4.THE SKELETAL SYSTEM

• Clinical applications of the skeletal system include cleft palate and lip, cranial assessment of the newborn, abnormal spinal curvatures, herniated disc, and evolutionary medicine.
• The skeletal system consists of the axial skeleton and appendicular skeleton, which are further divided into the skull, auditory ossicles, hyoid bone, vertebral column, thoracic cage, upper limb, and lower limb and pelvic girdle.
• The number of bones in the skeletal system varies with age and from one person to another due to the development of sesamoid bones.
• Understanding skeletal anatomy is useful for studying the gross anatomy of other organ systems because many organs are named for their relationships to nearby bones.
• Knowledge of skeletal anatomy is also useful for understanding how the muscles produce body movements and for determining the positions, shapes, and processes of bones can serve as landmarks for clinicians in determining where to give an injection or record a pulse, what to look for in an X-ray, and how to perform physical therapy and other clinical procedures.
• The petrous 12 part of the skull can be seen in the cranial floor, where it resembles a little mountain range separating the middle cranial fossa from the posterior fossa.
• The tympanic 10 part of the skull is a small ring of bone that borders the opening of the external acoustic meatus (me-AY-tus), or ear canal, with a pointed spine on its inferior surface.
• The squamous 9 part of the skull is relatively flat and vertical, encircled by the squamous suture, and bears two prominent features: the zygomatic process, which extends anteriorly to form part of the zygomatic arch, and the mandibular fossa, a depression where the mandible articulates with the cranium.
• Severe swelling can force the brainstem out through the foramen magnum, usually with fatal consequences.
• The occipital bone continues anterior to the foramen magnum as a thick median plate, the basilar part.
• The occipital bone's most conspicuous feature, the foramen magnum, admits the spinal cord to the cranial cavity; the dura mater is attached to the rim of this foramen.
• The occipital bone forms the rear of the skull (occiput) and much of its base.
• Swelling of the brain in the cranium can put pressure on the brain and result in even more tissue damage.
• Meatus: A canal (external acoustic meatus of the ear).
• Fovea: A small pit (fovea capitis of the femur).
• Foramen: A hole through a bone, usually round (foramen magnum of the skull).
• Line: A slightly raised, elongated ridge (nuchal lines of the skull).
• Tuberosity: A rough elevated surface (tibial tuberosity).
• Fossa: A shallow, broad, or elongated basin (mandibular fossa).
• Canal: A tubular passage or tunnel in a bone (auditory canal of the skull).
• Crest: A narrow ridge (iliac crest of the pelvis).
• Trochanter: Two massive processes unique to the femur.
• Process: Any bony prominence (mastoid process of the skull).
• Tubercle: A small, rounded process (greater tubercle of the humerus).
• Epicondyle: An expanded region superior to a condyle (medial epicondyle of the femur).
• Condyle: A rounded knob that articulates with another bone (occipital condyles of the skull).
• Facet: A smooth, flat, slightly concave or convex articular surface (articular facets of the vertebrae).
• Sulcus: A groove for a tendon, nerve, or blood vessel (intertubercular sulcus of the humerus).
• Spine: A sharp, slender, or narrow process (mental spines of the mandible).
• Alveolus: A pit or socket (tooth socket).
• Sinus: An air-filled space in a bone (frontal sinus of the forehead).
• Head: The prominent expanded end of a bone, sometimes rounded (head of the femur).
• Protuberance: A bony outgrowth or protruding part (mental protuberance of the chin).
• Fissure: A slit through a bone (orbital fissures behind the eye).
• The Frontal Bone extends from the forehead back to a prominent coronal suture, which crosses the crown of the head from right to left and joins the frontal bone to the parietal bones.
• The cranial bones are those that enclose the brain; collectively, they compose the cranium.
• The cranium consists of two major parts: the calvaria (skullcap) and the base (floor).
• The foramen magnum is the opening where the spinal cord meets the brain.
• The dura mater is the thickest and toughest of the meninges and is pressed against the inside of the cranium in most places and firmly attached to it at a few points.
• The base of the cranial cavity exhibits three paired depressions called cranial fossae that correspond to the contour of the inferior surface of the brain.