Axial and Appendicular Skeleton

206

Adult skeleton consists of ___ named bones (most of which are paired)

Axial skeleton and appendicular skeleton

Bones of the skeleton can be grouped into 2 divisions

Axial skeleton

80 bones; Includes skull, auditory ossicles, vertebral column, hyoid, ribs, sternum, and thorax

Apendicular skeleton

126 bones; Includes upper and lower limbs and girdles (pectoral and pelvic)

Long, short, flat, irregular, and sesamoid

Most bones can be classified into 5 types based on their shapes

Long bones

Bones that are longer than they are wide, thick compact bone exterior
Ex/ Femur, humerus

Short bones

Bones that are almost equal in width and length, thick spongy bone interior, thin compact bone exterior layer
Ex/ Carpals, tarsals

Flat bones

Bones that may be curved, thin spongy bone interior covered by a thin veneer of compact bone
Ex/ Cranial bones, sternum

Irregular bones

Bones that do not easily fit into any of the other categories, the amount of compact and spongy bone varies
Ex/ Facial bones, vertebrae

Sesamoid bones

Small bones that develop within certain tendons for protection against wear and tear, some can be found within the palms and soles
Ex/ Patella

Surface markings

Characteristic structural features adapted for specific function that bones possess

Depressions and openings & processes

2 major types of surface markings

Depressions and openings

Surface markings that allow for the passage of soft tissues, blood vessels, and nerves; Form joints

Processes

Surface markings that are projections or outgrowths that form joints and serve as attachment points for ligaments and tendons

Fissure

Narrow slit between bones for passage of blood vessels or nerves

Foramen

Opening for passage of blood vessels, nerves, or ligaments

Fossa

Shallow depression

Meatus

A tube-like opening

Condyle

Rounded projection with a smooth articular surface

Facet

Smooth, flat, slightly concave articular surface

Head

Usually rounded articular process supported on a neck

Crest

Prominent ridge or elongated process

Epicondyle

Usually roughened projection on a condyle

Line

Long, narrow ridge or border (less prominent than a crest)

Spinous process

Sharp, slender projection

Trochanter

Very large projection

Tubercle

Variably sized rounded projection

Tuberosity

Variably sized rough projection with rough bumpy surface

Head

The skull contains 22 bones (not including the bones of the inner ear) and makes up the bony framework of the

Nasal cavity, orbits, paranasal sinuses

Besides the cranial cavity, the skull also contains several smaller cavities including

Cranial cavity bones and facial bones

Bones of the skull are grouped into 2 parts

Frontal bone, parietal bone, temporal bone, occipital bone, sphenoid bone, ethmoid bone

8 cranial bones

Parietal bone and temporal bone

Of the cranial bones, there are 2 each of the

Mandible, maxilla, zygomatic bone, nasal bones, lacrimal bones, palatine bones, inferior nasal conchae, vomer

14 facial bones

Maxilla, zygomatic bone, nasal bones, lacrimal bones, palatine bones, and inferior nasal conchae

Of the facial bones, there are 2 each of the

Suture

A “seam”, an immovable joint between bones of the skull

Fontanels

Soft, membrane-filled spaces between the cranial bones in babies; Will become suture joints in adults

Paranasal sinus

A cavity within certain cranial and facial bones (maxillary, ethmoid, sphenoid, and frontal); Lined with mucus membranes (serve to humidify and warm air), reduces the weight of the skull, and helps to resonate the sound of our voice

Hyoid bone

A U-shaped bone situated at the top of the larynx that supports the tongue and provides attachment for some of the muscles in the neck and pharynx

Hyoid bone

Only bone in the body that does not articulate with any other bones

Vertebral column

Other names for this include: spinal column, backbone, and spine

Vertebral column

Encloses and protects the spinal cord, supports the head, serves as a point of attachment for the ribs and pelvic girdle, and provides attachment for muscles of the back and upper limbs

Vertebral column

Composed of 26 vertebrae divided into 5 regions, each of which have unique characteristics to help identify which type they are

Spinal curvatures

4 slight bends in the normal adult vertebral column seen when viewed from the side that function to increase the strength of the vertebral column, help maintain balance and upright position, absorb shocks during walking, and help protect the vertebrae from fracture

Thoracic and sacral

Primary curves that are concave

Cervical and lumbar

Secondary curves that are convex

Abnormal spinal curvatures

Various conditions may exaggerate the normal spinal curves, sometimes causing severe disability
Ex/ Scoliosis, kyphosis, lordosis

Intervertebral discs

Found between the bodies of adjacent vertebrae and functions to absorb vertical shock and form joints which are strong yet still permit movement of the spine

Annulus fibrosus

Tough, outer ring of fibrocartilage of each intervertebral disc

Nucleus pulposis

Soft, pulpy nucleus that is surrounded by the annulus fibrosus in each intervertebral disc

Decompression and rehydration

During the course of a day the intervertebral discs compress and lose water from their cartilage, therefore we are a bit shorter at night and during sleep 2 things occur

Herniated intervertebral disc

Clinical issue of intervertebral discs that can be caused by trauma or can be associated with aging

Body, transverse processes, spinous process, pedicle, and lamina

Typical vertebrae consists of

Pedicle

Connects body to the transverse process

Lamina

Connects transverse process to spinous process

Intervertebral foramina

Formed by notches on the superior and inferior aspects that come together to allow spinal nerves to pass through

Cervical vertebrae

7 bones that comprise the neck and support the head; Smallest of the vertebrae

Transverse foramina

The cervical vertebrae have distinct _____

Atlas

CV1 is the first of the cervical vertebrae and supports the head

Axis

CV2 is the second of the cervical vertebrae and provides a pivot for the atlas

Bifid

The cervical vertebrae has a _____ spinous process (CV2-CV5)

Thoracic vertebrae

12 larger vertebrae in the upper back; Spinous process is long and points down and back; Articulates with the ribs

Lumbar vertebrae

5 vertebrae in the lower back; Largest of the typical vertebrae and supports the weight of the body; Spinous process is short and protrudes horizontally and its vertebral body is kidney shaped

Sacrum

A triangular shaped structure at the base of the vertebral column that is composed of 5 vertebrae that are fused together into one bone and attaches to the bones of the hip to form the bony pelvis; Openings on the anterior and posterior surface allow passage of spinal nerves

Coccyx

The lowest bart of the vertebral column that is composed of 4 fused vertebrae

Thorax

Refers to the entire chest region and is formed from the sternum and the ribs and costal cartilages; Functions to enclose and protect the organs in the thoracic and abdominal cavities, providing support for the bones of the upper limbs and playing a role in breathing

Thoracic cage

Final part of the axial skeleton

Sternum

Located anteriorly in the center of the thoracic wall and consists of 3 segments: the manubrium, body, and xiphoid process; The “breastbone”

12 pairs of ribs

Gives structural support to the sides of the thoracic cavity

Costal cartilages

Bars of hyaline cartilage connecting the sternum to the ribs; Contributes to the elasticity of the thoracic cage

12

Humans have__ pairs of ribs that attach to the thoracic vertebrae

True ribs

The first 7 pairs of ribs that join the sternum directly by their costal cartilages; Vertebrosternal

False ribs

Remaining 5 pairs of ribs that do not reach the sternum directly

7

Ribs 8-10 join the cartilages of the __th rib; Vertebrochondral

Floating ribs

Last 2 ribs that have no cartilage; Vertebral; Also considered false ribs

126

There are ___ bones in the appendicular skeleton

Appendicular skeleton bones

Primarily concerned with movement and make up the “appendages” (upper and lower limbs) and includes the girdles that attach them: pectoral and pelvic girdle

Pectoral girdle

Bones of the _______ include the scapula and clavicle

Scapula

Triangular shaped bone that has distinct features that provide attachment for muscles and allow it to articulate with other bones; Shoulder blade

Glenoid fossa

Lateral part of the scapula that is a shallow, cup-like depression that articulates with the rounded head of the humerus to form the glenohumeral joint

Clavicle

S-shaped bone; “Collar bone”

Sternoclavicular joint

Medial end of the clavicle articulates with the manubrium of the sternum forming

Acromioclavicular joint

Lateral end of the clavicle articulates with the acromion of the scapula forming

Upper limb

Each has 30 bones in 3 locations: arm, forearm, and hand

Humerus

Only bone in the arm

Glenohumeral joint

Proximal end (head) of the humerus articulates with scapula to form

Elbow joint

Distal end of the humerus articulates with bones of the forearm to form

Forearm

Composed of the radius and the ulna

Radius

Lateral bone that is narrow at the proximal end and rotates over the ulna in pronation

Ulna

Medial bone that is narrow. at the distal end and has the olecranon process

Interosseus membrane

Diaphysis of the radius and the ulna are connected by _____

Proximal and distal

Two types of radioulnar joints in the forearm

Hand

Composed of the wrist, palm, and fingers

Wrist

Made up of 8 carpal bones arranged in 2 rows

Scaphoid, lunate, triquetrum, pisiform

Carpals proximal row (lateral to medial) listed

Trapezium, trapezoid, capitate, hamate

Carpals distal row (lateral to medial) listed

Palm

Composed of 5 metacarpal bones

Fingers

Each are composed of 3 phalanges: the proximal phalanx, middle phalanx, and distal phalanx, (except the 1st digit which has 2)

Thumb (pollex)

Metacarpals and phalanges are numbered 1-5 starting with the ______

Pelvic girdle

Composed of 2 os coxae (hip bones)