BONE LABORATORY DEMONSTRATIONS. These demonstrations are found on the bulletin boards outside the MCO Bookstore.

Transcription

1 BONE LABORATORY DEMONSTRATIONS These demonstrations are found on the bulletin boards outside the MCO Bookstore.

2 COMPACT & TRABECULAR BONE - LM When viewed under the polarizing light microscope, the layering (lamella) of collagen fibers can be seen as alternating light and dark bands. In the compact bone (CB), the lamellae form concentric circles around the Haversian canal (HC). Dark-staining osteocytes are within the concentric rings. In addition, interstital lamellae (IL) can be clearly defined. In the trabecular bone (TB), the angular trabecular packets (TP) are clearly defined by the lamellae. 100X

3

4 FORMING OSTEON This is characterized by its large Haversian canal ( FO; contains air bubble) and has only 2 layers of osteocytes. No osteoblasts can be observed lining this incomplete osteon because this is a ground bone section. 200X

5 DECALCIFIED CORTICAL BONE Look for the following features: Periosteum (PO), Osteon (O), Outer Circumferential Lamellae (OCL), Inner Circumferential Lamellae (ICL) and Endosteum (E). 200X

6 OSTEOCYTE - TEM Transmission electron micrograph of osteocyte surrounded by mineralized bone matrix (BM). All osteocytes are surrounded by a thin zone of uncalcified matrix call osteoid (ZO). What does the osteoid consist of? In what form is the mineral? 8,000X Kessel & Kardon, 1979

7 GROUND BONE SECTION - SEM The Lacunae (La) of the osteocytes are arranged around the Haversian canal (HC) of this Haversian system. The small openings (Ca) are the beginning of the small tunnels or canaliculi. What is the function of this small tunnel? 1,300X Inset: equivalent light micrograph of ground bone section. 1,000X Kessel & Karden, 1979 The lower micrograph demonstrates much of the same with the inset comparing the structure to a light micrograph of ground bone.

8

9 TRABECULAR BONE SURFACE - SEM Inset: The lacunae of osteocytes (OL) and Howship's lacunae (HL) are observed on the bone surface of this trabeculae. 265X. Large micrograph: Two layers of concentric lamellae (LM) can be seen around the inner aspect of a Haversian system. What cell lies in the Howship's lacunae? Why is this lacunae larger that that of the osteocytes? 600X Kessel & Karden, 1979

10 OSTEOCYTE - SEM Osteocyte (OS) in the lacunae (La) of the bone matrix in compact bone (BM). Processes of osteocytes (OP) enter the canaliculi (Ca) to communicate with other cells. 900X. Kessel & Karden, 1979

11 CANCELLOUS BONE -SEM In this micrograph the bone marrow has been removed to expose the cancellous or spongy (CaB) that is composed of numerous trabeculae (Tr). The small holes (arrows) are where small blood vessels enter to supply nutrients to the compact bone via Volkmann's canals. SEM 100X Kessel & Karden, 1979

12 OSTEOCLASTS - SEM Osteoclasts (Oc) of different shapes are observed eating into the bone matrix. Numerous microprocesses make up the ruffled border of the cell where bone removal occurs. SEM 500X Kessel & Karden, 1979

13

14 PARTIALLY MINERALIZED BONE MATRIX - TEM The bone osteoid contains collagen fibers (CF) and areas of mineralization (*), which appear as black foci along the surface of the collagen fibers and spread out. TEM 7,000X Kessel & Karden, 1979

15

16 BONE DEVELOPMENT LABORATORY DEMONSTRATIONS These demonstrations are found on the bulletin boards outside the MCO Bookstore.

17 EPIPHYSEAL PLATE - LM The epiphyseal plate (EP), which contains four zones of hyaline cartilage between the epiphysis (E) and the diaphysis (D) of a long bone, is the mechanism by which long bones are lengthened. 50X

18 EPIPHYSEAL PLATE - HIGH POWER The resting zone (RZ) appears as normal hyaline cartilage with a random scattering of chondrocytes. The proliferating zone (PZ) is characterized by columns of thin flattened cells. This is where mitosis and interstitial growth occurs. The zone of hypertrophy (HZ) is identified by its columns of greatly enlarged chondrocytes. The zone of calcification (ZC) is difficult to visualize because the calcium has been removed during tissue processing and takes a special stain to visualize. The end of the epiphyseal plate is located at the tip of the invading blood vessels (BV) or resorption front. The primary ossificaition zone (POZ) is characterized by osteoblasts laying down bone matrix on the remanents of calcified cartilage. 200X

19

20 FETAL SKULL These micrographs are to orient you to the fetal rodent skull and demonstrate where to look for the process of intramembranous ossification. Sections of the skull in your slide box can be taken either from the region of the nasal cavity (A) or from farther caudal in the region of the cranial vault containing the brain (B). A. The nasal cavity (NC) in rodents normally is surrounded by blue staining hyaline cartilage (*) which is underneath the layer (arrows) where intramembranous ossification is occuring. NOTE that the cartilage is separate from the fibrous layer and not involved in the intramembranous ossification process. The oral cavity (OC) contains the tongue. B. In this section the brain (B) is enclosed by the flat bones forming the cranial vault. The process of intramembranous bone formation is more advanced so bone has already formed throughout the layer indicated by the arrows.

21