3 Skeletal System (cont.) # of bones:Adults 206Babies 300
4 Function of Bones Support for body and organs Protection for the brain, spinal cord, and vital organsMovementlevers for musclesMineral storage – Ca, PBlood cell formationoccurs in the marrow of bones
5 Division of Bones:Axial skeleton – skull, vertebral column, sternum, rib cageAppendicular skeleton –upper & lower limbs, shoulder, hip
14 Structure of Long BonePeriosteum- tough layer of connective tissueCompact bone- found beneath periosteumHaversian canals- network of tubes that run through compact bone & contain blood vessels and nerves.
15 Structure of Long Bone: Spongy bone- ends of long bones & middle of short, flat bones.Adds strength w/o mass!Within bones are cavities that contain a soft tissue called bone marrow.
16 Structure of Long Bone: Two types of bone marrow:Yellow bone marrow- made up of fat cellsRed bone marrow- produces red blood cells, white blood cells, & platelets
18 Bone Cells:Osteocytes- mature bone cells that are embedded in the matrixOsteoclasts- break down boneOsteoblasts- produce boneStop growing- late teens!Our Bones are continuously remodel throughout our lives.
19 OsteoporosisOsteoclast activity is faster than osteoblast activity!
21 Development of Bones:Skeleton of embryo almost entirely cartilage:Cartilage is a type of connective tissue that is made up of a network of protein fibers (both tough collagen & flexible elastin).
22 Development of Bone Cont’d: Cartilage does not contain blood vessels!Cartilage is replaced by bone during the process called ossification:Osteoblasts secrete mineral deposits that replace cartilage with bone.Osteoblasts surrounded by bone tissue – now osteocytes
23 Growth:Long bones contain growth plates called epiphyseal lines at either ends
24 Growth:Growth of cartilage at these plates causes the bones to lengthen.Gradually cartilage replaced by bone- a.k.a. ossificationLate adolescence/ early adulthood growth plates replaced by bone- stop growing!Cartilage in adults found:- nose, external ears, attach ribs to sternum