The Skeletal and Muscular Systems

The Skeletal System

• The bones of the body make up the skeletal system (206 bones in adults)

• FUNCTION: Bones provide protection for internal organs and work with muscles to enable movement

Label the Skeleton…

Structure of Bones• There are two layers of bone

– 1st LAYER: The outer compact bone-dense connective tissue with a calcium salt matrix (hard)• Bone cells release calcium in rings

forming tubes called Haversian canals

– 2nd LAYER: The inner layer of spongy bone with many cavities… • (bone marrow makes blood cells and

platelets some bone marrow stores fats for energy)

– Covering-tough exterior membrane called the periosteum

Joints

• The place where two bones meet are called joints

• A tough connective tissue called cartilage cushions the bones at the joints

• Bands of connective tissue called ligaments hold bones together

anterior cruciate ligament

cartilage

Types of Joints

• Ball-and-socket joints: allow the widest range of motion – backward, forward, sideways, and in a circle– Hips and shoulders

• Pivot joints: allow a rotation movement– Vertebrae in the neck

• Hinge joints: allow bending and straightening– Knees and knuckles

Ball-and-socket joints

Pivot Joints

Hinge Joints

More Joint Types

• Gliding joints: allow a sliding motion– Wrists and ankles

• Saddle joint: allows rotation and bending– At the base of the thumb

Gliding Joints

Hinge Joints

Saddle Joint

Muscular System

• Although bones allow for movement, they couldn’t do so without the muscular system

• Your body has over 600 muscles

• All muscles are specialized for contraction

"It eats meat. We're meat!” -From Zathura

Types of Muscles

• Smooth muscle – found in organs and blood vessels…under involuntary control

• Cardiac muscle – found only in the heart…under involuntary control

• Skeletal muscle – attached to bones by strips of connective tissue called tendons

Skeletal muscle

Smooth muscle

Cardiac muscle

How they work…

• Muscles receive a nerve impulse with causes them to contract…

• They are attached to bones in opposing pairs– Flexor muscles cause a joint to bend– Extensor muscles cause a joint to straighten

• Connective tissues called tendons connect the muscles to the bones

Relationships…

• The muscular and skeletal systems work together to allow movement.

• The circulatory system brings oxygen (respiratory) and nutrients (digestive) to the muscles and removes wastes (excretory).

• The nervous system tells the muscles to move (voluntarily and involuntarily).