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1 2 3 6.1 Functions of the Skeletal System Support Protection Attachment sites for skeletal muscles Blood cell production Mineral storage 6.2 Bone Structure There are four basic types of bone based on shape Long bones e.g. thigh bone Short bones e.g. wrist bone Flat bones e.g. skull Irregular bones e.g. spine bone 4 5 Structure of a Long Bone Epiphysis Articular cartilage Diaphysis Epiphyseal plate (line) Periosteum Spongy bone Compact bone Medullary cavity Endosteum 6 Spongy (cancellous) bone Interior of small bones, skull bones, and epiphyses Consists of trabeculae and spaces filled with red bone marrow Reduces bone weight without reducing strength 7 7 Compact bone Wall of diaphysis and surface of diaphysis Tightly packed tissue with no spaces Strong and gives supportive strength 8 9 10 Microscopic Structure Bone cells lie inside lacunae Compact bone Osteons Osteonic canals Lamellae Foramen Canaliculi Spongy (cancellous) bone Lack osteons Receive nutrients by diffusion through canaliculi 11 12 13 6.3 Bone Formation Ossification is the process of bone formation during the 6th or 7th week of embryonic life Two types of bone formation 1. Intramembranous ossification 2. Endochondral ossification 14 15 14 15 For both types of bone formation Primitive connective tissue cells become osteoblasts Osteoblasts deposit bone matrix around them Once trapped in matrix, osteoblasts become osteocytes 16 1. Intramembranous Ossification Forms most skull bones Steps involved Connective tissue membranes form at sites of future intramembranous bones Some cells become osteoblasts and deposit spongy bone within the membrane starting in the center of bone Osteoblasts from the covering membrane (periosteum) deposit a layer of compact bone over the spongy bone 17 18 To produce the correct bone shape Use osteoclasts to remove bone matrix Use osteoblasts to reform new bone matrix 19 2. Endochondral Ossification Forms most bones of the body Example: long bones 20 Steps involved Primary ossification center forms in center of cartilage Periosteal osteoblasts form a collar of compact bone around primary ossification center Cartilage in the primary center calcifies and chondrocytes die 21 Blood vessels and nerves penetrate the center, bring osteoblasts with them Osteoblasts form spongy bone at the primary ossification center Secondary ossification center forms in the epiphyses Osteoblasts form spongy bone at the primary ossification center Secondary ossification center forms in the epiphyses Osteoclasts remove the spongy bone and form the medullary cavity 22 Bone continues to grow At the end of the process, the epiphyseal plate separates the epiphyses from the diaphysis 23 24 Continued growth in diameter due to formation of compact bone beneath the periosteum Continued growth in length takes place at the epiphyseal disk Cartilage grows on the epiphyseal side Cartilage is converted into bone on the diaphysis side Osteoblasts and osteoclasts continually reshape the bone as it grows Bone growth in length continues until age 25 Epiphyseal plate is completely replaced by bone Epiphyseal line is all that remains 25 Homeostasis of Bone Bone is continually remodeled due to activity of osteoclasts and osteoblasts 26 Remodeling can be affected by Physical activity Dietary calcium intake Age 6.4 Divisions of the Skeleton Skeleton is divided into two divisions Axial skeleton Bones along the longitudinal axis of the body Appendicular skeleton Pectoral girdle and upper extremities Appendicular skeleton Pectoral girdle and upper extremities Pelvic girdle and lower extremities 27 28 6.5 Axial Skeleton Skull Divided into two segments Cranium - 8 fused bones Facial bones - 13 fused bones Bones joined by sutures Immovable joints 29 Several bones possess paranasal sinuses 30 Cranium Frontal bone Anterior part of cranium Two frontal sinuses Parietal bones Sides and roof of cranium sagittal suture, coronal suture Occipital bones Posterior portion and floor of cranium foramen magnum: a large opening through which the brain stem extends occipital condyles: articulates with first vertebra (atlas) Fig 6.9 lambdoidal sutures: joined to the parietal bones 31 32 33 34 33 34 35 Cranium Temporal bones Inferior to parietal bones on each side of the cranium Squamosal sutures (parietal), lambdoidal sutures (occipital) external auditory canal: leads inward to eardrum mandibular fosssa anterior to the auditory canal a depression that receives the mandibular condyle temporomandibular joint processes zygomatic process: projects anteriorly to join with zygomatic bone mastoid process: a large, rounded projection inferior to the auditory canal. attachment site for some neck muscles styloid process: medial to the mastoid process, spikelike 36 37 38 Sphenoid bone "Keystone" of the cranium it articulates with all other cranial bones sella turcica a depression that contains the pituitary gland Two sphenoidal sinuses below sella turcica 39 40 Ethmoid bone Anterior portion of cranium, including medial surface of eye orbit and roof of nasal cavity (ethmoid sinus) perpendicular plate: form most of the nasal septum Anterior portion of cranium, including medial surface of eye orbit and roof of nasal cavity (ethmoid sinus) perpendicular plate: form most of the nasal septum superior and middle nasal conchae cribriform plate the roof of the nasal cavity crista galli (cock's comb): to which meninges are attached 41 Facial Bones Maxillae Form upper jaw, anterior portion of hard palate, part of lateral walls of nasal cavity, floors of eye orbits Each maxilla is formed separately, but they are joined at the midline during embryonic development → (cf. cleft lip) palatine process → hard palate alveolar process → teeth alveoli: the sockets containing the teeth Maxillary sinus: below orbits Palatine bones Form posterior portion of hard palate, lateral wall of nasal cavity 42 43 zygomatic (=yoke) Zygomatic bones Cheek bones Also form floor and lateral wall of each eye orbit temporal process (zygomatic bone) + zygomatic process (temporal bone) = zygomatic arch 44 45 Lacrimal bones Medial surfaces of eye orbits Nasal bones Form bridge of nose vomer (=plowshare, 보습) Vomer In midline of nasal cavity Vomer In midline of nasal cavity Forms nasal septum with the ethmoid bone 46 Inferior nasal conchae Attached to lateral walls of nasal cavity Mandible Lower jawbone Only movable skull bone body: U-shaped ramus:Y-shaped coronoid process mandibular condyle → mandibular fossa → temporomandibular joint 47 48 Hyoid bone F. hyoïde < L. hyoides < Gk. ὑοειδής huoeidēs = "shaped like the letter υ" → Y,u (upsilon ← hu) Found in anterior portion of neck, inferior to mandible Does not articulate with any other bones suspended from the styloid processes by ligaments Used as attachment site for tongue muscles 49 50 The infant skull Newborn skull is incompletely developed Possess fontanels Non-ossified areas Allow for flexibility during birth and growth afterwards 6 fontanels Allow for flexibility during birth and growth afterwards 6 fontanels anterior (1), mastoid (2), posterior (1), sphenoid (2) 51 52 Vertebral Column Extends from skull to pelvis Flexible and sturdy longitudinal support for trunk Formed by 24 movable vertebrae, a sacrum, and a coccyx Possess intervertebral discs Shock absorbers Possess four distinct curvatures cervical, thoracic, lumbar, pelvic 53 54 Structure of a Vertebra All vertebrae have common features Body Neural arch Vertebral foramen Spinous process Transverse process Superior and inferior articulating facets Intervertebral foramina 55 Cervical vertebrae C1-C7, Support neck Possess unique transverse foramen a passageway blood vessels and nerves 56 Atlas: cervical vertebra 1 56 Atlas: cervical vertebra 1 Articulate occipital condyles of occipital bone Supports head 57 58 Axis: cervical vertebra 2 Possesses the odontoid process (dens) Serves as a pivot point for axis 59 Thoracic vertebrae T1-T12 spinous processes are longer and slope downward Ribs articulate on the transverse processes and bodies 60 Lumbar vertebrae L1-L5 Heavy, thick bodies to support greater stress and weight Blunt spinous processes - attachment of back muscles 61 62 Sacrum Five fused sacral bones Fused spinal processes → tubercles sacral foramina, sacral canal, sacral hiatus Forms posterior wall of pelvic girdle Coccyx Tailbone Three to five fused rudimentary vertebrae 63 Three to five fused rudimentary vertebrae 63 64 65 Thoracic Cage Composed of Thoracic vertebrae Ribs Costal cartilages Sternum Functions Protection of internal organs Support of upper body 66 67 68 Ribs Attached to thoracic vertebrae True ribs (#1-7) Attached to sternum directly by costal cartilages False ribs (#8-10) Attach to costal cartilage of superior ribs Floating ribs (#11-12) Do not attach anteriorly, no costal cartilages 69 70 Sternum 70 Sternum Flat, elongated bone in the anterior midline of thoracic cage Composed of three fused bones Manubrium Body Xiphoid process 71 72 6.6 Appendicular Skeleton Consists of Pectoral girdle and upper extremity Pelvic girdle and lower extremity Composed of 126 individual bones c.f. 80 axial bones → Total 206 bones 73 Pectoral Girdle Composed of Two clavicles Two scapula Clavicle Articulates with sternum and scapula 74 Scapula Located on each side of vertebral column Does not articulate with the axial skeleton Held in place by muscles to allow free shoulder movement Scapular spine acromion process Scapular spine acromion process glenoid cavity coracoid process 75 Humerus Articulates with scapula at the shoulder and ulna and radius at the elbow Head fits into glenoid cavity of the scapula greater tubercle: lateral intertubercular groove lesser tubercle: medial neck: anatomical vs. surgical (fracture) deltoid tuberosity deltoid muscle condyles trochlea: medial → ulna capitulum: lateral → radius lateral, medial epicondyles fossa coronoid f.: anterior, coronoid process of ulna olecranon f.: posterior, olecranon process of ulna 76 Ulna Medial bone in forearm Bone does not move with hand rotation olecranon process fits into olecranon fossa (of humerus) trochlear notch articulates with trochlea (of humerus) coronoid process fits into coronoid fossa (of humerus) head: distal, articulates with medial surface of radius fits into coronoid fossa (of humerus) head: distal, articulates with medial surface of radius styloid process: ligaments of the wrist Radius Lateral bone in the forearm Bone that rotates when the hand is rotated head: proximal, articulates with capitulum radial tuberosity: biceps muscle styloid process: ligaments of the wrist 77 Carpals Wrist bones Metacarpals Bones of the palm of the hand Phalanges Bones of the fingers 78 Pelvic Girdle Consists of Two coxal bones Sacrum Forms a rigid, bony pelvis 79 Coxal Bones Attachment site for the legs Formed by three fused bones Ilium iliac crest greater sciatic notch iliac crest greater sciatic notch sacroiliac joint Ischium Pubis 80 Coxal Bones Attachment site for the legs Formed by three fused bones Ilium iliac crest greater sciatic notch sacroiliac joint Ischium ischial tuberosity ischial spine: determines the diameter of the pelvic opening during childbirth Pubis 81 82 Coxal Bones Attachment site for the legs Formed by three fused bones Ilium iliac crest greater sciatic notch sacroiliac joint Ischium ischial tuberosity ischial spine Pubis obturator foramen symphysis pubis obturator foramen symphysis pubis Three bones join at acetabulum 83 84 85 The pelvic girdles of males and females have several structural differences 86 87 Lower Extremity Femur Thigh bone Largest and strongest bone in the body head ( → acetabulum) greater (lesser) trochanter lateral (medial) condyle → tibia Patella Kneecap, anterior to the knee joint It is a sesamoid bone, which refers to a bone that is embedded in the tendon 88 Tibia Shinbone Lager, medial bone in lower leg Bears body weight lateral (medial) condyle: femur tibial tuberosity: patellar ligament medial malleolus: medial prominence of the ankle Fibula Slender, lateral bone in lower leg lateral malleolus: lateral prominence of the ankle Slender, lateral bone in lower leg lateral malleolus: lateral prominence of the ankle 89 90 Tarsals ankle bones talus: the prominent tarsal bone calcaneus: heel bone Metatarsals Bones of the instep Phalanges Toe bones 91 92 6.7 Articulations An articulation is a joint or junction between two bones Joints allow for varying degrees of movement Three categories of joints Immovable Slightly movable Freely movable 93 Immovable Joints (synarthrosis) Bones are tightly joined and separated by thin fibrous connective tissue No movement at the joint Example: sutures Slightly Movable Joints (amphiarthrosis) Bones separated by layer of cartilage or fibrous connective tissue Limited flexibility Bones separated by layer of cartilage or fibrous connective tissue Limited flexibility Example: joints between vertebrae 94 Freely Movable Joints (diarthrosis) Joints are freely movable Structurally more complex Several types of freely movable joints joint (articular) capsule : formed of ligament cf. ligament vs. tendon synovial membrane synovial fluid articular cartilage 95 Gliding Joints Involve sliding of bones across each other Example: carpal and tarsal bones 96 Condyloid Joints Allow movement from side to side and back and forth Example: between carpals and bones of forearm 97 Hinge Joints Allow movement in one direction only Example: knee and elbow joints 98 Saddle Joints Ends of each bone are saddle shaped Movement is side to side and back and forth Example: joint between trapezium and metacarpal of thumb Example: joint between trapezium and metacarpal of thumb 99 Pivot Joints Allow rotational movement Example: atlas on the axis 100 Ball-and-Socket Joints A rounded head of one bone fits into a concavity on another bone Movement may be rotational or in any plane Example: hip and shoulder joint 101 Movements at Freely Movable Joints Movement is caused by contraction of muscles that span the joint Movement depends upon joint type and location of muscle(s) involved 102 103 104 105 106 107 108 6.8 Disorders of the Skeletal System Common disorders can be characterized as Disorders of bones Disorders of joints Orthopedics Branch of medicine that specializes in treating skeletal disease and abnormalities Disorders of Bones Fractures: broken bones Complete: The break is completely through the bone. Compound: A broken bone pierces the skin. Complete: The break is completely through the bone. Compound: A broken bone pierces the skin. Simple: A bone does not pierce the skin. Comminuted: The bone is broken into several pieces. Segmental: Only one piece is broken out of the bone. Spiral: The fracture line spirals around the bone. Oblique: The break angles across the bone. Transverse: The break is at right angles to the long axis of the bone. Incomplete: The bone is not broken completely through. Green stick: The break is only on one side of the bone, and the bone is bowed. Fissured: The break is a lengthwise split in the bone. 109 110 Osteomyelitis Inflammation of bone and bone marrow due to bacterial infection Osteoporosis Weakening of bone due to loss of calcium salts Common in older people, especially postmenopausal women Caused by inactivity and decrease in hormone production 111 112 Rickets Childhood disease Due to deficiency of calcium salts in bones Dietary deficiency in calcium or Vitamin D Children have a bowlegged appearance Disorders of Joints Arthritis Characterized by inflammation, swelling, and pain Rheumatoid arthritis Most painful and crippling type Most painful and crippling type Result is ossification of joint, making it immovable Auto-immune disorder Osteoarthritis Most common type Loss of articular cartilage makes movement restricted and painful 113 Bursitis Inflammation of bursa Dislocation Displacement of bones forming the joint Herniated disk Intervertebral disc protrudes out beyond vertebrae Caused by excessive pressure May apply pressure to nerves 114 Spinal curvatures Kyphosis (hunchback) Excessive thoracic curvature Lordosis (swayback) Excessive lumbar curvature Scoliosis Abnormal lateral curvature 115 116 117 Sprain Tearing or stretching of ligaments and tendons without dislocation Kyphosis Lordosis Scoliosis 117 Scoliosis