Axial Skeleton•Consists of 80 bones•Forms longitudinal axis of body•Three major regions– Skull– Vertebral column– Thoracic cage

•Supports head, neck and trunk•Protects brain, spinal cord, and thoracic organs

BIOL 105 Lab 5 1

Lab 5, BIO 105

The SkullCranial bones• Enclose the brain in the cranial cavity• Provide sites of attachment for head and neck

muscles2.Facial bones• Framework of face and the sense organs• Openings for air and food passage• Sites of attachment for teeth and muscles of

facial expression

BIOL 105 Lab 6 2

Figure 7.8

Temporal Bones•Major markings: zygomatic process, mandibular fossa external auditory (or acoustic) meatus, mastoid process, mastoid sinus, styloid process

Occipital Bone Most of skull’s posterior wall and baseArticulates with 1st vertebraSites of attachment for the ligaments which attach the neck to the skull and the neck and back musclesMajor markings: foramen magnum, occipital condyles, external occipital protuberance and crest

BIOL 105 Lab 6 3

Zygomatic Bones:Cheekbones and lateral and inferior margins of

orbits

Ethmoid Bone- • Deepest skull bone; lies between the sphenoid and

nasal bones• Forms most of the bony area between the nasal

cavity and the orbits• Contributes to medial wall of orbits

BIOL 105 Lab 6 4

Sphenoid Bone--Butterfly or bat-shaped bone that spreads across the middle of the skull•Articulates with all other cranial bones-holds other bones of the skull together•Made up of the following areas:– Body --Lesser wings– Greater wings --Pterygoid processes

BIOL 105 Lab 6 5

Sutural or Wormian BonesTiny irregularly shaped bones that appear within

suturesIrregular shape due to different ossification rates of the

flat, skull bones

Maxilla Bones• Medially fused to form upper jaw and central portion

of facial bones• Keystone bonearticulates with all other facial

bones except mandible• Major markings: palantine process, alveoli,

infraorbital fissure, maxillary sinus

BIOL 105 Lab 6 6

Sinuses: Mucosa-lined, air-filled spaces found in frontal, sphenoid, ethmoid, and maxillary bones

Air enters from the nasal cavity and mucus drains into the nasal cavity from the sinuses

Lighten the skull , Enhance resonance of voice

• Nasal bones —thin, medially fused bones that form bridge of nose

• Lacrimal bones —contribute to the medial walls of orbits and has a deep groove called the lacrimal fossa that houses the lacrimal sac

• Vomer--plow shaped bone that forms part of nasal septum

BIOL 105 Lab 6 7

Mandible or lower jaw•Largest, strongest bone of face•Temporomandibular joint: only freely movable joint in skull•Major markings: coronoid process, mandibular condyle (also called condyloid process), body, mental foramina (nerves for tooth sensation travel through these), ramus, and alveoli

BIOL 105 Lab 6 8

Nasal Cavity•Constructed of bone and hyaline cartilage•Roof formed by ethmoid•Lateral walls formed by part of ethmoid and palantine bones, and inferior nasal conchae•Floor formed by palantine process of the maxilla and palantine bone

Orbits•Bony cavities in which eyes are enclosed (and cushioned by adipose tissue) and also contains the lacrimal glands•Sites of attachment for eye muscles•Formed by parts of seven bones: frontal, sphenoid, zygomatic, maxilla, palantine, lacrimal and ethmoid

BIOL 105 Lab 6 9

Hyoid Bone: Not actually bone of the skull; lies inferior to the mandible in the anterior neck•Only bone in the body that does not articulate directly with another bone; •Is a movable base for the tongue, attachment point for the muscles of swallowing and speech which raise and lower the larynx while swallowing and talking

BIOL 105 Lab 6 10

Vertebral Column•Flexible, curved structure containing 26 irregular bones (vertebrae)•Transmits weight of trunk to lower limbs•Surrounds and protects spinal cord•Vertebrae get larger (moving from cervical to lumbar) because they have to support more weight– Cervical vertebrae (7)—vertebrae of the neck– Thoracic vertebrae (12)—vertebrae of thoracic

cavity– Lumbar vertebrae (5)—vertebra of lower back– Sacrum—bone inferior to lumbar vertebrae and

articulates with hip bones– Coccyx—end of vertebral column

BIOL 105 Lab 6 11

Curves of the Vertebral Column•Increase resilience and flexibility of spine•Allow us to stay in upright position•Shock absorber—prevents lower extremity shock from easily reaching brain– Cervical and lumbar areas are concave curves

(posteriorly) • Thoracic and sacral areas are convex curves

(posteriorly)

BIOL 105 Lab 6 12

Intervertebral Discs•Cushionlike pad composed of two parts

1. Nucleus pulposus• Inner gelatinous nucleus that gives disc

elasticity and compressibility2. Anulus fibrosus• Surrounds nucleus pulposus; composed of

collagen and fibrocartilage

BIOL 105 Lab 6 13

General Structure of Vertebrae•Body or centrum: anterior weight-bearing region•Vertebral arch: posterior: composed of pedicles and laminae that, along with centrum, enclose vertebral foramen•Vertebral foramina: compose vertebral canal through which spinal cord runs•Pedicles (little feet):project posteriorly from vertebral body, form sides of arch•Laminae: flat plates, complete arch posteriorly

BIOL 105 Lab 6 14

• Spinous process —projects posteriorly• Transverse processes —project laterally• Both of these are attachment sites for muscles

and ligaments that move and stabilize vertebrae• Superior articular processes —protrude superiorly• Inferior articular processes —protrude inferiorly• Intervertebral foramina– Lateral openings formed by notched areas on

superior and inferior borders of adjacent vertebrae for spinal nerves

BIOL 105 Lab 6 15

Cervical Vertebrae•C1 to C7: smallest, lightest vertebrae•C3 to C7 have an oval body, short spinous processes which are often bifurcated, and large, triangular shaped vertebral foramen•C1 (atlas) and C2 (axis) have unique features

BIOL 105 Lab 6 16

Atlas (C1)---No body or spinous process (doesn’t need a body because it supports the weight of the head vs the entire body)• “Yes” vertebra• Superior surfaces of lateral masses articulate with

the occipital condyles• c1 and c2 are differ from the rest of the

vertebrae in that there is no intervertebral disc between them

Axis (C2)---Dens (a pivot area for the rotation of the atlas) projects superiorly into the anterior arch of the atlas; “No” bone

BIOL 105 Lab 6 17

• Thoracic Vertebrae--T1 to T12. **All articulate with ribs

• **Location of articular facets prevent flexion and extension but allow rotation of this area of spine; have facets for articulation with head of ribs

• **Have long spinous process, a heart shaped body, circular vertebral foramen

BIOL 105 Lab 6 18

Lumbar Vertebrae: L1 to L5, located in the small of the back

• Flat hatchet-shaped spinous processes • Orientation of articular facets locks lumbar

vertebrae together to prevent rotation and provide added stability; Body is thick and massive to support the weight of the body

BIOL 105 Lab 6 19

Sacrum– 5 fused vertebrae (S1–S5) which make the posterior

wall of pelvis– Articulates with L5 superiorly, and with auricular

surfaces of the hip bones laterally – Markings: Sacral foramina, sacral canal

Coccyx– Tailbone– 3–5 fused vertebrae– Articulates superiorly with sacrum

BIOL 105 Lab 6 20

Thoracic or Rib Cage•Composed of thoracic vertebrae, sternum, ribs and costal cartilage (cartilage which attach ribs to sternum)•Functions– Forms protective cage around heart, lungs, and great

blood vessels– Supports shoulder girdle and upper limbs– Provides attachment sites for many neck, back, chest

and shoulder muscles – Intercostal muscles used during breathing lift and

lower the thorax– some flexibility in rib cage due to cartilage so we can

breathe

BIOL 105 Lab 6 21

Ribs and Their Attachments•12 pairs make up the sides of the thoracic cavity•All attach posteriorly to body and transverse processes of the thoracic vertebrae•Pairs 1 through 7– True ribs because attach directly to sternum by costal

cartilages•Pairs 8 through12 : False ribs—– Pairs 8–10; attach indirectly to sternum by joining

costal cartilage of rib above – Pairs 11–12--floating ribs; no attachment to sternum

BIOL 105 Lab 6 22

Developmental Aspects: Fetal Skull•Infant skull has more bones than adult skull because skull bones are unfused and are connected by fontanelles– Fontanelles: Unossified remnants of fibrous

membranes between fetal skull bones

BIOL 105 Lab 6 23

LABWORK1.Identify and describe the bones and bone markings listed in the handout.

BIOL 105 Lab 6 24