Outcome 3 - Bone Tissue Flashcards
What are some fun facts about bone tissue?
- each individual bone is considered an organ
- they are constantly being remodeled
- bone tissue makes up ~18% of your weight
What are the six major functions of bone?
- Support
- Protection
- Aid in movement
- Mineral homeostasis
- Blood cell production
- Triglyceride storage
What is the red bone marrow?
it is a network of reticular fibres that contains blood cells, adipocytes, fibroblasts and macrophages
What is yellow bone marrow?
it is made up of adipose cells (which store tg)
What are long bones?
bones that are greater in LENGTH than width
What are the parts of long bones?
- epiphysis (ends)
- diaphysis (‘body’)
- metaphysis/epiphyseal line (“growth plate” in peds)
- articular cartilage (that protects epiphysis)
- periosteum (2 layers (inner - very immature bone cells) covers the bone)
- medullary cavity (contains marrow; red in adolescents and yellow in adults)
What is the difference between epiphyseal plate and epiphyseal line?
plate is seen in GROWING bones while the line is seen in MATURE bones
- in the plate, you see. hyaline cartilage to allow diaphysis to grow while in line, the cartilage is ossified
What is the articular cartilage responsible for?
it is a thin later of hyaline cartilage that reduces friction, and absorbs shock
forms the joint with another bone
What is the periosteum?
it is a 2 layered tough sheath of connective tissue that covers the entire bone (except for where the joint is)
What are the two layers of periosteum?
- outer fibrous layer
- inner osteogenic layer
What is the difference between the fibrous and osteogenic layer?
Osteogenic - has osteogenic cells that differentiate to osteoblasts
fibrous - dense irregular connective tissue
Osteoblasts are bone forming cells that allow for the lengthening of bone not thickening. T/F
False!
osteoblasts are bone forming cells but they allow for the thickening of bone NOT LENGTHENING
How are periosteum attached to bone tissue?
by perforating fibres (aka Sharpey’s fibres) - bundles of collagen fibres extending from periosteum to ECM of bone
What is the medullary cavity?
it is the hollow space in the diaphysis that holds yellow bone marrow and blood vessels
- hollowness minimizes the weight of bone
What is the endosteum?
a thin, single layer of bone forming cells and some connective tissue that lines the medullary cavity
Remember that connective tissues are made up of extracellular matrix and cells.
What is in the ECM of bone tissue?
- 15% water, 30% collagen fibres, 55% crystallized mineral salts
- Ca3(PO4)2 + Ca(OH)2 –> Ca10(PO4)(OH)2 [hydroxyapatite] which hardens around collagen and crystallize for hardened tissues
What is calcification?
It is the process of tissue hardening due to deposition of salt minerals into collagen fibre network
What are the 4 types of cells that are present in bone tissue?
- osteogenic (osteoprogenitor) - bone stem cells; develop into osteoblasts
- osteoblasts - bone forming; forms bone ecm
- osteocytes - maintains bone tissue
- osteoclasts - WBCs lineage –> large, phagocytic cells to break down bone tissues
Where do you find osteogenic cells?
the inner portion of the periosteum, in the endosteum, and the canals that house blood vessels
What are osteogenic cells derived from?
mesenchyme cells
What is the responsibility of osteoblast cells?
- secreting collagen fibres and ECM
- start the calcification process in bone tissue
Where do you find osteoblast cells?
the outer surfaces surrounded by ecm which results in them becoming trapped deep in the bone tissue where they become osteocytes
What are osteocytes? Role?
primary, and mature cells found throughout the bone tissues
- maintain metabolism within cells
What are osteoclasts? Where are they found?
huge cells derived from monocytes; ruffled ends of the cell secretes acids and enzymes to break down bone tissue
- in the endosteum
What is resorption?
the breakdown of bone ECM for normal repair, development, growth and maintenance
What are the two types of bone classification?
1) compact (80%)
2) spongy (20%)
What parts make up compact bones?
- osteons
> concentric lamellae (circular plate of calcified bone matrix surrounding the central canal)
–> central canal (where blood vessels and nerves are) - interstitial lamellae (areas between neighbouring osteons)
> lacuna (‘lake’ that has osteocytes)
> canaliculi (branches that allow for communication, and routes for nutrients and waste)
Where are compact bones found?
beneath the periosteum and makes up the majority of the shaft of long bones
- connected to the periosteum by sharpey’s fibres
What are perforating canals (aka Volkman’s canals)?
- it contains blood and lymphatic vessels and nerves from the periosteum
- it allows for the connection between central canals and medullary cavity
What is different about spongy bones?
- they don’t have osteons but their concentric lamellae is found in the trabeculae*
- contain lamellae in irregular patterns of thin columns known as trabeculae
- major tissue in short, flat, sesamoid and irregular shaped bones
- lighter than compact bones
- support and protect red marrow
Where is bone marrow specifically found?
in the spaces between trabeculae
What is hematopoiesis?
the formation of blood cells
Where does hematopoiesis occur in infants? adults?
infants - everywhere
adults - spongy bones mainly in axial skeleton (trunk): HIP, PELVIS, RIBS, VERTEBRAE, STERNUM and PROXIMAL HUMERUS AND FEMUR
What is the nutrient artery?
the largest artery found in bones (mainly long bones), that carry blood to the bone tissue
- usually through the diaphysis (sometimes through metaphysis)
What is the difference in bone vasculature in adult bones and adolescent bones?
in adolescent bones, the nutrient artery does not feed pass the epiphyseal plate whereas in adult bones, the nutrient artery will supply blood to the epiphysis area as well!
