Lecture Notes VAN-111 Scd

7/30/2019 Lecture Notes VAN-111 Scd

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Lecture notes of VAN-111 prepared by Dr Subhash C Dubal, Professor of Anatomy

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Bone, the material that makes vertebrates distinct from other animals, has evolved

over several hundred million years to become a remarkable tissue. Bone is a material

that has the same strength as cast iron, but achieves this while remaining as light aswood.

INTRODUCTION

A. DEFINITIOS:

Anatomy

Anatomy is a branch of biological science, which deals with the study of forms and

structures of the organisms.

Branches of anatomy:

i. Gross anatomy: It is the branch of anatomy, which deals with the study offorms and structures of the organisms with naked eyes.

ii. Histology: It is the branch of anatomy, which deals with the study of formsand structures of the organisms with the help of microscope, and hence, it isalso called as microscopic anatomy. The study of cell and its structure is

called as Cytology.

iii. Developmental Anatomy or Embryology: Itis the branch of anatomy, whichdeals with the study of successive changes, which occur during development

from the time of fertilization (zygote-formation) to the fully developed young

one. Ontogeny is related with the development of an individual species while

Phylogeny concerns the development of an entire phylum.

iv. Radiological anatomy: It is the branch of anatomy, which deals with thestudy of forms and structures of the organisms with the help irridations like X-

rays, Ultrasound etc.

B. Types of Anatomy

1. Special Anatomy: It is one of the types of anatomy, which deals with the study offorms and structures of a particular species of animal. For examples, bovine

anatomy (anatomy of ox and buffalo), equine anatomy (anatomy of horses),canine anatomy (anatomy of carnivores dog, cat), ovine anatomy (anatomy of

sheep), caprine anatomy (anatomy of goat), avian anatomy (anatomy of birds)and

medical anatomy (anatomy of human beings) etc.

2. Comparative Anatomy: It is one of the types of anatomy, which deals with thedescription and comparison of forms and structures of different species of animals

and forms a basis for their classification.Veterinary anatomy: It is one of the types of anatomy, which deals with the descriptionand comparison of forms and structures of principal domestic animals.

The principal domestic animals are ox, buffalo, horse, dog and cat, sheep and

goat, pig, poultry etc.


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C. Methods of Study Gross Anatomy

1. Systematic Anatomy: The systematic anatomy deals with the study ofvarious systems of the animal body one after another.

2. Regional Anatomy: The regional anatomy deals with the study of

various regions of an animal body (e.g. neck region; includes study of

muscles, bones, organs, blood vessels and nerves of this region) and3. Applied Anatomy: The applied anatomydeals with the use of knowledge

of anatomy in practical subjects namely surgery, medicine and

gynaecology and obstetrics (clinical subjects); diagnostic technique,pathology, livestock production and management, physiology, etc

The animal body is composed of cells. The cell is the structural and functional

unit of life (organisms). An assembly of cells forms tissues; the assembly of tissues formsorgans, the assembly of organs forms systems and the assembly of systems form the

animal body. The study of organs and / or systems forms various subjects of knowledge.

Osteology : Study of bones.Myology : Study of muscles.

Arthrology : Study of joints.

Splanchnology : Study of organs/viscera of tubular systems which communicate with the

exterior through their one or both the ends.

Angiology : Study of cardio-vascular and lymphatic systems.

Neurology: Study of nervous system.

Aesthesiology: Study of sense organs.

Biomechanics: It is a branch of mechanobiology that deals with the application of laws

of mechanics to the biological systems.

D. Topographic terms

Those terms which are used to describe various organs or parts of body with

respect to their location, directions, relations etc. It is assumed that the animal is inordinary standing position.

I. Planes of body

1. Median plane: It is the pane of the body, which passes through the mid-

longitudinal axis of the body and divides the body into equal parts. It is also called as

mid-sagittal plane.

2. Sagittal plane: The plane of the body that is parallel to the median plane is

known as sagittal plane. It is also called as paramedian plane.

3. Transverse plane: The plane of the body that is perpendicular to the median

plane is known as transverse plane.4. Frontal plane: The plane of the body that is perpendicular to both the median

and transverse planes is known as transverse plane.


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II. Surfaces

a. With respect to median plane:

1. Medial surface: The surface of a bone or an organ, which is nearer to the

median plane, is called as medial surface.

2. Lateral surface: The surface of a bone or an organ, which is farther away

from the median plane, is called as lateral surface.

b. With respect to head / tail:

1. Cranial surface: The surface of a bone or an organ, which is nearer to the headof the animal than any surfaces, is called as cranial surface.

2. Caudal surface: The surface of a bone or an organ, which is farther away from

the head of the animal than any surfaces, is called as caudal surface.

c. With respect to sky / ground:

1. Dorsal surface: The surface of a bone or an organ, which is nearer to the sky

(or farther away from the ground) than any surfaces, is called as dorsal surface.

2. Ventral surface: The surface of a bone or an organ, which is farther awayfrom the sky (or nearer to the ground) than any surfaces, is called as ventral surface.

Modification of cranial/caudal surface w.r.t. limbs:

1. Dorsal surface: The cranial surface of a bone or an organ in manus (from

carpal joint in forelimb to the toe) and pes (from tarsal joint in hind limbs to the

toe) regions is called as dorsal surface.

2. Palmer surface: The cranial surface of a bone or an organ in manus region

(from carpal joint in forelimb to the toe), is called as dorsal surface.

3.Planter surface: The caudal surface of a bone or an organ in manus (fromcarpal joint in forelimb to the toe) and pes (from tarsal joint in hind limbs to the

toe) regions is called as planter surface.

d. With respect to long axis of the body:

1. Axial surface: The surface of a bone or an organ, which is nearer to the longaxis of the body, bone or organ, is called as cranial surface.

2. Abaxial surface: The surface of a bone or an organ, which is farther away

from the long axis of the body, bone or organ, is called as abaxial surface.

III. Extremities

a. With respect to head / tail:

1. Cranial extremity: The end of a bone or an organ, which is nearer to the head

of the animal, is called as cranial extremity.

2. Caudal surface: The end of a bone or an organ, which is farther away from the

head of the animal, is called as caudal extremity.

Modification of cranial extremity w.r.t. head:

1. Rostral extremity: The cranial end of a bone or an organ in the head is called

as rostral extremity.


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c. With respect to sky / ground:

1. Dorsal extremity: The end of a bone or an organ, which is nearer to the sky orfarther away from the ground, is called as dorsal extremity.

2. Ventral extremity: The end of a bone or an organ, which is farther away from

the sky, is called as ventral extremity.

d. With respect to long axis of the body:1. Proximal extremity: The end of a bone or an organ, which is nearer to the

long axis of the body, is called as proximal extremity.

2. Distal extremity: The end of a bone or an organ, which is farther away from

the long axis of the body, is called as distal extremity.

E. Modifications of bone surfaceSince the bone acts as lever for locomotion, it provides attachments to the muscles

and ligaments of the joint(s). To achieve these functions, the surface of the bone has

some projections and depressions. They are of two types: articular and non-articula.

1. Articular projections;

i. Head: A spherical articular projection is known as head.

ii. Condyle: A cylindrical articular projection is known as condyle.iii. Trochlea: A pulley-like articular projection is known as trochlea.

iv. Facet: A flat articular surface (projection) is known as facet.

2. Articular depressions:

i. Glenoid cavity: A shallow articular concavity is known as glenoid cavity.

ii. Cotyloid cavity: A deep articular concavity is known as cotyloid cavityiii. Acetabulum: The largest articular concavity is known as acetabulum.

3. Non-articular projections:

i. Line: A non-articular linear ridge is called as line.

ii. Crest: A non-articular sharp ridge is called as crest.

iii. Spine: A non-articular pointed projection is called as spine.iv. Epicondyle: A non-articular eminence attached on either side of the condyle

is called epicondyle.

v. Tubercle: A non-articular small projection is called as tubercle.

vi. Tuberosity: A non-articular large projection is called as tuberosity.vii. Trachanter: The largest non-articular projection is called as trochanter.

viii. Process: Any non-articular projection is called as process.

ix. Notch: A non-articular indentation at the brim of a concavity is called as

notch. It may be articular or non-articular.x. Cornua: A non-articular horn-like projection is called as cornua.

xi. Hamulus: A non-articular hook-like projection is called as hamulus


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4. Non-articular depressions:

i. Sulcu: A non-articular shallow groove is called as sulcus.

ii. Fissure: A non-articular deep groove is called as fissure.

iii. Fossa: A non-articular shallow depression is called as fissure.

iv.Fovea: A non-articular deep and narrow depression is called as fissure.v. Foramen: A hole in the bone or an organ is called as foramen.vi. Hiatus: A non-articular shallow depression having more than one foramina

is called as hiatus.

vii. Canal: A tunnel in the bone or organ is called as canal.viii. Sinus: An air space inside a bone lined by mucous membrane and having

communication with the exterior is called as sinus.


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OSTEOLOGY

Osteology: It is the study of bones. The bone is the second hardest substance after the

enamel of the tooth in the animal body.

Bone is a hard, but brittle, tissue and is relatively light per unit volume. Bone is adynamic tissue, which throughout life bone tissue is continually being formed and

resorbed. This remodeling and reorganization of bone tissue is the result of many

factors including:1. Mechanical stimuli

2. Metabolic causes (lack of dietary calcium, illness, aging)

3. Endocrine changes

4. Effects of drugs.

Functions of bone:

1. It forms the framework of the body.

2. It protects the vital organs like brain, spinal cord, heart etc.3. It provides support and attachment to the muscles.

4. It acts as a lever for locomotion.5. It is one of the important organs of haemopoiesis (blood forming).

6. It is one or the important organs of mineral homeostasis (reserve of calcium,

phosphate, and other ions).

7. It acts as an organ of poisonous heavy metal deposition.8. Defense against acidosis.

Skeleton: It is the framework of animal body formed by hard tissues (substances). Thehard substances are enamel, bones, chitin, hard skin derivatives, calcaneous shell etc.

Classification of Skeleton: The skeleton is classified on the basis of location of the

substances.I. Exo-skeleton: The subdivision of the skeleton, which is located out-side (external to)

the animal body ( e.g., shield of the turtle, scales of fishes, chitinous covering of the

cockroach, horns, hooves, nails, claws, dewclaws etc., in mammals.

II. Endo-skeleton: The subdivision of the skeleton, which is located in-side (internal

to) the animal body.

Subdivisions of endo-skeleton:

1. Visceral skeleton: The subdivision of the endo-skeleton that is embedded into the

organs. It is generally not the part of the function skeleton of the animal body.

Examples:a. Os Os-cordis The bone in the heart of cattle and buffalo.

b. Os-phrenic: the bone in the diaphragm of camel

c. Os-rostrum: The bone in the snout (nose) of pigs

d. Os-penis: The bone in the penis of dogs, bear, rodents, bats and some primates.


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2. Axial Skeleton: The subdivision of the endo-skeleton that is located at the median

plane of the body. The sub divisions of the axial skeleton are:

i. Skull (skeleton of head)

ii. Vertebral column

iii. Sternum andiv. Ribs

3. Appendicular skeleton: The subdivision of the endo-skeleton that is located awayfrom the long axis of the body. The subdivisions of appendicular skeleton are:

i. Forelimbs (Pectoral limbs): It is the subdivision of the appendicularskeleton, which is located nearer to the head.

ii. Hind limbs (Pelvic limbs): It is the subdivision of the appendicular skeletonthat is located nearer to the tail.

Table 1: Regions, Joints and Bones of the Forelimbs

Name of region Bone(s) Name of Joints Bones

Shoulder (Pectoral or

shoulder gordle)

Scapula ( all species)

Coracoid (fowl, man)

Clavicle (fowl,man)

Synsarcosis 1. scapula

2. Thorax

Arm (brachium) Humerus Shoulder (scapulo-

humeral joint)

1.Scapula

2. Humerus

Forearm(anebrachium) Radius

Ulna

Elbow 1. Humerus

2. Radius

3. Ulna

Manus

1. Carpal (knee)2. Cannon3. Digits

Carpal bones

Metacarpal bones

1. Phalanges (Ist, IIndand IIIrd)

2. Sesamoids (proximaland distal)

Carpal 1.Radius

2. Ulna

3. Carpals

4. Metacarpals

Fetlock 1.Metacarpals

2. First phalanx

3. Proxinal sesamoids

Pastern 1. First phalanx

2. Second phalanx

Coffin 1. Second phalanx

2. Third phalanx3. Distal sesamoids

The distal sesamoid bone in horse is known as navicular bone


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Table 2a: Regions, Joints and Bones of the Hind limbs

Name of region Bone(s) Name of Joints Bones

Hip (Pelvic gidle) Os coxae (ilium, ischium and

pubis)

Sacro-iliac 1. Sacrum

2. Ilium

Thigh 1. Femur2. Fabella (dog)

Symphysis pelvis 1.Between two pubisand ischium

Leg 1. Patella, 2. Tibia and

3. fibula

Hip 1. Os coxae

2. Femur

Pes

1. Tarsal (Hock)

2. Shank

3.Digits

1. Tarsal bones

2. Metatarsal bones

3. Phalanges (Ist, IInd and

IIIrd)

4. Sesamoids (proximal and

distal)

Stifle 1.Femur

2. Patella

3. Tibia

Tarsal (Hock) 1. Tibia

2. fibula

3. Tarsals4. Metatarsals

Fetlock 1.Metataraals

2. First phalanx

3. Proxinal sesamoids

Pastern 1. First phalanx

2. Second phalanx

Coffin 1. Second phalanx

2. Third phalanx

3. Distal sesamoids

Table 2b: Comparison of Pectoral and Pelvic bones

Pectoral limb

Pectoral girdle (shoulder girdle)

Scapula

ClavicleCoracoid

Humerus-arm

Pelvic limb

Pelvic girdle (os coxae)-pelvis

Ilium

IshiumPubis

Femur- thigh

Radius- forearmUlna- forearm

Carpus-

Metacarpus- cannonPhalanges- digits

Patella

Tibia- legFibula- leg

Tarsus- hock (shank)

Metatarsus- cannonPhalanges- digits


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Regions of Axial skeleton

1. Skull: It is the skeleton of head. The subdivisions are: i. Cranium and ii. Face. Thecranium is the subdivision of skull, which lodges the brain and its associated structures.

The remaining region is known as face.

Table 3: The bones of cranium Table 4: The bones of face.

2. Vertebral column: The subdivision of axial skeleton, which lodges the spinal cord

and its associated structures. The bones of vertebral column are called as vertebrae.Table 5: Regions and Bones of the vertebral column.

Region Bones (with abbreviation)

1. Neck Cervical vertebrae (C)

2. Back Thoracic vertebrae (Th)

3. Loin Lumbar vertebrae (L)

4. Rump (croup) Sacral vertebrae (S)

5. Tail Coccygeal vertebrae (Cy)

The number of bones is constant in a particular region of an animal. The expression of

the number of vertebrae in different regions, in a compact form, is known as vertebral

formula.Table 6: The vertebral formula in different animals

3. Ribs (Costae): They are the bones of lateral wall of thorax. The number of ribs (in

pairs) is always equal to the number of thoracic vertebrae.4. Sternum: It forms the floor of the thorax. The bones of sternum are called as

sternebrae. The number of sternebrae varies with species as follows:

Ox = 7; Horse = 8; Sheep = 6; Goat = 7 and Pig = 6.

Unpaired bones Paired bones

1. Hoid

2. Mandible

3. Vomer

1. Lacrimal

2. Maxilla

3. Nasal

4. Palatine5. Premaxilla

6. Turbinates (Conchae)

7. zygomatic (Malar)

Unpaired bones Paired bones

1. Ethmoid

2. Occipital

3. Sphenoid

1. Frontal

2. Interparietal

3. Parietal4. Temporal

Species (animal) Vertebral formula

Ox C7 Th13 L5 S6 Cy18-20

Horse C7 Th18 L5 S6 Cy15-21Sheep C7 Th13-14 L6-7 S4 Cy16-18

Dog C7 Th13 L7 S3 Cy20-23Fowl C14 Th7 (L + S)14 Cy6

Rabbit C7 Th12 L7 S4 Cy16Pig C7 Th14-15 L6-7 S4 Cy20-23

Human being C7 Th12 L5 S5 Cy4


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Number of bones present in different skeletons:

Animal Skull Vertebral

column

Ribs &

sternum

Fore

limb

Hind

limb

Visceral

bone

Total

(approx.)

Ox 32 51 26+1+0 24X2 24X2 2

(os cordis)

208

Horse 32 51 36+1+0 20X2 20X2 - 200

Dog 32 51 26+1+2 44X2 45X2 1

(os penis)

291

Pig 30 52 28-30+1+0 40X2 40X2 1

(os rostri)

274

Rabbit 34 46 24-26+1+0 31X2(excl.

sesamoids)

29X2 - 229

Fowl 40 41 14+1+1+2 13X2

(coracoid)

21X2 2 (os -

sclerae)

169

Figure 1: Skeleton of ox (above) and horse (below)


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Exercise 1: Write the name of bones (region) and joints in the above figure.


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Exercise 2: Write the name of bones (region) and joints in the above figure.

Types of Bone Tissue

Bone cells are called osteocytes, and the matrix of the bone is made of calciumsalts and collagen. The calcium salts give bones the strength for its supportive andprotective functions. The function of osteocytes is to regulate the amount of calcium that

is deposited in or removed from the bone matrix.

Bone is an organ; it has its own blood supply and is made up of two types oftissue: compact and spongy bone. The names imply that the two types of differ in density,

or how tightly the tissue is packed together. There are three types of cells that contribute

to bone homeostasis. Osteoblasts are bone-forming cell, osteoclasts reabsorb or breakdown bone, and osteocytes are mature bone cells. An equilibrium between osteoblasts

and osteoclasts maintains bone tissue.

Structure of Bone

A. Gross (Macroscopic) Structure of Long bone:

The arrangement of compact and spongy tissue in long bone accounts for itsstrength. Long bones contain sites of growth and reshaping and structures associated with

joints. The bone is relatively (almost) cylindrical in shape. The parts of a long bone

include the following (Fig 2and 3):


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1. Diaphysis: The middle part of the bone is known as diaphysis (dia = through and

physis = growth) or shaft. Internally it is hollow and the hollow part is called asmedullary cavity. The diaphysis is mainly formed by the hard bone known as cortical

bone (compact bone) and spongy bones.

2. Medullary cavity: The medullary cavity is filled with marrow (bone marrow which

synthesizes blood and blood cells). The bone marrow is red in young animals andbecomes yellow in adult animals and white in old animals due to deposition of fat.

3. Periosteum: The cortical bone is covered by a fibrous membrane called as periosteum,

which is responsible for the lateral growth (increase in diameter). The periosteum isabsent at the articular surface of the bone.

The periosteum consists of an inner osteogenic (bone forming) layer (cambium),

which provides appositional growth before maturity, and an outer fibrous layer, which is

purely supportive. The presence of the active cambium, with longitudinal arterioles,makes the periosteum thick. However, for the mature long-bone the cambium is atrophic

(thin and tenuous). The periosteum protects the bone, serves as a point of attachment for

muscle, and contains blood vessels that nourish the underlying bone. Because the

periosteum carries the blood supply to the underlying bone, any injury to this structurehas serious consequences to the health of the bone. Like any other organ the loss of blood

supply can cause its death.The inner surface of the cortical bone is lined by a fibrous membrane called as

endosteum.

4. Epiphysis: The enlarged ends of the long bone are the epiphyses. The epiphyses of a

bone articulate, or meet, with a second bone at a joint. Each epiphysis consists of spongy(trabecular) bones and a thin layer of compact bone overlying the spongy bones. The

spongy bones enclose small cavities called as marrow spaces, which are filled with bone

marrow. The epiphyses are covered by cartilage.5. Metaphysis: It is present between the diaphysis and epiphysis and has a hayline

cartilage known as epiphyseal cartilage. The epiphyseal cartilage is responsible for the

longitudinal growth of the bone.External mechanical forces importantly determine the shape of the epiphysis during development,

and drive bone morphology to a physiological geometry. These external forces may arise from muscle

contractions as well as from tensile forces which develop during growth due to stretching of tendons,

ligaments, periosteum and perichondrium.

6. Articular cartilage- The articular cartilage is found on the outer surface of the epiphysis. It forms a

smooth, shiny surface that decreases friction within a joint. Because a joint is also called an articulation,

this cartilage is called articular cartilage.


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Figure 2: Spongy (cancellous or trabecular) bones at the extremity of the long bone.Figure 1: Epiphysis showing spongy (trabecular) bones


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Figure 3: Long bone showing diaphysis with medullary cavity, metaphyses and

epiphyses.


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Microscopic Structure of Compact Bone:

Mature compact bone is composed of three lamellar (layer) arrangements(Figure 3 and 4):

I. Osteons (Haversian Systems) or osteonal bones

II. Circumferential SystemsIII. Interstitial Systems

The last two lamellar systems form the periosteonal (periosteal) bones.

Osteons (Haversian Systems)

The osteonal bone consists of osteons made up of thin (26 m) lamellar sheets(haversian lamellae 24 in number) oriented in a concentric cylindrical structure around

a central canal called the osteonic (haversian) canal (Fig.3 and 4). These osteons are 150250 m in diameter and align parallel along the long axis of bone. Between the rings of

matrix, the bone cells (osteocytes) are located in spaces called lacunae. Small channels(canaliculi) radiate from the lacunae to the osteonic (haversian) canal to provide

passageways through the hard matrix. In compact bone, the haversian systems are packedtightly together to form what appears to be a solid mass. The osteonic canals contain

blood vessels that are parallel to the long axis of the bone. These blood vesselsinterconnect, by way of perforating canals, with vessels on the surface of the bone, are

known as Volkmanns canals. Volkmann's canals can be identified as they do not

have concentric lamella surrounding them.

Circumferential SystemsImmediately below the periosteum, at the periphery of compact bone of the

diaphysis, the lamellae surround the bone in a continuous manner and are parallel to the

bone surface. These are known as the outer circumferential lamellae. A similar system

of continuous lamellae adjacent to the endosteum is also found and is known as the innercircumferential lamellae. They are made up of fibrolamellar bone. Bundles of collagen

fibers, known as Sharpeys fibers or perforating fibers, anchor the periosteum to the

outer circumferential lamellae, especially in sites of tendon insertions.

Interstitial SystemsRemodeling of bone is a continuous process involving resorption of osteons and

the rebuilding of new osteons. Interstitial systems of compact bone represent theremnants of osteons after remodeling. They are present between regular osteons and can

be identified as irregular lamellar structures that lack a central Haversian canal.

The periosteal bone is stronger and more highly anisotropic than osteonal bone.


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Figure 4: Compact bone showing osteon in different views. Right figure shows T.S. of

compact bone.


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Figure 4: Compact bone showing osteon in T.S. view

Figure 5: Compact bone showing osteon in different views.


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Spongy (cancellous or trabecular (L. trabs- beam) bone:Spongy bone is lighter and less dense than compact. Spongy bone consists of

plates (trabeculae) and bars of bone adjacent to small, irregular cavities that contain red

bone marrow (Figure 1). The canaliculi connect to the adjacent cavities, instead of a

central haversian canal, to receive their blood supply. It may appear that the trabeculaeare arranged in a haphazard manner, but they are organized to provide maximum strength

similar to braces that are used to support a building. The trabeculae of spongy bone

follow the lines of stress and can realign if the direction of stress changes.

Properties of Bones

I. Cortical bone:

1. Physical properties: It is a white or yellowish white hard structure. The

biomechanical properties are given in Table-3. The bones are strongest under

compressive stress and the weakest under shear stress. The Youngs modulus of osteonlamellar bone is about 22 GPa. Completely demineralized bone has mechanical properties

similar to the cranial cruciate ligament of stifle joint and, therefore, has increased

likelihood for success in the cranial cruciate ligament reconstruction surgery.

Table 7: Hydrated density, Youngs modulus, compressive strength and compressivestrength. Weibull modulus (m) for untreated, deproteinized and demineralized bovine

cortical bone in the three anatomical directions.

Sample Orientation Density

(g /cm3)

Youngs

modulus

(GPa)

Average

compressive

strength(MPa)

Weibull

moduli

(m)

UNTREATED

LongitudinalRadial

Transverse

DEPROTEINIZEDLongitudinalRadial

Transverse

DEMINERALIZEDLongitudinal

Radial

Ttransverse

2.062.03

2.04

2.001.94

1.96

1.17

1.17

1.18

22.612.4

16.2

9.2

2.62.2

0.232

0.060

0.132

120142

112

2418

11

14

6

11

3.324.22

5.68

2.042.32

2.95

N/A

N/A

N/A

The elastic modulusE= 6.95 1.49

Where = apparent density (g / cm3)


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II. Mechanical properties of spongy bone:

Average shear strengths in the range of 5-7 Mpa.Ave. shear modulus = 58-89 MPa

Compression modulus = 158-378 MPa

Shear strength is proportional to apparent density to the exponent 1.65. The mean

shear strength is 6.60 1.66 MPa. Bone marrow dose not have any effect on trabecularbone shear modulus and strength.

The shear strength is directly proportional to the apparent density raised to the

1.02 power and to the strain rate raised to the 0.13 power. The shear modulus is directlyproportional to the apparent density raised to the 1.08 power and to the strain rate raised

to the 0.07 power.

Elastic modulusE= 3790 - 0:06

3app

where is the strain rate, and app is the apparent density.

The average ultimate strength in tension is 7.6 2.2 MPa and in compression is 12.4

3.2 MPa.

Chemical properties:

The bone matrix (ground substance) has two main components:

1. Organic matrix2. Inorganic salts.The ratio between organic and inorganic matrix is about 1:2.

Organic matrixThe organic matrix is composed oftype I collagen fibers (about 95%) embedded

in an amorphous ground substance consisting of:

i. Sulfated glycosaminoglycans (chondroitin-4-sulfate, chondroitin-6-sulfate,keratan sulfate)

ii. Various bone proteins (bone sialoprotein, osteocalcin).The non-cellular organic matrix is known as osteoid. The osteoid makes up 1/3 of

the matrix. Collagen is a fibrous protein which provides the bone with tensile strengthand flexibility. The boiling of bone yields gelatin solution

Inorganic saltsThe inorganic components make up 2/3 of the bone matrix. The main calcium

deposits in the bone matrix are in the form of crystals of hydroxyapatiteCa10(PO4)6.(OH)2 with impurities like calcium and magnesium carbonates, calcium

fluoride, calcium hydroxide and citrate. Water comprises approximately 25% of adultbone mass.

Table 8: Chemical composition of dry cortical bone.

Chemical composition Percentage in dry cortical bone

Organic matrix 33

Inorganic matrix

Calcium phosphateCalcium carbonate

Magnesium phosphate

Magnesium carbonateSodium carbonate and chloride

67

574

2.

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Classification of Bones:

I. On the basis of compactness:

1. Cortical bones (Compact bones) and 2. Spongy bones (cancellous ortrabecular bones)II. On the basis of development (ossification processes):

1. Intramembranous bone: The bones are formed by the process ofintramembranous ossification. Examples are most of the bones of skull (except

mandible, basi-sphenoid and occipital condyles).

2. Intracartilagenous bone (Endo-chondral bones): The bones are formed by theprocess of intracartilageous ossification. Examples are bones of limbs, vertebrae,ribs, sternum, mandible, basi-sphenoid and occipital condyles.

III. On the basis of physical characters like presence of medullary cavity, shape and

size and location:1. Long bones: These bones have a cylindrical shaft (diaphysis) and two expanded

extremities (epiphysis). The shaft has a medullary cavity inside. Examples arehumerus, radius, ulna, femur, tibia, fibula, metacarpal bones, metatarsal bones and

phalanges

Functions: Mainly support the body weight and act as lever for locomotion.

2. Short bones: They are cuboidal (suffix oid means similar to) in shape. They aremainly composed of the spongy bone, which is covered by a thin layer of compact

bone. The medullary cavity is absent. They are generally located at the composite

joints. Examples are carpal and tarsal bones.Functions: They act as shock absorber to dissipate concussion during locomotion.

3. Flat bones: They are plate like and are more expanded in two dimensions (height

or thickness is very less). They are mainly composed of the spongy bone, which is

covered by a thick layer of compact bone. The medullary cavity is absent. The spongysubstance of flat bones of skull is called as diploe and the layers of compact bones are

called as lamina externa and lamina interna. Examples are scapula, os coxae, and

intramembranous bones of skull.Functions: Protection of vital organs and provide attachment to muscles and tendons

and ligaments of the joints.

4. Irregular bones: They are unpaired, irregular in shape and are located at themedian plane of the body. Examples: Vertebrae and Sternum.

Functions: Same as those of flat bones.

5. Pneumatic bones: Those bones, which have an air-cavity (sinus) inside the

compact bones instead of spongy bone and marrow. For this they are directly orindirectly connected with the air sacs of the respiratory system.. The pneumatic bones

are generally present in birds. Examples are bones of forelimbs of fowl (scapula,

clavicle, , coracoids, humerus radius, ulna, carpal and metacarpal bones and sternum.

Functions: They reduce the body weight and help in flight.6. Elongated bones: They are elongated in one dimension and do not contain

medullary cavity. Examples are ribs.


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Functions: Same as those of flat bones

7. Aborted long bones: They are reduced developed bones with a small medullarycavity. Examples are ulna of horse, small metacarpus and small metatarsus.

Functions: Same as those of long bones.

8. Sesamoid bones: The bones, which are developed along the course of the tendon

of a muscle to change the angle of pull of the muscle are known as sesamoid bones astheir shape is sesame-seed like. Examples are patella (the largest sesamoid bone),

fabella, Proximal and distal sesamoid bones of digits.

Functions: To change the angle of pull of the muscle.


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Development (ossification) of Bones

The process of bone formation is known as Ossification. There are two types

of ossifications:

1. Intracartilagenous (endochondral) ossification and

2. Intramembranous ossification

1. Intracartilagenous (endochondral) ossification:

The process of bone formation, which takes place in the cartilage, is called as

Intracartilagenous ossification

A. Formation of hyaline cartilage

Chondroblasts form a hyaline cartilage model of the future bone Once surrounded by cartilage matrix they change into chondrocytes Perichondrium is formed over the bone except where it will articulate Perichondrium is continuous with the joint capsule

B. Calcification of the cartilage

Blood vessels supply the perichondrium Osteoprogenitor cells from the perichondrium change to osteoblasts Osteoblasts produce a woven bone collar surrounded by periosteum Interstitial and appositional cartilage growth causes the cartilage model to

lengthen and broaden

Chondrocytes start to hypertrophy in the diaphysis


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The matrix between them is mineralized with calcium carbonate forming calcifiedcartilage

Chondrocytes trapped in their calcified tombs die leaving lacunae with thincalcified matrix walls

C. Primary ossification center forms

Blood vessels invade lacunae in the calcified cartilage Osteoclasts and osteoblasts travel into the calcified cartilage via the connective

tissue of blood vessels

Osteoblasts then produce bone trabeculae in diaphysis forming cancellous bone This part of the future bone is called the primary ossification center

D. Medullary cavity develops


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More growth of the cartilage model Bone collar thickens and lengthens Mature bone is produced from woven bone by remodeling Medullary cavity forms when osteoclasts remove bone from the diaphysis Bone marrow is produced in the newly formed medullary cavity

E. Secondary ossification centre is established

Secondary ossification centres are established in the epiphysis of long bones. These appear late in fetal development and a baby is considered to be full term if a

secondary ossification center has appeared at either the head of femur, head of

tibia, of head of humerus. The last to appear is the medial epiphysis of the clavical

which does not develop until 18 or 20 years

No Medullary cavity occurs in a secondary ossification centerF. Formation of compact bone

Cartilage is increasingly replaced by bone leaving only the epiphyseal growthplate which remains until the bone growth is complete.


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Articular cartilage remains throughout development and in adulthood on allarticular surfaces

G. The mature bone

Compact bone and cancellous bone are completely developed and the epiphysealgrowth plate has fused at completion of the bone growth, leaving just the

epiphyseal line

The only cartilage remaining is on the articular surfaces All of the perichondrium is now periosteum2. Intramembranous ossification

The process of bone formation, which takes place in the fibrous membrane, is

called as Intramembranous ossification. This process of bone formation is responsible forthe development of flat bones, especially those found in the skull. Unlike endochondral

ossification, cartilage is not involved or present in this process. The processes involvedare:

1. Formation of bone spicules,

2. Formation of bone trabeculae,3. Formation of woven bone and

4. Formation of lamellar bone

The first step in the process is the formation of bone spicules which eventually

fuse with each other and become trabeculae. The periosteum is formed and bone growth

continues at the surface of trabeculae. Much like spicules, the increasing growth of


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trabeculae result in interconnection and this network is called woven bone. Eventually,

woven bone is replaced by lamellar bone.

A. Formation of bone spicules and trabecular bones:

Embryologic mesenchymal cells (MSC) condense into layers of vascularized

primitive connective tissue. Certain mesenchymal cells group together, usually near oraround blood vessels, and differentiate into osteogenic cells which deposit bone matrix

constitutively. These aggregates of bony matrix are called bone spicules. Separate

mesenchymal cells differentiate into osteoblasts, which line up along the surface of thespicule and secrete more osteoid, which increases the size of the spicule.

B. Formation of woven and lamellar bones:

As the spicules continue to grow, they fuse with adjacent spicules and this results

in the formation of trabeculae. When osteoblasts become trapped in the matrix theysecrete, they differentiate into osteocytes. Osteoblasts continue to line up on the surface

which increases the size. As growth continues, trabeculae become interconnected and

woven bone is formed. The term primary spongiosa is also used to refer to the initial

trabecular network.

C. Primary centre of ossificationThe periosteum is formed around the trabeculae by differentiating mesenchymal

cells. The primary centre of ossification is the area where bone growth occurs between

the periosteum and the bone. Osteogenic cells that originate from the periosteum increase

appositional growth and a bone collar is formed. The bone collar is eventuallymineralized and lamellar bone is formed. The lamellar bones replace the woven bones.


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SYLLABUS


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Lecture-wise Course Distribution of Anatomy-I (VAN - 111)

(Osteology, Arthrology and Biomechanics)

(Bones and Joints of Forelimbs and Hind limbs)

THEORY

Course Teacher: Dr. Subhash C. Dubal Total Hours: 5 + 2+ 3 = 10

Lecture

No.

Topics Hours

1 Osteology: Introduction and Topographic Terms 1

2 Skeleton, Physical and Chemical Properties of Bones, Structure of

Bones and Classification of Bones

1

3 Bones of Forelimbs 2

4 Bones of Hind limbs 2

5 Arthrology: Introduction, Classification of Joints, Structure ofSynovial Joints and Joints of Forelimbs

1

6 Joints of Hind limbs 1

7 Biomechanics: Introduction and Biomechanics of Locomotion 2

8 Biomechanics of Deformation 1


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Lecture-wise Course Distribution of Anatomy-I (VAN - 111)

(Osteology, Arthrology and Biomechanics)

(Bones and Joints of Forelimbs and Hind limbs)

PRACTICALS

Course Teacher: Dr. Subhash C. Dubal Total Hours: 10 + 4 + 6 = 20

Practical

No.

Practicals Hours

1 Osteology: Introduction and Topographic Terms 2

2 Skeleton: Division of Skeleton and Bones, Regions and Joints

of Forelimbs

1

3 Bones, Regions and Joints of Hind limbs and Gross andMicroscopic Structure of Bone

1

4 Classification of Bones and Study of Scapula 1

5 Study of Humerus 1

6 Study of Radius and Ulna 1

7 Study of Pelvic Bone 3

8 Study of Femur 1

9 Study of Tibia, Fibula and Patella 2

10 Study of Carpals and Tarsals 1

11 Study of Metacarpals amd Metatarsals 1

12 Study of Bones of Digits 113 Arthrology: Joints of Forelimbs 3

14 Joints of Hind limbs 3

15 Biomechanics: Introduction and Biomechanics of Locomotion 4

16 Biomechanics of Deformation 2

Lecture Notes VAN-111 Scd

Documents

Transcript of Lecture Notes VAN-111 Scd