Musculoskeletal System - Skeletal System PDF

# Anatomy ## BSN YEAR I ### MUSCULO SKELETAL SYSTEM Dr. Manju Avinash Nair ## At the end of the session students will be able to: - Describe the components of the musculoskeletal system. - Identify the bones of the skeletal system in human body ## The musculoskeletal system consists of: - the...

# Anatomy ## BSN YEAR I ### MUSCULO SKELETAL SYSTEM Dr. Manju Avinash Nair ## At the end of the session students will be able to: - Describe the components of the musculoskeletal system. - Identify the bones of the skeletal system in human body ## The musculoskeletal system consists of: - the bones of the skeleton (skeletal system) - their joints - and the skeletal (voluntary) muscles that move the body ## Bones ### Functions of bones: - providing the body framework - giving attachment to muscles and tendons - allowing movement of the body - protecting the organs they contain - haemopoiesis - the production of blood cells in red bone marrow - mineral storage, especially calcium, phosphate ## Types of bones ### Bones are classified as long, short, irregular, flat and sesamoid. ### Long bones - These bones are longer than they are wide. - Most long bones are found in the limbs. - Eg. Femur (bone of the thigh) ### Long bones consist of: - a shaft - diaphysis - two metaphysis (in children) - two extremities - two epiphyses ### The diaphysis is composed mainly of compact bone with a central medullary canal, containing fatty yellow bone marrow. ### The metaphysis is the narrow portion of a long bone between the epiphysis and the diaphysis. It contains the growth plate, the part of the bone that grows during childhood, and as it grows it ossifies near the diaphysis and the epiphyses. ### The epiphyses consist of an outer covering of compact bone with spongy (cancellous) bone inside. ### Long bones are covered by periosteum. - Periosteum has two layers: outer layer is tough and fibrous, and protects the bone underneath. - Periosteum covers the whole bone except within joint cavities, allows attachments of tendons and is continuous with the joint capsule. - Hyaline cartilage replaces periosteum on bone surfaces that form joints ## Short, irregular, flat and sesamoid bones. - These have no shafts or extremities and are diverse in shape and size. ### Examples include: - short bones - carpals (wrist) - irregular bones - vertebrae and some skull bones - flat bones - sternum, ribs and most skull bones - sesamoid bones - patella (knee cap) ## Microscopic structure of bone Bone is a strong and durable type of connective tissue ### Constituents - **Inorganic matrix** - major constituent (65%) is a mixture of calcium salts mainly calcium phosphate - gives bone great hardness - **Organic material**: Osteoid - which is composed mainly of collagen. Collagen is very strong and gives bone slight flexibility. ## Bone cells There are three types of bone cell: - osteoblast - osteocyte - osteoclast. ### Osteoblasts: - Bone-forming cells responsible for the deposition of both inorganic salts and osteoid in bone tissue. - As they deposit new bone tissue around themselves, they become trapped and differentiate into osteocytes. ### Osteocytes: - These are mature bone cells that monitor and maintain bone tissue. ### Osteoclasts: - These cells break down bone, releasing calcium and phosphate. ## Compact (cortical) bone - Compact bone makes up about 80% of the body bone mass. - It is made up of a large number of parallel tube shaped units called osteons. - **Haversian systems**: The central canal contains nerves, lymphatics and blood vessels and is linked with neighbouring canals by perforating canals. - The series of cylindrical plates of bone arranged around each central canal are called lamellae. - Between the adjacent lamellae of the osteon are strings of little cavities called lacunae, containing an osteocyte. ## Spongy (cancellous, trabecular) bone - looks like a honeycomb. - consist of a few lamellae and osteocytes interconnected by canaliculi. - The spaces between the trabeculae contain red bone Marrow. - Spongy bone is lighter than compact bone. ## The bones of the skeleton ### Classification: - **The axial skeleton** - **The appendicular skeleton** ### The axial skeleton - consists of the skull, vertebral column, ribs and sternum - Together the bones forming these structures constitute the central bony core of the body, the axis. ### The appendicular skeleton - consists of the shoulder and pelvic girdles and the limb bones. ## Vertebral column - There are 26 bones (24 movable + sacrum and coccyx) - The first seven vertebrae in the neck form the cervical spine. - Next 12 vertebrae are the thoracic spine. - Next five the lumbar spine. - The sacrum formed by 5 fused bones. - The coccyx formed by 4 fused bones. - Each vertebra is identified by the first letter of its region in the spine, followed by a number indicating its position. - Eg. L3 is third lumbar vertebra. ### Characteristics of a typical vertebra #### The body: - broad, flat, largest part of the vertebra. - When the vertebrae are stacked together between each pair of bones is a tough pad of fibrocartilage called the intervertebral disc. - The bodies of the vertebrae lie to the front of the vertebral column. #### The vertebral (neural) arch: - encloses a large vertebral foramen. - lies behind the body, and forms the posterior and lateral walls of the vertebral foramen. - The lateral walls are formed from plates of bone called pedicles, and the posterior walls are formed from laminae. - The region where the pedicle meets the lamina -- the transverse process. - The two laminae meet at the back is a process called the spinous process. - The vertebral foramina form the vertebral (neural) canal that contains the spinal cord. ### The Vertebrae #### 1. Cervical vertebrae - smallest vertebrae - The transverse processes have a foramen through which a vertebral artery passes upwards to the brain. - C1 - the atlas, is the bone on which the skull rests. The atlas permit nodding of the head. - Below the atlas is the axis (C2), has a small body with a small superior projection called the odontoid process .The head pivots side to side on this joint. #### 2. Thoracic vertebrae - The 12 thoracic vertebra. - Larger than cervical vertebra #### 3. Lumbar vertebrae - These are the largest of the vertebrae because they have to support the weight of the upper body. #### 4. Sacrum - Consists of five vertebrae fused together. - Articulates with the 5th lumbar vertebra. - On each side it articulates with the ilium to form a sacroiliac joint. - inferior tip it articulates with the coccyx. - The vertebral foramina are present on each side of the bone for the passage of nerves. #### 5. Соссух - This consists of the four terminal vertebrae fused to form a very small triangular bone, the broad base of which articulates with the tip of the sacrum. ## Features of the vertebral column ### Intervertebral discs: - Intervertebral discs separate the bodies of adjacent vertebrae, consist of an outer rim of fibrocartilage (annulus fibrosus) and a central core of soft gelatinous material (nucleus pulposus). - They have a shock-absorbing function, help in flexibility of the vertebral column as a whole. ### Intervertebral foramina - When two adjacent vertebrae are viewed from the side, a foramen formed by a gap between adjacent vertebral pedicles can be seen. - Throughout the length of the column there is an intervertebral foramen on each side between every pair of vertebrae, through which the spinal nerves, blood vessels and lymph vessels pass. ## Ligaments of the vertebral column - These ligaments hold the vertebrae together and keep the intervertebral disc in position. - The transverse ligament holds the odontoid process of the axis in the correct position in relation to the atlas. - The anterior longitudinal ligament extends the whole length of the column and lies in front of the vertebral bodies. - The posterior longitudinal ligament lies inside the vertebral canal and extends the whole length of the vertebral bodies of the bones. - The ligamenta flava connect the laminae of adjacent vertebrae. - The ligamentum nuchae and the supraspinous ligament connect the spinous processes, extending from the occiput to the sacrum. ## Curves of the vertebral column: - When viewed from the side, the vertebral column presents four curves: two primary and two secondary. ## Movement of the vertebral column - Movement is limited --- flexion (bending forward), extension (bending backward), lateral flexion (bending to the side) and rotation. There is more movement in the cervical and lumbar regions than elsewhere. ## Functions of the vertebral column - strong bony protection for the spinal cord lying. - the pedicles of adjacent vertebrae form intervertebral foramina, one on each side, providing access to the spinal cord for spinal nerves, blood vessels and lymph vessels. - movement of the whole column. - support of the skull. - the intervertebral discs act as shock absorbers, protecting the brain. - formation of the axis of the trunk, giving attachment to the ribs, shoulder girdle and upper limbs, and the pelvic girdle and lower limbs. ## Thoracic cage - **Anterior**: sternum - **Lateral**: twelve pairs of ribs - **Posterior**: twelve thoracic vertebrae. ### a. Sternum (breast bone) - Middle of the front of the chest. - The **manubrium** is the uppermost section and articulates with the clavicles at the sternoclavicular joints and with the first two pairs of ribs. - The body gives attachment to the ribs. - The xiphoid process is the inferior tip of the bone. It gives attachment to the diaphragm, muscles of the anterior abdominal wall and the linea alba ### b. Ribs - The 12 pairs of ribs form the lateral walls of the thoracic cage. - elongated curved bones and articulate posteriorly with the vertebra. - Anteriorly, the first seven pairs of ribs articulate directly with the sternum and are known as the **true ribs**. The next three pairs articulate only indirectly, costal cartilages attach the ribs to the sternum. The lowest two pairs of ribs, referred to as **floating ribs**, do not join the sternum at all. - Between each rib are the **intercostal muscles**, which move the rib cage during breathing.