Anatomical Terms Used In Description Of Bones

Anatomical Terms Used In Description of Bones

1. 2. 3. 4. 5. 6. 7.

Foramen: an opening or a hole in a bone Canal: Bony tunnel (foramen of some length) Canaliculus: a very narrow canal Meatus: a narrow passage Sulcus: a groove or furrow Pit or fovea: a small depression Fossa: a large depression (may be articular or non articular

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Facet : a small, smooth articular area of a bone Ridge: a linear elevation, usually rough Crest: a ridge of some breadth Lip: the raised margin of a crest Process: localized elevation or projection of large size Tubercle: a small localized rounded thickening Tuberosity: same as tubercle but larger in size Head: a round articular area of bone Spine: a sharp pointed projection lamina: a thin plate of bone Sinus: cavity inside a bone eg. Air sinuses of skull.

Bones of Skull • A. The calvaria/Brain case consists of 8 bones • Paired:- 1.parietal 2.Temporal • Unpaired:- Frontal, occipital, sphenoid, ethmoid

• B. The facial skeleton consists of

14 bones • Paired: Maxilla, Zygomatic, Nasal, lacrimal, Palatine, Inf Nasal Concha • Unpaired: Mandible, Vomer

Mandible • Largest & strongest bone of the face and forms the lower jaw.

• Parts: • 1. Body: horse shoe (u) shaped, horizontal and convex forward • 2. Rami: one ramus on each side, projecting upwards from the posterior ends of the body.

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Body

• Possesses: 2 surfaces- 1. external 2. internal 2 borders- 1.upper(Alveolar), 2. Lower (base)

• A. external

Surfaces:

surface: Convex in outline

• Presents:

 Symphisis menti: a faint ridge in the midline in the upper part of the

   

body (indicates fusion of two halves of foetal bone) Mental protuberence: triangular raised area below sym menti, & forms the prominence of chin. Mental tubercles: small tubercle at each lateral angle of the mental protuberence. Mental foramen: a foramen below the interval between the 1st & 2nd premolar teeth. It leads into the mandibular canal. It gives exit to mental nerve and vessels. Ext oblique line: a faint line running upward & backward on each side from the mental tubercle, very prominent behind and continuous with the ant border of ramus.  Ant part gives origin to:  Depressor labii inferioris: infront  Depressor angulioris: behind. Its post part and the adjoining area gives origin of buccinator.  Platysma is inserted below the oblique line. 

 Incisive fossa: shallow depression below the incisor teeth. Gives origin to:-1. Mentalis 2. Parts of orbicularis oris.

B. Internal Surface: Concave in outline. Presents: •Mylohyoid ridge: (int oblique line): an oblique ridge running forward and downwards on each side from 3rd Molar tooth to the symphysis menti; very prominent behind. It divides the int surface in to 2 areas. a. Submandibular fossa below the line b. Sublingual fossa above the line •Gives origin to :  mylohyoid muscle: throughout its whole length. Sup constrictor muscle of pharynx: from its post end. •Groove for lingual nerve: a groove above the mylohyoid line but below the last molar tooth. It lodges lingual nerve. Above this groove sup constrictor muscle is attached.

•Sub-Mandibular fossa: a triangular hollow area

below the mylohyoid line

Lodges- 1. submandibular gland 2. submandibular lymph nodes 3. facial artery • Sublingual fossa: a triangular concave area above the mylohyoid line. lodges- sublingual salivary gland • Genial tubercles: 4 in numbers, just above the ant ends of mylohoid lines. They lie in pairs- 2 upper & 2 lower upper tubercle- gives origin to genioglossus muscles, one on each side. lower tubercle- gives origin to geniohyoid muscles, on each side. • Mylohyoid groove: runs downwards and forwards from the ramus on to the body below the post end of mylohyoid line transmits- mylohyoid vessels and nerves.

Borders – Upper border (alveolar part): presents: 16 sockets, 8 on each side for lodging the roots of teeth. Dental formulae: ICPM/2123 • Lower border (base of mandible): -thick and rounded -continuous with lower border of ramus behind 3rd molar teeth. Presents:#Digastric fossa: a shallow depression on either side of mid-line. It gives origin to ant belly of digastric. #Insertion of platysma: lower border & extending anteriorly on to the adjoining ext surface.

Ramus • Flattened, quadrilateral part projecting upwards from the post end of the body on each side, gives insertion to all muscles of mastication. • Possesses: 2 surfaces: 1. external (lateral) 2. internal (medial) 4 borders: anterior, posterior, upper, lower • 2 processes: 1. coronoid 2. condyloid

• Surfaces: a. lateral (ext) surface: flat surface, rough throughout except in upper & post part which is smooth Presents:-

1. Insertion of masseter muscle: to a rough area 2. Parotid gland lies in smooth upper & post part. B. Medial (int surface)

Presents:1. Mandibular foramen- near the center,leads into a

mandible canal and finally into mental foramen. 2. Lingula- a sharp thin process of bone projection from medial margin of mandibular foramen. Gives attachment to sphenomandibular ligaments. 3. Mylohyoid groove- begins just behind linguala and runs downwards & forwards to fade out at the post end of submandibular fossa. Lodges- mylohyoid vessels & nerves 4. Medial pterigoid is inserted below & behind the mylohyoid groove.

• Borders:-

• Ant border: sharp/ prominent. Continuous above to the anterior •

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border of coronoid process & below the oblique line. Post border: thick/ rounded, concave in the middle Upper (superior) border: Presents: Mandibular notch- in the middle Coronoid process- in front Condyloid process- behind Mandibular notch transmit- masseteric vessels & nerves Lower (inferior) border: continuous in front with the base of mandible. Processes:

Coronoid process: flat & traingular with the apex pointing upwards while the base is fused with upper & ant part of ramus. Its ant border is continuous with ant border of the ramus & the post border forms the ant boundary of mandibular notch. 1. Insertion of temporalis muscle: to the apex, margins, whole of medial surface and a part of lat surface close to the apex. 2. Masseter covers lateral surface.

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Condyloid process: projects upwards from the upper & post part of ramus.

• Presents:1. Head of Mandible: thick and expanded upper part. 2.

Articulates with the articular part of mandibular fossa of temporal bone to form TMJ. Neck of Mandible: the constricted part just below the head. It gives attachment to lat. Ligament of TMJ. Ant surface of the neck is hollowed out into a depression called pterygoid fovea or pit which gives insertion to lat pterygoid muscle.

cervical vertebrae Vertebral column consists of a number of separate irregular bones called vertebrae. Forms the central axis of the body

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1. 2.

Functions:

Protects spinal cord Supports and transmits body weight 3. Provides attachment to axial muscles 4. Provides movement of the trunk There are 33 vertebrae & 31 pairs of spinal nerves

Vertebrae Number Spinal

number

Cervical 7

cervical 8

thoracic 12

thoracic 12

lumber

5

lumber

5

sacral

5

sacral

5

coccyx

4

coccyx

1

Characteristics of vertebrae: A typical vertebrae has 2 parts 1. Body – Ant or ventral 2. Neural arch- post or dorsal Vertebral foramen: lies between body and arch. In between vertebrae there are intervertebral discs. Vertebral foramen lodges spinal cord with its meninges & blood vessels. Body of vertebrae: Shape and size: nearly cylindrical and shape varies in different regions. • 6 surfaces: Ant/post, upper/lower, 2 lateral • Vertebral (neural ) arch: 1. Pairs of pedicles 2. Pairs of lamina 3. Seven processes-

• • •

Spinous-1 Articular-4 Transverse-2

Arch is connected to the body by the pedicles.

1. pedicles- short, thick & passes backwards from the junction 2. 3. 4. 5.

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of lat & post surface of the body. Laminae- broad plates lying behind & medial to pedicles. They fuse behind in a median plane into the spinous process. Spinous process- passes backward and downward from the junction of the 2 laminae. Articular processes- 4 in number, 2 superior, 2 inferior. Arises from junction of pedicles & laminae. Transverse processes- 2 in number projects lat from the junction of pedicle and laminae. In thoracic region they articulates with ribs. Distinguishing features of vertebrae: Cervical- presence of foramen in transverse process called foramen transversarium. Thoracic- presence of costal facet on the body Lumber- no foramen no costal facets on the body.

Cervical vertebrae • • • • • • •

7 in numbers Identification: presence of foramen transversarium in the transverse process Typical c.v: 3,4,5,6 Atypical c.v: 1,2,7 1st c.v – atlas 2nd c.v- axis 7th c.v- vertebra prominens

Characteristics of typical vertebrae: 1. Body: • Smallest of all vertebrae • Transverse> AP measurement • Post surface has 2 vascular foramen, to transmit basi vertebral vein & NA. • Ant. & post surfaces are flat.

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Attachments: A. Anterior surface: • Ant long ligament: to upper and lower borders B. Posterior surface: Post long ligament: to upper and lower borders • 2. Vertebral foramen: • Larger than the body • Triangular 3. Pedicles: • Projects laterally and backwards 4. Laminae: • Long and narrow • Ligamentum flava attached to upper and lower part of anterior surface.

5. Spine: • short and bifid • Ligmentum nuchae is attached to it 6. Articular processes: • Form an articular pillar which projects laterally at the junction of pedicles and laminae. • Articular facets are flat and oval 7. Transverse process: • pierced by foramen called foramen transversarium • Transmits: vertebral artery & vein Attachment:

Atlas • • • • •

Distinguishing points:

No body No spine It has 2 arches: ant & post 2 lateral masses

1. • A. • •

Lateral masses: Lie obliquly between 2 arches Superior articular facets: Faces upwards and medially Concave and elongated (kidney shaped) B. Inferior articular facet: Faces downwards and backwards. • Round, slightly concave and flat • 2. Anterior arch: Short, curved anteriorly • Connects to lateral masses • There is a rough tubercle on the anterior aspect called the rough tubercle •

3. Posterior arch: • Upper surface has a wide groove behind the lateral masses • Posterior tubercle: small tubercle at the posterior part. It represents spinous process. Attachments: 4. Transverse processes: • Quite long and strong • Ends laterally in a tubercle Attachments:

Axis (2nd cervical vertebrae) • •

Distinguishing point: Presence of odontoid process (dens)

1. •

Odontoid process: Strong tooth like process projecting from superior surface of the body. • Half inch long • Represents the body of the atlas • Acts as a pivot around which atlas rotates Attachment: 2. Body: the odontoid process arises from the superior surface • • On the lateral side of the upper surace a large circular facet is present which articulates with the inferior facet of the lateral mass of atlas

3. laminae: • Thickest and strongest of all c.v • Gives attachment to ligamentum flava 4. spine: • Large and very strong Attachment: 5. Transverse process: • Very small Attachment:

seventh cervical vertebrae •

Called vertebra prominence because of its long and thick prominent spinous process

1. spine: • Long, thick, horizontal • Not bifurcated, ends behind in a tubercle Attachment: 2. Transverse process: • Big size • Foramen transversarium is relatively small • F.T may be double or absent • Transversed by accessory vertebral vein Attachment: