Analysis Of Contents Of Cow And Goat Bone Ash

CHAPTER ONE

1.0 INTRODUCTION

Bones are rigid organs from part of the endoskeleton of the vertebrates. They support and protect the various organs of body production red and white blood cells and store minerals. Bone tissue is a type of tense connective tissue. Bone comes in a variety of shapes and has a complex internal and external structure, are light weight yet strong and hard and serve multiple functions. One of the types of tissue that makes up bone is the mineralized osseous tissue, also called bone tissue that gives it rigidity and a coral-like three dimensional internal structure. Other types of tissue found in bones include marrow endosteum, periosteum, nerves, blood vessel and cartilage. “At birth, there are over 270 bones in an infant human’s body”. (steele D. Gentry et. al (1998). The Anatomy and Biology of the Human skeleton, Texas A&M University press page 4 ISBN-0-89096-300-2), but many of these bones fused together as the child grows, leaving a total of 206 separate bones in an adult. “The largest bone in the human body is the femur and the smallest bones are auditory ossicles.” (Schmiedder et. al (1934) parent and child. An Introductory Study of Parent Education page 31).

  Bones are also a dynamic tissue that performs mechanical, biological and chemical functions and it depends on chemical and physical properties and are affected by age, nutrition, hormonal status and diseases. (Loveridge 1999), the skeletal system forms the external structure and appearance of mammalian vertebrate species and has the obvious functions locomotion, structural support of the body and protection of soft tissue such as brain, heart, spinal cord and lungs. Bone also serves as metabolic reservoir of Calcium (Ca), Phosphorus (P) and other minerals. Also, it houses cells responsible for bone formation and resorption (Decke et. al 1993).

1.1 FORMATION OF BONE

The formation of bone during the fetal stage of development occurs by two processes:

i. Intra membranous Ossification

ii. Endochondral Ossification

1.1.0 INTRAMEMBRANOUS OSSIFICATION

This mainly occurs during formation of the flat bones of the skull; the bone is formed from mesenchyme tissue. The steps in intramembranous ossification are:

1. Development of ossification centre

2. Calcification

3. Formation of trabeculae

4. Development of periosteum

1.1.1 ENDOCHONDRAL OSSIFICATION

Endochondral ossification on the other hand, occurs in long bones such as limbs; the bone is formed from cartilage. The steps in endochondral ossification are:

1. Development of cartilage model

2. Growth of cartilage model

3. Development of primary ossification center

4. Development of secondary center

5. Formation of articular cartilage and epiphyseal plate.

Endochondral ossification begins with points in the cartilage called primary ossification centers” they mostly appear during fetal development, though a few short bones begin their primary ossification after birth. They are responsible for the formation of the diaphyses of long bones, short bones and certain parts of irregular bones. 

Secondary ossification occurs after birth, and forms the epiphyses of long bones and the extrimities of irregular and flat bones. The diaphysis and both epiphyses and a long bone are separated by a growing zone of cartilage (the epiphyseal plate). When the child reaches skeletal maturity (18-25 years of age), all of the cartilage is replaced by bone, fusing the diaphysis and both epiphyses together (epiphyseal closure).

1.1.2 BONE MARROW

Bone marrow can be found in almost any bone that holds cancellous tissue. In newborns, all such bones are filled exclusively with red marrow, but as the child ages it is mostly replaced by yellow of fatty marrow. In adults, red marrow is mostly found in the marrow bones of the femur, the ribs, the vertebrae and pelvic bones.

1.1.3 REMODELING

Remodeling or bone turnover is the process of resorption followed by replacement of bone with little change in shape and occurs throughout a person’s life. Osteoblasts and osteoclasts, coupled together via pancrine cell signaling, are referred to as bone remodeling units. Approximately 10% of the skeletal mass of an adult is remodeling each year.

1.1.4 PURPOSE

The purpose of remodeling is to regulate calcium homeostasis, repair micro-damaged bones (from every day stress) but also to shape and sculpture the skeleton during growth.

1.1.5 CALCIUM BALANCE

The process of bone resorption by the osteoclasts releases stored calcium into the systematic circulation and is an important process in regulating calcium balance. As bone formation actively fixes circulating calcium in its mineral form, removing it from the blood stream, resorption actively unfixes it thereby increasing circulating calcium levels. These processes occur in tandem at site specific locations.

1.1.6 REPAIR

Repeated stress such as weight bearing exercise or bone healing result in the bone thickening at the point of maximum stress (Wolff’s law). It has been hypothesized that this is a result of bones piezoelectric properties which cause bone to generate small electrical potential under stress.

1.1.7 PARACRINE CELL SIGNAL

The action of osteoclasts and osteoblasts are controlled by a number of chemical factors which either promote or inhibit the activity of the bone remodeling cells, controlling the rate at which the bone is made, destroyed or changed in shape. The cells also use paracrine signaling to control the activity of each other.

1.1.8 OSTEOBLAST STIMULATION

Osteoblast can be stimulated to increase bone mass through increased secretion of osteoid and by inhibiting the ability of osteoclasts to breakdown osseous tissue.

Bone building through increase secretion of osteoid is stimulated by the secretion growth hormone by the pituitary, thyroid hormone and the sex hormones (estrogens and androgens). These hormones also promote increased secretion of osteoprotegerin. Osteoblasts can also be induced to secrete a number of cytokines to promote reabsorbtion of bone by stimulating osteoclast activity and differentiation from progenitor cells. Vitamin D, parathyroid hormone and stimulation from osteocytes induce osteblasts to increase secretion of RANK ligand and interleukin 6, which cytokines then stimulate increased reabsorbtion of bone by osteoclasts. These same compounds also increase secretion of macrophage colony-stimulating factor by osteoblasts, which promotes the differentiation of progenitor cells into osteoclasts and decrease secretion of osteoprotegerin.  

1.1.9 OSTEOCLAST INHIBITION

The rate at which osteoclast reabsorb bone is inhibited by calcitonin and osteoprotegerin. Calcitonin is produced by parafollicular cells in the thyroid gland and can bind to receptors on osteoclasts to directly inhibit osteoclast activity. Osteoprotegerin is secreted by osteoblasts and is able to bind RANK-L, inhibiting the osteoclast stimulation.

1.2 INDIVIDUAL BONE STRUCTURE

Bones is not a uniformly solid material, but rather has some spaces between its hard elements. 

a. Compact Bone (cortical bone): The hard outer layer of bone is composed of compact bone tissue, so-called due to its minimal gaps and spaces. This tissue gives bones their smooth, white and solid appearance and account for 80% of the total bone mass of an adult skeleton. Compact bone may also be referred to as dense bone.

b. Trabecular Bone: Filling the interior of the bone is the trabecular bone tissue (an open cell porous network also called cancellous or spongy bone), which is composed of a network rod and plate-like element that make the overall organ lighter and allowing room for blood vessels and marrow. Trabecular bone account for the remaining 20% of the total bone mass but has nearly ten times the surface area of compact bone. If for any reason there is an alteration in the strain to which the cancellous subjected there is a rearrangement of the trabeculae. Although adult bone exist in both cancellous and compact bone forms, there is no microscopic different between the two.

1.2.1 CELLULAR STRUCTURE

There are several types of cells constituting the bone;

i. Osteoblasts and mononucleate bone-forming cells that descend from osteoprogenitor cells. They are located on the surface of osteoid seams and make a protein mixture known as osteoid, which mineralizes to become bone. The osteoid seam is a narrow region of newly formed organic matrix that is not yet mineralized. Located on the surface of a bone. Osteoid is primarily composed of Type I collagen. Osteobalsts also manufacture hormones, such as prostaglandins to act on the bone itself. They robustly produce alkaline phosphate, an enzyme that has a role in the mineralization of bone, as well as many matrix proteins. Osteoblasts are the immature bone cells.

ii. Bone lining cells are essential inactive osteoblasts. They cover all of the available bone surface and function as barrier for certain ions.

iii. Osteocytes originate from osteoblasts that have migrated into and become trapped and surrounded by bone matrix that they themselves produce. The spaces they occupy are known as lacunae. Osteocytes have many processes that reach out to meet osteoblast and other osteocytes probably for the purpose of communication. Their functions include to varying degrees: formation of bones; matrix maintenance and calcium homeostasis. They have also been shown to act as machano-sensory receptors that regulate the bone’s response to stress and mechanical load. They are mature cells.

iv. Osteoclasts are the cells responsible for bone resorption (remodeling of bone to reduce its volume). Osteoclasts are large, multinucleated cells located in bone surfaces in what are called Howship’s lacunae or resorption pits. These lacunae, or resoprtion pits are left behind after the breakdown of the bone of the bone surface. Because the osteoclasts are derived from a monocyte stem-cell lineage, they are equipped with phagocytic-like mechanisms similar to circulating macrophages. Osteoclasts mature and/or migrate to discrete bone surface. Upon arrival active enzymes, such as tartrate resistant acid phosphatase, are secreted against the mineral substrate.