Module 3 Unit 2 Flashcards

1
Q

What is the paraxial mesoderm? What are the series known as?

A

Forms a segmented series of aggregated tissue blocks on each side of the neural tube

somitomeres - Loosely packed in the head region
Somites - more densely packed from the occipital to caudal region

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2
Q

How many pairs of somites are there for each region?

A

42 - 44 pairs of somites:
4 occiput
8 cervical
12 thoracic
5 lumbar
5 sacrum
8-10 coccyx

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3
Q

What are the differentiated parts of somites?

A

Dermatomes, Myotomes, Sclerotome

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4
Q

What is a dermtome? How does it relate to a clinical diagnosis?

A

Area is the skin innervates by sensory fibers from a single spinal nerve root. Relays sensation from a particular region of the skin to the brain.

Clinically to diagnose the level of the spinal cord or nerve root damage.

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5
Q

What are myotomes? How are there important for diagnosing?

A

Groups of muscles innervates by the motor fibers of a single spinal nerve root.

Important for assessing motor function and diagnosing neuromuscular disease.

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6
Q

What are the sclerotome? How is it clinically relevant?

A

The regions of bone or skeletal structures innervated by single spinal nerve roots.

Relevant in understanding patterns of referred pain in conditions affecting the skeletal system.
* Cells of sclerotome are mesenchymal that differentiate to become: chondroblasts, osteoblasts, fibroblasts

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7
Q

What does the paraxial mesoderm contribute to?

A

It contributes to the bones of the face and skull,and vertebrae and ribs.

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8
Q

What does the neural crest cells (NCC) contribute to?

A

It contributes to the bones of the face and skull.

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9
Q

What does the lateral plate mesoderm contribute to? What structures are the cells in the parietal mesoderm differentiated into?

A

It contributes to the viscerocranium in the pharyngeal arches. It is differentiated into parts of the appendicular skeleton such as, sternum, bones of the pelvic and shoulder girdles, and limb bones.

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10
Q

What are the two distinct processes involved in the formation of bones during embryonic and fetal development? What do they involve?

A

Intramembranous ossification - involves direct bone formation from mesenchymal tissue.
Endochondral ossification - the replacement of a cartilaginous template with bone tissue.

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11
Q

What is the intramembranous ossification process?

A

Mesenchymal stem cells —> Differentiate into osteoblasts —> Osteoblasts come together to form an ossification center —> Osteblasts gradually arrange in a circle around ossification center —> Osteoblasts secrete osteoid (unmineralized bone) —> Osteoid calcifies and hardens to form bone

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12
Q

What are the bone directly differentiated to in the intramembranous ossification process?

A

Flat bones of the skull (parietal, frontal, occipital etc.), clavicle

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13
Q

What does the endochondral ossification give rise to?

A

Mesenchyme (hyaline cartilage) —> Cartilage (scaffold) —> Primary ossification center formed in the center, blood vessels starts to enter (Osteoblasts and proliferating chondrocytes) —> Secondary ossification center formed on the two ends of the long bone

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14
Q

What does the brachial (pharyngeal) apparatus shape into?

A

The head and neck anatomy in vertebrate embryos

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15
Q

What does the pharyngeal cross-section consist of?

A

Mesenchymal core derived from mesoderm and neural crest cells, and each is lined internally by endodermis and externally by ectoderm.

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16
Q

What does the first pharyngeal arch (Meckel’s cartilage) give rise to?

A

Gives rise to the maxilla, mandible, and muscles of mastication innervated by CN 5

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17
Q

What does the secondary arch give rise to?

A

Contribute to the formation of the hyoid bone and muscles of facial expression innervated by CN 7

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18
Q

What does the third and fourth arches give rise to?

A

thyroid gland
Thymus
Parathyroid glands
Components of the middle ear and neck

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19
Q

What does arch/pouch 1 consist of?

A

Muscles of Mastication
Meckel’s Cartilage
Maxilla
Meatus
Middle ear
Mastoid air cells
Maxiallary artery
Mylohyoid
trigeMinal nerve (CN 3)

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20
Q

What does arch/pouch 2 consist of?

A

Staples
Styloid
Stylohyoid
Stapedius
Smiling (fascia nerve)
Stapedial artery

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21
Q

What does arch/pouch 3 consist of?

A

StyloPHARYNGEUS, glossoPHARYNGEAL nerve, Parathyroid glands, internal Carotid (Problem if severed), Common Carotid (Problems of severed)

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22
Q

What does arch/pouch 4 + 6 consist of?

A

everything from Vagus
4 - superior laryngeal
6 - Recurrent laryngeal

Arytenoids, Cricoid, Corniculate, Thyroid, Superior Parathyroid, Ultimobrachial body, Parafollicular Cells

Pulmonary arteries + ductus arteriosus (left)

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23
Q

What is the Neurocranium?

A

Forms a protective case around the brain

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24
Q

What is the Viscerocranium?

A

Forms the skeleton of the face

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25
Q

What is the neurocranium derived from?

A

Membranous and Cartilaginous/ Chondrocranium

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26
Q

How is the Viscerocranium formed?

A

From the first 2 pharyngeal arches

1st pharyngeal arch:
Maxillary process - extends beneath the eye - Maxilla, zygomatic and part of temporal bone

Mandibular process - Meckel cartilage - intramembranous ossification forms the mandible

Meckel cartilage along with the 2nd arch makes malleus and incus

2nd pharyngeal arch:
Stapes (3rd ossicle of mid ear)
Styloid process
Stylohyoid ligament

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27
Q

What are the fontanelles of the newborn skull? Where are they located? What order do they close in?

A
  1. Posterior fontanelle (back/ top of the head)- closes early @ 1 to 2 months
  2. Sphenoidal fontanelle (side of the head) - closes @ 6 months
  3. Mastoid fontanelle (back, bottom, side of the head) - closes in after sphenoidal and before anterior
  4. Anterior fontanelle (front/ top of head) - closes @ 18 months of age
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28
Q

What happens if the sagittal cranial sutures closes to fast?

A

Scaphocephaly - skull is long narrow shape with dominant frontal and occipital regions

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29
Q

What happens if the conornal cranial sutures closes to fast?

A

Brachycephaly - tall shape of skull

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30
Q

What happens if one of the coronal cranial sutures closes to fast?

A

Plagiocephaly

31
Q

What is anencephaly?

A

Cranial neuropore open fails to close causing the skull to not form and brain tissue is exposed to amniotic fluid

32
Q

What is microcephaly? Why does it happen?

A

Small head doe to the brain failing to grow to its normal size.

Alcohol consumption during gestation

33
Q

What are the 3 directions for each intersegmental sclerotome? What does it surround? What does it form?

A

Medial - Surrounds the notocord/ forms the membranous vertebral
Dorsal - surrounds the neural tube/ forms the posterior arch
Anterolateral - into space between myotomes/ forms the costal processes

34
Q

Which half of the sclerotome is dense and loose?

A

Top half of the sclerotome is loose cranial half

Bottom half of the sclerotome is dense caudal half

35
Q

After resegmentation, where are the sclerotome?

A

The dense caudal end above migrates and merges with the loose cranial end below.

36
Q

What is the result of the resegmentation?

A
  • The myotomes bridge the intervertebral discs which gives them the capacity to move the spine.
  • The intersegmental arteries, that were initially present between the sclerotome, now pass over and into the vertebral bodies.
  • The spinal nerves lie near the intervertebral discs. Nerves exit the vertebral column through the intervertebral foramen.
37
Q

What are the 4 chondrification centers that appear at the 7th week?

A

2 for the vertebral body
2 for the posterior arch

38
Q

What is it called if the vertebral body and posterior arch do not fuse until ossification occurs?

A

Synchondrosis

39
Q

When does ossification begin?

A

7-9 weeks

40
Q

When do the primary ossification and the union of vertebral arch and body occur?

A

3 years for cervical spine
6 years for the lumbar spine

41
Q

When does the primary ossification and the union of vertebral arch and body occur in the cervical and lumbar spine?

A

3 years for cervical spine
6 years for the lumbar spine

42
Q

When does the secondary ossification occur?

A

Around 7-15 years

43
Q

When does the skeletal immaturity occur around?

A

20 years of age

44
Q

What are the 9 secondary ossification centers?

A

1 for the development of epiphyseal plate on cranial surface of segment
1 for the development of epiphyseal plate on caudal surface of segment
2 for the superior zygapophyseal processes
2 for the inferior zygapophyseal processes
1 spinous process

45
Q

When do the end plates ossified?

A

15-17 years of age

46
Q

How many primary ossification centers in the prenatal period? How many does each vertebra have?

A

3 primary ossification centers
3 bony parts connected by cartilage

47
Q

When does the vertebral arches fuse halves to the vertebral body? When does the second ossification center seen?

A

Between 3-6 years
Puberty

48
Q

How do we apply embryology in the real world?

A

The process of formation and rearrangement of segmental sclerotome into vertebrae is complicated.

49
Q

When does neural tube defects happen? How does these defects occur?

A

4th week of embryologic development
Caused by nutritional, environmental, or drugs

50
Q

What does deflects in formation and segmentation results in? List examples

A

Absence of a structural element, causing an alternation in normal growth patterns.

Examples: Hemivertebra (formation) and block vertebra (segmentation)

51
Q

What does deflects in formation and segmentation results in? List examples

A

Absence of a structural element, causing an alternation in normal growth patterns.

Examples: Hemivertebra (formation) and block vertebra (segmentation)

52
Q

What are some congenital anomalies seen regularly in clinical practice?

A

Hemivertebrae, Block vertebrae, spina bifida occulta, butterfly vertebrae

53
Q

When do limb buds appear and grow out from the ventrolateral body wall?

A

4th week

54
Q

What do limb buds consist of?

A

A mesenchymal core that forms the bones and the connective tissue of the limb and a layer of ectoderm

55
Q

What does the terminal end of the limb bud do?

A

The ectoderm thickens and forms the apical ectodermal ridge (AER)

56
Q

What are 3 components are formed in the proximodistal manner?

A

1) Stylopod (humerus and femur)
2) Zeugopod (radius/ ulna and tibia ibula)
3) Autopod (carpals, metacarpals, tarsals, metatarsals)

57
Q

What flattens to form hand or foot plates?

A

Autopods

58
Q

What direction does limb rotation occur?

A

Upper and lower limbs rotate in opposite direction.
Adult elbow pointing posteriorly and adult knee pointing anteriorly.

59
Q

When does limb rotation occur?

A

6-8 weeks

60
Q

What do the muscular system consist of?

A

Skeletal, Cardiac, Smooth

61
Q

What mesoderm is the skeletal muscle in?

A

Paraxial mesoderm

62
Q

What mesoderm is the cardiac muscle in?

A

Visceral/ splanchnic mesoderm

63
Q

What derms layers is the smooth muscle in?

A

Visceral/ splanchnic mesoderm
Ectoderm
Neural crest cells

64
Q

How is the head muscularture derived from?

A

The first 7 somitomeres (paraxial)

65
Q

What is derived from somites?

A

Muscles of axial skeleton, body wall, and limbs

66
Q

What is derived from somites?

A

Muscles of axial skeleton, body wall, and limbs

67
Q

What do myoblasts fuse to? What do they produce?

A

They fuse to form a single, multinucleated skeletal muscle cell. They rapidly start producing actin and myosin of fibrils.

68
Q

How is the cardiac muscle developed? What does it surround?

A

Cardiac muscles develops from visceral/ splanchnic lateral plate mesoderm. It is surrounded by the endothelial heart tube.

69
Q

How does the heart adhere to one another?

A

Intercalated discs

70
Q

What do the myotomal cells differentiate into?

A
  1. Dorsomedial muscle cells = Epimere
  2. Ventrolateral muscle cells = Hypomere
71
Q

What are the epimere layers migrate into?

A

Erector Spinae Group:
1. Ilicostalis
2. Longissimus
3. Spinalis
4. Deep spinal intrinsic muscles

72
Q

What are the hypomere layers migrate into?

A
  1. Sub vertebral muscles
  2. 4 layered lateral body wall muscles
    - Suprcostal or outmost muscles
    - External muscles
    - Middle muscles
    - Innermost muscles
  3. Ventral muscles
73
Q

What is prune belly syndrome?

A

Partial or complete absence of abdominal musculature

74
Q

What is the Poland sequence?

A

The pectoral is minor and part of the pectoralis major muscles are missing on the patient’s left side.