Skull of the Adult Skeleton Found in the Axial Skeleton vities-by-system/skeletal-system

Skull of the Adult Skeleton

Found in the Axial Skeleton

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General Characteristics

• Usually 22 bones• Sutures interlocking all bone except

the mandible. • Cranium & Facial skeleton

Cranium

• Encloses and protects the brain.• Surface provides attachments for

muscles• Sinuses- Air filled cavities • 8 bones

• Frontal bone (1)-anterior portion of the skull above the eyes(orange).• Parietal bone(2)-located on each side of the skull just behind the frontal bone(blue).• Occipital bone(1)-joins the parietal bones & forms the back of the skull Articulates with 1st vertebrae (purple).• Temporal bone(2)-beneath the parietal bones on each side of the skull. Articulates with the mandible and houses the external/internal ear (red).• Sphenoid bone(1)-Wedged between several other bones in the anterior portion of the cranium(rose).• Ethmoid bone(1)-front of the sphenoid bone(pink).

Facial Skeleton

• 13 immovable bones and a movable lower jaw.

• Forms face shape & facial expressions

• Provides attachments for muscles

• Maxillary bones(2)-upper jaw, keystone of the face(yellow).• Palatine bones(2)-L-shaped located behind the maxillae. Form lateral walls of nasal cavity(light blue).• Zygomatic bones(2)-prominence of cheek and sides of the eyes(green).• Lacrimal bones(2)-thin, scale-like structure located on the medial wall of each orbit(blue).

• Nasal bones(2)-long , thin & nearly rectangular. Lie side by side and are fused to form nose(teal).• Vomer bone(1)-thin, flat at midline within nasal cavity(magenta)• Inferior nasal conchae(2)-fragile, scroll-

shaped bones attached to the lateral wall of the nasal cavity(blue).• Mandible(1)-lower jawbone & horseshoe shaped body(orangish).

Middle Ear Bones & Hyoid Bone

Found in the Axial Skeleton

Middle Ear Bones• 6 bones• Malleus(2)-mallet

shape,vibrations• Incus(2)-middle,

vibrations• Stapes(2)-stirrup-

shaped bone, transmits

vibrations from the incus

Hyoid Bone• 1 bone• Located in the neck between the

lower jaw and the larynx (voice box)• Supports the tongue.

Vertebral ColumnFound in the Axial Skeleton

Characteristics • Extends from the skull to

the pelvis & forms the vertical axis of the skeleton.

• Composed of many bones called vertebrae separated by fibrocartilage called intervertebral discs.

• Supports head and trunk• Protects spinal cord• Infant=33 & Adult=26• 4 curves which

correspond to their region in body: cervical, thoracic, lumbar and pelvic.

Cervical• 7 bones• Small but dense tissue• Atlas- C1, supports the

head• Axis-C2, has a

toothlike process called dens the atlas can pivot around when head moves side to side.

Thoracic • 12 bones• Larger than cervical• Pointed spinous process, slopes

downward and has facets on sides of it body which articulates with the ribs.

• Increase in size inferiorly

Lumbar• 5 bones• Lower back• Support more weight and are

larger/stronger

Pelvic• Consists of the Sacrum and Coccyx• Sacrum- triangular structure at the base

of the vertebral column. Composed of five fused vertebrae.

• Coccyx-tailbone, four fused vertebrae.

Thoracic Cage

Found in the Axial Skeleton

Characteristics

• Includes the ribs, the thoracic vertebrae, the sternum and the costal cartilages that attach the ribs to the sternum

• Support shoulder girdle and upper limbs, protect the viscera in the thoracic & upper abdominal cavities and play a role in breathing.

Ribs• Usually 24 bones, attached to the 12

thoracic vertebrae.• First 7 rib pairs called true ribs-join the

sternum by their costal cartilage (hyaline cartilage)

• Next 5 pairs are called false ribs-cartilage doesn’t reach the sternum directly.– Last 2 ribs called floating ribs-only attached

to vertebrae

• Rib has a long, slender shaft which curves around the chest and slopes downward.

Sternum• Breastbone• Located along the

midline in the anterior portion of the thoracic cage.

• Flat, elongated bone-3 parts (upper manubrium, middle body, lower xiphoid)

Pectoral GirdleFound in the Appendicular

Skeleton

Characteristics

• Shoulder girdle• Four parts: 2 clavicles (collarbones), 2

scapulae (shoulder blades)• Incomplete ring structure• Supports upper limbs & attachment for

several muscles that move the limbs.

Clavicles• Slender, rodlike bones with elongated S-

shapes• Located at the base of the neck, running

horizontally between the sternum and the shoulders.

• Structurally weak• Help holds shoulder in place

Scapulae• Broad, triangular bones located on either

side of the upper back.• Spine divides into unequal portions

Upper Limbs

Found in the Appendicular Skeleton

Characteristics

• Form the framework of the arm, forearm and hand.

• Include the humerus, radius, ulna, metacarpals and phalanges.

Humerus• Long bone that

extends from the scapula to the elbow.

• Numerous tubercles provide attachments for muscles

Radius• Located on the thumb

side of the forearm• Somewhat shorter

than ulna• Extends from the

elbow to the wrist

• Wrench-like opening at proximal end

Ulna

Hand• Wrist, palm and fingers• Each wrist has 8 small carpal bones (2

rows of 4)-carpus.• Each hand has 5 metacarpal bones in

line with each finger (numbered from thumb to pinkie)

• Each hand has 14 phalanges, which are the finger bones. There are 3 in each finger-proximal, middle and distal & 2 in the thumb.

Pelvic Girdle

Found in the Appendicular Skeleton

Characteristics• Consists of two coxae or hipbones

which articulate with each other anteriorly.

• The sacrum, coccyx and pelvic girdle together form the bowl shaped pelvis

• Supports the trunk of the body, provides attachments for lower limbs, protects the urinary bladder, distal ends of the large intestines & the internal reproductive organs.

Characteristics cont.• Each coxa, hipbone develops from three

parts– They fuse together in the region of a cup-

shaped cavity called the acteabulum which is where the femur bone articulates.

• 3 bones:– Illium-largest and most superior portion of the

coxa flares outward forming the prominence of the hip.

– Ishium-forms the lowest portion of the coxa, is L-shaped. Helps support body while sitting.

– Pubis-anterior portion of the coxa. 2 pubic bones come together to form a joint called the symphysis pubis.• Ishium & pubis creates the largest foramen in the

body.

Male vs. Female Pelvis• Female illiac bones are

more flared & hips are broader

• Angle of female pupic arch may be greater, greater distance between ischial spines and ischial tubersosity & the sacral curvatures may be shorter and flatter.

• Bones of female pelvis are usually lighter, more delicate and show less evidence of muscle attachments.

Lower LimbsFound in the Appendicular Skeleton

Characteristics• Framework of the thigh,

leg and foot.• They include the femur,

tibia , fibula, tarsals, metatarsals and phalanges.

Femur • Thigh bone, longest bone

in the body and extends from the hip to the knee.

• Knee cap is a flat sesamoid bone located in a tendon that passes anteriorly over the knee.

• Shin bone, larger of the two leg bones & is located on the medial side.

• Long, slender bone located on the lateral side of the tibia.

Patella

Tibia

Fibula

Foot• Made up of the ankle, the instep and the toes.• Each ankle or tarsus is composed of 7 tarsal

bones.– Talus can move freely, but remaining 6 are firmly

bound together.– Calcaneus or heel is the largest tarsal bone. Helps

support the weight of the body.

• Instep or metatarsus consists of 5 elongated metatarsal bones

• Tarsals and metatarsals are arranged and bound by ligaments to form the arches of the foot

• Phalanges of the toes are shorter but similar to the fingers