Bones IA (+ Flashcards
1
Q
Bone functions
A
- Weight bearing/support
- Protection (e.g. skull: brain, vertebrae: spinal cord)
- Mineral store
- Blood formation (red bone marrow)
2
Q
Gross anatomy of bones
A
- Compact bone
- Spongy (trabecular) bone
- Blood vessels
- Medullary cavity
- Bone marrow
- Membranes:
–Periosteum
–Endosteum
3
Q
Osteons/haversian systems
A
- Compact bone organised in circular structures (osteons/Haversian systems)
- Central Haversian canal and horizontal perforating/Volkmann’s canals
- Osteocytes and concentric rings of bone matrix (lamellae) around Haversian canal
4
Q
Spongy bone
A
- Also called cancellous or trabecular bone or diploe
- Less dense than compact bone
- Network of lamellated trabeculae filled with bone marrow (no Harversion systems!)
- Orientation of trabeculae reflect main directions of mechanical forces
5
Q
Long bone
A
- long bones have greater length than width, consist of a shaft and a variable number of extremities or epiphyses (ends), and are slightly curved for strength.
- Long bones consist mostly of compact bone tissue in their diaphyses but have considerable amounts of spongy bone tissue in their epiphyses.
- e.g femur (thigh bone), tibia and fibula (leg bones), humerus (arm bone), ulna and radius (forearm bones), and phalanges (finger and toe bones)
6
Q
Short bones
A
Short bones are somewhat cube-shaped and are nearly equal in length and width. They consist of spongy bone tissue except at the surface, which has a thin layer of compact bone tissue.
Examples of short bones are most carpal (wrist) bones and most tarsal (ankle) bones.
7
Q
Flat bones
A
- Flat bones are generally thin and composed of two nearly parallel plates of compact bone tissue enclosing a layer of spongy bone tissue.
- Flat bones afford considerable protection and provide extensive areas for muscle attachment. Flat bones include the cranial bones, which protect the brain; the sternum (breastbone) and ribs, which protect organs in the thorax; and the scapulae (shoulder blades).
8
Q
Irregular bones
A
Irregular bones have complex shapes and cannot be grouped into any of the categories. They vary in the amount of spongy and compact bone present. Such bones include the
vertebrae (backbones), hip bones, certain facial bones, and the calcaneus.
9
Q
Sesamoid
A
- Sesamoid bones (develop in certain tendons where there is considerable friction, tension, and physical stress, such as the palms and soles.
- Functionally, sesamoid bones protect tendons from excessive wear andtear, and they often change the direction of pull of a tendon, which
- improves the mechanical advantage at a joint.
10
Q
Sutural bone
A
Sutural bones are small bones located in sutures (joints) between certain cranial bones
11
Q
List the 6 types of bones
A
- Flat
- Short
- Sesamoid
- Sutural
- Irregular
- Long
12
Q
Endochondral ossification
A
- Development of the periosteum: mesenchyme (embryonic tissue) at the periphery of the bone develops into the periosteum.
- Growth of cartilage model: growth occurs by cell division of chondrocytes (a cell which has secreted the matrix of cartilage and become embedded in it)
- Development of 1• ossification center: in this region of the diaphysis, bone tissue has replaced most of the cartilage
- Development of the medullary cavity: bone breakdown by _osteo*c*lasts_ forms the medullary cavity
- Development of 2• ossification centers: these occur in the epiphyses of the bone
- Formation of articular cartilage and epiphyseal plate: both structures consist of hyaline cartilage.
- 12-week fetus. The red areas represent bones that are forming (calcified). Clear areas represent uncalcified cartilage
13
Q
Intramembranous ossification
A
- Development of ossification center: _osteo*b*lasts_ secrete organic extracellular matrix.
- Calcification: calcium and other mineral salts are deposited and extracellular matrix calcifies hardens.
- Formation of trabeculae: extracellular matrix develops into trabeculae that fuse to form spongy bone.
- Development of the periosteum: mesenchyme at the periphery of the bone develops into the periosteum.
14
Q
Bone composition
A
Minerals (hydroxyapatite)
- Make bone stiff & able to support structures
- High strength under compression (like concrete)
Collagen
- gives bone some flexibility & reduces risk of fracture
- High strength under tension (like steel)
15
Q
Osteoprogenitor
A
- Unspecialized bone stem cells derived from mesenchyme, the tissue from which almost all connective tissues are formed.
- They are the only bone cells to undergo cell division; the resulting cells develop into osteoblasts.
- Osteoprogenitor cells are found along the inner portion of the periosteum, in the endosteum, and in the canals within bone that contain blood vessels.
16
Q
Osteoblasts
A
- Bone-building cells.
- They synthesize and secrete collagen fibers and other organic components needed to build the extracellular matrix of bone tissue, and they initiate calcification
- As osteoblasts surround themselves with extracellular matrix, they become trapped in their secretions and become osteocytes.
Note: The ending -blast in the name of a bone cell or any other connective tissue cell means that the cell secretes extracellular matrix.)
17
Q
Osteocytes
A
- These mature bone cells, are the main cells in bone tissue and maintain its daily metabolism, such as the exchange of nutrients and wastes with the blood.
- Like osteoblasts, osteocytes do not undergo cell division.
Note: The ending -cyte in the name of a bone cell or any other tissue cell means that the cell maintains and monitors the tissue
18
Q
Osteoclasts
A
- Osteoclasts are huge cells derived from the fusion of many monocytes (a type of white blood cell) and are concentrated in the endosteum.
- On the side of the cell that faces the bone surface, the osteoclast’s plasma membrane is deeply folded into a ruffled border.
- Here they release powerful lysosomal enzymes and acids that digest the protein and mineral components of the underlying extracellular bone matrix.
- This breakdown of bone extracellular matrix, termed resorption, is part of the normal development, maintenance, and repair of bone.
Note: The ending -clast means that the cell breaks down extracellular matrix.
19
Q
Extracellular matrix
A
- Mainly minerals, protein (collagen) & water
- Modified Type I collagen fibres
- Strongly cross-linked & large ‘gaps’ within fibres
- Gaps provide space for hydroxyapatite crystals
- Collagen fibre orientation linked to mechanical forces
23
Q
Disorders
A
- Osteoporosis: Resorption rate exceeds formation
- Paget disease: Increase in resoprtion and formation
- Osteopetrosis: Decrease in resporoption
