HTHSCI 1H06 Lecture Notes - Lecture 15: Limb Bud, Synovial Joint, Synovial Membrane
20 Dec 2018
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Document Summary
Embryo at 5 weeks starts making a cartilage model from which bones will develop. Chondroblasts in mesenchyme secrete ecm: collagen, proteoglycans, hyalamic acid. By 6 weeks, limb bud has increased in size and there are cartilage models of bones making up upper and lower limbs. Cartilage models form basis of making bone which attracts ca2+ to ossify them. Chondrocytes allow calcium from blood to enter ecm of tissues and bone becomes hard. Begins in middle of diaphysis and grows towards ends of bone. All grows outwards so eventually ossification centers of diaphysis and epiphysis meet. Diaphysis medulla hollowed out and replaced with fat (yellow marrow) Epiphysis hollowed out and replaced with red marrow with rich blood supply. Eventually form osteocytes that excrete ecm that will become mineralized. Located in lacuna where they communicate with one another through these processes. Ecm in bone contains collagen and calcium phosphate (hydroxyapatite) which is a component in mineralizing the bone.
