Musculoskeletal System - Skeleton

Human BiologyYear 11ATAR Unit 1 & 2Musculoskeletal System - SkeletonFunctions of the skeletonProvides a framework that gives shape to the body and supports its parts. Bones also provide points of attachment for most of the muscles.Articulation varying degrees of movement depending on the bones.Providing protection to organs.E.g. brain enclosed within the skull.

Functions of the skeleton (Cont.)Bones act as storage for mineral salts and fats (e.g. calcium, phosphorus, sodium and potassium).

The bodys circulatory system can control the movement of these elements/minerals to areas of need.

Bones provide blood cell production (i.e. bone marrow).

Structure of bonesBones are living cells capable of growth and repair.A typical bone (i.e. long bone) consists of:The diaphysis (the shaft; the main section)The epiphyses (enlarged ends of the bone; normally covered with a layer of cartilage)

Structure of bones (Cont.)If we cut the bone lengthwise, the diaphysis is seen to be a hallow cylinder of compact bone surrounding a cavity.

This cavity is used as a fat storage site (yellow bone marrow).

Structure of bones (Cont.)The epiphysis on the other hand (the end regions) contains compact bone, plus:Spongy or Cancellous bone (contains many large spaces filled with marrow, in some cases red bone marrow).Periosteum is a dense, white, fibrous covering.Not present whenarticulate cartilage is covering the end.

Microscopic structure of bonesBones are classified as connective tissue. Connective tissue: cells separated from each other by large non-cellular material (called a matrix). Inorganic salts are deposited in the matrix (increases strength)

If we zoom into a bone using a microscope we find much smaller units that make up the compact bone called osteons (aka Haversian systems)Each osteon contains a central canal around which exist layers of bone (like a matrix) called lamellae.

Between the lamellae are small spaces in the matrix called the lacunae.

A bone cell (or osteocyte) occupies each lacuna. Tiny canals (or canaliculi) run between the lacunae.

These tiny canals act as connections between other cells allowing for material to pass.

CartilageCartilage connective tissue.Contains fibres made of protein called collagen.These protein fibres are embedded in a firm matrix of a protein-carbohydrate complex called chondrin.

Function: structural support, flexibilityFound in: trachea, bronchi, nose, ear.

Cartilage has a firm matrix in which collagen fibres are embedded. Within the matrix are spaces that contain cartilage cells called chondroblasts.

Overtime these spaces fill up and become matured cells called chondrocytes.

Many mature chondrocytes [A] are seen here, each located within a lacuna or "small hole".

Smaller, immature chondroblasts [B] are seen at the peripheral edges of the cartilage, where cartilage growth occurs.

Cartilage TypesHyaline cartilage contains closely packed fibres, very fine. Provides strength along with flexibility. Found where? Trachea, bronchi, moveable joints

Elastic cartilage conspicuous (or clearly visible) elastic fibres. Not as closely packed. Provide flexible elastic support.Found where? Ear

Cartilage TypesFibrocartilage coarse appearance from the parallel bundles of thick collagenous fibres that make up this tissue. Not as compacted.

Found where? In the intervertebral discs of the spinal column provides cushion between vertebrae. Also found in the articulate cartilage of the knee.Cartilage has no blood vessels. Therefore nutrition/waste removal is done via diffusion through the matrix.This is a slow process (hence slow rate of metabolism).

This explains why cartilage injuries take time to heal.

The perichondrium (connective tissue membrane) covers the external surface of cartilage contains blood vessels and supplies blood.Bones of the Skeleton206 bones make up a human adult.Some of these are fused (e.g. skull), whereas others form joints to allow for movement.

Bones are divided into two (2) sections:Axial skeleton central axis of the body. Provides the main support for posture, protects nervous system and organs (e.g. skull, ribs, sternum).Appendicular skeleton upper/lower limbs and the bones of the pectoral and pelvic girdles.

JointsThe site at which two or more bones come together.

Types include:Fibrous or fixed no movement occurs (e.g. skull). Held in place by fibrous connective tissue. The joints often break (fracture) rather than give way.

Cartilaginous or slightly moveable Held in place by cartilage. Allows for some movement (e.g. pelvic bones, joints between the ribs and sternum). Types include:Synovial or freely moveable joints - Movement is only limited by ligaments, muscles, tendons, etc. Examples: shoulder, elbow, wrist, fingers, knee, etc.

Synovial joints can be categorised by type of movement. Ball-and-socket joints Only 2 such joints exist. This forms when the spherical head of one bone fits into a cup-like cavity of another. Example: The head of the humerus (upper arm) fitting into the scapula (shoulder blade).

Synovial joints can be categorised by type of movement. Hinge joint movement in one plane only (like a door). Examples include; elbow and knee.

Pivot joint formed when rounded, pointed or conical end of one bone articulates with a ring, formed partly by bone and partly by ligament.Examples include; first vertebra, where the head is balanced (called the atlas). Another includes the radius and ulna of the forearm (rotation of the hand). Synovial joints can be categorised by type of movement. Gliding joint allows movement in any direction (side-to-side, or back-and-forth). Examples include; carpal bones, tarsal bones, the sternum and clavicle.

Saddle joint where the thumb joints the palm of the hand (allows both side-to-side and back-and-forth).Synovial joints can be categorised by type of movement. Condyloid or ellipsoid joint Allows movement in two directions, such as up and down and side to side. They have one surface of bone slightly convex that fits into a slightly concave depression in another bone.

These occur between the radius and the carpal bones, the metacarpal bones and the phalanges of the fingers.

Structure of a synovial jointArticulate capsule encloses the joint. Contains 2 layers:Fibrous capsule fibrous connective tissue attached to the bone. Allows for flexibility and prevents dislocation.Synovial membrane also the inner layer, contains loose connective tissue, supplied with blood capillaries. It lines the entire cavity except the articulate cartilage.

Structure of a synovial jointSynovial fluid secreted by synovial membrane. Fills the cavity. Acts as a lubricant. Provides nourishment for the cells of the articulate cartilage. Also contains phagocytes removes organisms and debris (from wear and tear).Excess fluid can occur during injury/inflammation.

Articulate cartilage Provides smooth surface for movement in the joint.

Articulate discs present in some joints (i.e. knee). They divide the synovial cavity into two, fluid is directed into areas of fiction.Structure of a synovial jointBursae or little sacs of synovial fluid (present in some joints). They prevent friction between a bone and a ligament or tendon, or between a bone and the skin.

Accessory ligaments holds bones together in many joints.

Movement of a jointFlexion - or bending, which usually decreases the angle between the articulating bones.

Extension or straightening, which usually increases the angle between the articulating bones.

Movement of a jointAbduction- movement away from the midline of the body (e.g. lifting arms upwards, away from body).

Adduction movement towards the midline of the body (e.g. returning arms to the sides).

Rotation movement of a none around its long axis (e.g. palm is turned upwards by twisting the forearm from the shoulder). Aging - OsteoporosisProminent in women when they hit menopause. Bone density decreases as calcium and other minerals diminish.

Osteoporosis means the loss of bone mass. Bone density decreases, risk of fractures increases.Most commonly affected bones include; vertebrae, ribs, pelvis, wrist and upper arm. Prevention: Calcium intake, vitamin D and exercise. Smoking often contributes to osteoporosis, so a lifestyle change must be made.

Aging - OsteoarthritisThe gradual change in the joints that occurs over time (associated with old age). Includes irritation of joints, wear and abrasion. This disease involves cartilage deteriorating. This means bones are NOT protected. This causes bones to wear away and bony spurs or growths to develop.

These spurs decrease space within the joint causing movement to berestricted.

Aging - OsteoarthritisBy the age of 70 almost all have symptoms (some minor).Before the age of 55 it is equal between genders.After 60 it is more common in women. Symptoms include; stiffness and pain in joints.

Those suffering notice rubbing, grating or crackling sounds when they move certain joints.

No cure. Treatment includes surgery (replacement therapy), medication for pain, physiotherapy for muscle strengthening.Homework TaskEnsure review questions on page 162 are completed.

Questions 1 to 15 only.

DUE Date: _________________________