The Skeleton Dr. Ali Ebneshahidi ebneshahidi Axial Skeleton • Skull 22 bones • 8 cranial bones – Frontal 1 – Parietal 2 – Occipital 1 – Temporal 2 – Sphenoid 1 – Ethmoid 1 • 14 facial bones – Maxilla 2 – Palatine 2 – Zygomatic 2 – Lacrimal 2 – Nasal 2 – Vomer 1 – Inferior nasal concha 2 – 1 mandible ebneshahidi • Middle ear bones Malleus 2 6 bones Incus 2 Stapes 2 • Hyoid bone Hyoid 1 1 bones • Vertebral column 26 bones Cervical vertebra 7 Thoracic vertebra 12 Lumbar vertebra 5 Sacrum 1 Coccyx 1 • Thoracic cage 25 bones Ribs 24 Sternum 1 ebneshahidi The Appendicular Skeleton • Pectoral girdle Scapula 2 4 bones Clavicle 2 • Upper limbs 60 bones Humerus 2 Radius 2 Ulna 2 Carpal 16 Metacarpal 10 Phalanx 28 ebneshahidi • Pelvic girdle 2 bones Coxal bone 2 • Lower limbs 60 bones Femur 2 Tibia 2 Fibula 2 Patella 2 Tarsal 14 Metatarsal 10 Phalanx 28 Total 206 bones ebneshahidi Skull (Cranium) • Skull Skull: protect brain (brain case). Facial bones: - Contains cavities for sense organ (eyes, smell). - Frame of the face. - Attachment sites for mulches of mastication & facial expression. ebneshahidi The Eight bones of the cranium a) Frontal bone (forehead ) • Frontal sinuses • Forms superior part of orbits • Forms roof of nasal cavity • b) Parietal bones and major sutures • Curved , rectangular bone • Forms the bulging sides and roof of cranium • The 4 largest sutures occur where parietal bone articulates with other bones. ebneshahidi • Coronal suture : where parietal bones meet the frontal bone anteriorly. • Lamboid suture : where parietal bones meet the occipital bone posteriorly. • Squamous suture : where parietal and temporal bone meet on the lateral aspect of the skull . • Sagittal suture : where the 2 parietal bones meet superiorly at the cranial midline . ebneshahidi ebneshahidi • C) Occipital bone : • Forms the back (posterior) of skull • Foramen magnum : a large opening on its lower surface houses nerve fibers that pass through and enter the vertebral canal to become the spinal cord . • Occipital condyles : articulates with the first vertebra (atlas) • Hypoglossal canals : for passage of hypoglossal nerves. ebneshahidi ebneshahidi • d) Temporal bones : – Lateral sides of skull. – Contains the external auditory meatus (external ear). – Mandibular fossa – receive condyles of mandible (lower jaw). – Zygomatic arch (process) – projects interiorly from the temporal bone. – Mastoid process – attachment for muscles of neck. – Styloid process – attachment for muscles of tongue and pharynx. – Jugular fareamen – at the junction of occipital and petrous temporal bone allows passage of the internal jugular vein. – Carotid canal – transmit internal carotid artery. ebneshahidi ebneshahidi ebneshahidi • e) Sphenoid bone (butterfly - shaped) – Sella turcica – indentition of a part of sphenoid, in the depression lies the pituitary gland . – Contains 2 sphenoid sinuses. – It has greater and lesser wings. – Optic foramina – allows passage of the optic nerve. – Superior orbital fissure – a long slit between the greater and lesser wing allows passage of the cranial nerves that control eye movements (III , IV, VI) to enter the orbit. ebneshahidi ebneshahidi ebneshahidi • F) Ethmoid bone: – Olfactory foramina – passage for the olfactory nerve. – Middle and superior nasal concha (nasal plates), also known as turbinates. – Ethmoid sinuses. ebneshahidi ebneshahidi Facial Skeleton • Maxillary bones (upper jaw) • All facial bones except mandible articulate with maxillae. • Forms roof of mouth (anterior 2/3 of hard palate). • Contains upper teeth . • Maxillary sinuses (largest sinuses). • Zygomatic process of maxilla articulate with zygomatic bone. • Infraorbital foramen – allows passage of infraorbital nerve. • Infraorbital fissure – at junction of maxilla with the greater wing of sphenoid allows passage of zygomatic nerve, maxillary nerve (a branch of cranial nerve V), and blood vessels. ebneshahidi ebneshahidi ebneshahidi • Palatine bones – L shaped . – Forms post 1/3 of hard plate . • Zygomatic bones (cheek bones) – Temporal process , which extends posteriorly to join the zygomatic process of temporal bone. Together these processes form the zygomatic arch . • Lacrimal bones – A groove in its anterior portion forms the lacrimal fossa (tear channel). • Nasal bones – Forms bridge of nose medially – Attachment of cartilaginous tissues that form the shape of the nose . ebneshahidi ebneshahidi • Vomer bone: unpaired, forms the nasal septum along with ethmoid bone. • Inferior nasal conches (largest): Support mucous membranes within nasal cavity . • Mandible (lower jaw) –Unpaired. –Horseshoe – shaped (u-shaped). –Largest bone of the face. –It has a body –anchors the lower teeth. –2 ramus. –Coronoid process – site of attachment of temporalis muscle that elevates jaw during chewing. –Mandibular condyle – articulates with mandibular fossa of temporal bone to form T.M.J. ebneshahidi ebneshahidi • The orbits: • Bony cavities within which the eyes are encased. The walls of each orbit are formed by parts of seven bones (the frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, and ethmoid bones). ebneshahidi Infantile skull • At birth, skull is incompletely developed, with fibrous membranes connecting the cranial bones. These membranes are called fontanels (soft spots). • Allow brain growth by allowing skull to expand. ebneshahidi The vertebral Column • The vertebral column (the spine) : • Cervical spine (C1-C7) • Thoracic spine (T1-T12) • Lumbar spine (L1-L5) • Sacrum (5 vertebra fused into one bone) • Coccyx (4 vertebra fused) Curvatures of spine: • Cervical & Lumbar are concave posteriorly • Thoracic & sacral curvature are convex posteriorly ebneshahidi Abnormal Curvatures: • Scoliosis: abnormal lateral curvature of spine. • Kyphosis : (hunch back) , exaggerated dorsally (T – spine ). • Lordosis : exaggerated Lumbar curvature. ebneshahidi Intervertebral Disc • Intervertebral discs : cushion like pads located between vertebrae. It is composed of 2 parts. • Nucleus pulpous – act like a rubber ball which gives disc elasticity and compressibility. • Annulus fibrosus – a strong collar of collagen fibers and fibro- cartilage, holds the nucleus pulpous in place and resists tension in spine. Rupture of annulus fibrosus causes protrusion of nucleus resulting in herniated disc. ebneshahidi General structure of vertebrae • Body: weight bearing portion, located anteriorly. • Vertebral arch : located posteriorly. Seven processes project form this arch. • Vertebral foramen: opening enclosed by the body and vertebral arch, through which the spinal cord passes. • Pedicle: project posteriorly from the vertebral body. ebneshahidi • Lamina: flattened plates that fuse posteriorly to close the arch. • Spinous process: posterior projection arising from the junction of 2 lamina (posterior projection of the arch). • Transverse process: extends laterally from each side of the arch. • Intervertebral foramina: the spinal nerves arising from the spinal cord pass through these holes. ebneshahidi Vertebral Characteristics • Cervical vertebrae: (C1-C7) • C1= known as atlas. • C2= known as axis. • C7= known as vertebra prominens. • C1 – has no body and no spinous process. • C2 – has a knob like structure called dens or odontoid process projecting superiorly. Odontoid allows rotation of atlas. • C3- C7 have the following characteristics: • The body is oval shaped • The SP's are short (except for C7 that is long). • Vertebral foramen is triangular & large . • Each T.P contains a transverse foramen through which the vertebral blood vessels pass to service the brain . ebneshahidi ebneshahidi • Thoracic vertebrae: (T1-T12) • The body is heart shaped • Vertebral foramen is circular • Sp is long and points sharply inferiorly • With exception of T11 and T12 ,they articulate with ribs. • Lumbar vertebrae: (L1-L5) • The body is massive and kidney shaped (support body weight). • Vertebral foramen is triangular • Sp's are short ebneshahidi ebneshahidi ebneshahidi • Sacrum: Triangular shaped structure. Formed by fusion of 5 vertebrae. Strengthen and stabilize the pelvis. • Coccyx (Tail bone): Formed by fusion of 4 vertebrae. ebneshahidi The bony Thorax (Thoracic Cage ) • Includes the ribs, thoracic vertebrae, the sternum, and the costal cartilages. • Sternum : (breast bone)- lies in anterior mid – line of the thorax. It results from the fusion of 3 bones: the Manubruin, the body and the xiphoid process. • Ribs : • 12 pairs • 1-7 ribs are true ribs because they join the sternum directly. • Reaming 5 ribs are false ribs (8 -12) they donot have sternal attachment, directly. • Ribs 11-12 are floating ribs – no anterior attachment . ebneshahidi ebneshahidi The Appendicular Skeleton • The pectoral girdle (shoulder girdle ): 4 parts • 2 clavicles (collar bones) & 2 scapulae (shoulder blades) • Clavicle: has a sternal (medial end) & an acrominal (lateral end) • Scapulae: – has the genocide cavity that articulates with the humerus of the arm, forming the shoulder joint. – spine – divides the scapula into unequal portions called the supra- spinous and infraspinous fossa. – the Acromion: the spine ends laterally in an enlarged anterior projection, articulates with clavicle to form A-C joint. – coracoids process – site of attachment of biceps muscle and other upper limb muscles . – subscapulars fossa (cavity) – concavity of entire anterior scapular surface . ebneshahidi ebneshahidi ebneshahidi The upper Limb • Humerus : single bone of the arm. • Head – fits into the glenoid cavity of scapula. • It has a greater