ANATOMY OF THE SKELETAL SYSTEM

206 bones in an adult (~ 350 cartilaginous bones as a developing baby)

Skeleton reaches full maturity by age 25Supports the body and protects vital organsManufactures blood cells at a rate of 1.2

million per secondAllows body movement by connecting with

skeletal muscles

SKELETAL SYSTEM FACTS

Stores excess minerals – primarily calcium and phosphorous

Ligaments connect bone to boneTendons connect bone to muscle2 broad divisions – axial and appendicular

SKELETAL SYSTEM FACTS

Includes the head (cranial and facial), spine, and thorax

80 bones totalPrimary function is to

support and protect the internal organs

AXIAL SKELETON

Cranial BonesMade of 8 bones – parietal (2), temporal (2), frontal, occipital, sphenoid, ethmoid

Fit tightly together without moveable jointsOne purpose is to protect the brain and other organs located in the cranium

BONES OF THE HEAD

Cranial BonesWhen born, joints are not fused – instead connected by cartilage called fontanels (makes the “softspot”)

Skull growth is not complete until age fourAreas where bones join are the sutures Jagged edge of sutures gives added strength

BONES OF THE HEAD

Facial BonesMade of 14 bones – maxilla (2), zygomatic (2), palatine (2), nasal (2), lacrimal (2), inferial nasal concha (2), mandible, vomer

Maxilla and palatine form upper jaw and the roof of the mouthMandible forms the lower jaw – only moveable bone in the skull

BONES OF THE HEAD

Auditory BonesMade of 6 bones – malleus (2), incus (2), stapes (2)

Also known as the hammer, anvil, and stirrupSmallest bones in the bodyNecessary for hearing

BONES OF THE HEAD

Hyoid (1)Only bone that does not articulate with another bone

U-shapedA point of articulation for many muscles (ex: tongue, pharynx)

Found just above the larynx

BONES OF THE HEAD

Vertebral Column (general information)Vertebrae – plural; vertebra – singularMade of 26 vertebrae (originally 34, but 5 sacral

bones fuse together and 4-5 coccygeal bones fuse together.

Intervertebral disks allow the spine to bend and act as shock absorbers – made of cartilage

Have a hollow area for the spinal cord to pass through

BONES OF THE SPINE

Cervical VertebraeFirst 7 vertebrae – make up the neck (C1-C7)C1 – atlas

Point where the head is connected to the spineAllows the head to pivot up and down

C2 – axisLocated right below the atlasAllows the head to swivel left to right

Other cervical vertebrae allow the head to tilt and move in other directions

BONES OF THE SPINE

BONES OF THE SPINE

Thoracic VertebraeMade of 12 vertebrae (T1-T12)

Larger than the cervical vertebrae

Attachment point for the ribs

BONES OF THE SPINE

Lumbar VertebraeMade of 5 vertebrae (L1-L5)Largest vertebraeForm the lower backSupport the weight of the entire upper body

BONES OF THE SPINE

Sacral Vertebrae (or Pelvic Vertebrae)Made of 5 vertebrae fused together (in adults)Also called the sacrum Joined to the hips to form the base of the spine

BONES OF THE SPINE

CoccyxMade of 4-5 vertebrae fused together (in adults)Also called the tailbone or coccygeal vertebraeUsed for muscle attachment and a shock absorber for the spine

BONES OF THE SPINE

Four curvesCervical lordosisThoracic kyphosisLumbar lordosisSacral/coccygeal curve

CURVATURE OF THE SPINE

Provide additional strength and flexibility

Can have excess curvatureScoliosis – excessive lateral curvature

Kyphosis – excessive thoracic curvature (humpback)

Lordosis – excessive lumbar curvature (swayback)

CURVATURE OF THE SPINE

RibsMade of 24 bones (12 pairs)Attaches to the thoracic vertebrae in the back and by cartilage to the sternum in front (the first 7 pairs)

Cartilage is flexible so the ribs can expand and contract during breathing

BONES OF THE CHEST

3 types of ribsTrue ribs- first 7 pairs, attach directly to the sternum

False ribs – next 3 pairs, attaches to the lowest true rib by cartilage

Floating ribs – last 2 pairs, do not attach to the sternum at all, also considered false ribs

BONES OF THE CHEST

BONES OF THE CHEST

SternumKnown as the breast boneContains the manubrium, body, and xiphoid process

Last bone to ossify

BONES OF THE CHEST

General InformationIncludes the shoulders, hips,

arms, and legs126 bones totalPrimary function is support

and to enable movement

APPENDICULAR SKELETON

Consists of 4 bonesAlso known as the pectoral girdle

BONES OF THE SHOULDER

Scapulae (2)Singular is scapulaAlso known as the shoulder bladesContains sockets for the armsDon’t rigidly attach to the axial skeletonOnly articulate with the humerus and clavicle

Clavicle (2)Also known as the collar boneArticulates with the scapula and the sternum

BONES OF THE SHOULDER

Consists of 60 bones

Only 6 are in the arms with the rest in the wrists, hands, and fingers

BONES OF THE UPPER EXTREMITIES

Humerus (2)Makes the upper armArticulates with the scapula, ulna, and radius

BONES OF THE UPPER EXTREMITIES

ForearmConsists of 4 bonesRadius (2)

Located on the lateral side of the forearm (thumb side)

Rotates over the ulnaUlna (2)

Locaed on the medial side of the forearm (little finger side)

Does not move when the arm is rotated

Has a “hook” to attach to the humerus

BONES OF THE UPPER EXTREMITIES

WristThe bones as a group are known as the carpalsConsists of 16 bones (8 on each side) – pisiform, lunate, scaphoid, trapezium, trapezoid, capitate, hamate, triquetrium

The bones are arranged in two rows of 4This allows the wrist to bend in various directions

BONES OF THE UPPER EXTREMITIES

BONES OF THE UPPER EXTREMITIES

Hands and FingersConsists of 38 bonesMetacarpals

These make up the palm of the handThere are 10 of these bones (5 per side)The metacarpal that makes up the thumb is held by ligaments that give it great mobility

Phalanges28 phalanges make up the fingers (14 per side)3 in each finger, 2 for each thumb

BONES OF THE UPPER EXTREMITIES

BONES OF THE UPPER EXTREMITIES

The pelvic girdle is made of a ring of bones: the sacrum makes up the back and the sides are made up of a pair of bones called the coxae

Each coxae is really three bones fused together: ilium, ischium, pubis

Coxae, coxal bone, and pelvic bone all refer to the same thing

BONES OF THE PELVIC GIRDLE

BONES OF THE PELVIC GIRDLE

Similar in basic layout to the upper extremities

Bones are thicker and stronger than in the upper extremities

Each lower limb has 30 bones – 4 in the leg and 26 in the foot and ankle

BONES OF THE LOWER EXTREMITIES

Bones of the LegFemur

Makes up the thighLongest bone in the body

Strongest bone in the body

Attaches to the pelvic girdle at the hip joint

BONES OF THE LOWER EXTREMITIES

TibiaOne of the bones in the lower leg

The main weight bearing bone of the leg

Extends from the knee to the ankle

FibulaMuch thinner than the tibiaFound on the lateral sideDoes not attach to the femur

BONES OF THE LOWER EXTREMITIES

PatellaKneecapFound on top of the joint between the femur and the tibia

Serves as a brace for the patellar tendon to increase leverage on the joint

Also helps to protect the joint from injury

BONES OF THE LOWER EXTREMITIES

Bones of the Ankle and Foot

TarsalsMake up the ankle14 bones (7 per side): talus, calcaneus (heel bone), navicular, cuboid, and 3 cuneiform

Thick and strong to support the weight of the body

Talus connects with the tibia

BONES OF THE LOWER EXTREMITIES

MetatarsalsMake up the base of the footMade of 10 bones (5 per side)Forms the framework of the arches of the foot

PhalangesMade of 28 bones (14 per side)Makes up the toesArranged like the phalanges in the fingers: 2 in each big toe, 3 in every other toe

BONES OF THE LOWER EXTREMITIES

BONES OF THE LOWER EXTREMITIES