Axial Skeleton PDF

THE AXIAL SKELETON MR. M. BANDA Types of Skeletal System  206 bones of the human skeleton are grouped into the axial and appendicular skeletons  The axial skeleton is composed of the bones along the central axis of the body,  the skull  the vertebral column...

THE AXIAL SKELETON MR. M. BANDA Types of Skeletal System  206 bones of the human skeleton are grouped into the axial and appendicular skeletons  The axial skeleton is composed of the bones along the central axis of the body,  the skull  the vertebral column  the thoracic cage The axial skeleton  Cranial bones  Formed by 8 cranial bones; flat and irregular.  1 frontal, 2 parietal, 2 temporal bones, 1 occipital, 1 sphenoid, 1 ethmoid  Dura mater is divided into 2 layers  The one that lines the inner surface becomes the periosteum  Cranium  AKA known as neurocranium  Enclose the cranial cavity, which supports and protects the brain  Attachment sites for some head and neck muscles  Vault – “calvaria” = skullcap  Forms superior, lateral and posterior aspects of skull  Base or floor: inferior part  Prominent bony ridges divide cranial base into 3 “fossae” (steps) – anterior, middle and posterior  Cranial bones  In an adult skull, cranial bones consists of sutures (immovable joints)  Numerous perforations through which nerves, blood vessels, lymphatics pass (foramina).  Cranial bones Frontal bone (1):  forms anterior part of the cranium, roof of the orbital cavity, and supra orbital margins.  Contains 2 paranasal sinuses  Cranial bones Parietal bones (2):  forms the greater portion of the sides and roof of the cranial cavity  articulate with each other by the sagittal suture  with frontal bone by the coronal suture  Occipital bone by lambdoidal suture  with temporal bone by squamous suture.  Cranial bones Temporal bones (2);  forms the inferior lateral aspects of the cranium  articulates with parietal, occipital, sphenoid and zygomatic bones.  5 Parts; squamous, petromastoid, tympanic, zygomatic process and styloid process  Cranial bones Occipital bone;  forms posterior part and most of the base of cranium.  Articulates with parietal, temporal and sphenoid bones.  Cranial bones Occipital bone  has 2 articular condyles that form condyloid joints with the the atlas  between the condyles is the foramen magnum were the spinal cord passes into cranial cavity.  Cranial bones Sphenoid bone  lies at the middle part of the base of the skull, articulates with all other cranial bones.  superior surface in the middle of the bone is a little saddle-shaped depression called the hypophyseal fossa (sella turcica) the pituitary gland rests.  contains fairly large paranasal sinuses  Cranial bones Ethmoid bone;  Forms part of the orbital cavity, nasal septum, and the lateral walls of the nasal cavity  Cribriform plate forms roof of nasal cavity, olfactory nerves.  2 projections into the nasal cavity the upper and middle conchae  Contains paranasal sinuses  Facial Bones  AKA as viscerocranium  Located on the anterior aspect of skull  Form framework of face  Form cavities for sense organs of sight, taste and smell  Provides openings for passage of air and food  Hold the teeth  Anchor the muscles of the face  Bones of the face  The facial bones are formed by;  2 zygomatic  1 maxilla  2 lacrimal  1 vomer  2 palatine  2 inferior conchae  1 mandible  Bones of the face Zygomatic bones (2);  forms prominences of the cheeks  parts of the floor and walls of the orbital cavity  Bones of the face Maxilla;  Articulates with every bone of the face except the mandible.  Contains paranasal sinuses  Contains the alveoli (sockets) for the maxillary teeth.  Facial bones Nasal bone;  paired bones, meet at the midline to form part of the bridge of nose. Lacrimal bones;  paired bones they are posterior and lateral to the nasal bones and form part of the medial walls of the orbital cavities.  Each is paired by a foramen for the passage of the nasal lacrimal duct.  Facial bones Vomer bone:  a thin flat bone that forms the inferior portion of the nasal septum superiorly  articulate with the perpendicular plate of the ethmoid bone  Facial bones Palatine bones;  L shaped bone form posterior portion of the hard palate,  Forms part of the floor and lateral wall of the nasal cavity  and a part of the floor of the orbits  Facial bones Inferior conchae;  scroll like bones form a part of the inferior lateral wall of the nasal cavity.  Facial bones Mandible:  lower jaw, only movable bone of the skull  articulates with the temporal bone to form temporomandibul ar joint  Auditory Ossicles  Malleus  Incus  Stapes  Small bones in the middle ear that transmit air vibrations  Facial bones Hyoid bone;  horse shoe-shaped bone  does not articulate with any bone  suspended on the anterior aspect of the neck by ligaments and muscles.  supports the larynx and gives attachment to the base of the tongue. Vertebral column  consists of 24 movable bones (vertebrae)  makes up 2/5 of the total height.  intervertebral discs; consist of cartilage separate the bodies of each bone  Cervical Vertebra  C1 atlas cervical articulates with the skull permits nodding of the head,  Axis C2, the axis has a small body with a small superior projection called odontoid process held securely by transverse ligament the head turns side to side on this joint.  Cervical Vertebra 7th cervical vertebra:  C7 is known as the vertebral prominens palpable at the back of the neck Typical Cervical Vertebrae  Smallest  Lightest  Most flexible  Triangular vertebral foramen  Transverse processes have foramina (transverse foramen)  Spinous process bifid  Vertebral column 12 thoracic vertebrae  larger than cervical as it supports more body weight,  the bodies and transverse processes have facets for articulation with the ribs. Thoracic Vertebrae T1-T12  Heart shaped body  Additional small costal facets (costal=ribs)  Round or oval vertebral foramen  Form posterior part of rib cage  5 lumbar vertebrae  They are the largest vertebrae, as they support weight of the upper body  Have substantial spinous processes for muscle attachment.  1 sacrum  Consists of 5 rudimentary vertebrae fused  Form a triangular or wedge shaped bone  Concave anterior surface, the sacrum articulates with the 5th lumbar vertebra above and the coccyx below  Shapes posterior wall of pelvis The Sacrum Composite bone of 5 fused vertebrae Sacral foramina allow passage of vessels nerves Coccyx (the tailbone) Vertebral column 1coccyx  consists of 4 fused bones appears like a small triangular bone articulates with the sacrum above.  Characteristic of a typical vertebra Vertebral body:  size varies with the site, smallest in the cervical region and become larger towards the lumbar.  Characteristic of a typical vertebra Vertebral arch:  forms the posterior and lateral walls of the vertebra foramen  encloses a large vertebra foramen  Lateral walls are formed from plates of bone called pedicles and the posterior walls are formed from laminae  Characteristic of a typical vertebra Articulating surfaces:  Neural arch consists of 2 articulate with the vertebra above, and 2 below  Intervertebral foramina: found on each side between every pair of vertebrae, spinal nerves, blood and lymph vessels pass through  Characteristic of a typical vertebra  projecting from the regions where pedicle meets the lamina is a lateral prominence called transverse process  where the two laminae meet at the back is the spinous process (palpable along the vertebral column).  Intervertebral discs  Intervertebral discs; found between the bodies of adjacent vertebrae from C2 to the sacrum.  Each disc has an outer fibrous ring of fibro cartilage called annulus fibrosus and a central core called nucleus pulposus  discs form strong joints, permit movements and absorbs vertical shock. Curvatures of the vertebral column 40 Functions of the vertebral column  The vertebrae enable certain amount of movement  It supports the skull  Intervertebral discs act as shock absorbers protecting the brain  Forms the axis of the trunk giving attachments to the ribs. Shoulder girdle and upper limbs, pelvic girdle and the lower limbs  Thoracic cage made up of the sternum anteriorly 12 pairs of ribs 12 thoracic vertebrae.  Sternum  a flat bone in front of the chest  Manubrium;  uppermost section  articulates with clavicles at sternoclavicular joints and the first two pairs of ribs  The sternum  the body (middle portion) gives attachment to the ribs  junction between manubrium and body is called sterna angle  xiphoid process is the tip of the sternum, gives attachment to the diaphragm, muscles of the anterior abdominal wall and linea alba. Ribs  Both males and females 12 pairs  Ribs 1–7 are called true ribs; connect individually to the sternum by separate cartilaginous extensions called costal cartilages.  Ribs 8–12 are called false ribs; costal cartilages do not attach directly to the sternum. The costal cartilages of ribs 8–10 fuse to the costal cartilage of rib 7 and thus indirectly articulate with the sternum.  Ribs 11 and 12 are called floating ribs; no connection with the sternum. 7-45 Vertebral and Sternal Articulations Typical rib Disorders of the axial skeleton  Scoliosis  Kyphosis  fractures Disorders of the axial skeleton  Lordosis  Vertebral compression  QUIZ 1. How may bones are present in the axial skeleton? (A) 50 (B) 60 (C) 70 (D) 80 2. What is the name of the bone that articulate with all the bone of the neurocranium? (A) Ethmoid (B) Sphenoid (C) Maxilla (D) Frontal 3. Which of the following is the only movable bone of the skull? (A) Mandible (B) Maxilla (C) Hyoid (D) Zygomatic 4. What do you call an opening where blood vessels and nerve pass through in a bone? (A) Fissure (B) Fossa (C) Foramen (D) Fovea 5. How many pair of ribs are there in the thoracic cage? (A) 10 (B) 12 (C) 20 (D) 24  THE END THANK YOU!