The Skeletal System Flashcards
How many bones are there in the appendicular skeleton?
126 bones
Osteology
= the study of the bone
What does collagen enable bones to do?
- Enable bone to resist being stretched or torn apart (tensile strength).
- Prevents bones being hard and brittle.
Osteoprogenitor cells
stem cells derived from mesenchyme (connective tissue found in the embryo) that have the ability to become osteoblasts
What does the appendicular skeleton include?
- Upper limbs
- Lower limbs
What does the axial skeleton include?
- Head (cephalic)
- Neck (cervical)
- Chest and trunk (thoracic)
- Lumbar and pelvis
Osteoblasts
secretes collagen and other organic components to form bones (builders)
Osteocytes
mature bone cells that maintain the daily activities of the bone
Osteoclasts
cells found on the surface of bones and they destroy or resorb bone tissue (demolition crew)
What can spongy bone also be known as (2)?
- Cancellous
- Trabecular bone
What is spongy bone responsible for?
the flexibility and weight distribution shifts that can withstand multidirectional forces
Describe the structure of spongy bone.
It is light, porous, and is made up of small, needle-like pieces of bone arranged like a honeycomb.
What is compact bone also known as?
cortical bone
Where is compact bone found?
forms outer layer of most bones (found in shafts of femur, tibia and fibula).
Describe compact bone.
It is dense, hard, and heavy tissue which makes up most of the bone’s weight.
What is the purpose of compact bone?
It provides:
- strength and protection
- insulation
- movement frameworks and ideal for resisting compressive forces.
What are compact bones made up of?
units called osteons or Haversian systems.
What are (7) functions of bones?
- Support
- Shape
- Protection
- Movement
- Mineral storage (calcium, phosphate and fat storage)
- Blood cell production in bone marrow
- Storage of energy (as bone marrow stores lipids, which can be used as an energy reserve)
What is intramembranous ossification?
where bone forms on or within loose, fibrous connective tissue membranes without first going through a cartilage stage
What is endochondral ossification?
where bones form in hyaline cartilage which has been produced by chondroblasts
What are some clinical features of fractures?
- pain
- deformity
- oedema
- muscle spasm
- abnormal movement
- crepitus
- loss of function
- hypovolaemic shock
- limitation of joint movement
- muscle atrophy
What are the 4 steps to fracture healing?
- Haematoma formation and inflammation
- Fibrocartilaginous callus formation (woven bone/spongy bone formation)
- Bony callus formation/Consolidation (lamella bone formation - solid union of fracture)
- Bone remodelling
How do we know when a fracture is healed?
- Absence of pain on weight-bearing, lifting or movement
- No tenderness on palpation at the fracture site
- Blurring or disappearance of the # line on x-ray
- Full or near full functional ability
How long does cancellous (spongy) bone take to heal?
approx. 3-12 weeks
How long does is take compact bone to heal?
approx. 12-18 weeks
What is bone growth in length called?
interstitial growth
What is bone growth in diameter called?
appositional growth
What is bone growth primarily controlled by?
hormones
Describe the steps involved in intramembranous ossification
- Clusters of osteoblasts form a centre of ossification that secretes the organic extracellular matrix.
- The extracellular matrix hardens by deposition of the calcium and mineral salts.
- Bony matrices fuse to form trabeculae.
- Periosteum develops on the bone’s periphery.
- Spongy bone is replaced with compact bone on the bone’s surface.
What is a zone of hypertrophic cartilage?
a column-like layer of maturing chondrocytes.
What is a zone of calcified cartilage?
a region of dead chondrocytes.
What is a zone of proliferating cartilage?
a layer of actively dividing chondrocytes.
What is a zone of resting cartilage?
a layer of small, scattered chondrocytes anchoring the epiphyseal (growth) late to the bone.
What happens to bones when mechanical stresses are absent?
bones weaken
What happens to bones when mechanical stresses are excessive?
bones thicken abnormally
Diaphysis
= each long bone’s main, central shaft
Periosteum
= membrane covering the diaphysis (in 2 layers)
What are the 2 layers of periosteum?
- Outer fibrous layer: made of dense, irregular connective tissue that contains blood vessels, lymph vessels and nerves that pass into the bone.
- Inner osteogenic layer: made of elastic fibers and containing blood vessels and bone cells.
Where is articular cartilage found?
each epiphysis (is covered by a thin layer of hyaline cartilage - articular cartilage)
Epiphysis
= each end of the diaphysis (where red blood cells are made)
What is the purpose of articular cartilage?
reduces friction and absorbs shock
Metaphysis
= the region where the diaphysis joins the epiphysis
Epiphyseal plate
= (in a growing bone) the metaphysis has a layer of hyaline cartilage that allows the diaphysis to grow in length
Epiphyseal line
= replaces the epiphyseal plate in a mature bone that’s no longer growing in length
Endosteum
= membrane lining the medullary cavity (which is inside the diaphysis)
How many axial bones are there?
80
What does it mean for healing time if a fractured bone has poor blood supply
healing takes longer
What (during childhood) promotes growth at epiphyseal plate, and has production stimulated by human growth hormone?
insulin like growth factors
What is involved in bone growth by increasing osteoblast activity, and also causes long bones to stop growing in length?
sex hormones
What decreases blood calcium levels by accelerating calcium depositions in bones and inhibiting osteoclasts?
CT (calcitonin)
What does mechanical stress do to bone strength?
increases it
How does mechanical strength increase bone strength?
by increasing deposition of mineral salts and production of collagen fibres
How does removal of mechanical stress weaken bone?
through demineralisation and collagen fibre reduction
How does aging result in weakened bones?
- reduced osteoblast activity, which causes demineralisation
- decreased production of extracellular matrix proteins (mostly collagen fibres), which make bones more brittle and so more susceptible to fracture
What (3 things) does osteoclast activity increase?
- loss of bone mass
- compact bone thins
- spongy bone - bigger gaps
What are risk factors of osteoporosis?
- smoking
- low BMI
- diet
- corticosteroids
What are the 4 stages to fracture repair?
- Hematoma formation
- Fibrocartilaginous callus formation
- Bony callus formation
- Bone remodelling
What are the (6) bone shapes/types?
- flat
- sutural
- long
- short
- sesamoid
- irregular
What (4) principal situations does ossification occur?
- initial formation of bones in an embryo and foetus (b/w 6th and 7th week of embryonic life)
- bone growth during infancy, childhood and adolescence until their adult size
- bone remodelling
- fracture repairs
When does intramembranous ossification begin?
when mesenchymal cells differentiate into osteoblasts, which secrete an extracellular matrix that hardens into bone
Where does endochondral ossification mainly occur?
- physis
- epiphysis
- cuboidal bones of the carpus and tarsus
How does fixation affect fracture healing time?
- adequate fixation prevents impairment of the blood supply, which may be caused by movements of the fragments
- maintains the reduction so prevents deformity and loss of function
How does age affect fracture healing time?
- children = quicker and consolidation may occur at b/n 4-6 weeks
- adults = makes little difference depending on other factors
How does smoking affect fracture healing time?
increased rate of delayed union and non-union
How does diet affect fracture healing time?
bone and soft tissue healing requires large amount of calories, proteins and minerals
How does infection affect fracture healing time?
colonisation of bacteria = necrosis and oedema = slow healing = or cellular death
How does ultrasound affect fracture healing time?
low intensity US may accelerate fracture healing
How long does union of the proximal 1/3 humerus take?
7-10 days
How long does union of the distal 1/3 radius take?
4-6 weeks
How long does union of the proximal 1/3 femur take?
4-6 weeks
How long does union of the distal 1/3 tibia take?
6-8 weeks
How long does consolidation of the proximal 1/3 humerus take?
3-4 weeks
How long does consolidation of the distal 1/3 radius take?
8-10 weeks
How long does consolidation of the proximal 1/3 femur take?
8-12 weeks
How long does consolidation of the distal 1/3 tibia take?
16-20 weeks
What are () complications of fracture?
- pulmonary embolism and deep vein thrombosis
- hypovolemic shock or loss of blood
- fat embolism –> acute respiratory distress syndrome
- skin plaster sores
- muscle damage and atrophy
- compartment syndrome
- avascular necrosis
- problems with union
- growth disturbance
- intra-articular fractures
- visceral injuries
- adhesions
- injury to large vessels
- nerve injury
- oedema
What are (5) clinical signs of hypovolemic shock or blood loss?
- tachycardia
- pallor
- hypoxia
- confusion
- state of semi-consciousness
What are (5) clinical signs of compartment syndrome?
The 5 P’s:
- pale
- painful
- pulseless
- paraesthesia
- paralysed
Reduction (when fracture management)
= realign to normal position
(e.g: closed (MUA - manipulation under local anaesthesia) or open (ORIF))
What are the (7) principles of fracture management?
- reduction
- immobilisation
- functional or cast bracing
- internal fixation
- intramedullary nailing
- external fixation
- traction
ORIF
Open Reduction and Internal Fixation
- a surgical procedure to repair broken bones
- useful when: compound (open), comminuted, displaced fractures, and fractures involving a joint
Open reduction
surgeon makes an incision to realign bone
Internal fixation
surgeon uses hardware like screws, plates, rods, or wire to hold bones together
What is a sesamoid bone?
a bone embedded within a tendon or a muscle
How do sesamoid bones impact tendons?
provide a smooth surface for tendons to slide over, increasing the tendon’s ability to transmit muscular forces
