| Mesenchymal cell | These cells are derived from the connective tissues that form a population of stem cells with potential to differentiate for repair and replacement of connective tissue and other tissues |
| Sclerotome | -It is formed from cells near the notochord and neural tube, and will become the bone and cartilage of the region |
| Somite | Primitive segmental blocks of paraxial mesoderm adjacent to the notochord in the embryonic body, that undergo epithelization and develop a lumen |
| Dermatome | The early embryonic dorsal portion of the somite that will contribute the dermis and hypodermis of the skin. Note in the adult, this term is used to the skin sensory region innervated by a single spinal (nerve) segment. Development: mesoderm - paraxial mesoderm - somite - dermomyotome - dermatome - dermis |
| Dermatomyotome | -Early embryonic dorsolateral half of the somite that will later divide to form both the dermatome and myotome. The dermatome will contribute the dermis and hypodermis of the skin. The myotome will contribute the skeletal muscle of muscoloskeletal system.
-Development sequence: mesoderm to paraxial mesoderm to somite to "dermomyotome" then dermatome and myotome |
| Skeletal muscle | -have a long tubularstructure with a striated appearance (dark and light bands).
-They use a lot of energy and require fine control, thus each fiber will have several nuclei associated with it(multinucleated)
-Control is voluntary
-Location: Torso, limbs,face |
| Cardiac muscle | -Fibers:Striated and tubular but have a branched appearance
-Involuntary control
-Single nucleus in each cell segment of each muscle fiber
-Located only in the heart |
| Smooth muscle | -Nonstriated, uninucleated and spindle-shaped fibers
-Involuntary control
-occur inside the body in places where structures need to be
constricted or dilated to function. This includes the muscles that regulate the size of the pupil of the eye, constrict arteries when you are cold or dilate them when you have been running, and the muscles around the gut tube which enable it to pass contents all the way through |
| Lateral somitic frontier | Lateral border of the somite |
| Mesoderm | The middle layer of the 3 germ cell layers of the trilaminar embryo (ectoderm, mesoderm, endoderm). Each region of this early layer will later form different structures, this middle layer contributes all connective tissues of the body, except in the head region where neural crest also will contribute. Mesoderm outside the embryo and covering the amnion, yolk and chorion sacs is extraembryonic mesoderm. |
| Paraxial mesoderm-lateral to neural tube | In early development, the two lateral strips of mesoderm lying beside the axial mesoderm (notochord). This mesoderm at the body level will segment into somites, at the head level it remains unsegmented. |
| Axial mesoderm | -Alternative name for the notochord, an early embryonic structure lying in the midline of mesoderm within the early trilaminar embryo.
-is a type of mesoderm that lies along the central axis under the neural tube. will give rise to notochord starts as the notochordal process, whose formation finishes at day 20. |
| Somitomere | In the developing vertebrate embryo, one of the loose masses of paraxial mesoderm derived cells that form along each side of the neural tube towards the end of the third gestational week. |
| Epaxial skeletal muscle | -Describes skeletal muscles which lie dorsal (posterior) to the vertebral column developing from the somite myotome.
-In the head region 7 somitomeres of the domain form the muscles of the head
-In the trunk region it gives rise to muscles of the back, shoulder girdle and intercostals |
| Hypaxial skeletal muscles | The body muscles lying ventral (anterior) to the vertebral column are the hypaxial muscles. |
| What innervates the epaxial muscles? | Dorsal rami of spinal nerves |
| What innervates the hypaxial or abaxial muscles? | Ventral rami of the spinal nerves |
| Myofibril | very fine contractile fibres, groups of which extend in parallel columns along the length of striated muscle fibres. The myofibrils are made up of thick and thin myofilaments, which help give the muscle its striped appearance |
| Myoblast | The undifferentiated mononucleated muscle cells that will fuse together to form a multinucleated myotube, then mature into a muscle fibre. |
| Purkinje fibres | any of the specialized cardiac muscle fibers forming a network in the ventricular walls that conduct electric impulses responsible for the contractions of the ventricles. |
| Primaxial/epaxial mesodermal region | Domain of mesoderm derived from the paraxial domain,that remains around the neural tube after other cells migrate across the somite from frontier. Muscles of the back, shoulder girdles,intercostals as well as muscles of the head derive from this domain |
| Hypaxial/Abaxial mesodermal domain | This domain is formed from cells that have migrated from the somite across the frontier into the lateral plate mesoderm. Infrahyoid, ABD wall and limb muscles will develop from this domain |
