Introduction to the musculoskeletal system Flashcards
Revision
What do axial bones consist of?
They are the bones of the skull.
The bones of the neck, including the cervical vertebrae and the hypoid bone.
The bones of the trunk (chest, abdomen and back).
(The axial skeleton essentially runs down the midline).
What are the two separate parts that the skeleton can be divided into?
The axial skeleton and the appendicular skeleton.
What bones does the appendicular skeleton consist of?
Bones of the pectoral girdle.
Bones of the upper limbs
Bones of the pelvic girdle.
Bones of the lower limbs.
What are the bones in the upper limbs?
1 long bone in the arm: the humerus
2 long bones in the forearm: radius and ulna (your thumb radiates away from your hand and the radius is on the same side as your thumb)
Hand: carpal bone (wrist)
metacarpals (palm) (meta=after metacarpals=after carpals)
phalanges (fingers)
What are the bones in the lower limbs?
1 long bone in the thigh: femur
2 long bones in the leg: tibia and fibula
foot: tarsal bones (hindfoot/midfoot)
metatarsals (forefoot) (meta=after metatarsals=after tarsals)
phalanges (forefoot-toes)
What is a bony feature?
A bony feature is something you find on bones (e.g. a groove, lump or bum) that is developed during bone growth and makes the bone functional, the best shape for the job.
What causes bony features?
Bony features are normally caused by an adjacent structure e.g. a tendon, a blood vessel, a nerve or another bone, which applies a force to the developing bone moulding it’s shape accordingly.
It can also sometimes be caused by an adjacent structure developing at the same time as the bone. The bone has to grow around the other structure forming a foramen (hole).
What are examples of bony features in the upper limb?
Greater tubercle (tuberosity) of the humerus. Styloid process of the radius (Anytime you see the word stylo you are looking for a little point, like a pen).
What is the skeleton made up of?
It is made up f a combination of bones and cartilage.
What is the definition of bone?
It is a hard connective tissue.
What are the functions of bone?
Support and protection of the body and organs
Calcium metabolism
Red blood cell formation
Attachment for skeletal muscles
What are the functions of cartilage?
It is less rigid than bone and so is located mostly but not exclusively where mobility is required, at articulations (joints).
Movement of the skeleton occurs at joints. How do the muscles allow the joints to move?
The skeletal muscles contract to move the bones.
Without joints we couldn’t move.
There are different types and subtypes of joints. What are the main 3?
Synovial (the most moveable)
Cartilaginous (the next most moveable)
Fibrous (the least moveable)
Each joint is a compromise between mobility and stability. what is the relationship between these?
Increased mobility = decreased stability
decreased mobility = increased stability
What is the name of the nerves that supply the joints and what is the result of their presence?
Joints have an excellent sensory nerve supply.
Sensory nerves detect some type of sensation.
This means that they hurt a lot when dislocated or affected by pathology e.g. arthritis.
What are the 4 sensations detected by the sensory receptors of the joint nerves?
Pain
Touch
Temperature
Proprioception (joint position sense), this can also be explained as an awareness of where your body is in space, e.g. allows you to close your eyes and touch your nose.
The arteries supplying joints arise from large named arteries located near the joint. these are called what?
Articular branches.
What type of arteries are common around the joint?
Periarticular (meaning around the joint) arterial anastomoses.
These are present in addition to the main blood supply. This helps to prevent the blood supply from being cut off.
What can happen to the arteries supplying joints, if the joint is dislocated?
The arteries supplying joints can be damaged by dislocations, dangerously compromising the blood flow to distal joints.
What are the roles of skeletal muscles?
Their primary role is to produce movement however, they also provide some structure and are involved in heat production.
Where are skeletal muscles normally found?
Deep in the deep fascia.
What is the deep fascia?
It is a tough fibrous connective tissue covering the body.
The shiny white appearance is the deep fascia
What are the layers that lead down to the skeletal muscle?
Epidermis (epithelium) is what we know as skin.
Next is the dermis made of collagen and elastic fibres.
Then is the superficial fascia (adipose tissue), this is a fatty tissue, the superficial fascia also has a bit of connective tissue.
The deep fascia is a really thick tough fibrous tissue covering the skeletal muscles. The shiny whit appearance is the deep fascia. Generally the muscles are found in the deep fascia but not always e.g. facial muscles.
What are the advantages of long muscle fibres?
They have a greater potential range of shortening.
They have a greater potential range of movement produced at a joint.
What happens when a skeletal muscle is strained?
When a skeletal muscle is strained/pulled some of the muscle fibres are torn. The more fibre torn, the worse the strain.
What are some of the many different types of skeletal muscles?
Circular generally known as sphynctor muscles e.g. orbicularis oculi
Fusiform e.g. biceps brachii
Flat with aponeurosis e.g. external oblique. An aponeurosis is essentially a flat tendon.
Pennate e.g. deltoid
Quadrate e.g. rectus abdominus.
Skeletal muscles are normally named according to a combination of what?
Shape Location Size Main body attachment Main movement e.g. biceps brachii (cep=head biceps = 2 heads and is in the arm region)
Skeletal muscles are usually attached to at least 2 points of attachment to the bone. What are these called and in general terms what will their positioning be?
The origin(s) on one side of a joint. Generally speaking the origin will be the most proximal point and the least moveable part. The Insertion(s) on the other side. This tends to be the more distal are and the most moveable part of the joint.
What is the only thing a skeletal muscle can do?
Move the origin and insertion closer together during contraction.
What happens to the muscle fibres during contraction?
During contraction, muscle fibres shorten along the long axis between the origin and insertion.
What is the only situation in which a skeletal muscle can move a joint?
Skeletal muscles can only move a joint if they cross the joint and attach to bones on either side.
What happens to muscles during contraction?
Muscles shorten during
What do tendons attach to?
They attach the muscle (usually) to bone.
What is the role of tendons?
They are found at either end of the muscle and non-contractile.
What is an aponeurosis?
A flattened tendon
They are most commonly associated with flat muscles.
It attaches muscle to soft tissue rather than bone.
What does the direction of movement on?
It depends on which side of the joint the muscle spasms.
What are the positions of the biceps brachii?
- spans the shoulder joint anteriorly, therefore it flexes the shoulder joint.
- Spans the elbow joint anteriorly therefore it flexes the elbow joint.
- Spans the proximal radioulnar joint anteriorly producing supination of the forearm.
How can the action(s) of any given muscle can be worked out?
Which joint is spanned.
The long axis of the muscle fibres
The aspect of the joint that is spanned.
The shapes of the articular surfaces of the joint.
(The biceps brachii does a little bit of flexion at the shoulder but mainly flexes the elbow joint)
What determines the possible movement of a joint?
The shape of the articular surface.
What permits circumduction of the shoulder?
The shallow socket of the glenoid fossa of the scapula.
Why is the mobility in the shoulder more than in the hips and what is the consequence?
Your hips are a synovial ball and socket joint.
The socket joint at the hip is far more tight than in the shoulder, meaning that the mobility in the shoulder is much more. Because the mobility in the shoulder is more, it is less stable than the hips.
What movement can the deltoids perform and what muscles control these?
- Posterior fibres of deltoid: allow for extension of the shoulder.
- Middle fibres of deltoid: abduction of the shoulder.
- Anterior fibres of deltoid: Flexion of the shoulder.
For the biceps brachii, what is the: name attachments main actions nerve supply how to clinically test it?
Biceps brachii From scapula to radius. Flexion of shoulder joint, flexion of elbow joint, supination of radioulnar joints. Musculocutaneous nerve. Biceps jerk reflex.
What clinical examinations do medical professionals carry out to examine skeletal muscles?
Testing the ability to move and the power of the movement.
Testing the muscle itself and the nerve(s) supplying it.
These can be carried out by asking the patient to make movements.
Or by testing reflexes.
What do muscles require to move?
Muscles can only move if they have a functioning nerve supply.
What are the two types of reflexes?
Protective: Rapid, predictable, involuntary reactions to “danger”
Automatic: Movement made unconsciously by nervous system and muscles.
What are the two main reflexes involving skeletal muscles?
Stretch reflex
Flexion withdrawal reflex
What is the flexion withdrawal reflex?
This is where you touch something potentially damaging.
There is a sudden flexion to withdraw from the danger.
Is the brain involved in a flexion withdrawal reflex?
Nerve connections are at a spinal cord level, the brain is not involved.
What are examples of stretch reflexes?
“biceps jerk”, “triceps jerk”, “knee jerk” & “ankle jerk” reflexes.
How do you carry out stretch reflex examinations?
A tendon hammer is used to apply a brief, sudden stretch to the muscle via it’s tendon.
The normal reflex response to being stretched is to contract.
Reflexes contraction in a brief twitch of the muscle belly or a movement in the normal direction.
Reflexes are protective to overstretching.
What structures do ligaments connect to?
Ligaments attach to bone
What structures do tendon’s attach to?
Tendons attach to muscle and bone.
What is the process that results in a deep tendon reflex?
Sensory nerve from muscle detects the stretch & tells the spinal cord.
Synapse in the spinal cord between the sensory & motor nerves.
The motor nerve from the spinal cord passes the message to the muscle to contract.
The neuromuscular junction is the synapse where the motor nerve communicates with the skeletal muscle.
The whole route taken by the action potentials is called the reflex arc.
Brain prevents reflex from being overly brisk.
The brain prevents the reflex from being overly brisk.
A normal stretch reflex indicates that what are functioning normally?
The muscle It's sensory nerve fibres It's motor nerve fibres The spinal cord connections between the two The neuromuscular junction "descending controls" from the brain.
What causes paralysis?
A muscle without a functioning motor nerve supply is “paralysed”.
What is paralysis?
A paralysed muscle cannot contract.
How can you tell that a muscle is paralysed on examination?
A paralysed muscle cannot contract and on examination the muscle would have reduced tone.
What is spasticity?
This is a muscle that has an intact and functioning motor nerve. However the descending controls from the brain are not working.
(This is where the muscle is being allowed to continuously overstretch and so is very tight).
How can you tell a muscle is spastic on examination?
On examination the muscle would have increased tone.
What is atrophy?
It is the “wasting” of muscles. Muscle fibres (myocytes) become smaller, reducing the muscle’s bulk.
What does it develop as a result of?
Immobilisation after fracture
Damage to motor nerve supply
“couch potato”
What is hypertrophy?
It is the opposite to atrophy
Skeletal muscles enlarge
Each individual myocyte enlarges.
(Hypertrophy is where the cells are getting bigger).
