Lecture Lecture The Department of Human anatomyThe Department of Human anatomy

The subject and substance of The subject and substance of anatomy, its significance for anatomy, its significance for

doctors. Methodological doctors. Methodological principles of anatomy. principles of anatomy.

Osteology (general data). Osteology (general data). Skeleton of a man, his Skeleton of a man, his

development and function. development and function. Classification, form and Classification, form and

structure of the bones, their structure of the bones, their chemical composition and chemical composition and

physical quality.physical quality.

PLANPLAN The subject of anatomy and its practical The subject of anatomy and its practical

importance for medicineimportance for medicine .. General information from the history of General information from the history of

anatomyanatomy .. Body types, kinds of anatomical studies, Body types, kinds of anatomical studies,

organization of the human body.organization of the human body. The anatomical position, planes of the bodyThe anatomical position, planes of the body.. Skeleton of manSkeleton of man.. Classification, form and structure of the Classification, form and structure of the

bones, their chemical composition and bones, their chemical composition and physical qualityphysical quality..

Human Anatomy is the science which studies the Human Anatomy is the science which studies the form and structure of the human body. form and structure of the human body.

The term “anatomy” is derived from the most The term “anatomy” is derived from the most ancient and major technique used by the ancient and major technique used by the anatomists of the past and present. The Greek anatomists of the past and present. The Greek word “anatemno” means ‘to dissect, to separate’. word “anatemno” means ‘to dissect, to separate’.

The term “morphology” encompasses sciences, The term “morphology” encompasses sciences, which study the form and structure of living which study the form and structure of living organism and includes anatomy, histology, organism and includes anatomy, histology, cytology and embryology.cytology and embryology.

Human anatomy has a very old and vast history. Human anatomy has a very old and vast history. Some of the most intelligent people the world Some of the most intelligent people the world

has ever seen had been the part of this has ever seen had been the part of this history. The overall history of human anatomy history. The overall history of human anatomy

can be divided into the following periodscan be divided into the following periodsI. ancient periodI. ancient period 1) Pre-scientific anatomy1) Pre-scientific anatomy (anatomy in ancient (anatomy in ancient

China, India, Egypt- near 2500-500 BC)China, India, Egypt- near 2500-500 BC) 2) Greek and Roman period:2) Greek and Roman period: 3) Medieval anatomy (4-13 centuries) 3) Medieval anatomy (4-13 centuries)

II. The scientific periodII. The scientific period 1) 14-19 century1) 14-19 century 2) Modern Anatomy (20-21 century)2) Modern Anatomy (20-21 century)

Greek period:Greek period:Greek period in the history of human anatomy started Greek period in the history of human anatomy started

somewhere near 400 BC. The most famous somewhere near 400 BC. The most famous anatomists of this period were Hippocrates and anatomists of this period were Hippocrates and Herophilus. Hippocrates was regarded as the father of Herophilus. Hippocrates was regarded as the father of medicine and he was one of the founders of anatomy.medicine and he was one of the founders of anatomy.

Herophilus is known as father of anatomy and he was one Herophilus is known as father of anatomy and he was one of the first very few people to dissect human body. of the first very few people to dissect human body. Herophilus did some great differentiations in the field Herophilus did some great differentiations in the field of anatomy for example he differentiated cerebrum of anatomy for example he differentiated cerebrum from cerebellum, nerves from tendons, arteries from from cerebellum, nerves from tendons, arteries from veins etc.veins etc.

Roman period:Roman period:The most prominent anatomist of this period was Galen. The most prominent anatomist of this period was Galen.

He is known as the “Prince of Physicians” because he He is known as the “Prince of Physicians” because he was the first experimental physiologist. His teachings was the first experimental physiologist. His teachings were followed for nearly 15 centuries considering them were followed for nearly 15 centuries considering them as infallible authorities of anatomy.as infallible authorities of anatomy.

II. The scientific periodII. The scientific period 1) 14-19 century1) 14-19 century

Fourteenth century:Fourteenth century: The most prominent scientist of this period was Mondino de Liuzzi. The most prominent scientist of this period was Mondino de Liuzzi.

He was an Italian and had the post of professor of anatomy in He was an Italian and had the post of professor of anatomy in Balogna. His famous book “Anthomia” was treated as the authorized Balogna. His famous book “Anthomia” was treated as the authorized anatomical text for over a century.anatomical text for over a century.

The reason his book became so famous was that he taught The reason his book became so famous was that he taught anatomy by dissection for which his book was a guide. Before the anatomy by dissection for which his book was a guide. Before the famous Vesalius, he was the most renowned anatomist.famous Vesalius, he was the most renowned anatomist.

Fifteenth century:Fifteenth century: This century is the time when one of the greatest geniuses of all This century is the time when one of the greatest geniuses of all

times Leonardo da Vinci lived. Da Vinci was the originator of cross times Leonardo da Vinci lived. Da Vinci was the originator of cross sectional anatomy. The most admirable and important work done by sectional anatomy. The most admirable and important work done by him in the field of anatomy was the collection of drawings of the him in the field of anatomy was the collection of drawings of the things he observed. These drawings were made with extreme things he observed. These drawings were made with extreme perfection. He made a total of 500 diagrams in his 60 notebooks.perfection. He made a total of 500 diagrams in his 60 notebooks.

Sixteenth century:Sixteenth century: This is the century of the greatest anatomist of all times, the famous Vesalius. This is the century of the greatest anatomist of all times, the famous Vesalius.

He is regarded as the “Founder of Modern Anatomy” because he made the He is regarded as the “Founder of Modern Anatomy” because he made the world realize that anatomy can only be taught through dissection. He world realize that anatomy can only be taught through dissection. He corrected the erroneous concepts of Galen and fought against his authority corrected the erroneous concepts of Galen and fought against his authority thus he corrected the concepts which were continuously taught wrong for thus he corrected the concepts which were continuously taught wrong for about 15 centuries.about 15 centuries.

Seventeenth century:Seventeenth century: In this century lived the famous English anatomist William Harvey. He In this century lived the famous English anatomist William Harvey. He

discovered the circulation of blood through human body and published in the discovered the circulation of blood through human body and published in the book titled “Anatomical exercise on the motion of blood and heart in animals:” book titled “Anatomical exercise on the motion of blood and heart in animals:” He also published a book on embryology.He also published a book on embryology.

Eighteenth and Nineteenth century:Eighteenth and Nineteenth century: In these two centuries major steps were taken in learning procedure for In these two centuries major steps were taken in learning procedure for

anatomy. Dissection was made compulsory for medical students. Warburton anatomy. Dissection was made compulsory for medical students. Warburton Anatomy Act was passed in England under which the unclaimed bodies were Anatomy Act was passed in England under which the unclaimed bodies were made available for dissection. The use of formalin as a fixative started in this made available for dissection. The use of formalin as a fixative started in this period and techniques of endoscopy were also discovered. Prominent period and techniques of endoscopy were also discovered. Prominent anatomists of this century included Cuvier, Meckel and Henry Gray (Author of anatomists of this century included Cuvier, Meckel and Henry Gray (Author of Gray’s Anatomy).Gray’s Anatomy).

2) Modern Anatomy (20-21 century)2) Modern Anatomy (20-21 century)

BODY TYPESBODY TYPES  No two human beings are built exactly alike, but we can group individuals No two human beings are built exactly alike, but we can group individuals

into three major categories. into three major categories. These groups represent basic body shapes.These groups represent basic body shapes.MORPH = body, body formMORPH = body, body formECTO = all energy is outgoingECTO = all energy is outgoingENDO = all energy is stored insideENDO = all energy is stored insideMESO = between, in the middleMESO = between, in the middleECTOMORPH = slim individualECTOMORPH = slim individualENDOMORPH = broad individualENDOMORPH = broad individualMESOMORPH = body type between the two others, “muscular” typeMESOMORPH = body type between the two others, “muscular” typeEctomorphs, slim persons, are more susceptible to lung infections. Ectomorphs, slim persons, are more susceptible to lung infections.

Endomorphs are more susceptible to heart disease.Endomorphs are more susceptible to heart disease.

KINDS OF ANATOMICAL STUDIESKINDS OF ANATOMICAL STUDIESMicroscopic anatomyMicroscopic anatomy is the study of structures that cannot be seen with  is the study of structures that cannot be seen with

the unaided eye. You need a microscope.the unaided eye. You need a microscope.Gross anatomyGross anatomy by systems is the study of organ systems, such as the  by systems is the study of organ systems, such as the

respiratory system or the digestive system.respiratory system or the digestive system.Gross anatomyGross anatomy  by regions considers anatomy in terms of regions such as by regions considers anatomy in terms of regions such as

the trunk, upper member, or lower member.the trunk, upper member, or lower member.NeuroanatomyNeuroanatomy studies the nervous system. studies the nervous system.Functional anatomyFunctional anatomy  is the study of relationships between functions and is the study of relationships between functions and

structures.structures.

ORGANIZATION OF THE HUMAN BODYORGANIZATION OF THE HUMAN BODY

The human body is organized into cells, tissues, organs, The human body is organized into cells, tissues, organs, organ systems, and the total organism.organ systems, and the total organism.

CellsCells are the smallest living unit of body construction. are the smallest living unit of body construction. A A tissuetissue is a grouping of like cells working together.  is a grouping of like cells working together.

Examples are muscle tissue and nervous tissue.Examples are muscle tissue and nervous tissue. An An organorgan is a structure composed of several different  is a structure composed of several different

tissues performing a particular function. Examples tissues performing a particular function. Examples include the lungs and the heart.include the lungs and the heart.

Organ systemsOrgan systems are groups of organs which together  are groups of organs which together perform an overall function. Examples are the perform an overall function. Examples are the respiratory system and the digestive system.respiratory system and the digestive system.

The total organismThe total organism is the individual human being. You  is the individual human being. You are a total organism.are a total organism.

THE ANATOMICAL POSITIONTHE ANATOMICAL POSITION

  The anatomical position is an The anatomical position is an artificial posture of the human artificial posture of the human body. This position is used as a body. This position is used as a standard reference throughout the standard reference throughout the medical profession.medical profession.

. In the anatomical position, the body . In the anatomical position, the body stands erect, with heels together. stands erect, with heels together. Upper members are along the Upper members are along the sides, with the palms of the hands sides, with the palms of the hands facing forward. The head faces facing forward. The head faces forward.forward.

PLANES OF THE BODYPLANES OF THE BODY

SagittalSagittal planes are vertical planes  planes are vertical planes that pass through the body from that pass through the body from front to back. The median or front to back. The median or midsagittal plane is the vertical midsagittal plane is the vertical plane that divides the body into plane that divides the body into right and left halves.right and left halves.

HorizontalHorizontal (transverse) planes are  (transverse) planes are parallel to the floor. They are parallel to the floor. They are perpendicular to both the sagittal perpendicular to both the sagittal and frontal planes.and frontal planes.

FrontalFrontal (coronal) planes are vertical  (coronal) planes are vertical planes which pass through the planes which pass through the body from side to side. They are body from side to side. They are perpendicular to the sagittal perpendicular to the sagittal plane.plane.

Anatomical terms for describing Anatomical terms for describing relations:relations: AnteriorAnterior means towards the  means towards the

front.front. PosteriorPosterior means towards the  means towards the

back.back. SuperiorSuperior means towards the  means towards the

head.head. InferiorInferior means towards the feet. means towards the feet. MedialMedial means towards the  means towards the

median plane (near the middle of median plane (near the middle of the body).the body).

LateralLateral means away from the  means away from the median plane (away from the median plane (away from the middle of the body).middle of the body).

Proximal and distal are terms Proximal and distal are terms applied specifically to the applied specifically to the limbs. limbs. ProximalProximal means nearer to  means nearer to the shoulder joint or the hip the shoulder joint or the hip joint. joint. DistalDistal means further away  means further away from the shoulder joint or the hip from the shoulder joint or the hip joint. joint.

Skeletal systemSkeletal systemSkeletal system is the system of Skeletal system is the system of

bones, associated cartilages bones, associated cartilages and joints of human body. and joints of human body. Together these structures Together these structures form the human skeleton. form the human skeleton. Skeleton can be defined as Skeleton can be defined as the hard framework of human the hard framework of human body around which the entire body around which the entire body is built. Almost all the body is built. Almost all the hard parts of human body are hard parts of human body are components of human components of human skeletal system. skeletal system.

Divisions of Human Skeleton:Divisions of Human Skeleton:Human skeleton can be divided into two divisions.Human skeleton can be divided into two divisions. Axial Skeleton:Axial Skeleton: Appendicular Skeleton:Appendicular Skeleton:

Axial skeletonAxial skeleton forms the axis of human body. It consists of Skull, vertebral column and thoracic forms the axis of human body. It consists of Skull, vertebral column and thoracic cage.cage.

Skull:Skull: Skull is that part of human skeleton that forms the bony framework of the head. It consists  Skull is that part of human skeleton that forms the bony framework of the head. It consists of 22 different bones that are divided into two groups: bones of cranium and bones of face.of 22 different bones that are divided into two groups: bones of cranium and bones of face.

Vertebral Column:Vertebral Column: It is a flexible column of vertebrae, connecting the trunk of human body to  It is a flexible column of vertebrae, connecting the trunk of human body to the skull and appendages. It is composed of 33 vertebrae which are divided into 5 regions: the skull and appendages. It is composed of 33 vertebrae which are divided into 5 regions: Cervical, Thoracic, Lumbar, Sacral, and Coccygeal.Cervical, Thoracic, Lumbar, Sacral, and Coccygeal.

Rib Cage:Rib Cage: It is a bony cage enclosing vital human organs formed by the sternum and ribs.  It is a bony cage enclosing vital human organs formed by the sternum and ribs. There are 12 pairs of ribs that are divided into three groups: True ribs, False ribs, and There are 12 pairs of ribs that are divided into three groups: True ribs, False ribs, and Floating ribs.Floating ribs.

Appendicular Skeleton:Appendicular Skeleton:It is the skeleton of appendages of human body. It consists of Shoulder girdle, Skeleton of upper It is the skeleton of appendages of human body. It consists of Shoulder girdle, Skeleton of upper

limb, Pelvic girdle and Skeleton of lower limb.limb, Pelvic girdle and Skeleton of lower limb.Shoulder Girdle:Shoulder Girdle: It attaches the upper limb to body trunk and is formed by two bones: clavicle  It attaches the upper limb to body trunk and is formed by two bones: clavicle

and scapula.Clavicle is a modified long bone and is subcutaneous throughout its position. and scapula.Clavicle is a modified long bone and is subcutaneous throughout its position. Skeleton of Upper limb:Skeleton of Upper limb: The skeleton of each upper limb consists of 30 bones. These bones  The skeleton of each upper limb consists of 30 bones. These bones

are: Humerus, Ulna, Radius, Carpals (8), Metacarpals (5), Phalanges (14).are: Humerus, Ulna, Radius, Carpals (8), Metacarpals (5), Phalanges (14).Pelvic Girdle:Pelvic Girdle: There are two pelvic girdles (one for each lower limb) but unlike the pectoral  There are two pelvic girdles (one for each lower limb) but unlike the pectoral

girdles, they are jointed with each other at symphysis pubis. Each pelvic girdle is a single girdles, they are jointed with each other at symphysis pubis. Each pelvic girdle is a single bone in adults and is made up of three components: Ileum, Ischium and Pubis. bone in adults and is made up of three components: Ileum, Ischium and Pubis.

Skeleton of Lower limb:Skeleton of Lower limb: The skeleton of each lower limb consists of 30 bones. These bones  The skeleton of each lower limb consists of 30 bones. These bones are; Femur, Tibia, Patella, Tarsals (7), Metatarsals (5), Phalanges (14).are; Femur, Tibia, Patella, Tarsals (7), Metatarsals (5), Phalanges (14).

Functions of bones:Functions of bones:1) Mechanical Functions of bones:1) Mechanical Functions of bones: Protection:Protection:

At numerous places inside the body, bones serve to protect At numerous places inside the body, bones serve to protect important and delicate organs. The best examples to be important and delicate organs. The best examples to be quoted here are those of brain (which is protected by the quoted here are those of brain (which is protected by the skull) and heart (which is protected by the ribcage).skull) and heart (which is protected by the ribcage).

Shape:Shape:Because of their rigid nature, bones provide a framework Because of their rigid nature, bones provide a framework around which the body is built. So bones are responsible for around which the body is built. So bones are responsible for the shape and form of human body.the shape and form of human body.

Movement:Movement:Working with skeletal muscles, tendons, ligaments and Working with skeletal muscles, tendons, ligaments and joints, the bones form the moving machinery of human body. joints, the bones form the moving machinery of human body. The major role of bones in movement is that they act as The major role of bones in movement is that they act as levers, which make use of the forces generated by skeletal levers, which make use of the forces generated by skeletal muscles in a beneficial way.muscles in a beneficial way.

2) 2) Synthetic Functions of Bones:Synthetic Functions of Bones: Synthesis of blood cells:Synthesis of blood cells:

The major synthetic role of bones is to produce blood cells. The The major synthetic role of bones is to produce blood cells. The bones themselves are not capable of doing this. Instead, they house bones themselves are not capable of doing this. Instead, they house the bone marrow, which containsHematopoietic stem cells, capable the bone marrow, which containsHematopoietic stem cells, capable of producing blood cells. In infants, bone marrow of all long bones of producing blood cells. In infants, bone marrow of all long bones is capable of this synthesis, however, as a person gets older, the red is capable of this synthesis, however, as a person gets older, the red marrow turns into yellow fatty marrow, which is no more capable of marrow turns into yellow fatty marrow, which is no more capable of hematopoiesis. The red marrow in adults and older individuals is hematopoiesis. The red marrow in adults and older individuals is restricted to vertebrae and heads of tibia and femur.restricted to vertebrae and heads of tibia and femur.

3) 3) Metabolic Functions of Bones:Metabolic Functions of Bones: Mineral Storage:Mineral Storage:

Bones serve as an important store house of minerals such as Bones serve as an important store house of minerals such as calcium and phosphorus.calcium and phosphorus.

Fat storage:Fat storage:The yellow bone marrow of long bones act as a storage of fats.The yellow bone marrow of long bones act as a storage of fats.

Role in acid-base balance:Role in acid-base balance:Bone buffers the blood against excessive pH changes by absorbing Bone buffers the blood against excessive pH changes by absorbing or releasing alkaline saltsor releasing alkaline salts

Bone is a dense type of connective Bone is a dense type of connective tissue impregnated with inorganic salts mainly tissue impregnated with inorganic salts mainly the salts of calcium such as calcium phosphate, the salts of calcium such as calcium phosphate, calcium carbonate etc. The organic portion of the calcium carbonate etc. The organic portion of the bone constitutes one third (1/3) and the inorganic bone constitutes one third (1/3) and the inorganic salt component constitutes two third (2/3). The salt component constitutes two third (2/3). The inorganic salts are mainly responsible for rigidity inorganic salts are mainly responsible for rigidity and hardness, which make bone resist and hardness, which make bone resist compression caused by the forces of weight and compression caused by the forces of weight and impact. The organic connective tissue portion of impact. The organic connective tissue portion of the bone makes it resilient and thus the bone can the bone makes it resilient and thus the bone can afford resistance to tensile forces. In strength afford resistance to tensile forces. In strength bone is comparable to iron and steel.bone is comparable to iron and steel.

ClassificationClassification

Types on the basis of shape:Types on the basis of shape: Long bones,Long bones, Short bones,Short bones, Flat bones,Flat bones, Irregular bones,Irregular bones, Pneumatic bones,Pneumatic bones, Sesamoid bonesSesamoid bones

Types on the basis of Types on the basis of development:development:

Membranous bones,Membranous bones, Cartilaginous bones,Cartilaginous bones, Membro-cartilaginous bonesMembro-cartilaginous bones

Types on the basis of region:Types on the basis of region: Bones of axial skeleton,Bones of axial skeleton, Bones of appendicular Bones of appendicular

skeletonskeleton

Types on the basis of Types on the basis of structure:structure:

According to Macroscopic According to Macroscopic approach;approach;

Compact bone,Compact bone, spongy bonespongy boneAccording to Microscopic According to Microscopic

approach:approach: Fibrous bone,Fibrous bone, Lamellar boneLamellar bone

Long bones:Long bones:

These bones typically have an These bones typically have an elongated shaft and two elongated shaft and two expanded ends one on either expanded ends one on either side of the shaft. The shaft is side of the shaft. The shaft is known as known as diaphysisdiaphysis and the ends and the ends are called are called epiphysesepiphyses. Normally . Normally the epiphyses are smooth and the epiphyses are smooth and articular. articular. MetaphysisMetaphysis is a portion is a portion of the bone between epiphyses of the bone between epiphyses and diaphysis.During bone and diaphysis.During bone growth the growth the metaphyseal platemetaphyseal plate is is responsible for the longitudinal responsible for the longitudinal growth of the bone. growth of the bone. ApophysisApophysis is is a bony process near epiphysis, a bony process near epiphysis, which contains separate which contains separate ossification center. The shaft ossification center. The shaft (diaphysis) has a central (diaphysis) has a central medullary cavity where lies the medullary cavity where lies the bone marrow. bone marrow.

Parts of the long bone 1. Epiphysis(epiphysis).

2. Apophysis(apophysis).3. Metaphysis (metaphysis).

4. Diaphysis (diaphysis).

Long bones are further divided into three categories that are;Long bones are further divided into three categories that are; Typical long bones:Typical long bones: They have an elongated shaft and two ends and are  They have an elongated shaft and two ends and are

represented by bones such as humerus, femur, radius, ulna, tibia and fibula.represented by bones such as humerus, femur, radius, ulna, tibia and fibula. Miniature long bones:Miniature long bones: As the name indicates, these bones have a miniature  As the name indicates, these bones have a miniature

appearance and often they have only one epiphysis. Examples of this class of appearance and often they have only one epiphysis. Examples of this class of long bones are metacarpals, metatarsals and phalanges of both upper and long bones are metacarpals, metatarsals and phalanges of both upper and lower limb.lower limb.

Modified long bones:Modified long bones: These bones either have modified shaft or ends. They  These bones either have modified shaft or ends. They have no medullary cavity which is present in the typical long bones. Examples have no medullary cavity which is present in the typical long bones. Examples of this class of bones are clavicle and body of vertebrae.of this class of bones are clavicle and body of vertebrae.

Short bones:Short bones:These bones are short in posture and can be of any shape. Most of These bones are short in posture and can be of any shape. Most of them are named according to their shape. Examples of this class of them are named according to their shape. Examples of this class of bones include cuboid, cuneiform, scaphoid, trapezoid etc. In fact all bones include cuboid, cuneiform, scaphoid, trapezoid etc. In fact all the carpal and tarsal bones are included in this category.the carpal and tarsal bones are included in this category.

Flat bones:Flat bones:These bones are flat in These bones are flat in appearance and have appearance and have two prominent two prominent surfaces. They surfaces. They resemble shallow resemble shallow plates and form plates and form boundaries of certain boundaries of certain body cavities. body cavities. Examples include Examples include scapula, ribs, sternum scapula, ribs, sternum etc.etc.

Irregular bones:Irregular bones:The shape of these The shape of these bones is completely bones is completely irregular and they do irregular and they do not fit into any not fit into any category of shape. category of shape. Examples of this type Examples of this type of bones are of bones are vertebrae, hip bone vertebrae, hip bone and bones in the and bones in the base of skull.base of skull.

Pneumatic bones:Pneumatic bones:

Pneumatic bones can also be Pneumatic bones can also be categorized under the irregular categorized under the irregular bones because they are also bones because they are also irregular in shape but since there is irregular in shape but since there is a difference between the two that is a difference between the two that is characteristically very important characteristically very important therefore they are often classified therefore they are often classified separately. The characteristic separately. The characteristic difference is the presence of large difference is the presence of large air spaces in these bones which air spaces in these bones which make them light in weight and thus make them light in weight and thus they form the major portion of skull they form the major portion of skull in the form of sphenoid, frontal, in the form of sphenoid, frontal, ethmoid and maxilla. Besides ethmoid and maxilla. Besides making the skull light in weight they making the skull light in weight they also help in resonance of sound and also help in resonance of sound and as air conditioning chambers for the as air conditioning chambers for the inspired air.inspired air.

Sesamoid bones:Sesamoid bones:These are not like the other These are not like the other types of bones because types of bones because they are in the form of they are in the form of nodules embedded in nodules embedded in tendons and joint capsules. tendons and joint capsules. They do not possess any They do not possess any periosteum and their periosteum and their ossification also takes ossification also takes place after birth. Examples place after birth. Examples of this type of bones are of this type of bones are patella, pisiform.patella, pisiform.

Types of bone on the basis of Types of bone on the basis of development:development:

Membranous bones: Membranous bones: These are also known as dermal bones and the process by which These are also known as dermal bones and the process by which they ossify is called intra-membranous ossification. These bones they ossify is called intra-membranous ossification. These bones ossify from mesenchymal condensations in the intrauterine life. ossify from mesenchymal condensations in the intrauterine life. Examples are bones of the skull and facial bones.Examples are bones of the skull and facial bones.

Cartilaginous bones: Cartilaginous bones: These bones ossify from a cartilage model and this type of These bones ossify from a cartilage model and this type of ossification is known as intra-cartilaginous ossification. These bones ossification is known as intra-cartilaginous ossification. These bones do not form from mesenchymal condensations but from preformed do not form from mesenchymal condensations but from preformed cartilage models. Examples of this type of bones include bones of cartilage models. Examples of this type of bones include bones of limbs, vertebral column and thoracic cage.limbs, vertebral column and thoracic cage.

Membrocartilaginous bones:Membrocartilaginous bones:These bones ossify partly from cartilage and partly from These bones ossify partly from cartilage and partly from mesenchymal condensations. Examples of this class of bones mesenchymal condensations. Examples of this class of bones include clavicle, mandible, occipital, temporal and sphenoid etc.include clavicle, mandible, occipital, temporal and sphenoid etc.

Types of bone on the basis of region:Types of bone on the basis of region:On the basis of region we have two types of On the basis of region we have two types of

bones that arebones that areBones of Bones of axial skeleton:axial skeleton:  

These bones form the axial skeleton of human These bones form the axial skeleton of human body. Examples are bones of skull, vertebral body. Examples are bones of skull, vertebral column and thoracic cage.column and thoracic cage.

Bones of Bones of appendicular skeleton:appendicular skeleton:  These bones form the appendicular skeleton of These bones form the appendicular skeleton of the body. Examples of this type of bones are the body. Examples of this type of bones are bones of the limbs and girdles of limbs.bones of the limbs and girdles of limbs.

Types of bone on the basis of structure:Types of bone on the basis of structure:Macroscopic approachMacroscopic approach divides the bones into two categories that are; divides the bones into two categories that are;

Compact bone:Compact bone:The part of a bone where bone substance to bone space ratio is a The part of a bone where bone substance to bone space ratio is a bigger quantity is called compact bone. This means that there is more bigger quantity is called compact bone. This means that there is more bone tissue and less empty space.bone tissue and less empty space.Spongy bone: Spongy bone: The part of a bone where bone substance to bone space ratio is a The part of a bone where bone substance to bone space ratio is a smaller quantity. This means that there is more empty space and less smaller quantity. This means that there is more empty space and less bone tissue.bone tissue.

Microscopic approachMicroscopic approach divides the bones into following  divides the bones into following categories;categories;

Lamellar bone:Lamellar bone:The type of bone which are composed of thin plates The type of bone which are composed of thin plates (lamellae) of bony tissue. Most mature human bones (lamellae) of bony tissue. Most mature human bones are lamellar bones.are lamellar bones.

Fibrous bone:Fibrous bone:These have more fibers in them. These have more fibers in them. In humans they are In humans they are found only in fetus.found only in fetus.

Besides osseous tissue, a living bone contains cartilage Besides osseous tissue, a living bone contains cartilage in the area of articular surfaces and connective tissue, in the area of articular surfaces and connective tissue, which covers the bone on the outside (periosteum), which covers the bone on the outside (periosteum), blood and lymph vessels and nerves.blood and lymph vessels and nerves.

Bone marrowBone marrow

The inside of the bone contains yellow and red bone The inside of the bone contains yellow and red bone marrow.marrow.

Red bone marrowRed bone marrow performs haemopoietic and immune performs haemopoietic and immune functions. In adults red bone marrow is located in functions. In adults red bone marrow is located in epiphyses of tubular bones as well as in the chambers epiphyses of tubular bones as well as in the chambers of spongy bones such as vertebrae, ribs, sternum, skull of spongy bones such as vertebrae, ribs, sternum, skull bones and alae of iliac bone.bones and alae of iliac bone.

Yellow bone marrowYellow bone marrow consists mainly of adipose tissue. consists mainly of adipose tissue. In adults it is located in bone marrow cavity of tubular In adults it is located in bone marrow cavity of tubular bones. During embrionic and fetal developmental bones. During embrionic and fetal developmental periods as well as newborns, bones contain exlusively periods as well as newborns, bones contain exlusively red bone marrow. red bone marrow.

OssificationOssificationOssification is the process by which bone is formed. The formation of bone Ossification is the process by which bone is formed. The formation of bone

is in fact conversion of other types of connective tissues into bone. is in fact conversion of other types of connective tissues into bone. Based on the type of tissue converted into bone, the process of Based on the type of tissue converted into bone, the process of ossification is of three types. ossification is of three types.

1) Intra-membranous ossification:1) Intra-membranous ossification:This type of ossification is also known as mesenchymal ossification. In this This type of ossification is also known as mesenchymal ossification. In this

type the bone is ossified from mesenchymal condensations. The bones type the bone is ossified from mesenchymal condensations. The bones formed by this process of ossification are known as membranous bones formed by this process of ossification are known as membranous bones or dermal bones.or dermal bones.

2) Intra-cartilaginous ossification:2) Intra-cartilaginous ossification:In this type of ossification, the mesenchyme has been converted to In this type of ossification, the mesenchyme has been converted to

cartilaginous models and the process of ossification starts in these cartilaginous models and the process of ossification starts in these cartilaginous models. The process of conversion of mesenchymal cartilaginous models. The process of conversion of mesenchymal condensations in cartilage is known as chondrification and this process condensations in cartilage is known as chondrification and this process takes place during the second month of intrauterine life. This indicates takes place during the second month of intrauterine life. This indicates that the bones which start ossifying before second month are membrane that the bones which start ossifying before second month are membrane bones and the bones which start ossifying after 2nd month of bones and the bones which start ossifying after 2nd month of intrauterine life are cartilaginous bones.intrauterine life are cartilaginous bones.

3) membro-cartilaginous3) membro-cartilaginous ossification:ossification:There is another type of ossification in which a bone partly ossifies from There is another type of ossification in which a bone partly ossifies from

membrane and partly from cartilage. These bones are known membrane and partly from cartilage. These bones are known as membro-cartilaginous bones.as membro-cartilaginous bones.

Process of ossification:Process of ossification:

With the explanation of different types of ossification in bones it is With the explanation of different types of ossification in bones it is also important to explain what ossification is. Ossification is the also important to explain what ossification is. Ossification is the process by which bone is formed. It is started at certain sites process by which bone is formed. It is started at certain sites known as centers of ossification each of which is a point where known as centers of ossification each of which is a point where lying down of lamellae (bone formation) is started by the activity lying down of lamellae (bone formation) is started by the activity of osteoblasts. Osteoblasts are bone forming cells and secrete of osteoblasts. Osteoblasts are bone forming cells and secrete collagen and other substances that form the ground substance of collagen and other substances that form the ground substance of bone. bone.

The centers of ossification may be primary or secondary. The The centers of ossification may be primary or secondary. The primary centers of ossification appear before birth and are the primary centers of ossification appear before birth and are the first to start the process of ossification. The secondary centers of first to start the process of ossification. The secondary centers of ossification mostly appear after birth but there are few exceptions ossification mostly appear after birth but there are few exceptions to this that is some secondary centers do appear before birth. to this that is some secondary centers do appear before birth. The secondary centers are sites where process of ossification The secondary centers are sites where process of ossification starts after it has started in primary centers.starts after it has started in primary centers.

Growth in length:Growth in length: A long bone grows in length by multiplication of cells in the epiphyseal A long bone grows in length by multiplication of cells in the epiphyseal

plate of cartilage. The cartilage cells divide and increase in number. plate of cartilage. The cartilage cells divide and increase in number. The zone of active division in the epiphyseal plate of cartilage lies The zone of active division in the epiphyseal plate of cartilage lies towards the epiphysis (end of the bone). This means that newly towards the epiphysis (end of the bone). This means that newly formed cartilage cells will push the older, larger cells towards the formed cartilage cells will push the older, larger cells towards the diaphysis (shaft of the bone).  Eventually these cartilage cells are diaphysis (shaft of the bone).  Eventually these cartilage cells are replaced by osteocytes (bone cells), thus increasing the length of the replaced by osteocytes (bone cells), thus increasing the length of the bone. It should be kept in mind that after puberty, when the epiphyseal bone. It should be kept in mind that after puberty, when the epiphyseal plate of cartilage no more exists, the growth in length of a bone stops plate of cartilage no more exists, the growth in length of a bone stops completely.completely.

Growth in thickness:Growth in thickness: A long bone grows in thickness by multiplication of cells in the deeper A long bone grows in thickness by multiplication of cells in the deeper

layer of periosteum. The cells lying in the deeper layer of periosteum layer of periosteum. The cells lying in the deeper layer of periosteum are known as osteoblasts (bone forming cells). These cells divide are known as osteoblasts (bone forming cells). These cells divide continuously and form the osteocytes, thus increase the thickness of continuously and form the osteocytes, thus increase the thickness of bone.bone.

Thank you for attention!Thank you for attention!