Human Skeleton Overview Quiz

Study Notes

Axial Skeleton Overview

The axial skeleton is made up of 80 named bones.
It supports the body and protects vital organs.

Appendicular skeleton

The appendicular skeleton is made up of 126 named bones.
It allows for movement and manipulation of the environment.

Anatomical Terminology

Foramen: A hole or opening in a bone.
Fossa: A depression or hollow in a bone.
Process: A projection or outgrowth from a bone.
Condyle: A rounded projection at the end of a bone, usually for articulation with another bone.

Bones of the Skull

Frontal bone: Forms the forehead.
Parietal bones (2): Form the sides and top of the skull.
Occipital bone: Forms the back of the skull.
Temporal bones (2): Form the sides and base of the skull.
- External auditory meatus: Opening for the ear canal.
- Mastoid process: Located behind the ear.
- Styloid process: A slender projection that helps with tongue movement.
Sphenoid bone: A complex bone located in the middle of the skull.
- Optic foramen: Allows passage for optic nerves.
- Sella turcica: A depression that houses the pituitary gland.
Ethmoid bone: Forms part of the roof of the nose and the floor of the skull.
- Perpendicular plate: Forms the upper part of the nasal septum.
- Cribiform plate: Perforated plate that allows passage of olfactory nerves for smell.
Zygomatic bones (2): Form the cheekbones.
Lacrimal bones (2): Forms the medial walls of the orbits (eye sockets).
Nasal bones (2): Form the bridge of the nose.
Inferior nasal concha bones (2): Also called turbinates, form part of the nasal cavity.
Maxillae (2): Form the upper jaw, parts of the hard palate, and the floor of the orbits.
Palatine bones (2): Form the back of the hard palate.
Vomer bone: Forms the bottom part of the nasal septum.
Mandible (dentary): Forms the lower jaw.
- Condylar process: Articulates with the temporal bone.
- Coronoid process: Attachment site for muscles.
Hyoid bone: U-shaped bone located in the neck, supports the tongue and swallowing muscles.

Sutures

Sutures are immovable joints that connect the bones of the skull.

Fontanels

Fontanels are soft spots on a baby's skull, which allow the skull to expand as the brain grows.

Sinuses

Sinuses are air-filled cavities in the skull that reduce the weight of the skull and are lined with mucous membranes.
- Frontal sinus: Located in the frontal bone.
- Maxillary sinus: Located in the maxillae.
- Sphenoidal sinus: Located in the sphenoid bone.
- Ethmoid sinus: Located in the ethmoid bone.

Nasal Septum

The nasal septum is the wall that divides the nasal cavity into two chambers.
- Ethmoid (perpendicular plate): Forms the superior portion of the septum.
- Vomer bone: Forms the inferior portion of the septum.
- Septal cartilage: Forms the anterior portion of the septum.

Orbit

The orbit is the bony socket that houses the eyeball. It is formed by several bones:
- Frontal bone
- Lacrimal bone
- Nasal bone
- Sphenoid bone
- Zygomatic bone
- Ethmoid bone
- Maxilla

Vertebral Column

The vertebral column is a flexible, curved structure that supports the head, neck, and trunk.
It is composed of 33 vertebrae.

Vertebral Column Regions

Cervical vertebrae (7): Located in the neck.
- Atlas (C1): First cervical vertebra, supports and allows the skull to move.
- Axis (C2): Second cervical vertebra. The dens (tooth-like process) acts as an axis of rotation for the head.
- Transverse foramen: A small opening allowing passage for blood vessels.
Thoracic vertebrae (12): Located in the chest.
- They have long downward projections, called spinous processes, that provide attachment for muscles and ligaments.
Lumbar vertebrae (5): Located in the lower back.
Sacrum (5 fused vertebrae): Located at the base of the spine.
Coccyx (4 fused vertebrae): Tailbone.

Thoracic Vertebrae

Thoracic vertebrae have facets (small articular surfaces) to which ribs attach.

Ribs

Ribs: 12 pairs of ribs that help protect organs and contribute to chest expansion.
- Costal cartilage: A thin cartilage that connects the rib to the sternum.
- Head: The thickened end of a rib which articulates with a thoracic vertebra.
- Tubercle: A small projection that articulates with the transverse process of a thoracic vertebra.
- Floating ribs: The last two pairs of ribs, they are not attached to the sternum.

Sternum

The sternum is a flat bone that forms the center of the chest. It is comprised of three parts:
- Manubrium: The upper most portion of the sternum.
- Body: The main portion of the sternum.
- Xiphoid process: The small, cartilaginous section at the bottom of the sternum.

Herniated Disc

A herniated disc (also called a slipped disc) occurs when the soft, gel-like center of an intervertebral disc (cushion that sits between vertebrae) pushes through the outer layer of the disc, causing compression on a nerve.