Flat bone

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Flat bone_table_infobox_0

Flat boneFlat bone_header_cell_0_0_0
DetailsFlat bone_header_cell_0_1_0
IdentifiersFlat bone_header_cell_0_2_0
LatinFlat bone_header_cell_0_3_0 os planumFlat bone_cell_0_3_1
TA98Flat bone_header_cell_0_4_0 Flat bone_cell_0_4_1
TA2Flat bone_header_cell_0_5_0 Flat bone_cell_0_5_1
FMAFlat bone_header_cell_0_6_0 Flat bone_cell_0_6_1

Flat bones are bones whose principal function is either extensive protection or the provision of broad surfaces for muscular attachment. Flat bone_sentence_0

These bones are expanded into broad, flat plates, as in the cranium (skull), the ilium (pelvis), sternum and the rib cage. Flat bone_sentence_1

The flat bones are: the occipital, parietal, frontal, nasal, lacrimal, vomer, hip bone (coxal bone), sternum, ribs, and scapulae. Flat bone_sentence_2

In the cranial bones, the layers of compact tissue are familiarly known as the tables of the skull; the outer one is thick and tough; the inner is thin, dense, and brittle, and hence is termed the vitreous (glass-like) table. Flat bone_sentence_3

These bones are composed of two thin layers of compact bone enclosing between them a variable quantity of cancellous bone, which is the location of red bone marrow. Flat bone_sentence_4

In an adult, most red blood cells are formed in flat bones. Flat bone_sentence_5

The intervening cancellous tissue is called the diploë, and this, in the nasal region of the skull, becomes absorbed so as to leave spaces filled with air–the paranasal sinuses between the two tables. Flat bone_sentence_6

Ossification in flat bones Flat bone_section_0

Ossification is started by the formation of layers of undifferentiated connective tissue that hold the area where the flat bone is to come. Flat bone_sentence_7

On a baby, those spots are known as fontanelles. Flat bone_sentence_8

The fontanelles contain connective tissue stem cells, which form into osteoblasts, which secrete calcium phosphate into a matrix of canals. Flat bone_sentence_9

They form a ring in between the membranes, and begin to expand outwards. Flat bone_sentence_10

As they expand they make a bony matrix. Flat bone_sentence_11

This hardened matrix forms the body of the bone. Flat bone_sentence_12

Since flat bones are usually thinner than the long bones, they only have red bone marrow, rather than both red and yellow bone marrow (yellow bone marrow being made up of mostly fat). Flat bone_sentence_13

The bone marrow fills the space in the ring of osteoblasts, and eventually fills the bony matrix. Flat bone_sentence_14

After the bone is completely ossified, the osteoblasts retract their calcium phosphate secreting tendrils, leaving tiny canals in the bony matrix, known as canaliculi. Flat bone_sentence_15

These canaliculi provide the nutrients needed for the newly transformed osteoblasts, which are now called osteocytes. Flat bone_sentence_16

These cells are responsible for the general maintenance of the bone. Flat bone_sentence_17

A third type of bone cell found in flat bones is called an osteoclast, which destroys the bone using enzymes. Flat bone_sentence_18

There are three reasons that osteoclasts are normally used: the first is for the reparation of bones after a break. Flat bone_sentence_19

They destroy sections of bone that protrude or make reformation difficult. Flat bone_sentence_20

They are also used to obtain necessary calcium that osteoclasts are used is for growing. Flat bone_sentence_21

As the bone grows, its shape changes. Flat bone_sentence_22

The osteoclasts dissolve the part of the bone that must change. Flat bone_sentence_23

Additional images Flat bone_section_1

Flat bone_unordered_list_0

  • Flat bone_item_0_0
  • Flat bone_item_0_1
  • Flat bone_item_0_2

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Flat bone.