Introduction to the Limbs Flashcards
What is special about the functions of the upper limb of a human compared to the equivalent structure on a quadruped?
– has almost no locomotor function
– has a great degree of freedom of movement
It is an organ for grasping and manipulating
What defines the structure and function of the upper limb?
Highly mobile joints
Levers
Enable the hand to be brought to any point in space and keep it steadily
What are the functions of the lower limb?
Supports the body weight
Involved mainly in locomotion
The bones of the lower limb are more robust than the bones and joints of the upper limb
From where and when do the limbs develop?
~Week 4 of development, specialized cells migrate from the somites and the lateral plate mesoderm
Limb buds form where the arms and legs will develop.
What are the three types of muscles in regards to their structure?
Skeletal muscles, Smooth muscles, Cardiac muscles
Where can the origin of a muscle normally be found?
usually the proximal end of the muscle, which remains fixed during muscular contraction
Where can the insertion of the muscle normally be found?
usually the distal end of the muscle, which is movable
What happens when a muscle is stimulated?
a muscle contracts and tries to bring its two ends closer.
In what direction do muscles normally contract/shorten?
in the Insertion -> Origin direction
What are the two types of muscle contraction?
Isometric contraction
Isotonic contraction
What are the two types of isotonic contraction?
A. Concentric contraction
B. Eccentric contraction
What is eccentric contraction?
When the muscle elongates while under tension due to an opposing force greater than the muscle generates
When does eccentric contraction occur?
Occurs as a braking force in opposition to a concentric contraction to protect from injury
(lowering a dumbbell)
What is concentric contraction?
Muscle contracts according to the sliding filament mechanism and shortens
(lifting a dumbbell)
What are the 5 types of muscle in regards to their purpose in a movement?
- Prime mover
- Agonist
- Synergist muscles
- Antagonistic muscles
- Fixating muscles
What is a prime mover?
Muscle(s) that play the primary role in moving a body part
What is an agonist?
Muscle(s) that acts directly to produce a desired movement
What are synergist muscles?
Muscle(s) which prevent unwanted movements associated with the action of the prime movers
What are antagonistic muscles?
Muscle(s) which directly oppose a movement
What are fixating muscles?
Muscle(s) that provide the necessary support to assist in holding the rest of the body in place while the movement occurs
What are the two different kinds of fascia in regards to their location?
Superficial fascia and
Deep (investing) fascia
What are the features of superficial fascia
- Just beneath the skin
* Contains adipose tissue
What are the features of deep (investing) fascia
- Ensheath muscles but continuous
- Facilitate contraction
- Barrier between muscles
- Compartments of muscles
- Passages for nerves and vessels
- Attachment for muscles (eg. by forming Interosseous membranes)
- Hold tendons in place (by forming Retinaculae)
What are retinaculae?
A retinaculum (actual plural retinacula) is a band of thickened deep fascia around tendons that holds them in place
What do deep fascia form between the muscles?
septae between the muscles to separate them into compartments
What do septae form?
potential spaces to allow passage of nerves and blood vessels
What is compartment syndrome?
An injury to the muscle within a tough compartment may cause swelling and increased pressure that compresses the neurovascular bundles
Where are the deep fascia of the arm (medics arm not layman’s)?
The intermuscular septae divide the arm into an anterior (flexor) and a posterior (extensor) muscular compartment
What are the two septae of the arm and where are they?
The lateral and medial intermuscular septae, both join the humerus and run roughly along the coronal plane, with the lateral intermuscular seta slightly posterior
What are the fascia of the atebrachium?
The antebrachial fascia forms the interosseous membrane that separates anterior (flexor) and posterior (extensor) compartments
Carpal tunnel
What are the deep fascia of the thigh?
Called fascia lata
The fascia lata thickens laterally as the Iliotibial Tract, and sends septae to divide the thigh into anterior (extensor), medial (adductor) and posterior (flexor) compartments
How is the invested fascia of the lower limb different from the invested fascia of the upper limb?
Deep fascia of the lower limb is thicker
What are the deep fascia of the leg(medics not layman’s)?
Fascia Lata -> Crural fascia The Crural Fascia - fuses with the tibia - forms the interosseous (IO) membrane - send septae to divide the leg into anterior (extensor), 2 posterior (superficial and deep flexor) and lateral (peroneal) compartments
What are neurons?
Excitable nerve cells which transmit information as electric signals or “action potentials”
What structures make up a typical neuron?
A typical neuron has a cell body (soma) and neurite(s). Neurite is either a dendrite or an axon
What is an axon?
is single, can be as long as 1 m, covered with myelin or Schwann sheath
What are dendrites?
multiple, thin, short extensions
What two functions may a neuron have?
motor or sensory
What two functions may motor neurons have?
somatic or autonomic
Where is the sensory root?
The posterior (dorsal) root/posterior (dorsal) radix to the dorsal root ganglion
Where is the motor root?
The anterior (ventral) root/anterior (ventral) radix to the sympathetic ganglion
What do the posterior and anterior roots join to form?
The spinal nerve
What is a dermatome?
the strip of skin supplied by 1 spinal nerve
What is a myotome?
the skeletal muscle or group of skeletal muscles supplied by 1 spinal nerve
Describe the initial position of the limbs in development
both the thumb and hallux are on the cranial side of each limb, and both the palm and sole face anteriorly
Describe the rotation of the upper limb in development
The upper limb rotates laterally from its in-utero position
• Thumb moves from medial to lateral
• Flexor muscle groups move to an anterior position
• Extensors move to a posterior position
Describe he rotation tf the lower limb in development
The lower limb rotates medially :
• Hallux moves from lateral to medial
• Flexor muscle groups move from an anterior to a posterior position
• Extensors move to an anterior position
What else rotates during the rotation of the limbs in development?
The dermatomes
Where do the spinal nerves emerge from?
intervertebral foramina
Where do C1 to C7 spinal nerves emerge from?
intervertebral foramina above respective vertebrae
Where does the C8 spinal nerve emerge from?
below C7 vertebra
Where do T1 and all lower nerves emerge from?
below respective vertebrae intervertebral foramina
Where does the neural innervation of the upper limb come from?
The brachial plexus, found in the axilla
What nerves form the brachial plexus?
C5 -> T1
What nerves emerge from the brachial plexus?
Musculocutaneous, Axillary, Radial, Median, Ulnar
Where does the neural innervation of the lower limb come from?
The Lumbo-Sacral plexus, within psoas major on the posterior abdominal wall, and on the lateral wall of the pelvis
Where is the psoas major muscle?
It starts on the spine around T12/L1 ish and moves caudo-laterally towards the pelvis idk
What nerves are the lumbo-sacral plexus derived from?
the ventral rami of L1 to L5 and S1 to 4
Describe the arterial supply of the upper limb
Subclavian -> axillary -> brachial -> radial and ulnar -> Deep and superficial palmar arches
Describe the arterial supply of the lower limb
External iliac artery -> Deep and superficial femoral -> popliteal -> tibias posterior and anterior -> plantar arcade
Describe the venous drainage of the upper limb
Two main veins: cephalic and basilic
The cephalic vein is broadly lateral to the basilic vein, this is much clearer in the brachium. The median cubital vein joins these two and is found in the cubital region (big surprise)
In the hands the basilica and cephalic veins from the dorsal and palmar venous networks
Describe the venous drainage of the lower limb
The great saphenous vein runs along the medial side of the femoral region and the small saphenous vein runs along the anterior side of the leg
Into what vein may one put an IV line?
The cephalic vein
From where may one take a venous sample?
The median cubital vein
Where may superficial veins be found?
in superficial fascia
Connections of superficial veins with the deep veins are more significant in the lower limb than the upper limb
Describe process of venous drainage of the lower limb
Venous flow is from superficial to deep, via perforators
The muscle pump, arterial pulsation, negative intrathoracic pressure and valves in veins help venous return to the heart, against gravity.
Describe lymph drainage of the limbs
Lymph vessels follow the superficial or deep veins
Drain to the Axillary (upper limb) and Inguinal (lower limb) lymph nodes
Alongside what structures can the deep veins in the limbs be found?
Accompanying the associated arteries of the limbs
