13. Skeletal System

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Information about 13. Skeletal System
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Published on February 15, 2020

Author: ruch001

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The Human Skeleton: The Human Skeleton General Training Module RK Contents: Contents Classification of bones Long bones and other types Example for each type of bones Function of Bones in the human body The skeleton and its bones Axial Skeleton The Skull The vertebral column Appendicular Skeleton Shoulder Pelvis Joints Bones of the Body - Some Interesting facts: Bones of the Body - Some Interesting facts At the time of birth there are 300-350 bones which fuse together as baby grows An infant has 270 bones where a fully grown adult has 206 bones 106 are in hands and feet only The longest bone in your body, the femur (thighbone), is about 1/4 of your height The smallest is the stapes (or stirrup) in the ear, which is about 1/10 of an inch Adult human bones account for 14% of an adult’s body weight Types of Bones: Types of Bones Bones are classified into: Long Bones Short bones Flat bones Irregular Classification of Bones: Classification of Bones Long bones:  has an elongated shaft or diaphysis and two expanded ends (epiphyses) which are smooth and articular. Examples of typical long bones are humerus , radius, ulna, femur, tibia and fibula, metacarpals, metatarsals and phalanges Short bone: Their shape is usually cuboid , cuneiform, trapezoid, or scaphoid . Examples: carpal and tarsal bones  Flat Bones: They resembles shallow plates and form boundaries of certain body cavities. Examples: bone in the vault of the skull, ribs, sternum and scapula Irregular Bones  vertebra, hip bone, and bones in the base of the skull Classification of Bones: Classification of Bones Long Bones: Long Bones They have a diaphysis or a shaft Two extremities are called Epiphyses Diaphysis is made of compact bone and has a central medullary canal which contains yellow bone marrow with fat. Epiphyses mainly contains cancellous or spongy bone They are separated from the diaphysis by epiphyseal cartilages Bone growth in length occurs when the diaphyseal end of this cartilage is active and stops when it is completely ossified. Bone thickness is increased when bone is deposited under the periosteum (the covering of the bone) Long Bones: Long Bones Long Bones of the body: Long Bones of the body Short, flat, irregular and spongy bones : Short, flat, irregular and spongy bones Short, flat, irregular and sesamoid bones are made up of thin outer layer of compact bone and inner cancellous or spongy bone with red marrow. Tendons & Ligaments: Tendons & Ligaments A tendon is a fibrous connective tissue which attaches muscle to bone . Tendons may also attach muscles to structures such as the eyeball. A tendon serves to move the bone or structure. A ligament is a fibrous connective tissue which attaches bone to bone , and usually serves to hold structures together and keep them stable Functions of Bones: Functions of Bones Provide a framework for the body Give attachment to muscles and tendons Form joints that could be moved by muscles there by permit movement of the body as a whole and parts of the body in relation to the whole or other parts Form the walls of body cavities and protect the organs in them Contain red marrow in which blood cells develop Provide a reservoir of calcium The Skeleton: The Skeleton Two components: The Axial Skeleton : consists of the skull, the vertebral column, The rib cage (ribs and the sternum anteriorly ). Together they consists of the bony core of the body or the AXIS. The Appendicular Skeleton : consists of the shoulder girdle and the upper limbs and pelvic girdle with the lower limbs Axial Skeleton: Axial Skeleton The Skull: The Skull The bony structure of the skull is divided into two parts: Cranium: Covers and protects the brain inside. Has a base upon which the brain rests and vault that covers it. Made up of several flat, irregular bones. The sutures in between these bones in the adult are fused by fibrous tissue Face: Forms the anterior part of the head The Cranium: The Cranium The bones of the cranium: Frontal bone (1) Parietal Bones (2) Temporal bones (2) Occipital bone (1) Sphenoid bone (1) Ethmoid bone (1) The Face: The Face The bones of the face: Maxilla (1) Mandible (1) Vomer (1) Zygomatic (Cheek) bones (2) Nasal bones (2) Lacrimal bones (2) Palatine bones (2) Inferior Conchae (2) The Face Orbital Cavity Auditory Meatus Sinuses: Sinuses Sinuses containing air are present in the following bones of the skull: Maxillary Bone Frontal Bone Sphenoid bones Ethmoid bones They all communicate with the nose and are lined with ciliated mucous membrane Functions of the Sinuses: To give resonance to the voice To lighten the bones of the face and cranium making it easier for the head to balance on top of the vertebral column Sutures of the Skull: Sutures of the Skull Fontanelles: Fontanelles Fontanelles are membranous areas of the skull where three or more bones meet which still has not ossified at birth. There two largest fontanelles : Anterior fontanelle ossification is completed only 12 to 18 months after birth Posterior fontanelle – ossification is completed 2 to 3 months after birth Base of the Skull - Cranial Fossae: Base of the Skull - Cranial Fossae There are three large depressions in the skull base: posterior, middle, and anterior aspects of the floor of the cranial cavity: The posterior one that is the largest and deepest of the three and lodges the cerebellum, pons , and medulla oblongata—called also  posterior cranial fossa , posterior fossa T he middle one that lodges the temporal lobes laterally and the hypothalamus medially—called also  middle cranial fossa , middle fossa T he anterior one that lodges the frontal lobes—called also  anterior cranial fossa , anterior fossa Base of the Skull - Cranial Fossae: Base of the Skull - Cranial Fossae Forman Magnum The Vertebral Column : The Vertebral Column Is a columnar structure made up of a series of specialized irregular bones called vertebrae They are arranged one after the other running down longitudinally in the midline from the base of the skull above to the tail bone below. It consists of: 24 separate vertebrae The sacrum (made up of 5 fused bones) The Coccyx (4 fused bones) – the tail bone Vertebrae: Vertebrae The 24 separate vertebrae consists of three types of vertebra depending on their location: Cervical (7) Thoracic (12) Lumbar (5) There are features common to all these types of vertebrae as well as features distinct to each type The Typical Vertebra: The Typical Vertebra Parts of a typical vertebrae includes: Vertebral body located anteriorly , smallest in the cervical region get larger in the lumbar region Neural arch – an arch made up of two pedicles and laminae . Where pedicle on each side meet lamina there is a transverse process. And where the two laminae meet posteriorly there is spinous process. In addition there are two superior articular surfaces and two inferior articular faces which articulates each vertebra with the one above and one below respectively Vertebral body and neural arch together forms the neural canal through which the spinal cord runs The Typical Vertebra: The Typical Vertebra Parts of a typical vertebra: NEURAL CANAL The Vertebral Column: The Vertebral Column There are several important features and parts in the vertebral column when taken as a whole. They are: Intervertebral discs Intervertebral foramina Ligaments of the vertebral column Curves of the vertebral column Movements of the vertebral column Functions of the vertebral column Inter-vertebral Discs: Inter-vertebral Discs These are disc shaped structures that are located in-between vertebral bodies of adjacent vertebrae. They consists of: Outer rim of fibro-cartilage (annulus fibrosis) Central core of soft gelatinous material (nucleus pulposus ) Thinnest in cervical region and becomes progressively thicker towards lumbar region. They absorb shocks and provides flexibility to the vertebral column as a whole. Inter-vertebral Discs: Inter-vertebral Discs Inter-vertebral Foramina: Inter-vertebral Foramina When you look at the vertebral column from the side, a foramen can be seen in between two vertebrae. This is known as the inter-vertebral foramen. They are present throughout the length of the column and it is through them that the spinal nerves come out along with blood vessels and lymphatics . Ligaments of the vertebral column: Ligaments of the vertebral column The vertebrae of the vertebral column are held together by a series of ligaments These ligaments help to maintain the vertebrae in position and provides stability to the vertebral column They are attached to various parts of the vertebrae Ligaments of the vertebral column: Ligaments of the vertebral column Transverse Ligament Ligamentum Nuchae Supra- spinous Ligament Inter- spinous Ligament Ligamenta flava Anterior Longitudinal Ligament Posterior Longitudinal Ligament Curves of the vertebral column: Curves of the vertebral column There are 2 primary Curves (at birth): Thoracic curve Sacral curve Two 2ndry curves: Cervical curve (at 3 months): when head is lifted Lumbar curve (at 12 to 18 months): when walking Movements of the vertebral column: Movements of the vertebral column Movements between the individual bones are limited. However movements in cervical and lumbar vertebrae are greater than in other regions. The spine as a whole has an extensive range of movement: Flexion (bending forward) Extension (bending backwards) Lateral flexion (bending sideways) Rotation Functions of the vertebral column: Functions of the vertebral column Supports the skull Protects the spinal cord While providing space for the nerves to emerge Inter-vertebral discs act as shock absorbers protecting the brain Forms the axis of the trunk: provides attachment to ribs, shoulder and pelvic girdles, upper and lower limbs. Allows movement. Thoracic Cage: Thoracic Cage Parts of the thoracic cage: Sternum (1) Ribs - 12 pairs (24) Thoracic vertebrae (12) Slide43: Parts of the sternum The Sternum: The Sternum The sternum is the flat bone just under the skin in the front of the chest in the midline. It has 3 parts: the body, manubrium and the xiphoid process The manubrium is the upper most part. Articulates with the clavicles and the first two ribs Xiphoid process is the tip of the bone. It gives attachement to the diaphragm and the muscles of the anterior abdominal wall Ribs: Ribs There are 12 pairs of ribs forming the posterior, lateral and anterior parts of the rib cage. All of them are posteriorly attached to the 12 thoracic vertebrae. In the front however 10 of them are attached to the sternum by costal cartilages. Some directly (true ribs) others indirectly (false ribs). The last two pairs have no anterior attachments (floating ribs). Ribs: Ribs Appendicular Skeleton: Appendicular Skeleton Bones of the Shoulder Girdle: Bones of the Shoulder Girdle Each Shoulder Girdle contain two bones Clavicle (collar bone) – One on each side. Provides the only bony link between the upper limb and the axial skeleton. Medially it articulates with the manubrium of the sternum and laterally with the scapula Scapula (shoulder blade)- one on each side. A triangular flat bone lying on the posterior chest wall superior to rib cage separated form it by muscles. On the lateral surface it has Glenoid cavity, an articular surface for the humerus of the upper limb with which it forms the shoulder joint Bones of the Upper Limb: Bones of the Upper Limb Humerus in Upper Arm Radius laterally in the forearm Ulna – medially in the forearm 8 carpal bones in 2 rows in the wrist: Proximal row – scaphoid , lunate , triquetral , pisiform . Distal row – trapezium, trapezoid, capitate , hamate 5 Metacarpal bones in the hand Phalanges or finger bones (14): 3 in each finger and 2 in the thumb Bones of the Pelvic Girdle: Bones of the Pelvic Girdle Two Hip bones and the sacrum make the pelvis Each Hip Bone ( Innominate Bone) consists of three fused bones: the ilium , ischium and pubis. On its outer surface is acetabulum a deep depression for the head of femur to articulate forming the hip joint. Ilium is the superior part Pubis is the anterior part Ischium is the inferior and posterior part The three parts are united in the acetabulum Pelvic Bones: Pelvic Bones Bones of the Lower Limb: Bones of the Lower Limb Femur in the thigh Tibia in the lower leg Fibula in the lower leg Patella (knee cap) Tarsal or ankle bones (7): Cuneiform (3), Cuboid (1), Navicular (1), Calcaneus (1), Talus (1) 5 Metatarsals 14 Phalangeas : 3 in each toe and two in bog toe Hip Bone Joints : Joints Joints : Joints A joint is a site at which two or more bones come together Joints give the flexibility to the skeleton and therefore our body There are several types of joints Some have no movement: Fibrous or fixed joints Some have only slight movements: Cartilaginous joints Some move freely: Synovial joints Joints: Joints Fibrous Joints: They have fibrous tissue between bones fixing them together. Skull sutures, joints between teeth and mandible. Joints: Joints Cartilaginous Joints: Their main feature is that the bones are allowed slight movements in relation to each other due to fibro-cartilage cushion in between them. Pubic Symphysis , Joints between vertebrae cushioned by fibro-cartilaginous inter-vertebral discs. Synovial Joints: Synovial Joints They are freely movable compared to the other two types. Their main characteristics are: Have articular surfaces (that part of the bone that is in contact with the other bone) made of cartilage. Therefore they can with stand the weight of the body and provide s smooth surface for articulation Have a joint capsule : a fibrous sheath that covers the joint bones that protects the joint while allowing enough flexibility for the bones to move Presence of Intra-capsular and extra-capsular structures. Synovial Joints: Synovial Joints Their main characteristics are: Have a synovial membrane lining the inner surface of the capsule Synovial membrane lined by a layer of epithelial cells that secrete synovial fluid. It is thick sticky fluid of egg-white consistency that acts as a lubricant, provides nutrients and stability to the joint bones Types of Synovial Joints : Types of Synovial Joints Synovial Joints are classified according to: The range of movements they allow The shape of the articular surfaces of their bones There are several main types of synovial joints: Ball & Socket Joints Hinge Joints Gliding Joints Pivot Joints Condyloid Saddle Joints Types of Synovial Joints : Types of Synovial Joints Ball & Socket Joints: Shoulder and Hip Allows flexion, extension, abduction, adduction, rotation and circumduction Hinge Joints: Elbow, knee, ankle, inter-phalangeal joints of the limbs, joint between the atlas and the occipital bone Flexion and extension only Types of Synovial Joints : Types of Synovial Joints Gliding Joints: Sternoclavicular and Acromioclavicular joints, joints between carpal and tarsal bones articular surfaces only glide over each other Pivot Joints: Proximal and distal radio- ulnar joints, atals and oddontoid process of the axis Movement is only around one axis (ROTATION) Condyloid and Saddle Joints : the wrist, temporomandibular , metacarpophalangeal and metatarsophalangeal joints Movements along two axes: flexion, extension, adduction, abduction and circumduction Synovial Joints of the Body: Synovial Joints of the Body Shoulder and the Upper Limb Shoulder joint Elbow Joint Radio- Ulnar Joints (proximal and distal) Wrist Joints of the Hand and Fingers Pelvis and the Lower Limb Hip Joint Knee Joint Ankle Joint Joints of the foot and toes End of Unit 9 – Part A: End of Unit 9 – Part A

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