WEEK ELEVEN - BONE TISSUE, SKELETAL SYSTEM AND JOINTS, MUSCLES Flashcards
List & describe 5 functions of the skeleton [spmbe]
1.support
framework for body shape
2.protection
hard tissue protects organs it surrounds eg vertebral column for spine
3.movement
muscle attach to bones = bones move body
4.blood cell production
RBW WBC platelets made in bone marrow
5.electrolyte balance
skeleton stores calcium and phosphate ions - released when needed
Describe the 4 different bone shapes with examples for each
long - levers for muscles to pull on eg femur
short - limited motion - glide across each other
flat - provide for thin/roughly parallel surfaces eg parietal and frontal bones, scapula, sternum
irregular - complex bones with short/flat/rigid surfaces eg facial bones
Describe the general structure for long and flat bones
long [shaft =diaphysis, and enlarged bone ends]
shaft - compact bone surrounds central hollow medullary cavity
- enlarged ends = thin outer layer of compact bone surrounding spongy bone
periosteum - thick CT membrane lines OUTER bone surface
endosteum - thin CT lines INNER bone surface + canals inside bone
flat - external+internal surface = compact bone
middle layer = spongy [diploe]
- has bone marrow between trabeculae
List & describe the cell types and the matrix of bone tissue [1p-4c]
- osteoprogenitor
stem cells found in membranous endosteum and periosteum [differentiate into osteoblasts] - osteoblasts
bone building cells - secrete bone matrix - osteocytes
= osteoblasts that have become surrounded the bone matrix they secreted
- communicate with other osteocytes via canaliculi [tentacle projections] to monitor/maintain bone matrix - osteoclasts
large, multi nucleated cell that dissolves and resorbed bones by secreting acids and proteolytic enzymes
= they released stored minerals in bones
bone matrix [1/3 organic + 2/3 inorganic]
organic = collagen + proteoglycans
inorganic = 85% hydroxyapatite [calcium phosphate crystal] + 10% calcium carbonate/other minerals
= combination of inorganic/organic –> provides strength and resilience
[minerals = strength] lack = floppy and too flexible –> osteomalacia
[collagen= flexibility] lack = bones too brittle –> osteogenesis imperfecta
Describe the histology of compact and spongy bone
compact - closely packed osteons
osteon = central canal [osteonic canal] surrounded by concentric rings [lamellae of matrix]
between matrix = osteocytes found in lacunae spaces
spongy - formed by bone plates [trabeculae]
trabeculae spaces filled with reticular CT = red bone marrow] = site of blood cell production
- lack osteons + central canal but osteocytes are supplied by blood
List & describe the two methods of bone formation
intramembranous ossification [in skull and clavicle bones]
- mesenchymal stem cells aggregate and replicate –> begin differentiating into osteoblasts
- osteoblasts release uncalcified osteoid tissue which is then ossified by calcium phosphate
- further differentiates into osteocytes
- osteocytes compact together = osteon = forms compact bone surrounding spongy bone + periosteum on top
endochondral [forms rest of skeleton]
- perforation of hyaline cartilage delivers osteogenic cells –> differentiate into osteoblasts - secrete osteoid
- secreted osteoid encases diaphysis [shaft] in bone collar
- vascular invasion of boney collar = osteoblasts+osteoclasts shape marrow cavity
- killing and replacement of chondrocyte cartilage cells with bone cells [osteocytes+calcified osteoids]
- In the adult, cartilage remains only as articular cartilage at the joint surfaces
Explain how mature bone continues to grow and also explain Wolff’s law
interstitial growth - increase in length
- by chondrocytes at epiphyseal plates
- growth continues until 1st ossification centre joints with 2nd = epiphyseal line
appositional growth - increase in width throughout life
1. cartilage osteoblasts beneath periosteum lay down bone = form ridges
2. blood vessel lies in groove between ridges = groove becomes tunnel when ridges meet
3. periosteum of groove becomes endosteum of tunnel
4. osteoblasts lay down bone = forms concentric lamellae
5. more concentric lamellae = new osteons
wolff’s law of bone = architecture of bone determined by mechanical stresses place on it = bones will adapt
Discuss how the body maintains calcium homeostasis
calcitriol + parathyroid hormone [PTH] = INCREASES blood calcium levels
- PTH increases osteoclast activity, decreasing osteoblast activity ++ promotes kidney calcium resorption
- calcitriol increases calcium absorption from gut, bone and kidneys
calcitonin = DECREASES blood calcium levels
- reduced osteoclast activity and increase osteoblast activity
List and identify the bones of the axial and appendicular skeletons
axial [central axis]
- skull bones
- vertebral column/sacrum
- ribs/sternum
appendicular [limb bones + pelvic/pectoral girdles
Explain how the structural features of the skull reflect its function
- skull = very thick post. and ant. = protection of brain
- rigid/non-moveable sutures between bones = protection
- one movable bone [mabdible] and joint [temporo-mandibular joint] = mastication and speech
- sinuses = lightens skull + adds resonance to voice
- outer+inner layer of compact bone sandwich sponngy bone = fracture may leave inner layer of compact bone undamaged
Explain how the structural features of the vertebral column (VC) reflect its function
- 33 individual bony vertebrae = movement + protection at same time
- Intervertebral discs = shock absorption and increased ROM
- cervical, thoracic, lumbar, and sacral curvatures = BW distribution over base of support = walking efficiency + shock absorption
- vertebral neural arch enclosing spinal cord - spinal cord protection
Explain how the structural features of the thoracic cage reflects its function
12 pairs of ribs and sternum = Protection of lungs/heart
- attachment points for breathing muscles [intercostals], limb muscles [pectoralis major and minor] and torso muscles [abdominals]
Sternoclavicular joint = Attachment pectoral girdle [clavicle+scapula]
attachment of costal cartilages to sternum = allows rhythmical expansion of rib cage = draws air into lungs
Discuss the similarities & differences between the pelvic & pectoral girdle
similarities
- provide articulation with limbs via ball/socked joint
- large area for muscle attachment sites
- fibrocartilaginous rim [glenoid fossa - humerus// acetabulum-femus] = deepens sockets
differences
- pectoral girdle = 2 bones [clavicle+scapula]
- pelvic girdle = 3 bones [ilium + ischium + pubis]
- pelvic girdle (hip joint) = deeper sockets compared to pectoral girdle (shoulder joint) = shallow socket = implications for shoulder dislocation
- pelvic girdle - attached to vertebral column = movement of spine [does not happen with pectoral girdle
Discuss similarities and differences between the upper and lower limb bones
similarities
- single bone in upper segment eg humerus and femur
- two bones in lower segment eg arm= radius/ulna, leg= tibia/fibula
- both hand+feet = similar number of bones = 5 metatarsal/metacarpals
- hinge at knee and elbow
differences
- patella at knee joint [reduces friction of quadriceps tendon] , but not at elbow
- greater ROM in forearm bones [radius/ulna] over tibia/fiba for hand range of motion
- larger limbs bones in leg for weight bearing purposes
List & describe the structure of the 3 types of fibrous joint types with examples for each
- sutures
immovable fibrous joints that bind skull bones together, short collagen fibres - gomphoses
attachment of a tooth to its socket.
- help in place by fibrous periodontal ligament
- some movement while chewing
- intermediate length collagen fibres - syndesmoses
- MOST MOVEABLE fibrous joints
- two bones bound by ligament only interosseous membrane
- eg tibia-fibula and radius-ulna
