Supporting systems and movement in Animals

Hydrostatic skeleton

Exoskeleton

Endoskeleton

Types of skeletons

Hydrostatic skeleton Exoskeleton Endoskeleton

Description Consists of fluid under pressure in a closed body compartment (fluid-filled cavity surrounded by muscles)

A hard, dead case made up of chitin formed on the outside of the body.

Is made up of living, hard supporting structures or bone lying inside the soft tissues of an animal

Example Jelly fish, earthworms Arthropods, crustaceans Human, animals

Advantage Ideal for organismsliving in an aquatic medium. Act as cushions against shock. Provides support. Flexible

Protects the organism from being attacked by predators, prevents dehydration, reduces damage and injury. Aids in movement

Offers protection to internal organs, allows different parts of skeleton to work separately, allows growth (large). Repairs itself.

Disadvantage Cannot provide support for movements such as walking and running. Need moisture (aquatic). Stay small. No protection to soft parts. Slow.

Hard and thick and cannot provide room for growth (moult). Is softer at the joints to allow movement. Does not allow gaseous exchange.

Parts which lie outside of the skeleton are not protected against predators. Can easily dehydrate.

Tissues forming the skeletal system

• Bone tissue : support, shape, protection

• Ligaments : join bones together

• Tendons: connects skeletal muscle to the bone

• Cartilage: lining joints and at the ends of bone to prevent friction,

cushion between bones as shock absorbers

• Blood: provides nutrients to the cells of the skeletal system and removes

waste products

• Nerves: enervate (send signals) cells of the skeletal system

Functions of the skeleton

• Support and shape

• Protection of vital organs

• Locomotion and movement

• Production of red blood cells (RBC)

• Storage of minerals - Calcium bank

• Provides attachment points for skeletal muscle

• Aids in the transmission of sound waves to the

inner ear for hearing to happen

Types of bones

• Long bones: femur, tibia, fibula, humerus, ulna and

radius

• Short bones: metacarpals, metatarsals, phalanges

• Flat bones: cranium, ribs, scapula, sternum, pelvic

bones

• Irregular bones: carpals, vertebrae

• An adult human body has 206 bones.

• The bones together have a mass of 8-15kg.

• The skeletal system is made up bones, jointsand muscles.

• Made up the 80 bones which make up the

skull, vertebral column (26/33), ribs (12 pairs) and sternum.

• Protects the internal organs

• Allows for flexibility of movement

• Allows for the attachment of the bones of the appendicular skeleton.

• Are found in the jaw.

• Not part of the skeletal system

as they are not made of bone.

2.1.2.3

2.1.2.3

• Made up of the cranium and facial bones.

• Cranium is made up of flat bones which fit together by special jagged joints called sutures.

• The under side of the skull has a large opening called the foramen magnum through which the spinal cord leaves.

• On both sides of the foramen

magnum there is a smooth ridge

called a condyle.

• The first two condyles make contact

with the atlas(first vertebrae).

• Facial bones include: bones of forehead, cheek bones, nasal bones and bones of the upper and lower jaw.

• “Hinge” between skull and atlas allow nodding in all directions

• “Hinge” between atlas and axis allows you to shake your head - no

Made up of 33 vertebrae organised into five regions as follows:

7 cervical vertebra in theneck region.12 thoracic vertebra in the chest region.5 lumbar vertebra in theback region.5 sacral vertebra which arefused.4 fused vertebra making upthe coccyx.

• Each vertebra interlocks with the one in the front and the one behind it to form a continuous spinal canal through to the cranium.

• Spinal cord runs through the spinal canal.

• Tiny gaps occur between the vertebra to allow spinal nerves to enter or leave the spinal cord.

• Cartilaginous discs occur between the vertebra to prevent friction and act as a shock absorber during running, walking and jumping. Separates vertebrae to allow spinal nerves to enter and leave the spinal cord and is flexible for movement

• Protects the spinal cord which runs through it.

• Made up of separate vertebra and therefore gives flexibility allowing us to bnd backwards,forwards and sideways.

• The gaps between the vertebra allow nerves to enter and leave the spinal cord.

Cervical spondylosis: When

the discs between the vertebra starts to degenerate, if this happens to the discs of the cervical vertebra pain occurs in the neck and the arms.

Slipped discs: injury especially

during middle and old age can cause the cartilaginous discs to slip out of position. The “slipped disc” may press against the spinal nerves causing severe back pains.

• Only 5-10% of all back pains are caused by slipped discs, most are caused by muscular spasms. The muscles become strained and are accompanied by sharp pains.

Causes of muscle spasm: • picking up something heavy• Strenuous exercise after a long period of

inactivity• Untrained or overweight persons• Jobs which require a person to remain seated

for long periods of time• High heel shoes

• Is made up of 12 pairs of ribs, the vertebral column and the sternum.

• All 12 pairs are joined to the vertebral column.

• The first 7 pairs are directly attached to the sternum by means of costal cartilage and are called true ribs.

• The next 5 pairs are called false ribs.

• The first 3 pairs of the false ribs are joined to each other before the sternum (with cartilage).

• The last two pairs are not attached to the sternum at all and are therefore called floating ribs.

• Between the ribs are intercostal muscles

• First 10 pairs of ribs and clavicle are attached to the sternum

• Function of ribs and sternum

– Protect heart and lungs

– Allow lungs to expand and contract as we breathe

Diagram representing the rib cage

• Protects the internal organs (heart and lungs)

• Movement of the ribs causes the volume of the thoracic cavity to be increased or decreased and therefore assists in breathing.

• Made up of 126 bones which make up the pectoral(shoulder) girdle and upper limbs as well as the pelvic girdle and lower limbs.

• Appendicular comes from the words appendages.

• Made up of two scapulae and two clavicles.

• The scapula has a shallow socket cavity into which the humerus fits.

• Each upper limb is made up of a humerus, radius and ulna, 8 carpals, 5 metacarpals and 14 phalanges.

• The humerus fits into the glenoid cavity forming a ball and socket joint.

• Forearm: radius and ulna

• Ulna fits into the humerusforming a hinge joint

• The 8 carpals or wrist bones glide over each other forming gliding joints.

• Made up of two hip bonesjoined to each other in frontand to the sacrum of the vertebral column at theback.

• Hip bone is made up of three bones fused together: ilium, ischium and pubis.

• The pubic symphysis joins the two hip bones together.

• The acetabulum (deep socket) is present in each hip bone into which the femur fits.

• Each leg or lower limb is made up of a femur, tibia and fibula, patella, tarsals, metatarsals and phalanges.

• The femur (thigh bone) fits into the acetabulum forming a ball and socket joint.

• The tibia and fibula make up the lower leg.

• The upper end of the tibia articulates with the lower end of the femur forming a hinge joint at the knee. The patella (knee cap) occurs in the front.

• There are 7 small tarsals or ankle bones which glide over each other forming gliding joints. The largest tarsals form the heel bone.

• The 5 metatarsals are bones of the foot

• The 14 phalanges (3 in each toe) form the hinge joints with each other.

Pectoral girdle Pelvic girdle

Flexible to provide full and quick movement Rigid as it supports the entire body’s weight

Glenoid cavity of shoulder is shallow Acetabulum of hip is deeep

Skeleton function

• Support: supports and anchors the muscles in the body (vertebrae and legs NB for support)

• Protection: protects soft tissues and organs (skull, vertebrae, ribs)

• Movement: Helps movement (muscles pull bones)

• Blood cell formation: production of red and white blood cells in certain bone components

• Mineral storage: reservoir for calcium and phosphorous

Skeletal Tissues

• Skeleton made up of both cartilage and bone

• Both are living tissues

• Bone is hard and rigid (calcium phosphate)

• Cartilage is tough and flexible

• Intercellular matrix is different

• Both gives support to the body

Bone tissue

• Contains bone cells called osteocytes.

• Osteocytes are embedded in a rigid intercellular matrix or ground substance.

• Collagen, mineral salts, predominantly salts of calcium magnesium and phosphate form 65% of the dry mass of bones

Bone structure

• Compact bone (very hard) is found in the shaft and both ends (heads)

• Compact bone is made up of Haversian system

• Spongy bone gives support while preventing bones from becoming too heavy

• Yellow marrow is mostly fat

• Red marrow is where formation of white and red blood cells and platelets

• Ends of bones covered in cartilage

Structure of a typical long bone

Bones function

• Providing support

• Enabling locomotion

• Storing calcium, magnesium and phosphate

• Producing red and white blood cells

Cartilage

• Not as hard and rigid as bone, because it contains fewer mineral salts.

• Composed of specialized cartilage cells called chondrocytes, located within large amount of matrix.

• Does not contain nerve or blood fibres, it receives nutrients by diffusion from the surrounding tissue or fluid.

3 types of cartilage:

• Hyaline cartilage

• Fibrocartilage

• Elastic cartilage

Hyaline Cartilage

• The most abundant type of cartilage in the human body.

• Covers the ends of bones where they meet in joints, forming a supportive cushion preventing friction during movement

• Supports the tip of the nose

• Connects the ribs to the sternum

Fibrocartilage

• Contains a large amount of collagen fibres

• Stronger and less elastic than hyaline cartilage

• Found between intervertebral discs

Elastic Cartilage

• Contains of a large amount of elastin fibers

• flexible

• Maintains the shape of the earflaps and the epiglottis.

Tendons formed by White fibrous

• Large number of non-elastic collagen fibres.

• Connect muscles to bones, therefore they have to be inelastic.

• Transmit the contraction or relaxation of muscles directly to bones enabling movement.

Ligaments formed by Yellow elastic

• A band of tough connective tissue that connects a bone to another bone at moveable joints.

• Ligaments are elastic

• They lengthen when placed under tension and return to their original shape when the tensions released

• Keep joints stable and are important in preventing dislocation

Joints

• Joint – a point of contact between two or more bones with tissue around it

• Three types:1. Fixed Joints

o Bones are joined by white fibrous connective tissue

o Bones are so close together that no movement occurs

o Examples – joints between the teeth and the jawbone, skull sutures

2. Partly Movable Joints (gliding joints)o Joints that allow for some movement

o Cartilage that holds the joint together is soft and flexible

o Examples – disks of cartilage between the spinal vertebrae

3. Synovial Joints (free movement)

o Allow free movement between the bones that they join

o These joints are surrounded by a synovial membrane that secretes a lubricating fluid

o The synovial fluid and the hyaline cartilage covers the surfaces and allows for movement with minimal friction

o The joint capsule encloses the joint

o Ligaments hold the joint together by binding bone to bone

o Example – The knee

X-rays

• Used to look at bones and joints of humans and animals

• Used to look for fractures bones or bone pathology (tumour)

Skeletal Muscle

• Is attached to bone by tendons

• Is made up of muscle cells called muscle fibres

– These muscle fibres are grouped into bundles

• It contains a large number of blood vessels and nerve fibres

• The nerve endings give the muscle instructions to contract or relax

• Is known as striated due to the alternating light and dark striations

– These striations result from the arrangement of contractile units called sarcomeres

Skeletal Muscle fibres

• These are long, threadlike cells with many nuclei lying close to the surface

• They can reach many centimetres in length

• They group together into bundles surrounded by connective tissue

• These bundles are bound together by connective tissue to form a skeletal muscle

Myofibrils

• Each muscle fibre is made up of a number of myofibrils that run parallel in the muscle fibre

• These myofibrils are separated from one another by mitochondria and other organelles

• Myofibrils are divided into many repeating sarcomeres (contractile units)– These contractile units contain thick myosin (dark band) and

thin actin (light band) filaments– These give the muscle their stripped appearance and are

responsible for muscle contraction

Muscle Contraction

• The actin and myosin filaments slide over one another to produce contraction

• During contraction the myosin stays the same length but the actin becomes thinner

• During relaxation the actin returns to its original length

• Movement results from the contraction of millions of sarcomeres in the skeletal muscle

• This contraction shortens the muscle which moves the bone to which it is attached

Muscle contraction cont.

• Muscle contraction requires energy

• This energy is obtained from the mitochondria during cellular respiration

• Blood vessels transport oxygen and glucose (needed for cellular respiration) to the muscle and remove carbon dioxide to the lungs

• Regular exercise increases the size of each fibre and hence the size of the entire muscle– These muscles are then more efficient at gaining

energy due to the increase in the size and number of mitochondria

Human Movement

• Locomotion is the ability to move from one place to another

• Antagonistic muscles – pairs of skeletal muscle that work together but have the opposite effect

• Skeletal muscle is attached to the bone at two points– Point of origin – point at which the muscle is attached

to a bone that will not move by contraction of the muscle

– Point of insertion – point at which muscle is attached to the bone that will be moved by contraction of the muscle

Human Movement cont

• Example of antagonistic muscles – the Biceps and Triceps

• Biceps attached to the scapula by two tendons (point of origin)

• Biceps attached to the radius (point of insertion)

• Triceps attached to the scapula with one tendon and the humerus with two tendons (points of origin)

• Triceps attached to the ulna just behind the elbow joint (point of insertion)

Human Movement Cont

• When the biceps contracts, the triceps relax and the arm bends

• When the triceps contract, the biceps relax and the arm straightens

• When the body is at rest the antagonistic muscles remain in a state of tension to hold the body in position in order to move when required

Muscles and locomotion

• Walking is the main form of locomotion in humans.

• This occurs in a sequence of steps using antagonistic pairs of skeletal muscle

• The sequence of the right leg for a single stride are as follows

– Calf muscles contract, raising the heel

– The ball of the foot presses down into the ground and the hamstrings contract, raising the foot off the ground

– All weight is transferred to the left leg

– Quadriceps muscles contract moving foot forwards

– The foot is placed on the ground, heel first

– Weight is transferred back to the right leg

Muscles and locomotion cont

• Arm movements help balance the body during each stride

• The right arm moves with the left leg• The left arm moves with the right leg

• Table 1 pg 109 provies the roles of bones, joints, ligaments and tendons in locomotion

• Figure 2 pg 109 provides a diagram of the antagonistic muscles involved in walking

Diseases of the skeletal system

• The skeleton can become weak due to aging, poor eating habits, deficiency of nutrients and minerals or as a result of injury

• These factors increases the risk of fracture or developing a skeletal disease

• These diseases are painful and make simple daily activities such as walking extremely difficult

Osteoporosis

• Bones become brittle from loss of bone tissue

• Causes – natural aging (bone broken down faster than replaced), deficiencies of vitamin D or calcium, hormonal changes

• Increases in women over menopause as no more oestrogen is produced which helps maintain bone mass

• Symptoms – degeneration of the spine leading to a hunched back

• If left untreated it could progress painlessly until a bone fractures or breaks

• Treatment aim at preventing or slowing further degeneration

• Building strong bones before 30 can prevent osteoporosis

• A healthy lifestyle – moderate weight bearing exercise, a balanced diet and no smoking and drinking is important to keep bones strong

Rickets

• Bones soften due to lack of vitamin D (required to absorb calcium and phosphorus from food)

• Occurs in children

• Lack of sunlight is the main cause of lack of vitamin D; poor nutrition may also play a role

• Symptoms – bowed legs, breastbone projection, unusual curvature of the spine and pelvic deformities

• If treated early with vitamin D rickets can be cured

• If not cured, it can lead to serious complications

• In adults – osteomalacia (progressive softening and decalcification of bony tissues)

Osteoarthritis

• Degeneration of the joint cartilage and underlying bone

• As a result the bones rub against each other causing swollen, painful, inflamed joints and loss of movement

• Over time bones spurs may grow where cartilage has been lost and joint space narrows

• Risk factors – heredity, age, obesity, previous injuries to cartilage or bone and joint infections

• Treatment – medication to reduce pain, gentle exercise to prevent stiffness or in severe cases surgery to replace the joint

• No cure