Normal function and development Flashcards
(36 cards)
What purpose do bones have?
- Raises us up form the ground against gravity
- Determines basic body shape
- Transmits body weight
- Forms jointed lever system for movement
- Protects vital structures from damage
- Houses bone marrow
- Mineral storage (calcium, phosphorous, magnesium)
Which bones are in the axial skeleton
Skull - cranium, maxilla, mandible Middle ear - (ossicles malleus, incus, and stapes/hammer, anvil, and stirrup) Hyoid bone Rib cage Sternum Vertebral column
The axial skeleton is the part of the skeleton that consists of the bones of the head and trunk of a vertebrate.
Which bones are in the appendicular skeleton
The appendicular skeleton is divided into six major regions: Pectoral girdles (4 bones) Left and right clavicle (2) scapula (2) Arms and forearms (6 bones) Left and right humerus (2) (arm), ulna (2) and radius (2) (forearm).
How can bones be classified by shape? (5)
- Long bones - tubular shape with hollow shaft and ends expanded for articulation with other bones eg, femur, tibia
- Short bones - cuboidal in shape, eg carpals and tarsals
- Flat bones - plates of bones, often curved, protective in function, eg cranium, sternum, ribcage
- Irregular bones - various shapes, eg hyoid bone
- Sesamoid bones - round, oval nodules in a tendon or muscle, eg kneecap/patella, pisiform in the wrist found in joints (sesame)
Types of bone structure -macro (2)
- Cortical - compact, dense, solid bones only has spaces for cells and blood vessels
- Trabecular - cancellous, spongy, network of bony struts (trabeculae), looks like a sponge, many holes filled with bone marrow, the cells reside in trabeculae and blood vessels in holes
Types of bone structure -micro (2)
- Woven bone/Primary bone - quick formation, disorganised, no clear structure
- may devleop directly from mesenchyme (membrane), or cartilage proformer (endochondral) - Lamellar bone/Secondary bone - made slowly, organised, layered structure, as a result of remodelling, good strength to weight ratio
How does bone structure contribute to function
a) Hollow long bone
b) Trabecular bone
c) Wide ends
a) Hollow long bone - keeps mass away from neutral axis, minimizes deformation
b) Trabecular bone - gives structural support while minimizing mass
c) Wide ends - spreads load over weak, low friction surface
What is the composition of bone?
50-70% Mineral (hydroxyapatite, crystalline form of calcium phosphate)
20-40% Organic matrix (collagen (I) 90%, 10% is non-collagenous proteins)
5-10% Water
Collagen is assembled in fibrils with mineral crystals situated in ‘gap’ regions between them
Why does bone contain collagen and mineral? (and water)
Mineral provides stiffness
Collagen provides elasticity
What two ways can bone form?
- Intramembranous bone - originates within sheets of connective tissue (collagen type II)
(Mesenchyme is embryonic connective tissue that is derived from the mesoderm and that differentiates into hematopoietic and connective tissue)
- Endochrondral bones - begin as models of hyaline cartilage that are replaced by bone (collagen type I)
What is the difference between modelling and remodelling?
Modelling - gross shape is altered, bone is added or taken away
Remodeling - all of the bone is altered and the new bone replaces the old bone
What are the 4 main cells of the bone?
Osteoclast - multinucleated
Osteoblast - plump, cuboidal
Osteocyst - stellate, entombed in bone
Bone-lining cells - flattened, line the bone
How does bone remodelling occur? (5/6)
- Resting phase
- Activation
- Resorption
- Reversal phase
- Formation
- (Resting stage)
What do bone cells differentiate from? (and into)
Mesenchymal stem cell = progenitor = can differentiate into, adipocytes, osteoblasts, chondrocytes, myoblasts, fibroblasts
Hematopoietic stem cells = osteoclasts (modulated by RANK L and others)
Function of osteoblast
- The Build Bone (in form of osteoid)
- Produce TYPE I collagen and mineralize the extra cellular matrix by depositing hydroxyapatite crystal (crystalline form of calcium phosphate) within collagen fibrils
- High alkaline phosphatase activity
- Make non-collagenous proteins
- Secrete factors that regulate osteoclast (RANKL)
Mesenchymal stem cell
Function of osteoclast
- Resorb bone
- dissolve mineralised matrix (Acid)
- Breakdown collagen in bone (Enzymatic)
- High expression of TRAP and Cathepsin K
Hematopoietic stem cells
Function of osteocyst
- Live inside the cell and have long branches which allow them to contact each other and line the surface of cells
- Sense mechanical strain on the bone
- Can secrete growth factors which activate the lining cells or stimulate osteoblasts
Why are bones remodelled? (6)
- Form bone shape
- Replace woven bone with lamellar bone
- Reorientate fibrils and trabeculae in favourable direction for mechanical strength
- Response to loading (exercise)
- Obtain calcium
- Disease
How do the cells of the bone function when trauma has occurred?
Osteoblasts - produce new woven bone (quick formation)
Osteoclasts - mop up dead bone and remodel into strong bone
Osteoblasts - then lay down the lamella bone (slower to form, well structured)
What occurs in osteoporosis?
When breakdown exceeds synthesis
-often linked to reduce oestrogen in women after the menopause
What are bone lining cells?
- Former osteoblasts which have become flat
- Line entire surface of the bone, responsible for release of calcium
- Protective
- Receptors from hormones that initiate bone remodelling
What are the types of collagen?
I a) loose and dense ordinary connective tissue, collagen fibres (fibroblasta and smooth muscle cells)
b) fibrocartilage
c) bone - osteoblasts
d) dentin - odontoblasts
II a) hyaline and elastic tissue - chondrocytes
b) vitreous body of the eye - retinal cells
III a) loose connective tissue, reticular fibres - fibroblasts and reticular cells
b) papillary layer of dermis
c) blood vessels - smooth muscle cells, endothelial cells
IV basement membrane - epithelial and endothelial cells
List of some types of collagen
Type I Skin, bone, teeth, capsules of organs
Type II Cartilage
Type III Liver, kidney, spleen, arteries, uterus
Type IV Basement membranes
Type V Placenta
Fibrillar collagen structure
- 3 collagen molecules form 3-stranded tropocollagen molecule
- triple helices
