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Week 04 Lab Skeletal Tissue and Bone Structure LEARNING OUTCOMES: ❍ Identify the three types of cartilage tissue under the microscope, and relate their microscopic structure to their respective functions. ❍ ❍ ❍ ❍ Become familiar with the basic shapes and markings of the bones of the skeleton. Identify the major gross anatomical features of a long bone. Identify bone tissue under the microscope and on anatomical models and describe its structure. Contrast the roles of the organic and inorganic components of bone matrix. ACTIVITY 1: Cartilage In this activity, you will observe prepared microscope slides of hyaline cartilage, elastic cartilage, and fibrocartilage. Locations Functions hyaline cartilage Forms most of the developing fetal skeleton; found on the ends of long bones (articular cartilages), between the ribs and sternum (costal cartilages), and making up several respiratory structures (nose and parts of larynx and trachea). Support and reinforcement; cushions and can resist stress. In fetuses, it forms the framework for what will become the bony skeleton. elastic cartilage Found in external ear and epiglottis. Maintains the shape of a structure while providing more flexible than hyaline cartilage; tolerates bending better fibrocartilage Found in intervertebral discs, in the knee joint (meniscus), in the joint where the two pelvic joints meet (pubic symphysis). Provides great tensile strength; can withstand heavy compression. In Lab: 1. Obtain prepared slides of the three types of cartilage and find the following: Hyaline cartilage You should be able to find: ❍ chondrocytes living within lacunae ❍ matrix ❍ perichondrium – fibrous layer that surrounds the entire tissue Elastic cartilage You should be able to find: ❍ chondrocytes living within lacunae ❍ matrix 1 ❍ dark-staining elastic fibers within the matrix Fibrocartilage You should be able to find: ❍ chondrocytes living within lacunae; usually stacked in rows ❍ matrix ❍ thick collagen fibers within the matrix hyaline cartilage elastic cartilage fibrocartilage ACTIVITY 2: General Bone Identification and Classification In this activity, you will perform some basic bone identification and group bones based on their shapes. In Lab: 1. Obtain a box of bones and a skull. Go through your box of bones and do the following: ❍ Use the figure on the following page to identify each of the bones in your box. All of the bones should have a letter on them that corresponds to the letter on the box. If you find a bone that doesn’t belong in your box, please tell the instructor. ❍ Using Fig. 6-1 (p. 171) in your textbook, sort the bones into piles based on their shapes: long, short, flat, irregular, miscellaneous. Use the miscellaneous pile for groups of bones that come attached to each other (the skull, for example) and therefore cannot be easily sorted. Week 04 Lab: Skeletal Tissue and Bone Structure 2 ACTIVITY 3: Bone Markings In this activity, you will begin the process of becoming familiar with the different kinds of markings found on bones. Most bone markings fall into two basic categories: bumps, knobs, and projections that serve as attachment sites for tendons and ligaments or form joints; or depressions, cavities, holes, and channels that are passageways for blood vessels and nerves. Week 04 Lab: Skeletal Tissue and Bone Structure 3 In Lab: 1. Find the following examples of bone markings on the lab bones. Figure numbers refer to the textbook. Underlined terms are general bone anatomical terms; they (and many others) can be found in Table 6-1 (p. 172) in the textbook. a. Sites of tendon and ligament attachment: ❍ ischial tuberosity (Fig. 8-8, p. 242) ❍ greater trochanter (Fig. 8-11, p. 244) ❍ spinous process (Fig. 7-18, p. 219) b. Structures that form joints: ❍ head of humerus (Fig. 8-4, p. 237) ❍ acetabulum (Fig. 8-8, p. 242) ❍ facet on rib (Fig. 7-24, p. 227) c. Openings or channels ❍ foramen magnum (Fig. 7-5, p. 204) ❍ external acoustic meatus (Fig. 7-7, p. 206) ❍ obturator foramen (Fig. 8-8, p. 242) ACTIVITY 4: Gross Anatomy of Long Bones Most of the bones that we think of when we picture bones are long bones. In this activity, you will review the basic features of a long bone’s gross anatomy. In Lab: 1. Obtain a generously-sized long bone from your lab bones (a femur, tibia, or humerus will work fine). 2. Use Fig. 6-2 (p. 173) in the textbook to identify the following structures: ❍ diaphysis ❍ metaphysis ❍ two epiphyses (the distal and proximal epiphyses) 3. Obtain a preserved sawed bone. These bones are found in plastic bags. I recommend that you leave them in their bags for this activity and that you wash your hands after handling them. 4. On these bones, you should be able to identify the following: ❍ the epiphysis ❍ the diaphysis ❍ the periosteum, which covers all of the bone’s external surfaces; ❍ the smooth articular cartilage on the ends of the bones Week 04 Lab: Skeletal Tissue and Bone Structure 4 (this will not be very obvious through the bag, but do your best) ❍ the medullary cavity within the diaphysis ❍ the yellow marrow inside the medullary cavity ❍ the spongy bone, with its trabeculae and marrow spaces, inside the epiphysis ACTIVITY 5: Microscopic Anatomy of Compact Bone In this activity, you will observe compact bone microscopically. You will also observe both baked and acidsoaked bones in order to appreciate the contributions of both the organic and inorganic components of bone matrix. In Lab: 1. Obtain a prepared slide of compact bone. This slide was prepared by simply grinding a chip off of a larger bone and mounting it on the slide. That means that there are no other tissues present, nor are any of the cells preserved. 2. On this slide, you should be able to identify the following: ❍ an osteon ❍ a central canal ❍ lamellae ❍ lacunae (which would have previously contained osteocytes) ❍ canaliculi 3. We also have an anatomical model of an osteon. See if you can find these structures on the model as well. Week 04 Lab: Skeletal Tissue and Bone Structure 5 4. Obtain examples of both baked and acid-soaked bones. Both are unpreserved bones that come from supermarket rotisserie chickens. Even though there’s no preservative here, it is recommended to leave the acid-soaked bones in their bag (in case there’s any residual acid). ❍ Bones that are baked become dehydrated and essentially lose the organic component of their matrix. What remains is the hard, brittle inorganic component (hydroxyapatite crystals). ❍ Soaking bones in acid dissolves the hydroxyapatites, leaving only the collagen fibers of the organic component behind. Notice the flexibility that the collagen fibers provide the bone. Week 04 Lab: Skeletal Tissue and Bone Structure 6