Dermatomes, Myotomes

Question 1

What is skeletal maturity determined by?

Answer 1

Genetic , socioeconomic and disease states ( hypothyroidism and malnutrition will cause slower bone growth than normal)

Question 2

What happens to the red(x tissue) and yellow marrow as the person ages? What types of stem cells are present in bone marrow.

Answer 2

X= myeloid More red bone marrow is converted into yellow bone marrow within the medulla of long and flat bones Stem cells : haemopoietic wc give rise to WBC and RBC and platelets + mesenchymal cells wc give rise to cartilage (chondrocytes) bone (osteocytes) and muscle (myocytes)

Question 3

How is bone marrow transplant done ? Who is is done on?

Answer 3

People with leukaemia ( bone marrow malignancy) so harvest nonmalignancy bone marrow cells from own patient or another patient, destroy that patients own marrow using chemo and radiation and then infuse new cells

Question 4

Why do fractures usually occur

Answer 4

Too much force /weight Osteoporosis (weaker bones)

Question 5

What’s segmentation

Answer 5

The patterning and segregation of groups of cells with different features,generating definable properties for such groups and organising them into tissues.

Question 6

What controls segmentation

Answer 6

Hox genes ; they determine the body that forms from a vertebrae/ the limb that forms from a limb bud / segmented identity but not the actual segments themselves

Question 7

What direction is segmentation carried

Answer 7

Cranio -caudal

Question 8

Mutation of the hox genes is

Answer 8

Homeotic mutation ; it causes abnormal pattering and differentiation pattern, producing integrated structures in usual locations e.g producing of a 6th lumbar vertebrae in he place of the 1st sacral vertebra

Question 9

6 fingers why?

Answer 9

Mutation of the hox genes governing digit development, resulting in the formation of extra digits

Question 10

X mutation of the cervical spine

Answer 10

X = homeotic mutation Result in the formation of an additional cervical spine which compresses arteries and nerves causing a condition known as thoracic outlet syndrome

Question 11

How would you describe the development as the top and bottom limbs as

Answer 11

Serially homologous

Question 12

Describe the embryology of the limb buds

Answer 12

• They first appear as small projections off the lateral body wall ding the fourth week of development
• consist of mass of mesenchyme covered by a layer of ectoderm; at the tip of the bud the ectoderm always cells divide to form apical ectoderm always ridge
• development of limb buds of upper body comes before that of the lower body by a few days
• limbs elongate via a process of proliferation of mesenchyme

Question 13

describe what happens in terms of embrology of the limbs

Answer 13

1. at first whole limb is cartilaginous
2. ossification of the long bones beings
3. at 12th week endocondral ossificatin begins
4. as bones are forming myoblasts aggregate and develop a large muscle mass in each limb bud. this msucle seperates into dorsal (extensors) and ventral (flexors)
5. since at first the flexors are ventral and extensors are dorsal the pre-axial is cranial and post-axial border caudal
6. limb rotation then takes place, where the upper limbd rotate 90 degrees externally and 90 degrees internally

Question 14

taking into account the rotations of the limbs where is the extensor compartment of the leg and why

Answer 14

anterior because the leg has rotated 90 degrees internally

Question 15

what map do we use and what map has significance for marking this limb rotation

Answer 15

• Foerster dermatome map
• keegan and garret dermatome map

Question 16

whats the segmentation pattern of the neural system called?

Answer 16

neural level = neural segment

Question 17

how is the neural tube formed and what happens after

Answer 17

1. day 18 embryo under the influence of notochord, te neural tube starts to invaginate to form the neural groove.
2. gradually the nerual folds appraoch each other and in the midline they fuse, forming a neural tube
3. by day 24 thers a cephalic(head) and caudal (taik) ends of the neural tube
4. but its day 20 that somites begin , first in the occipital region . they appear ina craniocaudual arrangment f 3 pairs per say but some disappear so that day 30 (week 5)theres only 34-35 pairs of somites left
5. as soon as somites form they begin to differentiate

Question 18

describe the differntiation process of somites

Answer 18

• each somite differentaites into the :
  
  1. schlerotome which is ventral and gives rise to vertebrae and ribs
  2. dermatomyotome which is dorsal and gives rise to skin via dermatome and muscle tissue via myotome
  3. these dermatomyotomes develop in association with a specific neural levels of the spinal cord and take their nerve supply with them from the nerual tube as a spinal (segmental) nerve

Question 19

draw and label the x dermatome map

Answer 19

foerster map

T4/5 = nipples

T10 = umbilicus

L1 = groin

Question 20

whats special about the endoneurium

Answer 20

it has properites analgous with the blood brain-barrier so it prevents certain molecules frm crossing from the blood into the endoneurial fluid

so this endoneurial fluid is therefore analgous to CSF in the CNS , during nerve irritation the endoneurial fluid increases , this oedema in the nerve can be detected with MRI

Question 21

axonds are surrounded by what? and what is theri arrangment

Answer 21

axons are surrounded by endoneural fluid and are bundled into fasciles, and each fascile is wrapped in CT called perineurim , and that itseft once grouped is surroneded by epineurium and within this epineurium is vasa nervorum which the blood suuply to the nerve

Question 22

what is each vertabrae derieved from

Answer 22

2 adjascent somites

Question 23

label this

Answer 23

Question 24

where does the spinal cord start and end?

Answer 24

starts at the inferior margin of medilla oblongata of brain stem and ends at the conus medullaris at L2, but due to differential growht between the vertebral canal and spinal cord, the spinal cord is shorter than the vertebral canal

Question 25

where is the conus medullaris

Answer 25

L2

Question 26

where does the cauda equina start

Answer 26

near the 1st lumbar vertebrae

T12/L1

Question 27

label this

whichroot is sensory and which is motor

Answer 27

dorsal = sensory

ventral = motor

Question 28

describe the differences between pre and post ganglionic neurones of sym and parasym

Answer 28

sym = short pre long post / pregangionic neurone cell body found in lateral horm of T1 - L2

para = long pre shor tpost (cell body is sometimes within the muscel itself) pregang. neruone cell body S2-s4 cord segment and