Skeletal System (The Bones)

Skull

Irregular and flat bones connected by sutures; encloses cavities (cranial, orbital, nasal, buccal)

Cranial and Facial bones

Divisions of the skull

Parietal, Temporal

Paired cranial bones

Parietal

Forms the roof and sides of the cranium.

Temporal

Forms the side and lower part of the skull; squamous, petrous, tympanic, and mastoid.

Frontal, Sphenoid, Ethmoid, Occipital

Unpaired cranial bones

Frontal

Anterior wall and 1/3 of the roof cranial cavity. Floor of anterior cranial fossa and roof of orbit.

Sphenoid

Resembles a bat with its wings extended which is centrally located by the silas body and is better viewed internally.

Greater wings

Middle cranial fossa of sphenoid

Lesser wings

Anterior cranial fossa of sphenoid

Ethmoid

Inserted into the notch between orbital plates of frontal bone.

Occipital

Forms the lower and back portion of cranium and is pierced by foramen magnum.

Nasal, Lacrimal, Zygomatic, Maxilla, Palatine

Paired facial bones

Nasal

Quadrangular bones articulation with each other and with frontal process of maxilla to form the bridge of the nose.

Lacrimal

Anterior part of the medial wall of the orbit.

Zygomatic

Prominence of cheek, inferolateral margin of orbit; orbital, temporal, frontal, infraorbital, and malar.

Maxilla

Forms the upper jaw, boundaries for orbital, nasal, and buccal cavities.

Palatine

L-shaped bone, part of the hard plate, wall of nasal cavity, and floor of orbit.

Mandible, Vomer

Unpaired facial bones

Mandible

Skeleton of the lower face and the only movable bone of the skull.

Vomer

Thin bone articulating with sphenoid, maxilla, palatine, and ethmoid and forms inferior half of nasal septum.

Inferior Nasal Concha

Pair of scroll-like lamina hanging at the lateral wall of the nasal cavity.

Nasal and Frontal bone

Meet at the frontonasal suture, forming the bridge of the nose and the upper part of the face.

Perpendicular plate and Vomer

Bony components that form the nasal septum, which divides the nasal cavity.

Palatine process and Horizontal plate

Work together to form the hard palate, which separates the oral cavity from the nasal cavity.

Ear Ossicles

Petrous part of temporal bone, the malleus, incus, and stapes.

Malleus

This is the largest and most lateral ossicle. It is attached to the eardrum (tympanic membrane) and transmits the eardrum's oscillations to the incus.

Incus

Located in the middle; receives vibrations from the malleus and passes them along to the stapes.

Stapes

The smallest and most medial ossicle; has a base that fits into the oval window of the inner ear. It transfers the mechanical energy of sound to the fluid in the inner ear, which then transmits the sound to the brain.

Hyoid bone

U-shaped bone lying in front of the neck and to which the base of the tongue is attached. Body, greater horn and lesser horn.

Greater horn

The cornua of the hyoid that extend backward.

Lesser horn

The cornua of the hyoid that project superiorly from the body where the greater horns attach.

Ribs

Articulate posteriorly with the thoracic vertebra; attach to the sternum through its costal cartilage.

Typical ribs

Ribs 3-9, common structure with a head, neck, and body.

Atypical ribs

Ribs 1, 2, 10, 11, 12, exhibit variations in their structure and articulation.

True ribs (Vertebrosternal)

Protect the vital organs of the thoracic cavity, particularly the heart and lungs, and to assist in breathing.

False ribs (Asternal)

Protect internal organs in the abdomen, such as the liver, kidneys, and stomach.

Floating ribs (Vertebral)

Have no interchondral joints or costochondral joints, and don't connect to the front of the rib cage.

Manubrium, body/gladiolus, xiphoid process

Landmarks of sternum

Thoracic/Rib cage

Composed of thoracic vertebra, sternum, and ribs.

Vertebral column

The bony structure of the skeleton that provides central support for the body, protects the spinal cord, and facilitates movement.

Intervertebral disc

A flexible, shock-absorbing cushion between vertebrae that provides spinal flexibility and stability.

Primary Curvature

Present at birth, concaves anteriorly; curves backward

Thoracic, Sacral

Primary curvature of vertebral column

Secondary Curvature

Develop after birth, concaves posteriorly; curves forward

Cervical, Lumbar

Secondary curvature of vertebral column.

Cervical Vertebra

Occupies the neck region, short and bifid spinous process, and transverse process is pierced with transverse foramen.

C1- Atlas

The topmost vertebra

C2- Axis

The vertebra that forms the joint connecting the skull and spine.

Atlantoaxial Joint

Links the first cervical vertebra, to the second cervical vertebra.

7th cervical vertebra

Spinous process resembles the thoracic, not bifid and ends in a tubercle, and lies horizontally.

Thoracic Vertebra

Lies in the posterior wall of the thorax, presents articular facet, and articulates with ribs to form the thoracic cage.

Lumbar Vertebra

Lies in the posterior abdominal wall

Sacrum

Forms posterior wall of pelvic cavity, inserted like a wedge between the os coxae.

Coccyx

Triangular bone at the bottom of the groove between the buttocks; attachment of muscles of the pelvic floor.