STRUCTURE AND FUNCTIONS OF BONES AND JOINTS
Functions of bones 1. Frame work of the body 2. Attachment to the muscles and tendons 3. Allowing the movement of the body 4. Forming the boundaries of cranial , thoracic, and pelvic cavities, protecting the organ they contain 5. Haemopoiesis 6. Mineral storage ( calcium phosphate etc)
Types of bones Long bones Other types Long bones with a shaft and 1. Short bones- carpals two extremities 2. Irregular bones – Eg, Femur, tibia Etc vertebrae, skull bones 3. Flat bones – sternum, ribs 4. Sesamoid bones (small) – patella,
Bone structure
A mature long bone Epiphysis Diaphysis (shaft) Epiphysis
Microscopic structure of bones • Calcium salts- calcium phosphate (65%) • Osteoids consisting of collagen • Cellular components (2%) • Bone cells- osteoblasts osteocytes osteoclasts
Osteoblast Bone forming cells present in :- * deeper layers of periosteum * centers of ossification * at the ends of diaphysis * at the site of a fracture
• Osteocytes • Mature bone cells present in the canaliculi • Osteoclasts Maintain the bone shape. A fine balance of osteoblast and osteoclast activity maintains normal bone structure and bone functions.
Compact bone • Osteons or Haversian system • Haversian canal and perforating canal • Lamellae and lacunae • Canaliculi • Interstitial lamellae
Spongy bone Formed of the frame work of trabeculae * Red bone marrow
Development of bone tissue (Osteogenesis or ossification) • Begins before birth (8 weeks) and continues till 21 years • Long, short and irregular bones – cartilage models • Flat bones – membrane models • Sesamoid bones – tendon models. Osteoblasts → osteoids → calcification → osteocytes
Developement of long bones • Osteogenic cells or centers of ossification • Bone collar – 8 weeks of gestation – primary ossification • As the blood supply improves secondary centers of ossification develops at the epiphysis. • Development completes when the cartilage is completely oscified
Hormonal regulation • Growth hormone, Thyroid hormones (thyroxin and tri-iodothyronine) • Testosterone – helps in the growth spurt at puberty, closes epiphyseal plate. • Oestrogens – widens pelvis, maintains bone mass of adult female. • Calcitonin and parathyroid hormone – maintains calcium level in blood.
• Weight bearing exercises improve thickness and strength of bone. • Healthy bone tissue requires adequate supply of calcium , vitamin A,D and C, minerals such as phosphate ,iron, manganese etc • Vit A – osteoblast activity • Vit- C – Collagen synthesis • Vit – D – calcium and phosphate absorption.
Bone markings
Bone fractures • Simple – The bone ends do not protrude through the skin. • Compound – The bone ends protrude through the skin. • Pathological – Fractures of bone weakened by diseases.
Healing of bone • stage 1 • A hematoma forms between the ends of bone and I surrounding soft tissues
• Stage 2 • Accute inflamation and accumulation of inflamatory exudates containing macrophages that phagocytose the hematoma and small fragments of bone without blood supply (5 days) • Fibroblast migrate to the site, granulation tissue and new capillaries develop.
• Stage 3 • Osteoblast secret spongy bone which unite broken ends protected by an outer layer of bone and cartilage - callus
• Stage 4 • Callus matures and the cartilage is gradually replaced with new bone.
• Stage 5 • In weeks or months medullary canal is formed through the callus • In time bone heals completely. Callus tissue is replaced by mature compact strong bone.
Factors affecting bone healing • Tissue fragments between the bone ends • Deficient blood supply • Poor alignment of bone ends • Continued mobility of bone ends • Infection • Systemic illness • Malnutrition • Drugs- corticosteroids • Ageing
Complications of fractures • Infection (osteomyelitis – pathogens enter through broken skin or blood borne) • Fat metabolism – fat enters in the circulation through torn veins and deposit in lungs
Blue part is axial sceleton Axial skeleton comprises 80 bone distributed along the main axis of the body. The skull,vertebral column, sternum and ribs constitute axial skeleton.
SKULL Skull is a bony structure present in the body which protects brain from external injuries.
Skull is made up of many bones ➢ Sphenoid bone ➢ Zygomatic bone ➢ Ethmoid bone ➢ Maxilla ➢ Frontal bone ➢ Mandible ➢ Parietal bone ➢ Temporal bone ➢ Lacrimal bone ➢ Occipital bone ➢ Nasal bone ➢ Occipital condyl
Sphenoid bone The sphenoid bone (from Greek sphenoeides, \"wedgelike\") is an unpaired bone situated at the base of the skull in front of the temporal bone and basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the orbit. Its shape somewhat resembles that of a butterfly or bat with its wings extended. Portions It is divided into the following parts: * A median portion, known as the body of sphenoid bone, containing the sella turcica which houses the pituitary gland * Two greater wings and two lesser wings * Pterygoid processes of the sphenoides which project from it posteriorly (below) Two sphenoidal conchae are situated at the anterior and posterior part of the body.
Sphenoid bone
Ethmoid bone The ethmoid bone (from Greek ethmos, \"sieve\") is a bone in the skull that separates the nasal cavity from the brain. As such, it is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a spongy construction. The ethmoid bone is one of the bones that makes up the orbit of the eye. Articulations The ethmoid articulates with fifteen bones: * four of the neurocranium—the frontal, and the sphenoid (at the sphenoidal body and at the sphenoidal conchae). * eleven of the viscerocranium—, two Nasal bones, two maxillae, two lacrimals, two palatines, two inferior nasal conchae, and the vomer
Ethmoid bone
Frontal bone The frontal bone is a bone in the human skull that resembles a cockle shell in form, and consists of two portions: * a vertical portion, the squama frontalis, corresponding with the region of the forehead. * an orbital or horizontal portion, the pars orbitalis, which enters into the formation of the roofs of the orbital and nasal cavities
Parietal bone The parietal bones are bones in the human skull and form, by their union, the sides and roof of the cranium. Each bone is irregularly quadrilateral in form, and has two surfaces, four borders, and four angles.
External The external surface is convex, smooth, and marked near the center by an eminence, the parietal eminence (tuber parietale), which indicates the point where ossification commenced.
PARIETAL BONE
Lacrimal bone The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Borders * the anterior articulates with the frontal process of the maxilla; * the posterior with the ethmoid; * the superior with the frontal bone. * Tlahceriimnfaelrciorresist divided by the lower edge of the posterior
Maxilla The maxilla (plural: maxillae), also known as the mustache bone, is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible (lower jaw), which is also a fusion of two halves at the mental symphysis.
Function The alveolar process of the maxilla holds the upper teeth, and is referred to as the maxillary arch. The maxilla attaches laterally to the zygomatic bones (cheek bones). The maxilla assists in forming the boundaries of three cavities: * the roof of the mouth * the floor and lateral wall of the nasal antrum * the floor of the orbit
The mandible consists of: *A curved, horizontal portion, the body. * two perpendicular portions, the rami, which unite with the ends of the body nearly at right angles * Alveolar process, the tooth bearing area of the mandible * Condyle, superior (upper) and posterior projection from the ramus, which makes the temporomandibular joint with the temporal bone * Coronoid process, superior and anterior projection from the ramus.
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