Nurs 1002-Obj #7

Learning Objectives

• Describe the two main divisions of the skeleton.

• Identify bones of the axial and appendicular skeleton and their major markings.

• Describe principle sutures and fontanels.

• Explain skeletal differences between men and women.

• Summarize primary joint classifications.

• Describe structural characteristics of synovial joints.

• Identify major synovial joints of the body.

Main Divisions of the Skeleton

Overview of the Skeletal System

The skeletal system, or skeleton, is composed of bones, cartilage, and ligaments. It provides the structural framework for the body and accounts for approximately 20% of total body mass.

• Axial Skeleton: Forms the longitudinal axis of the body and includes the skull, vertebral column, and thoracic cage.

• Appendicular Skeleton: Comprises the limbs and girdles that attach them to the axial skeleton.

Axial Skeleton

Regions and Functions

The axial skeleton consists of 80 bones divided into three major regions:

• Skull

• Vertebral Column

• Thoracic Cage

Functions of the axial skeleton include:

• Forming the longitudinal axis of the body

• Supporting the head, neck, and trunk

• Protecting the brain, spinal cord, and thoracic organs

Skull: Structure and Bones

The skull is the most complex bony structure in the body and consists of two sets of bones:

• Cranial Bones: Enclose the brain in the cranial cavity and provide sites of attachment for head and neck muscles.

• Facial Bones: Form the framework of the face, contain cavities for special sense organs (sight, taste, smell), provide openings for air and food passage, and anchor facial muscles.

Most skull bones are flat and firmly locked together by immovable joints called sutures, which have a saw-tooth appearance.

Cranial Bones

The cranium is composed of eight cranial bones:

• Parietal Bones (two—left and right)

• Temporal Bones (two—left and right)

• Other Cranial Bones: Frontal, occipital, sphenoid, and ethmoid

Major bone markings include articulations of parietal bones with frontal, occipital, and temporal bones.

Other cavities in the skull:

• Middle and inner ear cavities

• Orbits (house the eyeballs)

Foramina and Openings

The base of the skull contains several named openings (foramina, canals, fissures) that serve as passageways for the spinal cord, major blood vessels, and the 12 cranial nerves.

Sutures

Sutures are immovable joints that connect the bones of the skull. Major sutures include:

• Coronal Suture: Between frontal and parietal bones

• Sagittal Suture: Between right and left parietal bones

• Lambdoid Suture: Between parietal and occipital bones

• Squamous Suture: Between parietal and temporal bones

Fontanels

Fontanels are soft spots in the skull of infants where the bones have not yet fused. They allow for growth and development of the brain and skull during early life.

• Anterior fontanel (largest, closes by 18-24 months)

• Posterior, sphenoidal, and mastoid fontanels

Appendicular Skeleton

Overview and Functions

The appendicular skeleton consists of the bones of the limbs and the girdles that attach them to the axial skeleton. It is responsible for movement and manipulation of objects.

• Pectoral (Shoulder) Girdle: Clavicle and scapula

• Upper Limbs: Humerus, radius, ulna, carpals, metacarpals, phalanges

• Pelvic (Hip) Girdle: Coxal bones (ilium, ischium, pubis)

• Lower Limbs: Femur, tibia, fibula, tarsals, metatarsals, phalanges

Major Bone Markings and Features

• Humerus: Largest bone of the upper limb; articulates with scapula at shoulder and with radius/ulna at elbow.

• Radius and Ulna: Forearm bones; radius is lateral, ulna is medial in anatomical position.

• Carpals: Eight bones forming the wrist.

• Metacarpals: Five bones forming the palm.

• Phalanges: Fourteen bones forming the fingers (three per finger, two in the thumb).

• Femur: Largest and strongest bone in the body; articulates with acetabulum of pelvis and tibia at knee.

• Tibia and Fibula: Lower leg bones; tibia is weight-bearing, fibula is lateral and non-weight-bearing.

• Tarsals: Seven bones forming the ankle and heel (including talus and calcaneus).

• Metatarsals: Five bones forming the foot.

• Phalanges (foot): Fourteen bones forming the toes (three per toe, two in the big toe).

Pelvic Girdle and Sex Differences

The pelvic girdle attaches the lower limbs to the axial skeleton and supports the weight of the upper body. There are notable differences between male and female pelvises:

Summary Table: Axial vs. Appendicular Skeleton

Key Terms and Definitions

• Bone: Rigid organ that constitutes part of the vertebrate skeleton.

• Ligament: Connective tissue that connects bones to other bones.

• Suture: Immovable joint between skull bones.

• Fontanel: Soft spot in infant skull where bones have not fused.

• Foramen: Opening in bone for passage of nerves and blood vessels.

Example Application

Understanding the structure and function of the skeleton is essential for diagnosing fractures, joint disorders, and congenital abnormalities. For example, knowledge of foramina is crucial in neurology and surgery for identifying pathways of nerves and vessels.

Additional info: These notes provide foundational knowledge for further study of joint classifications and synovial joint characteristics, which are covered in subsequent sections of the course.