9.+Bone+____+3421++Prab+copy

9.+Bone+____+3421++Prab+copy - SKELETON The skeleton is...

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SKELETON The skeleton is more than a rigid scaffold for protection and support. It also allows man to be upright with hands freed from locomotion. Height allows for better hearing, sight, and smell. It also allows for greater speed-try running on all fours! Arboreal characteristics : opposable thumb, brachiation, binocular vision, bipedal locomotion. It consists of two types of tissue (cartilage and bone). Some functions of the skeleton would be as follows: a. Protection b. Support c. Allows for growth d. Allows for movement (leverage) e. Housing for blood forming red marrow ( red and some white blood cells, and platelets). f. Reservoir of calcium Bone is formed by: (1) direct ossification of embryonic connective tissue model  (intramembranous ossification) or by (2) replacement of hyaline cartilage model  (endochondral ossification). Intramembranous ossification takes place in the membrane  or dermal bones of the skull, while endochondral ossification is characteristic of the bones  of the trunk and extremities.
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(1) Dermal Bone (2) Endochondrial Bone TWO BONE TYPES Periosteum Compact bone Spongy bone
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TYPE OF BONE-Shape; a) Long bones-ex. femur, humerus, b) short bones (box-like)-ex. Carpels and tarsals,c) flat bones-ex. Roof of skull, ribs, scapula d) Irregular bones-ex, vertebrae, e) sesmoid bones- in tendons like patella. MESENCHYME OSTEOCYTE (mature bone cell, nonfunctional) OSTEOBLAST (active bone forming cells) OSTEOCLAST (multinucleated) (breaks down bone) CHONDROCYTES (active cartilage cells) Undifferentiated ****ALL BONES ARE MADE OF THE SAME MATERIAL,  EVEN THOUGH THEY MAY LOOK DIFFERENT Differentiation of Cells
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THE VERTEBRATE EMBRYONIC SKELETON CONSISTS OF TWO BASIC TYPES OF BONE: (1) Fibrous membranes which are later ossified to form membrane/dermal bones (intramembraneous bone). Ex. skull (2) Hyaline cartilage which will later ossify to form Endochondrial/cartilage bone. Ex. appendages Ossification (bone formation) starts at about 6-7 wks in embryonic life of humans and continues throughout adulthood. Bone ossification (osteoblast activity) exceeds bone re-absorption (osteoclast activity) until about age 25, then the rates become equal, and finally with old age re-absorption exceeds formation. The two patterns of bone formation do not lead to formation of different kinds of bones - all bone is similar.
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         (1) FORMATION OF MEMBRANEOUS/DERMAL BONE A) Blood vessels migrate in and increase vascularity of connective tissue model.  B) Active proliferation of mesenchymal cells occurs via mitosis. Mesenchymal cells
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