Anatomy & PhysiologyScience and Technology
Divisions of the Skeletal System
The skeletal system includes all of the bones, cartilages, and ligaments of the body that support and give shape to the body and body structures. The skeleton consists of the bones of the body. For adults, there are 206 bones in the skeleton. Younger individuals have higher numbers of bones because some bones fuse together during childhood and adolescence to form an adult bone. The primary functions of the skeleton are to provide a rigid, internal structure that can support the weight of the body against the force of gravity, and to provide a structure upon which muscles can act to produce movements of the body. The lower portion of the skeleton is specialized for stability during walking or running. In contrast, the upper skeleton has greater mobility and ranges of motion, features that allow you to lift and carry objects or turn your head and trunk.
In addition to providing for support and movements of the body, the skeleton has protective and storage functions. It protects the internal organs, including the brain, spinal cord, heart, lungs, and pelvic organs. The bones of the skeleton serve as the primary storage site for important minerals such as calcium and phosphate. The bone marrow found within bones stores fat and houses the blood-cell producing tissue of the body.
The skeleton is subdivided into two major divisions—the axial and appendicular.
The Axial Skeleton
The skeleton is subdivided into two major divisions—the axial and appendicular. The axial skeleton forms the vertical, central axis of the body and includes all bones of the head, neck, chest, and back ([link]). It serves to protect the brain, spinal cord, heart, and lungs. It also serves as the attachment site for muscles that move the head, neck, and back, and for muscles that act across the shoulder and hip joints to move their corresponding limbs.
The axial skeleton of the adult consists of 80 bones, including the skull, the vertebral column, and the thoracic cage. The skull is formed by 22 bones. Also associated with the head are an additional seven bones, including the hyoid bone and the ear ossicles (three small bones found in each middle ear). The vertebral column consists of 24 bones, each called a vertebra, plus the sacrum and coccyx. The thoracic cage includes the 12 pairs of ribs, and the sternum, the flattened bone of the anterior chest.
The Appendicular Skeleton
The appendicular skeleton includes all bones of the upper and lower limbs, plus the bones that attach each limb to the axial skeleton. There are 126 bones in the appendicular skeleton of an adult. The bones of the appendicular skeleton are covered in a separate chapter.
The skeletal system includes all of the bones, cartilages, and ligaments of the body. It serves to support the body, protect the brain and other internal organs, and provides a rigid structure upon which muscles can pull to generate body movements. It also stores fat and the tissue responsible for the production of blood cells. The skeleton is subdivided into two parts. The axial skeleton forms a vertical axis that includes the head, neck, back, and chest. It has 80 bones and consists of the skull, vertebral column, and thoracic cage. The adult vertebral column consists of 24 vertebrae plus the sacrum and coccyx. The thoracic cage is formed by 12 pairs of ribs and the sternum. The appendicular skeleton consists of 126 bones in the adult and includes all of the bones of the upper and lower limbs plus the bones that anchor each limb to the axial skeleton.
Which of the following is part of the axial skeleton?
- shoulder bones
- thigh bone
- foot bones
- vertebral column
Which of the following is a function of the axial skeleton?
- allows for movement of the wrist and hand
- protects nerves and blood vessels at the elbow
- supports trunk of body
- allows for movements of the ankle and foot
The axial skeleton ________.
- consists of 126 bones
- forms the vertical axis of the body
- includes all bones of the body trunk and limbs
- includes only the bones of the lower limbs
Critical Thinking Question
Define the two divisions of the skeleton.
The axial skeleton forms the vertical axis of the body and includes the bones of the head, neck, back, and chest of the body. It consists of 80 bones that include the skull, vertebral column, and thoracic cage. The appendicular skeleton consists of 126 bones and includes all bones of the upper and lower limbs.
Discuss the functions of the axial skeleton.
The axial skeleton supports the head, neck, back, and chest of the body and allows for movements of these body regions. It also gives bony protections for the brain, spinal cord, heart, and lungs; stores fat and minerals; and houses the blood-cell producing tissue.
- Anatomy & Physiology
- Unit 1: Levels of Organization
- An Introduction to the Human Body
- The Chemical Level of Organization
- The Cellular Level of Organization
- The Tissue Level of Organization
- Unit 2: Support and Movement
- The Integumentary System
- Bone Tissue and the Skeletal System
- Axial Skeleton
- The Appendicular Skeleton
- Muscle Tissue
- The Muscular System
- Interactions of Skeletal Muscles, Their Fascicle Arrangement, and Their Lever Systems
- Naming Skeletal Muscles
- Axial Muscles of the Head, Neck, and Back
- Axial Muscles of the Abdominal Wall, and Thorax
- Muscles of the Pectoral Girdle and Upper Limbs
- Appendicular Muscles of the Pelvic Girdle and Lower Limbs
- Unit 3: Regulation, Integration, and Control
- The Nervous System and Nervous Tissue
- Anatomy of the Nervous System
- The Brain and Cranial Nerves
- The Autonomic Nervous System
- The Neurological Exam
- The Endocrine System
- An Overview of the Endocrine System
- The Pituitary Gland and Hypothalamus
- The Thyroid Gland
- The Parathyroid Glands
- The Adrenal Glands
- The Pineal Gland
- Gonadal and Placental Hormones
- The Endocrine Pancreas
- Organs with Secondary Endocrine Functions
- Development and Aging of the Endocrine System
- Unit 4: Fluids and Transport
- The Cardiovascular System: Blood
- The Cardiovascular System: The Heart
- The Cardiovascular System: Blood Vessels and Circulation
- The Lymphatic and Immune System
- Anatomy of the Lymphatic and Immune Systems
- Barrier Defenses and the Innate Immune Response
- The Adaptive Immune Response: T lymphocytes and Their Functional Types
- The Adaptive Immune Response: B-lymphocytes and Antibodies
- The Immune Response against Pathogens
- Diseases Associated with Depressed or Overactive Immune Responses
- Transplantation and Cancer Immunology
- Unit 5: Energy, Maintenance, and Environmental Exchange
- The Respiratory System
- The Digestive System
- Metabolism and Nutrition
- The Urinary System
- Physical Characteristics of Urine
- Gross Anatomy of Urine Transport
- Gross Anatomy of the Kidney
- Microscopic Anatomy of the Kidney
- Physiology of Urine Formation
- Tubular Reabsorption
- Regulation of Renal Blood Flow
- Endocrine Regulation of Kidney Function
- Regulation of Fluid Volume and Composition
- The Urinary System and Homeostasis
- Fluid, Electrolyte, and Acid-Base Balance
- Unit 6: Human Development and the Continuity of Life
- The Reproductive System
- Development and Inheritance