The Skeleton

Axial skeleton

Bones involved with protecting, supporting, & carrying other body parts

Axial skeleton Examples

skull, vertebral column, rib cage

Appendicular skeleton

Bones involved in locomotion

Appendicular skeleton

Humerus, Pectoral Girdle, Femur, Pelvic Girdle

The Skull

Most complex bony structure in the body; most bones are flat bones

Skull Composed of 22 bones

Cranial Bones (8 bones) and Facial bones (14 bones)

Sutures

Interlocking joints of the skull with saw-toothed or serrated appearances (except mandible)

The Cranium

Encloses the brain and furnishes the attachment sites for the head & neck muscles

The Cranium: Single Bones

Frontal, occipital, ethmoid, & sphenoid bone

The Cranium: Paired Bones

Temporal & parietal bones

Cranial Vault

Round portion that makes up the superior, lateral and posterior portions of the skull

Cranial Base

Makes up the floor or interior portion of the skull

Foramen Magnus

Where spinal cord exits the cranium

The Cranial Fossae

Contoured depressions  that make up the floor of the cranium

Anterior Cranial Fossa

Supports the frontal lobe

Anterior Cranial Fossa Examples

Frontal bone, ethmoid bone and sphenoid bone

Middle Cranial Fossa

Supports the temporal lobe and the pituitary gland

Middle Cranial Fossa Examples

Sphenoid bone, and temporal bone

Posterior Cranial Fossa

Supports the cerebellum and part of the brainstem

Posterior Cranial Fossa Examples

Temporal bone and occipital bone

The Cranial Sutures

Immovable joints that form boundaries between the cranial bones

Coronal Suture

Articulation between frontal and parietal bones

Lambdoid Suture

Articulation between parietal and occipital bones

Sagittal Suture

Articulates between the paired parietal bones

Squamous Suture

Articulates between the temporal and parietal bone (on a side)

Facial Skeleton: Single Bones

Mandible & Vomer

Facial Skeleton: Paired Bones

Nasal bones, lacrimal bones, zygomatic bone, palantine bones, maxilla, & inferior nasal concha

Facial Skeleton Function

Forms cavities for the special sense organ and to help anchor face muscles

Cranial Cavity

Largest cavity that surrounds the brain

Orbital Cavities

Contains eyeballs and lacrimal glands

Nasal Cavity

Contains passage way for air and smell (considered the first part of the respiratory tract)

Nasal Cavity Bones

Divided by the septum (formed by vomer & ethmoid bone)

Oral Cavity

Contains teeth, tongue, a passage for both food and air, and most of the salivary glands

Nasal and Paranasal Sinuses

Air filled chambers within the bones of the skull

As air moves in from nasal cavity

Mucus drains out to nasal cavity

Nasal and Paranasal Sinuses Function

Helps to warm the air, listen the skull, and enhance resonance of the voice

Hyoid Bone

Has no direct articulations with any other bones and its position is maintained by a combination of ligaments and muscles

Hyoid Bone Function

Two pairs of projections called lesser and greater horns that help attach it to muscles involved in swallowing and speech

Cervical Vertebrae

7 (Concave Curve)

Thoracic Vertebrae

12 (Convex Curve)

Lumbar Vertebrae

5 (Concave Curve)

Sacral Vertebrae

5; Vertebrae are fused and called the sacrum(Convex Curve)

Coccygeal Vertebrae

4; Vertebrae are fused and called coccyx

Why the spine curves

Provides flexibility and increased resilience (e.g. acts like a spring)

Vertebrae: Body

Weight-bearing portion

Vertebrae: Vertebral Foramen

Space between the body & arch

Vertebrae: Vertebral Arch

Composite structure

Vertebrae: Spinal Process

Single; Extends Anteriorly

Vertebrae: Articular Process

Two pairs; Extends Superiorly and Inferiorly

Vertebrae: Transverse Process

One Pair: Extends Laterally

Intervertebral Discs

Resides between the vertebrae to provide cushioning

2 Parts of The Intervertebral Discs

Anulus Fibrosis and Nucleus Pulposus

Characteristics of Cervical Vertebrae

Triangular

Characteristics of Thoracic Vertebrae

Circular

Characteristics of Lumbar Vertebrae

Flattened Triangular

Special feature of The Thoracic Vertebrae

Transverse processes contain facets for the rib (called the costal facet)

Sacrum

Formed from 5 fused vertebrae; Superior Articular process connects to the hip

Sacrum Function

Possesses foramen for blood vessels & spinal nerves to pass through

Coccyx

Formed by 4 fused vertebrae; Occurs around age 25

Coccyx Function

Is the attachment site for several ligaments

Thoracic Cage: Sternum

Stabilizes the thoracic cage and helps protect the heart, vena cava, and thymus

The 3 Parts of the Sternum

Manubrium, Body, and Xiphoid Process

Manubrium

Articulates with clavicle and ribs

Body

Articulates with ribs

Xiphoid Process

Attachment point for the abdominal muscles; Initially composed of hyaline cartilage, ossifies by age 40

Thoracic Cage: Ribs

All attach posteriorly to the thoracic vertebrae

True Ribs

1-7; Attaches directly to Sternum

False Ribs

8-12; But 8-10 only Attaches to Rib 7

Floating Ribs

11 and 12

Rib Structure

Bow-shaped flat bone

Rib Structure: Shaft

Comprises the bulk of the rib

Rib Structure: Head

Articulates with the thoracic vertebrae at the costal groove, and is divided into the superior and inferior articular facets

Rib Structure: Neck

Area between the head and the tubercle

Rib Structure: Angle

The point where the rib curves toward the sternum

Rib Structure: Tubercle

Articulates with the transverse process of the vertebrae

The Pectoral Girdle

Is the clavicle and scapula

The Pectoral Girdle: Clavicle

Acts as a brace to hold the arms & scapula away from the body

Clavicle: Sternal End

Articulates with the manubrium of the sternum

Clavicle: Acromial End

Articulates with the acromion of the scapula

The Pectoral Girdle: Scapula

Attached to the axial skeleton via articulation with the clavicle and various muscles

Scapula Dorsal Process

Spine; which ends at the acromion

Acromion

Articulates with the clavicle

Glenoid Cavity

Articulates with the humerus

Ventral Surface of The Scapula

Subscapular Fossa

Dorsal Surface of The Scapula

Supraspinous Fossa and Intraspinous Fossa

The Humerus

Articulates with scapula to form the shoulder and articulates with the ulna and radius to form the elbow

Humerus: Head

Proximal end that articulates with the glenoid cavity

Humerus: Tubercules

Greater and Lesser attachment sites for the rotator cuff

Humerus: Deltoid Tuberosity

Attachment for the deltoid muscle

Humerus: Capitulum

Articulates with the head of the radius

Humerus: Trochlea

Articulates with the trochlear notch of the ulna

Humerus: Epicondyles

Attachment sites for muscles

The Forearm

Includes the ulna and radius