Question

10) Answer the following briefly:

a) What are the three types of cartilage and what distinguishes them from one another? Can you identify a histological section of them?

b) Aside from structural support what are other functions of bone?

c) What are two ways to view bone histologically?

4. What are the 2 methods of ossification, their process and how they differ.

d) What does an osteoclast actually do and what are the morphological zones we talked about?

e) How do bones grow in length compared to in width?

Thank you!

Answer 1

a). There are three different types of cartilage: elastic (A), hyaline (B), and fibrous (C).

Hyaline Cartilage

Hyaline cartilage is the most widespread cartilage type and, in adults, it forms the articular surfaces of long bones, the rib tips, the rings of the trachea, and parts of the skull. This type of cartilage is predominately collagen (yet with few collagen fibers), and its name refers to its glassy appearance.

In the embryo, bones form first as hyaline cartilage before ossifying as development progresses. Hyaline cartilage is covered externally by a fibrous membrane, called the perichondrium, except at the articular ends of bones; it also occurs under the skin (for instance, ears and nose).

Hyaline cartilage is found on many joint surfaces. It contains no nerves or blood vessels, and its structure is relatively simple.

If a thin slice of cartilage is examined under the microscope, it will be found to consist of cells of a rounded or bluntly angular form, lying in groups of two or more in a granular or almost homogeneous matrix. These cells have generally straight outlines where they are in contact with each other, with the rest of their circumference rounded.

They consist of translucent protoplasm in which fine interlacing filaments and minute granules are sometimes present. Embedded in this are one or two round nuclei with the usual intranuclear network.

Fibrous cartilage

Fibrous cartilage has lots of collagen fibers (Type I and Type II), and it tends to grade into dense tendon and ligament tissue. White fibrocartilage consists of a mixture of white fibrous tissue and cartilaginous tissue in various proportions.

It owes its flexibility and toughness to the fibrous tissue, and its elasticity to the cartilaginous tissue. It is the only type of cartilage that contains type I collagen in addition to the normal type II.

Fibrocartilage is found in the pubic symphysis, the annulus fibrosus of intervertebral discs, menisci, and the temporal mandibular joint.

Elastic Cartilage

Elastic or yellow cartilage contains elastic fiber networks and collagen fibers. The principal protein is elastin.

Elastic cartilage is histologically similar to hyaline cartilage but contains many yellow elastic fibers lying in a solid matrix. These fibers form bundles that appear dark under a microscope. They give elastic cartilage great flexibility so it can withstand repeated bending.

Chondrocytes lie between the fibers. Elastic cartilage is found in the epiglottis (part of the larynx) and the pinnae (the external ear flaps of many mammals, including humans).

b).

The major functions of the bones are facilitation of movement, protection of internal organs, storage of minerals and fat, and hematopoiesis. Together, the muscular system and skeletal system are known as the musculoskeletal system.

c). The analysis of hard tissue (bone and tooth) can be approached on many levels, ranging from the macroscopic to the molecular level. Intermediate to this range is the tissue level or histological level of organization. By definition, histology means the science of the tissues. More specifically, histological analysisis the study of the microscopic anatomy of tissues in plants and animals. Thus, histological analysis requires specialized equipment to prepare tissues for analysis and to magnify structures, making them visible. There are two analytical approaches used in anthropology when studying microstructures. One, referred to as histomorphology, is the qualitative analysis of microstructure morphology and organization. The other, referred to as histomorphometry, is the quantitative study of the microscopic organization and structure of tissue. These analyses can be performed using a static or dynamic approach to studying tissue. Static histological analysis allows for.

4. There are two processes resulting in the formation of normal, healthy bone tissue: Intramembranous ossification is the direct laying down of bone into the primitive connective tissue (mesenchyme), while endochondral ossification involves cartilage as a precursor.

The process of bone formation is called osteogenesis or ossification. After progenitor cells form osteoblastic lines, they proceed with three stages of development of cell differentiation, called proliferation, maturation of matrix, and mineralization.

Differ :The major events of membranous ossification occur in the periosteum, whereas the area of endochondral ossification is enclosed by the perichondrium.

d). Osteoclasts are the cells that degrade bone to initiate normal bone remodeling and mediate bone loss in pathologic conditions by increasing their resorptive activity. They are derived from precursors in the myeloid/ monocyte lineage that circulate in the blood after their formation in the bone marrow.

The external shape of bones is formed by a dense cortical shell (cortical or compact bone), which is particularly strong along the diaphysis, where the bone marrow is located. ... The bony end plates are covered by the articular cartilage, consisting of a mineralized deep zone and a nonmineralized surface zone.

e). In endochondral ossification, bone develops by replacing hyaline cartilage. Activity in the epiphyseal plate enables bones to grow in length (this is interstitial growth). Appositional growth allows bones to grow in diameter. Remodeling occurs as bone is resorbed and replaced by new bone.