Paragraph 5.1-5.6

Summary biology unit 5: Support and locomotion

5.1 The human skeleton

• Endoskeletons are skeletons inside the body
• Human skeleton has 206 bones
• The head bones belong to the skull
• The skull is supported by the backbone
• Rib cage:
  • Thoracic vertebrae
  • Ribs
  • Breast bone
  • Pectoral girdle:
    • Shoulder blades
    • Collar bones
    • Pelvic girdle
      • Pelvis (attached to backbone
      • Limbs:
        • Arms
        • Legs
        • Skull has fused joints
        • The skull of a baby is not completely joined. These are called fontanelles
        • At the age of 2 the fontanelles close.                                                                                     
        • Functions of a skeleton:
          • Support
          • Movement
            • Muscles are attached to the bones
            • Most of the bones are in such a position that they allow movement
• Protection
• Shape
•  

5.2: The skeletons of mammals

• Plantigrades: walk on the whole sole of his feet when he walks. E.g.
  • Bears
  • Humans
  • Digitigrades: walk on their toes when he walks. E.g.
    • Cats
    • Dogs
    • Unguligrades: walk on the tip of their toes. E.g.
      • Horses
      • Cows

5.3 Bone and cartilage

• Your body is supported by two different types of tissue:
  • Bone tissue
  • Cartilage tissue
  • Both contain extracellular material between the cells
  • Cartilage tissue is composed of cells clustered inside the extracellular material
  • It’s constructed in such a way that it’s strong and flexible
  • Where can cartilage be found? (adults)
    • Ears
    • Nose
    • Between the vertebrae
    • In joints
    • Bone tissue is composed of cells surrounding tiny canals. These canals contain blood vessels
    • The extracellular material is much tougher than that of cartilage tissue
    • The extracellular material in bone tissue is composed of:
      • Calcium phosphate
        • Strong and rigid
        • Disappears in hydrochloric acid
• Collagen
  • Flexible
  • Disappears in a flame
  • This makes it hard without being brittle
  • Collagen is replaced by calcium phosphate as we grow older

5.4 Joints

• A place where two bones meet is called a joint. Muscles on either side make movement possible
• We have four types of joints:
  • Fused joints
    • Immovable
    • E.g. sacrum, coccyx
• Sutures
  • Immovable
  • E.g skull
• Cartilaginous joint
  • Able to move slightly
  • Also function as shock absorbers
  • E.g. vertebrae
  • E.g. ribs
• Synovial joint
  • moveable
  • most common
  • found mainly in limbs
  • e.g. phalanges
  • we have three types of synovial joints:
    • ball-and-socket joint
      • e.g. shoulder joint
      • can move in all directions
      • hinge joint
        • e.g. between two phalanges
        • can move in one direction
        • pivot joint
          • e.g. between ulna and radius
          • a bone rotates around another
          • The end of a bone is covered by a slippery layer of cartilage. This provides a smooth surface for easy gliding and it prevents the bones wearing away. It also acts like a shock absorber
          • The synovial membrane produces an oily liquid called synovial fluid, which makes movement easy
          • The bones are held together by the synovial membrane
          • Ligaments often stretch across the joints to connect different bones

5.5 Muscles

• Muscles make your body move by pulling on the bones
• The muscular system is composed of around 650 muscles
• Muscles are attached to bones by fibres called tendons
• The site where a tendon is attached to the bone is called an attachment site
• Muscles are able to contract, tendons aren’t
• When a muscle contract, it gets shorter and thicker. When it shortens, it pulls on what it is attached to. This is how movement occurs
• When a muscle is on its rest, it’s long and thin
• Antagonistic muscles are muscles that have to work in opposite ways
  • You have a flexor and an extensor muscle. E.g. flexor: biceps, extensor: triceps
  • The biceps contract to bend the arm
  • Muscles can only push, they cannot push. Therefore, they have to work in pairs
  • When you want to straighten your arm, you need the triceps (extensor muscle) must contract and the biceps will relax to let this happen

5.6 Posture and movement

• Some people have a bad posture. This can cause backache
• The backbone has a double S form
• This form is supported by the muscles of the backbone which are connected to the vertebrae
• The discs of cartilage between the vertebrae are called intervertebral discs
• They’re shock absorbers
• If you have bad posture and repeatedly hold yourself in the wrong position, the backbone can get in the wrong position
• Because of that one side of the backbone gets overloaded. Some muscles have to work harder because of this overload. The intervertebral discs also become overloaded
• In time they can lose their flexibility
• The correct way to sit straight up is:
  • With an angle of 90° between the fibula and the thighbone
  • If you put your arm on the table there must be an angle of 90° with your upper body
  • When you lift (heavy) things your backbone should be in the double S form as well
  • Regular physical exercise is good for your health
  • It’ll improve your fitness
  • With untrained muscles the risk of an injury is bigger than when your muscles are trained