Chapter 7 The Skeletal System: The Axial Skeleton

Axial Skeleton

Skull (Cranium, Face), Hyoid bone, Audiotry ossicles, Vertebral column, Thorax (Sternum, Ribs)

Meatus

Tubelike opening. Example: External auditory meatus of temporal bone.

Processes that form joints

Condyle, Facet, Head

Processes that form attachment points for connective tissue

Crest, Epicondyle, Line, Spinous process, Trochanter, Tubercle, Tuberosity.

Types of depressions and openings

Foramen, fossa, sulcus, meatus.

Cranial and Facial bones

Frontal bone, two parietal bones, two temporal bones, occipital bone, sphenoid bone, ethmoid bone, two nasal bones, two maxillae, two zygomatic bones, mandible, two lacrimal bones, two palatine bones, two inferior nasal conchae, the vomer.

Sulcus

Furrow along bone surface that accommodates blood vessel, nerve, or tendon. Example: Intratubercular sulcus of humerus.

Condyle

Large, round protuberance with a smooth articular surface at end of bone. Example: Lateral condyle of femur.

Line

Long, narrow ridge or border (less prominent than crest).

Fissure

Narrow slit between adjacent parts of bones through which blood vessels or nerves pass. Example: Superior orbital fissure of sphenoid bone.

Foramen

Opening through which blood vessels, nerves, or ligaments pass. Example: Optic foramen of sphenoid bone.

Processes

Projections or outgrowths on bone that form joints or attachment points for connective tissue such as ligaments and tendons.

Crest

Prominent ridge or elongated projection. Example: Iliac crest of hip bone.

Epicondyle

Typically roughened projection above condyle. Example Medial epicondyle of femur.

What structures pass through the supraorbital foramen?

1. frontal 2. supraorbital artery, supraorbital nerve (branch VI)

What structures pass through the hypoglossal canal?

1. occipital 2. hypoglossal nerve (CN XII)

Fossa

Shallow depression: Example: Coronid fossa of humerous.

Spinous process

Sharp, slender projection. Example: Spinous process of vertebra.

Give an example of long, short, flat and irregular bones.

Short bones are somewhat cube-shaped and are nearly equal in length and width. They consist of spongy bone tissue except at the surface, which has a thin layer of compact bone tissue. Examples of short bones are most carpal (wrist) bones and most tarsal (ankle) bones. Flat bones are generally thin and composed of two nearly parallel plates of compact bone tissue enclosing a layer of spongy bone tissue. Flat bones afford considerable protection and provide extensive areas for muscle attachment. Flat bones include the cranial bones, which protect the brain; the sternum (breastbone) and ribs, which protect organs in the thorax; and the scapulae (shoulder blades). Irregular bones have complex shapes and cannot be grouped into any of the previous categories. They vary in the amount of spongy and compact bone present. Such bones include the vertebrae (backbones), hip bones, certain facial bones, and the calcaneus.

Bone Surface Markings: Depressions and Openings

Sites allowing the passage of soft tissue (nerves, blood vessels, ligaments, tendons) or formation of joints.

Facet

Smooth, flat, slightly concave or convex articular surface. Example: Superior articular facet of vertebra.

On what basis is the skelteon grouped into the axial and appendicular divisions?

The axial skeleton consist of the bones that lie around the longitudinal axis of the human body, an imaginary vertical line that runs through the body's center of gravity from the head to the space between the feet: skull bones, auditory ossicles (ear bones), hyoid bone (see Figure 7.5), ribs, sternum (breastbone), and bones of the vertebral column. The appendicular skeleton consists of the bones of the upper and lower limbs (extremities or appendages), plus the bones forming the girdles that connect the limbs to the axial skeleton.

The ethmoid bone forms which other cranial structure

The ethmoid bone forms (1) part of the anterior portion of the cranial floor; (2) the medial wall of the orbits; (3) the superior portion of the nasal septum, a partition that divides the nasal cavity into right and left sides; and (4) most of the superior sidewalls of the nasal cavity. The ethmoid bone is a major superior supporting structure of the nasal cavity and forms an extensive surface area in the nasal cavity.

How do the parietal bones relate to the cranial cavity?

The internal surfaces of the parietal bones contain many protrusions and depressions that accommodate the blood vessels supplying the dura mater, the superficial connective tissue covering of the brain.

Why is the sphenoid bone called the keystone of the cranial floor?

The spehnoid bone is called the keystone of the cranial floor because it articulates with all the other cranial bones, holding them together.

Paired and Unpaired cranial and facial bones

The unpaired anterior fontanel, the largest fontanel, is located at the midline among the two parietal bones and the frontal bone, and is roughly diamond-shaped. It usually closes 18 to 24 months after birth. The unpaired posterior fontanel is located at the midline among the two parietal bones and the occipital bone. Because it is much smaller than the anterior fontanel, it generally closes about 2 months after birth. The paired anterolateral fontanels, located laterally among the frontal, parietal, temporal, and sphenoid bones, are small and irregular in shape. Normally, they close about 3 months after birth. The paired posterolateral fontanels, located laterally among the parietal, occipital, and temporal bones, are irregularly shaped. They begin to close 1 to 2 months after birth, but closure is generally not complete until 12 months.

What structures form the zygomatic arch?

The zygomataic arch is formed by the zygomatic process of the temporal bone and the temporal process of the zygomatic bone.

Head

Usually rounded articular projection supported on neck (constricted portion) of bone. Example: head of femur.

Tuberosity

Variable sized projection that has a rough, bumpy surface. Example: Greater tubercle of humerus.

Tubercle

Variable sized rounded projection. Example: Greater tubercle of humerus.

Trochanter

Variably sized rounded projections. Example: Greater tubercle of humerous.

Nasal septum

a partition that divides the nasal cavity into right and left sides.

Flat bones

are generally thin and composed of two nearly parallel plates of compact bone tissue enclosing a layer of spongy bone tissue.

Nasal Bones

are small, flatterend, rectangular-shaped bones that form the bridge of the nose.

Parietal bones

form the greater portion of the sides and roof of the cranial cavity.

Temporal bones

form the inferior lateral aspects of the cranium and part of cranial floor.

Frontal bone

forms the forehead (anterior part of cranium), the roofs of the orbits (eye sockets), and most of the anterior part of the cranial floor.

Occipital bone

forms the posterior part and most of the base of the cranium.

Long bones

greater length than width, consist of a shaft and variable number of extremiteis or epiphyses, are slightly curved for strength.

Irregular bones

have complex shapes and cannot be grouped into any of the previous categories. vary in the amount of spongy and compact bone present.

Ethmoid bone

is a delicate bone located in the anterior part part of the cranial floor medial to the orbits and is spongelike in appearance. It is anterior to the sphenoid and posterior to the nasal bones.

Sphenoid bone

lies at the middle part of the base of the skill; articulates with all other cranial bones.

Sesamoid bones

shaped like a sesame seed, develop in certain tendons where there is considerable friction, tension, and physical stress, such as the palms and soles.

Sutural bones

small bones located in sutures (joints) between certain cranial bones.

Short bones

somewhat cube-shaped and are nearly equal in length and width. consist of spongy tissue except at the surface.

Surface markings

structural features adapted for specific funtions. two main types: (1) depressions and openings, (2) processes.

What are surface markings? What are their general functions?

surface markings, structural features adapted for specific functions. projections or outgrowths that either help form joints or serve as attachment points for connective tissue.