Chapter 7 The Skeletal System

Functions of Bone SUPPORT - PROTECTION LEVERAGE STORAGE HEMATOPOIESIS

Funny Bone Facts Bone is the 2nd hardest substance in the body, after ___________ Capable of ________-__________ if aligned and kept still! ________________________ = mineralization or hardening of bone Osteoblasts become trapped in their _______________ due to the bone that they have made Remember, when they are done making bone, their name changes Osteocytes communicate with each other via channels called ____________________

Bone Structure Two main types of bone: _________________________- Light and spongy inner layer of bone. Consists of tiny spicules with bone marrow between them. Helps reduce the weight of bone; spicules are arranged to withstand the forces that bone is subjected to _________________________- Heavy and dense outer layer of all bones Composed of Haversian Systems

Haversian Systems Concentric layers of bone arranged around a central ___________________ _________________. ___________________ _____________- tiny channels in the bone matrix that vessels pass through. They are horizontal, whereas Haversion canals are vertical. 5

Bone Structure 3 types of bone cells: ________________________- cells that secrete the matrix of bone ________________________- inactive cells that have become trapped in the matrix they have created ________________________- cells that remodel bone by eating it away from places it is not needed. They allow the body to utilize the calcium that was stored in bone.

_________________________- fibrous membrane that covers the outside of bone (except at the joint) _________________________- fibrous membrane that lines the hollow interior surface of bones. ____________________ - the shaft of long bones ____________________ - the ends of long bones Bone Structure

Bone Formation Bone is formed in 2 ways: __________________________ (cartilage bone formation) Grows into and replaces cartilage How most bones develop __________________________ (membrane bone formation) Develops from fibrous tissue membranes Bone formation and growth is stimulated by GROWTH HORMONE from the _________________ gland in the brain.

Endochondral Bone Formation Cartilage to bone formation cartilage template is replaced by bone Starts in the __________________ growth center Cartilage rods in the ___________________ (shaft) of long bones are gradually replaced by bone. __________________ growth centers develop in ________________ (ends) of bones Endochondral Bone Formation

Growth plates (epiphyseal plates) At the time of birth, cartilage remains at each end of long bones between __________________ and __________________. Sites of creation of new bone that allows bone to lengthen as animal grows. ______________________ is created on epiphyseal side while _______________ is created on diaphyseal side. Growth plates (epiphyseal plates)

Growth plates (epiphyseal plates) When bone reaches full length, all cartilage is replaced by bone and plates “close”. Remodeling may take place but bone will not get any longer. Young animals may have epiphyseal ______________ because this area is weaker than rest of bone.

Intramembranous Bone Formation Occurs only in _______ _________ bones Bone forms in the fibrous tissue that covers the brain of the ______________. There is no cartilage intermediary.

Bone Shapes Long Bones Short Bones Flat Bones Irregular Bones

Long Bones Longer than they are wide. There is a proximal epiphysis and distal epiphysis with the diaphysis in between. EXAMPLES: __________________________________________________________

Short Bones Shaped like cubes. Have a core of cancellous bone covered by compact bone. EXAMPLES: _____________________________

Flat Bones Thin and flat bones Consists of two layers of compact bone separated by cancellous bone. EXAMPLES: __________________________________________

Irregular Bones Miscellaneous bones that do not fit into another category. May have characteristics of more than one category. EXAMPLES: ___________________________ _____________ - is largest sesamoid bone in body.

Bone Marrow Fills the spaces within center of long bones & within cancellous bone _______________ bone marrow ________________________- the process of forming new blood cells. Majority of bone marrow in young animals __________________ bone marrow Consists primarily of __________________ connective tissue. Majority of bone marrow in adult animals Does not produce blood cells but can revert to red marrow if needed.