Download - The Skeletal System
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THE SKELETAL SYSTEM
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General Considerations of Bones
Average adult skeleton has 206 bones (Figure 7.1)
Bones are paired or unpaired
Most anatomical terms used to describe the features of bones are based on the relationship between the bones and associated ligaments, muscles, joints, nerves, and blood vessels (Table 7.1) Processes
Surfaces
Holes
The skeleton is divided into the axial and appendicular skeletons
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Fig 7.1
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Tab. 7.1
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Axial Skeleton
The axial skeleton forms the upright axis of the body
Consists of
Skull
Auditory ossicles
Hyoid bone
Vertebral column
Thoracic cage (rib cage)
Protects the brain, the spinal cord, and the vital organs housed within the thorax
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Axial Skeleton Skull
Composed of 22 bones The braincase protects the brain Paired parietal and temporal bones, and the unpaired
frontal, occipital, sphenoid, and ethmoid bones
The facial bones protect the sensory organs of the head and serve as muscle attachment sites The 14 facial bones are the maxilla (2), zygomatic (2),
palatine (2), lacrimal (2), nasal (2), inferior nasal concha (2), mandible (1), and vomer (1) bones
The mandible and maxillae hold the teeth, and the auditory ossicles that function in hearing, are located inside the temporal bones
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Axial Skeleton
Skull (External view)
Parietal bones Joined at the midline by the sagittal suture
Joined to the frontal bone by the coronal suture
Joined to the occipital bone by the lambdoid suture
Joined to the temporal bone by the squamous suture
The external occipital protuberance is an attachment site for an elastic ligament
Nuchal lines are the points of attachment for neck muscles
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Fig 7.2
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Fig 7.3
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Axial Skeleton Skull (Lateral view)
The external acoustic meatus transmits sound waves toward the eardrum
Neck muscles attach to the mastoid process, which contains mastoid air cells
The temporal lines are attachment points of the temporalis muscle
The zygomatic arch, from the temporal and zygomatic bones forms a bridge across the side of the skull
The mandible articulates with the temporal bone
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Fig 7.4
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Fig 7.5
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Axial Skeleton
Skull (Anterior view)
The orbits contain the eyes
The nasal cavity is divided by the nasal septum
Sinuses within bone are air-filled cavities The paranasal sinuses, which connect to the
nasal cavity, are the Frontal sinus
Sphenoidal sinus
Maxillary sinuses
Ethmoidal labyrinth
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Fig 7.6
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Fig 7.7
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Fig 7.8
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Fig 7.9
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Fig 7.10
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Axial Skeleton
Skull (Inferior surface)
Spinal cord and brain are connected through the foramen magnum
Occipital condyles are points of articulation between the skull and the vertebral column
Blood reaches the brain through the internal carotid arteries, which pass through the carotid canals, and the vertebral arteries, which pass through the foramen magnum
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Axial Skeleton
Skull (Inferior surface)
Most blood leaves the brain through the internal jugular veins, which exit through the jugular foramina
Styloid processes provide attachment points for three muscles involved in movement of the tongue, hyoid bone, and pharynx
The hard palate separates the oral cavity from the nasal cavity
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Fig 7.11
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Axial Skeleton
Skull (Superior view inside the cranial cavity)
The crista galli is a point of attachment for one of the meninges
The olfactory nerves extend into the roof of the nasal cavity through the olfactory foramina of the cribriform plate
The sella turcica is occupied by the pituitary gland
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Tab. 7.2
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Tab. 7.3
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Fig 7.12
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Axial Skeleton
The hyoid bone, which floats in the neck, is the attachment site for throat and tongue muscles
Fig 7.13
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Axial Skeleton
Vertebral Column
Provides flexible support and protects the spinal cord
The vertebral column has four major curvatures:
Cervical
Thoracic
Lumbar
Sacral/Coccygeal
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Fig 7.14
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Fig 7.15
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Axial Skeleton
Vertebral Column (Vertebra) Consists of a body, a vertebral arch, and various
processes Part of the body and vertebral arch (pedicle and
lamina) form the vertebral foramen, which contains and protects the spinal cord
The transverse and spinous processes are points of muscle and ligament attachment
Vertebrae articulate with one another through the superior and inferior articular processes
Spinal nerves exit through the intervertebral foramina
Adjacent bodies are separated by intervertebral disks
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Fig 7.16
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Tab. 7.4
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Axial Skeleton
Vertebral Column Components All seven cervical vertebrae have transverse
foramina, and most have bifid spinous processes The 12 thoracic vertebrae have attachment sites
for ribs and are characterized by long, downward-pointing spinous processes
The five lumbar vertebrae have thick, heavy bodies and processes. Their superior articular facets face medially and their inferior articular facets face laterally
The sacrum consists of five fused vertebrae and attaches to the coxal bones to form the pelvis
The coccyx consists of four fused vertebrae attached to the sacrum
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Fig 7.17
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Tab.
7.4(Cont
d.)
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Tab. 7.5
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Page
160.a
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Page
160.b
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Axial Skeleton Thoracic Cage The thoracic cage (consisting of the ribs, their
associated costal cartilages, and the sternum) protects the thoracic organs and changes volume during respiration
Twelve pairs of ribs attach to the thoracic vertebrae Seven pairs of true ribs
Five pairs of false ribs Two pairs of false ribs are floating
The sternum is composed of the Manubrium
Body
Xiphoid process
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Fig 7.19
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Fig 7.20
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Appendicular Skeleton
Consists of the bones of the upper and lower limbs and the girdles by which they are attached to the body
Pectoral girdle: upper limbs
Pelvic girdle: lower limbs
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Appendicular Skeleton
Pectoral Girdle/Shoulder Girdle
scapulae and clavicles
Scapula
Flat, triangular
3 fossae: arm muscles
Glenoid fossa: head of humerus
Acromion process: clavicle
Spine: posterior surface of scapula
Coracoid process: arm and chest muscles Attachment site for shoulder, back and arm muscles
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Fig 7.22
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Appendicular Skeleton
Clavicle Proximal end: attached to the
sternum
Holds the shoulder away from the body and allows movement of the scapula, resulting in free movement of the arm
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Fig 7.23
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Appendicular Skeleton
Upper Limb
Arm bone: humerus Head: glenoid cavity of scapula
Anatomical neck
Surgical neck
Tubercles: hold humerus to scapula
Deltoid tuberosity
Epicondyle: forearm muscles; medial and lateral
Capitulum: radius
Trochlea: ulna
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Fig 7.25
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Appendicular Skeleton
Upper Limb
Forearm bone: Ulna (medial) Trochlear notch: proximal end; elbow
joint
Olecranon process: point of the elbow
Coronoid process: grip with humerus
Styloid process: wrist ligaments
Head: posterior ulnar side of wrist
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Appendicular Skeleton
Upper Limb
Forearm bone: Radius (lateral) Head: rotates against humerus & ulna
Radial tuberosity: biceps brachii
Styloid process: wrist ligaments
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Appendicular Skeleton
Upper Limb
Eight carpal, or wrist, bones are arranged in two rows
five metacarpal bones (bony framework)
The phalanges are digital bones. Each finger has three phalanges, and the thumb has two phalanges
Proximal, middle, distal
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Appendicular Skeleton
Pelvic Girdle
2 coxal (hip) bones + sacrum
Pelvis: pelvic girdle + coccyx
Coxal bone
Ilium: most superior
Ischium: inferior and posterior
Pubis: inferior and anterior
Iliac crest: superior margin
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Appendicular Skeleton
Pelvic Girdle
Anterior superior iliac spine: landmark
Pubic symphysis: anterior
Sacroiliac joint: posterior
Acetabulum: socket
Obturator foramen
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Pelvic (Hip) Girdle
Basin-like pelvis is formed by two hip bones (pelvic girdle) + sacrum and coccyx
False (greater) pelvis: broad region superior to pelvic brim; contains abdominal organs
True (lesser) pelvis: small region inferior to pelvic brim; contains urinary bladder + internal reproductive organs
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Appendicular Skeleton
Lower Limb
Femur (thigh): between hip and knee
Head: acetabulum of coxa
Condyles (medial and lateral): tibia
Epicondyles (medial and lateral): ligament attachment
Neck
Trochanters (Greater and lesser)
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Appendicular Skeleton
Lower Limb
Leg (between knee and ankle)
Tibia (shinbone): major weight-bearing bone; medial
Condyles (medial and lateral): articulates with the condyles of the femur
Tibial tuberosity
Medial malleous
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Appendicular Skeleton
Lower Limb
Fibula (lateral)
Longest and thinnest bone
Does not articulate with femur
Head articulates with tibia
Lateral malleolus
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Right Femur
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Right Tibia and Fibula
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Ankle and Foot Tarsus (ankle) has 7 bones Large talus (ankle bone) and
Calcaneus (heel bone)
Metatarsals (foot bones) Numbered 1 to 5 from medial to lateral
Phalanges (toe bones) Big toe has proximal and distal phalanges while
others have proximal, medial and distal phalanges. Numbered like metatarsals from 1-5
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Right Foot