Skeletal System Flashcards
What are the two components of the skeleton?
Axial
Appendicular
What is the axial skeleton?
This consists of bones situated in the long axis of the body in the anatomical
What three groups of bones make up the axial skeleton?
Skull
Cervical vertebrae
Trunk bones, such as the ribs, sternum, vertebrae and sacrum
What is the appendicular skeleton?
This consists of bones which are appended to the axial skeleton, in other bones of the limbs
List three examples of bones which make up the appendicular skeleton
Clavicle
Hip bone
Tibia
What are the limb girdles? What is their role?
They are structures which surround and support the proximal end of the limbs
They provide a point of attachment for the appendicular bones to the axial bones
What is cartilage?
A semirigid, avascular type of connective tissue
What are the four functions of cartilage?
It forms part of the skeleton where flexibility is needed
It covers the end of articulating bones at the joints, providing a smooth, low-friction gliding surface for free movement
It is a precursor of bone
It holds tubes open in the body
What are the three types of cartilage? How do we classify cartilage?
Elastic
Hyaline
Fibrocartilage
By the relative amount of collagen, elastic fibres and matrix
What is the structure of elastic cartilage?
The chondrocytes are found in a threadlike network of elastic fibres within the matrix
What are the three functions of elastic cartilage?
Provides strength
Provides elasticity
Maintains the shape of certain structures
Where are the three places in which elastic cartilage can be found?
External ear
Epiglottis
Larynx
What is the strength of hyaline cartilage compared to the other two types?
Weakest
What is the structure of hyaline cartilage?
It has widely dispersed fine collagen fibres
Where are the four places in which hyaline cartilage can be found?
Ribs
Nose
Larynx
Trachea
What is the strength of fibrocartilage compared to the other two types?
Strongest
What is the structure of fibrocartilage?
It has alternating layers of hyaline cartilage matrix and thick layers of dense collagen fibres, which are oriented in the direction of functional stresses
Where are the three places in which fibrocartilage can be found?
IV discs
Joint capsules
Ligaments
Which two types of cartilage have a perichondrium?
Hyaline
Elastic
What is the function of the perichondrium?
Allows growth and repair of cartilage
Cartilage is avascular, so how does it receive oxygen and nutrients?
Diffusion
Why does cartilage regenerate much slower compared to bone?
Cartilage is avascular but bone has a rich vascular supply
How does the proportion of bone and cartilage change as the body grows?
As you age, the contribution of cartilage decreases
Why are bones of a new-born infant soft and flexible?
They are mainly composed of cartilage
What is bone?
A highly specialised, hard form of connective tissue that makes up most of the skeleton
What are the four main functions of bone?
They provide support and allow weight bearing
They provide protection for vital structures
They are a mineral store, as bones are full of calcium and when calcium is needed by the body it can be extracted
They form a continuous supply of new blood cells
What are the two types of bone?
Compact
Spongy/trabecular bone
How is compact bone organised?
Into circular structure which are referred to as osteons or haversian systems
What exists in the centre of each osteon?
There is a central canal, which contains blood vessels
These blood vessels branch off at right angle through perforating canals, which are known as Volkmann’s canals
Where do Volkmann’s canals extend to?
The periosteum
The endosteum
What are osteons composed of?
Concentric rings of bone matrix, known as lamellae
What is at the border of each lamellae?
Osteocytes which are located inside spaces called lacunae
What is the role of compact bone?
It provides strength for weight bearing
What is the difference between spongy and compact bone?
Spongy bone is less dense than compact bone
How is spongy bone organised?
A network of lamellate trabeculae, which are bone rods
What are the spaces in spongy bone filled with?
Red bone marrow
How does spongy bone withstand high forces?
The trabeculae form along lines of stress to provide strength to the bone
What are the role of the spaces within spongy bone?
To make bone light so that muscles can move them more easily
What is the epiphysis =?
The wider section at each end of the bone
What is the diaphysis?
The tubular shaft that connects the proximal epiphysis and the distal epiphysis together
What is the metaphysis?
The narrow portion of bone between the diaphysis and the epiphysis
What is the proximal epiphysis?
The epiphysis nearest to the middle of the body
What is the distal epiphysis?
The epiphysis furthest to the middle of the body
What type of bone fills the epiphysis?
Spongy
Red marrow fills the spaces in the spongy bone
What type of bone is found in the walls of the epiphysis?
Compact
What is a condyle?
The smooth layer of bone at each epiphysis end
What covers condyles?
Articular cartilage
What is the role of a condyle?
The condyle of one bone will articulate in a joint with the condyle of an adjoining bone
What is found above/below condyles? What is their role?
A protruding area, which forms a rough layer
To allow ligaments, muscles and tendons to attach to the bone
What is an epicondyle?
A rough, protrusion area which is located above the condyle
What is a supracondyle?
A rough, protrusion area which is located below the condyle
What is a medial condyle?
Condyles which are on the side which is nearer to the midline of the body
What is a lateral condyle?
Condyles which are on the side which is further from the midline of the body
What is the medullary cavity?
A hollow region within the diaphysis
What is found within the medullary cavity?
Yellow/red marrow
What are the walls of the diaphysis composed of?
Compact bone
What main structure is found within the metaphysis?
The epiphyseal growth plate
What is the epiphyseal growth plate?
A thin plate of cartilage that allows growth of bone
What happens to the epiphyseal plate as you age?
It ossifies, which means that it converts to bone and you are left with a gap in the bone
What membrane surrounds the outside of bone wall?
Periosteum
What membrane surrounds the inside of bone wall?
Endosteum
What are both the periosteum and endosteum formed from?
Fibrous connective tissue
What does the periosteum cover?
The entire outer surface of bone, apart where the epiphysis articulates with other bones to form joints.
This is because articular cartilage is contained here instead.
What are the three functions of the periosteum?
It contains blood vessels, nerves and lymphatic vessels that nourish compact bone.
It contains osteoblasts. This allows the periosteum to lay down more bone, which is particularly useful during fracture healing.
It provides an interface for attachment of tendons and ligaments.
How do we classify bones?
Shape
What are the five different classifications of bones?
Long
Short
Flat
Irregular
Sesamoid
What are long bones?
Bones with a tubular structure
Why do long bones usually make up limbs?
They allow limbs to support the weight of the body and facilitate movement
List two examples of long bones
Humerus - arm
Phalanges - fingers
What are short bones?
Bones which are cuboidal
Where are the only two places in which short bones are found?
Ankle
Wrist
List two examples of short bones
Tarsus - ankle
Carpus - wrist
What is the role of flat bones?
To protect organs and provide a large area of attachment for muscles
List two examples of flat bones
Sternum
Flat bones are also contained within the cranium
List an example of an irregular bone
Vertebrae
What is the role of sesamoid bones?
They develop in certain tendons to protect them from excess wear. They do this by modifying pressure and diminishing friction
They also change the angle of the tendon as they pass to their tendon and therefore change the direction of muscle pull
List an example of a sesamoid bone
Patella
What are the three causes of bone markings?
Attachment of ligaments, tendons or fascia
Arteries which lie adjacent to or enter bones
Passage of a tendon
What is a crest?
A ridge of bone
What is a facet?
A smooth, flat area of bone that is usually covered with cartilage
What happens at the facet?
A bone articulates with another bone
What is a foramen?
A hole within bone
What is the role of the foramen?
To allow blood vessel and nerves to access the bone and supply it with blood and electrical signals
What is a fossa?
A shallow depression in the bone
What is a line?
A linear elevation of bone
What is a malleolus?
A rounded prominence of the bone
What is a notch?
An indentation at the edge of a bone
What is a process?
A projection or bump
What is a sulcus?
A narrow grove in the bone
What is a spine, in terms of bone markings?
A pointed projection of the bone
What is a trochanter?
A large, blunt elevation of the bone
What is a tubercle?
A rough, small projection of the bone
What is a tuberosity?
A rough, large projection of the bone
What are all bones derived from?
Mesenchyme, which is embryonic connective tissue
What are the two processes which develop bone?
Endochondral ossification
Intramembranous ossification
What is the most common type of ossification?
Endochondral
Describe the process of endochondral ossification
Mesenchymal cells condense and differentiate to form cartilage tissue. This creates a cartilage model.
In the midregion of the cartilage model, the cartilage calcifies, and periosteal capillaries grow into the calcified cartilage.
The capillaries initiate the primary ossification centre in the cartilage, which turns cartilage into bone.
How is the epiphyseal growth plate formed? How?
Endochondral ossification
There is a small layer of cartilage that remains after endochondral ossification.
What type of bones does endochondral ossification form?
Long bones
What three types of bones does intramembranous ossification form?
Flat bones of the skull
Maxilla
Clavicles
Describe the process of intramembranous ossification
The mesenchymal cells develop into osteoprogenitor cells, which are stem cells of bone.
These cells then develop into osteoblasts, which develop bone.
However, not all the mesenchymal cells develop into osteoprogenitor cells, some develop into blood vessels and bone marrow.
What is appositional growth? How does it occur?
Bone growth in width
We add new bone tissue from the periosteum onto existing bone
What is interstitial growth? How does it occur?
Bone growth in length
When cells in the epiphyseal growth plate undergo division
What are the two main components of bone?
Cells
Extracellular matrix
What are the three types of cells found in bone?
Osteoblasts
Osteocytes
Osteoclasts
What cells form osteoblasts?
Osteoprogenitor cells in the periosteum and endosteum
What is the role of osteoblasts?
To form new bone
How do osteoblasts form new bone?
They produce bone matrix and initiate ossification of this bone matrix
What do osteoblasts converts into once they are surrounded by matrix?
Osteocytes
Where are osteocyte found?
In both compact and mature bone
Specifically, they are found inside lacunae, which are cavities of the bone
What do lacunae forms? Why?
They form canals between each other, which are referred to as canaliculi
They allow the osteocytes within the lacunae to communicate with one another
What are the two functions of osteocytes?
To maintain bone matrix
To sense forces
What are osteoclasts formed from?
Haematopoietic stem cells
What is the role of osteoclasts?
Bone degradation
Where are osteoclasts found? Why?
Surface of bone
They can remove the bone tissue underneath them
How do osteoclasts degrade bone?
They release acid, which then then enter the bone matrix and dissolve the minerals contained within it
What do osteoclasts form when they carry out bone degradation?
Howship’s lacunae, which are tiny depressions in the bone that are being resorbed by osteoclasts
What are the three components of extracellular matrix in bone?
Hydroxyapatite crystals
Type one collagen fibres
Water
What are hydroxyapatite crystals?
Minerals, which are specifically complex forms of calcium phosphate
What are the two roles of hydroxyapatite crystals?
To make bone stiff, so that it can support structures within the body
To give bone its high mechanical strength, which allows it to withstand compression forces
How are the collagen fibres organised within bone matrix?
They are striated structures which strongly cross link with one another.
When they cross link, these collagen fibres create large gaps, which provide space for the hydroxyapatite crystals
What is the role of collagen in bone?
To give it some flexibility, which reduces the risk of bone fracturing.
To give bone a high strength under tension, as collagen fibres usually form along lines of stress
What is mechanical adaption?
When bone adapts to mechanical forces, by becoming thicker and increasing in diameter
Describe the process of bone remodelling
Osteoclasts on the surface of bone break down the damaged/old bone
Osteoblasts then build new bone
New bone formed
Name the three arteries which supply bone with blood
Nutrient arteries
Periosteal arteries
Metaphysial and epiphyseal arteries
How do nutrient arteries enter bone?
They arise from outside the periosteum
They pass through the shaft of a long bone via nutrient foramen
They split in the medullary cavity into longitudinal branches
What parts of the bone do nutrient arteries supply?
Bone marrow
Spongy bone
Deeper portions of the compact bone
Where are periosteal arteries found?
Periosteum
What parts of the bone do periosteal arteries supply?
Majority of compact bone
Where do metaphysial and epiphysial arteries arise from?
The arteries that supply joints
What parts of the bone do metaphysial and epiphysial arteries supply?
The ends of the bones
How do veins enter bone?
Through the nutrient formn
Where are lymphatic vessels located within bone?
Periosteum
Where are most sensory, pain nerves found within bone? What are these nerves called?
Periosteum
Periosteal nerves
Where are most vasomotor nerves found? What is their role?
Within bone
To constrict and dilate blood vessels, which therefore regulates blood flow through the bone marrow
What is the main process which usually leads to bone disorders?
Remodelling
What is osteoporosis?
A bone disease that results in bone becoming weaker and more prone to fracture
What is the cause of osteoporosis?
There is more bone resorption occurring than formation.
This means that the trabeculae in the spongy bone tissue become thin or missing.
What is Paget’s disease?
A bone disorder which results in bones not forming properly, making them weaker from a mechanical point
What is the cause of Paget’s disease?
There is an increase in both resorption and formation
What is osteopetrosis?
A bone disorder which results in bone becoming too dense and brittle
What is the cause of osteopetrosis?
There is reduced resorption of bone
What four factors affect bone mass?
Age
Gender
Genes
Lifestyle
What occurs to bone mass during your mid 30’s?
Stops increasing and starts to steadily decline
What occurs to bone mass during menoopause? Why?
There is a striking decline of bone mass
Menopause results in a deficiency of oestrogen, and oestrogen usually inhibits osteoclasts function to resorb bone
Apart from age and menopause, what two factors also decreases bone mass?
Weightlessness
Bed rest
What factor can increase bone mass?
Resistance and high-impact sports
What is a joint?
An articulation between two or more rigid components, such as bone or cartilage
What are the three types of joints?
Fibrous
Cartilaginous
Synovial
What are fibrous joints formed from? What do this mean?
Dense fibrous collagen connective tissue
The articulating bones of fibrous joints are united by fibrous collagen tissue
What is the role of collagen in fibrous joints?
Gives these joints a high tensile strength and means that there is little movement in these joints
What are the three different types of fibrous joints?
Suture
Syndesmosis
Gomphosis
What are suture joints?
They are fibrous joints which are immovable and are only found between the bones of the cranium
What happens to suture joints as you grow?
They fuse, causing the movement in these joints to become even more limited
What are syndesmosis joints?
They are fibrous joints which are slightly moveable
They hold bones together by an intraosseous membrane
What is an intraosseous membrane?
A fibrous sheet of connective tissue that spans the space between two bones
What is a gomphosis joint?
They are fibrous joints which are immovable
They are found between teeth and their sockets.
What are cartilaginous joints?
Joints which are formed from layers of cartilage
What two type of cartilage form cartilaginous joints?
Fibrocartilage
Hyaline
What joints allow more movement - fibrous or cartilaginous?
Cartilaginous
What are the two types of cartilaginous joints?
Synchondroses/Primary
Symphyses/Secondary
What are synchondroses joints?
This joint is formed as a result of endochondral ossification, where at the end of the process we are left with a small plate of hyaline cartilage.
This is known as the epiphyseal growth plat
What is the role of synchondroses joints?
To allow growth
To allow slight movement, until the cartilage ossifies and disappears. This means that it will eventually become immovable
What are synchondroses joints formed from?
Hyaline cartilage
What are symphyses joints?
This joint is usually found between IV discs in the spine
What are symphyses joints formed of?
Fibrocartilage, which means that this cartilage has a lot of collagen fibres. It is also composed of hyaline cartilage
How much movement does symphyses joints allow? Why?
Little movement
This cartilage is very strong
What are synovial joints?
In a synovial joint, the two bones are separated by the characteristic joint cavity, which contains synovial fluid
How much movement do synovial joints allow?
They allow the greatest movement.
They provide free movement between the bones they join
What is the outermost layer of synovial joints?
Accessory structures
List two examples of accessory structures in synovial joints
Ligament
Muscle
What is the role of accessory structures in synovial joints?
Strengthening the joint
What is the fibrous capsule in the synovial joint formed from?
Collagen fibres
What is the synovial membranes role?
To create synovial fluid which fills the synovial cavity
What are the two roles of synovial fluid?
It lubricates the joint
It nourishes the articular cartilage
What are the bones covered with in synovial joints?
Articular cartilage
What type of cartilage forms articular cartilage?
Hyaline
What is in the synovial cavity?
The space between the articulating joints and the synovial membrane
It contains the synovial fluid
What are the six joint movements?
Hinge
Pivot
Saddle
Condylar
Plane
Ball & Socket
Describe hinge joint movements
It joint allows the bones to move along one axis.
This permits flexion and extension only.
Give an example of a hinge joint
Elbow joint
Describe pivot joint movements
It allows rotational movement around a single axis
Describe the structure of a pivot joint
A rounded process of bone fits into a bony ligamentous socket, permitting rotation
Give an example of a hinge joint
Atalanto-axial joint
Describe saddle joint movements
It allows movement in the sagittal and frontal planes, which means that it allows movement forwards and backwards, left and right.
It therefore permits movement in two different planes
Describe the structure of a saddle joint
The shape of this joint links in with its name, as it looks like a saddle
Give an example of a saddle joint
Carpometacarpal joint
Describe condylar joint movements
It allows movement in two planes, therefore they permit flexion and extension, abduction and adduction, as well as circumduction
Give an example of a condylar joint
Metacarpophalangeal joint
Describe plane joint movements
This joint is found between flat surfaces, meaning that only sliding and gliding occurs
Give an example of a plane joint
Acromicrovicular joint
Describe ball and socket joint movements
This joint allows movement in all directions
Describe the structure of a ball and socket joint
A rounded head fits into a concavity, permitting movement in all three planes
What increases the risk of dislocation?
The more degree of freedom that a joint has, as this means that the joint is less stable
Which three structures of joints prevent dislocation?
Shape of articulating surface
Accessory structures
Strong muscles
What shape of articulating surfaces prevents dislocation?
Deep sockets
Where do joints receive blood from?
Articular arteries hat arise from vessels around the joint
What are anastomoses?
Where arteries branches reconnect to form a network
What is the role of anastomoses?
To ensure continuous blood supply to a joint throughout its range of movement
Where are articular veins and arteries located within the joint?
Joint capsule, mostly in the synovial membrane
Which nerves supply joints?
Branches of the cutaneous nerves supplying the overlaying skin
Branches of nerves that supply the muscles that cross the joint
What is Hilton’s Law?
It states that when a muscle’s nerve crosses a certain joint it also supplies the joint with nerves
What sensation do joints transmit?
Proprioception
What is proprioception?
Information that provides an awareness of movement and position of parts of the body
What are three main joint pathologies?
Trauma
Arthritis
Craniosynostosis
Why are fractures of joints common?
Close to the joint there is only a thin layer of compact bone
What is osteoarthritis?
A joint disease that results in the joint cartilage and underlying bone degenerating with age
What is rheumatoid arthritis?
An autoimmune disease that results in your immune system attacking the synovial membrane, which is the lining of the membranes that surround your joints
The resulting inflammation thickens the synovial membrane, which can eventually destroy the cartilage and bone within the joint.
What is craniosynostosis?
This is a birth defect in which the suture joints in a baby’s skull join together too early. This happens before the baby’s brain is fully formed.
As the baby brain grows, the skull can become more misshapen
