Functions of the Skeletal System

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Functions of the Skeletal System

• Support - the body is kept in position by the
  muscles that attach to the skeleton.
• Protection- the flat bones protect the internal
  organs.
• Movement - provided by the joints
• Production of Blood - blood cells are produced in
  the red bone marrow in the centre of some bones,
  including the pelvis, ribs, vertebrae and stenum.
  The yellow bone marrow stores fat. The yellow
  bone marrow can convert to red bone marrow if the
  body needs additional blood production.
• Storage - Minerals are stored in the bone, mostly
  calcium and phosphorus.

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Skeletal System

• 360 bones in body when born
• 206 bones in body when you are about 10 or 20
• It gives us shape
• Protects our organs such as brain, heart, and
  lungs

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Skeletal system
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Bone Classification by Shape

• Long bones These are bones of the upper arms,
  the forearms, the thighs and the legs.
• They possess a long shaft that has a hollow core
  and is composed of a dense type of bone called
  compact bone in their cylindrical walls.
• The ends of long bones (epiphysis) form some of
  the most complex articulations the shoulders,
  elbows, wrists, hips, knees and ankles.
• The epiphysis is covered by cartilage
• The inside of the bone is spongy, called
  cancellous bone.

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Bone Classification by Shape

• Short bones cubed shaped and associated with
  smaller, more complex movements.
• Examples include carpals (small bones in the base
  of the hand) and tarsals (in the feet).

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Bone Classification by Shape

• Flat bones - these bones protect the internal
  organs and include the skull (cranium), ribs,
  scapula (shoulder blade), sternum (breast bone)
  and the pelvic girdle.

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Bones by Classification of Shape

• Irregular bones - these bones are irregular in
  shape and include the vertebrae and some facial
  bones.

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Bone Classification by Shape

• Sesamoid bones - these are small bones held
  within tendons and include the patella (knee
  cap). Cartilage separates the femur and the
  patella, and acts as a shock absorber. Sesamoid
  Bones serve to prevent friction where a tendon
  passes over a bone. They are small seed shaped
  bones which develop in vulnerable tendons. Rather
  than the tendon rubbing on bone, the sesamoid
  bone within the tendon rubs on the underlying
  bone.

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Osseus tissue - the structure of bone as a
substance

• The origin of osseus tissue. Our original
  "skeleton", which we form during the first 8
  weeks of gestation, is composed of hyaline
  cartilage (sometimes called cartilage models,)
  and, in our cranial area, fibrous membranes. So
  as an embryo, we have a soft, pliable skeleton
  that has no bone substance.

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Bone Growth

• At 6-7 weeks, the ossification process starts.
  When the baby is born, it has over 300 bones, but
  as the baby grows up, many bones fuse together
  and a fully grown adult has just 206 bones. When
  ossification occurs, cartilage is replaced with
  bone by laying down calcium. This process is
  known as calcification.

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Bone Growth

• During the growth phase, the bone grows from the
  growth plates (epiphyseal plates) which are
  situated at the end of the bone, just before the
  epiphysis (see the x-ray of a child's epiphyseal
  plates to the right). At the end of growth,
  between the ages of about 16 - 21, these
  epiphyseal plates turn to bone.

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Bone Growth

• Two types of cell involved in bone growth are
  osteoblasts and osteoclasts.
• Osteoblasts lay down new bone, whilst osteoclasts
  clear away the old bone.
• Growth occurs when the cells in the cartilage
  divide and push the older cartilage cells down
  towards the bone.
• The diaphysis ossifies first, followed by the
  epiphyses.

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What affects bone growth?

• Sufficient calcium
• Sufficient phosphorus
• Vitamins, especially vitamin D which is involved
  in the absorption of calcium
• The correct hormone balance, specifically
• Growth hormone from the pituitary gland
• Calcitonin from the thyroid gland. Calcitonin
  metabolises calcium and phosphorus.
• Parathormone - from the parathyroid gland -
  almost works in opposition to calcitonin to
  balance it out.
• The sex hormones, testosterone and oestrogen.

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What affects bone growth?

• The aging process. Women start to lose calcium
  from their bones at around the age of 40, and in
  men at around the age of 60, perhaps eventually
  leading to brittle bone disease - osteoporosis.
• Other causes of osteoporosis include prolonged
  treatment with cortisone steroids, anorexia
  nervosa and an inadequate diet, especially during
  pregnancy and breast feeding. However, it is
  possible to increase bone density by performing
  weight bearing exercise, taking calcium
  supplements (where the diet does not contain
  sufficient calcium) and, in women, estrogen
  replacement therapy.
• Protein formation in bone decreases with age,
  which can make bones more liable to fracture.

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Rat Anatomy

• Wash rat before making incisions
• Wash body cavity after making incisions
• Keep the rat in good condition
• You will use your own rat for your practical test
• Know the organs and functions

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Terminology

• Dorsal back or upper surface
• Ventral belly or lower surface
• Lateral the side
• Anterior the front or head end
• Posterior the hind or tail end
• Medial toward the midline of the body
• Proximal closer to the midline of the body
• Distal farther from the midline of the body
• Superficial near the surface
• Deep a distance below the surface

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External Features

• Hair
• Body regions
• Head, trunk, appendages, tail
• Vibrissae long hairs found behind the nose and
  above the eyes
• Guides the rat in darkness
• Ears, Eyes, Nares (nose), Mouth
• Reproductive structures
• Male scrotal sac (testes)
• Female mammary glands (6 pairs)
• Opening of excretory and digestive systems

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Digestive System

• Mouth
• Salivary glands
• Viscera
• All the organs of the body cavity
• Liver
• Stomach
• Pancreas
• Spleen
• Small intestine ileum, jejunum, duodenum
• Caecum junction of small and large intestine
• Large intestine aka colon

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Respiratory System

• Trachea
• Air travels down to reach the lungs
• Initial portion is the larynx
• Branches into right and left bronchi
• In the lungs, branch further into bronchioles
• Lungs
• Bronchioles carry air into air sacs
• Air sacs partitioned into alveoli
• Gas exchange occurs in alveoli
• Diaphragm
• Muscular wall separating the thoracic and
  abdominal cavities
• Diaphragm contracts upon inhalation, relaxes on
  exhalation

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Circulatory System

• The heart
• 4 chambers
• Right atrium receives blood returning from body
  by superior and inferior vena cava
• Right ventricle pumps blood via pulmonary
  artery to lungs
• Left atrium receives blood from lungs via
  pulmonary vein
• Left ventricle pumps blood to body via aorta
• Valves prevent backflow of blood
• Semilunar valves between aorta and left
  ventricle
• Atrioventricular valves between atriums and
  ventricles
• Chordae tendineae prevent valves from flapping
  back into atria

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Blood Vessels

• Veins blood toward the heart
• Vena cava
• Pulmonary vein
• Internal and external jugular veins
• Arteries blood away from the heart
• Aorta
• Divides into 3 branches
• Innominate artery
• Divides to form right subclavian and right common
  carotid
• Left carotid
• Left subclavian
• Continues dorsally, gives rise to other arteries
  thoracic, abdominal, femoral etc.

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