Skeletal System 2. The Axial Skeleton Consists of bones Three major regions Skull column cage

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1 Skeletal System 2 The Axial Skeleton Consists of bones Three major regions Skull column cage The Skull Two sets of bones 1. bones Enclose the brain in the cranial cavity Cranial (calvaria) Cranial : anterior, middle, and posterior cranial fossae Provide sites of attachment for head and neck muscles The Skull 2. bones Framework of face Cavities for special sense organs for sight,, and smell Openings for and passage Sties of attachment for and muscles of expression Cranial Bones bone Parietal bones (2) bone Temporal bones (2) bone Ethmoid bone Frontal Bone Anterior portion of Most of anterior cranial fossa Superior wall of

2 Contains air-filled sinus Parietal Bones and Major Associated Sutures Superior and lateral aspects of cranial vault Four sutures mark the articulations of parietal bones with frontal, occipital, and temporal bones: 1. suture between parietal bones and frontal bone 2. suture between right and left parietal bones 3. suture between parietal bones and occipital bone 4. (squamosal) sutures between and temporal bones on each side of skull Occipital Bone Most of skull s posterior wall and posterior cranial fossa with 1st vertebra Sites of attachment for the nuchae and many neck and back muscles Temporal Bones aspects of skull and parts of floor Four major regions Squamous Tympanic Petrous Sphenoid Bone Complex, bat-shaped bone bone Articulates with all other cranial bones Three pairs of processes Greater wings Lesser wings processes Ethmoid Bone skull bone Superior part of nasal septum, roof of nasal cavities Contributes to medial wall of orbits

3 Sutural Bones Tiny irregularly shaped bones that appear within sutures Facial Bones Mandible bones (maxillae) (2) bones (2) Nasal bones (2) bones (2) bones (2) Vomer Inferior nasal (2) Mandible Lower jaw Largest, strongest bone of face joint: only freely movable joint in skull Maxillary Bones Medially fused to form upper jaw and central portion of facial skeleton bones Articulate with all other facial bones except mandible Zygomatic Bones Cheekbones margins of orbits Nasal Bones and Lacrimal Bones Nasal bones Form of nose Lacrimal bones In medial walls of orbits fossa houses sac Palatine Bones and Vomer Palatine bones Posterior one-third of hard palate walls of the nasal cavity Small part of the orbits

4 Vomer Plow shaped Lower part of septum Inferior Nasal Conchae Form part of lateral walls of nasal cavity Orbits Encase eyes and glands Sites of attachment for eye muscles Formed by parts of bones (next slide) Nasal Cavity Roof, lateral walls, and floor formed by parts of four bones Ethmoid bones Maxillary bones Inferior nasal Nasal septum of bone and hyaline cartilage Ethmoid Vomer Anterior septal cartilage Paranasal Sinuses -lined, -filled spaces Lighten the skull Enhance of voice Found in frontal, sphenoid, ethmoid, and maxillary bones Hyoid Bone Not a bone of the skull Does not articulate directly with another bone Site of attachment for muscles of swallowing and speech Vertebral Column Transmits of trunk to limbs Surrounds and protects cord Flexible curved structure containing 26 irregular bones (vertebrae)

5 vertebrae (7) vertebrae of the neck vertebrae (12) vertebrae of the thoracic cage vertebrae (5) vertebra of the lower back bone inferior to the lumbar vertebrae terminus of vertebral column Vertebral Column: Curvatures Increase the resilience and flexibility of the spine Two posteriorly curvatures Cervical and lumbar Two posteriorly curvatures Thoracic and sacral Abnormal spine curvatures (abnormal lateral curve) (hunchback) (swayback) Ligaments and longitudinal ligaments From neck to sacrum flavum Connects adjacent vertebrae ligaments Connect each vertebra to those above and below Intervertebral Discs Cushionlike pad composed of two parts 1. Nucleus pulposus Inner nucleus that gives the disc its elasticity and compressibility 2. fibrosus Outer collar composed of collagen and fibrocartilage General Structure of Vertebrae Body or Anterior weight-bearing region arch Composed of pedicles and laminae that, along with centrum, enclose vertebral foramen Vertebral foramina Together make up vertebral canal for spinal cord

6 foramina Lateral openings between adjacent vertebrae for spinal nerves General Structure of Vertebrae Seven processes per vertebra: process projects posteriorly processes (2) project laterally Superior processes (2) protrude superiorly inferiorly articular processes (2) protrude inferiorly Cervical Vertebrae C1 to C7:, vertebrae C3 to C7 share the following features body processes are bifid (except C7) Large, triangular vertebral foramen foramen in each transverse process Cervical Vertebrae C1 ( ) and C2 ( ) have unique features Atlas (C1) No body or spinous process Consists of anterior and posterior arches, and two lateral masses Superior surfaces of lateral masses articulate with the occipital Cervical Vertebrae (C2) Dens projects superiorly into the arch of the atlas Dens is a pivot for the rotation of the atlas Thoracic Vertebrae T1 to T12 All articulate with ribs at facets and Long process Location of facets allows rotation of this area of spine Lumbar Vertebrae L1 to L5

7 Short, thick pedicles and Flat hatchet-shaped processes Orientation of facets locks lumbar vertebrae together so as to prevent rotation Sacrum and Coccyx Sacrum 5 fused (S1 S5) Forms posterior wall of pelvis with L5 superiorly, and with auricular surfaces of the hip bones laterally Coccyx Tailbone 3 5 fused vertebrae Articulates superiorly with sacrum Thoracic Cage Composed of vertebrae Sternum and their costal cartilages Functions Protects vital of thoracic cavity Supports girdle and upper limbs Provides attachment sites for many muscles, including intercostal muscles used during Sternum (Breastbone) Three fused bones Manubrium Articulates with and ribs 1 and 2 Body Articulates with costal cartilages of ribs 2 through 7 Xiphoid process Site of muscle attachment Not until ~ age 40 Ribs and Their Attachments pairs All attach posteriorly to thoracic vertebrae Pairs 1 through 7 True ( ) ribs

8 Attach directly to the sternum by individual costal cartilages Ribs and Their Attachments Pairs 8 through12 ribs Pairs 8 10 also called ribs Attach indirectly to by joining costal cartilage of rib above Pairs also called vertebral (floating) ribs No attachment to Structure of a Typical Rib Main parts: Head Articulates posteriorly with facets (demifacets) on bodies of two adjacent vertebrae Neck Tubercle Articulates posteriorly with transverse costal facet of same-numbered thoracic vertebra Shaft Appendicular Skeleton Bones of the limbs and their girdles girdle attaches the upper limbs to the body trunk girdle secures the lower limbs Pectoral Girdle (Shoulder Girdle) and the sca pulae Attach the upper limbs to the axial skeleton Provide attachment sites for muscles that move the upper limbs Clavicles (Collarbones) acromial ( ) end articulates with the scapula Cone-shaped sternal (medial) end articulates with the sternum Act as braces to hold the scapulae and arms out laterally Scapulae ( Blades) Situated on the dorsal surface of rib cage, between ribs 2 and 7 Flat and, with three borders and three angles Seven large, named according to location

9 The Upper Limb 30 bones form the skeletal framework of each upper limb Arm Humerus Forearm and ulna Hand 8 bones in the wrist 5 bones in the palm 14 in the fingers Humerus Largest, longest bone of upper limb Articulates with glenoid cavity of scapula Articulates with radius and ulna Bones of the Forearm Ulna bone in forearm Forms the major portion of the elbow joint with the humerus Radius bone in forearm Head articulates with of and with radial notch of ulna Interosseous membrane connects the radius and ulna along their entire length Hand: Carpus bones in two rows Proximal row Scaphoid, lunate, triquetrum, and pisiform proximally row Trapezium, trapezoid, capitate, and hamate distally Only and articulate with radius to form wrist joint Hand: Metacarpus and Phalanges Metacarpus metacarpal bones (#1 to #5) form the palm Phalanges Each finger (digit), except the thumb, has three phalanges

10 distal, middle, and proximal Fingers are numbered 1 5, beginning with the thumb ( ) Thumb has no middle phalanx Pelvic (Hip) Girdle Two hip bones (each also called bone or os coxae) Attach the lower limbs to the axial skeleton with strong ligaments Transmit weight of body to limbs Support pelvic organs Each hip bone consists of three fused bones: ilium, ischium, and pubis Together with the sacrum and the coccyx, these bones form the bony pelvis Hip Bone Three regions 1. Ilium region of the bone Auricular surface articulates with the sacrum (sacroiliac joint) 2. Ischium part of hip bone 3. Pubis Anterior portion of hip bone Midline pubic joint Comparison of Male and Female Pelves Female pelvis Adapted for childbearing True (inferior to pelvic brim) defines birth canal Cavity of the true pelvis is,, and has greater capacity Comparison of Male and Female Pelves Male pelvis Tilted forward Adapted for support of male s heavier build and stronger muscles Cavity of true pelvis is narrow and deep Comparison of Male and Female Pelves The Lower Limb Carries the weight of the body Subjected to exceptional forces

11 Three segments of the lower limb : femur : tibia and fibula : 7 tarsal bones in the ankle, 5 metatarsal bones in the metatarsus, and 14 phalanges in the toes Femur Largest and strongest bone in the body Articulates proximally with the of the hip and distally with the tibia and patella Bones of the Leg Tibia Medial leg bone Receives the weight of the body from the femur and transmits it to the foot Fibula Not weight bearing; no articulation with femur Site of muscle attachment Connected to tibia by membrane Articulates with tibia via proximal and distal joints Foot: Tarsals tarsal bones form the posterior half of the foot transfers most of the weight from the tibia to the calcaneus Other tarsal bones:,, and the medial,, and lateral cuneiforms Foot: Metatarsals and Phalanges Metatarsals: Five metatarsal bones (#1 to #5) Enlarged head of metatarsal 1 forms the ball of the foot Phalanges The 14 bones of the toes Each digit (except the hallux) has three phalanges Hallux has no middle phalanx Arches of the Foot Arches are maintained by interlocking foot bones, ligaments, and tendons Arches allow the foot to bear weight

12 Three arches longitudinal longitudinal Transverse Developmental Aspects: Fetal Skull Infant skull has more bones than the adult skull bones such as the mandible and frontal bones are unfused At birth, skull bones are connected by Fontanelles Unossified remnants of fibrous membranes between fetal skull bones Four fontanelles Anterior, posterior, mastoid, and sphenoid Developmental Aspects: Growth Rates At birth, the cranium is huge relative to the face At 9 months of age, cranium is _ adult size and are foreshortened but lengthen with age The arms and legs grow at a faster rate than the head and trunk, leading to adult proportions Developmental Aspects: Spinal Curvature Thoracic and sacral curvatures are obvious at birth These primary curvatures give the spine a C shape posteriorly Developmental Aspects: Spinal Curvature Secondary curvatures and lumbar convex anteriorly Appear as child develops (e.g., lifts head, learns to walk) Developmental Aspects: Old Age discs become thin, less hydrated, and less elastic Risk of disc increases Loss of stature by several centimeters is common by age 55 Costal cartilages ossify, causing the thorax to become rigid All bones lose mass