Tiêu đề 4. OSSEOUS SYSTEM.pdf ✅

PHARMD GURU Page 1 INTRODUCTION:  Skeleton constitutes the bony framework of the body.  The skeletal system consists of about 206 bones to make a strong, movable living framework for the body. It supports and protects softer, delicate tissues and organs and they form joints for the movement of the body. The bones making up the skeleton are of various types e.g. long bones, short bones, flat bones, irregular bones etc. The bones perform following important functions: (1) They form the supporting framework of the body; (2) They form boundaries for the cranial, thoracic and pelvic cavities; (3) They give protection to delicate organs; (4) They form joints which are essential for the movement of the body; (5) They provide attachment for the voluntary muscles. This helps in the movements of joints; (6) They form blood cells in the red bone marrow in cancellous bone; and (7) They act as a store house of calcium salts. The bones of the skeleton are divided into two groups: (1) The Axial Skeleton: It consists of the bones which form the skull, the vertebral column and the thoracic cage. (2) The Appendicular Skeleton: It consists of shoulder girdles, upper limbs, pelvic girdle and lower limbs. 1)THE AXIAL SKELETON: The bones of the axial skeleton constitute the central bony core of the body. THE SKULL: It rests upon the upper end of the vertebral column and its bony structure is divided into two parts viz., cranium and face. OSSEOUS SYSTEM

PHARMD GURU Page 3 1. The Frontal Bone: The frontal bone is a large flat bone which forms the forehead and also the upper part of the orbital cavities. It develops in two parts which gradually fuse into one bone. It contains two cavities called the frontal sinuses which lie one over each orbit. They contain air which enters by a small opening leading from nasal cavities. These sinuses give lightness to the bone and resonance to the voice, acting as sounding chambers. 2. The Parietal Bones: The parietal bones are two flat bones forming sides and roof of the skull. They articulate with each other and with frontal, occipital and temporal bones. The inner surface is concave and is grooved by the brain and blood vessels. 3. The Occipital Bone: The occipital bone forms back of the head and part of the base of the skull. It forms immovable joints with parietal, temporal and sphenoid bones. On the outer surface, there is a roughened area called occipital protuberance. In this bone, there is a large opening known as the foramen magnum, for the passage of spinal cord. 4. The Temporal Bones: The temporal bones lie on each side of the head (Fig. 4.2). Each temporal bone is divided into four parts. They are:  The squamous part is the fan shaped portion.  The mastoid process is a thickened part of bone and can be felt just behind the ear. It contains a large number of small air sinuses which communicate with middle ear. A styloid process projecting from it gives attachment to muscles.  The petrous portion is thick and forms a part of the base or floor of the skull and contains the organ of hearing.  The zygomatic process is directed forward and articulates with the zygomatic bone to form zygomatic arch.
PHARMD GURU Page 4 5. The Sphenoid Bone: The sphenoid bone is an irregular bone in the shape of a bat with its wings outstretched and lies in the centre of the base of the skull (Fig. 4.3). On the superior surface of the middle of the bone, there is a depression in which the pituitary gland rests. The wings are perforated by many openings for the passage of nerves and blood vessels.