Lab Practical 1 Study Guide: The Human Skeleton

The Human Skeleton: Axial and Appendicular Divisions

Overview of the Human Skeleton

The human skeleton is divided into two main parts: the axial skeleton and the appendicular skeleton. Understanding the structure and function of these divisions is essential for identifying bones and their roles in the body.

• Axial Skeleton: Forms the central 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

Main Components of the Axial Skeleton

• Skull: Protects the brain and forms the structure of the face.

• Vertebral Column: Supports the body and protects the spinal cord.

• Thoracic Cage: Includes the ribs and sternum, protecting the heart and lungs.

Example: The skull, vertebral column, and rib cage are all part of the axial skeleton.

Bones of the Skull

• Frontal Bone: Forms the forehead and the superior part of the eye sockets.

• Parietal Bones (paired): Form the sides and roof of the cranial cavity.

• Occipital Bone: Forms the posterior and base of the skull; contains the foramen magnum.

• Temporal Bones (paired): Form the lower sides of the skull and house the structures of the ears.

Facial Bones

• Mandible: The lower jawbone; the only movable bone of the skull.

• Maxilla: The upper jawbone; forms the upper dental arch and part of the orbit.

Hyoid Bone

• Location: Situated in the anterior neck between the mandible and larynx.

• Function: Serves as an attachment site for tongue and neck muscles; does not articulate directly with other bones.

Example: The hyoid bone is unique because it is not connected to any other bone in the skeleton.

Vertebral Column

• Cervical Vertebrae (C1–C7): The seven vertebrae of the neck. C1 is the atlas, and C2 is the axis.

• Thoracic Vertebrae (T1–T12): The twelve vertebrae of the upper and mid-back; each articulates with a pair of ribs.

• Lumbar Vertebrae (L1–L5): The five vertebrae of the lower back; largest and strongest vertebrae.

Special Vertebrae

• Atlas (C1): Supports the skull; allows nodding motion.

• Axis (C2): Has the odontoid process (dens) for rotation of the head.

Example: The atlas and axis form the joint that allows you to shake your head "no."

Appendicular Skeleton

Overview of the Appendicular Skeleton

The appendicular skeleton includes the bones of the limbs and the girdles that attach them to the axial skeleton. It is essential for movement and manipulation of the environment.

Bones of the Upper Limb

• Scapula: Shoulder blade; connects the humerus with the clavicle.

• Clavicle: Collarbone; acts as a strut to support the shoulder.

• Humerus: Upper arm bone; articulates with the scapula at the shoulder and the radius and ulna at the elbow.

• Radius: Lateral bone of the forearm (thumb side).

• Ulna: Medial bone of the forearm (pinky side); forms the elbow joint with the humerus.

• Carpals: Eight small bones forming the wrist.

• Metacarpals: Five bones forming the palm of the hand.

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

Bones of the Lower Limb

• Ilium: The broad, upper part of the hip bone.

• Pubis: The anterior part of the pelvic bone.

• Ischium: The lower, posterior part of the pelvic bone.

• Femur: Thigh bone; the longest and strongest bone in the body.

• Tibia: Shin bone; the larger, medial bone of the lower leg.

• Fibula: The slender, lateral bone of the lower leg.

• Tarsals: Seven bones forming the ankle and proximal foot.

• Metatarsals: Five bones forming the midfoot.

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

Table: Comparison of Axial and Appendicular Skeleton

Division	Main Components	Function
Axial Skeleton	Skull, vertebral column, thoracic cage	Protection of vital organs, support
Appendicular Skeleton	Limb bones, pectoral and pelvic girdles	Movement, manipulation of environment

Additional info: The appendicular skeleton is critical for locomotion and interaction with the environment, while the axial skeleton provides the main support and protection for the central nervous system and thoracic organs.