1
Q
Functions of Bone and Skeletal System
A
- Support
- Protection
- Assistance in movement
- Mineral Storage and Release
- Blood cell production
- Triglyceride storage
2
Q
Long bones
A
- greater length than width
- have a diaphysis (shaft) and epiphyses (ends)
- curved bone to absorb stress of body’s weight
- composed mostly of compact bone tissue but also contains spongy bone tissue
- examples include: humorous, femur, metacarpals, phalanges etc
3
Q
Short Bones
A
- somewhat cube shaped and nearly equal in length, width and depth
- consists of spongey bone except for thin layer of compact bone
- examples: carpals and most tarsals
4
Q
Flat Bones
A
- generally think and composed of 2 nearly parallel plates of compact bone enclosing a layer of spongy bone
- layers of compact bone are called internal and external tables
- in cranial bones, the spongey bones is referred to as diploe
- afford considerable protection and provide extensive areas for muscle attachment
- examples: cranial bones, sternum, ribs, and scapulae
5
Q
Irregular Bones
A
- have complex shapes
- vary in amounts of spongey bone and compact bone
- examples: vertebraa, certain facial bones, and calcaneous
6
Q
Sesamoid Bones
A
- develop in certain tendons where there is considerable friction, compression and physical stress
- not always completely ossified
- vary in number from person to person
- protect tendons from excessive wear and tear
- can alter direction or pull of a tendon which improves mechanical advantage at a joint
7
Q
Diaphysis
A
- bones shaft or body
- long cylindrical main portion of the bone
8
Q
Epiphyses
A
- aka extremities
- proximal and distal ends of the bone
9
Q
Metaphyses
A
- regions between the diaphysis and epiphyses
- in a growing bone each metaphysis contains an epiphesial growth plate in a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length
- when bone growth stops, the cartilage in the epiphyseal plate is replaced by bone and is then known as epiphyseal line
10
Q
Articulate Cartilage
A
- thin layer of cartilage covering the part of the epiphysis where the bone forms and articulation joint with another bone
- reduces friction and absorbs shock at freely moveable joints
- lack perichondrium and blood vessels, so repair of damage is limited
11
Q
Periosteum
A
- tough connective tissue sheath that is associated with blood supply that surrounds the bone surface where it is not covered by articulate cartilage
- composed of out fibrous layer of dense irregular connective tissue and inner osteogenic later that consists of cells
- some cells enable the bone to grow in thickness but not in length
- protects bone
- assists in fracture repair
- helps nourish bone tissue
- serves as attachment point for ligaments and tendons
- attached to underlying bone by perforating fibers - thick bundles of collagen that extend from periosteum into the bone extra cellular matrix
12
Q
Medullary Cavity
A
- also called marrow cavity
- hollow cylindrical space within diaphysis
- contains fatty yellow bone marrow and numerous blood vessels in adults
- minimizes the weight of the bone by reducing the dense bones material where it is needed least
- long bones tubular design provides maximum strength with minimum weight
13
Q
Endosteum
A
- thin membrane than lines the medullary cavity
- contains single layer of bone-forming cells and a small amount of connective tissue
14
Q
Bone Surface Marking - Depressions and Openings
A
- Fissure
- Foramen
- Fossa
- Sulcus
- Meatus
15
Q
Bone Surface Markings - Processes
A
- Condyle
- Facet
- Crest
- Epicondyle
- Line
- Spinous Process
- Trochanter
- Tubercle
- Tuberosity
16
Q
Fissure
A
- narrow slit between adjacent parts of Bones through which blood vessels or nerves pass
- eg: superiors orbital tissue of sphenoid bone
17
Q
Foramen
A
- opening through which blood vessels, nerves, or ligaments pass
- eg: optic Foramen canal of the sphenoid bone
18
Q
Fossa
A
- shallow depression
- eg: coronoid fossa of humerus
19
Q
Sulcus
A
- furrow along a bone surface that accommodates a blood vessel, nerve, or tendon
- eg: intertubercular sulcus of humerus
20
Q
Meatus
A
- tubelike opening
- eg: external and internal auditory meati of temporal bone
21
Q
Condyle
A
- large, round protuberance with a smooth articulate surface at the end of a bone
- eg: lateral Condyle of the femur
22
Q
Facet
A
- smooth, flat, slightly concave or conveys articulate surface
- eg: superior articulate facet of a vertebrae
23
Q
Crest
A
- prominent ridge or elongated projection
- eg: iliac crest of the hip bone
24
Q
Epicondyle
A
- typically roughened projection above a Condyle
- eg: medial Epicondyle of femur
25
Line
- Long narrow ridge or border (less prominent than a crest)
| - eg: linea aspera of the femur
26
Spinous Process
- sharp slender projection
| - spinous process of vertebra
27
Trochanter
- very large projection
| - eg: greater trochanter of femur
28
Tubercle
- variable sized rounded projection
| - eg: greater tubercle of humerus
29
Tuberosity
- variable sized projection that has a rough, bumpy surface
| - eg: ischial Tuberosity of hip bone
30
Histology of Bone Tissue
- connective tissue that contains abundant ECM that surrounds widely separated cells
- most abundant mineral salt is calcium phosphate, which combines with calcium hydroxide to form hydroxyapatite
- these crystals combine with other mineral salts and are deposited in framework formed by collagen fibres, then crystallize and the tissue hardens... this is called CALCIFICATION
- calcification is initiated by bone-building cells called osteoblasts
31
Osteoprogenitor Cells
- unspecialized bone stem cells derived from mesenchyme, the tissue from which connective tissues derive
- only bone cells that undergo cell division, resulting in osteoblasts
- osteoprogenitor cells are found along inner portion of the periosteum, in the endosteum, and in the canals within bone that contain blood vessels
32
Osteoblasts
- Bone building Cells
- synthesize and secrete collagen fibres and other organic components needed to build the ECM of bone tissue and initiate calcification
- become trapped in their secretions and then become osteocytes
- any cell with suffix blast secretes ecm
33
Osteocytes
- mature bone cells
- main cells in bone tissue and maintain is daily metabolism: exchange of nutrients and wastes within blood
- osteocytes don't undergo cell division
- any cells with suffix cyte maintain and monitor tissue
34
Osteoclasts
- huge cells derived from the fusion of as many as 50 monocytes, and are concentrated in the endosteum
- plasma membrane of an osteoclast is deeply folded into a ruffled border on the side of the c ell that faces the bone surface
- cell releases powerful lysosomal enzymes and acids that digest the protein and mineral components of the underlying ecm of bone
- this is called bone resorption, and is part of the normal development, growth, maintenance and repair of bone
35
Compact Bone Tissue
- aka cortical or dense bone
- repeating structural units called osteons or haversian systems
- each steam consists of a concentric lamellae arranged around a osteonic canal/haversion canal
- concentric lamallae are circular plates of mineralized ecm of increasing diameter surrounding small network of blood vessels and nerves
- lacunae: small spaces that contain osteocytes
- canaliculi: small channels that radiate from lacunae and are filled with ecm
- inside canaliculi are finger projections of osteocytes
- neighbouring osteocytes communicate via gap junctions
36
Osteons in compact bone tissue
- aligned in the same direction and are parallel to the length of the diaphysis
- results in the long bone resisting bending or fracturing even under immense pressure
- lines of stress in a bone are not static
37
Interstitial Lamellae
- areas between neighbouring osteons that contain lamellae
- also have lacunae with osteocytes and canaliculi
- interstitial lamellae are fragments of older osteons that have been partially destroyed during bone rebuilding or growth
38
Interosteonic Canals
- bloods vessels and nerves from the periosteum penetrate the compact bone through these transverse canals
- these vessels and nerves connect with those of the medullary cavity, periosteum and central canals
39
Circumferential Lamellae
- Lamellae that are arranged around the entire outer and inner circumference of the shaft of a long bone
- develop during initial bone formation
- circumferential lamellae deep to periosteum are called external circumferential lamellae - they are connected to the periosteum bu perforating fibres
- circumferential lamellae that line medullary cavity are called internal circumferential lamellae
40
Sponges Bone Tissue
- trabecular or cancellous bone tissue
- doesn't contain osteons
- always located in the interior of a bone, protected by compact bone
- consists of lamellae arranges in an irregular pattern of thin columns called trabeculae
- between trabeculae are filled with red bone marrow in bones that produce blood cells, and yellow bone marrow in other bones
- both types of bone marrow contain numerous small blood vessels that provide nourishment to the osteocytes
- each trabecula consists of concentric lamellae, osteocytes that lie in lacunae, and canaliculi
41
DIfference between spongey and compact
- spongey is light, reducing overall weight of the bone, which allows bone to move more readily when pulled by a muscle
- trabeculae of spongy bone tissue support and protect the red bone marrow
42
Blood and Nerve Supply of Bones
- bone is richly supplied with blood
| - vessels especially abundant in red bone marrow, which pass into bone through periosteum
43
Periosteum Arteries
- small arteries accompanied by nerves, enter the diaphysis through interosteonic canals and supply the periosteum and outer compact bone
- nutrient artery enters compact bone through centre of diaphysis on an oblique angle through the nutrient foramen
- path of the artery through the bone is always from the dominant growth end (to the elbow, flee the knee)
- when entering medullary cavity, nutrient artery divides into proximal and distal branches that course toward each end of the bone
- the branches supply both the inter part of compact bone and spongey tissue and red bone marrow as far as epiphyseal plate
44
Metaphyseal Arteries
- ends of long bones supplied by epiphyseal and metaphyseal arteries, which arise from that supply of the associated joint
- artery enters metaphyses of a long bone and with the nutrient artery supplies the red bone marrow and bone tissue of metaphyses
45
Epiphyseal Arteries
-enters epiphyses of long bone and supplies the red bone marrow and bone tissue of epiphyses
46
Veins associated with bones
- veins that carry blood away from long bones are evident in 3 places:
1. one or two nutrient veins accompany their respective arteries and exit through diaphysis
2. Numerous epiphyseal veins and metaphyseal veins accompany their respective arteries and exit through epiphyses
3. Many small periosteal veins accompany their respective arteries and exit through periosteum
-the periosteum surrounding the bone has numerous lymphatic capillaries and lymph vessels but no evidence of lymphatic vessels within the bone tissue
47
Ossification
- process by which bone is formed
- aka osteogenesis
- occurs in principle situations:
1. The initial formation of bones within embryo and fetus
2. Growth of bones during infancy/childhood etc
3. Remodelling of bones
4. Repair of fractures
48
Initial Bone Formation
- embryonic skeleton first composed of mesenchyme in general shape of bones
- these become sites of cartilage formation and then ossification
- 2 methods of bone formation that involve replacing connective tissue with bone:
1. Intramembranous ossification
2. Endochondreal ossification
49
Intramembranous Ossification
- bone forms directly within condensed mesenchyme, which is arranged in sheet like layers
- simpler method
- formation of flat bones of skull, facial bones, mandible, medial part of clavicle
50
Process of Intramembranous Ossification
1. Development of ossification centre: at bone development site, chemical messages cause mesenchymal cells to cluster and differentiate into osteoprogenitor cells then to osteoblasts. Site called ossification centre. Osteoblasts secrete organic ECM of bone until surrounded
2. Calcification: secretion of ECM stops and cells, now osteocytes, lie in lacunae and extend narrow cytoplasmic processes into canaliculi. Calcium and salts are deposited and ECM calcifies.
3. Formation of Trabeculae: as bone ECM forms, develops into trabeculae that fuse with one another to form spongey bones around network of blood vessels. Connective tissue associated with blood vessels differentiates into red bone marrow
4. Development of periosteum: mesenchyme at periphery of bone condense and develops into periosteum. Thin layer of compact bone replaces the surface layers of spongey bone. Much of new bone is remodelled into adult size and shape.
51
Endochondral Ossification
1. Development of Cartilage Model
2. Growth of Cartilage model
- interstitial growth
- appositional growth
3. Development of primary ossification centre
4. Development of Medullary cavity
5. Development of secondary ossification centre
6. Formation of articulate cartilage and epiphyseal growth plate
