be superficial or may communicate
intracranially via cribriform plate
o Cranial theory - As duramater recedes it pulls
the nasal ectoderm forming a sinus which later
gets pinched off to form the cyst
o Entrapment theory - Ectoderm may get
entrapped between the two median nasal folds
o Commonest inclusion cyst
o It is a median lesion
o May be superficial or may communicate
intracranially via cribriform plate
o Cranial theory - As duramater recedes it pulls
the nasal ectoderm forming a sinus which later
gets pinched off to form the cyst
o Entrapment theory - Ectoderm may get
entrapped between the two median nasal folds
Thank you
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