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level: Bone Development and Disorders

Questions and Answers List

level questions: Bone Development and Disorders

QuestionAnswer
Define ossificationossification is another word for osteogenesis and is bone tissue formation
What forms membrane bones?Membrane bones are formed directly from mesenchyme - they undergo intramembranous ossification
What forms other bones (not membranous bones)?Other bones are developed initially from hyaline cartilage - undergo endochondral ossification
Describe what is occuring in this photo, why is it important.This photo shows the very beginning of bone formation, the mesenchymal cells differentiate into osteoblasts and create an ossification center. We also see the formation of collagen fibers
Desribe what is occuring in this photo, why is it important?This photo shows the 2nd step in the bone formation process. The ossification center allows for the osteoblast to start secreting bone; new bone matrix. Some osteoblast become trapped inside the new bone and thus become osteoclasts.
Describe what is occuring in this photo, why is it important?This photo shows the third step of bone formation, the bone has been secreted but blood vessels begin to weave in and out + osteoids are laid in a random manner and this combination creates the trabeculae. Also the remaining mesenchyme cells condense and form the periosteum.
Describe what is occuring here, why is it important?some of the trabeculae hardens forming compact bone, however, some trabecula remains and the vascular tissue becomes red bone marrow - also in this particular picture
What bones go through Endochondral Ossification?All bones except some bones of the skill and clavicles go through endochondral ossification
Desribe Endochondral ossification?In endochondral ossification - the bones are modeled in hyaline cartilage - the bone begins to form late in the 2nd month of embryonic development - continues forming until early adulthood
What is occuring in this phase of Endochondral ossification?Because Endochondral ossification is where bones are modeled from hyaline cartilage, we see a bone collar form around the cartilage and an ossification center is created.
What is occuring in this phase of Endochondral ossification?The ossification center begins to form bone in the diaphysis region, cavities are developed
What is occuring in this phase of Endochondral ossification?Blood vessels begin to grow into the cavities and spongy bone begins to form
What is occuring in this phase of Endochondral ossification?Ossification continues and the diaphysis begins to elongate and the medullary cavity forms.
What do the epiphyseal plates allow?The epiphyseal plates allows for osteoblasts to continue producing bone, thus it is a growth plate. - pushes the epiphysis away from the diaphysis
What allows the epiphyseal plates to growcartilage cells form tall stacks (chondroblasts are located at the top of these stacks and divide quickly), the cartilage is organized for quick efficient growth
What signals the growth plate to produce more bone?Older chondrocytes send signals surrounding the matrix to calcify - they then die and disintegrate
What area is shown hereResting zone of bone
What area is shown here? What occurs here?Proliferation zone - cartilage cells are undergoing mitosis
What area is shown here? What occurs here?The Hypertrophic zone - older cartilage cells enlarge
What area is shown here? What occurs here?Calcification zone - matrix becomes calcified - older cartilage cells die - matrix begins deuterating
What area is shown here? What occurs here?Ossification zone - new bone is forming
During childhood and adolesence, what occurs to the new cartilage cells that were produced by the epiphyseal plate?The cartilage is replaced with bone connective tissue as quickly as it grows
What occurs to the epiphyseal plates as adolecence comes to an end?the epiphyseal plates become thinner - chondroblasts divide less often - cartilage stops growing, is replaced by bone tissue
When do long bones stop lengthening?Long bones stop lengthening when diaphysis and epiphysis fuse
How do bones widen (growing bones widen as they lenghten) ?Osteoblasts add bone tissue to the external surface of the diaphysis Osteoclasts remove bone from the internal surface of the diaphysis
Define appositonal growthappositional growth is the growth of a bone by addition of bone tissue to its surface.
What stimulates the growth at the epiphyseal plates?a growth hormone produced by the pituitary gland
What ensures that the skeleton retains its proper proportions?Thyroid hormone
What are the different types of fractures?Simple and compound fractures
How can one treat a fracturethrough reductions - either through closed reductions or open reductions
What first begins the healing process of a fracture?A fracture also causes not only the bone to break but the vessels thus the vessels bleed into the area and create a hematoma.
What occurs after a hematoma is created in the fractured area?Fibrous tissue and cartilage grows into the area (a internal and external callus is formed) New blood vessels are formed
What occurs to the fibrocartilageinous callus?the callus hardens... becomes a bony callus due to the osteoblasts
What occurs after the bony callus forms?Bone remodeling..... fracture is healed
What is a comminuted fracture?The fracture results in 3+ bone fragments -is common in elderly
What is a compression fracture?The fracture results in the bone being crushed - common in porous bones subjected to extreme trauma
What are the 2 fractures shown here?left picture: comminuted fracture (multiple pieces) right picture: compressed fracture (spine is tilting)
What is a spiral fracture?A spiral fracture is a ragged break that occurs when excessive twisting forces are applied to a bone - a common sports fracture
What is a epiphyseal fracture?an epiphyseal fracture is when the epiphyses separates from the diaphysis along the epiphyseal plate - tends to occur where cartilage cells are dying and calcification of the matrix is occurring
What 2 fractures are shown here?left picture: spiral fracture (caused by twisting) right picture: epiphyseal fracture (epiphyses seperates)
What is a depressed fracture?a depressed fracture typically occurs in the skull and is when the broken bone is pressed inward
What is a greenstick fracture?A greenstick fracture is when the bone breaks incompletely, one side of the shaft breaks and the other side is bended - common in children whose bones are more flexible
What are the 2 fractures shown here?left picture: depressed fracture (pressed inward) right picture: Greenstick fracture (not completely broken)
What is osteoporosis? Who does it affect the most? Where does it most often occur?A disease of aging - the weakening of the bone by the bone having a long bow mass - bone reabsorption is greater than bone deposition - occurs most often in women after mesopause - affects the trabecular bone the most
What occured to the bone on the bottom?the normal bone was affected by osteoporosis
When is the peak of bone mineral density?30
What occured to this person? Why did they become shorter?Osteoporosis caused compressing of the spine thus the spine bends
Define Osteomalaciaosteomalacia occurs in adults and is caused by bones being inadequately mineralized
Define RicketsRickets occurs in children, caused by a vitamin D deficiency
What is this child suffering from?Vitamin D defiency so Ricketts
What does mesenchyme produce?mesenchyme produces membranes and cartilage which then ossifies
Explain the ration of bone formation and bone reabsoprtion in different age groupsChildren and adolescents: Bone formation > bone reabsorption Young adults: bone formation = bone reabsorption Old age: bone reabsorption > bone formation