Chapter 8: The Skeletal System

Merged flashcards from Chapter 8, McGraw Hill Anatomy and Physiology Ninth Edition, by Kenneth S. Saladin.

Axial skeleton

The central supporting axis of the body; includes the skull, vertebrae, sternum, ribs, sacrum and hyoid

Appendicular skeleton

The appendages of the body; includes the pectoral girdle, upper extremities (arms), pelvic girdle, and lower extremities (legs)

Number of bones

270 at birth, but reduces to 206 by adulthood and may vary depending on new growths

Articulated skeleton

Held together by wire and rods, shows spatial relationships between bones

Disarticulated bones

A skeleton taken apart to study surface features and markings

Sutures

Immovable joints that hold the 22 skull bones

Cavities of skull

• Cranial cavity (brain case)

• Orbits (eye sockets)

• Nasal cavity

• Oral (buccal) cavity

• Middle and inner ear cavities

• Paranasal sinuses

Foramina

Holes that allow passage for nerves and blood vessels

Paranasal sinuses

Air-filled holes lined by a mucous membrane; adds voice resonance and lightens skull

Cranium (braincase)

Consists of the calvaria (skullcap) and cranial case and has membranes separating brain from bones

Frontal bone

Forms the forehead and roof of the cranium

Parietal bones

Forms most of the cranial roof and part of its lateral walls

Temporal bones

Forms the lateral walls and floor of the cranial cavity

Occipital bone

Forms the rear and base of the skull

Sphenoid bone

Located at the anterior base of the skull, made of the body and greater and lesser wings

Ethmoid bone

Located between the eyes; contributes to the medial wall of the orbit, walls of nasal cavity, and nasal septum

Facial bones

Gives shape to and supports the face

Maxillae

The largest facial bones; forms the upper jaw

Palatine bones

L-shaped bones dividing the oral and nasal cavities

Zygomatic bones

Forms part of the angles of the cheekbones and lateral orbital wall

Lacrimal bones

Forms part of the medial wall of each orbit; smallest bones of the skull

Nasal bones

Forms the bridge of the nose and supports cartilages that give shape; often fractured

Mandible

The strongest bone of the skull and the only one to noticeably move; supports the lower teeth

Auditory ossicles

Three in each middle-ear cavity for hearing

Hyoid bone

Slender U-shaped bone between the chin and larynx, not articulated and has horns

Fontanelles

Spaces between the unfused cranial bones childhood for growth

Spine functions

Supporting and protecting the skull, trunk, and spinal cord by absorbing stresses

Vertebral regions

• 7 cervical vertebrae

• 12 thoracic vertebrae

• 5 lumbar vertebrae

• 5 sacral vertebrae

• 4 vertebrae in the coccyx

Primary curvature

The first C-shaped convex curve at birth; persists as the thoracic and pelvic spine

Secondary curvatures

Develop with crawling and walking in childhood; creates the cervical and lumbar areas concave curves

Final curvatures

Spine turns into an S shape: cervical lordosis, thoracic kyphosis, lumbar lordosis, and pelvic kyphosis

Lordoses curve in, kypohses curve out

Abnormal curvatures

Can result from disease, paralysis, posture, or congenital defects like scoliosis (sideways)

Hyperkyphosis

An exaggerated thoracic curvature usually from osteoporosis, the spine curve goes overly out

Hyperlordosis

An exaggerated lumbar curvature usually caused by pregnancy or obesity, the spine curve goes overly in

Spinous process

Projection upward from one vertebra to meet another articular process above

Transverse process

Lateral extension from a vertebtra

Intevertebral foramen

Opening between pedicles of two adjoining vertebrae

Intervertebral discs

Pads between the vertebrae that bind them together to support the weight of the body

Herniated disc

The slipping or rupturing of a disc; can put painful pressure on the spinal nerve or cord

Cervical vertebrae

Notated as C1 to C7; C2 to 6 have forked spinous process while C1 and C2 are the atlas and axis

Atlas

The first cervical vertebrae (C1), supports the head and allows nodding “yes” (pitch) with anterior and posterior arches

Axis

The second cervical vertebrae (C2), allows nodding “no” (yaw)

Thoracic vertebrae

Notated as T1 to T12; has downward angled spinous processes that correspond to the 12 pairs of ribs they are attached to

Lumbar vertebrae

Notated as L1 to L5; have thick, stout bodies and blunt, squarish spinous processes

Sacrum

Bony plate forming the posterior wall of the pelvic girdle, notated as S1 to S5 that begin fusing around age 16

Anterior surface is smooth and concave while posterior surface is very rough

Coccyx

Consists of four smaller vertebrae notated as Co1 to Co4, fuses into single, triangular bone by age 20 to 30

Can be fractured during childbirth or hard fall and provides pelvic muscular attachment

Thoracic cage

Consists of the thoracic vertebrae, sternum, and ribs to enclose the lungs and heart

Sternum

The bony plate anterior to the heart, divided into the manubrium (superior portion), body (long mdidle portion), and xiphoid (inferior point)

Ribs

12 pairs with ends attached to vertebral column and sternum; costal cartilages attach ribs to sternum

True ribs

Ribs 1 to 7, each directly connected to the sternum

False ribs

Ribs 8 to 12, lacking independent connections to the sternum

Floating ribs

Ribs 11 and 12 (also false), no connection at all to sternum or cartilages

Pectoral girdle

Supports the arm, consists of the clavicle (collarbone) and scapula (shoulder blade)

Clavicle

An S-shaped, somewhat flattened bone that is frequently fractured

Scapula

A shovel-like, triangular plate posteriorly overlying ribs 2 through 7

Upper limb

Contains 30 bones in three regions: the brachium (humerus), antebrachium (radius and ulna), and hand (5 metacarpals, 14 phalanges)

Humerus

The arm proper, articulates with the scapula, clavicle, ulna, and radius

Radius

Bone that is part of the antebrachium; has a disc-shaped head for rotation

Ulna

Bone that is part of the antebrachium; has a hook to the humerus

Carpals

Eight bones that form the wrist to allow for flexion, extension, abduction, and adduction in two rows

Metacarpals

Bones of the palm

Phalanges

Bones of the fingers

Pelvic girdle

A ring composed of three bones: two hip (coxal) bones and one sacrum (also part of the vertebral column)

Pelvis

The pelvic girdle, ligaments, and muscles that line the pelvic cavity and its floor

Sacroiliac joint

Joins the coxal bone to the vertebral column

Pubic symphysis

The interpubic disc of fibrocartilage joining the pubic bones anteriorly

Iliac crest

The superior crest of the hip

Acetabulum

The socket of the hip

Ilium

The largest bone in the hip, extends from the iliac crest to the acetabulum

Ischium

The inferioposterior portion of the hip; heavy body with a prominent spine

Pubis

The pubic bone, most anterior portion of the hip bone

Lower limb

Divided into three regions with 30 bones: the thigh (femoral region), leg proper (crural region), and foot (tarsals, metatarsals, and toes)

Femur

The longest and strongest bone of the body; the head articulates with the acetabulum of the pelvis

Patella

The triangular sesamoid bone embedded in the tendon of the knee; cartilaginous at birth and ossifies from ages 3 to 6

Tibia

The thick, medial, weight-bearing leg bone in the leg proper (crural region)

Fibula

The slender, lateral strut that helps stabilize the ankle but does not bear any body weight

Calcaneus

The largest tarsal bone forming the heel

Talus

The most superior tarsal bone sitting upon the calcareous and forms a joint with the tibia and fibula

Metatarsals

Similar to the metacarpals in the hand

Phalanges

Similar to the digits in the hand

Embryonic limb rotation

The rotation of the upper and lower limbs in opposite direction in week 7 of embryonic development; explains posterior and anterior flexion differences

Bipedal adaptation

Bipedalism is advantageous — strong and springy foot arches to counter stress, posture requires less effort, and muscles are supported well