The Axial Skeleton forms the longitudinal axis of the body The Axial Skeleton forms the longitudinal axis of the body. It is divided into three parts Skull Vertebral column Bony thorax

Cranium (eight large flat bones) The skull consists of two sets of bones, which are joined by sutures. Only the mandible is attached by a freely movable joint. Cranium (eight large flat bones) Frontal, Parietal(2), Temporal(2), Occipital, Sphenoid, Ethmoid Facial bones (all paired except mandible and vomer) Paired Maxilla, Palatine, Zygomatic, Lacrimal, Nasal, and Inferior Nasal Conchae and Single Mandible and Vomer(plow)

The Fetal Skull The fetal skull is large compared to the infant’s total body length Fontanels—fibrous membranes connecting the cranial bones Allow the brain to grow Convert to bone within 24 months after birth

Skeletal Changes Throughout Life Figure 5.33a

Paranasal Sinuses The Paranasal Sinuses are hollow portions of bones surrounding the nasal cavity Functions of paranasal sinuses Lighten the skull Give resonance and amplification to voice

Serves as a moveable base for the tongue Aids in swallowing and speech The Hyoid bone is the only bone that does not articulate with another bone-it is held into place by thyroid ligaments. Serves as a moveable base for the tongue Aids in swallowing and speech Notice the bruising around the neck area. The appearance of finger indentations indicate manual strangulation. The impression was confirmed by finding bruising deep in the neck, along with a fracture of the hyoid bone.

The Vertebral Column Each vertebrae is given a name according to its location There are 24 single vertebral bones separated by intervertebral discs Seven cervical vertebrae are in the neck (C1-C7) Twelve thoracic vertebrae are in the chest region (T1-T12) Five lumbar vertebrae are associated with the lower back (L1-L5)

The Vertebral Column The remaining nine vertebrae fuse to form two composite bones Sacrum Coccyx (tailbone)

Sacrum and Coccyx Sacrum Coccyx Formed by the fusion of five vertebrae Formed from the fusion of three to five vertebrae “Tailbone,” or remnant of a tail that other vertebrates have

The spine has a normal curvature Primary curvatures are the spinal curvatures of the thoracic and sacral regions Present from birth Secondary curvatures are the spinal curvatures of the cervical and lumbar regions Develop after birth (cervical with head raising and lumbar with walking)

Abnormal Spinal Curvatures of the Vertebral Column Scoliosis- “crooked”-side to side curvature-causes multifactorial Kyphosis-”hunchback” causes include trauma “slouching”, osteoporosis with compression fractures. Lordosis “swayback” an inward curvature of the vertebrae usually caused by differing anterior and posterior disc thickness

The Bony Thorax forms a cage to protect major organs The Bony Thorax forms a cage to protect major organs. It consists of three parts Sternum Ribs True ribs (pairs 1–7 attached to sternum) False ribs (pairs 8–12) Floating ribs (pairs 11–12) Thoracic vertebrae

The Appendicular Skeleton is composed of 126 bones Limbs (appendages) Pectoral girdle Pelvic girdle

The Pectoral (shoulder) Girdle is composed of two bones, which allow the upper limb to have exceptionally free movement Clavicle—collarbone (acts as a brace to hold arm away from thorax and prevents shoulder dislocation) Scapula—shoulder blade (provides exceptional range of motion for the arm)

Bones of the Upper Limbs Humerus Forms the upper arm Single bone

Bones of the Upper Limbs The forearm has two bones Ulna Medial bone in anatomical position (pinky side) Radius Lateral bone in anatomical position (thumb side)

Bones of the Upper Limbs The hand (27 bones) Carpals—wrist Metacarpals—palm Phalanges—fingers

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