Human Biology

The Skeletal System

The Skeletal System… The skeletal system is

the body’s living framework

It consists of living material embedded in a matrix of nonliving material

The Skeletal System… Made up of bones, cartilage, ligaments, and

tendons Cartilage-dense, fibrous, flexible connective

tissue Ligaments-connective tissue that holds bones

together Tendons- connective tissue that attaches

bones to muscle Consists of approximately 206 bones

The Skeletal System…Functions Provides shape and support Allows movement

Almost all bones are attached to muscles As muscles contract, or shorten, they pull on

bones causing them to move Protects tissues and organs

Ex: vertebral column protects spinal cord Rib cage protects internal organs

The Skeletal System… Functions Stores certain materials

Some of these materials give bones their stiffness, others play roles in blood clotting, nerve functions and muscle activity

If the level of these substances in the blood falls below the normal range, the body will begin to remove them from where they are stored within the bones

The Skeletal System… Functions Produces blood cells

Red cells – carry oxygen White cells – destroy harmful bacteria

Development of Bones... Many bones are

formed from a type of connective tissue called cartilage Cartilage is a stiff,

jellylike material Strong enough to

provide support, flexible enough to bend and twist

Development of Bones… In newborns, many bones are

almost all cartilage The process of replacing

cartilage with bone begins about 7 months before birth

The process continues until the age of 25 or so

Some forming and reforming of bones still occurs in adulthood, particularly where bone is under a great deal of stress

Development of Bones… In some places, the cartilage remains

unchanged Places where bone meets bone Ex: knee, ankle, elbow Two jobs in these places

Cushion bones against sudden jolts (jumping or running)

Provides a slippery surface for bones to move without rubbing against each other

Development of Bones… Bone growth

Growth takes place at both ends of long bones

Growth region is called Epiphyseal plate Layer of cartilage in which mitosis takes place

Ossification Process of cartilage being replaced by bone

Structure of Bones… Bones are one of the

toughest yet lightest materials in your body

Bones make up barely 14% of your body’s mass

Structure of Bones… Bones = living material embedded in a

matrix of non-living material Osteocytes- living cells embedded in a

network of tough protein fibers called collagen

Non-living part of bone- compounds containing calcium and phosphorous that surround the osteocytes and make bone hard

Structure of Bones… Periosteum

Covers all bones and helps to connect them to muscles

Provides a rich blood supply to nourish the bone

Shaft Middle portion of a typical long bone

Central cavity surrounded by a hard bony material called compact bone

Structure of Bones… Haversian canals

Small channels that run through compact bone and contain the blood vessels that nourish the osteocytes

Structure of Bones… Central cavity of long

bones Filled with yellow

marrow Stores fat

Epiphyseal line The shaft is separated

from the ends by this line Marks the area where

growth formerly took place

Structure of Bones… In flat bones and the ends of long bones,

the hard material is very thin Underneath hard material = spongy bone Spongy bone mitigates shock, reduces the

potential for injury during periods of physical exertion or as a result of a blow to the body

In some bones, the spongy material contains red marrow in which red and white blood cells are produced

Classification of Bones… Bones are classified according to their shape

Long bones (arms and legs) – support weight and are involved in movement

Flat bones (skull, sternum) – protect underlying organs

Short bones (wrist, ankles) – provide great flexibility and precise movements

Irregular bones (ribs, scapula) – adaptations that provide for specific needs involving support, protection, and/or articulation

Structure of Skeleton… The skeleton consists

of approximately 206 bones

Two main divisions Axial skeleton Appendicular

skeleton

Structure of Skeleton… Axial skeleton

Central framework of support and protection

Consists of 80 bones including the skull, facial bones, vertebral column, and rib cage

Structure of Skeleton… Function of axial skeleton

Skull – protects brain 26 bones of vertebral column – holds body upright

and protects spinal cord Vertebral column – consists of 5 regions: cervical, thoracic,

lumbar, sacral, and coccygeal Rib cage – twelve pairs of ribs plus sternum

Each rib is attached to the vertebral column Only 7 pair of “true” ribs that are attached to the sternum by

cartilage The other 5 pair “false” ribs do no attach to sternum Function of rib cage is to protect organs of thoracic cavity

Structure of Skeleton… Appendicular

skeleton 126 bones in the

pectoral girdle, the pelvic girdle, arms, and legs

Structure of Skeleton… Function of appendicular skeleton

Pectoral girdle – provides support for arms and provides for their broad range of movement

Muscles attach the pectoral girdle to the axial skeleton

Pelvic girdle attaches directly to the lower part of the vertebral column

Structure of Skeleton… Skeletal joints

Joint – any place where two bones come close together Keeps bones far enough apart so they don’t rub

against each other Holds the bones in place

Six kinds of joints Pivot, ball-and-socket, hinge, saddle, gliding, and

Ellipsoid

Structure of Skeleton… Skeletal Joints

Focus on three Pivot joint- allows

for rotation of one bone around another Ex: joint of head on

neck Allows head to move

up and down as well as side to side

Structure of Skeleton… Skeletal joints, cont.

Ball-and-socket joint- provides for circular motion Ex: shoulder

Hinge joint – allows movement forward and backward with little side to side Ex: elbow, knee

Structure of Skeleton… Bones to know

Cranium

Structure of Skeleton… Vertebral column

5 parts Cervical Thoracic Lumbar Sacral coccygeal

Structure of Skeleton… Clavicle Scapula Humerus Ulna Radius Carpals Metacarpals phalanges

Structure of Skeleton… Ribs Sternum Femur Patella Fibula Tibia Tarsals Metatarsals phalanges

Injuries to Skeleton… Sprain

Ligaments or tendons get torn or pulled beyond their normal stretching range Painful, yet still able to function

Fracture A break in a bone

Bone is a living tissue; begins to heal almost immediately

Dislocation When a bone is forced out of its joint

Can be serious Bone can usually be pushed back into place by a doctor

Review of Skeletal System… Bones are fastened together by connective tissues

called ligaments Tendons are connective tissues that connect

muscles to bone The skeletal system has 5 important functions:

provides shape and support, allows movement, protects tissues and organs, produces blood cells, stores certain materials

Review of Skeletal System… The human skeleton is divided into 2 main

parts: the axial skeleton and the appendicular skeleton Axial skeleton: skull, ribs, breastbone,

vertebral column Appendicular skeleton: pectoral girdle, pelvic

girdle, arms and legs

Review of Skeletal System… Cartilage: a flexible connective tissue that

supports, acts as a shock absorber, and cushions other skeletal parts

Joint: a place where two bones come close together

Most common injuries to skeletal system Sprains, fractures, dislocations