principles of the skeletal system Flashcards
What is the function of the skeletal system?
- protection of organs
- supports the body
- movement
- metabolic reservoir
- production of new red blood cells
What are the two divisons of the skeletal system?
axial and appendicular
What is part of the axial division of the skeletal system?
- cranium
- thoracic cage
- spine
- sacrum
What is part of the appendicular division of the skeletal system?
- shoulders
- hips
- limbs
What are the 3 layers of the embryonic disc?
- ectoderm
- mesoderm
- endoderm
What are the two types of tissues in the skeletal system?
cartilage and bone
Describe the cartilage
- forms skeleton in parts where flexibility is required
- avascular
- connective tissue
What are the two types of bone?
compact and spongy
Describe bone
- hard form of connective tissue
- provides rigid framework
- vascular
What is ossification?
the process by which bone is formed
What is the process by which bone is formed called?
ossification
What are the two methods through which ossification can occur?
- intramembranous
- endochondral
What is mesenchyme?
embryonic connective tissue
Describe the steps of intramembranous ossification?
- mineralisation of mesenchyme
- cells divide and condense around capillary network (grows radially, fusing together and replacing connective tissue)
What is the starting point in intramembranous ossification called?
primary ossification centre
What does undifferentiated mesenchyme become in intramembranous ossification?
bone marrow
Give examples of bones arising from intramembranous ossification
- skull
- mandible
- clavicle
What is endochondral ossification?
where a cartilaginous template made from the mesenchyme is replaced by bone
What 2 cells is the bone made up of?
- osteoprogenitor cells
- osteoclasts
What 2 cells types can osteoprogenitor cells become?
osteoblasts and osteocytes
What are osteoclasts derived from?
blood monocytes/macrophages
Which 2 bone cell types are responsible for the constant remodelling of bones?
osteoclasts and osteoblasts
Which things we eat regulate bone maintenance?
- calcium
- phosphorous
- vitamin A, C, D
What role does vitamin A have in bone maintenance?
bone remodelling
What is vitamin C essential for in bone maintenance?
connective tissue
What is vitamin D essential for in bone maintenance?
calcium absorption
Which hormones control bone development?
- parathyroid hormone
- growth hormone (GH)
What is spongy bone also known as?
- cancellous bone
- trabecular bone
Describe spongy bone?
- irregular bony plates called trabeculae
- surrounded by red marrow
- highly vascuralised
How can bone be classified?
- long bones
- flat bones
- irregular bones
- short bones
- sesamoid bones
How many bones are we born with?
270
How many bones do we have by adulthood?
206
What are the 3 classes of joints?
- synovial
- fibrous
- cartilaginous
Describe synovial joints?
- have a joint capsule and synovial cavity
- permit movement
What are the types of synovial joints?
- plane
- saddle
- ball and socket
- hinge
- pivot
- condyloid
Describe fibrous joints?
- connected by collagen
- do not permit movement
Give an example of fibrous joints?
sutures of skull
Describe cartilaginous joints?
- connected by cartilage
- allow some movement
What is the mesoderm layer?
middle layer of embryonic disc from which all connective tissue develops
What is a foramen?
a hole within a bone through which neurovascular structures may pass
When does bone development start and finish?
- starts at 8 weeks
- ends at around 20 years
What is the name of the connective tissue that covers skeletal system (except at articulation)?
periosteum
What is the connective tissue surrounding cartilage called?
perichondrium
How is compact (cortical) bone arranged?
usually in lamellae (called concentric layers)
How do the lamellae in compact bone get arranged?
they are laid down by osteoblasts
How do the osteoblasts often become osteocytes?
- osteoblasts get trapped in osteoid matrix
- turn into osteocytes occupying their own lacunae
How do osteocytes communicate between each other if they are trapped in their lacunae?
- canaliculi radiate from each lacunae
- this is how nutrients travel to them
What contains the neurovascular supply in compact bones?
the Haversian canal
In what group of people are bone fractures the most common?
- over 50s
- cis-women
What are the most commonly fractured bones?
- distal radius
- ankle
- metacarpals
- proximal femur
- proximal humerus
Why can bones heal so well?
because they are a vascularised tissue
