Introduction to the limbs Flashcards
What is the function of the upper limbs ?
They enable the hand to be brought to any point in space and keep it steady.
State some features of the upper limbs
Highly mobile joints
Levers
What is the function of the lower limbs ?
Supports the body weight
Involved mainly in locomotion
State some features of the lower limbs
The bones are more robust
Joints are more stable
Briefly describe the development of the limbs
Week 4
- Ventrolateral body wall
- Contain cells from somites and lateral plate mesoderm
Where do the upper limbs bud ?
Opposite somites C5-T1
Where do the lower limbs bud ?
Opposite somites L2-S2
What buds first, the upper or lower limbs ?
The upper limbs. 2 days earlier
State the 3 types of muscle
Skeletal
Cardiac
Smooth
Where do limbs originate from ?
(usually) at the proximal end of the muscle, which remains fixed during muscle contraction.
Where is insertion of the limbs from ?
(usually) at the distal end of the muscle, which is moveable.
What happens to muscle when stimulated ?
The muscle contracts and tries to bring its 2 ends closer.
What happens when muscle contracts ?
The muscle shortens, and usually shortens in the insertion –> origin direction.
What is meant by isometric contraction ?
Muscle tone changes
(muscle “meter” - length is not changed)
What is meant by isotonic contraction ?
Muscle length changes
(muscle “tone” is not changed )
What are the 2 types of isotonic contraction ?
Concentric
Eccentric
What is meant by concentric contraction ?
Muscle contracts according to the sliding filament mechanism and shortens
What is meant by eccentric contraction ?
Muscle elongates whilst under tension due to an opposing force greater than the muscle generates.
How do concentric and eccentric contractions protect from injury ?
Eccentric contraction acts as a braking force in opposition to a concentric contraction to protect from injury.
Prime mover (muscles)
Muscles that play the primary role in moving a body part.
Agonist (muscles)
Muscle that acts directly to produce a desired movement.
Synergist (muscles)
Muscles which assist the prime mover but are doing less of the work OR prevent unwanted movements associated with the action of the prime movers.
Antagonist (muscles)
Muscles which directly oppose a movement
Fixator (muscles)
Muscles that provide the necessary support to assist in holding the rest of the body in place whilst the movement occurs.
What is fascia ?
A sheet of connective tissue
Briefly describe superficial fascia
Just beneath the skin
Contains adipose tissue
Briefly describe deep fascia
Ensheaths muscles but continuous
Sometimes named
State some functions of deep fascia
(6)
Facilitates contraction
Barrier between muscles
Compartments of muscles
Passages for nerves and vessels
Attachment for muscles
Holds tendons in place
What is the function of septa ?
Septae form potential spaces to allow passage of nerves and blood vessels
Function of deep fascia
Deep fascia sends septae between muscles to separate them into compartments.
What is a downfall of septae ?
Potential spaces are also potential tracts for infection spread and blood loss.
Briefly describe compartment syndrome
An injury to the muscle within a tough compartment may cause swelling and increased pressure that compresses the neurovascular bundles.
State some general rules about muscles in a compartment
Generally muscles in a compartment have…
- the same action
- the same nerve supply
State some features of deep fascia in the arm
The medial and lateral intramuscular septum separate into 2 compartments :
- anterior and posterior compartments
Function of the anterior compartment in the arm
Flexing movement (flexor)
Function of the posterior compartment in the arm
Extending movement (extensor)
What surrounds the arm ?
Brachial fascia
State some features of deep fascia in the forearm
The antebrachial fascia surrounds and separates the anterior and posterior compartments and forms an interosseous membrane.
Function of the anterior compartment in the forearm
Flexor - pronator
Function of the posterior compartment in the forearm
Extensor - supinator
Describe the formation of the carpal tunnel
At the wrist the interosseous membrane thickens to form a flexor retinaculum.
How does the deep fascia of the thigh differ from that of the upper limb ?
It is thicker that the upper limbs
What is the Iliotibial tract ?
The fascia lata (deep fascia) thickens laterally in the thigh to form the iliotibial tract.
What is the deep fascia of the thigh called ?
Fascia lata
Function of the iliotibial tract
Stabilises the hip and knee
What 3 compartments in the thigh are formed by septae ?
Anterior - Extensor
Medial - Adductor
Posterior - Flexor
What is the deep fascia of the leg called ?
Crural fascia
How is the interosseous membrane of the leg formed ?
The crural fascia fuses with the tibia
State the 3 compartments of the leg
Anterior - extensor
Lateral - everters
Posterior - flexor and plantar flexor
(posterior = deep and superficial)
What are neurons ?
Excitable nerve cells which transmit information as electrical signals (or action potentials)
What is a neurite ?
Either a dendrite or an axon
State the 2 types of neuron
Motor
Sensory
What are the 2 types of motor neurons ?
Somatic
Autonomic
What is a dermatome ?
An area of skin supplied by neurons from one spinal segment (spinal nerve)
What is a myotome ?
A muscle or groups of muscles supplied by neurons from a single spinal segment - usually having the same action.
Briefly describe rotation of the limbs
The upper limb rotates laterally from its in-utero position
The lower limb rotates medially
The dermatomes rotate too
Describe rotation of the upper limbs
Lateral rotation
- thumb moves from superior to lateral
- flexor muscle groups move to an anterior position
- extensors move to a posterior position
Describe rotation of the lower limbs
Medial rotation
- hallux moves from superior to medial
- flexor muscle groups move from an anterior to a posterior position
- extensors move to an anterior position
Describe the initial position of the thumb and hallux
Found on the cranial side of each limb, and both the palm and sole face anteriorly (or medially)
Describe the brachial plexus
Formed in axilla
C5-T1
Describe the lumbosacral plexus
Major feature of posterior abdominal wall
L1-S5
(L2-S2 for limb)
Where is the brachial plexus located ?
Upper limbs
What does the lumbosacral plexus supply ?
Supplies abdominal wall, pelvis and viscera
State the artery that supplies the upper limb
Subclavian artery
State the artery (arteries) that supply the lower limb
(COMMON) External iliac artery
- also some internal iliac artery
Briefly describe how veins drain blood
From superficial to deep via perforating veins
The back flow of blood is prevented by valves
Name superficial veins in the upper and lower limbs
UL :
- Median cubital
- Cephalic
- Basilic
- Superficial venous palmar arch
LL :
- Small saphenous
- Great saphenous
Describe deep veins
Accompany arteries
Usually as venue comitantes - taking the arteries name
What 3 things help blood return to the heart against gravity ?
Muscle pump
Arterial pulsation
Negative intrathoracic pressure
(also valves in veins)
What are some negative aspects of lymphatics ?
Allow the spread of metates or infection
What lymph node is associated with the upper limbs ?
Axillary
What lymph node is associated with the lower limbs ?
Inguinal
What is Hiltons law ?
A nerve innervating a particular muscle acting on a certain joint will also innervate the particular joint and skin overlying the muscle.
