The Skeletal System

Introduction -The Basics There are 206 bones in the human body. The skeleton has two major divisions

The axial skeleton forms the long axis of the body and includes the bones of the skull, vertebral column, and rib cage.

The Appendicular skeleton consists of the bones of the upper and lower limbs, and the shoulder bones and hip bones.

The Axial Skeleton The skull consists of two sets of bones – the cranium and the facial bones. There are eight cranial bones and fourteen facial bones.  The joints between bones of the skull are immovable and called sutures.

Baby Skull Sutures

Sutures in Adult Skull

The SPHENOID BONE- acts like a bridge between the cranial & facial bones

The Axial Skeleton Only the mandible is attached by a freely movable joint. The hyoid bone is the only bone in the body that does not articulate (match up with) another bone. The hyoid bone acts as an attachment point for several muscles that help with speech and swallowing. The hyoid bone is attached to the skull by ligaments.

The Axial Skeleton The vertebral column consists of vertebrae separated by disks of fibro-cartilage. 7 cervical vertebrae   12 thoracic vertebrae   5 lumbar vertebrae   The bony thorax forms a cage to protect major organs

SPINAL (VERTEBRAL) COLUMN The spinal column (or vertebral column) extends from the skull to the pelvis and is made up of 33 individual bones termed vertebrae.

The Axial Skeleton The bony thorax is made up of three parts: 1)Sternum 2)Ribs 3)Thoracic vertebrae

The Axial Skeleton You have three different types of ribs True ribs are the first seven pairs of ribs. True ribs attach directly to the sternum by costal cartilages. False ribs are the next five pairs. They either attach indirectly to the sternum or not at all. Floating ribs are the last two pairs of false ribs. They lack sternal attachments.  

The Appendicular Skeleton The 3 parts of the appendicular skeleton are: 1)Limbs (appendages) 2)Pectoral girdle (shoulder) 3)Pelvic girdle (pelvis)

The Appendicular Skeleton The pectoral girdle (or shoulder) is composed of two bones 1)Clavicle – collarbone 2)Scapula – Shoulder blade   The clavicle and the scapula allow the upper limbs to have free movement

The Appendicular Skeleton The arm is formed from a single bone, the humerus. The forearm has two bones: the ulna and radius

The Appendicular Skeleton The hand contains three types of bones: 1)Carpals – wrists 2)Metacarpals – palm 3)Phalanges - fingers

The Appendicular Skeleton The thigh has one bone – the femur.   The lower leg has two bones – the tibia and fibula.

The Appendicular Skeleton The foot has three types of bones: 1)Tarsals – ankle 2)Metatarsals – sole 3)Phalanges - toes

The Appendicular Skeleton The pelvic girdle is made up of the hip bones.   The “hip bones” are composed of three pair of fused bones – the ilium, ischium, and pubic bone.

The Appendicular Skeleton The total weight of the upper body rests on the pelvis. The pelvic girdle protects several organs – the reproductive organs, the urinary bladder, and part of the large intestine.