Session 1: Basic Concepts in MSK Flashcards
Give some functions of bone.
Support Protection Metabolic (storage and release of calcium and phosphate) Storage Movement Haematopoeisis
What do bones store?
They are store calcium and phosphate. But also store important growth factors and cytokines like insulin-like growth factors etc.
Give some functions of skeletal muscle.
Locomotion Posture Metabolic (fast twitch/slow twitch) Venous return Heat production Continence (muscles of the pelvic floor are responsible for the maintenance of urinary and faecal continence)
Give examples of connective tissue in the musculoskeletal system.
Tendons Ligaments Fascia Cartilage (Hyaline and fibrocartilage most commonly) Synovial membrane
Give functions of tendons.
They connect muscle to bone. Their role is force-transmission from the contracting the muscle to the bone to which they are attached.
Give functions of ligaments.
They connect bone to bone. They support joints and prevent and excessive range of movement.
Give functions of the fascia.
To envelop groups of muscles and divide body parts into anatomical compartments. They can also serve a protective function for the underlying structure.
What is the fascia called in the thigh?
It’s called fascia lata and it is very tough.
Give functions of the hyaline cartilage.
It’s found on the ends of bones contributing to the joints. It’s smooth and creates a near to frictionless motion at the joint.
Give functions of fibrocartilage.
Higher collagen content than hyaline cartilage. It plays an important role in shock absorption and also bony congruity. Menisci e.g.
What is congruity?
It’s creating a complementary shape of bony surfaces to improve stability.
Give functions of the synovial membrane.
Tissue found within joints, bursar and tendon sheaths. It produces synovial fluid to lubricate the joint and make it as close to frictionless as it gets.
What other cells than the most common are found in bone?
Fibroblasts, macrophages, mast cells and adipocytes.
Briefly outline the ECM of bone.
In the ECM CaPO4 can be found also called calcium phosphate. It mineralises the extracellular matrix. In the ECM you can also collagen, not very much elastin, but also ground substance containing water and GAGs and proteoglycans.
What does the calcium phosphate do in terms of stability?
It gives great compressive strength.
What does the collagen do in terms of stability?
It gives great tensile strength.
How many bones can be found in the adult human?
206 bones.
How many vertebrae bones can be found?
26 vertebrae.
How many upper limb bones can be found?
64 in total. 32 on each side.
How many lower limb bones can be found?
62 in total. 31 on each side.
There are two divisions of skeleton, which?
The axial and appendicular skeleton.
Explain the axial skeleton.
It forms the longitudinal axis of the body.
Explain the appendicular skeleton.
Comprises the bones of the upper and lower limbs.
Where are long bones mostly found?
In the appendicular skeleton.
Give a function of a long bone.
They act as rigid levers and are position in space by the action of the muscles.
What is the medullary cavity lined with?
Endosteum
What do arteries enter the bones via?
Foramens also called nutrient foramen.
Where can the foramen usually be found?
Near the middle of the diaphysis.
Where can you find short bones?
Located in wrist and ankle joints so in the appendicular skeleton.
Give functions of short bones.
Provision of stability. Facilitating a great range of movement.
What are the functions of flat bones?
To provide protection of internal organs such as brain, heart and pelvic organs. Flat bones can also provide larges areas of attachment for muscles.
Where can you find irregular bones?
Vertebrae for protection of the spinal cord.
Where can you find sesamoid bone?
In patella for example embedded in tendon.
What are processes of bone?
Prominent projections of a bone. Something that sticks out of it and usually provides attachment for a tendon/muscle. They can also be called for example tubercle or protuberance.
Give example of articulating processes.
Head
Condyle
Facet
What is head?
A rounded articular projection supported by a neck. For example the head of humerus.
What is condyle?
A large knuckle-like articular projection. (e.g. medial condyle of the femur.) In the case of the femur the condyle is distal to the head.
What is facet?
A smooth flat surface like the superior and inferior articulating facets of the vertebrae.
Give examples of non-articulating processes. What are their functions?
They are usually the result of traction on the developing bone by muscles and ligaments etc. Epicondyle Trochanter Tubercle Tuberosity Crest Line Spine
How does force on bone relate to prominence of non-articulating processes?
The more force on a bone the more prominent a non-articulating process will become.
What is epicondyle?
Smaller projections above the condyle. These are usually attachment sites for muscles and ligaments.
What is trochanter?
A blunt projection that is only found on femur. Slightly below and lateral to the head.
What is tubercle?
Small knob-like rounded process. Found in e.g. humerus.
What is tuberosity?
Large, often rounded usually roughened process. These are usually an attachment site.
What is crest?
Prominent border or ridge like the iliac crest.
What is line?
A less prominent ridge than a crest.
What is spine?
Sharp slender process like the spinous process of a vertebra.
What are depressions of bone?
They can be indents in bone that proves a passage for blood vessels, nerves, lymph or other soft tissues.
Give example of depressions.
Fovea Sulcus/groove Fossa Cavity Notch
What is fovea?
A pit-like landmark like the fovea wapitis of femur.
What is sulcus/groove?
Furrow that accommodates soft tissue such as blood vessels, nerves or tendons.
What is fossa?
Basin-like depression
What is cavity?
A spacious open area.
What is a notch?
A C or U shaped depression providing passage for vessels and other soft tissues.
Explain openings.
Openings are found in the bone which allows passage of vessels and nerves primarily.
Give example of openings.
Fissures
Foramen
Canals
What are fissures?
Narrow slit-like openings between adjacent parts of bones though which blood vessels or nerves can pass.
What are foramen?
A hole or a window in the bone.
What are canals?
Not only a hole but tube-like passageways.
What are periosteal arteries and what do they do?
They are found in the periosteum and supply the periosteum and the outer third of the cortex of the bone.
If the periosteal arteries only supply a third of the cortex, what supplies the rest?
They are supplied by the nutrient artery.
How do the arteries in the bone differ in children and adults?
In children the epiphyseal and metaphyseal arteries have not fused yet meaning that the epiphyseal artery supplies all of the epiphysis and the secondary ossification centre.
In adults however the metaphyseal arteries connect with the epiphyseal arteries fuse by the formation of an anastomosis.
What is avascular necrosis?
The death of bone due to loss of its blood supply.
Give common causes for avascular necrosis?
Fracture Alcoholism Excessive steroid use Trauma Radiation Thrombosis Hypertension Decompression sickness
How do bone remodelling relate to force entered on the bone.
The more force exerted on a bone the more bone remodelling will occur and thicken the bone.
Define joint.
An articulation between two or more bones.
What is the trade-off of joints?
It’s trade-off between mobility and stability. The more mobile a join is the less stable it is.
What three structural classification of joints are there?
Fibrous joints
Cartilaginous joints
Synovial joints
Explain fibrous joints.
Fibrous joints are united by collagen fibres. They have very limited mobility but a high stability.
Give examples of fibrous joints.
Sutures of the skull
Inferior tibiofibular joint (at ankle)
Radioulnar interosseous membrane in the forearm
Posterior sacroiliac joint in the pelvis
Joint between roots of a tooth and the bone of the mandible or maxilla.
Explain cartilaginous joints.
These are joints that use cartilage to unite bones, they act as glue. They are typically found in the midline of the body and also in the epiphyseal plates of long bones. There are primary and secondary cartilaginous joints.
What are primary cartilaginous joints? Give an example.
They are united by hyaline cartilage and are completely immobile. They can be found in the first sternocostal joint between the sternum and the first rib, xiphisternal joint and the epiphyseal growth plates of the long bones.
What are secondary cartilaginous joints? Give an example.
They are also known as symphyses. The articulating bones are covered with hyaline cartilage with a pad of fibrocartilage between them. These can be found in the pelvis like the symphysis pubs, also the intervertebral discs and the manubriosternal joint.
Explain synovial joints.
A synovial joint has a joint cavity that contains synovial fluid. This synovial fluid comes from the synovial membrane. The synovial fluid provides lubrication and makes the joint almost frictionless. This also gives a high degree of mobility.
Explain the structure of synovial joints.
Covered with hyaline cartilage providing smooth movement and resistance to compressive forces within the joint. There is a fibrous capsule surrounding the join as well, it is composed of collagen. The capsule usually completely enclose the joint. The fibrous capsule is also continuous with the periosteum covering the surface of the adjacent bones. It has a synovial membrane which is a highly vascularised membrane that produces synovial fluid. It lines tendon sheaths and bursar and osseous surfaces but not articular cartilage or menisci.
Explain the functions of the fibrous capsule.
It gives stability to the joint and permits movement by still resisting dislocation.
The fibrous capsule doesn’t always completely enclose the joint. It is sometimes interrupted. By what?
By something called synovial protrusions. These form bursae.
The hyaline cartilage does not always line the articular surfaces. What are some exceptions?
Acromioclavicular, sternoclavicular and tempermandibular joints. They are covered with fibrocartilage instead.
There are very many types of synovial joints which dictates which movements they can perform. List them.
Plane joints Hinge joints Pivot joints Saddle joints Condyloid joints Ball and socket joints
Explain plane joints.
Plane joints can only move in a plane. They occur when two flat surfaces slide against each other. They can move as they want in a plane and rotate in that plane as well.
Give examples of plane joints.
Caprbal bones of the wrist and the facet joints which are joints between vertebral articular processes of the spine.
Explain condyloid joints.
They are similar to plane joints but they are two ovals put together. They are also a little bit like a ball in a socket but it’s oval so it doesn’t have the full mobility.
Give examples of condyloid joints.
Atlanto-occipital joint at the base of the skull and the radoiocarpal joint between the radius and the carpal bones of the wrist.
Explain saddle joints.
They are composed by two bones that fit together like a rider in a saddle or the Pringles analogy. It allows movement in two different planes the the same time with sliding.
Give an example of a saddle joint.
The first carpometacarpal joint at the base of the thumb.
Explain hinge joints.
They allow stable flexion and extension without sliding or deviation. Here movement only occurs in one single anatomical plane. It looks like a tube fit into a claw.
Give an example of a hinge joint.
The elbow joint between the humerus and ulna.
Explain pivot joints.
They are composed of a peg within a ring-shaped hole. It allows rotational motion without having to glide. This means that it allows rotation without bending our sideways displacement.
Give an example of a pivot joint.
The Atlanto-axial join which can be found between the first and second cervical vertebrae. It allows the head to rotate whilst maintaining the stability of the head on the neck.
Explain ball and socket joints.
Allow stable movement in several directions without slippage. These are the most mobile type of synovial joint and often permit flexion-extension, abduction-adduction, lateral rotation-medial rotation and circumdiction.
Give examples of ball and socket joints.
The hip and shoulder joints.
What is a bursa?
A small sac lined by synovial membrane. They are filled with synovial fluid and found around most major joints in the body. They work as a fusion between bones and tendons and muscles around a joint and also they reduce friction between the bones.
What are tendon sheaths?
Elongated bursae that wrap around a tendon and reduce the friction.
Explain the structure of the synovial fluid.
A clear or pale yellow, vicious and slightly alkaline at rest fluid. The volume in a knee join for example is less than half a milli litre. It contains hyaluronic acid, lubricin, proteinases and collagenases. Its main function is to reduce friction, shock absorb and to transport neutrons to the articular cartilage of the joint.
Give examples of joints that do not have synovial covering.
The intra-articular fibrocartilaginous menisci and the joints between the vertebrae containing intervertebral discs which also have fibrocartilage.
The articular cartilage is avascular and the fibrous capsule and ligaments have poor blood supply. So how does it get its nutrients?
The synovial membrane has rich blood supply which maintains a flow of nutrients via the synovial fluid to the articulating cartilaginous surfaces.
Give some factors that affect the range of motion of joints.
Structure or shape of the articulating bones
Strength and tension of the joint ligaments
Arrangement and tone of muscles around the joint
Apposition of neighbouring soft tissues
Effect of hormones
Disuse of a joint
Explain the embryological development of synovial joints.
At around week six the mesenchyme will differentiate into hyaline cartilage that will later on be the model for the bone. In the middle of that hyaline cartilage the cells will undergo apoptosis (programmed cell death). This leaves a space that will then be filled with meniscal and ligament progenitors. Lining the bone will be articular progenitor and at the collar there will be synovial progenitor. Later on this will form meniscus and ligaments in the middle, synovium surrounding anything that is no the articular cartilage.
How does the trade-off between power and range of movement work?
Less power is needed if there is a long lever, however this means that it will only cause a limited range of displacement. A smaller level might need more power to work but might cause greater displacement.
How many skeletal muscles are there in the human body? (roughly)
- Most of them are bilateral pairs
What are bilateral pairs?
Left and right gluteus Maximus muscles for example. A lot of muscles have a bilateral pair meaning there are roughly around 320 unique muscles in the body.
Can muscles pull?
Yes
Can muscles push?
No, they can never push.
What is another key concept to remember related to muscles?
Muscles can only act on joints that they or their tendons cross.
How many attachments to the bone do muscles have?
Apart from the circular muscles all muscles have at least two sites of attachment. One of them is the origin, and one of them is the insertion.
Define origin.
The stationary anchor point, it is usually sited proximally in the limb.
Define insertion.
The mobile attachment point, it is usually sited distally in the limb.
What does it mean when someone says that muscle contraction is symmetrical?
There is an equal exertion of force on the origin and the insertion.
What happens at muscle inversion?
The usual insertion point becomes fixed and the usual origin becomes mobile. The position of the origin and insertion has become inverted.
What does the action of a muscle on a joint depend on?
It is a function of the orientation of its fibres and the relation of those fibres to the joint.
What does the action of a muscle on a joint depend on?
It is a function of the orientation of its fibres and the relation of those fibres to the joint.
The action of a muscle is a function of the starting position of the joint.
In what direction can a muscle contract?
Only in the direction of the muscle fibres.
What are agonist muscles?
The prime muscles that are responsible for a particular movement.
What are antagonist muscles?
The muscles that oppose the particular movement are antagonists. For example in flexing the biceps the biceps is the agonist and the antagonist is the triceps.
What are synergists?
Muscles that act to assist the prime mover (agonist). synergists cannot perform the desired movement on their own.
What are neutralisers?
These are muscles that prevent the unwanted actions that an agonist can perform. An example is that gluteus Maximus can stabilise the hip joint in the extended position while rectus femurs extends the knee.
What are fixators/stabilisers?
They act to hold a body part immobile while another body part is moving.
What different types of muscle contraction is there?
Concentric
Eccentric
Isometric
What is concentric contraction?
When a muscle shortens as it contracts. An example is flexing the elbow from full extension to full flexion by concentric contraction of the biceps brachii. These are the most common type of muscle contraction.
What is eccentric contraction?
When a muscle lengthens as it contracts. For example this occurs when you are lowering a dumbbell held up by the bicep. The bicep is still working as it controls the rate of which the dumbbell is lowered.
Also as you walk downhill, to prevent you from falling over the quadriceps is contracted eccentrically. This is common in injury.
What is isometric contraction?
When the muscle doesn’t shorten nor lengthens as it contracts. This occur when you hold a weight at a constant height, for example carrying a box.
Give examples of how the arrangements of skeletal muscle fibres can be.
Fusiform (biceps brachii) Strap (rectus abdominis) Triangular (pectoralis major) Unipennate (palmar interosseous) Bipennate (recuts femoris) Multipennate (deltoid) Circular (Orbicularis oculi)
What are the three main categories of muscle that run in parallel?
Strap, fusiform and triangular.
Explain pennate muscles.
They have one or more aponeuroses running through the muscle body from the tendon and the fascicles of muscle fibres attach to these aponeuroses at an angle to the direction of movement.
What is special about unipennate?
All the fascicles are on the same side of the tendon.
What is special about bipennate?
Fascicles can be found on both sides of a central tendon.
What is special about multipennate?
A central tendon branches.
What is special about compartments separated by fascia?
Each compartment usually share a common innervation and action.
Briefly explain fascia.
A region of the limb that contains muscles but also nerves and blood vessels. Each compartment usually has a separate nerve and blood supply to its neighbours. It also protects the muscles, an example is the fascia lata which is the deep fascia of the thigh. It is a dense irregular tissue that is very tough.
What is special about connective tissues?
They are all physically connected with each other. An example is that there is continuity between the periosteum, joint capsule, tendons, epimysium and the collagen matrix of the bone.
What is superficial fascia?
It’s called superficial fascia by anatomists and subcutaneous fatty layer or hypodermis by histologists. It stores fat, and water and is a passage way for lympathics, blood vessels and nerves.
What is deep fascia?
A thickened elaboration of the epimysium even loping the muscle compartments. It comprises of collagen and elastin fibres in a wavy pattern.
What do tendons do?
Connect bone to muscle
What do ligaments do?
Connect bone to bone.
What do aponeuroses do?
Connect muscle to muscle. Sometimes to bone in the example of the abdominal wall.
Briefly outline tendons.
Consist of dense regular connective tissue fascicles, enclosed within dense irregular connective tissue sheaths. They are anchored to bone by sharpey’s fibres. Low ratio of elastin to collagen.
Why do tendons heal poorly?
Because they have poor blood supply. They also have a low water content which limits the diffusion of nutrients and further impedes the healing process.
Briefly outline ligaments.
Comprise dense regular bundles of connective tissue which is mostly collagen. It is protected by dense irregular tissue.
What is the major role of ligaments?
To help stabilise joints and limit their range of movement.
Briefly outline aponeuroses.
Sheet-like structures that are histologically similar to tendons. Connect muscle to muscle. Found in the head for example connecting the frontal and the occipitals muscles of the scalp.
What is Hilton’s law?
The nerves supplying the joint capsule also supply the muscles moving the joint and the skin overlying the insertions of these muscles. This means that if you know the nerve supply of the muscles that move the join, you can also work out the nervy supply of the joint capsule itself.
What are segments in embryonic development?
Humans are built from a repeating pattern of subunits which are called segment that are arranged along the longitudinal axis. This is a crucial developmental process involved in patterning and segregation of groups of cells.
What is segmentation controlled by?
Hox genes.
What do Hox genes do?
They determine the different types of vertebrae that will form in a body segment and the type of limb that will develop from a limb bud.
What is a mutation of the Hox genes?
It is an example of a homeotic mutation where the tissue is altered from their normal differentiation pattern that can cause structure to form in unusual locations. Since Hox genes also govern digit development a mutation can cause an extra finger or toe, or one too little. It can also cause the existence of an extra rib for example as well.
Why can an extra rib be a problem?
It can compress the nearby arteries, veins or nerves that are supposed to pass through that location or close to it.
What is this condition called where there is compression of arteries etc by an extra rib due to Hox genes?
Thoracic outlet syndrome.
How do the upper limbs and the lower limbs relate regarding similarity?
They are very similar. They have one proximal bone first, then two distal, then short bones (carpals and tarsals) then 5 metatarsals and metacarpals and then 5 toes and 5 fingers.
What are the limb buds? When do they first appear?
They are the precursors of the limbs. They look like blobs sticking out of the body. They develop at the fourth week.
What do the limb buds consist of?
A mass of mesenchyme covered by a layer of ectoderm. At the tip of the bud the ectodermal cells divide to form an apical ectodermal ridge.
How do the limb buds elongate?
By proliferation of mesenchyme.
When does endochondral ossification start?
At the twelfth week of development.
How do the upper limbs and the lower limbs rotate?
They rotate in opposite directions and also to different degrees. Upper limb rates externally (laterally) through 90 degrees on its longitudinal axis. Elbows will point posteriorly.
The lower limbs rotate internally or medially through almost 90 degrees. Knees will point anteriorly.
