001 Organisational patterns of limbs Flashcards
what are the 3 components of limbs
Stylopod, Zeugopod, Autopod
what is the stylopod component of limbs?
- 1 single bone
- most proximal bone in limb
- e.g. humerus, femur
what is the zeugopod component of limbs?
- 2 bones
- middle bone in limb
- e.g. radius/ulna, tibia/fibula
what is the autopod component of limbs?
- multiple bones
- most distal bones
- e.g. carpals/metacarpals/phalanges (wrist and fingers), tarsals/metatarsals/phalanges (ankle and toes)
what is anterior and posterior?
- anterior = front e.g. face
- posterior = back e.g. back
what is medial and lateral?
- medial = closer to middle/midline e.g. heart
- lateral = further from the middle/midline e.g elbow.
what is proximal and distal?
- proximal = closer to the trunk of body e.g. humerus
- distal = further away from trunk of body e.g. fingers
what is the coronal/frontal plane?
- divides front and back of body
what is the transverse/axial plane?
- divides top and bottom of body e.g. CT scan (horizontal)
what is sagittal plane?
- divides left and right of body e.g. through the midline
how does limb development start in embryos?
- protuberances of segments of the body wall (stick out)
what are the dermatomes of the upper limbs?
- C5 - T1
what are the dermatomes of the lower limbs
- L1 - S3
give an overview of how limbs form in embryos in terms of ectoderm and mesoderm
- ectoderm creating a pocket = skeletal muscle and nerve innervation
- inside filled with and covered by mesoderm = bones, tendons, vasculature, fascia and dermis
what are tetrapods?
- vertebrates with 4 digited limbs
- evolved from fish
- all tetrapods have a stylopod, zeugopod and an autopod
in fish where are the dorsal muscles and which direction does it move?
- above the central axis
- moves fins upwards
in fish where are the ventral muscles and which direction does it move?
- below the central axis
- moves the fins downwards
how is the limb organisation different in 4 legged mammals compared to fish
- the limbs bend ( rotated 90 degrees around the central axis)
- upper and lower limbs rotate in opposite directions
- limbs are under the body
- forearm pronates to point fingers forward as elbow is backwards
what is pronation?
- twisting of the muscles and central axis in the forearm so that the fingers are facing forward despite the elbow being rotated backwards
describe briefly week 5,6,7,8 in limb development in embryos
- week 5 = limbs bud from trunk similar to fish
- week 6 = limbs grow and ben, elbows and knees point laterally hands and feet face trunk
- week 7 = limbs rotate 90 degrees rotation around their central axis but in opposite directions ( elbows point causally, knees crainally)
- week 8 = limbs rotate 90 degrees latero-medially, bringing the limbs underneath the trunk
give an overview of the adult dorsal/ventral muscle group distribution
- dorsal muscles = back, shoulders, back of arms, glutes, front of thighs, front of calves, feet
- ventral muscles = torso, forearms, pelvis, back of legs
describe what segmental innervation development in embryos is
- dermomyotomes of the limbs start like the torso in clear horizontal strips
- during embryonic development the limbs twist and rotate to form the arms and legs
- so the dermomyotomes are no longer clear horizontal segments going down
what is a nerve plexus?
- a plexus mixes and redistributes fibers from spinal nerves to form peripheral nerves
- used so the same spinal nerve can innervate multiple areas
- nerve fibers from different spinal nerve levels traveling to the same area e.g. the hand are bundled together into peripheral nerves using nerve plexi
what is the upper limb nerve plexus called?
- brachial plexus
what is the lower limb nerve plexus called?
- lumbosacral plexus
how do you clinically test spinal nerves in limbs?
- use the areas on the limbs with minimal dermatome overlap and correspond the areas to the spinal cords and determine the nerve ability
e.g. little finger = C8, pointer finger = C7, thumb = C6, big toe = L4 …
what are the main arteries for the upper limbs?
- single subclavian arteries from the thoracic aorta
what are the main arteries for the lower limbs?
- abdominal aorta splits into the 2 common iliac arteries that branch into external iliac arteries that supplies most of the lower limbs
describe the pattern of lymphatics in the upper limbs
- distal limb contains deep and superficial lymphatic vessels
- major lymph node groups are found in the axilla ( group of lymph nodes in the armpit) towards which all the upper limb drains
describe the pattern of lymphatics in the lower limbs
- distal limb contains deep and superficial lymphatic vessels
- the major lymph node groups are the superficial and deep inguinal nodes which drain into the external iliac nodes
