Do Now

• What are the major organs of the skeletal system?

• What are the major functions of the skeletal system?

• What are the 4 different types of tissues?

Chapter 5

The Skeletal System

Bones through Life

By looking at bones you can determine:

• Age

• Sex

• Some information about an individuals lifestyle

Cartilage before bone• Bones develop from cartilage• If cartilage is present bones can

still grow• Bones are young if they have

cartilage

Growing and Changing

• All during life minerals are deposited and removed from bone

• Childhood – minerals deposited faster than lost

• Middle age – deposit = lost

• Old age – minerals are lost faster than they are deposited

• As people age the rib bones gradually change shape over the years – they become cup-shaped and jagged

Pelvic Girdle Changes

• Females have wider pelvises than males – necessary for childbearing and childbirth

Female

Male

Male or Female?

• Female skull is rounder and smaller than the male’s

• The female forehead is longer vertically and the jaw is smaller

• Female sacrum is wider and shorter than the male’s

• Female tailbone is more moveable than in a male

Skulls Grow

• Young people’s skulls have bones that are not fused together – fontanelles or soft spots

• Adults have skull bones that are fused together

Bones Tells a Story

• To determine whether someone is right or left handed, you can compare the size of the bones

• Limbs that are used are slightly larger

• Broken bones can be detected by hairline scars

• Arthritis and osteoporosis can also be seen in skeletal remains

Do Now

• What are the major organs of the skeletal system?

• What are the major functions of the skeletal system?

• What are the 4 different types of tissues?

Chapter 5

The Skeletal System

Major Functions of the Skeletal System

• Protects the body• Motion

The Skeleton is divided into two divisions:

1. Axial Skeleton – spine, ribs, skull

2. Appendicular Skeleton – Appendages – arms, legs and hips

Major Organs of the Skeletal System

1. Joints – place where two bones meet

2. Cartilages – flexible connective tissue, flexible matrixex. Nose, ears

3. Ligaments – joins bone to bone at joints

4. Bones – hard, rigid connective tissue, matrix – lots of calcium

Bones: An Overview

Functions of the Bones

The Five Functions that bones perform:

1. Support – supports and anchors all soft organs

2. Protection – protects soft body organs

3. Movement – muscles attach to bones by tendons- bones are used as levers to move the body

4. Storage – stores fat, minerals (Ca and P)

5. Blood Cell Formation – Hematopoiesis – occurs in marrow cavities

Classification of Bones

• 206 bones

Two Types of Bone Tissue

1. Compact Bone – dense and smooth

2. Spongy bone – small needlelike pieces of bone and open space

Bones are classified into 4 groups based on shape

1. Long Bones

• Longer than wide• Shaft with a head at

both ends (compact bone)

Ex. Arms and legs

2. Short Bones

• Cube shaped, spongy bones

Ex. Wrist and ankle bones

3. Flat Bones

• Thin, flattened and usually curved

• Compact sandwiches spongy

4. Irregular Bones

• Do not fit in another group

Ex. Hips, vertebrae

Structure of a Long BoneGross Anatomy

• Diaphysis (shaft) – length of bone, compact bone

• Periosteum – membrane around the bone that contains blood vessels and nerves

• Epiphyses – ends of a long bone

• Epiphyseal Plate – growth plate – young bones lengthwise growth of a bone

• Bone Markings – sites of attachment for muscles, tendons and ligaments – blood vessels and nerves pass through

• Red Marrow – forms RBC’s – tips of bones

• Yellow marrow – storage area for fat – middle of bones

Bones – Microscopic Anatomy

Osteocytes

• Mature bone cells

• Osteoblasts – formed from osteocytes – bone forming cells (building) – capable of depositing calcium

• Osteoclasts – bone destroying cells – capable of reabsorbing calcium

• Osteocyctes are responsible for bone growth and changes in bone shape

• Bones have their hardness because of calcium deposits.

• Haversian canals run through the bones and contain blood vessels and nerves.

Bone Formation, Growth and Remodeling

• Ossification is the process of bone formation

• Bone is an active and dynamic tissue

Bones are continually remodeled in response to changes in two factors:

1. Calcium levels in the blood

2. The pull of gravity and muscles on the skeleton

Rickets

• A disease of children in which bones fail to calcify

• As a result, bones soften and a definite bowing of the weight bearing bones of the legs occurs

Bone Fractures

• Despite their remarkable strength bones are subject to breaks (fractures)

Youth

• Experience exceptional trauma that twists or smashes the bones

Old Age

• Bones are thin and they weaken

A fracture in treated by a reduction.

• Closed Reduction – bone ends are coaxed back into their normal position by physicians hands

• Open Reduction – surgery is performed and bone ends are secured by pins and/or wires

• A simple facture heals in 6 to 8 weeks.

The Four Major Events of Bone Repair

Step 1

• Hematoma is formed within 6 to 8 hours.

• Formed from escaped blood from the broken blood vessels.

• Hematoma is a mass of clotted blood. The area is inflamed and swollen.

Step 2

• Fibrocartilage callus

• splints the bone

• Lasts for 3 weeks

• Tissue a repair begins

• New capillaries are formed

Step 3

• Bony Callus

• 3 to 4 months

• The fibrocartilage is converted to a bony callus (spongy bone) by osteoblasts

Step 4

• Remodeling

• Spongy bone is converted to compact bone

• Remodeling occurs in response to stresses placed on the bone

Bones in the Human Skeleton

Joints

Joints = articulations

Two Functions1. Hold the bones together securely

2. Gives the rigid skeleton mobility

Structure determines strength and flexibility

• No movement- very strong but inflexible

• Fairly free movement – flexible but not as strong – Prone to displacement

Movement at joints is determined by:

1. Shape of the articulating bones

2. Flexibility of ligaments that bind the bones together

3. Tension of associated muscles and tendons

Classification of Joints

• Structurally – based on anatomical characteristics

• Functionally – type of movement they permit

Functional Classification

a. Synarthrosis - immovable joints – axial skeleton

b. Amphiarthrosis - slightly moveable joint

c. Diarthrosis - freely moveable joints – synovial joints - limbs

Structural Classification

a. Fibrous – no synovial cavity – bones held together by fibrous connective tissue

ex. Sutures of the skull

b. Cartilaginous – lack synovial cavity - bone ends are connected by cartilage

ex. spine

c. Synovial – synovial cavity – united by the dense irregular connective tissue of an articular capsule and often accessory ligaments

Ex. Knee, elbow

Fibrous Joints

Little or no movement

Suture – unites bones – skull

• Syndesmosis – distance between the articulating bones and the amount of dense fibrous connective tissue is greater than in a suture

Gomphosis – cone shaped pegs fits into a socket - teeth

Cartilaginous Joints

• Little or no movement

• Bones are connected tightly by fibrocartilage or hyaline cartilage

1. Synchondrosis – connecting material is hyaline cartilage – ex. – growth plate

2. Symphysis – bones are connected by a broad flat disc of fibrocartilage – ex. – between vertebrae

Synovial Joints

• Space between articulating bones

• Allows joint to be freely moveable

• Bones covered by articular cartilage (reduces friction and absorbs shock)

Structure of a Synovial Joint

• Articular capsule surrounds the synovial joint and unites articulating bones

Two Layers

1. outer fibrous capsule (attaches to periosteum of articulating bones, fibers arranged in parallel bundles called ligaments)

2. Inner synovial membrane

secrets synovial fluid which reduces friction by lubricating the joint

Accessory Ligaments

• Outside and inside the articular capsule

• Ex. In the knee – outside – MCL and LCL

• Inside – ACL and PCL

Menisci

• Pads of fibrocartilage that lies between the articulating surfaces

• Allows two bones of different shapes to fit more tightly

• Maintain stability of the joint

• Direct flow of synovial fluid to areas of greatest friction

Types of Synovial Joints

Shape of articulating surfaces vary and thus various types of

movement are possible

Planar Joints• flat or slightly curved• Side to side and back and forth

gliding movements• Intertarsal, intercarpal

Hinge Joints

• Convex surface fits into concave surface

• Knee, elbow, ankle

Pivot Joints

• Rounded or pointed surface of one bone articulates with a ring formed partly by another bone and partly by a ligament

• Ex. Radioulnar joint

Condyloid Joints

• Convex oval-shaped projection of one bone fits into the concave oval-shaped depression of another bone

• Ex. wrist

Saddle Joint

• One surface is saddle shaped and the other bone fits on it

• Ex. thumb

Ball and Socket Joints

• Ball like surface of one fits into cup like surface of the other

• Ex. Hip and shoulder

Dislocation

• When a bone is forced out of its normal position in the joint cavity

• Reduction - Process of returning the bone to its proper position

Common Disorders

Inflammatory Disorders of the Joints

Sprain

• Ligaments or tendons reinforcing a joint are damaged by excessive stretching or they are torn away from the bone

Osteoarthritis

• Most common• Chronic degenerative condition of the

aged• Cartilage breaks down• Exposed bones then form bone spurs• Movement is restricted – stiffness

results

Rheumatoid Arthritis

• Chronic inflammatory disorder

• Autoimmune disease – body’s immune system attempts to destroy its own tissues

• Ages: 40-50 - 3 times as many females as males

• Bones eventually fuse

Gouty Arthritis (Gout)• Uric acid accumulates in the blood

and is deposited as needle shaped crystals in the soft tissue of the joints

• Big toe• Common in males after 30 - immobile

The End