27.01.25 - Introduction to the Limbs Flashcards
What happened to human limbs as a result of evolution?
- humans are bipedal ( use two feet)
- the upper limb has almost no locomotor function
- the upper limb has a great degree of freedom of movement
Describe the Upper limb
- Upper limb is an organ for grasping and manipulating
- Highly mobile joints
- Levers
- Enable the hand to be brought to any point in space and keep it steadily
Describe the Lower limb
- Supports the body weight
- Involved mainly in locomotion
- The bones are more robust
-Joints are more stable
Explain the development of the limbs
At the end of week 4, the limbs buds become visible on the ventrolateral body wall and extend ventrally. Contain cells from somites and lateral plate mesoderm
Somite- aggregation of mesoderm
Upper Limb bud opposite somites C5-T1
Lower Limb bud opposite somites L2- S2 (2 days after)
Apoptosis occurs to give individual digits
What are the three types of muscles?
Smooth, Cardiac and Skeletal
What is the origin of a muscle?
The origin is usually the proximal end of the muscle. It is the fixed attachment point of a muscle. It does not move during contraction.
What is the insertion of a muscle?
The insertion is usually the distal end of the muscle. It is the movable attachment point of a muscle. It moves during contraction.
What happens to the origin and insertion during contraction
When stimulate, a muscle contacts it pulls its insertion towards the origin. The muscle shortens and brings the two attachment points closer
Explain the term isometric contraction
Isometric contraction- The muscle generates tension, but its length does not change during contraction. No movement occurs at the joint. Used to stabilize joints or hold a position
Explain the term Isotonic contraction
Isotonic Contraction- The muscle generates tension and changes length during contraction, causing movement at the joint. Used in dynamic actions
Describe and name the types of Isotonic contraction
- Concentric: The muscle shortens while generating tension (e.g., lifting a weight).
- Eccentric: The muscle lengthens while generating tension due to an opposing force greater than the force the muscle generates (e.g., lowering a weight).
Define these terms:
Prime mover
Agonist
Synergist
Antagonist
Fixator
- Prime mover: Muscle(s) that play the primary role in moving a body part
- Agonist: Muscle(s) that acts directly to produce a desired movement
- Synergist: Muscle(s) 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: Muscle(s) which directly oppose a movement
- Fixator: Muscle(s) that provide the necessary support to assist in holding the rest of the body in place while the movement occurs
What is the superficial fascia and what does it contain
- Just beneath the skin
- Contains adipose tissue
- Superficial nerves and vessels
Describe Deep fascia
- Sometimes named e.g. brachial fascia
- Ensheaths muscles but continuous
- Facilitate contraction by transmitting the forces generated by muscles
- Barrier between muscles
- Compartments of muscles
- Passages for nerves and vessels
- Attachment for muscles (e.g. by forming interosseous membranes) (muscles can arise from deep fascia)
- Hold tendons in place by forming retinaculae for more efficient action of the muscle
- Send septae between the muscles to separate them into compartments. These septae form potential spaces to allow passage of nerves and blood vessels
- Potential spaces are also potential tracks for infection spread
- Compartment syndrome- treated by fascioctomy
- Potential spaces are also potential tracks for infection spread
Describe the deep fascia of the arm
- Medial and Lateral intramuscular septae are connective tissue bands that run from the deep fascia and separate the muscles of the arm into different compartments into the anterior and posterior sides of the arm.
- Anterior - Flexor compartment : Contains flexor muscle responsible for bending the elbow joint
- Posterior - Extensor compartment: Contains muscles that extend the elbow
Describe the deep fascia of the forearm
Antebrachial fascia surround and separates:
- Anterior - flexor compartment: for flexing the wrist, fingers and elbow
- Posterior - extensor/ supinator compartment; extending the wrist and fingers, supinating the forearm (rotating the palm upwards)
- And forms an interosseous membrane which is a connective tissue structure between the radius and the ulna
At the wrist it thickens to form a flexor retinaculum - the carpal tunnel
Describe the deep fascia of the thigh
- Fascia Lata - very thick - thicker than upper limb
- Thicker than the upper limb
- Thickened laterally to form illotibial tract
- Septae for three compartments
- Anterior- Extensor compartment: for extension of the knee and hip flexion
- Medial - Adductor compartment: Adducting the thigh (bringing the leg toward the midline) and assists flexion/extension of the hip
- Posterior - Flexor compartment: for flexion of the knee and hip extension
Describe the deep fascia of the Leg
- Crural fascia
- Fuses with tibia
- Forms interosseous membrane
- Septae form:
- Anterior-Extensor compartment: for dorsiflexion of the ankle (lifting the foot upward) and extension of the toes
- Lateral- Everters compartment: for eversion of the foot ( turning the sole outward) and plantarflexion of the ankle ( pointing toes downward)
- Posterior - Flexor and plantar flexor compartment
What happens to tHe dermatomes as the limbs grow
As the limbs grow out, they rotate dragging the dermatomes with them.
In the upper limb C7 and C8 extend distally
What is the initial position of the thumb, hallux (big toe), palm and sole in early development
Initially, 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 during development
- The upper limb rotates laterally from its in-utero position
- Thumb moves from superior to lateral
- Flexor muscle groups move to an anterior position
- Extensors move to a posterior position
Describe the rotation of the lower limb during development
- The lower limb rotates medially :
- Hallux moves from superior to medial
- Flexor muscle groups move from an anterior to a posterior position
- Extensors move to an anterior position
What are the main groups of lymph nodes in the upper limb
The axillary lymph nodes are located in the armpit area and are the main lymph nodes that drain the upper limb (arm, shoulder, and chest).
What is the main group of lymph nodes in the lower limb
The inguinal lymph nodes are located in the groin area and drain lymph from the lower limb (leg, foot, and lower abdomen).
What is the arterial supply of the upper limb
Subclavian artery
What is the arterial supply of the Lower limb
External iliac artery
What are deep veins
accompany arteries, usually as venae comitantes – taking the artery’s name
What are superficial veins?
Are closer to the skin, in the superficial fascia.
They are individually named, and are commonly accessed for venepuncture.
Explain the venous flow of the upper limb
Veins normally drain from superficial to deep via perforating veins and backflow is prevented by valves.
If the valves fail it causes distension
Describe the venous flow of the lower limb
- Venous flow is from superficial to deep via perforators. If blood is stagnant it causes a thrombus
- The muscle pump, arterial pulsation, negative intrathoracic pressure and valves in veins help venous return to the heart against gravity.
