The Skeleton Part A 7

The Axial Skeleton Eighty bones segregated into three regions Skull Vertebral column Bony thorax

The Skull The skull Cranium Facial bones Eight cranial bones – 2 parietal, 2 temporal, frontal, occipital, sphenoid, and ethmoid Facial bones Fourteen bones 2 maxillae, 2 zygomatics, 2 nasals, 2 lacrimals, 2 palatines, and 2 inferior conchae mandible and vomer are unpaired

Skull: Anterior View Figure 7.2a

Skull: Lateral View Figure 7.3a

Skull: Posterior View Figure 7.2b

Inferior Portion of the Skull Figure 7.4a

Paranasal Sinuses Figure 7.11

Vertebral Column 26 irregular bones 7 Cervical vertebrae 12 Thoracic vertebrae 5 Lumbar vertebrae Sacrum – 5 fused bones Coccyx – 4 fused bones

Vertebral Column: Ligaments Anterior (ventral) and posterior (dorsal) longitudinal ligaments Short ligaments connect adjoining vertebrae together

General Structure of Vertebrae Figure 7.15

Vertebral Column: Intervertebral Discs Nucleus pulposus – inner gelatinous region Annulus fibrosus – collar of collagen and fibrocartilage

Cervical Vertebrae: The Atlas (C1) Figure 7.16a, b

Cervical Vertebrae: The Axis (C2) Figure 7.16c

Cervical Vertebrae Figure 7.17a

Sacrum and Coccyx: Posterior (dorsal) View Figure 7.18b

Thorax (Thoracic Cage) The thoracic cage Dorsal - thoracic vertebrae Laterally - ribs Ventral - sternum and costal cartilages Functions Protective cage around the heart, lungs, and great blood vessels Supports the pectoral girdle and upper limbs Attachment sites for neck, back, chest, and shoulder muscles Intercostal muscles lift and depress the thorax for breathing

Thorax: Sternum Fusion of three bones manubrium, sternal body, xiphoid process

Thorax: Ribs 12 pairs All attached dorsally to the thoracic vertebrae Vertebrosternal ribs –attach to sternum via costal cartilages – “true ribs” Vertebrochondral ribs - attach to costal cartilage of rib 7 – “false ribs” Vertebral ribs - no ventral attachment – “floating ribs”

Pectoral Girdle (Shoulders) Figure 7.22a

Scapulae (Shoulder Blades) Figure 7.22d, e

The Upper Limb The proximal arm (brachium), distal arm (forearm; antebrachium), and hand (manus) Thirty-seven bones

Humerus of the Proximal Arm Figure 7.23

Radia and Ulna of the Distal Arm (Forearm) Figure 7.24

Manus (Hand) 14 5 8 Figure 7.26a

Pelvic Girdle (Hips) Os coxae - coxal bones Coxal bone is fusion of 3 bones – ilium, ischium, pubis Os coxae, sacrum and coccyx, form the bony pelvis

Os coxa: Lateral View Obturator foramen

Comparison of Male and Female Pelvic Structure Female pelvis Tilted forward, adapted for childbearing Pubic arch obtuse angle Cavity of the true pelvis is broad, shallow, Male pelvis Less tilted forward Pubic arch acute angle Cavity of true pelvis is narrow and deep

The Lower Limb the thigh (proximal), leg (distal), and foot

Femur Figure 7.28b

Tibia and Fibula Figure 7.29

Foot 14 5 7 Figure 7.31b, c

Developmental Aspects: Fetal Skull At birth, fetal skull bones are incomplete and connected by fontanels Fontanels Unossified remnants of fibrous membranes between bones anterior, posterior mastoid sphenoid Figure 7.33

Developmental Aspects: Growth Rates At birth, the cranium is huge relative to the face Mandible and maxilla are foreshortened but lengthen with age The arms and legs grow at a faster rate than the head and trunk, leading to adult proportions Figure 7.34