Axial Skeleton Anatomy PDF

SKELETAL SYSTEM I Ajith Sominanda Herath College of Medicine, QU [email protected]. Mobile 33808329  Expected Learning Outcomes Classify the skeleton Skull Identify the main parts of the skull Name the bones of the skull and their major anatomical features...

SKELETAL SYSTEM I Ajith Sominanda Herath College of Medicine, QU [email protected]. Mobile 33808329  Expected Learning Outcomes Classify the skeleton Skull Identify the main parts of the skull Name the bones of the skull and their major anatomical features Identify the cavities within the skull and their related bones Name the principal sutures that join bones of the skull Vertebral Column (VC) (Spine) Identify the different regions of the VC Name the parts of a typical vertebra, and explain in general the regional differences between vertebrae Describe different types of joints between vertebrae Discuss the structure and importance of the intervertebral discs Describe normal and abnormal spinal curvatures and explain how they differ from one another thoracic cage Name the components of the thoracic cage  The Skeleton Consists of bones, cartilage, joints, and ligaments Composed of 206 named bones grouped into two divisions: Axial skeleton (80 bones) Appendicular skeleton (126 bones) (A separate lecture to follow)  The Axial Skeleton Formed from 80 named bones Lies in the midline of body Consists of skull, hyoid bone, vertebral column, and bony thorax (ribs and sternum)  The Skull Formed by cranial and facial bones Skull Consists of Two sets of bones 1. The cranium That encloses the brain Consist of 8 bones 1 frontal bone 2 Parietal bones 2 Temporal bones 1 occipital bone 1 Ethmoid bone 1 Sphenoid bone 2. Facial bones Forms the face Consists of 14 bones (12 paired bones & 2 single bones) 2 Maxillary bones 2 Palatine bones 2 Zygomatic bones 2 Lacrimal bones 2 Nasal Bones 2 Inferior Conchae 1 Vomer 1 Mandible Anterior aspect of Skull Lateral aspect of Skull Inferior aspect of Skull  Cranial Cavity Cranium is divided into cranial vault and the base Internally, prominent Media 1 Sent separately watch it bony ridges divide skull into three distinct cranial fossae Anterior cranial fossa Middle cranial fossa Posterior cranial fossa  Skull. Summary Consists of Two sets of bones 1. The cranium That encloses the brain Consist of 8 bones 1 frontal bone 2 Parietal bones 2 Temporal bones 1 occipital bone 1 Ethmoid bone 1 Sphenoid bone 2. Facial bones Forms the face Consists of 14 bones (12 paired bones & 2 single bones) 2 Maxillary bones 2 Palatine bones 2 Zygomatic bones 2 Lacrimal bones 2 Nasal Bones 2 Inferior Conchae 1 Vomer The skull contains smaller cavities Middle and inner ear cavities – in lateral aspect of cranial base Nasal cavity – lies in and posterior to the nose Orbits – house the eyeballs Air-filled sinuses – occur in several bones around the nasal cavity (Four paranasal air sinuses)  Skull foramina The skull contains approximately 85 named openings Foramina, canals, and fissures Provide openings for important structures: Spinal cord Blood vessels serving the brain 12 pairs of cranial nerves  Cranial bone sutures Three main sutures of the cranium: Coronal suture – runs in the coronal plane Located where parietal bones meet the frontal bone Sagittal suture – occurs where right and left parietal bones meet superiorly Lambdoid suture – occurs where the parietal bones meet the occipital bone posteriorly  Paranasal Air Sinuses  Frontal  Ethmoidal  Sphenoidal (single in midline)  Maxillary (largest one) Neonatal Skull The cranial bones are incompletely fused in infants, leaving soft spots called fontanelles.  The Hyoid Bone Lies inferior to the mandible and superior to the larynx The only bone with no direct articulation with any other bone Acts as a movable base for the tongue, and serves as a point of attachment of muscles used in swallowing.  The Vertebral Column Formed from 26 separate bones in the adult Transmits weight of trunk to the lower limbs Surrounds and protects the spinal cord Serves as attachment sites for muscles of the neck and back Held in place by: 1. Ligaments (fibrous) Anterior and posterior longitudinal ligaments Ligamentum flavum 2. Synovial joints 3. Inter-vertebral discs (cartilaginous) The Vertebral Column  General Structure of Vertebrae Typical vertebrae consists of A body Vertebral arch Processes: two transverse processes one spinous process four articular processes  Intervertebral Discs AF NP Cushion-like pads between vertebrae Act as shock absorbers Compose about 25% of height of vertebral column Composed of nucleus pulposus* (an inner gelatinous material) and annulus fibrosis (an outer ring of fibrocartilage) * Remnant of the notochord  Regions and Normal Curvatures Vertebral column is about 70 cm (28 inches) Vertebral column is divided into five major regions: Cervical vertebrae – 7 vertebrae of the neck region Thoracic vertebrae – 12 vertebrae of the thoracic region Lumbar vertebrae – 5 vertebrae of the lower back Sacrum – inferior to lumbar vertebrae – formed of five fused vertebrae - articulates with coxal (hip) bones Coccyx – or tailbone - most inferior region of the vertebral column – formed of fused 3-4 vertebrae. There are regional characteristics of vertebrae -Specific regions of the spine perform specific functions.  Normal Vertebral Curvatures Four distinct curvatures give vertebral column an S-shape Cervical and lumbar curvatures– concave posteriorly Thoracic and sacral curvatures – convex posteriorly Curvatures increase the resilience of the spine In fetus, only thoracic and sacral curvatures are found – C-shaped fetus  Normal Curvatures Abnormal Curvatures Cervical Thoracic Lumbar Sacral Scoliosis Kyphosis Lordosis  The Rib Cage The rib cage is composed of the thoracic vertebrae, the ribs and their cartilages, and the sternum.  The Ribs Consist of twelve pairs all connected to the thoracic vertebrae Ten pairs of ribs connect to the sternum via hyaline cartilage “true and false”. The lower two pairs are “floating ribs” because they are not attached to the sternum.  The Sternum (Breastbone) Protects the heart and lungs. It is shaped like a “dagger” made of the manubrium, the body, and the xiphoid process. A B Thank you