Lab 3 Organization of the Skeletal System

Organization of the Skeletal System ● ● ● ● List the components of the axial skeleton and those of the appendicular skeleton. Describe the gross anatomy of a long bone. List five shapes of bones and give an example of each type. Describe the bone markings visible on the skeleton. Bones may be grouped and classified according to shape. Examine the articulated skeleton and determine how many of each type of bone is present. 6 Long Bones 15 Short bones 3 Flat Bones 4 Irregular Bones 1 Sesamoid Bones 4 Sutural Bones Using the table for reference, locate on the skeleton: A foramen in the skull. Describe this structure. Holes inside the skull. A fossa on the distal end of the humerus. How is the fossa different from a foramen? The fossa is a dip at the end o f the humerus and the foramen is holes that are inside the skull. Identify the head on the femur. Which other bones have a head? The humerus A condyle on two different bones. Describe this structure. Rounded structures at the end of bones like the femur and the humerus. A tuberosity on the proximal end of the humerus. What is the texture of this structure? The texture is rough. Matching: Match each bone with the correct division and part of the skeleton: Each question may have more than one answer, and each choice may be used more than once. __C_______ 1. Scapula _____B____ 2. Patella _______A__ 3. Hyoid ____D_____ 4. Radius _____D___ 5. Metacarpal ___A____ 6. Vertebra ____C___ 7. Clavicle _____A__ 8. Rib ____F___ 9. Femur ____A___10. Sternum A. axial division B. appendicular division C. pectoral girdle D. upper limb E. Pelvic girdle F. Lower limb Cranial Bones The skull serves a wide variety of functions, cradles the brain, houses many sensory organs for vision, hearing, balance and taste. The skull is perforated with many holes called foramina where nerves and blood vessels pass to and from the brain and other structures of the head. Facial and cranial bones make sockets, called orbits, for the eyes. The joints of the skull are designed for strength instead of movement. The cranium has eight bones; one frontal bone, two parietal bones, two temporal bones, one occipital bone, one sphenoid and one ethmoid. 1. Locate the frontal bone on the skull. The floor of the cranium has three depressions called fossae. The anterior cranial fossa is mainly the depression that forms the base of the frontal bone. Small portions of the ethmoid and sphenoid also contribute to the floor of this area. The middle cranial fossa is a depressed area extending over the sphenoid and the temporal and occipital bones. The posterior cranial fossa is found in the occipital bone. The frontal bone forms the roof walls and floor of the anterior cranium. The frontal bone forms the upper portion of the eye orbit. Superior to the orbit is the supra-orbital foramen, which on some skulls is not a complete hole but as a small notch, the supra-orbital notch. In the anterior and medial regions of the orbit, the frontal bone forms the lacrimal fossa, an indentation for the lacrimal gland. Identify the anterior cranial fossa, supra-orbital foramen, supraorbital notch (foramen), lacrimal fossa. 2. Locate the parietal bones on the skull. Two parietal bones form the posterior crest of the skull and are joined by the sagittal suture. The bones are smooth and have few surface features. The low ridges of the superior and inferior temporal line are superior to the squamous suture, where muscles for chewing attach. Examine the lateral surface of the parietal bone and locate the superior and inferior temporal lines. Identify the sagittal suture, lambdoid suture, squamous suture, and coronal suture. 3. Identify the occipital bone on the skull. The occipital bone forms the posterior floor and wall of the skull. The large hole, foramen magnum is where the spinal cord enters the skull and joins the brain. Along the lateral margins of the foramen magnum are flattened occipital condyles that articulate with the first vertebra of the spine. Passing superior to each occipital condyle is the hypoglossal canal, a passageway for the hypoglossal nerve controls muscles of the tongue and throat. The external surface has marks that show where muscles and ligaments attach. The external occipital protuberance and superior and inferior nuchal lines are surface marks indicating where muscles of the neck attach to the skull. Locate the foramen magnum, the occipital condyles, the hypoglossal canal. Locate the external occipital crest, external occipital protuberance, and superior and inferior nuchal lines. 4. Identify the temporal bones on the skull The two temporal bones constitute the inferior lateral walls of the skull and part of the floor of the middle cranial fossa. One of the most distinctive features of the temporal bone is the articulation with the zygomatic bone of the face by the zygomatic arch. The arch is formed from two bones: the zygomatic process of the temporal bone and the temporal process of the zygomatic bone. The mandibular fossa is a shallow depression where the mandible bone articulates with the temporal bone. The hole inferior to the flat squamous surface of the temporal bone is the external acoustic meatus, which conducts sound waves towards the eardrum. Directly posterior is the mastoid process where a muscle tendon that moves the head attaches. The long needle like styloid process is located anteromedial to the mastoid process. From the internal perspective you can see a large bony ridge of the temporal bone which is the petrous part (houses organs for hearing and equilibrium). The internal acoustic meatus is on the posteromedial surfaces of the petrous part. Locate the squamous and petrous parts, mastoid processes and zygomatic processes. Can you feel the mastoid process on your own skull? Find the mandibular fossa. Identify the styloid process. Identify the major passageways of the temporal bone. External and internal auditory meatuses 5. Examine the Sphenoid The sphenoid is the base of the cranium and each cranial bone articulates with it. The easiest view of this bone to work with is the superior surface exposed on the floor of the skull. The superior surface is made up of two lesser wings and two greater wings on either side of the medial line. The center of the sphenoid is the U-shaped sella turcica. The depression in the sella turcica is the hypophyseal fossa, which contains the pituitary gland of the brain. Identify the lesser wings, greater wings and sella turcica. 6. Identify the Ethmoid on the skull The ethmoid is a rectangular bone that is anterior to the sphenoid. On the superior surface is a vertical crest of bone called the crista galli where membranes that protect and support the brain attach. At the base of the crista galli is a screen like cribriform plate punctured by many small olfactory foramina that are passageways for branches of the olfactory nerve. The inferior ethmoid has a thin sheet of vertical bone, the perpendicular plate, which contributes to the septum of the nasal cavity. Extending inferiorly to the nasal cavity from the lateral masses are the superior and middle nasal conchae. Observe on the floor of the skull the crista gilla, cribriform plate Examine the perpendicular plate in the nasal cavity Facial Bones The face is constructed of 14 bones: two nasal, two maxillary, two lacrimal, two zygomatic, two palatine, two inferior nasal conchea, the vomer, and the mandible. Locate the Maxillae on the skull. You can feel your hard palate by placing your tongue on the roof of your mouth. Examine the palatine bones. With which part of the maxillary bones do they articulate? The palatine bones articulate the mouth of the maxillary bones. Identify the zygomatic bones. Which part of the temporal bone contributes to the zygomatic arch? The squamous part. Examine the lacrimal bone and identify the lacrimal fossa. Locate the nasal bones. Which bone occurs between a nasal bone and a lacrimal bone? The maxilla Locate the vomer both in the inferior view of the skull and in the nasal cavity. Examine the mandible. Identify the body, angle and ramus. Identify the coronoid process, mandibular notch. Vertebral Column The vertebral column or spine is a flexible change of 26 bones, 24 vertebrae, the sacrum, and to coccyx. The column articulates at the superior end with the skull, the inferior portion with the pelvic girdle, and the ribs laterally. Vertebrae Anatomy The anatomical features of the typical vertebra include a large, anterior, disc-shaped vertebral od (the centrum) and posterior elongated spinous process. Lateral on each side of the spinous process is a transverse process. The lamina is a flat plate of bone between the transverse and spinous processes that forms the curved vertebral arch. The pedicle is a strut of bone extending posteriorly from the vertebral body to transverse process. The pedicle and lamina on each side form the wall of the large posterior vertebral foramen, which contributes to the spinal cavity where the spinal cord is housed. Cervical vertebrae The seven cervical vertebrae in the neck are recognizable by the presence of a transverse foramen on each transverse process. The tip of the spinous process is bifid (branched) in the vertebrae C2 to C6. The first cervical vertebra, C1 is called the atlas and is the only vertebrae to articulate with the skull. The last cervical vertebrae is called the vertebra prominens. Thoracic Vertebrae The twelve thoracic vertebrae articulate with the 12 pairs of ribs, are larger than the cervical vertebrae and increase in size as they reach the lumbar region. Most ribs attach to the thoracic vertebrae at two sites; on a transverse costal facet at the tip of the transverse process and on a costal facet located on the posterior of the vertebral body. Lumbar vertebrae The five lumbar vertebrae are large and heavy in order to support the weight of the head, neck and trunk. Characteristics include wider body, a blunt and horizontal spinous process, and shorter transverse processes. Sacral and Coccygeal Vertebrae Sacrum is a single bony element composed of five fused sacral vertebrae. It articulates with the ilium of the pelvic girdle to form the posterior wall of the pelvis. Fusion of the sacral bones before birth consolidates the vertebral canal into the sacral canal. The coccyx articulates with the fifth sacral vertebrae at the coccygeal cornu. What are the five major regions of the vertebral column and the number of vertebrae in each region? Cervical, thoracic, lumbar, sacral, coccygeal What are three features found on all vertebrae? The centrum, posterior spinous process, and the transverse process. Describe the anatomy of a typical vertebrae. Locate each feature on a disarticulated vertebrae. Identify the unique features of the Atlas. Describe how lumbar vertebrae are different from a thoracic vertebrae. Thoracic Cage The 12 pairs of ribs articulate with the thoracic vertebrae posteriorly and the sternum anteriorly to enclose the thoracic organs in a protective cage. Sternum is the flat bone located anterior to the thoracic region of the vertebral column. It is composed of three bony elements. The manubrium. A middle sternal body and an inferior xiphoid process. Ribs are also called costae and are classified according to how they articulate with the sternum. The first sevel true ribs because their cartilage attaches directly to the sternum. Ribs pairs 8-12 are called false ribs because costal cartilage does not connect directly to the sternum but to costal cartilage of rib 7. Pairs 11 and 12 are called floating ribs because they do not articulate with the sternum. Each rib has a head (capitulum) with two articular facets. The tubercle of the rib articulates with the transverse costal facet of the rib’s vertebrae. Between the head and the tubercle is the neck. Identify the Sternum and located manubrium Describe the anatomy of a typical rib.