Study Notes: Human Axial and Appendicular Skeleton (Anatomy & Physiology)

Articulated Skeleton

Axial Skeleton

The axial skeleton forms the central axis of the human body and provides support and protection for the brain, spinal cord, and vital organs. It consists of the skull, vertebral column, and thoracic cage.

• Skull

  • Cranial bones: Protect the brain and form the structure of the head.

  • Facial bones: Form the face and support sensory organs.

• Hyoid bone: Located in the neck, supports the tongue and is associated with swallowing.

• Vertebral column:

  • Cervical vertebrae: 7 vertebrae in the neck region.

  • Thoracic cage: Includes the sternum and ribs, protects the heart and lungs.

  • Sacrum and Coccyx: Fused vertebrae at the base of the spine.

Appendicular Skeleton

The appendicular skeleton includes the bones of the limbs and girdles, facilitating movement and interaction with the environment.

• Pectoral Girdle: Connects the upper limbs to the axial skeleton.

  • Clavicle

  • Scapula

• Upper Limb:

  • Humerus

  • Radius

  • Ulna

  • Carpals (wrist bones)

  • Metacarpals (hand bones)

  • Phalanges (finger bones)

• Pelvic Girdle: Connects the lower limbs to the axial skeleton.

  • Coxal bones

  • Symphysis pubis

• Lower Limb:

  • Femur

  • Patella

  • Tibia

  • Fibula

  • Tarsals (ankle bones)

  • Metatarsals (foot bones)

  • Phalanges (toe bones)

Disarticulated Axial Skeleton

Skull External Features: Anterior View

The anterior view of the skull reveals the facial bones and openings for nerves and blood vessels.

• Frontal bone

• Nasal bone

• Zygomatic bone

• Maxilla

• Perpendicular plate of ethmoid bone

• Mandible

Skull External Features: Orbit

The orbit houses the eye and is formed by several bones.

• Maxilla

• Lacrimal bone

• Ethmoid bone

• Sphenoid

• Zygoma

Skull External Features: Lateral View

The lateral view of the skull shows the side profile and important landmarks for muscle attachment and articulation.

• Frontal bone

• Parietal bone

• Occipital bone

• Temporal bone

  • External acoustic meatus

  • Styloid process

  • Mastoid process

  • Zygomatic process

• Nasal bone

• Zygomatic bone

• Maxilla

• Mandible

  • Mandibular condyle

  • Mental foramen

  • Coronoid process

• Suture lines

• Lambdoid suture

Skull External Features: Posterior & Superior Views

These views highlight the occipital region and cranial sutures.

• Parietal bone

• Occipital bone

• External occipital protuberance

• Lambdoid suture

Skull External Features: Base

The base of the skull contains openings for nerves and blood vessels.

• Maxilla

• Palatine bone

• Temporal bone

  • Mandibular fossa

  • Foramen magnum

Skull Internal Features: Base

The internal base of the skull supports the brain and contains foramina for cranial nerves.

• Ethmoid bone

  • Cribriform plate

• Sphenoid bone

  • Sella turcica

• Temporal bone

  • Jugular foramen

  • Foramen magnum

Vertebral Column

General Features

The vertebral column supports the body and protects the spinal cord. It is divided into regions and consists of individual vertebrae separated by intervertebral discs.

• Cervical vertebrae

• Thoracic vertebrae

• Lumbar vertebrae

• Sacrum

• Coccyx

• Intervertebral discs

• Intervertebral foramen

Cervical Vertebrae General Features

Cervical vertebrae are the smallest and lightest vertebrae, allowing for a wide range of head movement.

• Atlas (C1)

• Axis (C2)

  • Dens (odontoid process)

• Transverse process

• Vertebral foramen

• Spinous process (bifid)

Thoracic Vertebrae General Features

Thoracic vertebrae articulate with the ribs and have long spinous processes.

• Transverse process

• Lamina

• Pedicle

• Superior/inferior articulating facets

• Spinous process

• Vertebral foramen

Lumbar Vertebrae General Features

Lumbar vertebrae are large and robust, supporting much of the body's weight.

• Spinous process

• Lamina

• Transverse process

• Pedicle

• Vertebral foramen

• Superior/inferior articulating facets

• Body

Sacrum Features

The sacrum is a triangular bone at the base of the spine, formed by the fusion of five sacral vertebrae.

• Sacral base

• Sacral canal

• Sacral ala

• Sacral promontory

• Sacral foramina

Coccyx

The coccyx, or tailbone, is attached to the inferior sacrum and consists of fused vertebrae.

• Serves as an attachment site for ligaments and muscles.

Thoracic Cage

Sternum

The sternum is a flat bone located in the center of the chest, forming the anterior portion of the thoracic cage.

• Manubrium

• Jugular notch

• Clavicular notch

• Body

• Xiphoid process

Ribs

The ribs are curved bones that form the sides of the thoracic cage, protecting the heart and lungs.

• True ribs (attached directly to sternum)

• False ribs (attached indirectly or not at all)

• Floating ribs (not attached to sternum)

Key Table: Classification of Vertebrae

Region	Number of Vertebrae	Main Features
Cervical	7	Small, bifid spinous process, transverse foramen
Thoracic	12	Articulate with ribs, long spinous process
Lumbar	5	Large body, short spinous process
Sacral	5 (fused)	Triangular, forms sacrum
Coccygeal	3-5 (fused)	Small, forms coccyx

Key Terms & Definitions

• Foramen: An opening or hole in a bone for passage of nerves and blood vessels.

• Process: A projection or outgrowth of bone for muscle attachment or articulation.

• Suture: An immovable joint between skull bones.

• Condyle: A rounded articular projection.

• Fossa: A shallow depression in a bone.

Example: Clinical Application

• Fracture of the clavicle: Common injury that affects the pectoral girdle and can impact arm movement.

• Herniated disc: Occurs when the intervertebral disc protrudes, compressing spinal nerves and causing pain.