Upper Limb Organization- Diogo Flashcards
The joint between the sternum (axial skeleton) and clavicle (shoulder girdle)
sterno-clavicular joint
The joint between clavicle and scapula
acromio-clavicular joint
acromion is the bony process of the scapula
Gleno-Humeral joint is what?
the joint between the scapula and the humerus
Glenoid cavity articulates with the head of the humerus. The glenoid cavity or glenoid fossa of scapula is a part of the shoulder.
joint between the humerus and radius and ulna
elbow joint
radius is in the direction of thumb (lateral)
ulna is in the direction of the pinkey (more medial)
joint between radius and carpals (hand)
wrist or radio-carpal joint
joint between carpals and metacarpals
carpo-metacarpal joint
What is the anatomical position?
hand is outward with thumbs facing outward or laterally
What is the reference point in humans for determining what is axial or proximal?
the heart
What is the direction of the fibula and tibia?
fibula is lateral and tibia is medial
Why is the ventral rami an imperfection? What price do we have to pay for this imperfection?
The anterior or ventral muscles are innervated by the ventral rami. The posterior or dorsal muscles are innervated by the dorsal rami.
However, all muscles of the limbs, including those that are posterior are innervated by the ventral rami. This is an imperfection.
Imperfections are usually where diseases occur. One example of a ventral rami is the axillary nerve (anterior) that goes posteriorly to the axial side. It is very prone to damage and this is how we get disease. This is the price we pay for these imperfections.
Ventral rami is used to talk about anterior nerves.
All the muscles come from what embryological structure and where do they migrate?
myotome
they migrate to form the skeletal muscle
Myotomes are segmental in the fetus at what time?
6 weeks
At 8 weeks the myotomes diffuse and you lose the segmentation.
The distal regions are more similar in terms of bone and muscles as opposed to the proximal regions. True or false?
True!!
The shoulder has nothing to do with the pelvis in the proximal region. In terms of muscles and bones, the distal regions are more similar.
What are always different between the upper and lower limbs?
the nerves
the arteries
The upper and lower limbs converge to have similar shape, as they use similar genes, but only in the distal parts are they more similar in terms of bone and muscle than the proximal parts. All the parts of the limb are different in terms of nerves and arteries.
What forms the distal epithelium on the day 30 of forelimb development in humans?
apical ectodermal ridge (AER)
Which has more sonic hedgehog secretion, radius or ulna?
ulna
What is between the radius and ulna on day 30 of forelimb development?
active polarizing zone where there are sonic hedgehog secretions
polarizing zone is to the ulna
Tendons and muscles are together during embryogenesis. True or false?
FAAALLLSEEEE
Tendons and muscles are NOT together during embryogenesis. They come together later on.
What directs the proximo-distal polarity?
apical ectoderm ridge
What cells releases signals (what signals) to develop the latero-medial OR radio-ulnar OR cranio-caudal axis?
Zone of polarizing activity cells
at the ulnar/medial side of hand
release sonic hedgehog signals
That’s why the thumb has very low concentrations of sonic hedgehog.
What is the factor being changed for a mirror hand image?
the zone of polarizing activity
there are two on the radial-lateral and ulna-medial side
instead of one on the ulna-medial side (normal)
Zone of polarizing activity mediates _____________polarity and apical ectoderm ridge mediates _______________polarity.
latero-medial
proximo-distal
What DEFINES the proximal/distal distance?
AER and Hox genes
Forelimb (upperlimb) and hindlimb (lowerlimb) are regulated by which genes respectively?
upper limb is regulated by Tbx5 transcription factor
lower limb is regulated by TBx4, and Pitx1
Without this, your fingers would be webbed AKA syndactyly.
apoptosis
The discreptancy between the human standard anatomical position and the “true” anatomical position is with the LOWER LIMB rotated almost 180 degrees laterally. What is the position of the thumb in the anatomical position? What is the position of the hallux in the anatomical position? What is both of their positions in the “true” anatomical position?
-human standard anatomical position
thumb: lateral
big toe : medial
-“true” anatomical position
thumb: lateral
hallux (big toe): lateral
The brachial artery (branch of the brachial plexus) supplies the blood for what?
the muscles of the upper limb on the posterior side
Tool use is NOT exclusive of humans due to what evolutionary implication?
bipedalism opposition
this movement is exceptionally refined in the human species where the more mobile thumb is exchanged for the other digits moving badly
What grips are primates/animals and humans able to perform due to bipedalism opposition?
primates/animals mainly use power grip
humans are the only ones who can do precision grip
The specialization of voice leads to what trade-off/price we have to pay?
humans are the most susceptible to choking because
there’s a big space between the tongue and larynx and food could get into the larynx instead of the oesophagus
Other animals have a small space so there’s hardly any choking for them
An abnormal configuration is considered what?
a birth defect
1-2% of this are found in the NORMAL human population.
human variation
These are found in more than 3% of the normal human population. Palmaris longus is an example.
polymorphisms
Limb defections are present in the normal human population. True or false?
FALLLSEE
limb defects are birth defects which are NOT present in the normal human population
There is no normal in a population. There’s a continuum. Normal is just a simplification.
He’s trying to explain that we ought to understand that “normal” has just been our way of simplifying things.
What is the sensitive period of limb development?
4th to 8th week
This limb malformation describes the absence of one or more complete limbs.
Amelia, ectromelia
This limb malformation describes short, ill-formed upper or lower limbs–named for their resemblance to the flippers of a seal.
phocomelia
What is ectrodactyly? Polydactyly? Syndactyly? Adactyly?
ectrodactyly: complete absence of one or more digits
polydactyly: presence of extra digits or parts of digits
syndactyly: fusion of digits
adactyly: absence of all the digits on a limb
We can predict the number of surgeries a patient with polydactyly and syndactyly can have. True or false?
TRUE!!!
- no thumb: muscles that go to thumb are still there but will go to digit 2
- 2 thumbs: muscles that go to the lateral thumb will now go to the MOST lateral digit (in anatomical position)
Thalidomide teratogen taken by pregnant women to alleviate morning sickness caused what type of limb malformation?
amelia, phocomelia
When does limb formation occur for the human embryo?
This is also known as the phylotypic stage.
Week 6
During the phylotypic stage around Week 6 of embryogenesis, genes like Tbx form the limbs, head, gut, etc.. If you mess up the phylotypic stage then you have a lot of different defects. That’s why 1-8 weeks is a very sensitive stage!!
lower limbs are formed after the phylotypic stage
Limb anomalies are usually due to teratogenesis, however some limb anomalies are inherited. What is an example?
Lobster claw hand or foot is inherited as autosomal dominant trait. It is inherited genetically.
Achondroplasia: a form of short-limbed dwarfism
This is a hereditary condition in which the growth of long bones by ossification of cartilage is retarded, resulting in very short limbs relative to the trunk, and sometimes a face that is small in relation to the (normal-sized) skull.
Achondroplasia which affects the limbs (lower and sometimes both lower and upper limb).
Motor innervation of all limb muscles is by ___________which are derived from the neural tube. Sensory innervation receives contribution from neural crest cells.
ventral rami
Why are there different models of extensor digitorum communis tendons (EDC tendons)?
It allows for more flexibility. You can still have some functionality with less or more than 5 digits.
How is the brachial plexus of the ventral rami an imperfection?
The brachial plexus of the ventral rami innervates the upper limb muscles. Brachial plexus are anterior to the clavicle and shoulder. The shoulder muscles are on the posterior side. So you have brachial plexus nerves coming from the anterior side to innervate shoulders on the posterior side.
You pay the price for the imperfections (nerves are more susceptible to damage).
The pectoral nerves on the anterior side innervate the pectoralis muscles on the anterior side so these are less prone to damage.
