Panopto 18/19 Flashcards
What is the chemical nature of bone?
Organic and inorganic
Organic portion: cells + matrix (osteoid)
Inorganic portion: (calcium and phosphate)
Osteoid made up of?
fibers and ground substance, but the primary component is fibers. 60% of the substance is collagen type one, and the remaining 40% is ground substance. ground substance is made of sulfated GAGs.
Ossification
transforms the osteoid into bone
is extracellular fluid the same as extracellular matrix?
Extracellular fluid is NOT the extracellular matrix, This fluid keeps the matrix wet and is the source of calcium and phosphate, its the way all of our cells receive nutrients and oxygen, carries away cellular waste like CO2
Osteoblasts
cells that make osteoid and initiate the formation of hydroxyapatite. They do this by secreting a structure called the matrix vesicle. They secrete the matrix vesicle into the matrix, and it is membrane bound. It contains the enzyme alkaline phosphatase. This kind of secretion is unusual. Usually in a secretion, the contents are exocytosis. This vesicle initially is small, about 50 nm; gradually, calcium phosphate accumulates inside and the vesicle gets large, as large as 250 nm. Chemical reactions occurs inside the vesicle resulting in hydroxyapatite, at some point the vesicle membrane is ruptured
Bone formation (genesis): when does it start and end?
forming of our skeleton, we only do once but its a long process, begins in utero and is continuous until bone stops growing (about 20 years or so)
osteoblasts
Making of osteoid, the cytoplasm of these cells are said to be PAS positive, which is an indicator of carbohydrate (GAGs). These will eventually be secreted and become a component of ground substance
Bone remodeling when does it start and end
maintenance process, as bone tissue gets old and broken down it is replaced with new tissue. begins early in life, and happens while bones are growing . When genesis ends bone maintenance will continue for the rest of our lives
Osteoprogenitor cells
arise from the mesenchyme (connective tissue stem cells) we find them on all surfaces of the bone both inside and the outside, even in the small spaces of haversian canals and spongy bone. Divides into an osteoblast.
osteocytes
mature bone cells that are trapped within the matrix, and each one lives in a small space called a lacuna. When they were actively secreting matrix, they were called osteoblasts. Have a low activity level, but they can become active and perform small repairs. Their function is maintenance.
What are intramembranous bones?
form via ossifications of the embryological membrane, flat bones found in the face, cranium, and clavicle. Made of both compact and spongy bone
What’s another word for intramembranous bone?
membrane bones or dermal bones
what are endochondral bones?
Arise from a cartilaginous precursor and are gradually transformed into bone. Composed of compact bone and spongy bone.
What are the two types of bones based on embryological origin?
intramembranous and endochondral bones
story of intramembranous bone
Begins about 4 weeks post conception, we get the appearance of mesenchyme cells; some of these cells will migrate to locations in the embryo where the intramembranous bones will form, form embryological membrane (8 weeks post conception): A sheet of cells that are roughly in the shape of the bone they are going to be forming (usually flat bones). The mesenchyme cells divide and differentiate to get the formation of osteoblasts. Over time, compact and spongy bones are made due to the activity of these osteoblasts. At the same time, your blood vessels invade this developing bone tissue and form red marrow in the spaces of spongy bone (diploe). Mesenchymal cells form osteoprogenitor cells, which go on to form osteoblasts. When the osteoblasts produce a layer of fluid that’s on the outer surface of a flat bone, the bone will get larger (appositional growth)
