COMPLETE SCHOOL PROJECT TOPICS & MATERIALS :
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ABSTRACT

This project work introduced some knowledge about the basics involved in finding the contents of bone. This project work deals with the principle of qualitative analysis of cations and anions. Skeletal system plays an integral part of most of the animals “what is it that makes It to form an integral part?”. The solution to this question can be understood more succinctly from this project work.

        This project indeed would be a revolution in the world, where there is increasing worry about problems of bone like osteoporosis and osteomalacia. In this industrial age amount of calcium content in bone is also reducing; this project work would indeed be a very good solution.

 

 

TABLES OF CONTENTS

Title Page

Certification

Dedication

Acknowledgement

Table of contents

Terminologies

Several terms  are  used  to  refere  to  features and components of bones  throughout  the  body

s/no	Bone features	Definition
1	Articular  process	A projection  that  contacts an  adjacent  bone .
2	Articulation	The region  where  adjacent  bones contact each  other- a joint.
3	Canal	A long, tunnel-like foramen, usually a  passage for notable nerves or blood vessels.
4	Condyle	A large, rounded articular  process.
5	Crest	A prominent ridge.
6	Eminence	A relatively small  projection  or bump
7	Facet	A small, flattened articular surface
8	Epicondyle	A projection  near  to a  condyle but  not  part of the joint.
9	Foramen	An  opening  through  a  bone.
10	Fossa	A broad shallow depressed area.
11	Fovea	A small  pit  on  the head  of a  bone.
12	Labyrinth	A cavity within  a bone.
13	Line	A long, thin  projection, often  with  a  rough surface. also  known as  a  ridge
14	Malleolus	One of two specific  protuberansces of bone in  the ankle.
15	Meatus	A short  canal
16	Process	A relatively large projection  or prominent bump (gen.)
17	Ramus	An  arm-like branch of the  body  of a bone
18	Sinus	A cavity within a cranial bone.
19	Spine	A relatively long, thin projection  or bump.
20	Suture	Articulation between  cranial bones.
21	Trochanter	One of two specific tuberosities located  on the fermur.
22	Tubercle	A projection or bump with a roughened s surface, generally  smaller than  a  tuberosity.
23	Tuberosity	A projection  or bump with a roughened  surface.

 

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:

1. Intra membranous Ossification
2. 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
   • 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).

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

1. 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.
2. 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;

1. 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.
2. Bone lining cells are essential inactive osteoblasts. They cover all of the available bone surface and function as barrier for certain ions.

• 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.

1. 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.

1.2.2        MOLECULAR STRUCTURE

1. Matrix: The majority of bone is made of the bone matrix. It is composed primarily of inorganic Hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) and organic collagen. Bone is formed by the hardening of this matrix around entrapped cells. When these cells become entrapped from osteoblasts they become osteocytes.
2. Inorganic: The inorganic is mainly crystalline mineral salts and calcium, which is present in the form hydroxyapatite. The matrix is initially laid down as unmineralized osteoid (manufactured by osteoblasts). Mineralization involves osteoblasts secreting vesicles containing alkaline phosphate. This cleaves the phosphate groups and acts as the foci for calcium and phosphate deposition. The vesicles the rupture and act as a center for crystals grow on.

• Organic: The organic part of matrix is mainly composed of Type I collagen. This is synthesized intracellularly as tropocollagen and then exported, forming fibrils. The organic part is also composed of various growth factors, the functions of which are not fully known. Factor present include Glucosaminoglycans. Osteonectin, Osteocalcin, bone sialo protein, Osteopontin and cell attachment factor. One of the main things that distinguishes the matrix of a bone from that of another cell is that the matrix in bone is hard.

1. Woven and Lamella: Two types of bone can be identified microscopically according to the pattern of collagen forming the osteoid (collagenous support tissue of Type I collagen embedded in Glycosaminoglycan gel).
2. Woven bone, which is characterized by haphazard organization of collagen fibers and is mechanically weak.
3. Lamellar bone which has a regular parallel alignment of collagen into sheets (Lamellae) and is mechanically strong.

Woven bone is produed when osteoblasts produce osteoid rapidly which occurs initially in all fetal bones (but is later replaced by more resilent lamellar bone). In adult woven bone is created after fractures or in paget’s disease. Woven bone is weaker, with a smaller number of randomly oriented collagen fibers, but forms quickly; it is this appearance of the fibrous matrix that the bone is termed woven. It is soon replaced by lamellar bones, which is highly organized in concentric sheets with a much lower proportion of osteocytes to surrounding tissue. Lamellar bone, which makes it first appearance in the fetus during the third trimester, is stronger and filled with many collagen fibers parallel to other fibers in the same layer (these parallel columns are called osteons). In cross-section the fibers run in opposite direction in alternating layers, much like in plywood, assisting the bone’s ability to resist torsion forces. After a fracture, woven bone forms initially and is gradually replaced by lamellar bone during a process known as “bony substitution”. Compared to woven bone, lamella bone formation takes more slowly. The orderly deposition of collagen fibers restricts the formation of osteoid to about 1 to 2 micro meter per day. Lamellar bone also requires a relatively flat surface to lay the collagen fibers in parallel or concentric layers.       These terms are histogic, in that a microscope is necessary to differentiate between the two types

1.3   CHARACTERISTIC OF BONE

The primary tissue of bone, osseous tissue, is a relatively hard and has light weight composite material formed mostly of calcium phosphate in the chemical arrangement termed Calcium Hydroxyapatite (Ca₁₀(PO₄)(OH)₂) (this is the osseous tissue that gives bone their rigidity).

It has relatively high compressive strength but poor tensile strength of 104-121 Mpa meaning it resists pushing force well, but not pulling forces. While bone is essentially brittle, it does have a significant degree of elasticity, contributed chiefly by collagen. All bones consist of living and dead cells embedded in the mineralized organic matrix that make up osseous tissue.

1.4   TYPES OF BONE

There are five types of bones in the human body:

Long bone, short bone, flat bone, irregular bone and sesamoid bone.

1. Long bones: They are characterized by a shaft, the diaphysis that is much longer in length than width. They are comprised mostly of compact bone with lesser amounts of marrow, which is located within the medullary cavity and spongy bone. Most bones of the limbs including those of the fingers and the toes are long bones. The exceptions are those of the wrist, ankle and kneecap.
2. Short bone: are roughly cube shaped, and have only a thin layer of compact bone surrounding a spongy interior. The bones of the wrist and ankle are short bones as are the sesamoid bones.

• Flat bones: are thin and generally curved, with two parallel layers of compact bones sandwiching a layer of spongy bone. Most of the bones of the skull are flat bones, as is the sternum.

Sesamoid bones: Are bones embedded in tendons. Since they act to hold the tendon further away from the joint, the angle of the tendon is increased and thus the leverage of the muscle is increased. Examples of sesamoid bones are the patella and the pisiform.

1. Irregular bones: do not fit into the above categories. They consist of thin layers of compact bone surrounding a spongy interior. As implied by the name, their shapes are irregular and complicated. Often this irregular shape is due to their many centers of ossification or because they contain bony sinuses. The bones of the spine, hips and some bones of the skull are irregular bones. Example include the ethmoid and sphenoid bones.

 

1.5   FUNCTIONS OF BONE

Bones have eleven main functions:

1. MECHANICAL FUNCTIONS OF BONE
2. Protection: Bones can serve to protect internal organs, such as the skull protecting the brain or the ribs protecting the heart and lungs.
3. Movement: Bones, skeletal muscles, tendons, ligament and joint function together to generate and transfer forces so that individual body parts or the whole body can be manipulated in three dimensional space. The interaction between bone and muscle is studied in Biomechanics.

• Shape: Bones provides a frame to keep the body supported.

1. Sound transduction: Bones are important in the mechanical aspect of overshadowed hearing.
2. SYNTHETIC FUNCTION OF BONE
3. Blood production: The marrow, located within the medullary cavity of long bones are interstice of cancellous bones, produces blood cells in process called “Haematopoiesis”
4. METABOLIC FUNCTION OF BONE
5. Mineral Storage: Bones act as reserves of minerals important for the body, most notably calcium, phosphorus etc.

• Growth Factors Storage: Mineralized bone matrix stores important growth factors such as insulin-like growth factor, transforming growth factor, bone morphogenetic proteins and others.
• Fat storage: The yellow bone marrow acts as a storage reserve of fatty acids

1. Acid-Base balance: Bones buffers the blood against excessive pH changes by absorbing or releasing alkaline salts.
2. Detoxification: Bone tissues can also store heavy metals and other foreign element, removing them from the blood and reducing their effects on other tissues. These can later be gradually release for excretion.
3. Endocrine organs: Bone controls phosphate metabolism by releasing fibroblast growth factors -23 (FGF-23) which acts on kidneys to reduce phosphate reabsorption. Bone cells also release a hormone called osteocalcin which contribute to the regulation of blood sugar (glucose) and fast deposition. Osteocalcin increases both the insulin secretion and sensitivity, in addition to boosting the number insulin-producing cells and reducing stores of fat.

1.6   USES OF BONE

Bones from slaughtered animals  have  a  number  of  uses. They have been used as crafting  materials,  for  buttons,  handles,  ornaments etc. A special genre is scrimshaw. Ground bones are used as an organic phosphorus- nitrogen fertilizer and as additive in animal  feed. Bones, in  particular  after  calcinations  to bone ash  is  used as source of calcium phosphate for the production  of bone china and  previously  also  phosphorus chemicals.