Animals without a vertebral column about 95% of animals are in this group e.g. jellyfish, flatworms, roundworms and arthropods

A joint not allowing any movement e.g. serrated joints between bones of the cranium

Joints that allow a small amount of movement e.g. between vertebra

High energy x-rays penetrate soft tissue and less so bones making it possible to visualize the internal skeleton. Used by doctors to diagnose bone fractures and dislocation of joints

Muscles attached to the skeleton to bring about movement of parts of the body. Attached by in elastic tendons They have light and dark bands (striated) They are voluntary muscles

Skeletal system Flashcards by Ryan de Roo

What is a hydrostatic skeleton and example organisms

fluid filled cavity surrounded by muscles
e.g. jellyfish, earthworm, snail

(Image: https://www.slideshare.net/nirmalajosephine1/biology-form-5-chapter-2-locomotion-support-21-part-1)

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How does a hydrostatic skeleton work?

Fluid provides support against muscles that contract
The pressure that the fluid exerts changes the animals shape according to which muscles are contracting
This brings about movements

(image: http://faculty.fmcc.suny.edu/mcdarby/BIO170Book/12-AnimalStructure.html)

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Advantages of a hydrostatic skeleton

Anatomy simple, no extra support organs needed
Body elastic and can change shape easily
No need for a specialised support system, living in water, the water provides support

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Disadvantages of hydrostatic skeleton

Animals are slow in moving
Require aquatic or moist environment
Limited size of animal
No protection from skeleton

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What is an exoskeleton and examples of animals

An external skeleton
made of chitin on the outside of the animals body
E.g. arthropods (insects)
Some animals have it further hardened with calcium carbonate (e.g. crabs)

(Image: http://www.dierk-raabe.com/biological-natural-materials/)

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Advantages of an exoskeleton

Supports and protects underlying tissue and organs
The inside is a place of attachment for muscles
The skeleton has joints for flexibility
Quick movement possible
The skeleton prevents desiccation (drying out)

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Disadvantages of an exoskeleton

Limited size of the animal as it is heavy
Larger, heavier animals have more limited movement
Limits growth and the animal needs to moult
Moulting leaves the animal vulnerable as a new skeleton forms
Exoskeleton impermeable to gases so a specialized respiratory system needed.

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What is an Endoskeleton and examples of animals

An internal skeleton on the inside of the animals body
made of bone and cartilage
Found in vertebrates e.g. fish, frogs, reptiles and mammals

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Advantages of an Endoskeleton

skeletal tissues grow as the animal grows
protects vital organs e.g. Brain
provides good structure to give the body shape
provides a place for muscles to attach for movement
joints between bones make the body flexible

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Disadvantages of Endoskeleton

More vulnerable to desiccation (drying out)
No outer protection

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Vertebrate animals

Animals with a vertebral column made of bone or cartilage
Members of the phylum Chordata
e.g. fish, frogs, reptiles, birds and mammals

(Image: http://byjus.com/biology/vertebrates/)

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Invertebrate animals

Animals without a vertebral column
about 95% of animals are in this group
e.g. jellyfish, flatworms, roundworms and arthropods

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Different types of skeletons in animals

Hydrostatic skeleton
Exoskeleton
Endoskeleton

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Joints

The junction in the skeleton where two or more bones meet and are joined by ligaments or cartilage

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immovable joints

A joint not allowing any movement
e.g. serrated joints between bones of the cranium

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semi-movable joints

Joints that allow a small amount of movement
e.g. between vertebra

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synovial joints

Joints allowing free movement

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parts of a synovial joint

Bones covered with hyaline cartilage
A enclosing sac made of ligament called the joint capsule
Capsule lined with a synovial membrane
Capsule contains synovial fluid
Ligaments attach the two bones of the joint

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Types of synovial joint

Ball and socket joints e.g. hip and shoulder
Hinge joints e.g. elbow and knee
Pivot joints e.g. atlas and axis
Gliding joint e.g. wrist and ankle joints

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x-Ray photo’s

High energy x-rays penetrate soft tissue and less so bones
making it possible to visualize the internal skeleton.
Used by doctors to diagnose bone fractures and dislocation of joints

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skeletal muscles

Muscles attached to the skeleton
to bring about movement of parts of the body.
Attached by in elastic tendons
They have light and dark bands (striated)
They are voluntary muscles

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Structure of skeletal muscles

Made up of many muscle fibres (muscle cells)
bound together by connective tissue into perimysium bundles
Perimysium bundles are bound together to form the epimysium, the complete skeletal muscle

(Image: https://training.seer.cancer.gov/anatomy/muscular/structure.html)

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Structure of a muscle fibre

A single elongated cylindrical cell
Consists of thousands of myofibrils
Myofibrils contain myosin and actin protein filaments
Myosin thicker and darker than actin giving the fibre a banded appearance

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Sarcomere of a muscle fibre

A functional unit of a muscle allowing it to contract.
Region where actin and myosin filaments overlap.

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How a muscle fibre contracts

* Nerve fibres transmit impulses to the sarcomere. * Thin actin filaments slide past thicker myosin filaments to increase their overlap. * The sarcomeres shorten * This shortens the overall length of the muscle fibres and in tern the whole muscle.

Antagonistic muscles and an example in the arm

* Skeletal muscles arranged in pairs * When one contracts, the other relaxes * Allow coordinated movements * e.g. The bicep and tricep muscles in the forearm (Image: http://www.jeron.je/anglia/learn/sec/science/body/muscle.htm)

How the arm straightens

* Tricep contracts and bicep relaxes * The elbow joint extends and the arm is straightened

How the arm lifts/bends

* The bicep contracts and the tricep relaxes * The elbow joint bends and the forearm is lifted. (Image: http://www.mychhs.colostate.edu/david.greene/Yamagata2007\_distal\_upper\_extremity\_lecture.htm)

What is rickets?

* A childhood deficiency disease affecting the skeleton * bones become soft, bend and weaken

Symptoms of rickets

* Bones still growing are deformed e.g. bent/bow legs * High incidence of bone fractures and weakness * Delayed growth, * Pain in the spine, pelvis and legs.

Causes of rickets

* Shortage of vitamin D * Vitamin D is needed for absorption of calcium * Calcium is needed for bone and teeth development

What is osteoporosis?

* A disease of the bones * Characterized by a decrease in bone density * Bones become porous and less dense

Causes of osteoporosis

* Shortage of calcium * Greater bone absorption than bone building * A lack of certain hormones, particularly estrogen in women * Lack of exercise

Prevention of osteoporosis

* Peak bone density is reached at approximately 25 years of age, * it is important to build strong bones by that age. * Sufficient calcium and vitamin D intake to ensure sufficient bone building. * Sufficient exercise while bones are growing

Symptoms of osteoporosis

* Usually bone density loss starts long before symptoms * Weakened bones * Increased risk of fracture of hips, spine and wrists * Curved back and decreased height

What is arthritis

* A disease that causes severe pain in the joints * Loss of movement in joints * Inflammation of the joints

What causes inflammation?

* Inflammation causes swelling, pain and loss of movement of the affected area * Usually caused by the bodies immune system reaction to injury or pathogens

What is osteoarthritis?

* Cartilage of a joint aging and disintegrating with time * Bones grind against each other causing inflammation * Common in hips, knees, feet, fingers and spine

Factors that might lead to osteoarthritis

* Being overweight. * Getting older. * Joint injury. * Joints that are not properly formed. * A genetic defect in joint cartilage. * Stresses on the joints from certain jobs and playing sports.

What is rheumatoid arthritis?

* Synovial membranes in joints thicken * Too much synovial fluid causes inflammation * Causes deformation of joints * Usually affects finger joints, wrists, knees and toes

Causes of rheumatoid arthritis

* An autoimmune disease * Bodies immune system attacks its own tissues * In this case the cartilage, ligaments, bones and tendons.