Types of Ossification The first type is intramembranous ossification , in which dense connective tissue membranes are replaced by deposits of inorganic calcium salts, thus forming bone. The membrane itself will eventually become the periosteum of the mature bone. Underneath the periosteum will be compact bone with an inner core of spongy or cancellous bone. Only the bones of the cranium or skull form by this process.
Because complete ossification in this way does not occur until a few months after birth, one can feel these membranes on the top of a baby’s skull as the soft spot or fontanelle (fontah- NELL ). This allows the baby’s skull to move slightly as it moves through the birth canal.
The other bones of the body are formed by the second process called endochondral (en-doh- KON -dral) ossification This is the process in which cartilage is the environment in which the bone cells develop (endo = inside, chondro = cartilage). As the organic matrix becomes synthesized, the osteoblast becomes completely surrounded by the bone matrix and develops into a mature bone cell or osteocyte. Both types of ossification result in compact and cancellous bone.
Cranium- rounded chamber that encloses the brain - composed of 8 distinct cranial bones Frontal bone- forms the forehead 2 parietal bones- form most of the top and sidewalls of the cranium 2 temporal bones- form part of the sides and some of the base of the skull Ethmoid bone- a light, fragile bone located between the eyes
Sphenoid bone- when seen from above resembles a bat with its wings extended - forms the base of the cranium behind the eyes Occipital bone- forms the back and a part of the base of the skull Foramen magnum- located at the base of the occipital bone - large opening through which the spinal cord communicates with the brain
Foramen Magnum Hypoglossal canal Jugular Foramen
Facial Bones- composed of 14 bones Mandible(lower jaw bone) - largest and strongest bone of the face - the only movable bone of the skull 2 maxillae - fuse in the midline to form the upper jaw bone 2 zygomatic bone- form the prominences of the cheek
2 slender nasal bones- forms the bridge of the nose 2 lacrimal bones- lie near the inside corner of the eye in the front part of the medial wall of the orbital cavity Vomer- shaped like the blade of the plow - forms the lower part of the nasal septum
Paired palatine bones- form the back part of the hard palate 2 inferior nasal conchae- extend horizontally along the lateral wall of the nasal cavities
Temporomandibular joint Each ramus of the mandible has a posterior condylar process that articulates with the mandibular fossa and articular tubercle of the temporal bone to form the TMJ
Sutures of the Skull 1. Coronal suture - articulates the frontal bone with the two parietal bones. 2. Sagittal suture - articulates the two parietal bones. 3. Squamous ( squamoparietal ) suture - articulates the parietal bone and the squamous part of the temporal bone. 4. Lambdoid suture - articulates the two parietal bones with the occipital bone.
Junctions of the cranial sutures a. Lambda - Intersection of the lambdoid and sagittal sutures. b. Bregma - Intersection of the sagittal and coronal sutures. c. Pterion – the junction of the frontal, parietal, and temporal bones and the greater wing of the sphenoid bone. d. Asterion - at the junction of the parietal, occipital, and temporal (mastoid part) bones. e. Nasion -a point on the middle of the nasofrontal suture (intersection of the frontal and two nasal bones). f. Inion - most prominent point of the external occipital protuberance, which is used as a fixed point in craniometry.
What is the weakest point of the skull? Pterion What happens to the anterior and posterior fontanelles? Anterior fontanelle – close at 18-24 mo – bregma Posterior fontanelle – close at 2 mo - lambda
Bones of the Vertebral Column: Cervical vertebrae= 7 Located in the neck Atlas - 1 st vertebra, supports the head, when one nods the head, the skull rocks on the atlas Axis- the second cervical vertebra - serves as a pivot when the head is turned
Thoracic vertebrae= 12 - located in the chest Lumbar vertebrae= 5 Sacral vertebrae -5 separate bones in the child, fuse to form single bone called Sacrum in the adult
Coccyx(tail bone) -consists of four or five tiny bones in the child -these fuse to form a single bone in the adult
Atlanto -axial joint The articulation formed between the anterior arch of the atlas (C1) and dens of the axis (C2), and between their articular facets
Normal Curvatures of the Spine Primary curvatures Spinal curvatures of the thoracic and sacral regions Present from birth Secondary curvatures Spinal curvatures of the cervical and lumbar regions Develop after birth
Sternoclavicular joint Lateral to the suprasternal notch are clavicular notches that articulate with the medial ends of the clavicles to form the sternoclavicular joints
Acromioclavicular joint The broad, flat, lateral end, the acromial end of the clavicle articulates with the acromion of the scapula to form the acromioclavicular joint
Glenohumeral joint Inferior to the acromion is a shallow depression, the glenoid cavity, that accepts the head of the humerus (arm bone) to form the glenohumeral (shoulder) joint
Elbow joint The ulna and radius articulate with the humerus at the elbow joint. The articulation occurs in two places: where the head of the radius articulates with the capitulum of the humerus, and where the trochlear notch of the ulna articulates with the trochlea of the humerus.
Bones of the Pelvic Girdle The total weight of the upper body rests on the pelvis Protects several organs Reproductive organs Urinary bladder Part of the large intestine
Tibiofemoral (Knee) Joint The proximal end of the tibia is expanded into a lateral condyle and a medial condyle. These articulate with the condyles of the femur to form the lateral and medial tibiofemoral (knee) joints.
Which bone of the lower limb is not weight-bearing? Fibula Which bone is a commonly used in bone grafting? Fibula
What is largest and strongest tarsal bone? Calcaneus What is the most superior tarsal bone? Talus
Talocrural (Ankle) Joint The talus is the only bone of the foot that articulates with the fibula and tibia. It articulates on one side with the medial malleolus of the tibia and on the other side with the lateral malleolus of the fibula. These articulations form the talocrural (ankle) joint.
Types of Synovial Joint Based on Shape Plane joint- articular surfaces are flat - only short gliding movements are allowed - movements are nonaxial- gliding does not involve rotation around any axis ex. Intercarpal joints of the wrist
Hinge joint- permits only back and forth movements - cylindrical end of one bone fits into though- shaped surface on another bone - uniaxial( allow movement around one axis only) ex. Elbow joint, ankle joint, joints between phalanges of the finger, knee joint
Pivot joint- the rounded end of one bone fits into a sleeve or ring of bone - uniaxial (can turn only around its long axis) ex. Proximal radioulnar joint, atlanto -axial joint
Condylar joint (knuckle-like) - the egg-shaped articular surface of one bone fits into an oval concavity in another - allow moving bone to travel from side to side and back and forth, but cannot rotate around its long axis - biaxial ex. Knuckle (metacarpophalangeal) joints
Saddle joints- each articular surface has both convex and concave areas - biaxial ex. Carpometacarpal joints in the thumb
Ball-and-socket joint - the spherical head of one bone fits into a round socket in another - multiaxial joints (allow movement in all axes including rotation) - the most freely moving synovial joints ex. Shoulder, hip