BONE ANATOMY Flashcards
What is the cortex?
Tube of solid bone
What is the medulla?
Central cavity filled with bone marrow
What is the diaphysis?
The shaft/ long part of the bone
What is the epiphysis?
The round part of the bone end
What is the metaphysics?
The flared part of the bone towards the end
What is the different between a cortical and cancellous bone?
Cortical is compact
Cancellous is spongy
How many bones in a dog skeleton and in which part?
Trunk- 136
Limbs- 186
Visceral (in soft organs)- 1
What is the axial skeleton?
Bones forming the axis/ centre of the body (vertebrae, pelvis, tail etc.)
What is the appendicular skeleton?
Bones that are attached (forelimbs/ hindlimb)
What are the two examples of visceral bones?
Os penis (cats and dogs)
Os cordis (heart of ruminants)
What is ossification and the two different bone types?
Bones turning hard
- chondral ossification
- membranous ossification
What is Chondral ossification and what bones are formed from it
Bones ossify from a cartilage precursor
Bones replace cartilage
Most weight bearing bones/ limbs
What is membraneous ossification and what bones are formed from it?
develops directly from sheets of mesenchymal (undifferentiated) connective tissue.
Most bones of the skull and scapula
What are the different types of bones?
Long bones
Short bones
Flat bones
Sesamoid bones
Irregular bones
Why is it important to have lots of different types of bones?
Different shapes have evolved for different functions
Anatomy is about structure and function
Understanding structure of bone helps understand disease processes
What is the shape, function and examples of long bones?
Cylindrical shape
Main part of bone is a column providing strength,
Expanded ends provide transfer of load
Resist tension during muscle contraction
Humerus, radius, femur, tibia
What is the shape, function and examples of short bones?
Many sides, similar dimensions throughout
They are found in groups to distribute weight and force more evenly and reduce concussive forces)
Carpal and tarsal bones
What is articulate bone?
Bone to bone joint
What is a non articulate
A surface for a ligament or tendon to join to
What is the shape, function and examples of irregular bones?
Irregular shape
Common example is vertebrae
What is the shape, function and examples of flat bones?
Thin flat bones
Act as attachments for soft issues and protect underlying tissues
Bones of skull, scapula, pelvis, ribs
What is the shape, function and examples of pneumatic bones?
Bones that have air spaces
Flat bones of the skull that form the paranasal sinus
What are sesamoid bones?
Provides additional strength and reduces wear over joints
Protects tendon over a bony provinence (navicular bone)
Redirects course of tendon (patella)
Attachment for tendon (patella)
Weight bearing function (fetlock)
What is the periosteum structure and function
the membrane of blood vessels and nerves that wraps around most of your bone
Delivers blood supply and sense of feeling to the bone
What is structure and function of the compact bone?
Solid bone consisting of concentric bone arranged around a central osteone
Provides strength and protection
What is structure and function of the cancellous bone?
Less dense and contains red bone marrow
Bone is lighter and produces red blood cells
What is structure and function of the medullary cavity?
Hollow part that contains bone marrow
Makes red blood cells and stores fat
What is deltoid tuberosity and where is it on the humerous?
Triangular part providing attachment for deltoid muscle
About 1/3 towards elbow
What are the medial and lateral epicondyles?
Point of attachment for ligaments or tendons
Allows forearm to flex and extend
What is the trochanter?
The tubercle (small rounded part) of the femur near the hip
Where are the medical and lateral fermoral condyle?
The medial femoral condyle is located on the inside part of the knee whereas the lateral femoral condyle, which is bigger, is located on the outside part of the knee.
What is the intercondylar fossa and its function?
The region between the two femoral condyles and it stabilises the joint
What is the extensor fossa?
Pit/ groove at top of femur
What are the 4 needs for a skeleton?
Structural —> supports the body
Protection —> protects vital organs
Locomotion —> provides rigid rods for muscle attachment
Mineral reserve
What are some limitations of the bone?
Rigid
Hard/ brittle
Unable to expand from within
What are the three main components of bone tissue?
Matrix
Cells —> osteocytes, osteoblasts, osteoclasts
Vesicular spaces (carrying blood vessels)
What is the osteoid
Ground substance (matrix) of bone which contains collagen
What synthesises the osteoid
Osteoblasts
What type of collagen is in the bone matrix and what features does it have?
90% type 1
Strong and inert
What is in the ground substance of bones and what are their functions?
Glycoproteins —> binds collagen and minerals
Proteoglycans —> bind growth factors
Bone sialoproteins —> associated with cell adhesion
How much of the dry bone weight is due to minerals
60-70%
What is the function of bone minerals
Makes it hard
When does mineralisation of the bone take place?
As soon as the osteoid is secreted
Reaches about 70-80% complete 3 weeks before birth
Then takes about 18 years to fully mineralise
What is the advantage of the bones not being fully mineralised?
Mother is less likely to be damaged during birth, as foetus has bendy bones to leave the birth canal
Infant less likely to break bones during falls
When do you typically see woven bone?
Young growing bones
Fracture repair
Quick at forming and mineralising
Will eventually form lamellar bone
What is the structure of lamellar bone like and why it it advantageous?
Thin layers of osteoid in which collagen fibres are parallel
Structurally superior and stronger
What is an osteon?
a cylindrical structure in which a central canal containing blood vessels is surrounded by 20 to 30 concentric lamellae
What is fibrolamellar bone?
Similar to lamellar bone but with a few more fibres
When are primary osteons formed?
During appositional bone growth (when bone grows outwards)
What is cortical bone surrounded by?
Woven bone
What is a Haversian system?
Osteocytes lying in concentric circles and surrounded by a calcified matrix
What is the function of osteoblasts?
Secretes osteoid (matrix of bone)
Active in mineralisation
Where are osteoblasts derived from?
Mesenchymal stem cells
What is the structure and function of osteocytes?
Scattered within the matrix
Interconnected by dendritic processes for communication
Are in lacunae, which are connected by canniculi
They maintain matrix
What is the structure and function of osteoclasts?
Responsible for bone reabsorption (bone might need to change shape/ get rid of dead bone)
Multiple nuclei
How do osteoclasts break down bone?
Release protons to make acidic environment for demineralised environment
Secrete proteases to destroy matrix
How are bones remodelled? (Turning into osteon)
Osteoclasts excavate a tunnel through bone
Osteoblasts follow and form a secondary osteon
What is the purpose of bone remodelling?
Changes bone shape
Changes bone material
Repairs damaged bone
Releases mineral ions
What is a stress fracture?
A localised bone injury due to stress or fatigue damage due to repetitive loading
What is maladaptive remodelling?
Cells burrow to repair small broken fractures
Creates pores and holes in bone so it’s weaker
What is maladaptation of bone?
Cells burrow to try and fix small fractures in bone, which creates pore and holes in bone so it’s weaker
What is the yield point of a bone?
Point at which a structure will no longer return to its original shape
What is the plastic region on a bone graph
The structure is deformed and moving towards failure
What is stress on bone graph
Force per unit area
What is strain on a bone graph?
Percentage of elongation
How does remodelling contribute to failure of the bone?
High strain
Micro damage (stress fractures)
Remodelling
Increased porosity of the bone
What the structure of compact bone
Compact bone consists of closely packed osteons or haversian systems. The osteon consists of a central canal called the osteonic (haversian) canal, which is surrounded by concentric rings (lamellae) of matrix.
What is the structure of spongy bone?
Spongy bone has a honeycomb-like structure with interconnecting spaces filled with bone marrow. It does not contain Haversian and Volkmann canals like compact bone. It is composed of thin, branching bony plates known as trabeculae.
What is the function of spongy bone?
Spongy bone primarily functions in shock absorption, reducing the weight of bones, and facilitating metabolic exchange between bone cells and the surrounding tissue. It contains red marrow, which contains stem cells for the formation of blood cells
What is the function of cortical bone?
Compact bone provides strength, support, and protection to the body. It resists compression forces, bears the majority of the body’s weight, and houses yellow bone marrow, which stores adipose tissue or fat.
What are the Volkmann canals?
They interconnect the Haversian canals for communication
What is an osteon?
The osteon consists of a central canal called the osteonic (haversian) canal, which is surrounded by concentric rings (lamellae) of matrix. Between the rings of matrix, the bone cells (osteocytes) are located in spaces called lacunae.
Where are the osteocytes
In the lacunae (spaces in bone tissue)
What is the endosteum?
Membrane in the inner surface of the bony wall
What do the canniculi look like on a micrograph?
Black line running from central canal
What do the canniculi do?
Provide nutrients from the central canal to the osteocytes in the lacuna
What is the lamellae on the micrograph and what actually is it>
Each little ring
It’s layers of compact matrix in concentric rings
How is calcium conc. increased if too low in blood?
Vitamin D is converted into calcitrol if PTH present
Calictrol stimulates:
- osteoclasts activity
- decrease in calcium excretion at kidney
- increase in calcium absorption at intestine
How is calcium conc. decreased if too high?
Calcitonin inhibits osteoclast activity
Calcium absorption at intestine is inhibited
Calcium excretion at kidney is increased
Which bone cell is multinuclested
Osteoclasts
What is the periosteal lamallae?
Single layer (or lamellar) periosteal reaction is a uniformly dense, single thin layer of new bone about 1-2 mm from the cortical surface
What is enchondral ossification
Length growth in long bones (limbs, vertebrae, ribs and base of skull)
•Cartilage is invaded by vessels and undergoes mineralization
•Occurs in the growth plates (physes)
What is intermembraneous ossification and which bones use jt?
Direct formation of bone
Flat bones
Width growth of bones
What are the 5 different zones on the growth plate?
Resting zone
Proliferation zone
Hypertrophic zone
Calcification zone
Ossification zone
What is a fossa
Shallow depression in bone where another bone may join it
What are the two fossa’s on the scapula?
Cranial end—> supraspinous fossa
Caudal —> infraspinous fossa
Where is the acromion?
End of spine of scapula
What is the glenoid cavity?
small depression present at the lateral part of the scapula bone or shoulder blade of the pectoral girdle.
It is present below the acromion process.
Glenoid cavity articulates with the humerus of the upper limb by the glenohumeral joint.
