1. Lesson 1: Skeletal System

2. Lesson 1– Skeletal System
The skeletal system:
Provides shape and support to the body
Protects vital organs
Acts as a set of levers, and together with muscles helps a person move
Produces blood cells
Stores calcium
Skeletal System
The skeletal system refers to the bones that form the framework of the body. An adult human has 206 bones. The skeletal system performs these functions:
Provides shape and support to the body
Protects vital organs
Acts as a set of levers, and together with muscles helps a person move
Produces blood cells
Stores calcium

3. Lesson 1– Types of Bones Long bones Short bones Flat bones
Irregular bones
Types of Bones
Bones vary in shape and size depending on where they are found in the body. Bones are classified by shape.
Long bones are longer than they are wide. Bones of this type form the extremities, or arms and legs.
Short bones have a similar length and width. Bones of this type can be found in the wrists and ankles. They have an outer layer of compact bone and an inner layer of bone with a latticework structure.
Flat bones have a broad shape. Bones of this type can be found in the skull, shoulder blades, and pelvis. They cover organs to protect them or provide a surface for large areas of muscle.
Irregular bones are specialized and do not fit the other types. Examples include the bones of the ear, face, and vertebrae.

4. Lesson 1– Parts of Long Bones
Diaphysis
Epiphysis
Articular cartilage
Periosteum
Medullary canal
Endosteum
Parts of Long Bones
The longest part of a long bone is called the diaphysis, or shaft.
Each end of the shaft is called an epiphysis. A thin layer of articular cartilage covers the epiphysis to absorb shock where two bones meet to form a joint.
The outer part of the bone is made of compact bone tissue, which does not bend easily. It is covered by the periosteum, which is a tough, fibrous tissue. This tissue contains blood vessels, lymph vessels, and osteoblasts for bone growth, repair, and nutrition.
Inside the compact bone is spongy bone. The medullary canal is a cavity in the center of the shaft where marrow is stored. It is lined by the endosteum to keep the cavity intact.

5. Lesson 1– Bone Marrow Red marrow Yellow marrow Bone Marrow
Present in long bones, marrow is important in making blood cells.
Red marrow is found in epiphyses and in certain flat bones. It produces red blood cells, platelets, and some white blood cells. Children have red marrow throughout their bodies. As they become adults, most of it is replaced with yellow marrow.
Yellow marrow, which is mostly made of fat cells, fills the medullary canal. This marrow serves as fat storage and contains blood vessels and some cells that form white blood cells.

6. Lesson 1– Sections of the Skeletal System
Axial skeleton
Appendicular skeleton
Sections of the Skeletal System
The skeletal system is divided into two sections, axial and appendicular.
The axial skeleton forms the main trunk of the body. It includes the skull, spinal column, ribs, and breastbone.
The appendicular skeleton forms the extremities. It includes the shoulder girdle, arm bones, pelvic girdle, and leg bones.

7. Lesson 1– Axial Skeleton: Skull
The skull consists of the cranium and facial bones.
Cranium
1 frontal
2 parietal
2 temporal
1 occipital
1 ethmoid
1 sphenoid
Sutures.
Axial Skeleton: Skull
The skull consists of the cranium and facial bones.
The cranium surrounds and protects the brain. The cranial bones join at points called sutures. At birth, there are two openings in the cranium called fontanels, or “soft spots.” They give space for the skull to enlarge as the brain grows, and they usually close by months of age. The 8 cranial bones include the following:
1 frontal
2 parietal
2 temporal
1 occipital
1 ethmoid
1 sphenoid

8. Lesson 1– Axial Skeleton: Skull (Continued)
Facial bones
5 nasal
2 maxilla
2 lacrimal
2 zygomatic
2 palatine
1 mandible
Sinuses
Axial Skeleton: Skull (continued)
Facial bones are also part of the skull. Facial bones guard and support the eyes, nose, mouth, and ears. Sinuses are air spaces in and around these bones. These spaces allow the voice to resonate to sound stronger. The 14 facial bones include the following:
5 nasal
2 maxilla, or upper jaw
2 lacrimal, or inner aspect of the eyes
2 zygomatic, or cheek
2 palatine, or roof of the mouth
1 mandible, or lower jaw
The mandible is the only movable bone in the face. It contains the sockets for the lower teeth. The maxilliary bones contain the sockets for the upper teeth.

9. Lesson 1– Axial Skeleton: Spinal Column
Vertebrae
Discs
Axial Skeleton: Spinal Column
The spinal column consists of 26 bones called vertebrae. It is also known as the vertebral column. It encloses and protects the spinal cord and supports the head and trunk. Discs of cartilage tissue separate the vertebrae to cushion the bones and allow movement.
The spinal column includes these vertebrae:
7 cervical, or neck
12 thoracic, or chest
5 lumbar, or middle back
1 sacrum
1 coccyx, or tailbone

10. Lesson 1– Axial Skeleton: Thorax
Ribs
Sternum
Manubrium
Gladiolus
Xiphoid process
Axial Skeleton: Thorax
The thorax is also known as the chest cavity. It helps to protect the heart and lungs.
There are 12 pairs of ribs, or costae:
The first 7 pairs are called “true ribs” because they are attached to the sternum, or breastbone.
The next 5 pairs are called “false ribs.”
- The first 3 pairs of these ribs each attach to the cartilage of the rib above it.
- The last 2 pairs have no attachment on the front of the body and are called “floating ribs.”
The sternum includes 3 parts:
The manubrium is the upper region. It is attached by ligaments on both sides to the clavicles, or collarbones.
The gladiolus is the body.
The xiphoid process is a small piece of cartilage at the bottom.

11. Lesson 1– Appendicular Skeleton: Shoulder Girdle
2 clavicles
2 scapulas.
Appendicular Skeleton: Shoulder Girdle
The shoulder girdle is also known as the pectoral girdle. It includes 4 bones:
2 clavicles, or collarbones
2 scapulas, or shoulder bones
The clavicles help brace the shoulders and prevent a person from having too much forward motion. The scapulas provide a place for the arms to be attached, and together with muscles they assist with arm movement.

12. Lesson 1– Appendicular Skeleton: Arms and Hands
Arm bones:
Humerus
Ulna
Radius
Hand bones:
8 carpals
5 metacarpals
14 phalanges
Appendicular Skeleton: Arms and Hands
The bones of each arm include the following:
Humerus, or upper arm bone.
Ulna, or the lower arm bone whose upper end forms the elbow.
Radius, or the lower arm bone on the thumb side.
The bones of each hand include the following:
8 carpals, which form the wrist.
5 metacarpals, which form the palm of the hand.
14 phalanges, which form the fingers.

13. Lesson 1– Appendicular Skeleton: Pelvic Girdle
Pelvic girdle is made of 2 hip bones, which connect at the symphysis pubis.
Each hip bone is composed of 3 sections:
Illium
Ischium
Pubis
Appendicular Skeleton: Pelvic Girdle
The pelvic girdle includes 2 os coxae, or hip bones. They attach to the sacrum in addition to connecting to each other at a joint called the symphysis pubis. Each os coxae consists of these 3 fused sections:
Illium
Ischium
Pubis
The pelvic girdle supports the trunk of the body, in particular the lower soft abdominal organs. It also provides a place for the legs to be attached.

14. Lesson 1– Appendicular Skeleton: Legs and Feet
Leg bones:
Femur
Patella
Tibia
Fibula
Foot bones:
7 tarsals
5 metatarsals
14 phalanges
Appendicular Skeleton: Legs and Feet
The bones of each leg include the following:
Femur, or the thigh bone in the upper leg. It is the longest bone in the body.
Patella, or kneecap.
Tibia, or the shin in the lower leg.
Fibula, which is also in the lower leg.
The bones of each foot include the following:
7 tarsals, which form the ankle. A large tarsal bone called the calcaneous forms the heel.
5 metatarsals, which form the instep of the foot.
14 phalanges, which form the toes.

15. Lesson 1– Joints Joints Ligaments Joints are classified by movement:
Diarthrosis– movable
Amphiarthrosis– partially movable
Synarthrosis– not movable
Joints
Joints are areas where two or more bones connect. Bands of connective tissue called ligaments help hold bones together at joints. Joints are classified by movement.
A diarthrosis joint is movable.
An amphiarthrosis joint is partially movable.
A synarthrosis joint is not movable.