Module 3 Unit 2 Flashcards
What is the paraxial mesoderm? What are the series known as?
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
How many pairs of somites are there for each region?
42 - 44 pairs of somites:
4 occiput
8 cervical
12 thoracic
5 lumbar
5 sacrum
8-10 coccyx
What are the differentiated parts of somites?
Dermatomes, Myotomes, Sclerotome
What is a dermtome? How does it relate to a clinical diagnosis?
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.
What are myotomes? How are there important for diagnosing?
Groups of muscles innervates by the motor fibers of a single spinal nerve root.
Important for assessing motor function and diagnosing neuromuscular disease.
What are the sclerotome? How is it clinically relevant?
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
What does the paraxial mesoderm contribute to?
It contributes to the bones of the face and skull,and vertebrae and ribs.
What does the neural crest cells (NCC) contribute to?
It contributes to the bones of the face and skull.
What does the lateral plate mesoderm contribute to? What structures are the cells in the parietal mesoderm differentiated into?
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.
What are the two distinct processes involved in the formation of bones during embryonic and fetal development? What do they involve?
Intramembranous ossification - involves direct bone formation from mesenchymal tissue.
Endochondral ossification - the replacement of a cartilaginous template with bone tissue.
What is the intramembranous ossification process?
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
What are the bone directly differentiated to in the intramembranous ossification process?
Flat bones of the skull (parietal, frontal, occipital etc.), clavicle
What does the endochondral ossification give rise to?
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
What does the brachial (pharyngeal) apparatus shape into?
The head and neck anatomy in vertebrate embryos
What does the pharyngeal cross-section consist of?
Mesenchymal core derived from mesoderm and neural crest cells, and each is lined internally by endodermis and externally by ectoderm.
What does the first pharyngeal arch (Meckel’s cartilage) give rise to?
Gives rise to the maxilla, mandible, and muscles of mastication innervated by CN 5
What does the secondary arch give rise to?
Contribute to the formation of the hyoid bone and muscles of facial expression innervated by CN 7
What does the third and fourth arches give rise to?
thyroid gland
Thymus
Parathyroid glands
Components of the middle ear and neck
What does arch/pouch 1 consist of?
Muscles of Mastication
Meckel’s Cartilage
Maxilla
Meatus
Middle ear
Mastoid air cells
Maxiallary artery
Mylohyoid
trigeMinal nerve (CN 3)
What does arch/pouch 2 consist of?
Staples
Styloid
Stylohyoid
Stapedius
Smiling (fascia nerve)
Stapedial artery
What does arch/pouch 3 consist of?
StyloPHARYNGEUS, glossoPHARYNGEAL nerve, Parathyroid glands, internal Carotid (Problem if severed), Common Carotid (Problems of severed)
What does arch/pouch 4 + 6 consist of?
everything from Vagus
4 - superior laryngeal
6 - Recurrent laryngeal
Arytenoids, Cricoid, Corniculate, Thyroid, Superior Parathyroid, Ultimobrachial body, Parafollicular Cells
Pulmonary arteries + ductus arteriosus (left)
What is the Neurocranium?
Forms a protective case around the brain
What is the Viscerocranium?
Forms the skeleton of the face
What is the neurocranium derived from?
Membranous and Cartilaginous/ Chondrocranium
How is the Viscerocranium formed?
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
What are the fontanelles of the newborn skull? Where are they located? What order do they close in?
- Posterior fontanelle (back/ top of the head)- closes early @ 1 to 2 months
- Sphenoidal fontanelle (side of the head) - closes @ 6 months
- Mastoid fontanelle (back, bottom, side of the head) - closes in after sphenoidal and before anterior
- Anterior fontanelle (front/ top of head) - closes @ 18 months of age
What happens if the sagittal cranial sutures closes to fast?
Scaphocephaly - skull is long narrow shape with dominant frontal and occipital regions
What happens if the conornal cranial sutures closes to fast?
Brachycephaly - tall shape of skull