Axial Skeleton Lecture Notes PDF

Skeletal System (1) Axial Skeleton Dr. TARIG ALARABI Objectives: By the end of this lecture ,students should be able to know: 1- Bone Development. 2- Histological features of bones. 3- Types of bones. 4- Functions of the skeleton. 5- Parts of the skeleton. 6- Classification of bones. 7-...

Skeletal System (1) Axial Skeleton Dr. TARIG ALARABI Objectives: By the end of this lecture ,students should be able to know: 1- Bone Development. 2- Histological features of bones. 3- Types of bones. 4- Functions of the skeleton. 5- Parts of the skeleton. 6- Classification of bones. 7- Parts of the axial skeleton.  Introduction The bones provide attachment sites for muscles Bones also support and protect internal organs. The organs of the skeletal system are largely composed of connective tissue, including bone and cartilage.  Bone Development -Osteogenesis and ossification: is the process of bone tissue formation, which leads to: - The formation of the bony skeleton in embryos - Bone growth until early adulthood - Bone thickness, remodeling, and repair - It begins at week 8 of embryo development. There two types of ossification: 1- Intramembranous ossification: bone develops from a fibrous membrane E.g. flat bones of the face, skull and clavicle. 2- Intracartilagenous ossification: bone forms by replacing hyaline cartilage E.g. long bones..  Histo lo gic al Features of the Bo ne Definition: - Bone is a specialized type of connective tissue with a calcified solid intracellular matrix. - It is rich in blood supply. - It is consists of: 1. Bone cells: osteogenic cells, osteoblast, osteocytes and osteoclast. 2. Bone Matrix. 3. Periosteum: covering layer of bone from outside. 4. Endosteum: lining layer of bone from inside.  Types of Bone - There are two types of bone according to their structure : A- Compact (solid) bone: it is present in the shafts of long bone and the outer thin layer of spongy bone in old age. B- Spongy (cancellous) bone: it is present in the epiphyses of long bones, ribs, vertebrae and in flat bones. Compact and Spongy Bones  Functions of Bone (Skeleton) 1. Support the body. 2. Protect soft body parts. 3. Permits flexible movement. 4. Blood cell formation. 5. Mineral storage (calcium especially). 6. Site for muscle attachment (body movement).  The skeleton The skeleton of the human body is consists of: 206 bones divided into: 1. Axial Skeleton. 2. Appendicular Skeleton.  Classification of Bones According to their shape, the bones are classified into: -Long: bones of the limbs e.g. humerus and femur. - Short: bones of the hand and feet e.g. carpal and tarsal bones. - Irregular: e.g. vertebrae. - Flat: e.g. skull, scapula and sternum. - Sesamoid: small bone that embedded within a tendon. e.g. Patella. Sho rt b o nes L o ng b o nes Irregular b o ne Flat b o nes Sesamoid bone  The Axial Skeleton The axial skeleton lies in the midline of the body and consists of: 1. The skull. 2. The hyoid bone. 3. The vertebral column. 4. The thoracic cage. 1) The Skull: The skull contains the cranium, which protects the brain, and also includes the facial bones. 2) The Hyoid Bone: The hyoid bone located above the larynx is the only bone in the body that does not articulate with another bone. The hyoid bone anchors the tongue and serves as the site of attachment for the muscles associated with swallowing Bones of the skull Hyoid Bone 3) The Vertebral Column: The vertebral column consists of 33 vertebrae, and supports the head and trunk, protects the spinal cord and roots of spinal nerves, and serves as a site for muscle attachment. The vertebral column 4) The Thoracic cage: The Thoracic cage is composed of the thoracic vertebrae, the ribs with their associated cartilages, and the sternum. It protects the heart and lungs, and expands during inhalation.  The Ribs: There are 12 pairs of ribs attached to the thoracic vertebrae. The upper seven pairs of the ribs attach to the sternum (true ribs). the next three pairs connect indirectly to the sternum by means of common cartilage (false ribs), and the last two pairs are called (floating ribs) because they have no connection at all to the sternum.  The Sternum: It is consists of the manubrium sterni, the body, and the xiphoid process that fuse during fetal development. The Thoracic Vertebrae: They are 12 in number articulated with ribs and with each other through the intervertebral discs. Thoracic vertebrae and the thoracic cage Success is the goal that a real person seeks  References Snell, R.S., 2018. Snell’s Clinical Anatomy. Wolters kluwer india Pvt Ltd. Lumley, J.S., 2008. Surface anatomy: the anatomical basis of clinical examination. Elsevier Health Sciences. Martini, F.H., 2009. Anatomy and Physiology'2007 Ed. Rex Bookstore, Inc..