Chapter 7 Notes

Structure of the Skeleton

Structure of the Skeleton

• Skeletal tissue forms bones.• Bones are organized or grouped to

form major subdivisions.• Coordination of bones with joints

and muscles allows for movement.

Subdivisions of the Skeleton

• Axial - 80 bones– Skull - face and cranium– Earbones - 3– Hyoid bone - in neck, not attached to

any other bone - helps in tongue movement

– Spinal column– Sternum and ribs - thoracic cage

Hyoid Bone

Subdivisions of the Skeleton Continued

• Appendicular skeleton - 126 bones

– Upper extremities– Lower extremities– Pectoral girdle - scapula and clavicle

Skull – 28 Bones - Major Subdivisions

• Cranium - brain case– Frontal - forehead and anterior top– Parietal (2) - give shape to top side of

cranium– Temporal - lower sides of cranium

Skull - Major Subdivisions

– Occipital - framework for lower, posterior skull– Sphenoid - helps form the base of the cranium– Ethmoid - irregular bone, posterior to nasal

bones

Skull - Major Subdivisions Continued

• Face– Maxilla– Mandible -

lower jaw, only movable structure of face; strongest of face

– Zygomatic arch -shapes cheeks

– Nasal bones - shapes nose

Skull

• Mastoiditis– Inflammation of the air spaces within

the mastoid portion of the temporal bone.

– Could spread to brain if left untreated.

Skull

Vertebral Column – Spinal Column

• Longitudinal axis of skeleton• Flexible due to segmentation• Backbone of body

– head balanced on top– ribs suspended in front– lower extremities attached below– spinal cord enclosed within

Division of Column

• Cervical vertebrae - 7

– Framework for the neck– 1st = atlas– 2nd = axis – for neck

rotation

• Thoracic vertebrae - 12

– Allows for rib attachment

• Lumbar– Support small of back

• Sacrum and Coccyx– Fusion of vertebrae

Structure of a Single Vertebrae

• Body - flat, round surface

• Spinous process - backwards projections

• Transverse process - lateral projections (winglike)

• Vertebral foramen - hole for spinal cord

• Curved - allows for strength and balance

Pathological Curvatures of the Spine

• Lordosis– curve in lumbar region is exaggerated

in concavity

Pathological Curvatures of the Spine

• Scoliosis– any region is abnormally curved

laterally

Pathological Curvatures of the Spine

• Kyphosis– hunchback– convexity in thoracic region

Shoulder Girdle

• Clavicle• Scapula• Forms one joint

with trunk between 2 bones.

• All shoulder movement involves this joint.

Pelvic Girdle

• Stable, circular base, supports trunk and attaches lower extremities.

• Three Parts– Ilium - largest and

uppermost bone– Ischium - strongest

and lowermost bone– Pubis - anteriormost

bone– Strong ligaments

attach sacrum to each hip bone.

Sternum

• Medial part of anterior chest wall.

• Xiphoid process– cartilaginous lower tip

• Ribs– True Ribs – attached

to sternum– False Ribs – their

cartilages do not reach sternum directly

– Floating – no attachment to sternum

Upper Limb

• Humerus– Long bone that

extends from the scapula to the elbow (when hit at distal end it is known as the funny bone).

– Upper end has smooth rounded head that fits into cavity of scapula.

– 2 processes just below the head, greater and lesser tubercles .

• Provide attachment for muscles.

Upper Limb Continued

• Radius– Located on the thumb

side of the forearm.– Extends from the

elbow to the wrist and crosses over ulna.

• Ulna– Longer than the

radius. – Overlaps the end of

the humerus posteriorly.

Wrist and Hand

• Wrist - consists of 8 small bones - carpals

– 2 rows of 4 bones each

• Hand - palm and 5 fingers

– Palm - metacarpals – 5 - line up with each finger

• Numbered 1 to 5 beginning with metacarpal of thumb.

– Fingers – phalanges - 14 in each hand

• 3 in each finger• A proximal, a middle,

and a distal phalanx• 2 in the thumb – missing

middle phalanx

Lower Limb

• Femur– Thigh bone– Longest bone in the

body - extends from the hip to the knee.

• Patella– Kneecap– Located in a tendon

that passes anteriorly over the knee.

Lower Limb Continued

• Tibia– Largest and

strongest bone of the lower leg.

– Located medially and superficially.

– Atriculates with the fibula and talus to form ankle joint.

• Fibula– Smaller lower leg

bone.– Located laterally and

deep.

Foot

• Structure– Arches allow for

great support.– Big toe much more

stable than thumb.

• Tarsals (7)– Create ankle bones– Strong ligaments

and leg muscle tendon keeps arches of foot.

Foot Continued

• Metatarsals (5)– Framework for soles of

feet.– Articulate with

phalanges.– Numbered 1 to 5

beginning on medial side.

• Phalanges– Shorter than that of the

fingers.– Align and articulate with

metatarsals.– Each toe has 3 phalanges

(same as hand).– Big toe has 2.

Skeletal Differences

• Males– Larger and heavier– Pelvis is deep and funnel shaped– Pubic arch is narrow

• Females– Pelvis is shallow, broad and flaring– Pelvic arch is wider

Age Changes in Skeleton

• Incremental decrease in height that begins about age 30.

– 1/16 of an inch a year

• Calcium levels fall – Bones become brittle and increasingly

prone to fracture.– Osteoclasts outnumber Osteoblasts.