The Skeletal System PDF

© 2018 Pearson Education, Inc.  The Skeletal System ▪ Parts of the skeletal system ▪ Bones (skeleton) ▪ Joints ▪ Cartilages ▪ Ligaments ▪ Two subdivisions of the skeleton 1. Axial skeleton 2. Appendicular s...

© 2018 Pearson Education, Inc.  The Skeletal System ▪ Parts of the skeletal system ▪ Bones (skeleton) ▪ Joints ▪ Cartilages ▪ Ligaments ▪ Two subdivisions of the skeleton 1. Axial skeleton 2. Appendicular skeleton © 2018 Pearson Education, Inc.  Functions of the Bones ▪ Support the body ▪ Protect soft organs ▪ Skull and vertebrae protect brain and spinal cord ▪ Rib cage protects thoracic cavity organs ▪ Attached skeletal muscles allow movement ▪ Store minerals and fats ▪ Calcium and phosphorus ▪ Fat in the internal marrow cavity ▪ Blood cell formation (hematopoiesis) © 2018 Pearson Education, Inc.  Classification of Bones ▪ The adult skeleton has 206 bones ▪ Two basic types of osseous (bone) tissue 1. Compact bone ▪ Dense, smooth, and homogeneous 2. Spongy bone ▪ Small needlelike pieces of bone ▪ Many open spaces © 2018 Pearson Education, Inc. Figure 5.1 Flat bones consist of a layer of spongy bone sandwiched between two thin layers of compact bone. Spongy bone Compact bone © 2018 Pearson Education, Inc.  Classification of Bone ▪ Bones are classified on the basis of shape into four groups ▪ Long ▪ Flat ▪ Short ▪ Irregular © 2018 Pearson Education, Inc. Figure 5.2 Classification of bones on the basis of shape. (b) Flat bone (sternum) (a) Long bone (humerus) (d) Irregular bone (vertebra), right lateral (c) Short bone view (talus) © 2018 Pearson Education, Inc.  Classification of Bones ▪ Long bones ▪ Typically longer than they are wide ▪ Shaft with enlarged ends ▪ Contain mostly compact bone; spongy bone at ends ▪ All of the bones of the limbs (except wrist, ankle, and kneecap bones) are long bones ▪ Examples: ▪ Femur ▪ Humerus © 2018 Pearson Education, Inc. Figure 5.2a Classification of bones on the basis of shape. (a) Long bone (humerus) © 2018 Pearson Education, Inc.  Classification of Bones ▪ Flat bones ▪ Thin, flattened, and usually curved ▪ Two thin layers of compact bone sandwich a layer of spongy bone between them ▪ Examples: ▪ Most bones of the skull ▪ Ribs ▪ Sternum © 2018 Pearson Education, Inc. Figure 5.2b Classification of bones on the basis of shape. (b) Flat bone (sternum) © 2018 Pearson Education, Inc.  Classification of Bones ▪ Short bones ▪ Generally cube-shaped ▪ Contain mostly spongy bone with an outer layer of compact bone ▪ Sesamoid bones are a type of short bone that form within tendons (patella) ▪ Examples: ▪ Carpals (wrist bones) ▪ Tarsals (ankle bones) © 2018 Pearson Education, Inc. Figure 5.2c Classification of bones on the basis of shape. (c) Short bone (talus) © 2018 Pearson Education, Inc.  Classification of Bones ▪ Irregular bones ▪ Irregular shape ▪ Do not fit into other bone classification categories ▪ Examples: ▪ Vertebrae ▪ Hip bones © 2018 Pearson Education, Inc. Figure 5.2d Classification of bones on the basis of shape. (d) Irregular bone (vertebra), right lateral view © 2018 Pearson Education, Inc.  Structure of Bone ▪ Long bone anatomy ▪ Diaphysis (shaft) ▪ Makes up most of bone’s length ▪ Composed of compact bone ▪ Periosteum ▪ Outside covering of the diaphysis ▪ Fibrous connective tissue membrane ▪ Perforating (Sharpey’s) fibers secure periosteum to underlying bone © 2018 Pearson Education, Inc. Figure 5.3a The structure of a long bone (humerus of arm). Articular cartilage Proximal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum) Diaphysis Distal epiphysis (a) © 2018 Pearson Education, Inc. Figure 5.3c The structure of a long bone (humerus of arm). Endosteum Yellow bone marrow Compact bone Periosteum Perforating (Sharpey’s) fibers Nutrient arteries (c) © 2018 Pearson Education, Inc.  Structure of Bone ▪ Long bone anatomy (continued) ▪ Epiphysis (ends) ▪ Composed mostly of spongy bone enclosed by thin layer of compact bone ▪ Articular cartilage ▪ Covers the external surface of the epiphyses ▪ Made of hyaline cartilage ▪ Decreases friction at joint surfaces © 2018 Pearson Education, Inc. Figure 5.3b The structure of a long bone (humerus of arm). Articular cartilage Compact bone Spongy bone (b) © 2018 Pearson Education, Inc.  Structure of Bone ▪ Long bone anatomy (continued) ▪ Epiphyseal line ▪ Remnant of the epiphyseal plate ▪ Seen in adult bones ▪ Epiphyseal plate ▪ Flat plate of hyaline cartilage seen in young, growing bone ▪ Causes lengthwise growth of a long bone © 2018 Pearson Education, Inc. Figure 5.3a The structure of a long bone (humerus of arm). Articular cartilage Proximal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum) Diaphysis Distal epiphysis (a) © 2018 Pearson Education, Inc.  Structure of Bone ▪ Long bone anatomy (continued) ▪ Endosteum ▪ Lines the inner surface of the shaft ▪ Made of connective tissue ▪ Medullary cavity ▪ Cavity inside the shaft ▪ Contains yellow marrow (mostly fat) in adults ▪ Contains red marrow for blood cell formation in infants until age 6 or 7 © 2018 Pearson Education, Inc. Figure 5.3a The structure of a long bone (humerus of arm). Articular cartilage Proximal epiphysis Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum) Diaphysis Distal epiphysis (a) © 2018 Pearson Education, Inc.  Structure of Bone ▪ Bone markings ▪ Sites of attachments for muscles, tendons, and ligaments ▪ Passages for nerves and blood vessels ▪ Categories of bone markings ▪ Projections or processes—grow out from the bone surface ▪ Terms often begin with “T” ▪ Depressions or cavities—indentations ▪ Terms often begin with “F” © 2018 Pearson Education, Inc. Table 5.1 Bone Markings (1 of 3) © 2018 Pearson Education, Inc. Table 5.1 Bone Markings (2 of 3) © 2018 Pearson Education, Inc. Table 5.1 Bone Markings (3 of 3) © 2018 Pearson Education, Inc.  Structure of Bone ▪ Microscopic anatomy of spongy bone ▪ Composed of small, needlelike pieces of bone called trabeculae and open spaces ▪ Open spaces are filled by marrow, blood vessels, and nerves © 2018 Pearson Education, Inc. Figure 5.4a Microscopic structure of bone. Trabeculae of spongy bone Osteon (Haversian Perforating system) (Volkmann’s) canal Blood vessel continues into medullary cavity containing marrow Blood vessel Lamellae Compact bone Central (Haversian) canal Perforating (Sharpey’s) fibers Periosteum Periosteal blood vessel (a ) © 2018 Pearson Education, Inc.  Structure of Bone ▪ Microscopic anatomy of compact bone ▪ Osteocytes ▪ Mature bone cells situated in bone matrix ▪ Lacunae ▪ Cavities in bone matrix that house osteocytes ▪ Lamellae ▪ Concentric circles of lacunae situated around the central (Haversian) canal © 2018 Pearson Education, Inc.  Structure of Bone ▪ Microscopic anatomy of compact bone (continued) ▪ Central (Haversian) canal ▪ Opening in the center of an osteon (Haversian system) ▪ Runs lengthwise through bone ▪ Carries blood vessels and nerves ▪ Osteon (Haversian system) ▪ A unit of bone containing central canal and matrix rings ▪ Structural and functional unit of compact bone © 2018 Pearson Education, Inc. Figure 5.4b Microscopic structure of bone. Lamella Osteocyte Canaliculus Lacuna Central Bone matrix (Haversian) canal (b) © 2018 Pearson Education, Inc. Figure 5.4c Microscopic structure of bone. Osteon Interstitial lamellae Lacuna Central (Haversian) canal (c) © 2018 Pearson Education, Inc.  Structure of Bone ▪ Microscopic anatomy of compact bone (continued) ▪ Canaliculi ▪ Tiny canals ▪ Radiate from the central canal to lacunae ▪ Form a transport system connecting all bone cells to a nutrient supply ▪ Perforating (Volkmann’s) canal ▪ Canal perpendicular to the central canal ▪ Carries blood vessels and nerves © 2018 Pearson Education, Inc. Figure 5.4b Microscopic structure of bone. Lamella Osteocyte Canaliculus Lacuna Central Bone matrix (Haversian) canal (b) © 2018 Pearson Education, Inc.  Bone Fractures ▪ Fracture: break in a bone ▪ Types of bone fractures ▪ Closed (simple) fracture is a break that does not penetrate the skin ▪ Open (compound) fracture is a broken bone that penetrates through the skin © 2018 Pearson Education, Inc.  Bone Fractures ▪ Bone fractures are treated by reduction and immobilization ▪ Closed reduction: bones are manually coaxed into position by physician’s hands ▪ Open reduction: bones are secured with pins or wires during surgery ▪ Healing time is 6–8 weeks © 2018 Pearson Education, Inc.  Bone Fractures ▪ Repair of bone fractures involves four major events ▪ Hematoma (blood-filled swelling, or bruise) is formed ▪ Fibrocartilage callus forms ▪ Cartilage matrix, bony matrix, collagen fibers splint the broken bone ▪ Bony callus replaces the fibrocartilage callus ▪ Osteoblasts and osteoclasts migrate in ▪ Bone remodeling occurs in response to mechanical stresses © 2018 Pearson Education, Inc. Figure 5.7 Stages in the healing of a bone fracture. Hematoma External Bony callus callus of spongy bone New Internal blood vessels Healed callus fracture (fibrous Spongy tissue and bone cartilage) trabecula 1 Hematoma 2 Fibrocartilage 3 Bony 4 Bone forms. callus forms. callus remodeling forms. occurs. © 2018 Pearson Education, Inc. Table 5.2 Common Types of Fractures © 2018 Pearson Education, Inc.  Axial Skeleton ▪ Forms the longitudinal axis of the body ▪ Divided into three parts 1. Skull 2. Vertebral column 3. Bony thorax © 2018 Pearson Education, Inc. Figure 5.8a The human skeleton. Cranium Skul Facial bones l Clavicle Thoracic Scapula cage Sternum (ribs and Rib sternum) Humerus Vertebra Vertebra Radius l Ulna Sacrum column Carpals Phalanges Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges (a) Anterior © 2018 Pearson Education, Inc. view  Skull ▪ Two sets of bones form the skull 1. Cranium bones enclose the brain 2. Facial bones ▪ Hold eyes in anterior position ▪ Allow facial muscles to express feelings ▪ Bones are joined by sutures ▪ Only the mandible is attached by a freely movable joint © 2018 Pearson Education, Inc.  Skull ▪ 8 cranial bones protect the brain 1 Frontal bone 2 Occipital bone 3 Ethmoid bone 4 Sphenoid bone 5, 6 Parietal bones (pair) 7, 8 Temporal bones (pair) © 2018 Pearson Education, Inc.  Skull ▪ 14 facial bones 1, 2 Maxillae (pair) 3, 4 Palatine bones (pair) 5, 6 Lacrimal bones (pair) 7, 8 Zygomatic bones (pair) 9, 10 Nasal bones (pair) 11 Vomer bone 12, 13 Inferior nasal conchae (pair) 14 Mandible © 2018 Pearson Education, Inc. Figure 5.9 Human skull, lateral view. Coronal suture Frontal bone Parietal bone Sphenoid bone Temporal bone Ethmoid bone Lambdoid Lacrimal bone suture Squamous suture Nasal bone Occipital bone Zygomatic process Zygomatic bone Maxilla External acoustic meatus Mastoid process Alveolar processes Styloid process Mandible (body) Mental foramen Mandibular ramus © 2018 Pearson Education, Inc.  Skull ▪ Hyoid bone ▪ Closely related to mandible and temporal bones ▪ The only bone that does not articulate with another bone ▪ Serves as a movable base for the tongue ▪ Aids in swallowing and speech © 2018 Pearson Education, Inc. Figure 5.14 Anatomical location and structure of the hyoid bone. Greater horn Lesser horn Body © 2018 Pearson Education, Inc.  Vertebral Column (Spine) ▪ Vertebral column provides axial support ▪ Extends from skull to the pelvis ▪ 26 vertebral bones are separated by intervertebral discs ▪ 7 cervical vertebrae are in the neck ▪ 12 thoracic vertebrae are in the chest region ▪ 5 lumbar vertebrae are associated with the lower back ▪ Sacrum (formed by fusion of 5 vertebrae) ▪ Coccyx (formed by fusion of 3–5 vertebrae) © 2018 Pearson Education, Inc. Figure 5.15 The vertebral column. Anterior Posterior 1st cervical vertebra (atlas) Cervical curvature 2nd cervical (concave) 7 vertebrae, vertebra (axis) C1 – C7 1st thoracic vertebra Transverse process Spinous Thoracic curvature process (convex) 12 vertebrae, T1 – T12 Intervertebral disc Intervertebral foramen 1st lumbar vertebra Lumbar curvature (concave) 5 vertebrae, L1 – L5 Sacral curvature (convex) 5 fused vertebrae Coccyx 4 fused vertebrae © 2018 Pearson Education, Inc.  Vertebral Column (Spine) ▪ Primary curvatures ▪ Spinal curvatures of the thoracic and sacral regions ▪ Present from birth ▪ Form a C-shaped curvature in newborns ▪ Secondary curvatures ▪ Spinal curvatures of the cervical and lumbar regions ▪ Develop after birth ▪ Form an S-shaped curvature in adults © 2018 Pearson Education, Inc. Figure 5.16 The C-shaped spine typical of a newborn. © 2018 Pearson Education, Inc.  Vertebral Column (Spine) ▪ Parts of a typical vertebra ▪ Body (centrum) ▪ Vertebral arch ▪ Pedicle ▪ Lamina ▪ Vertebral foramen ▪ Transverse processes ▪ Spinous process ▪ Superior and inferior articular processes © 2018 Pearson Education, Inc. Figure 5.17 A typical vertebra, superior view. Posterior Lamina Vertebral arch Transverse Spinous process process Superior articular process and facet Pedicle Vertebral foramen Body Anterio © 2018 Pearson Education, Inc. r Figure 5.18a Regional characteristics of vertebrae. (a) ATLAS AND AXIS Transverse Posterior process arch Anterior arch Superior view of atlas (C 1) Spinous Transverse process process Facet on superior articular process Dens Body Superior view of axis (C 2) © 2018 Pearson Education, Inc. Figure 5.19 Sacrum and coccyx, posterior view. Superior Auricular Ala Sacral articular surface canal process Body Median Sacrum sacral crest Posterior sacral foramina Sacral Coccyx hiatus © 2018 Pearson Education, Inc.  Thoracic Cage ▪ Bony thorax, or thoracic cage, protects organs of the thoracic cavity ▪ Consists of three parts 1. Sternum 2. Ribs ▪ True ribs (pairs 1–7) ▪ False ribs (pairs 8–12) ▪ Floating ribs (pairs 11–12) 3. Thoracic vertebrae © 2018 Pearson Education, Inc. Figure 5.20a The bony thorax (thoracic cage). T1 vertebra Jugular notch Clavicular notch Manubrium Sternal angle Body Xiphisternal Sternum True joint ribs Xiphoid (1–7) process False ribs (8–12) Intercostal spaces L1 Floating vertebra Costal cartilage ribs (11, 12) (a) © 2018 Pearson Education, Inc.  Appendicular Skeleton ▪ Composed of 126 bones ▪ Limbs (appendages) ▪ Pectoral girdle ▪ Pelvic girdle © 2018 Pearson Education, Inc. Figure 5.8a The human skeleton. Cranium Skul Facial bones l Clavicle Thoracic Scapula cage Sternum (ribs and Rib sternum) Humerus Vertebra Vertebra Radius l Ulna Sacrum column Carpals Phalanges Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges (a) Anterior © 2018 Pearson Education, Inc. view  Bones of the Shoulder Girdle ▪ Also called pectoral girdle ▪ Composed of two bones that attach the upper limb to the axial skeletal 1. Clavicle 2. Scapula ▪ Light, poorly reinforced girdle ▪ Allows the upper limb a exceptional flexibility © 2018 Pearson Education, Inc. Figure 5.21a Bones of the shoulder girdle. Acromio- clavicular Clavicle joint Scapula (a) Articulated right shoulder (pectoral) girdle showing the relationship to © 2018 Pearson Education, Inc. bones of the thorax and sternum Figure 5.21c Bones of the shoulder girdle. Coracoid process Suprascapular notch Superior Acromion angle Glenoid cavity at lateral angle Spine Medial border Lateral border (c) Right scapula, posterior aspect © 2018 Pearson Education, Inc.  Bones of the Upper Limbs ▪ Humerus ▪ Forms the arm ▪ Single bone ▪ Proximal end articulation ▪ Head articulates with the glenoid cavity of the scapula ▪ Distal end articulation ▪ Trochlea and capitulum articulate with the bones of the forearm © 2018 Pearson Education, Inc. Figure 5.22a Bones of the right arm and forearm. Greater Head of tubercle humerus Lesser tubercle Anatomical neck Intertubercular sulcus Deltoid tuberosity Radial fossa Medial epicondyle Coronoid fossa Capitulum Trochlea (a) © 2018 Pearson Education, Inc.  Bones of the Upper Limbs ▪ The forearm has two bones 1. Ulna—medial bone in anatomical position ▪ Proximal end articulation ▪ Coronoid process and olecranon articulate with the humerus 2. Radius—lateral bone in anatomical position ▪ Proximal end articulation ▪ Head articulates with the capitulum of the humerus © 2018 Pearson Education, Inc. Figure 5.22c Bones of the right arm and forearm. Trochlear notch Olecranon Head Coronoid process Neck Radial Proximal tuberosity radioulnar joint Radius Ulna Inter- osseous membrane Radial Ulnar styloid Distal styloid process radioulnar process joint (c) © 2018 Pearson Education, Inc.  Bones of the Upper Limbs ▪ Hand ▪ Carpals—wrist bones ▪ 8 bones arranged in two rows of 4 bones in each hand ▪ Metacarpals—palm bones ▪ 5 per hand ▪ Phalanges—fingers and thumb ▪ 14 phalanges in each hand ▪ In each finger, there are 3 bones ▪ In the thumb, there are only 2 bones © 2018 Pearson Education, Inc. Figure 5.23 Bones of the right hand, anterior view. Distal Middle Phalanges (fingers) Proximal 4 3 2 Metacarpals 5 (palm) 1 Hamate Trapezium Carpals Pisiform Trapezoid (wrist) Triquetrum Scaphoid Lunate Capitate Ulna Radius © 2018 Pearson Education, Inc.  Bones of the Pelvic Girdle ▪ Formed by two coxal (ossa coxae) bones ▪ Composed of three pairs of fused bones 1. Ilium 2. Ischium 3. Pubis ▪ Pelvic girdle = two coxal bones, sacrum ▪ Pelvis = two coxal bones, sacrum, coccyx © 2018 Pearson Education, Inc.  Bones of the Pelvic Girdle ▪ The total weight of the upper body rests on the pelvis ▪ Pelvis protects several organs ▪ Reproductive organs ▪ Urinary bladder ▪ Part of the large intestine © 2018 Pearson Education, Inc. Figure 5.24a The bony pelvis. Iliac crest Sacroiliac joint lliu m Coxal Sacru bone Pelvic brim m (or hip bone) Pubi Coccy Ischial spine s x Acetabulum Ischiu Pubic symphysis m Pubic arch (a ) © 2018 Pearson Education, Inc.  Bones of the Lower Limbs ▪ Femur—thigh bone ▪ The heaviest, strongest bone in the body ▪ Proximal end articulation ▪ Head articulates with the acetabulum of the coxal (hip) bone ▪ Distal end articulation ▪ Lateral and medial condyles articulate with the tibia in the lower leg © 2018 Pearson Education, Inc. Figure 5.25a Bones of the right thigh and leg. Surgical neck Head Inter- trochanteric Lesser trochanter line Lateral epicondyle Medial epicondyle Patellar surface (a) © 2018 Pearson Education, Inc.  Bones of the Lower Limbs ▪ The lower leg has two bones 1. Tibia—shinbone; larger and medially oriented ▪ Proximal end articulation ▪ Medial and lateral condyles articulate with the femur to form the knee joint ▪ Distal end articulation ▪ Medial malleolus forms the inner part of the ankle 2. Fibula—thin and sticklike; lateral to the tibia ▪ Has no role in forming the knee joint ▪ Distal end articulation ▪ Lateral malleolus forms the outer part of the ankle © 2018 Pearson Education, Inc. Figure 5.25c Bones of the right thigh and leg. Intercondylar eminence Lateral Medial condyle condyle Head Tibial tuberosity Proximal tibiofibular joint Interosseous membrane Anterior border Fibula Tibia Distal tibiofibular joint Medial Lateral malleolus malleolus (c) © 2018 Pearson Education, Inc.  Bones of the Lower Limbs ▪ Foot ▪ Tarsals—7 bones ▪ Two largest tarsals are the: ▪ Calcaneus (heel bone) ▪ Talus ▪ Metatarsals—5 bones form the sole of the foot ▪ Phalanges—14 bones form the toes © 2018 Pearson Education, Inc. Figure 5.26 Bones of the right foot, superior view. Phalanges: Distal Middle Proximal Tarsals: Medial Metatarsals cuneiform Tarsals: Intermediate cuneiform Lateral cuneiform Navicular Cuboid Talus Calcaneus © 2018 Pearson Education, Inc.  Joints ▪ Joints are articulations ▪ Occur where two or more bones meet ▪ Functions of joints ▪ Hold bones together securely ▪ Allow for mobility ▪ Two ways joints are classified ▪ Functionally ▪ Structurally © 2018 Pearson Education, Inc.  Joints ▪ Structural joint classifications ▪ Fibrous joints ▪ Generally immovable ▪ Cartilaginous joints ▪ Immovable or slightly movable ▪ Synovial joints ▪ Freely movable © 2018 Pearson Education, Inc.  Joints ▪ Fibrous joints ▪ Bones are united by fibrous tissue ▪ Types ▪ Sutures ▪ Immobile ▪ Syndesmoses ▪ Allow more movement than sutures but still immobile ▪ Found on the distal ends of tibia and fibula ▪ Gomphoses ▪ Immobile ▪ Found where the teeth meet the facial bones © 2018 Pearson Education, Inc. Figure 5.28a Types of joints. Fibrous joints Fibrous connectiv e tissue (a) Suture © 2018 Pearson Education, Inc.  Joints ▪ Cartilaginous joints ▪ Bones are connected by fibrocartilage ▪ Types ▪ Synchrondrosis ▪ Immobile ▪ Found in epiphyseal plates of growing long bones ▪ Symphysis ▪ Slightly movable ▪ Found in the pubic symphysis, intervertebral joints © 2018 Pearson Education, Inc. Figure 5.28c Types of joints. Cartilaginous joints First rib Hyaline cartilage Sternum (c) Synchondrosis © 2018 Pearson Education, Inc. Figure 5.28d Types of joints. Cartilaginous joints Vertebrae Fibrocartilage (d) Symphysis © 2018 Pearson Education, Inc.  Joints ▪ Synovial joints ▪ Articulating bones are separated by a joint cavity ▪ Synovial fluid is found in the joint cavity ▪ Four distinguishing features of synovial joints 1. Articular cartilage 2. Articular capsule 3. Joint cavity 4. Reinforcing ligaments © 2018 Pearson Education, Inc. Figure 5.28f Types of joints. Synovial joints Scapula Articular capsule Articular (hyaline) cartilage Humerus (f) Multiaxial joint (shoulder joint) © 2018 Pearson Education, Inc.  Developmental Aspects of the Skeleton ▪ Fetal skull ▪ Fontanels are fibrous membranes connecting the cranial bones ▪ Known as “soft spots” ▪ Allow skull compression during birth ▪ Allow the brain to grow during later pregnancy and infancy ▪ Usually ossify by 2 years of age © 2018 Pearson Education, Inc. Figure 5.32a The fetal skull. Anterior fontanel Frontal bone Parietal bone Posterior fontanel Occipital (a bone ) © 2018 Pearson Education, Inc.  Developmental Aspects of the Skeleton ▪ Skeletal changes ▪ At birth, the head and trunk are proportionately much longer than the lower limbs ▪ During puberty: ▪ Female pelvis broadens ▪ Entire male skeleton becomes more robust ▪ By the end of adolescence: ▪ Epiphyseal plates become fully ossified © 2018 Pearson Education, Inc.