Module 3: Unit 1/2 Flashcards
What is the length of the Embryonic Period?
3-8 weeks
What are the three germ layers and in what layers are they?
Ectoderm (outer later)
Mesodderm (Middle layer)
Endoderm (Deepest layer)
The skeleton is split into what two divisions?
Axial skeleton
And
Appendicular skeleton
Define Somitomeres. What germ layer do they abide?
Loosely packed in the head region — Bones of skull
Paraxial mesoderm
Define somites. How many pairs of somites are there in paraxial mesoderm?
42-44 pairs of somites:
4 occipital
8 cervical
12 thoracic
5 lumbar
5 sacrum
8-10 coccyx
What are the three somite differentiations? Briefly describe each.
Dermatomes - These are areas of skin innervates by sensory fibers from a single spinal nerve root. Each spinal nerve relays sensation from a particular region of skin to the brain. Dermatome maps are used clinically to diagnose the level os spinal cord or nerve root damage.
Myotomes - Thesse are groups of muscles innervates by the motor fibers of a single spinal nerve root. Myotomes are important for assessing motor function and diagnosing neuromuscular diseases.
Sclerotome - These are regions of bone or skeletal structures innervates by a single spinal nerve root. Sclerotomes are used less frequently in clinical practice but are relevant in understanding patterns of referred pain in conditions affecting the skeletal system.
Cells of sclerotome are mesenchymal that differentiate to become what?
Chondroblasts
Osteoblasts
Fibroblasts
*review summary slide #10 on MOD 3 UNIT 2 for mesodermal origin gas of most osseous structures
What are the 2 main types of ossification?
Intramenbranous ossificication
Endochondral ossification
Describe endochondral ossification.
Involves the replacement of a cartilaginous template with bone tissue
Describe intramembranous ossification.
Involves direct bone formation from mesenchymal tissue
Name the steps of intramembranous ossification, and give examples of the bones they form.
- Mesenchymal stem cells
- Differentiate into osteoblasts
- Osteoblasts come together to form an ossification Center
- Osteoblasts gradually arrange in a circle around the ossification Center
- Osteoblasts secrete esteoid (unmineralized bone)
- O steroid calcifies and hardens to form bone.
*Picture on slide 14.
Formation of flat bones of the skull (parietal, frontal, occipital, etc.) clavicle
Name the steps of endochondral ossification, and give examples of the bones formed.
- Mesenchymal stem cells come together to form cartilage.
- at 8 weeks (embryo has cartilage skeleton)
- Primary ossification Center formed in the Center, blood vessels starting to enter.
- Secondary ossification Center formed on the two ends of the long bone
*Slide 16 for reference
Ex: bones of the limbs and the base of the skull
What does the Branchial (Pharyngeal) apparatus do?
Shapes the head and neck anatomy in vertebrate embryos.
REVIEW Branchial apparatus, pouches, and groupings on slides 19 and 20
What two parts does the skull consist of? What are the two ossification processes of the neurocrainuim?
Neurocranium and Viscerocranium (forms the skeleton of the face)
- The neurocranium (which forms a protective cause around the brain)
*Derived from a mixed population of cells, neural crest cells, and parochial mesoderm via both methods of bone formation.
1st method of bone formation: Membranous —> intramembranous ossification (Flat skull bones, EX: frontal, parietal)
2nd method of bone formation: Cartilaginous/Chondrocranium —> Endochondral ossification, (basal skull bones, EX: Sphenoud ethmoid, etc)
The viscerocranium (forms the skeleton of the face) is formed mainly from the first two pharyngeal arches. Name name these arches and the division of formation with these arches.
1st pharyngeal arch: maxillary process - extends beneath the eye - MAXILLA, ZYGOMATIC and part of the TEMPORAL BONE.
- mandibular process - MECKEL CARTILAGE- intramembranous ossification format the MANDIBLE
2nd pharyngeal arch: STAPES (3rd ossicle of mid.ear) STYLOID PROCESS, STYLOHYOID LIGAMENT
*look at reference picture on slide 28 unit 2
How many arches (keys to cranial facial development) are there in a 4 week old developing embryos?
There are five well developed arches numbered one through six because the fifth is vestigial (non-functional)
OBJECTIVE:
Understand the origin and development of the axial skeleton, appendicular skeleton, and muscles.
*COME BACK AND NOTE
OBJECTIVE:
Understand the embryonic origins of the skeletal system
*COME BACK
OBJECTIVE: Understand the two types of ossification processes.
Come back
OBJECTIVE: Understand the Axial Skeleton
— Development of the head and neck, parts of the skull
— Neurocranium, Viscerocranium
— Formation of the vertebral column, ribs and sternum
Come back
OBJECTIVE: Understand the appendicular skeleton
— Development of limbs
Come back
What are fontenelles and what are the four types of fontanelles?
*locations on slide 31 unit 2
IN ORDER OF CLOSER
- Posterior fontanelle - closes early @ 1 and 2 months of age
- Sphenoidal fantanelle - closes @ 6 months
- Mastoid fontanelle - closes after sphenoidal but before Anterior fontanelle
- Anterior fontanelle - closes @ 18 months of age
What are the developmental anomalies (abnormalities) of the skull? Name and briefly describe.
Craniosynostosis: early closure of cranial sutures
— Scaphocephaly caused by early closure of the sagittal suture
— Brachycephyaly cause by early closure of coronal sutures - tall shape of skull
— Plagiocephaly results from premature closure of the coronal suture on one side of the skull
Abnormalities:
Anencephaly - cranial neuropore open fails to close. The skull never forms and the brain tissue is exposed to amniotic fluid, thus tissue degenerates.
Microcephaly - A small head due to the brain failed to grow to its normal size.
Vertebrae are formed form the ___________ of the somites which are derived from paraxial mesoderm.
Sclerotome,
These cells migrate around the neural tube and notochord to merge with sclerotome cells of the state on the other side of the neural tube (forming the primitive membranous vertebrae)
Review Diagram on Slide 38 unit 2
Growth of each intersegmental sclerotome occurs in which 3 directions?
Medial- surrounds the notochord, forms membranous vertebral body
Dorsally - surrounds the neural tube, forms the posterior arch
Anterolaterally - into space between Myotomes, forms the costal processes (ribs and TP’s)
What is the segmentation/re-segmentation process?
Each vertebra is formed from the combination of the caudal half of one somite and the cranial half of its subjacent somite.
*diagram and further explain on slides 40-45
What happens as a result of resegmentation?
The Myotomes bridge the intervertebral discs - giving them the capacity to move the spine
The intersegmental arteries, that mere initially present between the sclerotomes, now pass over and into the vertebral bodies.
The spinal nerves lie near the intervertebral discs. Nerves exit that vertebral column through the intervertebral foramen.
*Diagram 43-45 for reference
What three directions do the growth of each intersegmental sclerotome occurs in?
Medial - surrounds the nontochord, forms membranous vertebral body
Dorsally - surrounds the neural tube, forms the posterior arch
Anterolarterally - into space between Myotomes, forms the costal processes (ribs and TP’s)
What 4 chondrification centers appear a the 7th week?
2 for the vertebral body (left and right) - enlarge and unite at the center
2 for the posterior arch (left and right) - Unite posteriorly at approximately 3 months, enclose the spinal cord
True or false: the vertebral body and posterior arch do not fuse until ossification occurs
True
This is called synchondrosis
C1 is embryologically formed of three primary ossification centers. What are these centers?
The anterior arch and two posterior neural arches.
GENERAL Questions of cartilaginous vertebrae.
*replacing cartilage with bone…
At what weeks does ossification (mineralization) begin?
What are the 3 primary ossification centers?
At what region does ossification begin?
7-9 weeks
1 for the VB
1 for each left and right portion of the posterior arch
Thoracolumbar region
At what years of age are the primary ossification and unions of vertebral arch and body is complete at ?
3 years for cervical spine
6 years for the lumbar spine
Secondary centers appear around 7-15 years. Skeletal immaturity occurs around 20 years of age.
How many secondary ossification centers are there?
9 secondary ossification centers
At what year of age do the endplates (superior and inferior) fuse.
20 years of age
Two primary curves of the spine are established initially by?
The thoracic and sacral curvatures formed in utero and present at birth
The two secondary curves are established later and are?
The cervical curvature, and the lumbar curvature
SUMMARY CARD: Vertebral ossification
Prenatal period: 3 primary ossification centers. At birth, each vertebra has 3 bony parts connected by cartilage
Postnatal period: Vertebral arch halves fuse to the vertebral body between 3-6 years.— Puberty: 9 secondary ossification centers are seen which unite with the rest of the vertebra at “skeletal maturity” around 20 years of age.
Explain what spina bifida is and how it forms?
Involves Neural Tube Defects: The neural tube does not completely close during the fourth week of embryological development, may be caused by nutritional factors, environmental factors or drugs.
*Due to the failure of fusion of laminae to form the SP (very common and usually asymptomatic)
Explain defects in formation and segmentation. Give an example.
- Arise as a result of an absence of a structural element, causing an alteration in normal growth patterns.
EX: Hemivertebra (formation) and clock vertebra (segmentation)
What are block vertebrae?
What are butterfly vertebrae?
-Block vertebrae are segmentation problems
-Butterfly vertebrae aer caused by failure of fusion of the 2 vertebral body chondrification centers (due to notochord remnant)
Look over review slide and quiz slide on 70-71 of unit 2
At what week do the limb buds appear and grow out from the ventrolateral body wall? What do the limb buds consist of?
@ the end of the 4th week
-Consist of a mesenchymal core that format the bone and the connective tissue of the limb
-Consists of a layer of ectoderm - external covering
At the terminal end of the limb bud, the ectoderm thickens and forms the…?
Apical Ectodermal Ridge (AER)
Positionally development happens in what manner?
Proximodistal manner
- Starts proximodistal, gradually progresses towards the distal end
Following the formation of the AER. What 3 components are formed from this?
Stylopod - humerus and femur
Zeugopod - radius/ulna and tibia/fibula
Autopod - carpals, metacarpals, tarsals, metatarsals
*Autopod flattens to form the hand or foot plates, these plates are separated from the zeugopod by a circular constriction
what happens with limb rotation during development?
To attain an adult anatomical position, the upper and lower lobs rotate in opposite directions and to different degrees, resulting in the adult elbow pointing posterior lay and the adult knee pointing anteriorly.
what happens with limb rotation during development?
To attain an adult anatomical position, the upper and lower lobs rotate in opposite directions and to different degrees, resulting in the adult elbow pointing posterior lay and the adult knee pointing anteriorly.
What consists of the Autopod component of developement?
Carpals, metacarpals, tarsals, and metatarsals
- Fingers and toes are formed due to cell death (apoptosis) in hand and foot plates, —> separates the plates into five parts.
Diagram slide 81*
When does limb development begin?
At the end of the fourth week
Watch Video of limb development for reference. Unit 3 section 4. “Lang an video of limb development”
What direction and degrees do the upper and lower limbs rotate?
The upper limbs rotate 90 degrees laterally
The lower limbs rotate 90 degrees medially
Except for some smooth muscle tissue, the muscular system develops from what layer?
Mesodermal germ layer
The muscular system consists of what muscle groups?
Skeletal muscle —> derived from parochial mesoderm (myotome of somate)
Cardiac muscle —> derived from visceral/splanchnic (lateral plate) mesoderm
Smooth muscle —> differentiates from diverse germ tissues
What aspects differentiate smooth muscle from germ tissues?
Visceral/ splanchnic mesoderm (for muscles surrounding the gut and its derivatives, muscles of aorta, large arteries)
Ectoderm (for muscles of the memory gland, sweat gland muscles, pupil dilator muscles, and sphincters)
Neural crest cells (muscles of aorta, large arteries, coronary arteries)
The head musculature is derived from how many somitomeres (paraxial)?
The first 7,
Skeletal muscle of the axial Kelton, body wall, and limbs is derived from he somites
Within skeletal muscle development the cells in the upper region of the somite form what?
The dermatome, and two muscle-firming areas are at the orders - dermomyotome
These cells also eventually make the muscles of the back, shoulder girdle, and intercostal muscles
What fuses to form single, multinucleated skeletal muscle cell that rapidly starts producing actin and myosin?
Myoblasts fuse
Fill in the blank.
__________ are the attachment point for muscles to bones and are derived from ___________ cells lying adjacent to myotomes.
Tendons
Sclerotome
(1 Word)
_______ is a subdomain that occupies the dorsal lateral portion of somite and comprises tendon progenitor cells. __________ is located between the neighboring sclerotome and myotome, at the future site of connection between bone and muscle and gives rise to the axial tendons of the body.
Syndetome
Myoblasts of the heart adhere to one another by special attachments that later develop into ____________ which are specialized junctions unique to cardiomyopathy that allow for rapid electric transmission
Intercalated discs
Cardiac muscle develops from what mesodermal?
Visceral/splanchnic lateral plate mesoderm
T or F
Myoblasts do not fuse
True
Some myoblasts become purkinje fibers
Only the sphincter and dilator muscles of the pupil and muscle tissue in the mammary and sweat glands are derived from __________
Ectoderm
What portions of the body originate from the visercal/splanchnic mesoderm?
Dorsal aroma large arteries, coronary arteries, gut and its derivatives.
Axial muscle development
The condensation of myotomal cells differentiates into what two subdivisions?
- Dorsomedial muscle cells = Epimere
- Ventral arterial muscle cells = Hypomere
Look at diagram Slide 95*
T or F
The sclerotomal and epithelial migrate?
True,
The epimere and hypomere portions of the somites undergo migration
___________ migrates to form the 4 layers of the Epaxial paravertebral muscles:
Forming the _________ Spinae Group (I Love Spines- Illiocostalis, Longissimus, Spinalis)
Epimere
Erector
___________ migrates to form the Hypaxial muscles:
Hypomere
*Diagram 97
What are the hypaxial muscles and what are the 4 layered lateral muscles?
How many total?
Subvertebral muscle
Supracostal (or outermost muscles)
- External muscles
- Middle muscles
- Internal muscles
Ventral wall muscle
SIX muscles on the ventral body wall total.
Diagram Slide 98*
What is Prune belly syndrome?
Partial or complete absence of abdominal musculature
What is Poland sequence?
The pectoral is minor and part of the pectoral is major muscles are missing on the patient’s left side
Name the arch/pouch that contributes to the development of the trigeminal nerve V3, mastoid air cells, and meckle’s cartilage
Arch/pouch 1
Name the arch/pouch 2 portions that contribute to the bronchial apparatus
Staples
Styloid
Stylodhyoid
Stapedius
Smiling (facial nerve)
Stapedial artery
Name the arch/pouch 3 portions that contribute to the bronchial apparatus
Stylopharynegeus
Glossopharyngeal nerve
Parathyroid glands
Internal carotid (problems if severed)
Common carotid (problems if severed)
Name the arch/pouch 4 portions that contribute to the bronchial apparatus
Everything from vagus
4 - superior laryngeal
6 - recurrent larygneal
