VCE Physical Education Unit 1 SKELETAL SYSTEM

Human Skeleton

FUNCTIONS SUPPORT - organs and tissues of the body are held in place by the skeleton. SUPPORT - organs and tissues of the body are held in place by the skeleton. PROTECTION – provides a rigid surface for protection of vital organs. cranium protects the brain PROTECTION – provides a rigid surface for protection of vital organs. cranium protects the brain MOVEMENT – bones provide a base for muscle attachment. It allows movement of the body through using the bones as levers. MOVEMENT – bones provide a base for muscle attachment. It allows movement of the body through using the bones as levers. PRODUCTION & STORAGE – bones provide a site for manufacture of red & white blood cells and storage of minerals. Ie.calcium PRODUCTION & STORAGE – bones provide a site for manufacture of red & white blood cells and storage of minerals. Ie.calcium

STRUCTURE OF SKELETON  There are about 206 bones found in an adult skeleton.  The bones are divided into two main groups (1)AXIAL SKELETON (2) APPENDICULAR SKELETON

AXIAL SKELETON The axial skeleton forms the basic structure supporting the rest of the skeleton. It consists of: –Skull –Vertebral column –Rib cage

AXIAL SKELETON SKULL Cranium consists of 8 bones fused together. Face has 14 bones. Most are fused, whilst others like the mandible (lower jaw bone) can move independently

Fusion of the human skull

AXIAL SKELETON VERTEBRAL COLUMN Divided into 5 main regions (1)C ervical spine (7) (2)T horacic spine (12) (3)L umbar spine (5) (4)S acrum (5) (5)C occyx (4) The 5 sacrum vertebrae and 4 coccyx vertebrae are fused to form one solid bone.

Cervical, Thoracic, Lumbar, Sacrum and Coccyx

AXIAL SKELETON ATLAS – first cervical vertebraATLAS – first cervical vertebra AXIS – second cervical vertebraAXIS – second cervical vertebra Spinal chord runs down the canal formed by the vertebra being stacked on top of one another.Spinal chord runs down the canal formed by the vertebra being stacked on top of one another. Intervertebral Discs are found between each vertebrae and keep spine flexible and they absorb shockIntervertebral Discs are found between each vertebrae and keep spine flexible and they absorb shock Coccyx remnance of a tailCoccyx remnance of a tail

AXIAL SKELETON THORAX 12 pairs of ribs12 pairs of ribs Joined to thoracic vertebraeJoined to thoracic vertebrae Top 10 ribs joined to sternumTop 10 ribs joined to sternum Remaining two have “free” ends – ‘floating’Remaining two have “free” ends – ‘floating’

APPENDICULAR SKELETON Forms mainly the extremities of the body and their connections to the axial skeletonForms mainly the extremities of the body and their connections to the axial skeleton Consists ofConsists of - limbs (arms & legs) - shoulder and pelvic girdles

APPENDICULAR SKELETON THE ARM AND HAND

APPENDICULAR SKELETON THE LEG AND FOOT

TYPES OF BONE TISSUE (1)COMPACT BONE TISSUE  Heavy, dense, strong bone tissue  Consist of closely packed osteon.  Osteon consist of a central canal called osteonic canal.  It surrounded by concentric ring called lamella  Thickest at the centre of the shaft

TYPES OF BONE TISSUE (2) CANCELLOUS BONE TISSUE or “spongy bone” IIIIt consist of Plates (Trabecule) SSSStrong, hard & less dense than compact bone FFFFound mainly ends of bones

Bone Development and Growth The terms osteogenesis and ossification are often used synonymously to indicate the process of bone formation. Parts of the skeleton form during the first few weeks after conception. By the end of the eighth week after conception, the skeletal pattern is formed in cartilage and connective tissue membranes and ossification begins.

Intramembranous Intramembranous ossification involves the replacement of sheet-like connective tissue membranes with bony tissue. Bones formed in this manner are called intramembranous bones. They include certain flat bones of the skull and some of the irregular bones. The future bones are first formed as connective tissue membranes. Osteoblasts migrate to the membranes and deposit bony matrix around themselves. When the osteoblasts are surrounded by matrix they are called osteocytes.

Endochondral Ossification Endochondral ossification involves the replacement of hyaline cartilage with bony tissue. Most of the bones of the skeleton are formed in this manner. These bones are called endochondral bones. In this process, the future bones are first formed as hyaline cartilage models. During the third month after conception, the perichondrium that surrounds the hyaline cartilage "models" becomes infiltrated with blood vessels and osteoblasts and changes into a periosteum.perichondrium The osteoblasts form a collar of compact bone around the diaphysis. At the same time, the cartilage in the center of the diaphysis begins to disintegrate. Osteoblasts penetrate the disintegrating cartilage and replace it with spongy bone. This forms a primary ossification center. Ossification continues from this center toward the ends of the bones. After spongy bone is formed in the diaphysis, osteoclasts break down the newly formed bone to open up the medullary cavity.

Bone Growth Bones grow in length at the epiphyseal plate by a process that is similar to endochondral ossification. The cartilage in the region of the epiphyseal plate next to the epiphysis continues to grow by mitosis. The chondrocytes, in the region next to the diaphysis, age and degenerate. Osteoblasts move in and ossify the matrix to form bone. This process continues throughout childhood and the adolescent years until the cartilage growth slows and finally stops. When cartilage growth ceases, usually in the early twenties, the epiphyseal plate completely ossifies so that only a thin epiphyseal line remains and the bones can no longer grow in length. Bone growth is under the influence of growth hormone from the anterior pituitary gland and sex hormones from the ovaries and testes.

TYPES OF BONES Bones are classified into 5 groups according to their shape:  LONG BONES –  are longer than they are wide are called long bones. They consist of a long shaft with two bulky ends or extremities. They are primarily compact bone but may have a large amount of spongy bone at the ends or extremities. Long bones include bones of the thigh, leg, arm, and forearm.  incl. humerus, radius, tibia and phalanges

TYPES OF BONES  SHORT BONES –  Short bones are roughly cube shaped with vertical and horizontal dimensions approximately equal. They consist primarily of spongy bone, which is covered by a thin layer of compact bone. Short bones include the bones of the wrist and ankle.  incl. carpals and tarsals

TYPES OF BONES  FLAT BONES –  Flat bones are thin, flattened, and usually curved. Most of the bones of the cranium are flat bones.  incl. skull, pelvis, ribs and shoulder blades (Flat bones protect vital organs and provide sites for muscle attachment)

TYPES OF BONES  IRREGULAR BONES –   Bones that are not in any of the above three categories are classified as irregular bones. They are primarily spongy bone that is covered with a thin layer of compact bone. The vertebrae and some of the bones in the skull are irregular bones.   incl. facial and vertebrae

TYPES OF BONES Short bones (carpals)

ANATOMICAL TERMINOLOGY TERMDEFINITION Superior Toward the Head Inferior Toward the feet Anterior (ventral) Front Posterior (dorsal) Back Medial Toward the midline (inside) Lateral Toward the side (outside) Proximal Nearer the trunk Distal Further from the trunk Prone Face down (on stomach) Supine Face up (on back)

BODY GROWTH  Changing rate of growth to the body is affected by two things – height and weight.  Differs from time to time during life and differs for various body parts.

Adolescent Growth Spurt  Most rapid gains in height within first 1 to 2 years of life  By 2 years of age – an individual has reached half their adult height.  Pubertal growth spurt is the next major increase in height. (11-12 years for girls and years for boys approximately)  Body changes length in the following pattern (1) Feet and hands develop first (increase in size) (2) Lower legs and forearms grow rapidly (3) Thighs and upper arms increase in length (4) Finally trunk develops in length The width of the body develops next, as the shoulders and pelvis widens

SHORT BONE GROWTH  The outside of a short bone is formed by cartilage. The cartilage grows until the final shape of the bone is formed.  Meanwhile the bone ossifies (hardens into bone) from the inside outwards. Eventually all cartilage is ossified, and growth is complete.

LONG BONE GROWTH Two growth processes responsible for done development. First process:  OSTEOBLASTS (bone builders) – add bone to the outside surface, enlarging and elongating the bone.  OSTEOCLASTS (bone eaters) – tunnel out the marrow cavity and internal spaces (these work at the same time as osteoblasts.) Second process (greatest growth occurs):  EPIPHYSEAL PLATES (growth plates) found at either end of the bone where the shaft (diaphysis) meets the head or base (epiphysis). These growth plates are made of cartilage cells which multiply rapidly and the outside cells ossify, increasing the length of the shaft.

LONG BONE GROWTH

GROWTH HORMONE (GH)  GH - Responsible for most growth changes occurring.  Produced by the pituitary gland, at the base of the brain.  Growth Hormone: (1)stimulates the epiphyseal plates to expand and form bone (2)increase protein uptake by the muscles, therefore increasing muscle growth

FACTORS AFFECTING GROWTH  Basic control of growth is genetic  Starvation and Malnutrition can delay growth spurt  Major illness slow down growth  Regular exercise has many growth benefits  Aerobic exercise also increases the size and efficiency of the heart, blood and lungs. However, repetitive long distance training for marathons or triathlons may damage epiphyseal plates.

SKELETAL SYSTEM Reference: VCE Phys Ed Book 1 (your text) Chapter 1 pg 3-10 The End