Anatomy Lecture 03 (General Anatomy)

Anatomy Lecture 03 (General Anatomy) Bone,Function of bone,Classification of bone,Parts of developing long bone,Blood supply,Nerve supply,Bone marrow,Ossification,X-rays

INTRODUCTION

• Bone
• Function of bone
• Classification of bone
• Parts of developing long bone
• Blood supply
• Nerve supply
• Bone marrow
• Ossification
• X-rays

BONE

• A living tissue capable of changing its structure as the result of stresses to which it is subjected
• Adult human body consist of 206 bones
• In a new born baby there are over 270 bones in body
• Branch deals with the study of bones is called osteology

COMPOSITION OF BONE

Bone consist of

• Cells
• Fibers
• Matrix

FUNCTIONS OF BONE

1. Characteristic form to the body – preservation of form
2. Support to human body – mechanical support
3. Protection to vital structures – skull, rib cage
4. Surface of attachments of various structures – tendons, muscles and ligaments.
5. Activity of erythropoises – it is blood forming organ
6. Transmission of sound waves – ossicles of middle ear from ear drum to middle ear
7. Stores Ca and phosphorus – storage organ
8. Maintain electrolyte balance – Ca and phosphate
9. Detoxification – lead, fluorine, arsenic, radium are removed from circulation and deposited in bones and teeth
10. Reticuloendothelial system – defensive system of body
11. Respiration – assist ribs
12. Speech – mandible, hyoid bone, bones of palate.

CLASSIFICATION OF BONE

• Developmental classification
• Structural classification
• Regional classification
• Classification according to size and shape

DEVELOPMENTAL CLASSIFICATION

• Intramembranous
• Intracartilaginous
• Membranocartilagenous

INTRAMEMBRANOUS

• Embryonic mesenchyme directly differentiates into bony tissue
• It occurs in embryo, when bones are urgently required for support and protection

Ø  Bones of vault and skull

Ø  Bones of face

Ø  Clavicle

INTRACARTILAGENOUS

First of all cartilagenous model is formed of bone which later on transforms into bony tissue

• All long bones except clavicle
• Short bones
• Irregular bones

MEMBRANO-CARTILAGENOUS

• At the junction of vault and base of skull the bones are formed by this method

STRUCTURAL CLASSIFICATION

• Compact bone
• Spongy/ Cancellous bone

COMPACT BONE

• Well developed Harversian lamellae or cylindrical lamellae are seen
• Appear as solid mass
• Lamellae consist of collagen fibers, lying in calcified materials

COMPACT BONE

• Adjacent lamellae are held together by interchange of fibers
• Bones cells lie scattered between the lamellae
• E.g., shafts of long bone

SPONGY BONE

• The lamellae are arranged flat
• No harversian system are seen
• E.g., ends of long bone

REGIONAL CLASSIFICATION

• Axial skeleton: 80 bones
• Appendicular skeleton: 126 bones

CLASSIFICATION ACCORDING TO SIZE AND SHAPE

There are five types of bones in the human body

• Long bones:

Found in limbs

Their length is greater then their breath

Have shaft-diaphysis and ends called as epiphysis

• Short bones:

found in hand and foot

They are roughly cuboidal in shape and are composed of cancellous bone.

• Flat bones are thin and generally curved, composed of thin inner and outer layers of compact bone separated by a layer of cancellous bone. e.g. skull bones.
• Sesamoid bones are small nodules of bone found in certain tendons where they rub over bony surfaces. e.g. the patella
• Irregular bones do not fit into the above categories. They consist of thin layers of compact bone surrounding a cancellous interior. e.g. skull, vertebrae and pelvic bones

PARTS OF DEVELOPING LONG BONE

There are 4 main parts of developing long bone:

• Diaphysis
• Epiphysis
• Epiphyseal cartilage
• Metaphysis

DIAPHYSIS

• It resemble the shaft of long bone
• Its ossification center appears in 7^th week of intrauterine life
• Ossification center is primary ossification center

EPIPHYSIS

• It resemble the ends of long bone
• Ossification center usually appears after birth at the age of one or two years
• Except the lower end of femur

EPIPHYSEAL CARTILAGE

• It is the plate of cartilaginous tissue present between epiphysis and diaphysis
• It is represented by epiphyseal line in adult bone

METAPHYSIS

• The actively growing part of shaft close to epiphyseal cartilage is metaphysis
• It is highly vascular
• It is responsible for growth in length

BLOOD SUPPLY OF LONG BONE

• Periosteal arteries
• Nutrient arteries
• Epiphyseal arteries
• Arteries at the end of long bone – periartecular anastomosis
• From the artery passing over that region

NERVE SUPPLY OF LONG BONE

• All bones are supplied by nerves
• They enter the bone through nutrient foramen and periosteum

NUTRIENT FORAMEN

• The nutrient foramen has direction against the growing end
• Towards the elbow we go; from the knee we flee e.g.,
• In humerus the nutrient foramen is directed towards the elbow and upper end of bone is the growing end

BONE MARROW

The marrow cavity is lined by endosteum and contains gelatinous material called bone marrow

Two types of bone marrow:

• Yellow bone marrow
• Red bone marrow

YELLOW BONE MARROW

• It is yellowish gelatinous fibro-fatty mass present in medullary cavity

RED BONE MARROW

It is red gelatinous mass consisting of haemopoietic tissue

It is engaged in erythropoiesis

It is found in:

• Ends of long bone
• Bodies of vertebrae
• Sternum
• Flat bones of skull

OSSIFICATION

The process of bone formation is called as ossification

• Intramembranous ossification
• Intracartilagenous ossification

INTRAMEMBRANOUS OSSIFICATION

• Embryonic mesenchyme directly differentiate into bony tissue.

INTRACARTILAGENOUS OSSIFICATION

• Cartilagenous model of bone is formed that is later on replaced by bony tissue

CENTERS OF OSSIFICATION

• Primary center – appear during fetal life
• Secondary center – appear after birth
• FACTORS AFFECTING BONE GROWTHMinerals – Ca, P etc
• Hormones – PTH, Calcitonin, Growth hormone
• Vitamins – Vit D, Vit C

RADIOGRAPHIC ANATOMY

• X-rays
• CT
• CAT
• MRI

X-RAYS

A tissue that is relatively dense absorbs more x-rays than tissues that are less dense.

• Radiopaque – very dense tissue.
• Radiolucent – less dense tissue.