Bone and biomechanics Flashcards
Homeostasis
The state of a steady internal, physical and chemical conditions
Epithelial tissue
- Covers exposed surfaces
- Line internal passageways and chambers
- Forms secretory glands
Connective tissue
- Fills internal spaces
- Provides structural support
- Stores energy
Nervous tissue
- Conducts electrical impulses
- Carries information
Muscle tissue
- Contracts to produce movement
- Includes skeletal muscle, cardiac muscle and smooth muscle
Anatomical position
- Upright
- Face forwards
- Feet together
- Palms face forward
- Remains the same regardless of movement
Superior
A position above or higher than another part of the body
Inferior
A position below another part of the body and closer to the feet
Medial
The middle or direction towards the middle of the body
Lateral
The side or direction towards the side of the body
Proximal
Toward or nearest the trunk or point of origin of a body part
Distal
Away from or farthest from the trunk or the point of origin of a body part
Anterior
The front or direction toward the front of the body
Posterior
The back or toward the back of the body
Cranial
Closer to the brain
Caudal
Closer to the tail
Deep
Further from the surface
Superficial
Closer to the surface
Sagittal
Down the middle to create a left and right side
Coronal
Down the middle to create a front and back half
Transverse
Through the middle to create a top and bottom half
Flexion
- Decreases angle
- Fleshy parts of the limb bought closer together
Extension
Increases angle
Dorsiflexion
Toes bought towards the face
Plantarflexion
Toes pointing towards the ground
Abduction
Movements at joint that moves away from the mid-line
Adduction
Movements at joint towards the midline
Circumduction
Combination of four movements - flexion, abduction, adduction, extension
Rotation
Rotation around the long axis of a joint
Pronation
Palms face posterior
Supination
Palms face anterior and forearm bones parallel
Inversion
Sole of foot faces towards the midline
Eversion
Sole of foot turns away from midline
Functions of the skeleton
- Support
- Movement
- Protection of major organs
- Storage of minerals
- Red blood cell formation - in bone marrow
Compact bone
- Strong
- Good at transmitting force in one direction
Cancellous bone
- Light, spongy
- Sock absorbing
- Resists and channels force that come from multiple directions
Long bones
- Longer than they are wide
- Composed of wider epiphyses and a longer, narrower diaphysis
- Acts as levers for movement
- Thicker compact bone in diaphysis
Short bones
- Close to equal width and length
- Mostly cancellous bones
- Weight bearing
Flat bones
- Functional usually for muscle attachment
- Protection
- Thin plates of compact bone
Irregular bones
- Various shapes and functions
- Not long
- Not round/square shaped
- Not just cancellous bone
- Not flat
- Often have hole
Axial skeleton
Bones of the core Protection of vital organs - Skull - Sternum - Ribs - Vertebral column - Sacrum - Coccyx
Appendicular skeleton
Bones of the limbs
Most important or movement
Pectoral girdle
Clavicle - stabilising strut
Scapula - free-moving, muscle attachments
Pectoral girdle
Hip bones - as coxae
Sacrum - pelvic bones + sacrum
Lots of weight bearing
Female pelvic cavity more circular
Organic extracellular components
Collagen (protein) Ground substance (proteoglycans) Function = resists tension
Inorganic extracellular components
Hydroxyapatite + other calcium minerals
Mineral component makes bone hard and resistant to compression
When bone has its organic components removed making it too flexible
Cellular component of bone
Makes up 2% of bone matrix
Four types of cells - Osteogenic cells, osteoblasts, osteoclasts, osteocytes
Osteogenic cells
Stem cells that produce osteoblasts
Osteoblasts
Makers - produce new bone matrix
Osteocytes
Maintainers - recycle protein and minerals from matrix
Osteoclasts
Destroyers - remove bone matrix
Osteons
Longitudinal unit within compact bone - pathway for nutrients to get to cells in ECM
Central canal
Contains blood vessel and nerves
Lamallae
- Series of cylinders formed of ECM around the central canal
- Forms shape of osteon
- Collagen fibres within lamallae resists forces
Lacunae
Lakes for osteocytes
Canaliculi
Channels for nutrients through ECM
Trabeculae
Series or group of partitions formed by bands or columns of connective tissue
Orientation of trabeculae
- Organisation of trabecular resists force from multiple directions
- Directs force from body weight in single direction down shaft
- Spreads force distally
Osteoporosis
- When osteopenia becomes serve and clinically significant
- Cancellous bone = trabeculae becomes thinner
- Compression fractures of vertebrae
Primary centres of ossification
- Diaphyses (shafts)
- Develop at different times depending on the bone
Secondary ossification centres
Epiphyses - same ossification process as primary centres
Seperated from diaphyses by an epiphyseal plate
What is a joint?
- Holds bone together
- Is where bone meets
- Involves bone shapes and soft tissues
- Allows free movements/control of movement
Cartilage composition
- Collagen fibers in a ground substance, chondrocytes in lacuna
- Blood vessels don’t penetrate cartilage
- Nutrients diffused through matrix by joint loading
Hyaline (articular) cartilage
- Collagen fibers are barely visible
- High water content in matrix
- Function = resist compression
- Smooth, friction-less surface
Functions of hyaline cartilage in joints
- Moulds to surface of bones where they articulate
- Friction-less, smooth movement
- Degrades with age
Fibrocartilage
- Collagen fibres form bundles throughout matrix
- Orientation of fibres aligns with stresses
- Function = resist compression and tension
Functions of fibrocartilage in joints
- Generally at articulations that experience both compression and tension
- Depending of articular surfaces
- Acts as a buffer/shock absorber
Ligaments
- Connect bone to bone
- Function = restrict movement (away from themselves)
- Mostly collagen, minimal elastin
Tendons
- Connect muscle to bone
- Function = facilitates and control movements
- Contraction of muscles transmitted to bone
Fibrous joints
- Tissue = DFCT
- Structure = ligaments
- Function = limit movement, provide stability
Cartilaginous joints
- Some movement
- Tissue = fibrocartilage
- Connected entirely by cartilage
- Various structures with special functions
Fibrous joints
- Tissue
- Structure = ligament
- Function = limited movement/stability
Cartilaginous joints
- Some movement
- Tissue = fibrocartilage
- Various stricture with special functions
Synovial joints
- Free moving
- Most limb joints
- Amount of an direction of movement us determined by joint structure
Synovial joint features
- Complex association of tissues and structures
- Facilitation of free movement and control of movement
- Bone ends determine the range of motion at a joint
- Hip vs knee
Plane joint
- Multiaxial
- Sliding and gliding
- Flat articular surfaces
Hinge joint
- Uniaxial
- Movements are flexion and extension
Pivot joint
- Uniaxial
- Movement is rotation
Condylar joint
- Biaxial
- Flexion and extension
- Rotation (when flexed)
Ellipsoid joint
- Biaxial
- Flexion and extension
- Abduction and adduction
- Circumdation
- No rotation
Saddle joint
- Biaxial
- Flexion and extension
- Abduction and adduction
- Circumdation
- Obligatory rotation
Ball and socket
- Multiaxial
- Flexion and extension
- Abduction and adduction
- Circumduction
- Rotation
Osmosis
Sugar moving froma high to low concentration through a semi-permiable membrane
Water in adult males
Water = 60%
Solids = 40%
Plasma = 4.5%
Other body fluids = <1%
Water in adult females
Water = 50%
Solids = 50%
Plasma = 4.5%
Other body fluids = <1%
What is plasma?
Liquid of the blood
Isotonic
The ECF and ICF are in balance, with the two solutions
Hypertonic
Amount of solute outside is too high
Shrinks
Water loss from ECF ecreases volume and makes the solution hypertonic with respect to the ICF
Hypotonic
Too much water
Swelling
Water moves from low concentration of solutes to restore osmotic equilibrium
Excitable tissues
Neurons and muscles - excitable membrane potential
Epithelial cells also have a membrane potential - but not excitable
Excitation is accompanied by action potential, disturbed along the cellular membrane
Cations (+)
A positively charged ion
Examples of cations
Na+, K+, Ca2+
Anions (-)
A negatively charged ion
Examples of anions
Cl-, proteins
Ion channels or pores
Channels which allow crossing over of ions between cells
Smooth muscle
Mainly line hollow organs (e.g. gut, blood vessles).
NOT under voluntary control
Cardiac muscle
Located only in the heart, it generates force to pump blood around the body.
NOT under voluntary control
Skeletal muscle
Applies force to the bones to control posture and body movements.
IT IS under voluntary control
Skeletal muscle: structural features
Skeletal muscle fibres are huge, mulitnucleate cells containing large amount of protein
Connective tissues ensheath the muscle fibres and connect fibres to the bone
Skeletal muscle is richly supplied with blood vessels
Skeletal muscle is richly supplied with nerve fibres
The sliding filament theory
Contractile proteins develop force by triggered molecule interaction. It allows association with myosin head with nearby thin actin filament followed by the flexing of the myosin head.
Neuromuscular junction (NMJ)
Myelinated axon of a motor neuron terminates at a single point on the muscle fibre, forms an excitatory synapse
A motor unit
Motor neuron cell bodies are in ventral part of spinal cord. A whole muscle is a collection of motor units
Muscle structure and function
Individual muscle fibre is an individual cell.
Muscle is comprised of multiple muscle fibres
Myofibre = muscle fibre
Neuromuscular transmission
The NMJ is a chemical synapse, so depolarisation at the nerve terminal results in release of neurotransmitter (ACh)
Chemical synaptic transmission step 1
Action potential triggers the opening of voltage-gated calcium channels
Chemical synaptic transmission step 2 (a&b)
a. Calcium ions diffuse in the axon terminal
b. Trigger synaptic vesivles to release ACh by exocytosis
Chemical synaptic transmission step 3
ACh diffuses across synaptic cleft, binds to ACh-gated sodium ion channels and produces a graded depolarization
Chemical synaptic transmission step 4
Depolarization ends as ACh is broken down unto acetate and choline by AChE
Chemical synaptic transmission step 5
The axon terminal reabsorbs choline from the synaptic cleft and uses it to synthesize new molecules of ACh
Muscle tension
Primary job of skeleton is to develop force and to apply it to the skeleton
Length tension curve
The amount of force a sacrmere can produce is maximal when overla between thick (myosin) and thin (actin) filaments is optimal
Rate coding and summation
The amount if force a fubre can produce is also proportional to the frequency of its stimulation
Recruitment
The amount of force a whole muscle can produce is a function of the force produced by each fibre AND the number of fibres activated
How much can muscle fibres shorten?
Up to 50%
Arrangement of muscle fibres
Arranged vertically between muscle tendons
Fibres oblique to muscle tendon - pennate
Reduced shortening but greater CSA
What is CSA
Number of muscle fibres
What is pennate?
More fibres into same space
Anatomical levers
Bones = lever
Joint = pivot or fulcrum
Muscle contraction = pull
Load = external or internal
Types of levers with muscle attachments
First = stabilise joint position Second = effective at overcoming loads Third = large range of movement and speed
Concentric
Muscle is active, develops tension
Change in joint position
Shorting of muscle
Isometric
Muscle is active, develops tension
No change in joint position
No change in length of muscle
Eccentric
An active muscle lengthening under load
Types of muscle role
Agonist
Antagonist
Stabilizer
Neutralizer
Agonists
Biceps brachii
Act concentrically - shortens
Antagonists
Triceps brachii
Act eccentrically - lengthens
Stabilizers
When a muscle is active to hold a joint still
Neutralizers
Muscle eliminates an unwanted movement caused by another muscle
Concentric actions of muscle
Anterior - flexion
Lateral - abduction
Medial - adduction
Posterior - extension
Gait cycle
- initial contact
- loading response
- mid stance
- terminal stance
- pre swing
- initial swing
- mid swing
- terminal swing
