ch 6

• Bones are made up of 1/3 organic material ( collagen protein, ground substance, and gives flexibility) and 2/3 inorganic material ( mineral crystal of calcium and phosphate, gives hardness and strength )
• children with not enough mineral ( calcium ) develop Rickets
• Rickets: bones bend in lower extremities and can't support weight
• not enough protein in older adults leads to bones becoming more brittle ( like chalk ) and then fracture ( because it can't support the weight )
• bone cells have two categories : bone builders and bone destroyers
• Compact bone : dense outer layer
• Spongy bone : looser trabeculae with red bone marrow in the spaces
• Articular cartilage : hyaline cartilage ( slippery and hard ) found on ends of moving bones
• Periosteum : dense fibrous connective tissue on the outside surface ( slippery , for attachments )
• Endosteum : cellular layer lining hollow long bones
• Flat bones have red bone marrow in the spaces of spongy bone
• flat bones continue growth for your entire life
• Flat bones : noses, jaws lengthen
• ends of long bones are called epiphyses
• structure of epiphyses : articular cartilage covers joint ends, compact bone , spongy bone with red bone marrow ( red bone marrow makes blood cells )
• The shaft of long bones is called the diaphysis
• periosteum coves compact bone, endosperm, and yellow bone marrow in the medullary cavity
• nutrient artery and vein serve diaphysis
• metaphyseal vessels supply the epiphyseal cartilage
• periosteal vessels supply outer surface
• broken bones usually bleed a lot
• osteons give longitudinal strength to long bone to support weight
• Compact bone : outer smooth layer and parallel osteons
• spongy bone : inner tissue with red bone marrow and network of trabeculae
• Osteon: a functional unit in compact bone
• Spongy bone does not need a central canal as it is surrounded by red bone marrow with blood
• Bone development begins during the 6th week of embryonic development
• Can see ossification centers and progressing bone formation at 10 weeks
• at 16 weeks most of the bones of the adult skeleton can be identified
• ultrasound : sound waves are sent through the cutaneous membrane to the mother
• Waves penetrate into her abdominopelvic region and allow visualization of the living fetus
• ultrasound allow measurements of the head circumference and head to tail length
• two kinds of fetal bone development : flat bones and Long bones
• flat bones : develop flat connective tissue called mesenchyme, spread from center in one plane , covers the brain , develops ribs, develops sternum, scapula, pelvis, and intramembranous ossification
• long bones : develop from hyaline cartilage , diaphysis first, followed by secondary ossification centers at epiphyses, and stop growing in late childhood/young adulthood and endochondral ossification
• intramembraneous ossification: forms the first flat bone, skull, some facial bone, lower jaw, sternum, ribs, and central cervicle

  • bone forms from fibrous connective tissue
• osteoblasts enter fibrous CT and secrete osteoids then osteocytes and lamellar layers are formed
• the bony layer are woven into trabeculae . Blood vessels and red bone marrow enter the spaces and then osteoblasts line under the periosteum and generate compact bone osteons
• Interstitial growth : cartilage grows first and slowly and chondrocytes undergo mitosis to make 2 cells in one lacuna
• Interstitial growth: each cell produces cartilage matrix that pushes the cells apart , makes the cartilage get longer