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Nasal Cavity


Atlas References

  • Netter: 45–52, 61, 142

  • McMinn: 58, 59, 73

  • Gray's Atlas: 566–571

Dissection Steps

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    Exposure of the contents of the nasal cavity requires a midsagittal transection through the head ( Fig. 26.1 ).

    Fig. 26.1, Craniotomy view with dashed line for sagittal section.

Dissection Tip

Electric saws are usually too small for transection of the head. Make sure that one of your classmates holds the cadaver head firmly as you cut with the saw.

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    Place the saw as close as possible to the midline. Begin the cut externally from the face toward the midportion of the head ( Fig. 26.2 ).

    Fig. 26.2, Anterolateral view of face with previous craniotomy, demonstrating sagittal cut of nasal cavity.

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    Split the head in half, and choose one of the two halves to decapitate ( Figs. 26.3 and 26.4 ).

    Fig. 26.3, Anterior view of sagittal cut of nasal and oral cavities revealing nasal septum with left and concha on right.

    Fig. 26.4, Sagittal view of nasal and oral cavities revealing nasal bone, cartilage, concha, and openings. Structures of mouth and pharynx include hard palate, soft palate, tongue, mandible, epiglottis, and posterior pharyngeal wall.

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    Clean away soft tissues or any bony fragments after the hemisection (compare Fig. 26.4 with Fig. 26.5 ).

    Fig. 26.5, Sagittal view of nasal and oral regions. Nasal region structures include sphenoidal sinus, ethmoidal sinus (anterior, middle, and posterior cells), nasal concha, and eustachian tube opening. Oral structures include lips, hard and soft palate, tongue, oral floor muscles (genioglossus, geniohyoid, mylohyoid), epiglottis, pharyngeal recess, and retropharyngeal space.

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    Identify several landmarks as indicated on the dissection photographs of the hemisected head.

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    The nasal cavities extend from the nares anteriorly to the choanae posteriorly, constituting the nasal cavity proper. Identify the superior, middle, and inferior nasal conchae, which are located within the nasal cavity proper ( Figs. 26.6 and 26.7 ).

    Fig. 26.6, Sagittal view of nasal cavity revealing sphenoidal, ethmoidal, and frontal sinuses; concha; nasal bone; torus tubarius; and salpingopharyngeal fold.

    Fig. 26.7, Sagittal view of nasal cavity revealing sphenoidal and ethmoid sinuses and nasal concha highlighting drainage pathways that include sphenoethmoidal recess and meatus associated with superior, middle, and inferior conchae.

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    Identify the superior meatus, the space between the superior and middle conchae.

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    Continue inferiorly and identify the space between the middle and inferior conchae, the middle meatus.

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    Finally, identify the space between the inferior concha and the hard palate, the inferior meatus (see Figs. 26.6 and 26.7 ).

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    Posterior to the superior concha is a space referred to as the sphenoethmoidal recess. Identify the opening for the sphenoidal sinus into this recess (see Figs. 26.6 and 26.7 ).

Dissection Tip

Some specimens have an increased thickness of the nasal mucosa (see Figs. 26.6 and 26.7 ).

Dissection Tip

In most cadavers it is necessary to break away part of the thin, medial wall of the sphenoidal sinus to gain access to its interior. Some specimens may also have a “supreme” concha.

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    With forceps, lift the middle meatus upward and identify the ethmoidal bulla.

Anatomy Note

The ethmoidal bulla can be oversized from hypertrophy of the ethmoidal cells.

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    Locate the opening of the ethmoidal infundibulum into the semilunar hiatus ( Fig. 26.8 ).

    Fig. 26.8, Sagittal view of nasal cavity with middle concha reflected, revealing opening of ethmoidal cells, ethmoidal bulla, semilunar hiatus, and maxillary sinus opening.

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    With scissors or a scalpel, cut the middle concha away from its junction with the lateral wall of the nasal cavity, and completely expose the middle meatus ( Fig. 26.9 ).

    Fig. 26.9, Sagittal view of nasal cavity with superior concha cut and middle concha removed revealing sphenoidal sinus and posterior, middle, and anterior ethmoidal cells. Middle concha removed, highlighting ethmoidal bulla, semilunar hiatus, and maxillary sinus opening.

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    Identify the anterior, middle, and posterior ethmoidal cells. In the superior meatus, find the ostia of the posterior ethmoidal cells (see Fig. 26.9 and Plate 26.1 ).

    Plate 26.1, A lateral view of the structures of the nasal cavity, with conchae cut away.

Anatomy Note

The hiatus semilunaris is the long, semicircular groove into which the frontonasal duct drains (drainage of frontal sinus through infundibulum), as well as the anterior ethmoidal cells.

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    Identify the opening of the maxillary sinus. Pass a probe into this opening.

Dissection Tip

Inspect the area of the middle meatus to determine whether there may be accessory openings for the maxillary sinus.

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    The ethmoidal bulla is formed by the bulging of ethmoidal cells into the middle meatus (see Fig. 26.9 ).

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    Remove the anterior half of the inferior nasal concha and identify the opening of the nasolacrimal duct ( Fig. 26.10 ).

    Fig. 26.10, Sagittal view of nasal cavity with middle concha removed and inferior concha cut and partially removed, revealing drainage pathways of superior, middle, and inferior conchae (nasolacrimal duct) and osteotomy to pterygopalatine fossa. Pterygopalatine fossa includes ganglion, nerve of pterygoid canal, greater and lesser palatine nerves, and sphenopalatine and descending palatine arteries.

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    Place a probe in the nasolacrimal duct.

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    Before dissection of the pterygopalatine fossa, identify the opening to the auditory or pharyngotympanic tube (eustachian tube) and place a probe into it (see Fig. 26.10 ).

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    Identify the elevation of the auditory tube and its muscular ridge, the salpingopharyngeal fold. At the opening of the eustachian tube, dissect away the mucous membrane ( Fig. 26.11 ).

    Fig. 26.11, Sagittal view of nasal cavity revealing sphenoidal, posterior middle, and anterior ethmoidal cells. Middle concha removed, revealing semilunar hiatus, ethmoid bulla, maxillary sinus opening, and superior, middle, and inferior conchae, as well as the perpendicular plate of palatine bone.

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    Identify the levator veli palatini muscle ( Fig. 26.12 ).

    Fig. 26.12, Sagittal view of nasal cavity revealing hard and soft palate, torus tubarius, salpingopharyngeal fold, opening of eustachian tube, and levator veli palatini muscle.

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    Anterior to the levator veli palatini, dissect out fat and other connective tissues ( Fig. 26.13 ).

    Fig. 26.13, Sagittal view of nasal cavity highlighting hard palate and revealing tensor and levator veli palatini muscles, torus tubarius, and salpingopharyngeal fold.

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    Identify the tensor veli palatini muscle (see Fig. 26.13 ).

Dissection Tip

The tensor veli palatini and levator veli palatini muscles are easy to distinguish because of the white, tendinous fibers of the tensor veli palatini (see Fig. 26.13 ).

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    Lift the soft tissues and mucous membranes at the space posterior to the nasal conchae and the tensor veli palatini (in essence, the posterior plate of the pterygoid process of the sphenoid bone) ( Fig. 26.14 ).

    Fig. 26.14, Sagittal view of nasal cavity with superior, middle, and inferior concha cut, revealing perpendicular plate of palatine bone, tensor and levator veli palatini, torus tubarius, and salpingopharyngeal fold.

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    Cut the posterior one third of the middle and superior conchae, and remove the mucosa and soft tissues to expose the palatine bone ( Fig. 26.15 ).

    Fig. 26.15, Sagittal view of nasal cavity highlighting perpendicular plate of palatine bone, tensor and levator veli palatini muscles, torus tubarius, and mucosa of hard palate.

Dissection Tip

The palatine bone is thin, and you can identify the course of the greater and lesser palatine nerves and vessels before removing it.

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    With a small electric drill, cut away the palatine bone, making a vertical cut from the sphenoidal sinus to the hard palate and posteriorly to the middle concha (see Figs. 26.15 and 26.16 ).

    Fig. 26.16, Sagittal view of nasal cavity highlighting middle and superior conchae cut and perpendicular plate of palatine bone with small osteotomy to reveal pterygopalatine fossa structures.

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    First, expose the greater and lesser palatine nerves, as well as the descending palatine artery and the greater and lesser palatine arteries ( Figs. 26.17 and 26.18 ).

    Fig. 26.17, Sagittal view of nasal cavity with greater and lesser palatine nerves retracted, revealing descending palatine artery.

    Fig. 26.18, Sagittal view of nasal cavity highlighting osteotomy of perpendicular plate of palatine bone to reveal sphenopalatine artery, greater and lesser palatine nerves, and descending palatine artery.

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    Continue drilling upward to the sphenoidal sinus. Identify the sphenopalatine artery and the pterygopalatine ganglion ( Fig. 26.19 and Plate 26.2 ).

    Fig. 26.19, Sagittal view of nasal cavity with osteotomy of perpendicular plate of palatine bone, revealing sphenopalatine artery, pterygopalatine ganglion, nerve of pterygoid canal, greater and lesser palatine nerves, and descending palatine artery.

    Plate 26.2, Nerves and arteries of the pterygopalatine fossa.

Dissection Tip

In this part of dissection, use fine forceps and scissors to separate the delicate nerves and arteries.

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    Continue drilling posteriorly to the pterygopalatine ganglion and inferior to the sphenoidal sinus. Expose the vidian nerve (nerve to pterygoid canal) ( Fig. 26.20 ).

    Fig. 26.20, Sagittal view of nasal cavity with osteotomy of perpendicular plate of palatine bone, revealing pterygopalatine ganglion, nerve of pterygoid canal, greater and lesser palatine nerves, and descending palatine artery.

Anatomy Note

The greater and deep petrosal nerves unite and form the nerve of the pterygoid canal. This nerve passes through the pterygoid canal of the sphenoid bone and then into the pterygopalatine fossa.

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    If time permits, drill away the sphenoidal sinus, and expose the connection of the pterygopalatine ganglion with the maxillary nerve ( Fig. 26.21 ).

    Fig. 26.21, Sagittal view of nasal cavity highlighting osteotomy of perpendicular plate of palatine bone and the sphenoidal sinus and revealing pterygopalatine fossa with pterygopalatine ganglion, nerve of pterygoid canal, greater palatine nerve, descending palatine artery, and maxillary nerve.

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    With scissors, reflect the oral mucosa from the hard palate, and identify the distribution of the greater and lesser palatine nerves ( Fig. 26.22 ).

    Fig. 26.22, Sagittal view of nasal cavity highlighting osteotomy of perpendicular plate of palatine bone, to show pterygopalatine fossa with pterygopalatine ganglion, nerve of pterygoid canal, greater and lesser palatine nerves and arteries, and descending palatine artery.

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    The lateral wall of the nasal cavity is dissected on one side of the head, as well as the pterygopalatine fossa. Dissect the nasal septum on the opposite side, i.e., the other hemisected part of the head ( Fig. 26.23 ).

    Fig. 26.23, Sagittal view of nasal and oral cavities revealing nasal septum and sphenoidal/frontal sinuses. Oral cavity reveals hard palate, soft palate, uvula, pharynx, floor of tongue muscles (genioglossus, geniohyoid), and epiglottis.

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    Remove the mucous membranes from the exposed surface of the nasal septum ( Fig. 26.24 ).

    Fig. 26.24, Sagittal view of nasal and oral cavities with nasal septum reflected, revealing superior concha, vomer bone, sphenoidal sinus, and frontal sinus. Oral cavity reveals tongue, floor of tongue muscles, uvula, epiglottis, and pharynx.

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    Identify the septal cartilage, perpendicular plate of the ethmoid bone, and the vomer bone ( Fig. 26.25 ).

    Fig. 26.25, Sagittal view of nasal and oral cavities revealing sphenoidal and frontal sinuses, septal cartilage, vomer bone, superior concha, and nasal pharynx. Oral cavity reveals uvula, tongue, and genioglossus, geniohyoid, mylohyoid, and anterior belly of digastric muscles.

Dissection Tip

Usually, it is difficult and time-consuming to find any of the nerves or vessels on the nasal mucosa, because of drying and shrinkage from fixation.

Identify the following:

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    1. Sphenoethmoidal recess, posterior to the superior concha, the location of the opening for the sphenoidal sinus

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    2. Superior nasal meatus, beneath the superior concha, the opening for the posterior ethmoidal cells

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    3. Middle nasal meatus, the ethmoidal bulla, with openings for middle ethmoid cells and the maxillary sinus

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    4. Inferior nasal meatus, the opening of the nasolacrimal duct

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    5. Ethmoidal infundibulum, for the opening of the frontonasal duct from the frontal sinus

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    6. Hiatus semilunaris, the semilunar hiatus, the long, crescent-shaped opening for the anterior ethmoidal cells

Laboratory Identification Checklist

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