The Skeletal System

THE SKELETAL SYSTEM
Introduction to Osteology
Functions of the Skeletal System
A. Support
B. Protection
C. Movement
 Contraction of the muscles attached to the bones (skeletal muscles) causes movements at the joints
between bones
 Tendons- attach muscles to bones ( Muscles-to- Blood Production
Bones)(Mnemonic: TM; Tendons-Muscles to
Bones)  Prenatal: Yolk sac, Liver/Spleen, Bone
 Ligaments- holds bone together (Bone-to-Bone) Marrow
D. Storage of minerals Ca2+ and PO4-  Postnatal (1-2 years old): Tibia/Femur
In the form of Calcium Phosphate [Ca3 (PO4)2]  >20 Years: Vertebra, Sternum, Rib
E. Blood Cell Production
Erythropoiesis – RBC production
Leukopoiesis – WBC/Leukocyte production
Thrombopoiesis – Platelet/thrombocyte production
 Organization of Skeletal System
A. Axial Skeleton (80 Bones)
Skull – 29
Vertebral column – 26
Ribcage – 25
 Sternum – 1
 Ribs – 24
B. Appendicular Skeleton (126 Bones)
Pectoral Girdle – 4
Upper Limb – 60
Pelvic Girdle – 2
Lower Limbs 60

The Skeletal System by Region

I. Skull – 8 cranial bones, 14 facial bones
 Joints of the Skull
 SUTURES
 Non-movable joints between bones
 Major sutures of the skull:
o Frontal Suture – non-visible on adult skull.
Where 2 frontal bones fuse together
o Sagittal Suture- where 2 parietal bone fuse
together
o Coronal Suture- where parietal bones fuse
with frontal bone
o Lambdoidal Suture- where parietal bone fuse
with occipital bone




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,  FONTANELS – “soft spots”
 Uncalcified angles of parietal bones- Soft spots of fetal skull
 Includes: Anterior (Frontal), Posterior (Occipital), Sphenoidal,
and Mastoidal Fontanel
 AIR SINUSES – “cavities” of the skull bone
Paranasal Air Sinuses – communicates with nasal cavities. Lined
by CILIATED MUCOUS MEMBRANE that functions to warm and
humidify the inhaled air
o Frontal
o Ethmoidal
o Sphenoidal
o Maxillary
Mastoid Air Sinuses – located within the mastoid process of each temporal bone. Lined by Mucous
Membranes and connects with the EUSTACHIAN CANAL (Auditory Tubes) which open into the
throat.
They allow equalizing of the air pressure across the tympanic membrane (eardrum)
EAR OSSICLES (3 smallest bones)
 Malleus – “mallet”
 Incus – “anvil”
 Stapes – “stirrup”
Disease Correlation!!
1. Sinusitis, Sinus Headaches – buildup of mucus and fluid or infection in
the sinus cavities
2. Otitis Media – Earache: infection/inflammation in the middle ear.

 Frontal Bone (1)
Superciliary arches of frontal bone – ridges that form base of
the eyebrows
Supraorbital notch (foramen) of frontal bone – where nerves
and blood vessels pass just above the eye sockets
Zygomatic Process of frontal bone – portion of the frontal bone
that joins the Zygomatic bone
Maxillary process of frontal bone – portion of frontal bone that
joins the Maxilla
Frontal (paranasal) sinuses – air inhaled through the nose, swirls
up into these sinuses located in the frontal bone
Frontal suture – location where the right and left frontal bones
join together
 Visible only on Fetal skull
 Zygomatic “cheek” Bone (2)
 Temporal Process of Zygomatic Bone – portion of Zygomatic
bone that joins the Temporal bone
 Maxillary Process of Zygomatic Bone – Portion of Zygomatic
bone that joins the Maxilla
 Frontal Process of Zygomatic Bone – portion of Zygomatic Bone
that joins Frontal Bone




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,  Nasal Bones (2)
thin bones that form the bridge of the nose
 Lacrimal Bones (2)
Located at the medial corners of the orbits
Nasolacrimal Canal – location of nasolacrimal duct which
conducts excess tears down to the nasal cavity (which explains
why crying leads to runny nose)
 Mandible “lower jaw” Bone (1)
Lower jaw, only movable bone of the skull
Body of Mandible – forms the chin
Mental foramen of the Mandible – openings for
nerves and blood vessels
Alveolar Process (tooth sockets) – Incisors, Canines,
Premolars, Molars
Ramus of Mandible – the angles “sides” of the
mandible
Condyloid process of Mandible – the thick, rounded
portion of the Mandible that attaches with the
Mandibular fossa of the Temporal Bone forming the
TEMPORO-MANDIBULAR JOINT (TMJ)
Coronoid process of the Mandible – the thin, pointed,
anterior projection for the attachment of muscles
Mandibular Foramen – openings for nerves and blood
vessels located on the “back side” internal surface of the
Mandible
 Maxilla “upper jaw” Bone (1)
 Infraorbital foramen of the Maxilla – location where
nerves and blood vessels pass just below the orbits
“eye sockets”
 Alveolar Processes (tooth sockets) – Incisors, Canines,
Premolars, Molars
 Zygomatic Process of the Maxilla – portion where
maxilla joins Zygomatic bone
 Frontal process of the Maxilla – portion where Maxilla
joins Frontal bone
 Palatine process of the Maxilla – portion of the Maxilla
that makes up the hard palate ( along with palatine
bone) anteriorly
o Makes up roof of the mouth
 Incisive foramen of the Maxilla – small hole located just
behind the front incisor teeth for the passage of nerves and
blood vessels
 Maxillary Sinus – air inhaled through the nose, swirls
into these sinuses located within the Maxilla
o Visible on frontal X-ray of the skull
 Palatine Bone (2)
Forms posterior portion of hard palate (roof of the mouth)




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