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Ch 7 – The Skeleton Part A: The Axial Skeleton Section 1 – Axial Skeleton Overview (pp. 198-200) The Axial Skeleton • Consists of 80 bones • Divided into 3 main parts: 1) Skull 2) Vertebral column 3) Bony Thorax • Functions of Axial Skeleton: 1) Forms longitudinal axis 2) Supports head, neck, & trunk 3) Protects brain, spinal cord, heart, & lungs Ch 7 – The Skeleton Part A: The Axial Skeleton Section 2 – The Skull (pp. 200-216) The Axial Skeleton – Skull Skull - Two sets of bones 1) Cranial bones (Cranium) - enclose & protect brain - provide attachment sites for head/neck muscles 2) Facial bones - provide framework for the face - contain cavities for sight, taste, & smell sense organs - provide attachments sites for facial expression muscles The Axial Skeleton – Skull Skull - Most are flat bones & are joined together by sutures - Mandible only bone attached w/ freely movable joint - Many bones have air-filled sinuses to reduce weight - About 85 openings providing passageways for major blood vessels & nerves Cranial Bones There are 8 cranial bones: Frontal bone Parietal bone (left & right) Occipital bone Temporal bone (left & right) Sphenoid bone Ethmoid bone Cranial Bones – Frontal bone Frontal Bone • Most anterior portion of cranium… forehead • Contains frontal sinus • Forms superior wall of orbits • Supports frontal lobes of brain Cranial Bones – Parietal bones Parietal Bone (x2) • Most superior (top) & lateral (side) parts of cranial cavity • Bulk of cranial cavity Cranial Bones – Occipital bone Occipital Bone • Forms posterior wall of cranium • Attachment site for many neck/back muscles • Occipital condyles - form joint w/ vertebral column • Foramen magnum - large opening for spinal cord to attach to brain Cranial Bones – Temporal bone Temporal Bone (x2) • Inferior to parietal bones • Forms lower sides of cranium & part of cranial floor • External acoustic meatus - surrounds external ear canal • Mandibular fossa - forms the temporomandibular joint w/ mandible • Zygomatic process - part of cheek bone nearest your ear Cranial Bones – Major Sutures Four sutures form major joints of the cranium: 1) Coronal suture - between parietal & frontal bones 2) Squamous suture - between parietal & temporal bones 3) Lamboid suture - between parietal & occipital bones 4) Sagittal suture - between left & right parietal bones Cranial Bones – Sphenoid bone Sphenoid Bone • Complex, bat-shaped bone • “Keystone” of the cranium - forms joints w/ all other cranial bones • Sella turcica - small enclosure for pituitary gland Cranial Bones – Ethmoid bone Ethmoid Bone • Deepest skull bone • Superior part of nasal septum • Cribiform plates - roof of nasal cavities • Crista galli - between cribiform plates attaches to covering of brain to help secure it to cranial cavity Cranial Bones Frontal Bone Left & Right Parietal Bones Occipital Bone Left & Right Temporal Bones Sphenoid Bone Ethmoid Bone Facial Bones There are 14 facial bones: Mandible Maxillary bones (x2) Zygomatic bones (x2) Nasal bones (x2) Lacrimal bones (x2) Palatine bones (x2) Vomer Inferior nasal conchae (x2) Facial Bones – Mandible Mandible • Lower jaw • Largest, strongest facial bone • Temporomandibular joint - only freely movable joint in skull • Alveolar margin - contains sockets for teeth Facial Bones – Maxillary Bones Maxillary Bones • Two bones fused medially • Form upper jaw & central portion of face • “Keystone” of face - form joints w/ all other facial bones Facial Bones – Zygomatic Bones Zygomatic Bones • Cheekbones • Form lateral borders of orbits Facial Bones – Nasal Bones Nasal Bones • Form bridge of nose Facial Bones – Lacrimal Bones Lacrimal Bones • Form medial walls of orbits • Houses lacrimal sac - part of passageway that allows tears to drain into nasal cavity Facial Bones – Palatine Bones Palatine Bones • Form back 1/3 of roof of mouth… hard palate • Form back walls of nasal cavity Facial Bones – Vomer Vomer • Plow-shaped • Lower part of nasal septum Facial Bones – Inferior nasal conchae Inferior nasal conchae • Form lateral walls of nasal cavity • Force inhaled air to swirl so that it can pick up moisture before traveling to lungs Hyoid Bone • Not a bone of the skull • Only bone that does not articulate w/ another bone • Attachment site for muscles of swallowing & speech • Acts as a moveable base for tongue Paranasal Sinuses • Found in frontal, sphenoid, ethmoid, & maxillary bones • Mucosa-lined, air-filled spaces • Enhance resonance of voice • Lighten the skull Ch 7 – The Skeleton Part A: The Axial Skeleton Section 3 – The Vertebral Column (pp. 216-223) The Axial Skeleton – Vertebral column Vertebral column - Transmits weight of trunk to lower limbs - Surrounds & protects spinal cord - Provides attachment points for ribs & muscles of back/neck - Flexible due to its curved construction The Axial Skeleton – Vertebral column Vertebral column - Composed of 26 irregular bones & divided into 5 segments 1) Cervical vertebrae (7) - vertebrae of the neck 2) Thoracic vertebrae (12) - vertebrae of thoracic cage 3) Lumbar vertebrae (5) - vertebrae of lower back 4) Sacrum 5) Coccyx The Axial Skeleton – Vertebral column Natural Curvatures - Increase flexibility of spine - Function like spring instead of rod - When viewed from side, S-shaped - Two posteriorly concave curvatures 1) Cervical curvature 2) Lumbar curvature - Two posteriorly convex curvatures 1) Thoracic curvature 2) Pelvic curvature The Axial Skeleton – Vertebral column The Axial Skeleton – Vertebral column Scoliosis (abnormal lateral curvature) The Axial Skeleton – Vertebral column Kyphosis (“Hunchback”) The Axial Skeleton – Vertebral column Lordosis (“Swayback”) The Axial Skeleton – Vertebral column Ligaments - Give added strength, support to spine 1) Anterior & posterior longitudinal ligaments - run entire length of spine *Anterior = front side; prevents bending too far backward *Posterior = back side; prevents bending too far forward 2) Ligamentum flavum - Connects 2 adjacent vertebrae 3) Short ligaments - Connects each vertebrae to the one above & below it The Axial Skeleton – Vertebral column Intervertebral Discs - cushion-like pads between vertebrae - shock absorbers during walking, jumping, & running - thickest in lumbar/cervical regions; enhances flexibility - flatten during course of day; always a few millimeters shorter at night The Axial Skeleton – Vertebral column Herniated Disc - “slipped disc” - rupture of the disc caused by compression of vertebrae - disc “squeezes” out from between vertebrae - if pressing on spinal cord, causes numbness or pain - usually treated w/ exercise, massage, heat, painkillers - may have to be surgically removed; vertebrae fused The Axial Skeleton – Vertebral column General Structure of Vertebrae 1) Body or centrum - anterior; weight-bearing region 2) Vertebral foramen Animation: Rotatable Spine (horizontal) - opening for spinal cord 3) Intervertebral foramina - openings between vertebrae for spinal nerves to leave spinal cord Animation: Rotatable Spine (vertical) 4) Spinous process - project out the posterior side; protection The Axial Skeleton – Vertebral column Cervical Vertebrae (C1-C7) - smallest, lightest vertebrae - found in the neck C1 vertebra = Atlas - articulates with base of the skull - allows you to nod “yes” C2 vertebra = Axis - knoblike “dens” projects up - Atlas pivots around “dens” - allows you to shake head “no” The Axial Skeleton – Vertebral column Thoracic Vertebrae (T1-T12) - All form joints with ribs - All have long, downwardpointing spinous processes The Axial Skeleton – Vertebral column Lumbar Vertebrae (L1-L5) - “small of the back” - receives most stress - each has large centrum to handle extra stress The Axial Skeleton – Vertebral column Sacrum - shapes posterior wall of pelvis - lateral borders form joints with hips Coccyx - tailbone - nearly useless Ch 7 – The Skeleton Part A: The Axial Skeleton Section 4 – The Thoracic Cage (pp. 223-225) The Axial Skeleton – Thoracic cage Thoracic cage - aka “Bony thorax” - Made up of 3 parts: 1) Sternum 2) Ribs & costal cartilage 3) Thoracic vertebrae The Axial Skeleton – Thoracic cage Thoracic cage - Forms cage to protect major organs of chest - Supports pectoral girdle & upper limbs - Provides multiple muscle attachment sites The Axial Skeleton – Sternum Sternum - “breastbone” - Composed of 3 fused bones: 1) Manubrium - articulates w/ clavicles & ribs 1-2 2) Body - articulates w/ ribs 2-7 3) Xiphoid process - site of muscle attachment - cartilage until age 40 The Axial Skeleton – Ribs Ribs - 12 pairs - True ribs * Top 7 ribs * Attach directly to sternum via costal cartilage - False ribs * Ribs 8-10 * Attach indirectly to sternum - Floating ribs * Ribs 11-12 * No attachment to sternum Ch 7 – The Skeleton Part B: The Appendicular Skeleton Section 5 – Appendicular Skeleton Overview (p. 225) The Appendicular Skeleton • Everything attached to the axial skeleton - Limbs (arms/legs) - Pectoral girdle - Pelvic girdle • Enables us to carry out all body movements Ch 7 – The Skeleton Part B: The Appendicular Skeleton Section 6 – The Pectoral Girdle (pp. 225-228) The Appendicular Skeleton Pectoral (shoulder) girdle - Composed of two bones 1) Clavicle 2) Scapula - Attaches arms to axial skeleton - Provides arm w/ exceptionally free movement A&P Flix™: Bones of the pectoral girdle Pectoral Girdle – Clavicle Clavicle - known as the “collarbone” - acts as a brace; holds scapula & arm out laterally - transmits compression forces of upper limb to axial skeleton - usually fracture anteriorly; posterior fractures very dangerous b/c of major blood vessels just behind clavicle Pectoral Girdle – Scapula Scapula - known as the “shoulder blade” - attaches to spine by way of muscles; exceptional movement Glenoid cavity - articulates with humerus of arm, forming shoulder joint Acromion process - articulates with clavicle Ch 7 – The Skeleton Part B: The Appendicular Skeleton Section 7 – The Upper Limb (pp. 228-233) The Upper Limb Upper Limb - 30 bones in each upper limb 3 main components 1) Arm - Humerus 2) Forearm - Radius & ulna 3) Hand - 8 carpal (wrist) bones - 5 metacarpal (palm) bones - 14 phalanges (finger bones) The Upper Limb – Arm Humerus - only bone of the arm - largest bone of upper limb - proximal end articulates w/ glenoid cavity of scapula Greater & lesser tubercles - attachment sites for rotator cuff Trochlea - articulates w/ ulna Capitulum - articulates w/ radius The Upper Limb – Forearm Ulna - medial bone in forearm - main function is forming elbow joint w/ humerus Radius - lateral bone in forearm - main function is forming wrist joint w/ carpal bones *Interosseous membrane - flat, flexible ligament running entire length between both bones The Upper Limb – Hand Carpals - form “wrist” - 8 total bones laid out in 2 rows Proximal row (from lateral to medial) - scaphoid, lunate, triquetrum, & pisiform Distal row (from lateral to medial) - trapezium, trapezoid, capitate, & hamate *Only the scaphoid & lunate articulate w/ the radius to form the wrist joint The Upper Limb – Hand Metacarpals - form “palm” - 5 total bones - #1-5 starting w/ thumb Phalanges - finger #1 (thumb) = 2 phalanges (distal & proximal) - fingers #2-5 = 3 phalanges (distal, middle, & proximal) Ch 7 – The Skeleton Part B: The Appendicular Skeleton Section 8 – The Pelvic Girdle (pp. 233-237) The Appendicular Skeleton – Pelvis Pelvic girdle - Attaches lower limbs to axial skeleton using some of the strongest ligaments in the body - Lacks mobility of pectoral girdle but far more stable - Supports total weight of upper body - Protects pelvic organs: 1) Reproductive organs 2) Urinary bladder 3) Part of large intestine The Appendicular Skeleton – Pelvis Pelvic girdle - formed by a pair of hip bones - each hip bone is made of 3 fused bones: 1) Ilium 2) Ischium 3) Pubis “Bony pelvis” - the 2 hip bones plus the sacrum & coccyx Acetabulum = deep socket that receives the head of the femur Animation: Rotatable pelvis The Appendicular Skeleton – Pelvis Gender differences in pelvic girdle: The Appendicular Skeleton – Pelvis Gender differences in pelvic girdle: The Appendicular Skeleton – Pelvis Gender differences in pelvic girdle: Ch 7 – The Skeleton Part B: The Appendicular Skeleton Section 9 – The Lower Limb (pp. 237-241) The Lower Limb The Lower Limb - bones thicker & stronger than upper limb bones - carries weight of the body - subjected to exceptional forces 3 main components 1) Thigh - Femur 2) Leg - Tibia & fibula 3) Foot - 7 tarsal (ankle) bones - 5 metatarsal (foot) bones - 14 phalanges (toe bones) The Lower Limb – Thigh Femur - forms the “thigh” - largest, strongest bone in body - “neck” is weakest part & often fractured; “broken hip” Patella - “kneecap” - purpose is to protect knee joint The Lower Limb – Leg Tibia - medial leg bone - receives weight from femur; transmits it to foot Fibula - not weight-bearing - muscle attachment site - does not contribute to knee joint; only stabilizes ankle *Bound together by interosseous membrane The Lower Limb – Foot Tarsals - form “ankle” & posterior ½ of foot - 7 total bones 1) talus 2) calcaneus 3) cuboid 4) navicular 5) medial cuneiform 6) intermediate cuneiform 7) lateral cuneiform *Talus transfers weight from tibia to calcaneus (heel) The Lower Limb – Foot Metatarsals - form anterior ½ of foot - 5 total bones - #1-5 starting w/ big toe Phalanges - toe #1 (big toe) = 2 phalanges (distal & proximal) - toes #2-5 = 3 phalanges (distal, middle, & proximal) Animation: Rotatable bones of the foot Arches of the Foot Foot Arches - maintained by interlocking foot bones, ligaments, & tendons - allow foot to bear weight - “give” or stretch when weight is applied; spring back when weight is removed Ch 7 – The Skeleton Section 10 – Developmental Aspects (pp. 242-244) Developmental Aspects Fetal Skull - very large compared to infant’s total body length - more bones than adult skull; unfused sutures - mandible is proportionally very small Developmental Aspects Fontanelles - fibrous membranes connecting cranial bones in infants - provide brain room to grow - convert to bone within 24 months after birth Developmental Aspects Developmental Aspects Developmental Aspects Growth Rates: - at birth, cranium is huge relative to face - at 9 months, cranium is ½ adult size - mandible & maxilla lengthen w/ age - arms & legs grow at faster rate than head & trunk Developmental Aspects Spinal Curvature: - thoracic & sacral curvatures obvious at birth - this gives the spine a C shape Developmental Aspects Spinal Curvature: - cervical & lumbar curvatures appear as child develops (lifts head, learns to walk, He’s cute! I etc.) think Hey Mike! Come see Typical guy… I’m in love!!! what the dog - positions weight over centerleft!!! of gravity The Boy… Men are from Mars, Women are from Venus… The Girl… Developmental Aspects As you Age… - intervertebral discs become thin & less elastic - risk of disc herniation increases - loss of height (by several cm) is common by age 55 - costal cartilages ossify; thorax becomes rigid (breathing becomes more difficult) - all bones lose mass Ch 7 – The Skeleton Section 11 – Homeostatic Imbalances (pp. 244-245) Homeostatic Imbalances Cleft Palate: - right & left halves of hard palate (maxilla) fail to fuse - opening between oral & nasal cavities - very difficult for babies to drink from bottles - can lead to aspiration (inhalation) of food into lungs Homeostatic Imbalances Clubfoot: - congenital defect where soles of feet face medially & toes point inferiorly - affects 1 in 700 babies - may be genetic defect or the result of abnormal position of the foot in the womb during development Homeostatic Imbalances Spina bifida: - congenital defect of the vertebral column - 1 or more of the vertebral arches incomplete - ranges in severity…may not cause any problem or may severely impair neural function depending on location Homeostatic Imbalances Spinal fusion: - surgical procedure involving insertion of bone chips to immobilize/stabilize specific region of vertebral column - used often with fractures involving the vertebrae & injuries involving herniated discs