The skeletal system has several key functions: 1. It provides structure and support for the body, protects vital organs, and allows for movement. 2. Bones act as levers for muscle attachments and movement. 3. Bones store minerals and act as sites for blood cell formation. 4. There are 206 bones in the adult skeleton divided into long, short, flat, irregular, and sesamoid shapes serving different functions. Bones are classified as either axial or appendicular. Surface markings on bones provide attachment points for muscles and allow for vascular and nerve passageways.

1. Unit 4: The Skeleton System
Section 1: Introduction
Anatomy & Physiology
Mrs. DeFord

2. Skeletal System Functions
1. Support
• Organs and tissues of the body are held in place by the skeleton.
• The bones of the legs, pelvic girdle, and vertebral column support
the weight of the erect body.
• The mandible (jawbone) supports the teeth.
2. Protection
• Provides a rigid surface for protection of vital organs:
– The bones of the skull protect the brain.
– Ribs and sternum (breastbone) protect the lungs and heart.
– Vertebrae protect the spinal cord.

3. Skeletal System Functions
3. Movement
• Bones provide a base for muscle attachments.
• Skeletal muscles use the bones as levers to move the body.
4. Reservoir for Minerals and Adipose Tissue
• 99% of the body’s calcium is stored in bone.
• 85% of the body’s phosphorous is stored in bone.
• Adipose tissue is found in the marrow of certain bones.
5. Hematopoiesis
• a.k.a. blood cell formation
• All blood cells are made in the marrow of certain bones.
– 2.6 million red blood cells are produced each second.

4. Skeletal System Introduction
The Skeletal System is composed of the body’s
bones and associated ligaments, tendons, and
cartilages.
• Muscles are connected to bones by
tendons.
• Bones are connected to each other by
ligaments (strong, stretchy bands).
• Where bones meet one another is
typically called an articulation (joint).
• Cartilage serves as the fetal template for
bone formation, and covers the end of
bones, most especially at the joints.

5. Humans are born with @306 bones
that are fused into 206 named
bones in the adult skeleton.
The bones form a rigid framework
to which the softer tissues and
organs of the body are attached.
Skeletal System Introduction

6. The 206 bones that compose the adult
skeleton are divided into five categories
based on their shapes.
Their shapes and their functions are
related such that each categorical shape
of bone has a distinct function.
Bone Classification: Shape

7. Bone Classification: Shape
Classification Features Function(s) Examples
Long
cylinder-like shape, longer
than it is wide
leverage
metacarpals, femur, tibia,
humerus, metatarsals, ulna,
phalanges, radius, fibula
Short
cube-like shape, roughly
equal in length, width, and
thickness
provide stability and
support, while allowing
for some motion
carpals, tarsals
Flat Thin and curved
points of attachment
for muscles; protectors
of internal organs
sternum, ribs, scapulae,
cranial bones
Irregular complex shape protect internal organs vertebrae, facial bones
Sesamoid
small and round;
embedded in tendons
protect tendons from
compressive forces
patellae

8. Each bone belongs to one of 2 large groups:
– Axial Skeleton (80 bones)
• Forms the long axis of the body.
• Includes the bones of the skull, vertebral column, and
thorax.
• Involved in protection and support.
– Appendicular Skeleton (126 bones)
• Bones of upper & lower limbs and the girdles
(shoulder bones and pelvic bones) that attach them
to the axial skeleton.
• Involved in locomotion and manipulation of the
environment.
Skeletal Divisions

9. The purpose of bone
markings are to:
– Join one bone to
another
– Provide a surface for
attachment of
muscles
– Create an opening
for passage of blood
vessels and nerves
– Use as landmarks
Bone Markings (Surface Features)

10. Bone Markings (Surface Features)