Dr. Sama ul Haque

Objectives
 Define Skeleton.
 What do you understand by the terms Axial and
Appendicular skeleton.
 Define bones with their constituents.
 Enumerate their functions.
 Define Cartilage.
 Give different types of cartilage with examples.
 Classify the bones on the following basis.
1.
Histological or Microscopically
2.
Gross Appearance or Macroscopically

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Define Ossification.
Describe developing parts of a typical long bone.
Give the arterial supply of a Mature long Bone.
What are different types of bone break.
Define terms used for describing Bony features.

 Epithelium
 Connective tissue
 Connective tissue proper
 Cartilage
 Bone
 Blood
 Muscle tissue
 Nervous tissue

Axial Skeleton
These bones lie around the longitudinal axis of the body.
 Skull (cranium and facial bones)
 Vertebral column (vertebrae and discs)
 Thoracic cage (ribs and sternum)
Function:
Axial skeleton supports and protects organs of head, neck and thorax.

Appendicular skeleton
 Pectoral or Shoulder girdle
(clavicles and scapulae)
 Upper limbs (arms)
 Pelvic girdle
(Hip bones, sacrum, coccyx)
 Lower limbs (legs)
Function:
1.
2.
Voluntary movements
Protection of delicate Structures

Composition of Bones
 Collagen: chief organic constituent (protein)
 Inorganic Calcium Salts: Vitamin D essential for absorption

A Chemical Analysis of Bone

 Osteoblasts : bone building, bone repairing cells in the periosteum and synthesize new matrix (Osteogenesis)
 Osteocytes : osteoblast embedded within the bone matrix (mature bone cells)
 Osteoclasts : cells that cause absorption of bone or dissolve bone matrix (Osteolysis)

Periosteum
 Dense, fibrous membrane covering bone
 Contains blood vessels
 Essential for bone cell survival and bone formation
Endosteum

 1- Shape
Functions of Bones
 2- Support
 3- Protection
=> Skull
=> Thoracic cage
=> Vertebral Column

Functions of Bones
 4- Movement
=> Muscles
=> Tendons
=> Ligaments
 5- Locomotion:
To provide a lever system against which muscles can pull.
 6- Weight Transmission

Functions of Bones
 7- Mineral Storage
=> Calcium
=> Phosphate
=> Results in maintaining Electrolyte balance
 8- Helps in Respiration

Functions of Bones
9- Blood cell formation= Hematopoisis
 Red Bone Marrow

Red gelatinous mass consisting of
Haemopoietic tissue
> Ends of long bones
> Bodies of vertebrae
> Sternum
> Flat bones of skull

 Type of Dense connective tissue ( Cells and fibers)
 Perichondrium ( Fibro-vasculo-cellular membrane)
 Cells = Characterized by Rigid with flexibility and
Resilience.
 Avascular
 Nerves and lymphatics are absent
 Cells (Chondroblasts and chondrocytes)
 Matrix => Connective tissue fibers (Collagen, Elastin)

Remember the four basic types of tissue
 Epithelium
 Connective tissue
 Connective tissue proper
 Cartilage
 Bone
 Blood
 Muscle tissue
 Nervous tissue

1.
Hyaline cartilage : flexible and resilient
2.
Elastic cartilage : highly bendable
3.
Fibrocartilage : resists compression and tension

and
 Hyaline (Glass)
 Commonest form
 Bluish white, translucent and homogenous in appearance with collagen fibers
Sites => Articular cartilage:
Covers the ends of long bones in joint cavities
=> Costal cartilage
=> Tracheal cartilage
=> Laryngeal cartilage

 Forms most of the embryonic skeleton
 Ossifies to form bone in young age

Elastic Cartilage
 Yellow; Elastin fibers as well as collagen fibers
 More elastic than hyaline
 Highly bendable
 Sites
=> Pinna of the ear
=> Epiglottis

Never o ssifies

Fibro-cartilage
 resists compression and tension
 White, Opaque with collagen fibers
 Rows of thick collagen fibers alternating with rows of chondrocytes (in matrix)
 Sites
=> Intervertebral disc
=> Intra articular disc
=> Menisci of the knees

Ossifies in old age

 Histological or Microscopically
 Gross Appearance or Macroscopically

Histological or Microscopically
1- Compact bone (dense)
 Basic unit of compact bone is an osteon.
 Osteocytes within lacunae arranged in concentric circles called lamellae .
 This surround a central canal; complex is called

Haversian system .
Weight Bearing.

Histological or Microscopically
2- Spongy bone (cancellous)
 Contains trabeculae
 Found at ends of Long Bones, Ribs, Sternum, Hips,
Vertebrae, Cranium
 Web-Like Arrangement
 Low Stress Areas Where Weight of Bone Would Be a Problem.

Compact and Spongy Bone

Compact Bone

Compact and Spongy Bone

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Developing parts of a typical long bone

 Epiphysis (Spongy):
Covered with Hyaline cartilage.
 Diaphysis (Compact):
Covered with Periosteum.
Medullary cavity with yellow and red marrow.
Examples:
 Femur, Tibia, Fibula, Humerus,
Ulna, Radius, Clavicle .

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Examples:
Metacarpals
Metatarsals
Phalanges

 Cube-shaped
 Allows flexible
 movement
Spongy bone covered by
Compact bone
Examples:
 Carpals & Tarsals,

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Flat Plates
Protect Vital Organs
Examples:
Bones of Vault of
Skull
Ribs
Scapula
Sternum

 Peculiarly Shaped to provide Support and Protection with Flexibility.
Examples:
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Vertebrae
Hip bone
Bones of base of Skull.

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Periosteum absent.
Ossify after birth.
Functions:
 Resist pressure
 Reduce friction
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Examples:
Patella
Pisiform
Fabella

cont’d
According to development:
1. Membranous = starts as fibrous membrane, calcium gradually deposited until structure becomes ossified  intramembranous ossification e.g.: bones of the skull, mandible
2. Cartilagenous = starts as cartilage, gradually ossified enchondral or intracartilagenous ossification.
e.g.: long bones

Developing parts of a typical long bone

The arterial supply of a Mature long Bone

Simple: Skin is not pierced.
Compound: Skin is pierced.
Complete: Bone is broken in half
Greenstick: Incomplete break on outer arc.
Comminuted: Broken into several pieces