Introduction to the limbs Flashcards
What are the 3 functions of the upper limbs?
- They have almost no locomotor function, however they can be used as a locomotor prop (e.g Crutches to walk)
- Highly mobile joints
- Leavers/allows hand to be brought to any point in space and kept steady
What are the 2 key features of the upper limbs?
They are less stable but highly mobile
What are the 4 functions of the lower limbs?
- Support body weight
- Involved mainly in locomotion
- The bones are more robust
- Joints are more stable
Where do limbs develop from in a foetus and when?
The upper and lower limb buds
32-35 days
What develops after the limb buds grow?
The digital rays develop which will later become digits (fingers)
42-49 days
When and where do limbs develop?
Around week 4 of development, specialised cells migrate from somites and the lateral plate of the mesoderm and limb buds form where the arms and legs will develop
How does the upper limb develop?
The upper limb develops with the thumb pointing superiorly
What are the 3 different types of muscles?
Skeletal muscle, Cardiac muscle and Smooth muscle
What is the Origin?
The origin is usually the proximal end of the muscle which remains fixed during muscular contraction, making it more stable
What is the Insertion?
The insertion is usually the distal end of the muscle which is moveable, making it less stable
What happens to a muscle when stimulated?
The muscle contracts and shortens, trying to bring its two ends closer (Insertion and Origin)
What muscle moves closer to the other during a muscle being stimulated?
The muscles usually shorten in the Insertion -> Origin direction, so insertion becomes closer to the Origin
What is Isometric muscle contraction?
Increase in muscle tone but muscles don’t change in length or shorten
What is an Isotonic muscle contraction?
Muscle length changes so the muscle wither elongates or shortens but the muscle tone is not changed
Give an example of Isometric muscle contraction?
Carrying an object in front of you
Give an example of Isotonic muscle contraction?
Walking and running
What are the 2 varieties of Isotonic contractions and their differences?
Concentric contraction - Muscle contracts according to the sliding filament mechanism and shortens
Eccentric contraction - The muscle elongates while under tension due to an opposing force greater than the muscle generates - Works as a breaking force in opposition to a concentric contraction to protect from injury (E.g - Bicep Eccentric contraction prevents dropping of weight)
What is a prime mover?
A muscle/muscles that play the primary role in moving a body part
What is an Agonist muscle?
A muscle/ muscles that act directly to produce a desired movement - Aids the prime mover
What are Synergist muscles?
Muscles which prevent unwanted movements associated with the action of prime movers
What are Antagonistic muscles?
Muscles which directly oppose a movement (E.g - flexing elbow, the muscles on back resist to prevent hyperextension
What are Fixating muscles?
Muscles that provide the necessary support to assist in holding the rest of the body in place while movement occurs (Stabilises Origin or Insertion)
What is Fascia and its 2 subdivisions and their properties?
Fascia is a sheet of connective tissue (1 continuous sheet with 2 layers)
Superficial Fascia;
- Just beneath the skin and contains Adipose tissue (Fat)
Deep (investing) Fascia;
- Ensheath muscles but are continuous
- Help/facilitate contractions
- Barrier between muscles
- Compartment muscles and neurovascular bundles
- Passages for nerves and vessels
- Point of attachment for muscles (e.g by forming Interosseous membranes - fascia running from bone to bone in arm)
- Becomes thicker in structures (e.g wrist joint) to hold tendons in place (by forming Rentinaculae
What runs between muscles and why?
Septae to separate muscles into compartments for a group of muscles of similar function and vessels/neurovascular bundles
What do Septae form that is an advantage and disadvantage?
Septae form potential spaces to allows the neurovascular bundle to pass and to protect it.
However, potential spaces are also potential tracks for infection spread and blood loss
What is compartment syndrome and why is it important?
Compartment Syndrome is an injury to the muscle within a tough compartment which may cause swelling and increased pressure that compresses the neurovascular bundles
This is a surgical emergency as there is compromised circulation
What divides the arm into an anterior and posterior muscular compartment?
The intermuscular septae
What is the anterior compartment in the arm also referred to as ?
The flexor as the muscles flex the elbow
What is the posterior compartment in the arm also referred to as ?
The extensor as it extends muscles in the elbow
What forms into what membrane which separates the forearm into anterior (flexor) and posterior (extensor) compartments?
The antebrachial fascia forms into the interosseous membrane to separate the forearm into anterior (flexor) and posterior (extensor) compartments
What is in between the flexor retinaculum and what does this contain?
The carpal tunnel which transmits the tendons of the flexors to the fingers and the median nerve
How many compartments does the arm have?
2
How many compartments does the forearm have?
2
How many compartments does the thigh have ?
3
How many compartments does the leg have ?
4
How does fascia vary from arm to leg?
Lower limb fascia is thicker and called fascia lata
What does the fascia lata thicken into laterally in the thigh?
The iliotibial tract
