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Biology Review: Skeletal System Definitions & Comparisons

Q1 / Define the following:
1- osteocytes: star-like cells that bones tissue composed of them. Secretes ossein wich is the solid Substance of bones.
2- Haversian Canal: is a central canal resulting from arrangement of osteocytes in form of acycle around it. discovered by Clapton Havers (1657-1702).
3- Periosteum: An external membrane covering the body bone which contains nerves and blood vessels to nourish the bone.
4- Foramen Magnum: its a big hole relatively found in the bottom of cranium, spinal cord pass through it.
5- Fontanelle: spaces located between the bones of head in the child's skull, and covered with afibrous cartilaginous tissue.
6- Apical Foramen: Its a hole located at the bottom of the tooth, branched dental nerve and branched blood vessels enter the tooth through it.
Q2 / Compare between Body and Two ends of bone:
Body of bone Two ends
1- It's consist of or( the type of tissue) is compact bone
2- The body is covered by an external Membrane Called Periosteum. Contains Nerves and blood Vessels to nourish the bone		 1- Two ends distinguished from the body of bone by being spongy.
2- Two ends is not surrounded by periosteium but surrounded by a smooth half-solid layer called cartilage..
Q4 / Give the causes of the following:
  • Presence of cartilaginous discs between the vertebral column: Enable the vertebral column to bend to different sides, facilitate the movement of vertebrae and prevent the friction of vertebrae.
  • Presence of the cartilaginous pieces at the front side of the real ribs: These pieces important in the process of respiration since they facilitate the movement of thoracic cage.
  • The lower limbs are longer than the upper limbs: Helps human in walking with wide spaces.
  • Dentine is a very solid substance in the structure of teeth: Because it contains calcic materials.

Q5 / Give the corresponding name for each of the following:
1. Ankle Tarsal
2. Hallux Big toe
3. Thumb Big finger
4. lower jaw Mandible
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