1. 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 51 Lab 5, BIO 105

2. The Skull Cranial bones Enclose the brain in the cranial cavity Provide sites of attachment for head and neck muscles 2.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 62

3. 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 base Articulates with 1st vertebra Sites of attachment for the ligaments which attach the neck to the skull and the neck and back muscles Major markings: foramen magnum, occipital condyles, external occipital protuberance and crest BIOL 105 Lab 63

4. 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 64

5. 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 65

6. Sutural or Wormian Bones Tiny irregularly shaped bones that appear within sutures Irregular 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 bone  articulates with all other facial bones except mandible Major markings: palantine process, alveoli, infraorbital fissure, maxillary sinus BIOL 105 Lab 66

7. 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 67

8. 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 68

9. 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 69

10. 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 610

11. 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 611

12. 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 612

13. Intervertebral Discs Cushionlike pad composed of two parts 1.Nucleus pulposus Inner gelatinous nucleus that gives disc elasticity and compressibility 2.Anulus fibrosus Surrounds nucleus pulposus; composed of collagen and fibrocartilage BIOL 105 Lab 613

14. 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 614

15. 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 615

16. Cervical Vertebrae C 1 to C 7 : smallest, lightest vertebrae C 3 to C 7 have an oval body, short spinous processes which are often bifurcated, and large, triangular shaped vertebral foramen C 1 (atlas) and C 2 (axis) have unique features BIOL 105 Lab 616

17. Atlas (C 1 )--- 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 (C 2 )---Dens (a pivot area for the rotation of the atlas) projects superiorly into the anterior arch of the atlas; “No” bone BIOL 105 Lab 617

18. Thoracic Vertebrae--T 1 to T 12. ** 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 618

19. Lumbar Vertebrae: L 1 to L 5, 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 619

20. Sacrum – 5 fused vertebrae (S 1 –S 5 ) which make the posterior wall of pelvis – Articulates with L 5 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 620

21. 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 621

22. 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 622

23. 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 623

24. LABWORK 1.Identify and describe the bones and bone markings listed in the handout. BIOL 105 Lab 624