NASAL
CAVITY
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2005 zillmusom
I. NASAL
CAVITY ‑ openings ‑
anteriorly opens to Anterior Nares, posteriorly at Choanae (Posterior Nares);
cavity lined by mucoperiosteum
A.
Boundaries; each described from anterior to posterior: Floor ‑ (Atlas Fig. 7.63): composed of palatine process of maxillary
bone and horizontal plate of palatine bone; Roof ‑ nasal bone, frontal
bone, cribriform plate of ethmoid, and
body of sphenoid; Medial wall = nasal septum: septal cartilage, perpendicular plate of ethmoid bone and vomer; Lateral Wall
‑ nasal bone, maxillary bone, inferior concha and ethmoid bone, palatine
and sphenoid bone.
Note: fractures of nose are common; fractures of
cribriform plate of ethmoid (which forms roof of nasal cavity and floor of
anterior cranial fossa) can lead to meningitis or cerebrospinal fluid leakage
into nasal cavity if the dura is torn.
B. Lateral Wall (Atlas Figs. 7.63,
7.66) ‑ three projections from
lateral wall called turbinates or conchae (L. shell): These projections
increase surface area of mucosa; increase area functions warm, humidify, and clean air we breathe;
Superior and Middle conchae are part of
ethmoid; Inferior concha is a separate
bone.
Note: Opening of auditory tube in nasopharynx is
posterior to inferior concha.
1. Four Spaces of Nasal Cavity associated
with conchae, each space has its own
opening for air sinuses or nasolacrimal duct (Atlas Figs. 7.66 to 7.68).
a.
Sphenoethmoidal recess ‑ above superior concha; openings ‑ 1) olfactory
foramina of cribriform plate and 2) opening of Sphenoidal air sinus.
b. Superior
Meatus (L. passage) ‑ below superior concha; opening ‑ Posterior
Ethmoidal air sinus.
c. Middle
Meatus ‑ below middle concha; has
rounded elevation called Ethmoidal Bulla which is formed by projection
of middle ethmoidal air cells; slit
below Ethmoidal bulla is called Hiatus semilunaris; anterior part of Hiatus
semilunaris is called infundibulum; openings ‑ 1) Middle Ethmoidal
sinuses open onto upper border of Ethmoidal bulla; 2) Anterior ethmoidal sinus
and 3) Maxillary sinus open into Hiatus semilunaris; 4) Frontal sinus drains
into middle meatus via infundibulum.
Note:
maxillary sinus opening is high up on wall of sinus, can lead to poor drainage
of sinus when infected.
d. Inferior
meatus ‑ below inferior concha; opening: nasolacrimal duct
C. Divisions ‑ Respiratory
area ‑ lower part of mucosa, lined with respiratory epithelium; Olfactory
area (Atlas Fig. 7.64A) ‑ upper part of mucosa, lined with olfactory epithelium
D. Nerves (Atlas Fig. 7.64A)
1. Olfactory area ‑ Olfactory nerve (sense
of smell)
2. General sensation
(touch, temperature, etc.) ‑ branches of Anterior Ethmoidal nerve (from
V1) and Nasopalatine nerve and Nasal branches (from V2)
3. Innervation to nasal mucous glands ‑ from Pterygopalatine ganglion;
branches of facial nerve (VII) travel with trigeminal nerve (V)
E. Blood supply (Atlas Fig. 7.65A)
1. Arteries ‑
Mostly from Sphenopalatine artery (branch of Maxillary artery); also from
Anterior and Posterior Ethmoidal arteries (branches of Ophthalmic artery) and
branches of Facial artery (anteriorly).
2. Veins ‑
Ethmoidal veins drain to Ophthalmic vein; other branches to Pterygoid venous
plexus and Facial vein.
Note:
rich anastomoses in nose results in epistaxis (nosebleed) due to tearing of
veins; spurting of blood occurs from tears of arteries.
F. Lymphatics ‑ drain to
Retropharyngeal nodes.
II.
PARANASAL AIR SINUSES (Atlas Figs. 7.69, 7.68) ‑ air filled
extensions of nasal cavities; all are paired; develop after birth; lined by
mucous membrane; serve to lighten growing bones; a mistake of evolution,
because could have filled growing bones with spongy bone and would not get
infected.
A. Frontal sinus ‑ two sinuses
separated by a median septum; variable in size.
B. Sphenoid sinus ‑ paired
sinuses located in body of sphenoid bone
C. Ethmoidal sinus ‑ Anterior,
Middle, and Posterior groups;
Note:
Blocked ethmoidal sinuses may cause infection to pass laterally through thin
medial wall of orbit to infect eye.
D. Maxillary sinus ‑ largest,
occupies entire body of maxilla; Roof ‑ floor of orbit; Medial wall ‑
related to lower part nasal cavity. (Atlas Fig. 7.71)
Note:
Roots of teeth closely related to floor of sinus (Atlas Fig. 7.71); Extraction
of molar teeth can result in fracture of floor of sinus.
Note:
Anterior and Posterior
III.
PALATE
A. Development ‑ occurs during
5‑12th week (Sadler Figs. 15.21 –15.27)
1. Two parts form
palate: primary and secondary palates.
a. Primary
palate (Median palatine process) ‑ formed by union of Medial Nasal
Processes, become part of palate anterior to incisive foramen, bearing incisor
teeth
b. Secondary
palate (posterior to incisive foramen) ‑ formed of maxillary processes of
Arch I; maxillary processes fuse with the Median Palatine processes
anteriorly; posteriorly, maxillary
processes fuse with each other at midline; fusion proceeds anteriorly to
posteriorly.
2.
Malformations ‑ (Sadler Figs. 15.28 –15.29)
a. Anterior
Cleft palate ‑ improper fusion of primary and secondary palates (Medial Nasal processes and
Maxillary processes fail to fuse); cleft is anterior to incisive foramen;
1:1000 births
b. Posterior
Cleft palate ‑ improper fusion of parts of secondary palate (Maxillary processes from each side fail to fuse with
each other); cleft is posterior to incisive foramen; 1:2500 births
B. Anatomy ‑ palate forms roof of
mouth and floor of nasal cavity.
1. Hard palate ‑
formed of palatine processes of maxillary and horizontal plates of palatine
bones; tightly covered by mucoperiosteum.
2. Soft palate ‑
collection of muscles with a central aponeurosis (tendon); soft palate hangs
down from posterior end of hard palate, projecting posteriorly as uvula; soft palate elevated during swallowing to close
off oropharynx from nasopharynx
a. Palatal muscles (4) ‑ (Snell Fig. 11‑78)
|
MUSCLE |
ORIGIN |
INSERTION |
ACTION |
NERVE |
|
Tensor
Palati |
Auditory
tube (tendon wraps under hamulus of medial pterygoid plate) |
Palatine
aponeurosis |
Tenses
soft palate |
V3 |
|
Levator
Palati |
Temporal bone, Auditory tube |
Palatine
aponeurosis |
Elevates
soft palate |
X |
|
Palatoglossus |
Palatine
aponeurosis |
Side of
tongue |
Draws
soft palate down, raises tongue |
X |
|
Musculus
Uvulae |
Palatine
aponeurosis |
Uvula |
Raises
uvula |
X |
3. Blood Supply (Atlas
Fig. 7.57) ‑ Mostly from branches
of maxillary artery : Descending
Palatine artery gives off Greater and Lesser Palatine arteries, which pass to
hard and soft palate, respectively; also Ascending Palatine artery (branch of facial artery).
4. Nerves ‑
Sensory: branches of CN V2 ‑
Greater palatine and Nasopalatine nerves to hard palate; Lesser palatine nerves
to soft palate.
5. Lymph ‑ drains
to retropharyngeal nodes which drain to deep cervical nodes.
IV.
PALATINE TONSILS (Snell Fig. 11-78; Atlas Fig. 8.32) ‑ located
between palatoglossal and palatopharyngeal folds on lateral side of oropharynx;
tonsils are a collection of lymphoid tissue covered by mucous membrane; lateral
to tonsil is the tonsilar bed (lateral wall of pharynx); bed formed by superior constrictor muscle of pharynx and styloglossus
muscle.
A. Arteries ‑ mainly from
Tonsilar branch of Facial artery (Atlas Fig. 8.32B-D).
B. Veins ‑ join pharyngeal
plexus of veins which drain to Facial, Lingual or Internal Jugular veins.
Note:
Glossopharyngeal n. (Atlas Fig. 8.32E) ‑
passes forward with tonsilar artery in lateral wall of pharynx; only mucosa and
pharyngobasilar fascia cover nerve; can be damaged in tonsillectomy.
C. Lymphatics ‑ Drain to
Jugulodigastric node (one of the Deep Cervical nodes, becomes enlarged during
tonsillitis); node located near angle of mandible and inferior to posterior
belly of digastric.