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Life Sciences
Grade 10
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SESSION 9: SUPPORT SYSTEMS IN ANIMALS 2
KEY CONCEPTS:
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Structure & function of bone, cartilage, tendons, ligaments
Joints – fixed, partly movable, synovial
Role of bones, joints, ligaments, tendons, muscle in locomotion
Muscle – antagonistic, myofibrils & contraction
Diseases affecting skeleton – rickets, osteoporosis, arthritis
X-PLANATION:
Bone Tissue:
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Connective tissue – rigid matrix
Function – support & protection
Suitability –
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Matrix and osteocytes arranged in concentric rings around the Haversion
Canal – strength
Matrix has white and elastic fibres – strength & flexibility
Canaliculi allows for communication between the osteocytes in the hard
matrix so they can receive nourishment etc.
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Cartilage:
Hyaline – strong & rubbery matrix reduces friction at joints
White fibrous –extremely tough with collagenous fibres to provide padding and act as
a shock absorber
Yellow elastic – elastic fibres provide flexibility in the ears (pinna) and epiglottis
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 Tendons : Are connective tissue responsible for attaching skeletal muscle to
bone
 Ligaments : Are tough fibrous connective tissue that attaches one bone to
another
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 Joints (articulations):
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Where parts of skeleton meet
Allows varying amounts of mobility
Classified by structure or function
There are three types of joints classified by the amount of movement they
allow:
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Immovable – sutures in cranium
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slightly movable – discs between vertebrae
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freely movable – synovial joints
Synovial Joints:
The joint capsule is an outer sleeve that protects and holds the knee together.
The synovial membrane:
Lines the capsule and secretes synovial fluid – a liquid which lubricates the joint,
allowing it to move freely.
Hyaline cartilage lines the ends of the bones reducing friction there
A typical synovial joint:
In ball and socket joints, the rounded end of one bone fits inside a cup-shaped
ending on another bone
Ball and socket joints allow movement in all directions and also rotation.
The most mobile joints in the body are ball and socket joints.
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Examples: Shoulders and hips.
Pivot joints have a ring of bone that fits over a bone protrusion, around which it can
rotate.
These joints only allow rotation.
Examples: The joint between the atlas and axis in the neck which allows you to
shake your head.
Atlas
Axis
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Hinge joints – as their name suggests – only allow forwards and backwards
movement.
Examples: The knee and elbow.
Gliding joints have two flat faces of bone that slide over one another.
They allow a tiny bit of movement in all directions.
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Structure of Skeletal Muscle:
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Muscle Contraction:
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Each muscle fibre consists of smaller units called myofibrils, which consist of
protein filaments, myosin and actin
During contraction, the actin filaments slide between the myosin filaments
The sarcomeres therefore become shorter
Each muscle fibre is made up of many sarcomeres
So when they all shorten together, the whole muscle fibre contracts
Types of Body Movement:
Flexion:
Extension:
Bringing two parts of a limb together - bending at the joint.
Moving two parts of a limb away from each other - straightening at
the joint.
Abduction:
Moving limbs away from the centre of the body.
Adduction:
Moving limbs towards the centre of the body.
Circumduction: The movement of a limb around a joint.
How muscles work:
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Muscles can only pull. To make a joint move in two directions, you need two
muscles that can pull in opposite directions.
Antagonistic muscles are pairs of muscles that work against each other. One
muscle contracts (agonist, or prime mover) while the other one relaxes
(antagonist) and vice versa.
The origin is where the muscle joins the fixed bone. The insertion is where it
joins the moving bone. On contraction, the insertion moves towards the origin.
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Diseases Affecting the Skeletal System:
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Fracture is a break of the bone
Simple or Complex fracture
Regrowth of bone:
– Spongy bone forms in first few days
– Blood vessels regrow and spongy bone hardens
– Full healing takes 1-2 months
Rickets in Children:
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Disease of children due to a lack of vitamin D.
Calcium is not deposited in bones.
Bones become soft.
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Bowing of the bones, and other deformities occur:
Osteomalacia in Adults:
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“Rickets” of adults.
Due to a lack of vitamin D.
Calcium is not deposited in the bones.
Bones become brittle.
Osteoporosis:
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Bone reabsorption is greater than bone deposition.
Decline in bone density
Due to any of the following:
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Lack of oestrogen in women.
Lack of exercise to stress the bones.
Inadequate intake of calcium and phosphorus.
Abnormalities of vitamin D metabolism.
Loss of muscle mass.
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How much calcium do I need?
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Children and teenagers between the ages of 9 and 18 should aim for 1,300
mg per day. Each 8-oz glass of milk and each cup of yogurt has about 300 mg
of calcium.
Adults 19 to 50 years of age should aim for 1,000 mg per day. Adults 50+
need 1,200 mg per day.
Osteoarthritis:
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chronic inflammation of articular cartilage
can be normal age-dependent change
can also be pathology due to:
 Age-related changes
 decrease blood supply
 trauma
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Gout:
Gout is a disease that results from an overload of uric acid in the body. This overload
of uric acid leads to the formation of tiny crystals of urate that deposit in tissues of
the body, especially the joints. When crystals form in the joints it causes recurring
attacks of joint inflammation (arthritis). Chronic gout can also lead to deposits of hard
lumps of uric acid in and around the joints and may cause joint destruction,
decreased kidney function, and kidney stones.
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X-AMPLE QUESTIONS:
Questions 1:
Study the diagram of a synovial joint and answer the questions:
1.1 Provide labels for A and B.
1.2 Write the letter of two labels that reduce friction at the joint.
1.3 What is the purpose of ligaments at the joint?
Question 2:
Study the diagram and answer the questions:
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2.1 Draw a table to indicate the different joints illustrated above and the degree of
movement offered by each.
Question 3:
Classify the following as immovable, slightly movable or freely movable joints.
a)
b)
c)
Question 4:
Explain how skeletal muscle contracts.
Question 5:
Discuss the role of bones, muscles and tendons in movement.
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