HUMAN ANATOMY – VOLUME 1

Fig. 49. Ethmoid bone.

A — posterior aspect: 1 — crista galli; 2 — cribriform plate; 3 — orbital plate; 4 — superior nasal concha; 5 — middle nasal concha; 6 — perpendicular plate. B — superior aspect: 1 — crista galli; 2 — orbital plate; 3 — ethmoidal cells; 4 — perpendicular plate.

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Fig. 50. Temporal bone.

A — external aspect: 1 — squamous part; 2 — sphenoidal margin; 3 — zygomatic process; 4 — articular tubercle; 5 — mandibular fossa; 6 — petrotympanic fissure; 7 — styloid process; 8 — sheath of styloid process; 9 — external acoustic opening; 10 — tympanic part; 11 — tympanomastoid fissure; 12 — mastoid process; 13 — mastoid notch; 14 — mastoid opening; 15 — parietal notch; 16 — groove for middle temporal artery. B — internal surface: 1 — parietal margin; 2 — petrosquamous fissure; 3 — arcuate eminence; 4 — parietal notch; 5 — groove for superior petrosal sinus; 6 — occipital margin; 7 — mastoid foramen; 8 — groove for sigmoid sinus; 9 — posterior surface of petrosal part; 10 — external opening (apertura) of aqueductus vestibuli; 11 — jugular notch; 12 — subarcuate fossa; 13 — internal acoustic opening; 14 — styloid process; 15 — external opening of cochlear canaliculus; 16 — groove for inferior petrosal sinus; 17 — superior border of petrous part; 18 — trigeminal impression; 19 — apex of petrous part; 20 — zygomatic process; 21 — sphenoid

margin; 22 — cerebral surface of squamous part.

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The a n t e r i o r s u r f a c e faces upwards. Near the apex this surface has a small t r i g e m i n a l i m p r e s s i o n on it, to the lateral side of which there are two foramina. The larger of them is called h i a t u s f o r t h e g r e a t e r p e t r o s a l n e r v e, from which a narrow homonymous groove passes medially towards the front. Laterally and to the font is the h i a t u s f o r t h e l e s s e r p e t r o s a l n e r v e. It continues into the homonymous groove. On the anterior surface of the pyramid there is a flattened area called t e g m e n t y m p a n i, which is the upper wall of the petrous part. Along the upper border of the pyramid there is a g r o o v e f o r t h e s u - p e r i o r p e t r o s a l s i n u s.

In the middle of the posterior surface is the i n t e r n a l a c o u s t i c o p e n i n g leading into the i n t e r n a l a c o u s t i c m e a t u s. Above this opening, to its lateral side, there is a s u b a r c u a t e f o s s a, below and

i n f e r i o r p e t r o s a l s i n u s. Near the j u g u l a r f o s s a there is a depression, in the bottom of which is the external aperture of the c o c h l e a r c a n a l i c u l u s.

The i n f e r i o r s u r f a c e of the pyramid has a complicated structure. Next to the base of the pyramid is a deep jugular fossa. To the front of the jugular fossa is a round external opening of the carotid canal. Its internal opening is situated on the apex of the pyramid. Between the external opening of the carotid canal and the jugular fossa there is a small p e t r o s a l f o s s u l a. Lateral to the jugular fossa a thin and long styloid process points downwards. Behind it is the s t y l o m a s t o i d f o r a m e n. Behind this foramen is the m a s t o i d p r o c e s s, which is broad and can easily be palpated through the skin. This process forms the posterior region of the temporal bone. Inside it there are air-filled cells, which communicate with the tympanic cavity. Medial to the process there is a deep mastoid notch. To the inside of this notch is the s u l c u s f o r t h e o c - c i p i t a l a r t e r y. At the base of the mastoid process there is sometimes a m a s t o i d f o r a m e n.

The t y m p a n i c p a r t of the temporal bone is formed by a curved narrow bone plate, which confines the e x t e r n a l a c o u s t i c o p e n i n g from above and behind. This foramen leads into the e x t e r n a l a c o u s - t i c m e a t u s. Between the tympanic part and mastoid process there is a narrow t y m p a n o m a s t o i d f i s s u r e. In front of the external acoustic opening is a t y m p a n o s q u a m o u s f i s s u r e. It is divided by a bony crest into the p e t r o s q u a m o u s f i s s u r e, which is situated closer to the m a n d i b u l a r f o s s a, and the p e t r o t y m p a n i c f i s s u r e, which is situated closer to the pyramid.

The s q u a m o u s p a r t is a bone plate, convex to the outside, with an oblique free upper edge. The external t e m p o r a l s u r f a c e of this

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part is smooth. On the internal c e r e b r a l s u r f a c e of the squama there are cerebral protuberances, digital depressions and arterial grooves. On the squama, above and to the front of the external acoustic opening, there is a z y g o m a t i c p r o c e s s. This process joins the temporal process of the zygomatic bone, forming the zygomatic arch. Behind the zygomatic process, at its base, is the mandibular fossa, which articulates with the condylar process of the mandible.

Canals of the temporal bone

The pyramid of the temporal bone contains several canals through which cranial nerves and blood vessels pass.

The carotid canal (canális caróticus) begins on the inferior surface of the pyramid at the ex t e r n a l o p e n i n g o f c a r o t i d c a n a l. It is at first directed upwards, then bends nearly at a right angle and goes medially to the front. The canal ends at the i n t e r n a l o p e n i n g o f c a - r o t i d c a n a l at the apex of the pyramid. This canal is a passage for the internal carotid artery and nerves of the carotid plexus into the cranial cavity. From the carotid canal two or three c a r o t i c o t y m p a n i c c a n a l i c u l i branch off and go into the tympanic cavity. These canaliculi contain the homonymous arteries and nerves.

The musculotubal canal (canális musculotubárius) begins at the apex of the pyramid, goes laterally to the back and enters the tympanic cavity. A horizontal septum divides this canal into two parts. One of them is the c a n a l f o r t e n s o r t y m p a n i, which creates tension on the tympanic membrane, and below it is the canal for auditory tube.

The facial canal (canáalis faciális) begins at the internal acoustic meatus. In the beginning it is directed perpendicularly to the long axis of the pyramid. At the level of the hiatus for the greater petrosal nerve it bends at a right angle and continues laterally to the back. Then the canal turns vertically down, rounds the tympanic cavity and ends as the stylomastoid foramen. This canal contains a section of the facial nerve.

The canaliculus for chorda tympani (canáliculus chórdae týmpani) begins at the wall of the facial canal, near its end, and opens into the tympanic cavity. This canal is a passage for the chorda tympani.

The tympanic canaliculus (canalículus tympánicus) begins at the bottom of the petrosal fossula. Directed upwards, it penetrates the lower wall of the tympanic cavity. Then the canal continues through the medial wall and ends in the region of the hiatus for the lesser petrosal nerve. This canal is a passage for the tympanic nerve.

The mastoid canaliculus (canalículus mastoídeus) begins in the jugular fossa and ends in the tympanomastoid fissure. Through this canal passes the auricular branch of the vagus nerve.

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BONES OF THE FACIAL SKULL

The maxilla (máxilla) is a paired bone. It consists of a body and four processes: alveolar, frontal, palatine and zygomatic (Fig. 51). The b o d y of the bone is irregular in shape and has four surfaces. Its anterior surface is slightly concave. It is separated from the o r b i t a l s u r f a c e by the i n - f r a o r b i t a l m a r g i n, beneath which there is an i n f r a o r b i t a l f o - r a m e n. On the medial edge of the anterior surface there is a deep n a s a l n o t c h, which forms part of the anterior opening of the nasal cavity. The orbital surface forms part of the lower wall of the orbit. In its back region there is an i n f r a o r b i t a l g r o o v e, which continues to the front into a homonymous canal, which opens as the infraorbital foramen. The i n - f r a t e m p o r a l s u r f a c e is separated from the anterior surface by the base of the z y g o m a t i c p r o c e s s. On the infratemporal surface there is a m a x i l l a r y t u b e r o s i t y (tuber maxillae), on which there are small a l v e o l a r f o r a m i n a of the a l v e o l a r c a n a l s. Medial to the tuber is the g r e a t e r p a l a t i n e g r o o v e, situated vertically. The n a s a l s u r f a c e of the body forms part of the lateral wall of the nasal cavity. On it is a m a x i l l a r y h i a t u s, leading into the m a x i l l a r y (Highmore’s) s i n u s, which is located inside the body of the maxilla. To the front of the maxillary hiatus is a vertical l a c r i m a l g r o o v e.

The f r o n t a l p r o c e s s extends upwards from the body of the maxilla and joins the nasal part of the frontal bone.

The a l v e o l a r p r o c e s s e s of the two maxillae form the a l v e o - l a r a r c h, which contains sockets called d e n t a l a l v e o l i. Each maxilla has alveoli for the roots of eight upper teeth. Alveoli are separated from each other with thin bony septa.

The p a l a t i n e p r o c e s s is a thick plate, which forms part of the hard palate. In the front part of the process, along the median line, it is pierced through by the i n c i s i v e c a n a l. In the back it is joined with the horizontal plate of the palatine bone.

The z y g o m a t i c p r o c e s s begins at the upper lateral part of the body of the maxilla, and extends towards the zygomatic bone.

The palatine bone (os palátinum) forms part of the hard palate, the orbit and of the pterygopalatine fossa. The palatine bone has two plates: the horizontal and the vertical plate, which are attached almost at a right angle. The medial edge of the h o r i z o n t a l p l a t e joins the edge of the analogous plate of the paired palatine bone. The back edge of the horizontal plate is free. Its front edge attaches to the palatine process of the maxilla. The p e r p e n d i c u l a r p l a t e of the palatine bone forms part of the lateral wall of the nasal cavity. On the lateral surface of the perpendicular plate is the greater palatine groove. Together with the homonymous grooves

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Fig. 51. Maxilla.

A — external surface: 1 — frontal process; 2 — anterior lacrimal crest; 3 — infraorbital margin; 4 — anterior surface; 5 — infraorbital foramen; 6 — nasal notch; 7 — anterior nasal spine; 8 — alveolar process; 9 — alveolar yokes; 10 — body of maxilla; 11 — zygomatic process; 12 — tuber of maxilla; 13 — infraorbital groove; 14 — orbital surface. B — internal surface: 1 — frontal process; 2 — ethmoid crest; 3 — conchal crest; 4 — lacrimal groove; 5 — maxillary sinus;

6 — nasal surface; 7 — palatine process; 8 — alveolar process; 9 — anterior nasal spine.

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on the maxilla and the pterygoid process it forms the greater palatine canal. On the medial surface of the perpendicular plate there are two horizontal crests. The upper one is the e t h m o i d a l c r e s t, which serves for attachment of the middle nasal concha. The lower is the c o n c h a l c r e s t, which serves for attachment of the inferior nasal concha.

The palatine bone has three processes: orbital, sphenoidal and pyramidal. The o r b i t a l p r o c e s s extends laterally forward and forms part of the lower wall of the orbit. The sphenoid process is directed medially to the back. It attaches to the inferior surface of the sphenoid bone body. The orbital and sphenoid processes confine the sphenopalatine notch. The p y r a m i d a l p r o c e s s extends from the palatine bone laterally downwards and to the back. This process is perforated by several l e s s e r narrow p a l a t i n e c a - n a l s, which open as homonymous foramina on its palatine surface.

The inferior nasal concha (cóncha nasális inférior) is a paired, thin, curved plate. It has a body and three processes. The lateral surface of its body is attached by its upper edge to the conchal crest of the maxilla and perpendicular plate of the palatine bone. All the processes of this bone begin at its upper edge. The l a c r i m a l p r o c e s s extends up to the lacrimal bone. The m a x i l l a r y p r o c e s s is directed downwards. On the posterior edge of the concha there is an e t h m o i d a l p r o c e s s, which extends upwards and attaches to the uncal process of the ethmoid bone.

The vomer (vómer) is an unpaired bone plate, which forms part of the nasal septum. Its lower edge attaches to the nasal crest of the maxilla and the palatine bone. Its posterior edge separates the choanae. The anterior edge attaches at the top to the perpendicular plate of the ethmoid bone, and in its bottom section with the cartilaginous nasal septum.

The nasal bone (os nasále) is paired, and forms part of the bony bridge of the nose. The upper edge of the nasal bone attaches to the nasal part of the frontal bone. Its lateral edge articulates with the frontal process of the maxilla. Its lower edge forms part of the piriform aperture, which is the front opening of the nasal cavity.

The lacrimal bone (os lacrimále) is paired and forms the front section of the medial wall of the orbit. With its lower front section the lacrimal bone attaches to the frontal process of the maxilla. In the back it is attached to the ethmoid bone. At the top the lacrimal bone borders with the medial edge of the orbital part of the frontal bone. On the lateral surface of the bone is the p o s t e r i o r l a c r i m a l c r e s t. In front of the lacrimal crest is a l a c r i m a l g r o o v e, which joins with the homonymous groove on the maxilla to form a lacrimal fossa.

The zygomatic bone (os zygomáticus) is paired. It articulates with the frontal bone, the temporal bone and the maxilla, thus strengthening

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the facial skull. The zygomatic bone has a lateral, a temporal and an orbital surfaces. The la t e r a l s u r f a c e faces laterally to the front and is perforated by a small z y g o m a t i c o f a c i a l f o r a m e n. The temporal surface forms the anterior wall of the infratemporal fossa and has a small zygomaticotemporal foramen. The o r b i t a l s u r f a c e, which forms the lower lateral wall of the orbit, is also perforated by a small z y g o m a t i c o - o r b i t a l f o r a m e n. The t e m p o r a l p r o c e s s of the zygomatic bone extends downwards and, together with the zygomatic process of the temporal bone, forms the zygomatic arch. The f r o n t a l p r o c e s s extends upwards and attaches to the z y g o m a t i c p r o c e s s of the frontal bone and the greater wing of the sphenoid bone.

The mandible (mandíbula) is the only motile bone of the skull. It is an unpaired bone, which has a body and two rami (Fig. 52). The b o d y of the mandible is prominent to the front. Its upper edge forms the a l v e o - l a r p a r t, which contains d e n t a l a l v e o l i that are separated by thin bony in t e r a l v e o l a r s e p t a. The front walls of the alveoli bulge forward, forming a l v e o l a r y o k e s on the external surface of the alveolar arch. On the anterior part of the body of the mandible, along the median line, there is a small m e n t a l p r o t u b e r a n c e. To the sides of it, at the level of the second premolar, there are small m e n t a l f o r a m i n a.

In the middle of the concave inner surface of the mandible there is a small protuberance called the m e n t a l s p i n e. To the sides of it there is a d i g a s t i c f o s s a. Somewhat higher, closer to the alveoli, on either side of the mental spine there is a s u b l i n g u a l f o s s a, which is an imprinting of the sublingual gland. Also on the internal surface of the mandible body there is an oblique m y l o h y o i d l i n e, beneath which is

to the back from the mandible body. In the place where the body joins each of the rami there is an a n g l e o f t h e m a n d i b l e. On its outer surface there is a m a s s e t e r i c t u b e r o s i t y, and on the inner surface is a p t e r y g o i d t u b e r o s i t y. On the inner surface of each ramus there is a m a n d i b u l a r f o r a m e n leading into a homonymous canal, which ends at the mental foramen. At the top the rami diverge into the coronoid and the condylar processes. The c o r o n o i d p r o c e s s in the front is separated from the condylar process in the back by the m a n d i b u l a r n o t c h. The c o n d y l a r p r o c e s s continues into the neck of the mandible, and ends as the h e a d o f t h e m a n d i b l e.

The hyoid bone (os hyoídeum) is situated in the anterior section of the neck. It is hung to the skull and connected with the larynx by means of muscles and ligaments. The hyoid bone consists of a body and two pairs of processes, namely the g r e a t e r and l e s s e r h o r n s. The b o d y is curved

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Fig. 52. Mandible.

A — external aspect (from the left and up): 1 — coronoid process; 2 — mandibular notch; 3 — condylar process; 4 — ramus of mandible; 5 — masseteric tuberosity; 6 — angle of mandible; 7 — oblique line; 8 — body of mandible; 9 — mental foramen; 10 — mental protuberance; 11 — mandibular foramen. B — internal aspect: 1 — coronoid process; 2 — mandibular notch; 3 — condylar process; 4 — pterygoid fossa; 5 — mandibular foramen; 6 — angle of mandible; 7 — pterygoid tuberositas; 8 — mylohyoid groove; 9 — mylohyoid line; 10 — submandibular fossa; 11 — sublin-

gual fossa; 12 — digastric fossa; 13 — lingula.

bone plate, prominent to the front. The lesser horns are short and sharpened, and extend from the body laterally and upwards. The greater horns are elongated and thickened at the ends, and extend from the body to the back.

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Questions for revision and examination

1.How many bones make up the cranial skull and the facial skull? Name these bones.

2.Describe the structure of the frontal bone.

3.Describe the structure of the temporal bone and name its foramina and canals.

4.Name the foramina and canals of the mandible and maxilla.

SKULL AS A WHOLE

The upper part of the cranial skull is called the roof, skullcap or the c a l v a r i a in accordance with its localization. The lower part of the skull is called the b a s e. The r o o f is separated from the base by an imaginary line, which passes across the external occipital protuberance, along the superior nuchal line to the base of the mastoid process and then over the base of the zygomatic process of the temporal bone and the infratemporal crest of the sphenoid bone. The border of the calvaria then extends up to the base of the zygomatic process of the frontal bone, and along its supraorbital margin to the nasofrontal suture. The calvaria consists of the frontal squama, the parietal bones, the squamous parts of the occipital and temporal bones and the lateral parts of the greater wings of the sphenoid bone.

The border between the roof and the base is not designated on the internal surface of the skull, except in its posterior part. There a line can be drawn along the groove of the transverse sinus, which correlates with the superior nuchal line of the outer surface of the occipital bone.

There is a prominent region on the front section of the skull known as the forehead /frons/, which is formed by the frontal squama. On the upper sides of the roof there are prominences called parietal tubers. The anterior side sections of the skull each have two fossae: the temporal and infratemporal.

The temporal fossa /fóssa temporális/ is limited by the inferior temporal line at the top and the infratemporal crest on the bottom. The infratemporal crest separates the temporal and infratemporal fossae.

The infratemporal fossa /fóssa infratemporális/ is well visible on the lateral view of the skull. Its upper wall is formed by the lower part of the greater wing of the sphenoid bone. The medial wall is formed by the lateral plate of the pterygoid process of the sphenoid bone. The anterior wall is formed by the maxillary protuberance and a part of the zygomatic bone. The infratemporal fossa does not have lateral and inferior walls. In the front this fossa is connected with the orbit by the inferior orbital fissure, and from the medial side it is connected with the pterygopalatine fossa through the pterygomaxillary fissure.

The pterygopalatine fossa /fóssa pterygopálatina/ is limited by the maxillary protuberance in the front, the base of the pterygoid process of

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